Structure–property–performance relationship of vanadium- and manganese-based metal–organic frameworks and their derivatives for energy storage and conversion applications

Abstract

Energy crises are currently the main challenges for human life. Promising solutions are expected from research on novel materials with a wide range of functional benefits. The new family of materials, known as metal–organic frameworks (MOFs), with coordination bonds between a metal and organic matter as the center atom and ligand, respectively, are an exciting class of such functional materials. MOFs represent inorganic–organic hybrids of crystals, making them beneficial for different applications. In the past few years, several attempts have been made to modify pristine MOFs and achieve better characteristics, including a larger surface area, greater availability of active sites, highly stable materials, and improved transport and diffusion of mass. The present review summarizes MOFs containing vanadium and manganese, including multi-metallic materials, composites, and derivatives. It focuses on the structure, porosity, and stability and their impact on energy storage and conversion applications. Each MOF type containing vanadium and manganese is examined to highlight the association of porous structures and characteristics. This review will further provide a deep understanding and transparent insights into the functions of MOFs and their suitability for certain applications. Other interested researchers are recommended to examine material optimization and synthesis of various vanadium and manganese-based MOFs that are more stable while also showing higher capacity. Vanadium and manganese-MOFs have many different oxidation states that are useful for energy-related applications, and their comprehensive review in comparison with other first row transition metals has not been carried out yet.

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Reza Abazari

Dr Reza Abazari obtained his MSc in Inorganic Chemistry from K. N. Toosi University of Technology (Iran) in 2012 and his PhD from Tarbiat Modares University in 2019. Currently, he is working as a Youth Research Professor at University of Maragheh, Iran. His research interests include the design and synthesis of nanostructured materials based on crystalline porous frameworks for electrochemical energy storage and photocatalytic applications.

Soheila Sanati

Dr Soheila Sanati obtained her PhD in Inorganic Chemistry at Azarbaijan Shahid Madani University (Iran) in February 2019. Her research interests mainly focus on the design, synthesis, and applications of layered double hydroxides and metal–organic framework-based nanostructured materials for energy storage and conversion, irradiation thermal treatment, renewable clean energy and environmental protection applications.

Deepak P. Dubal

Prof. Deepak Dubal is currently working as Full Professor at Queensland University of Technology (QUT), Australia. He is a productive, well-cited, and multiplefellowship-winning scientist. His achievements are honoured by several prestigious fellowships such as Brain Korea-21 (South Korea-2011), Alexander von Humboldt (Germany-2012), Marie Curie (Spain-2014), and Australian Future Fellowship (Australia-2018). His research expertise lies in the design and development of multifunctional materials for clean energy conversion and storage technologies with a special focus on supercapacitors, lithium-ion batteries, Li-ion capacitors, and electrochemical flow cells. In addition, his team is extending its research area in biomass valorisation and battery recycling, aiding circular economy and sustainable practices.

Min Liu

Prof. Min Liu received his PhD (2010) from Chinese Academy of Sciences. In 2010–2015, he joined the University of Tokyo as a research fellow with Prof. Kazuhito Hashimoto and Prof. Kazunari Domen, separately. In 2015–2017, he joined the University of Toronto as a postdoctoral fellow with Prof. Edward Sargent. Since 2017, he has been working as a professor at Central South University. He has published more than 200 papers with over 21,000 citations (h-index 69). His research focuses on electrocatalytic energy conversion, photo-electrocatalytic CO2 reduction and the resource utilization of perfluorocarbons.

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1. Introduction

Over the past five decades, world energy consumption has been increasing owing to population growth, urbanization, and the enhancement of living standards, imposing considerable environmental burdens. As a consequence, the development of green and renewable energy sources is becoming increasingly necessary. Recently, many works have been performed to develop energy storage and conversion technologies such as supercapacitors, batteries and water splitting.^1–4 To achieve high performance in these technologies, the designing of efficient electrode materials with high power and energy densities is urgent.^5,6 Different materials can be developed to realize such advanced applications in this regard.

Recently, numerous attempts have been made to design and synthesize novel metal–organic frameworks (MOFs) and investigate their physical and chemical characteristics. Additionally, much attention has been focused on MOFs created through connecting metal nodes with organic bridging ligands using strong bonds to produce crystalline frameworks (Fig. 1). MOFs have several attractive characteristics such as structural tailorability, high porosity, low density, desired chemical functionalities, ordered crystalline structures, and open metal sites, which make them promising for various applications such as membranes, optoelectronics, gas storage, photo(electro)catalysis, energy storage, fluorescent sensors, molecular separation, fuel cells, imaging, and biomedicine.^7–13 Reports have confirmed the existence or development of more than 30 000 MOFs owing to a wide range of metal ions, organic linkers, and their various combinations, which are abundant, intriguing, designable, and adaptable.^14–17 Unlike conventional catalysts, whose performance is restricted by their low porosity and inflexible design, MOFs facilitate the precise control of the structure and open metal sites while providing large specific surface areas.^18,19

Fig. 1 Various design and structural engineering modes in ligands and metal ions in MOFs.

In comparison with other common porous materials such as mesoporous silica and zeolites, MOFs have advantages such as tuneable topologies and pore sizes, porous structures, multi-functionality, well-defined structures and uniform dispersion of components that enable them for energy-related applications. These advantages make easy electron transfers and ion diffusions during electrochemical reactions. Despite their advantages, MOFs have some disadvantages in comparison to some common materials. These materials have poor conductivity and low specific capacitance that limit their usage for energy-related applications. Some of the MOFs just have a microporous structure that this is not suitable for the entry of macromolecules.²⁰

Various MOFs have been fabricated using divalent or trivalent 3p metal ions, 3d transition metals, and lanthanides, while there are still challenges in synthesizing MOFs from high-valent metal ions.^21,22 The synthesis of MOFs with covalent bonds between metal ions contributing as nodes and organic ligands as spokes combined to produce open framework configurations was conducted by Furukawa et al.,²³ who discussed the developments in the construction of higher-order mesoscopic superstructures containing nanocrystals.²⁴ Two examples of transition metals are vanadium and manganese, belonging to the 3d subfamily and having an electron configuration of 3d³ 4s² and 3d⁵ 4s², respectively. The five and seven valence electrons at the surface layer can produce a perfect pseudo-capacitance and different redox potential pairs.^25,26 The low cost, eco-friendliness, and different coordination numbers established in situ have given manganese, a transition metal ion, the required advantages for application in electrode material. Although vanadium and manganese-containing electrode materials have been successfully and extensively used in industries, single-component vanadium and manganese electrode materials cannot deal with different requirements, including activity and stability in various applications associated with energy. Multi-metallic electrode materials can enhance performance through their electronic and chemical characteristics, distinguishing them from their parent metals' properties.^27,28

Although significant attention has been paid to MOFs derived from divalent metals (Ni²⁺, Zn²⁺, Cu²⁺),^29–31 less research has focused on tri-, penta-, and heptavalent metals in MOFs, with even more scant reports on MOFs based on vanadium and manganese. The lack of research in this area is surprising, given the possibility of forming diverse clusters and complexes with vanadium nodes. Available evidence shows that MOFs based on these two chemical elements are highly porous. They can promote the effective transfer of electrons to address the requirements to storage and conversion.^32–38 The first porous MOF formed based on vanadium is called MIL-47,³⁹ which has attracted much attention in relevant literature due to its great specific surface area (S_Langmuir = 1320 m² g⁻¹), considerable thermal stability (400 °C) in the atmosphere, and significant catalytic effects in oxidation reactions.

Nevertheless, the direct application of MOFs as electrode materials is considerably limited due to their low electrical conductivity, excellent crystal size, and low structural stability.^40–42 Porous materials can interact with different ions, atoms, and molecules via their surfaces and bulk, leading to their unique properties compared to other materials.^43,44 The easy post-synthesis surface functionalization of organic moieties provided a great chance to design organic–inorganic hybrids with a high porosity used in various energy applications.^45,46 On the other hand, it is possible to transform MOFs into their derivatives, which possess significant electro-catalytic activities, mainly found in bimetallic MOFs.⁴⁷ The optimal structural stability of MOFs for various energy applications can be achieved by modifying their pathways as single MOFs, composites, and derivatives (Fig. 2).⁴⁸

Fig. 2 Schematic representation of MOFs and MOF-composites and derivatives together with their transformations. Adapted with permission from ref. 48. Copyright 2017 Elsevier.

Thus, the mentioned MOF derivatives and composites are highly porous and have a great surface area, leading to their desirable catalytic activity and making them more stable than their pristine counterparts or different emerging compounds. Although there have been several studies on M-MOFs and their composites (M = Zr, Ti, Zn, Ni, Fe, Co, Ni, and so on) with the production and storage of energy,^49–52 as far as the authors know, no studies have recently investigated vanadium and manganese-based MOFs or their composites to provide a more comprehensive review of the applications of these two MOFs in the field of energy. Accordingly, the current study has summarized the data on the development of these MOFs concerning their structural, chemical, and physical characteristics, their role in energy applications. The current study also discusses energy applications of the mentioned MOFs; supercapacitors, batteries and water splitting, along with the potential future advancements in these fields, are hoped to result in beneficial information for other researchers and play a role in filling the gap in current research.

2. Structures and characteristics of MOFs

Overall, hierarchically porous materials can be practically used to harvest light, transport electrons and ions, and perform mass loading and diffusion due to their high porosity, great surface area, highly accessible space, low density, various chemical compositions, and interconnection of hierarchically porous structure at a wide range of length scales, making them technologically important.^53,54 Secondary building units (metal ions or clusters) and organic linkers form the MOF's structure. Various combinations of these components create enormous number of MOFs.^55,56 Many of the mentioned characteristics are shown by MOFs because of their considerable porosity and hierarchical structure,⁵⁷ set up through connections between organic linkers and metal ion clusters/metal ions. Besides, the secondary building units, known as SBUs, represent another important concept related to MOFs' unique design and characteristics.⁵⁸ Some regularities have been revealed from framework formation that predicts the MOF's properties. The most important characterization methods of MOFs include the Brunauer–Emmett–Teller method to determine the specific surface area of MOFs, X-ray diffraction for analysis of their structure, and thermogravimetric analysis (TGA) for studying the thermal stability of MOFs.

Energy is required to disconnect or form bonds and carry out MOF synthesis, through which the organic linkers and metal oxides are bound.⁵⁹ MOFs are mainly synthesized to produce the required inorganic building blocks while avoiding the decomposition of organic linkers. Different appliances, including ovens, microwaves, or electromagnetic wave radiation, produce adjustable amounts of energy and synthesize MOFs. The properties of the resulting MOFs will depend on the source type, the type of energy produced, and the synthesis method. The main characteristics of MOFs containing exact inorganic building blocks, including particle size, morphology, and distribution, determine their feasibility and accessibility. It can also be said that the porous structure of these MOFs depends on the type of heat energy generated throughout the reaction and the utilized heat source.^60–62 The synthesis of MOFs by coordinated metal clusters and organic ligands may seem straightforward; obtaining the optimum structure can be challenging. The type of MOF produced depends heavily on compositional and process parameters, the first of which includes the concentration of metal ions, pH, linker substituents, and solvents. In contrast, the second comprises temperature, time, and pressure.^63,64 Current research on various catalysis processes associated with energy generation has focused on such compounds because they are highly porous and possess large surface areas and common starting materials, particularly for their ligands. Despite using similar reactive mixtures (organic ligands, metal sources, and solvents) throughout MOF production, structural differences are associated with the size of particles, reaction time, yield, and morphology.^65,66 Thus, developing various methods to synthesize MOFs seems of critical importance. Among the synthesis techniques, some seem appropriate for application at a large scale. Fig. 3 shows some methods used to synthesize MOFs.⁶⁷

Fig. 3 Different synthesis techniques for MOFs. Adapted with permission from ref. 67. Copyright 2022, the Royal Society of Chemistry.

MOFs provide considerably large surface areas, consistent adjustable pore sizes, and significant pore volumes. At the same time, they can also perform various tasks as their metal nodes and ligands are easily modified,⁶⁸ making them suitable candidates as catalysts and electrode materials.^69–71 MOFs have evenly distributed catalytic sites, large surface areas, open channels for substrate diffusion to access the active sites, and highly recyclable structures (Fig. 4). Unique configurations, adjustable pores, and surface performance of MOFs can be designed by self-assembly and post-synthesis modifications, leading to better performance than conventional materials.^72–74 Accordingly, the successful modulation of different organic and inorganic catalytic elements has been carried out in active MOF-localized sites.⁷⁵ However, MOFs can only be functionalized with efficient and localized catalytically active components while controlling the conditions and considering clear-cut assumptions.⁷⁶ The synthesis and characterization processes for the intercalation of localized catalytic sites throughout MOF lattices are also examined in addition to the discussions on the general concepts and the essential contribution of catalytic elements for producing novel compounds. More attention is paid to the techniques utilized for catalytic site immobilization in the MOF's particular structural components, while the structural preservation of the latter is favored.^77–79

Fig. 4 Different catalytically active sites of MOFs (bimetallics and composites).

Overall, MOF synthesis leads to the fabrication of MOF crystals with adaptable sizes, configurations, and compositions by incorporating certain metal ions and organic ligands.⁸⁰ The MOF precursors can then be modified through post-synthetic modifications leading to the generation of their derivatives with various nanostructures and compositions.⁸¹ Studies have reported different synthesis techniques such as solvothermal, diffusion, microwave, sonochemical, and electrochemical synthesis^82–91 and discussed the strengths and drawbacks of each.⁹² The purification of MOFs is through its treatment with a solvent at high temperature. Pore emptying is needed for the activation of a MOF that is difficult since the collapse of the framework may take place by removing inclusions from the MOF structure, especially if the framework and the guest molecules have a strong bond. For instance, purification is a vital process for the catalytic performance of MOFs since by-products can affect the catalytic behaviour. According to Fig. 5, different nanostructures are currently achievable, including microporous, composites, core–shell, layer structures, and 2D materials.^82,93 Microstructuring is an efficient method to modulate the physical and chemical properties of inorganic functional materials.⁹² The potential of synthesis processes for MOF-derived materials to tune the composition and design of material structures has already been highlighted, confirming improvements in the catalytic performance.⁹³ For instance, the catalytic activity of MOF-derived materials can be modulated and increased by incorporating several components and adjustable chemical composition. As mentioned earlier, the significant surface area and highly porous structure of MOF-derived nanomaterials provide a considerably active surface, facilitate mass transfer and charging, and guarantee efficient strain accommodation throughout catalysis.^92,94–96 MOFs are also fascinating precursors for transformation to various classes of porous derivatives, which are easily tunable and possess good dispersion of active sites. Consequently, it is easy to alter the pore shapes, sizes, and characteristics in MOFs using various methods, resulting in novel characteristics and more effectiveness.

Fig. 5 Schematic view of MOF-derived nanomaterials: (a) structures derived from MOFs, (b) micro/nanocomposites derived from MOFs. Adapted with permission from ref. 93. Copyright 2019, the Royal Society of Chemistry.

The stability of MOFs is one of the main concerns for various applications that mainly include chemical, mechanical and thermal stability. Totally, the MOF's stability arises from different factors like the kinetic and thermodynamic factors of the environment.^97,98 The resistance of MOFs in different environments such as aqueous solutions, solvents and moisture determine their chemical stability. The strength of metal–ligand coordination bond determines the thermodynamic stability. For example, linkers with low pK_a will bind with high valence metal ions to make a stable structure.⁹⁹ Also, metal clusters make MOFs with excellent stability. MIL-101 MOFs with chromium acetate cluster exhibit a great stability in aqueous solutions.¹⁰⁰ Rigid building blocks create rigid and dense frameworks with high stability. In addition, the hydrophobicity of the surface due to the prevention of water condensation around the clusters or water adsorption in the pores increases the stability of MOFs in aqueous solutions. However, introducing various functional groups on MOFs with high stability will be very successful.

3. Energy conversion and storage

3.1. Electrochemical water splitting

The overconsumption of fossil fuels has led to global warming and air pollution.^101,102 Therefore, attempts to replace fossil fuels with renewable and clean energy sources have become an urgent global need.¹⁰³ Hydrogen can be a promising fuel source to meet future energy demand. Electrochemical water splitting is a promising approach for hydrogen generation, which occurs under mild conditions using electricity.^104–107 This method includes two half-reactions of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) occurring in the cathode and anode, respectively (Fig. 6a). As depicted in Fig. 6b, a water electrolyzer comprises three sections: anode, cathode, and electrolyte. Although this method is an effective approach to produce high-purity hydrogen, the practical use of this method for the mass production of hydrogen is limited due to the requirement of high overpotentials in the electrocatalysts. These limitations can be overcome by developing efficient electrocatalysts with low overpotentials.^108,109

Fig. 6 (a) OER and HER polarization curves and corresponding half reactions, and (b) schematic illustration of H₂ and O₂ generation from water.

Pt-based materials are currently used for HER electrocatalysis, while Ru- and Ir-based oxides are employed as the OER electrocatalyst.¹¹⁰ The application of these materials is also faced with several limitations, such as their scarcity and high costs. These high-cost electrocatalysts can be replaced by electrocatalysts based on non-precious metals.¹¹¹ MOFs are porous materials with organic likers and metal clusters. Thanks to their large surface area and tunable porosity, these materials could be ideal candidates for developing water-splitting electrocatalysts. Their accessible surface area and porosity can decrease the distance of charge carriers and reactants during the electrocatalytic reactions, leading to improved performance.¹¹² The other important factor in improving the electrocatalytic performance of the MOFs in water splitting is the interfacial electronic coupling interactions due to the accessibility of metal–ligand junctions in MOFs.¹¹³ The use of DFT (density functional theory) calculations seems to facilitate the prediction of the electronic structure of these MOFs and their derivatives, as a result of which more ideal surfaces can be designed for electrochemical reactions.^114–119

Vanadium (V) is a transition metal with 5 electrons in its outer electron layer, offering various redox behaviors.¹²⁰ Therefore, V-based materials have extensive applications in electrochemical storage and energy conversion.^121–123 V-MOFs have shown high electrocatalytic performance and cycle stability due to their multiple valence states and open framework structure.¹²⁴ The use of V-MOFs as a precursor for the design and fabrication of various V-based electrode materials is also promising as these materials can inherit some of the unique features of MOFs, like their high surface area and porosity, which can accelerate the diffusion of ions in the electrocatalytic reactions, thus improving the electrocatalytic performance.¹²⁵ Manganese (Mn) is also a transition metal that offers different redox behavior. Concerning Mn-based MOFs, Mn³⁺ is believed to play a decisive role in OER performance. Mn³⁺ with high spin configuration has Jahn–Teller distortion in which longer Mn–O bonds can facilitate O–O formation, enhancing the performance of the OER electrocatalyst.^126,127 On the other hand, the low toxicity and abundance of Mn are among the advantages of Mn-based water-splitting electrocatalysts.¹²⁸ The binding energy is optimized for oxygen intermediates in the Mn-containing electrocatalysts, which can enhance the performance of OER electrocatalysts.

Studies on recent electrocatalysts have shown that the electrocatalytic performance can be significantly improved by incorporating the second metal of a similar electronic configuration.¹²⁹ Concerning MOFs, numerous reports have addressed multi-metallic electrocatalysts.¹³⁰ The multimetallic electrocatalysts are believed to present a synergistic effect between multi-element metals, which can affect the performance of the electrocatalyst.¹³¹ In this regard, designing an optimal electrocatalyst structure with better composition can positively affect its efficiency. In 2021, Han et al. developed VFe-MOF with controllable stoichiometry on Ni foam (VFe-MOF@NF) as a bifunctional electrocatalyst for OER and HER.¹³² In 1 M KOH (pH = 14) as electrolyte solution, the VFe-MOF@NF electrocatalyst needs 246 mV and 147 mV overpotentials to reach 10 mA cm⁻² current density for OER and HER, respectively. The superior performance of this electrocatalyst can be assigned to the electronic regulation and morphological control of bimetals (Fig. 7a). Array structure leads to the accessibility of the active sites on the electrode surface, accelerating the diffusion of ions in the electrocatalytic reactions.¹³³ On the other hand, as depicted in Fig. 7b, there is a synergistic effect between Fe and V metals, which guarantees the superior performance of this electrocatalyst.

Fig. 7 (a) The formation of VFe-MOFs@NF, (b) synergistic effect between V and Fe in VFe-MOF@NF. Adapted with permission from ref. 132. Copyright 2021, Elsevier.

Vanadium possesses different valence states. It could be a dopant to improve the electrocatalytic performance due to its high earth abundance and high electrocatalytic performance.^134–136 The presence of vanadium in the electrocatalysts can optimize the intermediate binding energy during the redox processes and improve the electrical conductivity, hence affecting the decline of the overpotential. On the other hand, vanadium offers a synergistic effect between different metals and will effectively improve the electrocatalyst's performance.¹³⁷ Kong et al. examined M₂V-MOFs in OER and HER.¹³⁸ Their results showed that Fe₂V-MOF had the lowest overpotential for OER and HER. The performance of Fe₂V-MOF for HER and OER was examined in 0.1 M KOH (pH = 12) and 1 M KOH (pH = 14) as electrolyte solutions. This electrocatalyst for OER and HER needs 314 mV and 195 mV overpotential at 10 mA cm⁻² current density in 1 M KOH, respectively. For OER and HER in 0.1 M KOH electrolyte, this electrocatalyst needs 363 mV and 255 mV overpotential to reach 10 mA cm⁻² current density, respectively. In this regard, in another report by Lv et al. on Ni₂V-MOF, Ni₂V-MOFs@NF was used as electrocatalysts for OER and HER.¹³⁹ The electrochemical tests were carried out in 1 M KOH (pH = 14). The synergistic effect between Ni and V, as well as 2D ultrathin self-assembled nanosheet morphology, improved the performance of this electrocatalyst (Fig. 8a(i)). As shown in Fig. 8a(ii), electron transfer occurs between Ni and V, where Ni acts as a donor while V serves as an electron acceptor. In contrast, the incorporation of high valent V was observed to lower the E_g of Ni₂V-MOFs, improving the proton adsorption properties for HER. Their results described the self-aggregation of a 2D ultrathin nanosheet Ni₂V MOF in a 3-dimensional nanoflower Ni₂V-MOF@NF composite, in which HER and OER needed the merely respective overpotentials of 89 and 244 mV (Fig. 8a(iii)). Even though 10 mA cm⁻² Ni₂V-MOFs@NF exhibited a higher overpotential than Pt/C@NF (20 mV), it still performed better than other samples. The Tafel slope of Ni₂V-MOFs@NF (98.3 mV dec⁻¹) is lower than that of other catalysts, except for Pt/C@NF (71.9 mV dec⁻¹). Moreover, achieving the overall water splitting at 1.55 V and 10 mA cm⁻² current density was possible. In addition, multiple tests revealed that Ni₂V-MOFs@NF possessed long-time stability for OER and HER reactions. DFT could justify vanadium selection as a second metal, highlighting the BMOF E_g reduction and the electronic transport promotion due to vanadium addition at a high oxidation state, which subsequently improves the electronic conductivity.

Fig. 8 (a) (i) Growing NiV-MOFs on the Ni foam by the ultrasound/solvothermal route for overall water splitting, (ii) electronic coupling between the Ni, V and O elements, (iii) the photograph of the electronic cell. Adapted with permission from ref. 139. Copyright 2020, The American Chemical Society. (b) (i) The synthesis protocol of V_0.09-Ni_0.91MOF/NF, (ii) total water splitting LSV curves of V_0.09-Ni_0.91MOF/NF. Adapted with permission from ref. 142. Copyright 2022, Wiley-VCH.

In recent years, doping has become one of the most effective methods to improve MOFs' stability and intrinsic OER performance, which can modify the surface electrical structure of MOFs.¹⁴⁰ In this regard, vanadium is an effective dopant for improving the electrocatalytic performance of water oxidation. Thanks to its valence states, V can tune the electronic structure and provide a synergistic effect between the host metal and dopant to improve the electrocatalyst performance for OER. V-doped catalysts have many free carriers around the Fermi level due to the doping of vanadium, which improves charge transfer in the catalyst, leading to better electrocatalyst performance.¹⁴¹ Regarding the importance of vanadium doping in the structure of MOFs, Yu et al. succeeded in synthesizing V_1−xNi_xMOF by a solvothermal method in 2022. They used it to study OER performance (Fig. 8b(i)).¹⁴² Their findings suggested that V doping accelerated the charge transfer in Ni-MOF with an OER overpotential of 235 mV at 10 mA cm⁻² current density in 1 M KOH (pH = 14). This electrocatalyst's unique 3D self-supported structure provides more active sites, leading to a synergistic effect between active sites during water splitting. This electrocatalyst has exhibited good behavior (1.93 V) in the electrolyzer system at high current density (Fig. 8b(ii)).

On the other hand, heteroatom doping in catalysts reduces the Gibbs free energy in addition to adjusting the electronic structure of catalysts, improving their conductivity. As mentioned, vanadium is a proper choice in this regard. ZIFs could be ideal precursors for preparing heteroatom-doped porous carbon skeletons.¹⁴³ In this context, Guo et al. prepared V-Co_xP@NC NPs for water-splitting applications (Fig. 9a) in 1 M KOH (pH = 14).¹⁴⁴ The advantages offered by this electrocatalyst for a good performance of water splitting in an alkaline electrolyte include its regulated electronic structure due to V doping and the presence of the CoP and Co₂P mixing phase, which is due to the interaction between these mixture phases and V doping, leading to lattice distortion and improved performance of the electrocatalyst. This electrocatalyst exhibited improved stability and conductivity due to the ZIF-derived N-doped carbon shell, resulting in ideal electrocatalytic performance (Fig. 9b–d).

Fig. 9 (a) Schematic presentation of V-Co_xP@NC NPs, (b) electrocatalytic HER activities, (c) electrocatalytic OER activities, and (d) LSV curves (inset: two-electrode electrolytic system). Adapted with permission from ref. 144. Copyright 2020, Elsevier.

Ni₃S₂ has been considered an electrocatalyst due to its simple preparation and high chemical stability.¹⁴⁵ The pure form of this material has not shown significant performance, motivating researchers to design Ni₃S₂-based materials for water-splitting purposes. One of these important ideas is the doping of elements capable of effective improvement in the activity of active sites. In this regard, thanks to their unique characteristics, MOFs can be an attractive strategy to increase and improve the performance of electrocatalysts for water splitting in combination with metal doping. Dong et al. reported MOF-V-Ni₃S₂/NF electrocatalyst using a self-templating method.¹⁴⁶ In 1 M KOH (pH = 14) as electrolyte solution, this electrocatalyst needs 118 and 268 mV overpotentials at 10 mA cm⁻² current density for HER and OER, respectively. They claimed that V-doping and MOF-derived 3D hieratic nanostructure played an effective role in the electrocatalyst performance for water splitting by providing high surface area and numerous active sites.

By understanding the requirements of electrocatalysts, the efficient design of materials can lead to the design of platform composites. In this regard, designing modular bottom-up materials in which polyoxometalates are incorporated into the structure of MOFs¹⁴⁷ could be attractive due to the chemical and redox tenability and the presence of MOFs with suitable pores for the uptake of polyoxometalates. These items can strengthen conductivity in the presence of organic ligands.¹⁴⁸ Polyoxovanadates with high redox activity and high energy density are ideal candidates in this field.¹⁴⁹ In a study by Ji's group, the CoVO/C composite was developed for OER using ZIF-67 precursor (Fig. 10a).¹⁵⁰ This composite showed good OER performance with 350 mV overpotential at 10 mA cm⁻² current density and high stability in 1 M KOH (pH = 14) (Fig. 10b and c).

Fig. 10 (a) Process fabrication of the CoVO/C composite. (b) LSV curves and (c) stability test of the CoVO/C composite after 1000 CV cycles. Adapted with permission from ref. 150. Copyright 2019, the Royal Society of Chemistry.

One of the effective strategies to overcome the limitations of MOFs in electrocatalytic applications is the preparation of 3D electrodes in which pristine MOFs are directly deposited on a conductive substrate such as Ni foam, carbon cloth, and Cu foil.¹⁵¹ The advantage of these 3D porous metallic materials, which play the role of the support surface in electrode materials, is their open-pore hierarchical structure with a high specific surface area, which can elevate the conductivity while reducing the ion diffusion length during electrochemical reactions, providing better electrocatalytic performance. These reasons allowed Goswami et al. to explore the binder-free Mn-MOF/NF electrode in 2022 for water-splitting purposes.¹⁵² The coexistence of mixed metals in the structure of MOFs provides another opportunity to adjust their properties and multifunctionality, further reinforcing their use as electrocatalysts.¹⁵³ This electrocatalyst in 0.1 M KOH (pH = 12) needs to 280 and 125 mV overpotentials to reach 10 mA cm⁻² for OER and HER, respectively. Studies on the electrocatalytic performance of MOFs confirm that the use of mixed metals improved their local electronic structures and the presence of synergistic effects,¹⁵⁴ reflecting the superiority of mixed metallic MOFs compared to their single metallic counterparts. Mn is a dopant in electrocatalysts to adjust their electronic structure.¹⁵⁵ In a study by Zhang et al., FeCoMnNi-MOF-74/NF was prepared by the hydrothermal method.¹⁵⁶ In this work, 1 M KOH (pH = 14) was used as an electrolyte solution. They observed a multilevel and hollow nanostructure for this MOF (Fig. 11a(i)). The investigation of this electrocatalyst's HER and OER performance showed its high stability and conductivity. The reason could be its multilevel and hollow structure, which improves the interaction between active sites and electrolytes during electrochemical reactions, which improves the electron transfer (Fig. 11a(ii and iii)). The performance of MOF electrocatalysts can be improved through various approaches, including the modification of intrinsic activities, enhancing the number of active sites, and designing self-supporting electrodes.^157,158 Zhou et al. prepared well-ordered trimetallic Mn_xFe_yNi-MOF-74 film (x = the molar ratio of Mn : Ni, y = the molar ratio of Fe : Ni) through a solvothermal method and used it as a self-supporting electrode material for water splitting applications (Fig. 11b(i)).¹⁵⁹ Their investigation indicated that Mn_0.52Fe_0.71Ni-MOF-74 was an optimized electrode for overall water splitting with an overpotential of 462 mV at a current density of 100 mA cm⁻² in 1 M KOH (pH = 14). The incorporation of Mn in the MOF structure regulated the morphology of MOF-74. It led to the formation of several Fe(II)–OFe(III) motifs through the adjustment of the electronic structure, which resulted in the higher stability and accessibility of high valent active sites, hence increasing the electrocatalyst performance (Fig. 11b(ii and iii)).

Fig. 11 (a) (i) Synthesis protocol of FeCoNiMn-MOF-74/NF, (ii) samples Nyquist plots of OER, and (iii) stability test of FeCoNiMn-MOF for 30 hours. Adapted with permission from ref. 156. Copyright 2020, the American Chemical Society. (b) (i) In situ formation of Mn_0.52Fe_0.71Ni-MOF-74 on NF, (ii) schematic illustration of overall water splitting inelectrocatalyst, and (iii) LSV curve of Mn_0.52Fe_0.71Ni-MOF-74 in overall water splitting. Adapted with permission from ref. 159. Copyright 2020, Wiley-VCH.

Hydroxide ligands, coordinatively unsaturated metals, and the effect of multimetallic coupling can dramatically enhance the OER electrocatalytic performance.¹⁶⁰ Li et al. assessed the OER performance of Fe/Ni/Co(Mn)-MIL-53 (Fig. 12a(i)).¹⁶¹ The optimal Fe/Ni_2.4/Mn_0.4-MIL-53 exhibited an OER overpotential of 236 mV at a current density of 20 mA cm⁻² in 1 M KOH (pH = 14). Such a high performance can be assigned to the synergistic effect of porosity and active sites as well as the unique structure of the electrode material (Fig. 12a(ii and iii)). In another work, FeMn bimetallic MOF was utilized for HER and OER (Fig. 12b(i)). In this study, FeMn-MOF/NF(1 : 1) nanoflowers showed the highest electrochemical specific surface area.¹⁶² OER and HER overpotentials in 1 M KOH (pH = 14) solution at a current density of 50 mA cm⁻² were 290 mV and 260 mV, respectively. The presence of Fe and Mn in the structure of this electrocatalyst led to a synergistic effect that enhanced the active sites. These advantages finally improved the HER and OER performance of the electrocatalyst (Fig. 12b(ii and iii)).

Fig. 12 (a) (i) Fabrication process of Fe/Ni/Co(Mn)-MIL-53/NF, (ii) LSV curves and (iii) Tafel plots of samples. Adapted with permission from ref. 161. Copyright 2018, Wiley-VCH. (b) (i) Fabrication process of FeMn-MOF/NF, (ii) LSV curves of OER and (iii) LSV curves of the HER. Adapted with permission from ref. 162. Copyright 2018, Elsevier.

Theoretical studies have shown a relationship between ferromagnetic and antiferromagnetic with bonding and antibonding orbitals interaction between organic ligands and magnetic ions. Moreover, some reports have expressed that the OEP performance of magnetic electrocatalysts highly depends on their exchange interaction and spin configuration.¹⁶³ This knowledge motivated researchers to discover a method to guide the distribution of the catalyst spin, which can be advancement with a deeper understanding of the OER performance. In this regard, Zhou et al. employed the magnetic stimulation method to prepare CoMn-MOF for OER purposes.¹⁶⁴ When metal atoms are placed on the surface as a reaction site, they can accept lone-pair electrons due to their unpaired 3d orbitals, incrementing the electrocatalytic performance (Fig. 13a–c). In the presence of Mn and Co and their unpaired electrons, the 3d shell served as a spin-dependent and regulated carrier transfer and orbital reaction during the catalytic reactions. Moreover, the effect of magnetic heating contribution on the OER performance of the Co_0.8Mn_0.2-MOF catalyst was assessed. The role of spin reconfiguration is highlighted in Fig. 13d, indicating the OER process of Co_0.8Mn_0.2-MOF, considering high- and low-spin configurations.

Fig. 13 (a) 3d orbital electron configuration, (b) magnetic exchange sketch, (c) the interaction between Co and *OH orbital under different spin configurations, and (d) the OER process of Co_0.8Mn_0.2-MOF with high spin and low spin configurations. Adapted with permission from ref. 164. Copyright 2021, Nature.

Charge transfer is accelerated due to metal–sulfur bonds in transition metal sulfides. On the other hand, electron tunneling and an abundance of active sites can improve the catalytic performance of the transition metal sulfides.¹⁶⁵ However, their charge transfer and electrocatalytic performance may be limited due to possible metal center coverage. In this regard, structurally-controlled engineering could be useful. Manganese sulfide-based electrocatalysts have succeeded in regulating the electronic structure, leading to high conductivity.¹⁶⁶

Moreover, the interactions between cobalt sulfide electrocatalysts and other transition metal sulfides can decrease the adsorption free energy.¹⁶⁷ These findings motivated Zhang et al. (2021) to employ the MIL-88B(Co/Mn)-NH₂ precursor for developing semi-crystal MILN-based Co₃S₄/MnS₂ for overall water splitting.¹⁶⁸ In the mentioned electrocatalyst, S-doped carbon acted as a bridge and conducted electron transfer between MnS₂ and Co₃S₄. Moreover, the dispersion of active sites through the metal centers dispersion enhanced the performance of the electrocatalyst. The dual synergistic effect due to NH₂– and S²⁻ electron-donating and the ability to change valence in metal centers have also greatly increased the overall water-splitting performance. In another study, Chen et al. reported Mn-Co9S8/NC using ZIF precursor to study the OER performance (Fig. 14a(i)).¹⁶⁹ They argued that Co₉S₈ enhanced the conductivity. Interestingly, the graphitization of the carbon skeleton was increased after Mn introduction, which contributed to the regulation of the electronic structure of Co. These factors can explain the proper performance of this electrocatalyst for OER (Fig. 14a(ii and iii)). Qi et al. reported an efficient OER electrocatalyst with Mn and S-dual doping on Co₃O₄-derived MOF (Mn-Co₃O₄/S) (Fig. 14b(i–iii)).¹⁷⁰ Their results indicated that Mn doping modified the Co electronic structure and improved the performance of active sites in Co₃O₄. In contrast, S doping enhanced the sites for the adsorption of protons and provided high conductivity for the electrocatalyst. This dual doping increased the Co³⁺ proportions and facilitated the OER's four-electron transfer. This electrocatalyst needs 330 mV overpotential at 10 mA cm⁻² current density in 1 M KOH (pH = 14) as an electrolyte solution.

Fig. 14 (a) (i) The synthesis process of Mn-Co₉S₈/NC, (ii) LSV curves and (iii) EIS curves of the samples. Adapted with permission from ref. 169. Copyright 2021 Elsevier. (b) (i) Fabrication process of Mn-Co₃O₄/S, (ii) LSV curves and (iii) EIS curves of samples. Adapted with permission from ref. 170. Copyright 2019 Elsevier.

Carbon-decorated metal oxides derived from ZIFs are one of the suitable approaches for preparing OER electrocatalysts. ZIF-derived materials containing Ni, Mn, and Cu elements have been studied as electrocatalysts.¹⁷¹ Lourenço et al. investigated the formation of carbon/metal oxides using the effect of solvent on the incorporation of Mn²⁺ on ZIF-67 and reported its OER performance.¹⁷² This work examined the effect of Mn²⁺ content in the ZIF-67 structure on the morphology and electrocatalytic performance. Mn/ZIF-67C(E) and Mn/ZIF-67C(M) exhibited good OER performance, which could be due to Mn³⁺ ions in the tetragonal sites and cobalt hydroxide/hydroperoxide functional groups. The presence of Mn³⁺/Mn⁴⁺ also improved the electrocatalytic activity. The electrochemical tests were carried out in 1 M KOH (pH = 14).

Bifunctional electrocatalysts can be applied in water-splitting reactions such as HER and OER, which are crucial in future conversion processes and renewable energy storage. Therefore, Li and co-workers¹⁷³ synthesized a hybrid nanostructure (Mn-CoP) composed of manganese-doped cobalt phosphide through the etching–carbonization–phosphatization of ZIF-67. The catalyst displayed outstanding activity in OER in 1 M KOH (pH = 14) solution, with an overpotential of 290 mV and a Tafel slope value of 76 mV dec⁻¹. For hollow CoP, the results were as follows: 342 mV, 102 mV dec⁻¹. Its performance in the OER is comparable with the commercial RuO₂ catalysts. The study showed that Mn doping optimized the hydrogen adsorption free energy, facilitating the HER activity. The presence of high valent Mn³⁺/Mn⁴⁺ species assisted in the easier generation of active metal-(oxy)hydroxide catalyst to promote the OER activity. Moreover, Mn-CoP nanosheets exhibited remarkable stability after long-term operation for HER and OER, which is ascribed to the synergistic effects of CoP NSs, graphitic carbon, and Mn and N-doped optimized electronic structure. Similarly, CoMnP/NF was also synthesized from the MOF-71 precursor for efficient HER activity in acidic/alkaline electrolytes.¹⁷⁴

NiMn-based BMOF NSs on MWCNT fibers (NiMn-MOF/MCCF) was investigated by Luan and Lou et al. through a simple hydrothermal procedure with subsequent ligand exchange, revealing its OER functional superiority with insignificant overpotential (282 mV at 10 mA cm⁻²).¹⁷⁵ The consistency of the Tafel slope (87 mV dec⁻¹), turnover frequency (0.34 s⁻¹ at 302 mV overpotential), increased FE (91%), and a greater C_dl (4.38 mF cm⁻²) indicated that a greater number of active sites were exposed in NiMn-MOF/MCCF. According to the EIS findings, NiMn-MOF/MCCF had the smallest semicircle, representing a charge transfer enhancement. Notably, 96% of the primary activity can be preserved 30 hours after the oxygen evolution reaction. Based on the XPS and XAFS analysis results, a mixture of high valence Ni^2+/3+ and Mn^3+/4+ ions was found, along with the respective presence of {NiO₆} and {MnO₆} environments. Considering the functional superiority of transition-metal oxyhydroxides with shared oxidation states and structural arrangements, it was concluded that NiMn-MOFs would possess interesting electrocatalytic activities. Based on DFT analyses, the electron density was near the Ni-MOF Fermi level (FL), which is typically considered an electronic structure found in semiconductors. However, given the apparent electron density near the Ni-MOF Fermi level, incorporating Mn ions makes free electrons available. The DOS enhancement can be mainly associated with the nickel 3d orbital hybridization with oxygen 2p orbitals as O atoms react with Ni atoms more strongly than the atoms of Mn. The Ni-MOF Fermi level enables Ni sites to accept or donate electrons. There is a significant distance between the Mn 3d orbital dominant band and the Fermi level, indicating the willingness of active manganese sites to accept electrons. The above evidence supports the potential of Ni sites as active OER centers, while efficient kinetics can be obtained through manganese incorporation.

The production of MOF-anchored nanoparticles or C-matrices derived from MOFs as ORR electrocatalysts is another useful procedure. Great electrocatalytic ORR activities were found for NPs, including non-noble metals on MOFs or C-matrix composites obtained from MOFs. Elbaz et al. focused on MOFs based on manganese, iron, cobalt, and copper with C₉H₃O₆ linkers (BTC₃) acquired within the activated carbon (AC), as shown in Fig. 15a–c. Considerable ORR activities were found for the studied MOF@AC composites in 0.1 M KOH (pH = 12). Besides, according to Fig. 15d, the functional superiority of Mn-MOF@AC was highlighted considering 0.92 V versus the onset potential of RHE and 4e⁻ transfer ORR compared with the relevant catalysts.¹⁷⁶ Hence, the metal ion type in MOFs mainly determines the functional characteristics of these catalysts with the decreasing order of Mn > Fe > Cu > Co.

Fig. 15 (a) Structure of H₃BTC and schematic presentation of M-BTC@AC; (b) TEM image of M-BTC@AC; (c) CV and (d) LSV curves of M-BTC@AC electrocatalysts recorded in 0.1 M KOH. Adapted with permission from ref. 176. Copyright 2018, the Royal Society of Chemistry.

A straightforward and mild method was proposed by Yao et al. to prepare multiple-lattice strains as a bifunctional NiMn-MOF@CoOOH hybrid.¹⁷⁷ It was believed that NiMn-MOF stabilized the structure and prevented material breakage throughout the electro-oxidation phase change while serving as an anchor point for the tight connection of Co ions. As reported by this study, CoOOH underwent lattice stretching and compression, building many vacancies and dislocations. Besides, these strains could accelerate ion conduction via tensile/compressive strain while introducing more sites with electromechanical activities. NiMn-MOF@CoOOH shows small values of 221 mV overpotentials at 10 mA cm⁻² in 1 M KOH (pH = 14) electrolyte. Ghising et al. focused on the fabrication of trimetallic Ni-Fe-Mn-MOF derived Ni-Fe-Mn-P/NC@NF ultrathin NSs (Fig. 16a), with the aim of proficient overall water splitting.¹⁷⁸Fig. 16b and c indicates how a bunch of Ni-Fe-Mn-P/NC@NF rose-like structures can be regularly formed on the nickel substrate. Ni-Fe-Mn-P/NC@NF was more efficient with faster kinetics due to the smaller values of 72 and 274 mV overpotentials at 10 and 30 mA cm⁻² related to HER and OER, respectively, and smaller values of 79.8 and 56.8 mV dec⁻¹ Tafel slopes compared to the controls. These results have been reported in 1 M KOH (pH = 14). As shown by the digital image of the alkaline water electrolyzer Ni-Fe-Mn-P/NC@NF (+,−) in Fig. 16d, hydrogen and oxygen gas bubbles were generated.

Fig. 16 (a) Synthesis, (b and c) FE-SEM images, and (d) digital photograph of the alkaline water electrolyzer Ni-Fe-Mn-P/NC@NF (+, −) (HER and OER). Adapted with permission from ref. 178. Copyright 2022, the Royal Society of Chemistry.

In brief, the electrocatalytic performance of V,Mn-based MOFs and their derivatives for water splitting can be significantly improved by some strategies. Multi-metallic electrocatalysts with optimal composition present a synergistic effect between multi metals. Metals on the electrode surface create many active sites that accelerate the electrocatalytic reactions. Doping is the most efficient strategy to improve the electrocatalytic performance so that the dopant element tunes the electronic structure and provide a synergistic effect between the dopant and host metals for improving the electrocatalytic performance.

3.2. Supercapacitors

The demand for energy is rapidly increasing for smart grids and electric vehicles, and tremendous efforts have also been devoted to developing energy storage devices.^179–182 Thanks to their fast-charging capability, high power density, and long lifetime, supercapacitors (SCs) are one of the good choices in energy storage.^183,184 SCs have found extensive applications in mobile electronics, memory, military, and high-power electric devices.¹⁸⁵ The choice of electrode materials can drastically affect the performance of the SCs. An ideal electrode material should have high conductivity, stability, and excellent surface area. Among various substances, carbon materials, metal oxides, and polymers have potential to be used in SCs.^186–188 However, the poor energy density of SCs is still a major bottleneck.

A novel class of materials with unique tunable structures and porosity, known as the metal–organic frameworks (MOFs), has recently attracted considerable attention in the field of energy storage as electrode materials.^189,190 The structure of MOFs is made up of metal ions and organic ligands. The high porosity of these structures and the presence of metal ions have made them a suitable candidate for redox reactions. The presence of open channels for ion transport and high surface area, which results in the uniform dispersion of metal sites and facilitates the accessibility of active sites by the electrolyte ions, are among the other advantages of MOFs in energy storage applications. Vanadium (V) is one of the transition metals with 5 electrons in its valence layer. The electron-rich valence of V results in its excellent pseudocapacitance. V-MOFs also enjoy a high surface-to-volume ratio, making it a suitable material for SCs.^191–193 Among various MOFs, Mn-MOFs are also introduced as an ideal electrode material for SCs due to their low cost and wide voltage range.^194,195

Owing to their high active surface and excellent surface-to-volume ratio, rod-like V-MOFs are a proper candidate for energy storage in SCs. The porous framework in MIL-47 is composed of V⁴⁺O₆ octahedral chains whose three-dimensional structure provides large pores. Therefore, MIL-47 could contribute to electron transport, presenting a proper electrode material for energy storage applications. In a study by Yan et al., rod-like MIL-47 was utilized as an electrode material for SCs.¹⁹¹ The specific capacitance of 572 F g⁻¹ was reported for this electrode material at a current density of 0.5 A g⁻¹.

Transition metal nitrides are a fascinating class of electrode materials with various advantages, such as high electronic conductivity, mechanical strength, and chemical stability against corrosive acids and bases.¹⁹⁶ Vanadium nitride (VN) has received one of the highest research attentions among these materials due to its enormous potential window and high energy density. As MOFs are ideal precursors in preparing numerous derivatives, V-MOFs can be used to prepare VN. Regarding the multiple advantages of VN, they suffer from poor cyclic stability such that the structure may collapse during the charge–discharge process. Various solutions have been developed to resolve this problem. These solutions include wrapping a thin layer of carbon on the VN surface or wrapping a layer of gel electrolyte on the surface of VN.¹⁹⁷

On the other hand, the cyclic stability of these materials is related to the type of surface oxide. Some studies have shown that the metal oxides on the VN surface can increase their potential window and specific capacitance.¹⁹⁸ Therefore, Liu et al. succeeded in the preparation of VN materials of VO₂ with surface single species (VN@VO₂), which can be applied in the SCs as an electrode material (Fig. 17a(i)).¹⁹⁹ Their results indicated the specific capacitance of 149.5 F g⁻¹ at a current density of 1 A g⁻¹ in 2 M KOH (pH = 14) with cyclic stability of 85% after 1000 cycles (Fig. 17a(ii and iii)). The presence of VO₂ on the VN surface effectively improved its cyclic stability.

Fig. 17 (a) (i) The preparation steps of VNs, (ii) CV curves of VN@sVO₂ at 50 mV s⁻¹, and (iii) cycling performance of VN@sVO₂-1.5 at 1 A g⁻¹ current density. Adapted with permission from ref. 199. Copyright 2020, Elsevier. (b) (i) Structural representation for the synthesis of the MS-V-CO, (ii) FE-SEM images of the MS-V-CO hollow microspheres, and (iii) the two-electrode device of the MS-V-CO//AC. Adapted with permission from ref. 201. Copyright 2021, Elsevier.

Based on the literature, using vanadium as a dopant can enhance the specific surface area and improve the electrochemical performance due to the decline in the ion transport resistance.²⁰⁰ Hollow-type morphologies provide a high surface area. Niknam et al. prepared multi-shelled vanadium-doped Co₃O₄ (MS-V-CO) hollow spheres using MOF templated through a solvothermal method for SCs (Fig. 17b(i and ii)).²⁰¹ Their results indicated that the proper performance of this electrode material, with a unique structure and good conductivity could be justified. The specific capacitance of the developed system was calculated to be 1593 F g⁻¹. Following this proper performance, they considered a two-electrode setup to investigate further the system's performance (Fig. 17b(iii)). The MS-V-CO//AC asymmetric device also exhibited excellent performance with maximum energy density.

It has been accepted that the performance of SCs is mainly dependent on their electrode materials. In this regard, metal oxides and metal hydroxides are proper candidates for SCs. Thanks to their high specific capacitance and energy density, metal oxides are increasingly utilized in SCs as substituents for carbon materials. In recent years, vanadium oxides are benefited from numerous advantages due to their abundance of sources, low cost, and various oxidation states. VO₂ has high charge storage capability and conductivity, and due to having mixed valence, it offers a vast potential window and proper supercapacitor performance.²⁰² Zhuang et al. reported using VO₂@CC derived from V-MOF as a flexible electrode for SCs.²⁰³ Their results indicated that the type of precursor affects the performance of the metal oxide. MOF-derived metal oxide offered a high surface area and porous structure, which enhanced the energy storage performance, leading to high specific capacitance and a wide potential window.

Mixed metal oxides have received significant attention for energy storage due to synergistic effects between the metal species, improved conductivity, and redox chemistry.²⁰⁴ Copper and cobalt vanadates have received significant attention due to their rich redox chemistry. Owing to the strong bond between vanadium and oxygen, the oxidation state of vanadium does not reach zero during the charge–discharge process; this advantage leads to lower volume changes of vanadium-based oxides compared to other metal oxides. Sekhar et al. synthesized core–shell-like CuV₂O₆ and Co₃V₂O₈ (CuV–CoV) composite on a copper foam.²⁰⁵ This group utilized copper foam substrate due to its high conductivity and three-dimensional architecture, which resulted in high electrolyte accessibility and accelerated kinetics. The use of this substrate also resolved the dead mass issue. The surface area of the substrate increased by the vertical growth of the CuV NRs, leading to the improved performance of the electrode material. More importantly, MOF-derived Co₃O₄ offered high charge storage capacity due to its high porosity and surface area (Fig. 18a(i)). So, the redox chemistry for the CuV–CoV electrode reveals the superior performance of this electrode material (Fig. 18a(ii)).

Fig. 18 (a) (i) Structural merits of CuV NRAs@CoV NHPs architecture, (ii) CV curves of electrode materials. Adapted with permission from ref. 205. Copyright 2020 Wiley-VCH. (b) (i) Fabrication process of Mn-MOFs, (ii) layered structure of Mn-MOF, and (iii) charge–discharge curves of Mn-MOF 140. Adapted with permission from ref. 213. Copyright 2020, Elsevier.

Advances in electronic devices have extended the use of SCs, including shape-memory SCs, self-charging SCs, and electrochromic SCs.^206,207 Electrochromic materials refer to substances in which the redox reactions lead to visible color variation. Multi-colored electrochromic asymmetric supercapacitors enjoy the precise control of light modulation by monitoring the device charge content, hence preventing the overcharging/discharging of the device.^208,209 Transition metal oxides have numerous applications due to their optical memory effect and natural abundance.²¹⁰ V₂O₅ can exhibit anodic and cathodic coloration upon the reversible intercalation/deintercalation of alkaline cations (e.g., Li⁺), making it suitable for multicolor displays. Dewan et al. (2022) used MOF-derived V₂O₅ as an electrode material in supercapacitors.²¹¹ This work used PANI films and MOF-derived V₂O₅ as cathode and anode electrodes. Their investigations revealed the proper coloration efficiency of MOF-derived V₂O₅ with significant optical modulation. Multiple-color states were also formed in different charging–discharging states, making it possible to determine the energy storage with the naked eye precisely.

Portable innovative electronics require fiber-shaped integrated devices. These devices have received a considerable deal of attention in the field of energy storage due to their high flexibility and lightweight. Despite the enormous progress in this field, the proper application of multifunctional fibers in one integrated configuration for simultaneous energy storage and use is a great challenge. Accordingly, Pu et al. (2021) succeeded in preparing multifunctional fibers derived from V-MOF nanowires grown on carbon nanotube fiber (V-MOF NWs@CNT fiber) for energy storage applications.²¹² They employed a fiber-shaped asymmetric supercapacitor using CoNi-LDH NSs@V₂O₅ NWs@CNT fiber and vanadium nitride (VN) NWs@CNT fiber as cathode and anode, respectively. Their results indicated a working voltage of 1.7 V with high energy density.

MOFs prepared with various organic linkers have different morphologies. Thus, they can exhibit other electrochemical performances. Therefore, the morphology, pore structure, and composition can be varied to improve the MOFs' performance in different applications. Pristine MOFs can be employed in SCs due to their highly porous structure. Mn-MOFs can facilitate access to the ions of the electrolyte due to their layered structure, short ion diffusion pathways, and open space, reflecting their excellent electrochemical performance. Due to their cost-effectiveness, the H₂BDC linkers and Mn species are ideal candidates for supercapacitors. Shinde et al. synthesized 2D layered Mn-MOF nanostructures assembled on Ni foam at different temperatures as an electrode material for SCs (Fig. 18b(i and ii)).²¹³ The capacitance of 10.25 mF cm⁻² was observed for this electrode material in 2 M KOH at a current density of 1 A g⁻¹ (Fig. 18b(iii)).

In addition to electrode material, the electrolyte is another critical factor in the energy storage performance of the SCs. In this context, adding redox additive electrolytes to the aqueous electrolytes could be an effective solution. The electrolyte can effectively modulate the potential window and affect the electrode material's performance.²¹⁴ The presence of redox active species in the electrolyte accelerates the kinetics of the redox reactions.²¹⁵ The existence of redox-active species in the electrolyte also decreases the solution and charge transfer resistance.²¹⁶ In this regard, Sundriyal et al. studied a layered Mn-MOF in the presence of the redox additive electrolyte (0.2 M K₃[Fe(CN)₆] in 1 M Na₂SO₄ 0.2 M KFCN).²¹⁷ They found that the porous structure of Mn-MOF electrode material can show a synergistic effect with KFCN electrolyte, leading to the enhanced performance of the SCs.

Broadening the voltage window could be a practical approach for improving the supercapacitors' performance and increasing the energy density.²¹⁸ Pseudocapacitive materials have high specific capacities, and their voltage window can be extended by fabricating hybrid supercapacitors.²¹⁹ Among various electrode materials, transition metal oxides could be a proper candidate. For instance, Mn₂O₃ has received particular attention due to its nontoxicity and low cost. Chen et al. reported the fabrication of hierarchical Mn₂O₃ hollow microspheres from Mn-MOF sphere precursors, which were then used as supercapacitors.²²⁰ Thanks to its hierarchical structure, this electrode material managed to enhance the electrochemical performance of the system due to its more active sites and faster electron transfer. The presence of oxygen vacancies can also accelerate ion diffusion and electron conduction in this structure.

MnO₂ has also drawn a considerable deal of attention in the field of energy storage supercapacitors due to its high theoretical specific capacitance. The interesting point about this electrode material is the high dependence of its charge storage performance on the crystallographic phase. Yuan et al. addressed this interesting point. To this end, they used Mn-MOFs to achieve different crystal phases of MnO₂.²²¹ In this work, MnO₂ with varying structures of crystal (α-MnO₂, β-MnO_2, and δ-MnO₂) was assessed. The results indicated morphology and crystal structure as the key factors affecting the electrode material's performance. δ-MnO₂ showed better performance with the highest specific capacitance due to its higher surface area and nanosheet morphology. Its layer structure also provided easier access to the ions of the electrolytes, and its structure increased the insertion/extraction process of cations.

In addition to metal oxides, transition metal phosphides have received significant attention as promising electrode materials for supercapacitors due to their chemical stability, high electrical conductivity, and high redox activity.²²² Compared to transition metal oxides, transition metal phosphides have shown higher conductivity and capacitance, which could be assigned to the electronegativity of phosphorous compared to oxygen, which can accelerate the electron transfer in phosphides. Based on these findings, Manikandan et al. successfully deposited Co-MOF on carbon cloth substrate followed by Mn doping; MnCoP on carbon cloth (MCP/CC) was finally achieved by the phosphorization process (Fig. 19a).²²³ The mentioned research group assesses the performance of this electrode material for supercapacitor applications. The three-dimensional porous structure can accelerate and facilitate ion transport and improve conductivity, confirming the excellent electrochemical performance of this electrode material. This binder-free electrode material exhibited an aerial capacitance of 338 mF cm⁻² at a current density of 2 mA cm⁻² (Fig. 19b and c).

Fig. 19 (a) Growth steps of MOFs on carbon cloth, (b) charge–discharge curves of the electrode materials, (c) Nyquist plots of the electrodes. Adapted with permission from ref. 223. Copyright 2021, Elsevier.

Recently, MOF-derived hydroxides have been used as electrode material in SCs. In this class of materials, metal sources preserve the properties of MOFs during the Faradaic reactions to enhance the electrochemical stability and conductivity.²²⁴ Liu et al. reported the use of Mn/Ni-MOF-74 as a precursor to synthesize Mn–Ni double hydroxide (Fig. 20a(i)).²²⁵ The resulting electrode material can reliably perform the intercalation/deintercalation of electrolyte ions and improve the electrochemical performance due to its suitable pore structure and sufficient space for charge storage (Fig. 20a(ii)). The results introduced the co-existence of mesoporous and microporous structures as one of the reasons for the high specific capacitance of this material since mesopores accelerate electron transport.

Fig. 20 (a) (i) Synthesis steps of MnNi double hydroxide, (ii) charge–discharge of electrodes at a current density of 1 A g⁻¹. Adapted with permission from ref. 225. Copyright 2020, Elsevier. (b) (i) Representation of charge storage mechanism in the electrode, and (ii) charge–discharge curves of the electrodes at 1 A g⁻¹ current density. Adapted with permission from ref. 226. Copyright 2019, Elsevier.

In contrast, microporous structures guarantee abundant active sites with high surface area. Moreover, the presence of active metals in the structure of this material led to the faradaic contribution. Additionally, spear-shaped morphology further made this material suitable for energy storage applications. In another report by Du et al., NiCoMn-OH with a unique multi-order microarchitecture was successfully synthesized using the ZIF-67 template.²²⁶ This porous micro–nano framework has a high specific surface area; moreover, nanosheet stacking in this structure resulted in a 3D multi-order hollow polyhedral structure, which ideally accelerated ion/electron transport and improved the electrochemical performance (Fig. 20b(i and ii)). With its hollow polyhedral structure, NiCoMn–O had numerous active sites. On the other hand, nanosheets were vertically grown on the polyhedrons, further offering abundant active sites for electrochemical reactions. The synergistic effect between Co, Mn, and Ni also further improved the performance of this structure such that the NiCoMn-OH//AC device exhibited an energy density of 43 W h kg⁻¹.

Two-dimensional layered materials are among the promising materials for energy storage applications; thanks to their large d-spacing, these structures allow free migration of the electrolyte ions between the layers. On the other hand, these layered materials have a high surface area and numerous active sites for electrochemical reactions. Layered double hydroxides (LDHs) also possess a layer-by-layer structure comprising metal ions with +2 and +3 oxidation states.^227,228 Layers are positively charged, and the charge of different anionic layers is intercalated to neutralize the charge.^229,230 Therefore, the interlayer distances are under the influence of the anion size.^231,232 The synthesis of these compounds by MOF precursors compared with other routine methods could offer advantages such as better morphology control and enhanced surface area at room temperature.²³³

CoMn-LDH has been utilized as a proper electrode material in alkaline solutions. This material is, however, unstable in this solution due to the instability of Mn(III) ions. Therefore, Liu et al. found that identifying the active phase can effectively design an efficient electrode material. Using MOF precursors, they obtained CoMn-LDH using different Mn solutions (i.e., MnSO₄, Mn(NO₃)₂, and MnCl₂) (Fig. 21a).²³⁴ They found that the presence of different anions can affect the structure of the layers, phase transformation, and charge storage (Fig. 21b). The most significant interlayer space belonged to CoMn-LDH in the presence of sulfate solution, and the highest areal capacity was 582 mC cm⁻².

Fig. 21 (a) Synthesis steps of CoMn-LDHs, (b) the effects of different anions on CoMn-LDH structure and properties. Adapted with permission from ref. 234. Copyright 2019, the American Chemical Society.

Peng et al. synthesized ternary MoS₂/Mn-MOF/MWCNT composite for SCs. Based on their experiments, a ratio of 1 : 4 : 1 for m(MoS₂) : m(Mn-MOF) : m(MWCNT) led to optimum performance with 862.73 F g⁻¹ specific capacitance (Fig. 22a).²³⁵ Another study by Yao et al. focused on preparing K_0.5Mn₂O₄@Mn-MOF-8 nanosheet arrays, in which K_0.5Mn₂O₄ played the role of asymmetric supercapacitor's template and precursor (Fig. 22b). Their study reported a considerably large specific capacitance for K_0.5Mn₂O₄@Mn-MOF-8 when the Mn³⁺/Mn⁴⁺ redox couple increased along with conductivity because of the intercalating K_0.5Mn₂O₄ alkali cations (K⁺).²³⁶ Han and co-workers sought to fabricate Mn–Ni bimetallic MOFs anchored on MWCNTs (Mn/Ni-MOF@MWCNTs) active anchoring sites considering a 793.6 F g⁻¹ specific capacitance at 1 A g⁻¹ and 74.92% capacitance retention following 1000 cycles.²³⁷ Their results confirmed the contribution of the studied sites to electron transfer enhancement and better structural integrity. According to Fig. 22c(i–iii), the composite resistance decreases considerably due to the synergy between manganese and nickel. In 2022, a study by Liu et al. focused on Ni-doped Mn-MOF as electrode materials used in supercapacitors, revealing a 779.6 C g⁻¹ specific capacity and a 1676.6 F g⁻¹ specific capacitance at 1 A g⁻¹.²³⁸

Fig. 22 (a) The preparation steps and brief storage of energy mechanism of the MoS₂/Mn-MOF/MWCNT composite. Adapted with permission from ref. 235. Copyright 2022, Elsevier. (b) The synthesis process of K_0.5Mn₂O₄@Mn-MOF-8 nanosheets. Adapted with permission from ref. 236. Copyright 2020, the American Chemical Society. (c) (i) The structure of Mn/Ni-MOF@MWCNT and its reaction mechanism, (ii) HRTEM image of Mn/Ni-MOF@MWCNT, and (iii) CV curves of Mn/Ni-MOF@MWCNT at various sweep rates. Adapted with permission from ref. 237. Copyright 2021, Elsevier.

A new cathode material based on core@shell structure was introduced as a positive electrode in asymmetric SCs by enfolding (Mn⁻¹)Co_xS_y nanosheet arrays derived from MOFs in specific (Ni–Cu)OHs marigold flower-like nano reservoirs.²³⁹ The ultrahigh 2.19 mA h cm⁻² areal capacity was delivered by the multi-component (Mn⁻¹)Co_xS_y@(Ni–Cu)OHs core@shell nanosheet arrays at 1 mA cm⁻². As shown in Fig. 23a, 94 W h kg⁻¹ ultra-high energy density performance was delivered at a 963.2 W kg⁻¹ power density while retaining 92.08% of capacity following 10 000 cycles. According to the results obtained by Lam et al. in 2021, Mn-MOF is transformable into nanoparticles of MnO/Mn₃O₄ with uniform dispersion in mesoporous graphitic carbon composite (MnO/Mn₃O₄@GC), exhibiting better supercapacitive function with 194 F g⁻¹ specific capacitance and retaining 82% of capacity following 5000 cycles (Fig. 23b and c).²⁴⁰

Fig. 23 (a) Design and construction of MOF-derived (Mn-1)Co_xS_y@(Ni–Cu)OHs marigold flower-like core@shell as cathode materials and (Mn–Fe₁₀)S_x@graphene foam as anode materials along with asymmetric supercapacitor device. Adapted with permission from ref. 239. Copyright 2018, the American Chemical Society. (b) Synthesis of the Mn₃O₄@C and MnO/Mn₃O₄@GC from Mn-MOF and (c) charge–discharge curves of the supercapacitors. Adapted with permission from ref. 240. Copyright 2021, Wiley-VCH.

In this section, we summarized the application of V, Mn-containing MOFs as electrode materials for supercapacitors. For this type of MOFs, some limitations have been reported that they can be resolved by some strategies. Excellent surface-to-volume ratio and high active surface area in rod-like and hollow morphologies of V-MOF promote the supercapacitive performance. MOF-derived metal oxides with high surface area and porous structure exhibit high specific capacitance, wide potential window and high energy density for SCs. Synergistic effects between the metal species in V, Mn-MOFs derived mixed metal oxides improve the redox chemistry and their conductivity. In MOF-derived hydroxides, metals preserve the MOF's properties during the faradaic reaction to promote the conductivity and stability of the electrode material.

3.3. Batteries

The increasing demand for clean energy has motivated researchers to find green energy storage solutions.^{206,207,241–243} Rechargeable batteries have shown the potential to be used in energy storage applications due to their high storage efficiency, environment-friendly operation, and high cycling stability.²⁰⁸ In these systems, electrode materials play a fundamental role. The rational design and selection of electrode materials play a decisive role in these energy storage systems.²⁴⁴ An ideal electrode material should have electrical/ionic conductivity, porosity, thermal and chemical stability, and suitable lattice sites for charge and ion storage.^41,245 MOFs have exhibited promising features such as porosity and high specific surface area, which can be employed in batteries.²⁴⁶ Among MOFs, V and Mn-based MOFs can be effectively utilized as electrode material in batteries with high cyclic stability due to their various oxidation states and open framework structure.^247–249

Lithium–sulfur batteries (LSBs) are from reserves of active sulfur materials that have shown high specific capacity.^250,251 They, however, suffer from drawbacks such as the poor conductivity of sulfur and volume change during the charge–discharge process. On the other hand, they can result in polysulfide intermediates, which may dissolve in the electrolyte, leading to the shuttle effect. The mentioned weaknesses have hindered the commercialization of these batteries. In this regard, using cathode materials can decrease the polysulfide diffusion and enhance the conductivity, which will be helpful. Thanks to their high specific surface area, porous structure, and adsorption ability, MOFs can effectively immobilize lithium polysulfide intermediates and, thus, improve the stability of the batteries.^252,253 In this context, the design of a MOF-based sulfur host in which the features of MOFs are maintained could be highly efficient. Yang et al. designed V-MOF (MIL-47)-derived V₂O₃@C hollow microcuboid (Fig. 24a)²⁵⁴ and used it as a sulfur host. The hollow micro cuboid morphology with a hierarchical lasagna-like structure provides channels for ion transport. At the same time, carbon framework physical confinement and V₂O₃ chemical adsorption prevented the shuttle effect, giving rise to good cycling stability for the V₂O₃@C/S composite cathode (Fig. 24b). In another study by Chen and colleagues, density functional theory was employed to assess two-dimensional porphyrin-like MOFs. Their results indicated remarkable chemical interactions of V-MOFs with lithium polysulfides, which decreased the shuttle effect, improving the performance and increasing the energy density.²⁵⁵ In 2021, the synthesis of MnM-MIL-100 bimetallic was carried out by Li et al. with no changes in the main morphology to store the electrochemical energy (Fig. 25a and b). The MnNi-MIL-100@S cathode had the most optimum performance of Li–S batteries, indicating an approximately 708.8 mA h g⁻¹ reversible capacity following 200 cycles.²⁵⁶

Fig. 24 (a) Three main properties of the V₂O₃@C/S electrode material; (b) fabrication process of the V₂O₃@C/S. Adapted with permission from ref. 254. Copyright 2020, the Royal Society of Chemistry.

Fig. 25 (a) Preparation of MnM-MIL-100 and (b) GCD profiles at a current density of 0.1 C. Adapted with permission from ref. 256. Copyright 2021, Wiley-VCH. (c) The MOF cathode∥Zn anode ZIBs and (d) cycling performance of Mn-H₃BTC-MOF-4. Adapted with permission from ref. 260. Copyright 2021, the American Chemical Society.

Zn-ion batteries are another type of essential battery for energy storage applications due to their intrinsic safety, high theoretical capacity, low cost, and good ionic conductivity in aqueous electrolytes.^257,258 These batteries, however, suffer from several drawbacks, such as self-aggregation, active material dissolution, and structural collapse.²⁵⁹ The evident point is that the design of a cathode material with a stable crystal structure and abundant channels for ion migration during the charge–discharge process is necessary. In 2021, a novel type of coordinated unsaturated Mn-MOF was introduced by Yin et al. as an advanced cathode for zinc-ion batteries.²⁶⁰ Coordinated Mn unsaturation was conducted with oxygen atoms of two adjacent carboxylic acid ions, indicating highly efficient Zn²⁺ transfer and electron exchange due to the appropriate degree of unsaturated coordination. Hence, great intrinsic activities and quick electrochemical reaction kinetics are ensured throughout the repeated processes of charging/discharging (Fig. 25c and d). Their synthesized MOF-based electrode had a 138 mA h g⁻¹ capacity at 100 mA g⁻¹ and a long lifespan (retaining 93.5% capacity following 1000 cycles). Mondal et al. reported a highly porous V-MOF as a cathode material for Zn-ion batteries.²⁶¹ This highly 3D porous MOF with mesoporous cages facilities the insertion and de-insertion of Zn ions in the electrochemical system. V-MOF exhibited a high specific capacity of 362 mA h g⁻¹ at 0.2 A g⁻¹ current density. It is worthy to note that the porosity of V-MOF is beneficial for contact between the electrolyte and electrode in the electrochemical system.

V-MOFs have shown high stability due to their multiple valence states and open framework, which explain their extensive application in zinc-ion batteries.²⁶² The performance of the three-dimensional conductive V-MOF nanowire-bundle arrays with the hierarchical structure on carbon nanotube fibers was explored by He et al. for ZIBs (Fig. 26a(i)).²⁶³ The mentioned structure offered high porosity and conductivity, giving rise to proper performance with high volume capacity (101.8 mA h cm⁻³ at a current density of 0.1 A cm⁻³). Based on the results presented by this research team, the V-MOF-48//Zn battery exhibited high cyclic stability and flexibility (Fig. 26a(ii and iii)). Ding and colleagues investigated porous V₂O₃@C materials for zinc-ion batteries (Fig. 26b(i)).²⁶⁴ Their results showed the high conductivity of this material due to its unique channels and proper pore size distribution, offering a good rate capability for zinc-ion batteries (Fig. 26b(ii)). Another study by this group addressed porous V₂O₅ nanoplates derived from MOF for zinc-ion batteries. Their results suggest a high energy density of 230 W h kg⁻¹.²⁶⁵ Gong et al., in 2022, introduced two-dimensional hierarchical V₂O₅@graphene derived from V MOF@graphene and evaluated its performance in zinc-ion batteries.²⁶⁶ The two-dimensional architecture of this substance possessed numerous Zn²⁺ active sites, which resulted in high conductivity. Moreover, V₂O₅ collapse during the cyclic process was prevented in addition to presenting proper rate capability. Liu and co-workers reported V₂O₅@CNT derived from V-MOF@CNT with nanorod-like porous structure as a cathode material for Zn-ion batteries.²⁶⁷ The porosity of the structure promoted the ion diffusion, leading to improved electrochemical performance. In another study conducted by Hu et al., the synthesis of 3D layer-by-layer MnO_x hierarchical mesoporous from templates based on Mn-MOF-74 resulted in an appropriate cathode for aqueous Zn-ion batteries with considerable efficiency because of the controlled MOF ligand exchange with OH⁻ ions and easy conversion into Mn₃O₄ or δ-MnO₂ counterparts.²⁶⁸ According to their findings, the synthesized 3D materials had persistent superiority in Li storage, particularly at high rates, due to their properly coordinated structure.

Fig. 26 (a) (i) Fabrication process for the hierarchical structure of V-MOF@CNTF, (ii) schematic illustration of V-MOF-48//Zn battery, (iii) cycling behavior of the V-MOF-48//Zn battery. Adapted with permission from ref. 263. Copyright 2019, Elsevier. (b) (i) Process of charge/discharge in the V₂O₃@C electrode material and (ii) cycling performance of V₂O₃@C. Adapted with permission from ref. 264. Copyright 2019, the American Chemical Society.

Li-ion batteries are a promising and clean power source with high reversible capacity.²⁶⁹ Thanks to this distinctive feature, Li-ion batteries have found extensive applications in portable electronic devices and electric vehicles, further attracting the attention of researchers. However, these batteries suffer from low cycling stability and energy density, requiring further research to resolve the mentioned problems. The design and fabrication of novel materials that can well substitute the current graphite anode and offer desirable stability and capacity are among the leading research priorities in this field.

Transition metal oxides are another class of functional materials with various morphologies that can be employed in diverse applications.^270,271 These materials, for instance, can be utilized in lithium-ion batteries due to their higher specific capacity than commercial graphite.^272,273 Environmental compatibility is the other advantage of transition metal oxides, making them suitable for application in lithium-ion batteries.^274,275 The role of these materials as an anode in the mentioned batteries is limited due to their volumetric changes and pulverization problem in the charge–discharge process.²⁷⁶ Manganese monoxide (MnO) is one of the interesting materials in this field. MnO enjoys abundant resources, low conversion potential, and voltage hysteresis. The poor rate performance of MnO, however, limits its application. One of the approaches to resolve this issue is forming a three-dimensional conductive network by compositing carbon materials with MnO.²⁷⁷ The use of carbon materials accelerates charge transport and decreases the volume expansion-induced stress.²⁷⁸ Accordingly, Guo et al. succeeded in the synthesis of MOF-derived MnO with nanosheet morphology. They also prepared a composite using graphene oxide to increase the electrode–electrolyte contact area further and improve the conductivity (Fig. 27a and b).²⁷⁹ The use of MnO@rGO composite in lithium-ion batteries resulted in better rate performance. Nanosheets facilitated the diffusion of the electrolyte ions, and a synergistic effect between graphene and MnO also prevented the agglomeration of MnO microcrystallites, leading to the improved performance of the electrode material (Fig. 27c and d). In this context, Sun et al. synthesized MnO with various morphologies using Mn(PTA)-MOFs; they then utilized MnO/C hybrids as an anode material for lithium-ion batteries. They reported the better performance of spindle-like MnO/C microrods compared to other morphologies as they showed high cyclic stability after 200 cycles.²⁸⁰

Fig. 27 (a) Synthesis protocol of the MnO@GO composite, (b) presentation of cations in graphene layers and MnO nanosheets, (c) Nyquist plots, and (d) cycling performance of MnO@rGO and MnO electrodes. Adapted with permission from ref. 279. Copyright 2019, the Royal Society of Chemistry.

MnO/C@rGO nanocomposites were utilized by Tian et al. for lithium-ion batteries (Fig. 28a(i)).²⁸¹ This study showed an improvement in the conductivity of the composite in the presence of graphene. Due to this composite's two-dimensional structure and high surface area, the diffusion of Li ions accelerated, leading to enhanced cyclic stability (Fig. 28a(ii)). Niu et al. synthesized mesoporous MnO/C–N nanostructures using MOF precursors as an anode material in Li-ion batteries.²⁸² They observed the high capacity of Mn/C-N nanoparticles (1085 mA h g⁻¹) due to the excellent surface area of these unique nanostructures. Chen et al. also introduced Mn-MOF-derived mixed-valent manganese oxide on carbon sheets (MnO_x-CSs) as an anode material for Li-ion batteries (Fig. 28b(i)).²⁸³ The results of their investigations indicated the proper performance of MnO_x-CSs-600 in Li-ion batteries with a capacity of 1217 mA h g⁻¹ at 200 mA g⁻¹. Two-dimensional carbon sheets served as an appropriate support for the growth of MnO_x in these electrode materials, which resulted in a high specific surface area.

Fig. 28 (a) (i) Formation steps and (ii) cycling stability of MnO/C@rGO composite. Adapted with permission from ref. 281. Copyright 2019, Elsevier. (b) (i) Synthesis steps of the MnO_x-CSs nanocomposite, (ii) cycling performance, and (iii) rate performance of MnO_x-CSs-600. Adapted with permission from ref. 283. Copyright 2017, Elsevier.

On the other hand, the high conductivity of the carbon sheet facilitates ion and electron transport between the electrode and electrolyte offered a good rate capability for the mentioned system (Fig. 28b(ii and iii)). Li electrochemical reactions of the V^IV(O)(bdc) [MIL-47] framework were examined in the study of Kaveevivitchai et al., who stated that small ions such as Li⁺ were readily lodged due to the presence of big open channels in the V-MOF. Vanadium(IV) has redox properties, which results in its application as a rechargeable intercalation electrode in Li batteries.³²

The synthesis of ZnMnO₃/C nanoparticles was performed by Hu et al. utilizing Mn-MOF-5 as an advanced electrode material in Li-based batteries (Fig. 29). The porosity of Mn-MOF-5 makes it suitable for Li⁺ transport as it offers short diffusion pathways and alleviates the volume changes throughout cycling. Besides, carbon doping in ZnMnO₃ improves the conductivity and enhances Li⁺ adsorption, while a high reversible capacity and favorable rate capability are also obtained.²⁸⁴

Fig. 29 (a) The synthetic process of ZnMnO₃/C using Mn-MOF-5 as a sacrificial template, (b) cycling performance at 0.1 A g⁻¹, and (c) rate capability of ZnMnO₃/C and ZnMnO₃ at different current densities. Adapted with permission from ref. 284. Copyright 2022, the Royal Society of Chemistry.

As suggested by Cao et al., the design and control of the size of hollow structures play a decisive role in improving the cyclic stability of electrode materials in the batteries. They studied Mn-MOF-derived mini-hollow polyhedron Mn₂O₃ for Li-ion batteries.²⁸⁵ They examined the effect of the hollow size on the cyclic performance (Fig. 30a–c). Thanks to the sufficient space for volume expansion in these mini-hollow structures, a structural evolution occurred for the formation of hierarchical nanostructure with the homogenous dispersion of nanoparticles, giving rise to proper cyclic stability after several cycles. In the case of bulk polyhedrons, however, there is a lack of space to prevent inward volume expansion; hence, a hierarchical nanostructure is formed with a congested core, and agglomeration and collapse occur in such structures. In a large-hollow electrode, a hierarchical structure is formed after the first cycle, which is prone to collapse due to the lack of balance between interactions occurring between nanoparticles and inner cavities (Fig. 30d). Findings have shown the better energy storage performance of mixed metal oxides (compared to single metal oxides) in batteries due to the mechanical stability and high conductivity of these mixed metal oxides.²⁸⁶ In this regard, multivalent metal oxides with various metal cations have exhibited improved electrochemical performance due to the synergistic effect between different cation species and their interfacial effects.²⁸⁷

Fig. 30 (a–c) Illustration of structure evolutions of Mn₂O₃ and (d) cycling stability of Mn₂O₃ electrodes at 1 A g⁻¹ current density. Adapted with permission from ref. 285. Copyright 2015, Wiley-VCH.

Interestingly, MOF-derived mixed metal oxides have shown good rate performance for Li-ion batteries.²⁸⁸ Such information motivated Soundharrajan et al. to synthesize Co₃V₂O₈ using MOF-based intermediates.²⁸⁹ Investigations of this group with sponge-like morphology of materials showed that the unique morphology of this electrode material with an ordered array of MOF networks offered considerable rate performance (430 mA h g⁻¹ at 3200 mA g⁻¹). In another study by Hu and colleagues, the use of Mn-1,4-benzenedicarboxylate MOF in the Li-ion batteries was evaluated before and after heat treatment, which showed an improvement in the specific discharge capacity after the heat treatment.²⁹⁰ They claimed that the presence of coordinated dimethylformamide in the MOF structure had an adverse effect on the Li-ion batteries such that solvent removal improved the electrode material's performance. In 2021, the fabrication of Zn₂VO₄ nanoparticles with encapsulation in N-doped nanocarbon networks was carried out by Fang et al. using V-Zn bimetallic MOFs.²⁹¹ The application of the fabricated material for the anode in Li-ion batteries led to a significant reversible capacity of 807 mA h g⁻¹ at 0.5 A g⁻¹ along with a considerably high performance of 372 mA h g⁻¹ at 8.0 A g⁻¹.

The prolonged cycling performance stability was also ensured because the bimetallic material had intrinsic synergic impacts and several multiple valence states for V. Aqueous rechargeable batteries are another class of batteries used in energy storage applications. Thanks to their high ionic conductivity, inexpensive electrolyte salts, and high safety, these batteries can overcome the drawback of Li-ion batteries.²⁹² Facile synthesis methods at low temperatures and facilitating the diffusion path of guest ions are among the critical issues requiring extra attention in designing these electrode materials. Due to their ideal crystal structure, Prussian blue analogues (PBAs) have recently been used in rechargeable batteries.²⁹³ These MOFs have large lattice parameters that favor energy storage as they facilitate ion diffusion and promote structural stability in successive insertion/extraction. This framework also exhibited poor bonding with ions, decreasing the activation energy for guest ion transport.²⁹⁴ Despite these advantages, these MOFs are limited by their low specific capacity in aqueous electrolytes. These limitations can be assigned to the fact that only transition metal ions are electrochemically active in these structures. Vanadium hexacyanoferrate (V/Fe PBA) was introduced by Lee et al. to resolve these limitations in aqueous rechargeable batteries.²⁹⁵ They observed accelerated charge/discharge rates in these electrode materials due to the multiple-electron redox reactions of V and Fe ions. The open structure and presence of a 3D H-bonding network also improved the discharge capacity in these electrode materials.

Li–O₂ batteries are another class of batteries with high theoretical energy density.²⁹⁶ They are also accompanied by challenges, such as different side reactions due to reactive oxygen radicals, which can attenuate the cyclability. The use of electrode materials capable of enhancing oxygen reduction or evolution reactions could be a helpful solution. MOF-74 has one-dimensional channels with abundant open sites on the surface of the channel, which are effective in the adsorption of O₂. This feature can facilitate the formation and decomposition of the oxygen reaction products in the air electrodes due to the discharge process. Accordingly, Kim et al. utilized MnCo-MOF-74 cathode electrode material in the Li–O₂ batteries.²⁹⁷ This bimetallic MOF has shown high discharge capacity thanks to the porous structure and the effect of Mn- and Co-metal clusters. As reported by Wu et al., a 9420 mA h g⁻¹ primary capacity subject to 1 atm oxygen in robust Mn-MOF-74-based Li–O₂ batteries led to values over four times greater than those achieved by cells with no MOF (Fig. 31a(i and ii)). According to their findings, the O₂ molecule population increased in the pores because of the available open metal sites across uniform channels, facilitating the efficient reaction and providing a higher capacity.²⁹⁸

Fig. 31 (a) (i) A Li–O₂ cell using Mn-MOF-74 and (ii) discharge profiles of the Li–O₂ cells using Mn-MOF-74 compared to other samples. Adapted with permission from ref. 298. Copyright 2014, Wiley-VCH. (b) (i) Synthesis steps of MnO@NC-G, (ii) the structural features of Mn(II) catalysts for Li–CO₂ batteries. Adapted with permission from ref. 302. Copyright 2019, the Royal Society of Chemistry.

CO₂ utilization and conversion have attracted the attention of researchers in resolving environmental crises.^299,300 Recently, Li–CO₂ batteries have emerged as a novel strategy for CO₂ capture and electrical energy storage as well as resolving the issues of Li–air batteries.³⁰¹ These batteries could ideally supply power in places with high CO₂ concentrations, such as factories or even on Mars. Li–CO₂ batteries encounter several challenges, including short cyclic life and poor stability. In this class of batteries, the activity of the electrode for the decomposition of Li₂CO₃ depends on the dispersion of catalytic species and fast electron transport, especially at high current densities. The deposition and decomposition of discharge products also play a decisive role in the cycle life of cathode materials. Li et al. used Mn-MOF for the synthesis of MnO, which was embedded in a nitrogen-doped carbon framework (Fig. 31b(i and ii)).³⁰² In this system, graphene acts as a conductive support and links MnO@NC in a three-dimensional network and affects electron transport. On the other hand, Mn(II) centers are effective in the decomposition of discharge products. Therefore, high-rate capability and long cycle life can be achieved by the MnO@NC-G cathode (Fig. 31b(iii)).

In brief, promising strategies have been reported to resolve some drawbacks in different rechargeable batteries in this section. The design of cathode materials in Zn-ion batteries with a stable crystal structure and abundant channels in MOFs ensure fast reaction kinetics and high intrinsic activities throughout ion migration during the charge–discharge process. The cyclic stability of electrode materials in the batteries is affected by the size of hollow structures. In this state, a structural evolution occurs for the formation of hierarchical nanostructure with homogenous nanoparticles dispersion due to the sufficient space for volume expansion in these hollow structures, and it causes a proper cyclic stability for electrode material. Some studies showed an improvement in the conductivity of the composite in the presence of carbon materials. The high conductivity of the carbon materials facilitates ion and electron transport between the electrode and electrolyte, offering a good rate capability.

4. Summary and perspective

This review displayed the numerous possibilities of applying manganese- and vanadium-based MOFs-derived materials and their composites in energy applications in various processes such as electrochemical water splitting, supercapacitors and batteries. A broad range of vanadium oxidation states, impact on the acidity, and beneficial interactions with other MOFs' components entail numerous advantages for these materials as electrocatalysts and electrode materials. Properties such as regular structure, large specific surface area, high porosity, or many modification options are reasons for the great potential of Mn-MOFs and V-MOFs in the above-mentioned energy conversion and storage applications. Therefore, future research should focus on synthesizing novel Mn- and V-based MOFs electrode materials, improving the stability and performance of the already known materials, and further developing their applications. The conclusions below are potentially drawn considering the conditions mentioned:

From the industrial perspective, two important factors in the catalysts' mass distribution are the scale and cost of production. For example, catalysts used to generate large-scale hydrogen through electrochemical water splitting should be cost-effective and abundantly found on the earth while indicating high efficiency in addressing the slow OER kinetics. These characteristics are all found in catalysts containing vanadium and manganese-based MOFs, making them promising candidates for this area of research.

One of the main influencing factors on the performance of vanadium and manganese-based MOFs and their derivatives is the surface composition, making them considerably functional and stable, which are the required characteristics for HER/OER electro-catalysis.

The MOFs under study have certain structural characteristics such as large surface area, porous structure, and unique composition, all of which are passed to their derivatives during transformation. Accordingly, the formation of several active centers leads to the superiority of these compounds over their pristine type.

Little research has been conducted to theoretically study and model uninvestigated compounds, focusing on understanding the available functional data and predicting their performance. The use of DFT calculations seems to facilitate the prediction of the electronic structure of these MOFs and their derivatives, as a result of which more ideal surfaces can be designed for organic or electrochemical reactions.

It is possible to enhance the specific surface area, morphology, and structure of catalysts derived from these bimetallic MOFs using novel synthetic methods. There are different chemical as well as electrochemical procedures that can be used in addition to pyrolysis.

The applications of vanadium and manganese-based MOFs can be extended to various catalysis processes associated with energy generation and storage issues by functionalizing the surface and selecting suitable compositions.

It is also possible to design tri- and multi-metallic vanadium and manganese-based MOFs in addition to the bimetallic compounds, leading to multi-metallic oxides, sulfides, phosphides, and other composites that can even perform as more efficient catalysts.

If the crustal morphology is adequately controlled, it may be possible to use vanadium directly and manganese-based MOFs as HER/OER electro-catalysts, to which thin two-dimensional MOF nanosheets seem to have a special contribution.

Although there have been significant developments in designing and synthesizing vanadium and manganese-based MOFs, research in both academic and industrial areas has been challenging so far, some instances of which are as follows.

Poor conductivity, failure to absorb visible light, and broader bans gaps are among the main shortcomings of many vanadium and manganese-based MOFs in photo- and electro-catalysis.

Various characterization techniques are required to highlight the charge transfer process and improve the catalytic and photo(electro)catalytic activities in the mentioned MOFs.

The logical and accurate design of such catalysts with several active sites and optimum stability for application in various industries is only possible through in-depth research.

Few studies have investigated the reaction mechanisms and surface and composition adaptation to individual half-reactions. In situ/operando methods can be combined with computational calculations to shed light on the origin of enhanced performance while providing descriptors and indications to the design of novel generations of advanced materials, particularly vanadium and manganese-based MOFs possessing various metal centers.

Despite the continuous preparation of MOFs, their applications face several obstacles, one of which is the considerably high costs of preparing these materials and their derivatives. Besides, high-temperature pyrolysis (HTP) can be considered as an essential step, making the process more energy-dependent. Hence, the current research focuses on developing low-energy production processes and cost reduction. For instance, HTP may be enhanced by solar energy, while the potential of novel highly efficient activators and self-activation systems should also be investigated.

Another attractive research area is the combination of the mentioned MOFs in this study with various single or mixed catalysts. Investigations can be carried out on different procedures and methodologies to prepare such MOFs, the results and impacts of which can then be deliberated.

Although the MOFs under study have applications as active compounds in various catalytic processes to produce energy, most of these compounds cannot compete with commercial catalysts. Therefore, their performance improvement is sought through extensive studies on various obstacles for improving the performance and mechanism associated with these compounds.

The MOFs investigated in this study have broad applications in many catalytic processes. Still, few studies have focused on several important practical areas, including photo-electro-catalysis, reducing inorganic and organic compounds. Hence, it is hoped that the results summarized in the present study can also enhance other fields.

Using different MOFs and their derivatives can have inevitable environmental consequences, necessitating their recovery and efficient reuse to ensure their optimum green cycle path. One of the main ways these compounds can be recovered is to magnetize vanadium and manganese-based MOFs, particularly aimed at protecting the environment. Besides, another significant challenge is to obtain the efficient recovery of the mentioned compounds as electrode materials and restore them effectively from the environment. It is noteworthy that simple treatment methods like pyrolysis may reuse such materials.

While several studies have reported the synthesis of electro-catalysts that contain first-row transition metals as derivatives of bimetallic MOFs, few studies have investigated vanadium and manganese-based bimetallic MOFs and their applications in high-power electrolysis. As shown by the present study, few studies have concentrated on the effects of production scale-up on the catalyst performance. One of the critical issues is to examine the techno-economic feasibility of producing the MOFs mentioned above and their derivatives on a large scale because the enhanced performance of such catalysts has been proven, on the one hand, and water electrolysis is of great importance in the future decarbonized energy.

Hence, although there has been much development in this area, further studies are required to ensure the commercialization of the mentioned bimetallic MOFs and their derivatives. The design of these materials facilitates a deeper insight into their behavioral and functional characteristics. In this regard, researchers have significantly contributed to the screening and designing of advanced catalysts based on first-row transition metals, including those investigated to achieve more practical properties. Overall, such compounds can be valuable candidates as excellent catalysts, leading to compatible, simple, and green energy and environmental applications, which are particularly ensured by continuous research in this field.

Conflicts of interest

There are no conflicts to declare.

Acknowledgements

This work was supported by the University of Maragheh, Iran’s National Elites Foundation and Iran National Science Foundation (project number: 4025427). The authors are grateful for the financial support.

Notes and references

1. J. Huang, Y. Xie, Y. You, J. Yuan, Q. Xu, H. Xie and Y. Chen, Adv. Funct. Mater., 2023, 33, 2213095.
2. Y. Hong, Z. Ma, K. Li, J. Li, S. Tang, Z. Xu, D. Yu, D. Chen, L. Qin, J. Xie and Q. He, J. Mater. Chem. A, 2023, 11, 7898.
3. S. Wang, Y. Zhang, X. Deng, Z. Ma, R. Cheng, Z. Wan, J. Li and X. Wang, J. Mater. Chem. A, 2023, 11, 5222.
4. R. Abazari, S. Sanati, A. Morsali, A. M. Kirillov, A. M. Z. Slawin and C. L. Carpenter-Warren, Inorg. Chem., 2021, 60, 2056–2067.
5. R. Karthik, R. Sukanya, S. M. Chen, M. Hasan, G. Dhakal, P. Muhammed Shafi and J.-J. Shim, ACS Appl. Mater. Interfaces, 2023, 15, 11927.
6. D. S. Dalavi, R. S. Desai and P. S. Patil, J. Mater. Chem. A, 2022, 10, 1179.
7. S. Sanati, R. Abazari, J. Albero, A. Morsali, H. García, Z. Liang and R. Zou, Angew. Chem., Int. Ed., 2021, 60, 11048.
8. J. Gao, and R. Abazari, Advanced Catalysts Based on Metal-Organic Frameworks, Part 1, Bentham: UAE, 1st edn, 2023.
9. Y. Peng, S. Sanati, A. Morsali and H. Garcia, Angew. Chem., Int. Ed., 2023, 62, e202214707.
10. S. Sanati, A. Morsali and H. García, J. Energy Chem., 2023, 87, 540–567.
11. A. Das, S. Bej, N. R. Pandit, P. Banerjee and B. Biswas, J. Mater. Chem. A, 2023, 11, 6090.
12. Y. Pan, S. Sanati, M. Nadafan, R. Abazari, J. Gao and A. M. Kirillov, Inorg. Chem., 2022, 61, 18873.
13. J. Wang, R. Abazari, S. Sanati, A. Ejsmont, J. Goscianska, Y. Zhou and D. P. Dubal, Small, 2023, 19, 2300673.
14. S. Yuan, L. Zou, J.-S. Qin, J. Li, L. Huang, L. Feng, X. Wang, M. Bosch, A. Alsalme and T. Cagin, Nat. Commun., 2017, 8, 15356.
15. L. Zhong, J. Qian, N. Wang, S. Komarneni and W. Hu, J. Mater. Chem. A, 2023, 11, 20423.
16. T. Kalhorizadeh, B. Dahrazma, R. Zarghami, S. Mirzababaei, A. M. Kirillov and R. Abazari, New J. Chem., 2022, 46, 9440–9450.
17. R. Abazari, F. Ataei, A. Morsali, A. M. Z. Slawin and C. L. Carpenter-Warren, ACS Appl. Mater. Interfaces, 2019, 11, 45442–45454.
18. B. Zhu, R. Zou and Q. Xu, Adv. Energy Mater., 2018, 8, 1801193.
19. Z. Chen, K. O. Kirlikovali, P. Li and O. K. Farha, Acc. Chem. Res., 2022, 55, 579.
20. W. Fan, X. Wang, B. Xu, Y. Wang, D. Liu, M. Zhang, Y. Shang, F. Dai, L. Zhang and D. Sun, J. Mater. Chem. A, 2018, 6, 24486–24495.
21. S. El Hankari, M. Bousmina and A. El Kadib, Prog. Mater. Sci., 2019, 106, 100579.
22. R. E. Sikma, K. P. Balto, J. S. Figueroa and S. M. Cohen, Angew. Chem., 2022, 134, e202206353.
23. S. Furukawa, J. Reboul, S. Diring, K. Sumida and S. Kitagawa, Chem. Soc. Rev., 2014, 43, 5700.
24. S. Kaushal, G. Kaur, J. Kaur and P. P. Singh, Mater. Adv., 2021, 2, 7308.
25. M. G. Jafari, D. Fehn, A. Reinholdt, C. Hernández-Prieto, P. Patel, M. R. Gau, P. J. Carroll, J. Krzystek, C. Liu, A. Ozarowski, J. Telser, M. Delferro, K. Meyer and D. J. Mindiola, J. Am. Chem. Soc., 2022, 144, 10201.
26. R. Basse, S. Vanicek, T. Höfer, H. Kopacka, K. Wurst, T. Müller, H. A. Schwartz, S. Olthof, L. A. Casper, M. Nau, R. F. Winter, M. Podewitz and B. Bildstein, Organometallics, 2021, 40, 2736.
27. J. Guo, J. Liu, W. Ma, Z. Sang, L. Yin, X. Zhang, H. Chen, J. Liang and D. Yang, Adv. Funct. Mater., 2023, 33, 2302659.
28. J. Zhang, Y. Liu, T. Wang, N. Fu and Z. Yang, J. Energy Storage, 2024, 76, 109873.
29. C. -F. Li, L. -J. Xie, J. -W. Zhao, L. -F. Gu, H. -B. Tang, L. Zheng and G. -R. Li, Angew. Chem., Int. Ed., 2022, 61, e202116934.
30. T. Li, Y. Bai, Y. Wang, H. Xu and H. Jin, Coord. Chem. Rev., 2020, 410, 213221.
31. Y. Pan, S. Sanati, R. Abazari, V. Navvar Noveiri, J. Gao and A. M. Kirillov, Inorg. Chem., 2022, 61, 20913.
32. W. Kaveevivitchai and A. J. Jacobson, J. Power Sources, 2015, 278, 265.
33. A. Centrone, T. Harada, S. Speakman and T. A. Hatton, Small, 2010, 6, 1598.
34. N. D. McNamara, G. T. Neumann, E. T. Masko, J. A. Urban and J. C. Hicks, J. Catal., 2013, 305, 217.
35. A. Phan, A. U. Czaja, F. Gándara, C. B. Knobler and O. M. Yaghi, Inorg. Chem., 2011, 50, 7388.
36. Y. Liu, X. Zhou, Z. Jia, H. Wu and G. Wu, Adv. Funct. Mater., 2022, 32, 2204499.
37. R. Du, Y. Du, X. Liu, Z. Fan and X. Wu, J. Environ. Chem. Eng., 2022, 10, 108028.
38. N. Yu, M. Li, X. Chen, L. Xu, W. Wang, F. Wei, Y. Sui, Q. Yan and S. Wang, ACS Appl. Energy Mater., 2023, 23, 12043–12051.
39. K. Barthelet, J. Marrot, D. Riou and G. Ferey, Angew. Chem., Int. Ed., 2002, 41, 281.
40. Y. Pan, R. Abazari, B. Tahir, S. Sanati, Y. Zheng, M. Tahir and J. Gao, Coord. Chem. Rev., 2024, 499, 215538.
41. S. Sanati, A. Morsali and H. García, Int. J. Hydrogen Energy, 2023, 48, 14749–14762.
42. R. Abazari, A. R. Amani-Ghadim, A. M. Z. Slawin, C. L. Carpenter-Warren and A. M. Kirillov, Inorg. Chem., 2022, 61, 9514.
43. S. Chongdar, S. Bhattacharjee, P. Bhanja and A. Bhaumik, Chem. Commun., 2022, 58, 3429.
44. T. C. Wang, N. A. Vermeulen, I. S. Kim, A. B. F. Martinson, J. F. Stoddart, J. T. Hupp and O. K. Farha, Nat. Protoc., 2016, 11, 149.
45. M. Shi, C. Peng and X. Zhang, Small, 2023, 19, 2301449.
46. H. Zhong, S. Chen, Z. Jiang, J. Hu, J. Dong, L.-H. Chung, Q.-C. Lin, W. Ou, L. Yu and J. He, Small, 2023, 19, 2207266.
47. M. Kim, J. F. Cahill, Y. Su, K. A. Prather and S. M. Cohen, Chem. Sci., 2012, 3, 126.
48. H. Wang, Q. L. Zhu, R. Zou and Q. Xu, Chem, 2017, 2, 52.
49. I. Hussain, S. Iqbal, C. Lamiel, A. Alfantazi and K. Zhang, J. Mater. Chem. A, 2022, 10, 4475.
50. F. Wang, J. Cai, C. Yang, H. Luo, X. Li, H. Hou, G. Zou and D. Zhang, Small, 2023, 19, 2300510.
51. C. Lamiel, I. Hussain, H. Rabiee, O. R. Ogunsakin and K. Zhang, Coord. Chem. Rev., 2023, 480, 215030.
52. E. R. Kearns, R. Gillespie and D. M. D'Alessandro, J. Mater. Chem. A, 2021, 9, 27252.
53. G. Cai, P. Yan, L. Zhang, H.-C. Zhou and H.-L. Jiang, Chem. Rev., 2021, 121, 12278.
54. C. Liu, Q. Li, W. Kang, W. Lei, X. Wang, C. Lu and M. Naebe, J. Mater. Chem. A, 2022, 10, 10.
55. S. Sanati, A. Morsali and H. Garcia, Energy Environ. Sci., 2022, 15, 3119–3151.
56. Y. Zhou, R. Abazari, J. Chen, M. Tahir, A. Kumar, R. R. Ikreegeegh, E. Rani, H. Singh and A. M. Kirillov, Coord. Chem. Rev., 2022, 451, 214264.
57. H. Saini, E. Otyepkova, A. Schneemann, R. Zboril, M. Otyepka, R. A. Fischer and K. Jayaramulu, J. Mater. Chem. A, 2022, 10, 2751.
58. L. Liu, S. Wu, D. Li, Y. Li, H. Zhang, L. Li, S. Jin and Z. Yao, ACS Appl. Mater. Interfaces, 2022, 14, 36882.
59. M. Ma, X. Lu, Y. Guo, L. Wang and X. Liang, TrAC, Trends Anal. Chem., 2022, 157, 116741.
60. S.-M. Wang, X.-T. Mu, H.-R. Liu, S.-T. Zheng and Q.-Y. Yang, Angew. Chem., Int. Ed., 2022, 134, e202207066.
61. S. K. Yadav, G. K. Grandhi, D. P. Dubal, J. C. de Mello, M. Otyepka, R. Zbořil, R. A. Fischer and K. Jayaramulu, Small, 2020, 16, 2004891.
62. R. Abazari, S. Sanati, M. A. Bajaber, M. S. Javed, P. C. Junk, A. K. Nanjundan, J. Qian and D. P. Dubal, Small, 2024, 20, 2306353.
63. T. D. Villenoisy, X. Zheng, V. Wong, S. S. Mofarah, H. Arandiyan, Y. Yamauchi, P. Koshy and C. C. Sorrell, Adv. Mater., 2023, 35, 2370174.
64. H. Saini, N. Srinivasan, V. Sedajova, M. Majumder, D. P. Dubal, M. Otyepka, R. Zboril, N. Kurra, R. A. Fischer and K. Jayaramulu, ACS Nano, 2021, 12, 18742.
65. K. Wang, Y. Li, L.-H. Xie, X. Li and J.-R. Li, Chem. Soc. Rev., 2022, 51, 6417.
66. Y. Feng and J. Yao, Coord. Chem. Rev., 2022, 470, 214699.
67. S. Ko, F. Gao, X. Yao, H. Yi, X. Tang, C. Wang, H. Liu, N. Luo and Z. Qi, New J. Chem., 2022, 46, 15758.
68. M. Sun, R. Abazari, J. Chen, C. M. Hussain, Y. Zhou and A. M. Kirillov, ACS Appl. Mater. Interfaces, 2023, 15, 52581–52592.
69. Y. Pan, R. Abazari, Y. Wu, J. Gao and Q. Zhang, Electrochem. Commun., 2021, 126, 107024.
70. Y. Peng, S. sanati, A. Morsali and H. Garcia, Angew. Chem., Int. Ed., 2023, 62, e202214707.
71. R. Abazari, S. Sanati, P. Stelmachowski, Q. Wang, A. Krawczuk, J. Goscianska and M. Liu, Inorg. Chem., 2024, 63, 5642–5651.
72. R. Abazari, S. Sanati, N. Li and J. Qian, Inorg. Chem., 2023, 62, 18680–18688.
73. Y. Hu, R. Abazari, S. Sanati, M. Nadafan, C. L. Carpenter-Warren, A. M. Z. Slawin, Y. Zhou and A. M. Kirillov, ACS Appl. Mater. Interfaces, 2023, 15, 37300–37311.
74. W. He, D. Lv, Y. Guan and S. Yu, J. Mater. Chem. A, 2023, 11, 24519.
75. P. Rassu, X. Ma and B. Wang, Coord. Chem. Rev., 2022, 465, 214561.
76. A. Zhou, Y. Dou, J. Zhou and J. -R. Li, ChemSusChem, 2020, 13, 205.
77. P. Li and H. C. Zeng, ACS Appl. Mater. Interfaces, 2016, 8, 29551.
78. Z. Zhai, W. Yan, L. Dong, S. Deng, D. P. Wilkinson, X. Wang, L. Zhang and J. Zhang, J. Mater. Chem. A, 2021, 9, 20320.
79. W. Xu, Y. Wu, W. Gu, D. Du, Y. Lin and C. Zhu, Chem. Soc. Rev., 2024, 53, 137.
80. G.-R. Xu, Z.-H. An, K. Xu, Q. Liu, R. Das and H.-L. Zhao, Coord. Chem. Rev., 2021, 427, 213554.
81. Y. Zhang, J. Wu, S. Zhang, N. Shang, X. Zhao, S. M. Alshehri, T. Ahamad, Y. Yamauchi, X. Xu and Y. Bando, Nano Energy, 2022, 97, 107146.
82. M. H. Yap, K. L. Fow and G. Z. Chen, Green Energy Environ., 2017, 2, 218.
83. R. Abazari and A. R. Mahjoub, Ultrason. Sonochem., 2018, 42, 577.
84. N. Campagnol, E. R. Souza, D. E. De Vos, K. Binnemans and J. Fransaer, Chem. Commun., 2014, 50, 12545.
85. R. Abazari, G. Salehi and A. R. Mahjoub, Ultrason. Sonochem., 2018, 46, 59.
86. Y. Thi Dang, H. T. Hoang, H. C. Dong, K. B. T. Bui, L. H. T. Nguyen, T. B. Phan, Y. Kawazoe and T. L. H. Doan, Microporous Mesoporous Mater., 2020, 298, 110064.
87. M. Rubio-Martinez, C. Avci-Camur, A. W. Thornton, I. Imaz, D. Maspoch and M. R. Hill, Chem. Soc. Rev., 2017, 46, 3453.
88. B. Ma, T. T. Chen, Q. Y. Li, H. N. Qin, X. Y. Dong and S. Q. Zang, ACS Appl. Energy Mater., 2019, 2, 1134.
89. J. Cai, Y. Chen, H. Song, L. Hou and Z. Li, Carbon, 2020, 160, 64.
90. F. Ghafarifar, S. Molaie, R. Abazari, Z.-M. Hasan and M. Foroutan, Iran. J. Parasitol., 2020, 15, 537.
91. N. A. Khan and S. H. Jhung, Coord. Chem. Rev., 2015, 285, 11.
92. K. A. Adegoke and N. W. Maxakato, Mater. Today Energy, 2021, 21, 100816.
93. Z. Song, L. Zhang, M. Zheng and X. Sun, in Layer. Mater. Energy Storage Convers., The Royal Society of Chemistry, 2019, ch. 1, pp. 1–38.
94. H. Bin Wu and X. W. Lou, Sci. Adv., 2017, 3, 1.
95. X. Cao, C. Tan, M. Sindoro and H. Zhang, Chem. Soc. Rev., 2017, 46, 2660.
96. J. Liu, D. D. Zhu, C. X. Guo, A. Vasileff and S. Z. Qiao, Adv. Energy Mater., 2017, 7, 1700518.
97. S. Yuan, L. Feng, K. Wang, J. Pang, M. Bosch, C. Lollar, Y. Sun, J. Qin, X. Yang, P. Zhang, Q. Wang, L. Zou, Y. Zhang, L. Zhang, Y. Fang, J. Li and H.-C. Zhou, Adv. Mater., 2018, 30, 1704303.
98. M. Ding, X. Cai and H.-L. Jiang, Chem. Sci., 2019, 10, 10209–10230.
99. M. E. A. Safy, M. Amin, R. R. Haikal, B. Elshazly, J. Wang, Y. Wang, C. Woll and M. H. Alkordi, Chem. - Eur. J., 2020, 26, 7109–7117.
100. T. Hashem, E. P. V. Sanchez, P. G. Weidler, H. Gliemann, M. H. Alkordi and C. Woll, ChemistryOpen, 2020, 9, 524–527.
101. J. Chen, R. Abazari, K. A. Adegoke, N. W. Maxakato, O. S. Bello, M. Tahir, S. Tasleem, S. Sanati, A. M. Kirillov and Y. Zhou, Coord. Chem. Rev., 2022, 469, 214664.
102. X. Luo, R. Abazari, M. Tahir, W. K. Fan, A. Kumar, T. Kalhorizadeh, A. M. Kirillov, A. R. Amani-Ghadim, J. Chen and Y. Zhou, Coord. Chem. Rev., 2022, 461, 214505.
103. X. Li, X. Yang, H. Xue, H. Pang and Q. Xu, EnergyChem, 2020, 2, 100027.
104. S. Sanati, Q. Wang, R. Abazari and M. Liu, Chem. Commun., 2024, 60, 3129–3137.
105. R. Abazari, S. Sanati and A. Morsali, Inorg. Chem., 2022, 61, 3396–3405.
106. Q. Wang, Y. Gong, Y. Tan, X. Zi, R. Abazari, H. Li, C. Cai, K. Liu, J. Fu, S. Chen, T. Luo, S. Zhang, W. Li, Y. Sheng, J. Liu and M. Liu, Chin. J. Catal., 2023, 54, 229–237.
107. S. Sanati, R. Abazari and A. Morsali, Chem. Commun., 2020, 56, 6652–6655.
108. J. Yu, Q. Cao, Y. Li, X. Long, S. Yang, J. K. Clark, M. Nakabayashi, N. Shibata and J.-J. Delaunay, ACS Catal., 2019, 9, 1605.
109. Y. Wu, J. Liu, Q. Sun, J. Chen, X. Zhu, R. Abazari and J. Qian, Chem. Eng. J., 2024, 483, 149243.
110. C. Li and J.-B. Baek, ACS Omega, 2020, 5, 31.
111. S. -M. Ji, A. Muthurasu and H. Y. Kim, Chem. - Eur. J., 2023, 29, e202300137.
112. S. Xu, M. Li, H. Wang, Y. Sun, W. Liu, J. Duan and S. Chen, J. Phys. Chem. C, 2022, 126, 14094.
113. H. B. Aiyappa, J. Massa, C. Andronescu, M. Muhler, R. A. Fischer and W. Schuhmann, Small Methods, 2019, 3, 1800415.
114. P. Sadhukhan, S.-Q. Wu, S. Kanegawa, S.-Q. Su, X. Zhang, T. Nakanishi, J. I. Long, K. Gao, R. Shimada, H. Okajima, A. Sakamoto, J. G. Chiappella, M. S. Huzan, T. Kroll, D. Sokaras, M. L. Baker and O. Sato, Nat. Commun., 2023, 14, 3394.
115. Z. Wang, A. Roffey, R. Losantos, A. Lennartson, M. Jevric, A. U. Petersen, M. Quant, A. Dreos, X. Wen, D. Sampedro, K. Börjesson and K. Moth-Poulsen, Energy Environ. Sci., 2019, 12, 187–193.
116. M. Watanabe, M. L. Thomas, S. Zhang, K. Ueno, T. Yasuda and K. Dokko, Chem. Rev., 2017, 117, 7190–7239.
117. S. Khan, N. Ullah, A. Mahmood, M. Saad, Z. Ullah, W. Ahmad and S. Ullah, Energy Technol., 2023, 11, 2201416.
118. D. Kong, Y. Gao, Z. Xiao, X. Xu, X. Li and L. Zhi, Adv. Mater., 2019, 31, 1804973.
119. D. Chen, M. Lu, D. Cai, H. Yang and W. Han, J. Energy Chem., 2021, 54, 712–726.
120. F. Wan and Z. Niu, Angew. Chem., Int. Ed., 2019, 58, 16358.
121. P. Liu, K. Zhu, Y. Gao, H. Luo and L. Lu, Adv. Energy Mater., 2017, 7, 1700547.
122. C. Wu and Y. Xie, Energy Environ. Sci., 2010, 3, 1191.
123. M. Liu, B. Su, Y. Tang, X. Jiang and A. Yu, Adv. Energy Mater., 2017, 7, 1700885.
124. P. V. D. Voort, K. Leus, Y.-Y. Liu, M. Vandichel, V. V. Speybroeck, M. Waroquier and S. Biswas, New J. Chem., 2014, 38, 1853.
125. X. Li, X. Yang, H. Xue, H. Pang and Q. Xu, EnergyChem, 2020, 2, 100027.
126. H. Xu, J. Wei, K. Zhang, M. Zhang, C. Liu, J. Guo and Y. Du, J. Mater. Chem. A, 2018, 6, 22697.
127. H.-J. Pan, G. Huang, M.-D. Wodrich, F. F. Tirani, K. Ataka, S. Shima and X. Hu, Nat. Chem., 2019, 11, 669.
128. W. Zhou, Z. Xue, Q. Liu, Y. Li, J. Hu and G. Li, ChemSusChem, 2020, 13, 5647.
129. D. S. Raja, X.-F. Chuah and S.-Y. Lu, Adv. Energy Mater., 2018, 8, 1801065.
130. W. Wang, X. Xu, W. Zhou and Z. Shao, Adv. Sci., 2017, 4, 1600371.
131. K. Rui, G. Zhao, Y. Chen, Y. Lin, Q. Zhou, J. Chen, J. Zhu, W. Sun, W. Huang and S. X. Dou, Adv. Funct. Mater., 2018, 28, 1801554.
132. L. Han, J. Xu, Y. Huang, W. Dong and X. Jia, Chin. Chem. Lett., 2021, 32, 2263.
133. M. Hasanzadeh, N. Shadjou, L. Saghatforoush, R. Mehdizadeh and S. Sanati, Catal. Commun., 2012, 19, 10–16.
134. J. Jiang, F. Sun, S. Zhou, W. Hu, H. Zhang, J. Dong, Z. Jiang, J. Zhao, J. Li, W. Yan and M. Wang, Nat. Commun., 2018, 9, 2885.
135. R. Wei, X. Bu, W. Gao, R. A. B. Villaos, G. Macam, Z.-Q. Huang, C. Lan, F.-C. Chuang, Y. Qu and J. C. Ho, ACS Appl. Mater. Interfaces, 2019, 11, 33012.
136. T. Zhao, X. Shen, Y. Wang, R. K. Hocking, Y. Li, C. Rong, K. Dastafkan, Z. Su and C. Zhao, Adv. Funct. Mater., 2021, 31, 2100614.
137. P. Li, X. Duan, Y. Kuang, Y. Li, G. Zhang, W. Liu and X. Sun, Adv. Energy Mater., 2018, 8, 1703341.
138. Y. Kong, D. Xiong, C. Lu, J. Wang, T. Liu, S. Ying, X. Ma and F.-Y. Yi, ACS Appl. Mater. Interfaces, 2022, 14, 37804.
139. J. Lv, P. Liu, F. Yang, L. Xing, D. Wang, X. Chen, H. Gao, X. Huang, Y. Lu and G. Wang, ACS Appl. Mater. Interfaces, 2020, 12, 48495.
140. Y. Wang, B. Liu, X. Shen, H. Arandiyan, T. Zhao, Y. Li, M. Garbrecht, Z. Su, L. Han, A. Tricoli and C. Zhao, Adv. Energy Mater., 2021, 11, 2003759.
141. W. Zhou, D.-D. Huang, Y.-P. Wu, J. Zhao, T. Wu, J. Zhang, D.-S. Li, C. Sun, P. Feng and X. Bu, Angew. Chem., Int. Ed., 2019, 58, 4227.
142. H. Yu, L. Wang, H. Li, Z. Luo, T. T. Isimjan and X. Yang, Chem. - Eur. J., 2022, 28, e202201784.
143. Y.-J. Tang, H.-J. Zhu, L.-Z. Dong, A.-M. Zhang, S.-L. Li, J. Liu and Y.-Q. Lan, Appl. Catal., B, 2019, 245, 528.
144. W. H. Guo, Q. Zhang, X. H. Wang, Y. X. Yang, X. L. Li, L. J. Li, H. Q. Luo and N. B. Li, Electrochim. Acta, 2020, 357, 136850.
145. Y. Lin, G. Chen, H. Wan, F. Chen, X. Liu and R. Ma, Small, 2019, 15, e1900348.
146. W. Dong, H. Zhou, B. Mao, Z. Zhang, Y. Liu, Y. Liu, F. Li, D. Zhang and W. Shi, Int. J. Hydrogen Energy, 2021, 46, 10773.
147. Y. Ji, L. Huang, J. Hu, C. Streb and Y.-F. Song, Energy Environ. Sci., 2015, 8, 776.
148. Y. Ji, J. Hu, J. Biskupek, U. Kaiser, Y.-F. Song and C. Streb, Chem.–Eur. J., 2017, 23, 16637.
149. L. E. VanGelder, A. M. Kosswattaarachchi, P. L. Forrestel, T. R. Cook and E. M. Matson, Chem. Sci., 2018, 9, 1692.
150. Y. Ji, Y. Ma, R. Liu, Y. Ma, K. Cao, U. Kaiser, A. Varzi, Y.-F. Song, S. Passerini and C. Streb, J. Mater. Chem. A, 2019, 7, 13096.
151. H. Ji, S. Hwang, K. Kim, C. Kim and N. C. Jeong, ACS Appl. Mater. Interfaces, 2016, 8, 32414.
152. A. Goswami, D. Ghosh, D. Pradhan and K. Biradha, ACS Appl. Mater. Interfaces, 2022, 14, 29722.
153. W. Xu, H. Chen, K. Jie, Z. Yang, T. Li and S. Dai, Angew. Chem., Int. Ed., 2019, 58, 5018.
154. J. Duan, S. Chen and C. Zhao, Nat. Commun., 2017, 8, 15341.
155. X. Zhao, X. Li, Y. Yan, Y. Xing, S. Lu, L. Zhao, S. Zhou, Z. Peng and J. Zeng, Appl. Catal., B, 2018, 236, 569.
156. M. Zhang, W. Xu, T. Li, H. Zhu and Y. Zheng, Inorg. Chem., 2020, 59, 15467.
157. D.-J. Li, Q.-H. Li, Z.-G. Gu and J. Zhang, J. Mater. Chem. A, 2019, 7, 18519.
158. Z. Liang, C. Qu, D. Xia, R. Zou and Q. Xu, Angew. Chem., Int. Ed., 2018, 57, 9604.
159. W. Zhou, Z. Xue, Q. Liu, Y. Li, J. Hu and G. Li, ChemSusChem, 2020, 13, 5647.
160. J.-Q. Shen, P.-Q. Liao, D.-D. Zhou, C.-T. He, J.-X. Wu, W.-X. Zhang, J.-P. Zhang and X.-M. Chen, J. Am. Chem. Soc., 2017, 139, 1778.
161. F.-L. Li, Q. Shao, X. Huang and J.-P. Lang, Angew. Chem., 2018, 130, 1906.
162. H. Guan, N. Wang, X. Feng, S. Bian, W. Li, Y. Chen and A. Physicochem, Eng. Aspects, 2021, 624, 126596.
163. Y. Sun, S. Sun, H. Yang, S. Xi, J. Gracia and Z.-J. Xu, Adv. Mater., 2020, 32, 2003297.
164. G. Zhou, P. Wang, H. Li, B. Hu, Y. Sun, R. Huang and L. Liu, Nat. Commun., 2021, 12, 4827.
165. Z. Chen, X. Duan, W. Wei, S. Wang and B.-J. Ni, J. Mater. Chem. A, 2019, 7, 14971.
166. Q. Li, Z. Xing, D. Wang, X. Sun and X. Yang, ACS Catal., 2016, 6, 2797.
167. S. Shit, S. Chhetri, W. Jang, N. C. Murmu, H. Koo, P. Samanta and T. Kuila, ACS Appl. Mater. Interfaces, 2018, 10, 27712.
168. R. Zhang, Z. Yu, R. Jiang, J. Huang, Y. Hou, F. Yang, H. Zhu, B. Zhang, Y. Huang and B. Ye, Electrochim. Acta, 2021, 366, 137438.
169. X. Chen, W. Li, C. Gong, X. He, H. Chen, X. Du, W. Fang, L. Yang and L. Zhao, Int. J. Hydrogen Energy, 2021, 46, 38724.
170. J. Qi, H. Wang, J. Lin, C. Li, X. Si, J. Cao, Z. Zhong and J. Feng, J. Colloid Interface Sci., 2019, 557, 28.
171. C.-C. Hou and Q. Xu, Adv. Energy Mater., 2019, 9, 1801307.
172. A.-A. Lourenço, V. D. Silva, R. B. da Silva, U. C. Silva, C. Chesman, C. Salvador, T.-A. Simoes, D. A. Macedo and F. F. da Silva, J. Colloid Interface Sci., 2021, 582, 124.
173. Y. Li, B. Jia, B. Chen, Q. Liu, M. Cai, Z. Xue, Y. Fan, H. P. Wang, C. Y. Su and G. Li, Dalton Trans., 2018, 47, 14679.
174. D. Duan, J. Feng, D. Guo, J. Gao, S. Liu, Y. Wang and X. Zhou, Int. J. Hydrogen Energy, 2022, 47, 12927.
175. W. Cheng, X. F. Lu, D. Luan and X. W. (David) Lou, Angew. Chem., Int. Ed., 2020, 132, 18391.
176. S. Gonen, O. Lori, G. Cohen-Taguri and L. Elbaz, Nanoscale, 2018, 10, 9634.
177. S. Yao, Y. Jiao, C. Lv, Y. Kong, S. Ramakrishna and G. Chen, J. Colloid Interface Sci., 2022, 623, 1111.
178. R. B. Ghising, U. N. Pan, D. R. Paudel, M. R. Kandel, N. H. Kim and J. H. Lee, J. Mater. Chem. A, 2022, 10, 16457.
179. R. Abazari, S. Sanati, A. Morsali and D. P. Dubal, J. Mater. Chem. A, 2021, 9, 11001–11012.
180. R. Abazari, S. Sanati, A. Morsali, A. Slawin and C. L. Carpenter-Warren, ACS Appl. Mater. Interfaces, 2019, 11, 14759–14773.
181. M. Ghahremani, R. Behzadian, I. Aghayan, S. Barzegaribaghbidi and T. Kalhorizadeh, Int. J. Pavement Eng., 2023, 24, 2273318.
182. S. Sanati and Z. Rezvani, Chem. Eng. J., 2019, 362, 743–757.
183. R. Abazari, S. Sanati, A. Morsali, A. M. Z. Slawin, C. L. Carpenter-Warren, W. Chen and A. Zheng, J. Mater. Chem. A, 2019, 7, 11953–11966.
184. S. A. Thomas and J. Cherusseri, J. Mater. Chem. A, 2023, 11, 23148.
185. S. Sanati, R. Abazari, A. Morsali, A. M. Kirillov, P. C. Junk and J. Wang, Inorg. Chem., 2019, 58, 16100–16111.
186. T. Prasankumar, D. Salpekar, S. Bhattacharyya, K. Manoharan, R. M. Yadav, M. A. Kampos Mata, K. A. Miller, R. Vajtai, S. Jose, S. Roy and P. M. Ajayan, Carbon, 2022, 199, 249.
187. X. Shen, T. Wang, X. Wei and S. Li, ACS Appl. Energy Mater., 2022, 5, 2596.
188. B. Zhang, C. Zhang, W. Yuan, O. Yang, Y. Liu, L. He, Y. Hu, L. Zhou, J. Wang and Z. L. Wang, ACS Appl. Mater. Interfaces, 2022, 14, 9046.
189. Y. Wang, Y. Liu, H. Wang, W. Liu, Y. Li, J. Zhang, H. Hou and J. Yang, ACS Appl. Energy Mater., 2019, 2, 2063.
190. D. Sheberla, J. C. Bachman, J. S. Elias, C.-J. Sun, Y. Shao-Horn and M. Dinca, Nat. Mater., 2017, 16, 220.
191. Y. Yan, Y. Luo, J. Ma, B. Li, H. Xue and H. Pang, Small, 2018, 14, 1801815.
192. F. Farzinpour, A. A. Ensafi, K. Z. Mousaabadi and B. Rezaei, Fuel, 2023, 341, 127724.
193. M. Liu, Z. Li and Y. Zhang, J. Electrochem. Soc., 2023, 170, 110524.
194. I. Hussain, S. Sahoo, T. Hussain, M. Ahmad, M. S. Javed, C. Lamiel, S. Gu, T. Kaewmaraya, M. S. Sayed and K. Zhang, Adv. Funct. Mater., 2023, 33, 2210002.
195. E. Erçarıkcı, E. Topçua and K. D. Kıranşan, J. Mater. Chem. C, 2023, 11, 9593.
196. B. Gao, X. Li, K. Ding, C. Huang, Q. Li, P. K. Chu and K. Huo, J. Mater. Chem. A, 2019, 7, 14.
197. X. Lu, M. Yu, T. Zhai, G. Wang, S. Xie, T. Liu, C. Liang, Y. Tong and Y. Li, Nano Lett., 2013, 13, 2628.
198. O. Bondarchuk, A. Morel, D. Belanger, E. Goikolea, T. Brousse and R. Mysyk, J. Power Sources, 2016, 324, 439.
199. Y. Liu, L. Liu, L. Kang and F. Ran, J. Power Sources, 2020, 450, 227687.
200. Z. Wu, D. Khalafallah, C. Teng, X. Wang, Q. Zou, J. Chen, M. Zhi and Z. Hong, J. Alloys Compd., 2020, 838, 155604.
201. E. Niknam, H. Naffakh-Moosavy, S. E. Moosavifard and M. G. Afshar, J. Energy Storage, 2021, 44, 103508.
202. S. Lindberg, N. M. Ndiaye, N. Manyala, P. Johansson and A. Matic, Electrochim. Acta, 2020, 345, 136225.
203. H. Zhuang and F. Yang, Surf. Interfaces, 2021, 25, 101232.
204. G. K. Veerasubramani, A. Chandrasekhar, M. Sudhakaran, Y. S. Mok and S. J. Kim, J. Mater. Chem. A, 2017, 5, 11100.
205. S. Chandra Sekhar, B. Ramulu, D. Narsimulu, S. J. Arbaz and J. S. Yu, Small, 2020, 16, 2003983.
206. Y. Huang, M. Zhu, Z. Pei, Q. Xue, Y. Huang and C. Zhi, J. Mater. Chem. A, 2016, 4, 1290.
207. X. Liang, L. Zhao, Q. Wang, Y. Ma and D. Zhang, Nanoscale, 2018, 10, 22329.
208. Q. Guo, X. Zhao, Z. Li, B. Wang, D. Wang and G. Nie, ACS Appl. Energy Mater., 2020, 3, 2727.
209. Y. Zhong, Z. Chai, Z. Liang, P. Sun, W. Xie, C. Zhao and W. Mai, ACS Appl. Mater. Interfaces, 2017, 9, 34085.
210. H. Liang, R. Li, C. Li, C. Hou, Y. Li, Q. Zhang and H. Wang, Mater. Horiz., 2019, 6, 571.
211. A. Dewan, R. Narayanan and M. O. Thotiyl, Nanoscale, 2022, 14, 17372.
212. J. Pu, Y. Gao, Q. Cao, G. Fu, X. Chen, Z. Pan and C. Guan, SmartMat, 2022, 3, 608.
213. P. A. Shinde, Y. Seo, S. Lee, H. Kim, Q. M. Pham, Y. Won and S. C. Jun, Chem. Eng. J., 2020, 387, 122982.
214. S. Maiti, A. Pramanik, U. Manju and S. Mahanty, ACS Appl. Mater. Interfaces, 2015, 7, 16357.
215. C. Zhong, Y. Deng, W. Hu, J. Qiao, L. Zhang and J. Zhang, Chem. Soc. Rev., 2015, 44, 7484.
216. S. Maiti, A. Pramanik and S. Mahanty, ACS Appl. Mater. Interfaces, 2014, 6, 10754.
217. S. Sundriyal, V. Shrivastav, M. Sharma, S. Mishra and A. Deep, ChemistrySelect, 2019, 4, 2585.
218. P. Simon and Y. Gogotsi, Nat. Mater., 2008, 7, 845.
219. W. Lu, Z. Yuan, C. Xu, J. Ning, Y. Zhong, Z. Zhang and Y. Hu, J. Mater. Chem., 2019, 7, 5333.
220. Y. Chen, R. Yang, C. Chen, Y. Li and M. Wei, J. Power Sources, 2021, 505, 230077.
221. Y. Yuan, J. Zhu, Y. Wang, S. Li, P. Jin and Y. Chen, J. Alloys Compd., 2020, 830, 154524.
222. K. Zhou, W. Zhou, L. Yang, J. Lu, S. Cheng, W. Mai, Z. Tang, L. Li and S. Chen, Adv. Funct. Mater., 2015, 25, 7530.
223. R. Manikandan, C. Justin Raj, A. D. Savariraj, P. Thondaiman, W.-J. Cho, H.-M. Jang and B. C. Kim, Electrochim. Acta, 2021, 393, 139060.
224. X. Liu, F. Zou, K. Liu, Z. Qiang, C. J. Taubert, P. Ustriyana, B. D. Vogt and Y. Zhu, J. Mater. Chem. A, 2017, 5, 11781.
225. H. Liu, H. Guo, W. Yao, L. Zhang, M. Wang, T. Fan, W. Yang and W. Yang, Colloids Surf., A, 2020, 601, 125011.
226. Y. Du, G. Li, M. Chen, X. Yang, L. Ye, X. Liu and L. Zhao, Chem. Eng. J., 2019, 378, 122210.
227. M. Chen, R. Abazari, S. Sanati, J. Chen, M. Sun, C. Bai, A. M. Kirillov, Y. Zhou and G. Hu, Carbon Energy, 2023, 5, e459.
228. G. Salehi, M. Bagherzadeh, R. Abazari, M. Hajilo and D. Taherinia, ACS Omega, 2024, 9, 4581–4593.
229. S. Sanati, Z. Rezvani and B. Habibi, New J. Chem., 2018, 42, 18426–18436.
230. S. Sanati and Z. Rezvani, J. Mol. Liq., 2018, 249, 318–325.
231. Z. Liu, C. Yu, X. Han, J. Yang, C. Zhao, H. Huang and J. Qiu, ChemElectroChem, 2016, 3, 906.
232. H. Maki, M. Inoue and M. Mizuhata, Electrochim. Acta, 2018, 270, 395.
233. C. Guan, W. Xiao, H. Wu, X. Liu, W. Zang, H. Zhang, J. Ding, Y. P. Feng, S. J. Pennycook and J. Wang, Nano Energy, 2018, 48, 73.
234. X. Liu, L. Zhang, X. Gao, C. Guan, Y. Hu and J. Wang, ACS Appl. Mater. Interfaces, 2019, 11, 23236.
235. W. Peng, N. Song, Z. Su, J. Wang, K. Chen, S. Li, B. Wei, S. Luo and A. Xie, Microchem. J., 2022, 179, 107506.
236. S. Yao, Y. Jiao, S. Sun, L. Wang, P. Li and G. Chen, ACS Sustainable Chem. Eng., 2020, 8, 3191.
237. Y. Han, J. Zhou, L. Wang, L. Xing, Z. Xue, Y. Jiao and Y. Pang, J. Electroanal. Chem., 2021, 882, 114993.
238. X. Liu, X. Zhang, R. Liu, C. Li, C. Xu, H. Ding, T. Xing, Z. Dai and X. Zhu, J. Nanopart. Res., 2021, 24, 23.
239. G. A. A. Saeed, P. Bandyopadhyay, S. M. Jeong, K. H. Kim and S. Lim, Mater. Today Chem., 2022, 23, 100758.
240. D. V. Lam, D. T. Dung, E. Roh, J. -H. Kim, H. Kim and S. -M. Lee, Adv. Mater. Interfaces, 2021, 8, 2101599.
241. J. Ren, Y. Huang, H. Zhu, S. Shen, G. Tan, F. Wu, H. He, S. Lan, X. Xia and Q. Liu, Carbon Energy, 2020, 2, 176.
242. M. Coduri, M. Karlsson and L. Malavasi, J. Mater. Chem. A, 2022, 10, 5082.
243. Y. He, Y. Qiao, Z. Chang and H. Zhou, Energy Environ. Sci., 2019, 12, 2327.
244. S. Mondal, P. Samanta, R. Sahoo, T. Kuila and M. C. Das, Chem. Eng. J., 2023, 470, 144340.
245. C. Gao, Z. Jiang, P. Wang, L. R. Jensen, Y. Zhang and Y. Yue, Nano Energy, 2020, 74, 104868.
246. W. Xi, J. Zhang, Y. Zhang, R. Wang, Y. Gong, B. He, H. Wang and J. Jin, J. Mater. Chem. A, 2023, 11, 7679.
247. W. Liu, H. Zong, M. Li, Z. Zeng, S. Gong, K. Yu and Z. Zhu, ACS Appl. Mater. Interfaces, 2023, 15, 13554.
248. X. Wang, D. Du, H. Xu, Y. Yan, X. Wen, L. Ren and C. Shu, Chem. Eng. J., 2023, 452, 139524.
249. L. Gong, Y. Zhang and Z. Li, Mater. Today Chem., 2022, 23, 100731.
250. C. B. Bucur, M. Jones, M. Kopylov, J. Spear and J. Muldoom, Energy Environ. Sci., 2017, 10, 905.
251. M. Du, P. Geng, C. Pei, X. Jiang, Y. Shan, W. Hu, L. Ni and H. Pang, Angew. Chem., Int. Ed., 2022, 61, e202209350.
252. Z. Wang, B. Wang, Y. Yang, Y. Cui, Z. Wang, B. Chen and G. Qian, ACS Appl. Mater. Interfaces, 2015, 7, 20999.
253. Z. Zhao, S. Wang, R. Liang, Z. Li, Z. Shi and G. Chen, J. Mater. Chem. A, 2014, 2, 13509.
254. J. Yang, B. Wang, F. Jin, Y. Ning, H. Luo, J. Zhang, F. Wang, D. Wang and Y. Zhou, Nanoscale, 2020, 12, 4552.
255. D. Chen, S. Mukherjee, C. Zhang, Y. Li, B. Xiao and C. V. Singh, J. Colloid Interface Sci., 2022, 613, 435.
256. W. Li, X. Guo, P. Geng, M. Du, Q. Jing, X. Chen, G. Zhang, H. Li, Q. Xu, P. Braunstein and H. Pang, Adv. Mater., 2021, 33, 2105163.
257. M. Song, H. Tan, D. Chao and H. J. Fan, Adv. Funct. Mater., 2018, 28, 1802564.
258. H. Pan, Y. Shao, P. Yan, Y. Cheng, K. S. Han, Z. Nie, C. Wang, J. Yang, X. Li, P. Bhattacharya, K. T. Mueller and J. Liu, Nat. Energy, 2016, 1, 16039.
259. G. Fang, J. Zhou, A. Pan and S. Liang, ACS Energy Lett., 2018, 3, 2480.
260. C. Yin, C. Pan, X. Liao, Y. Pan and L. Yuan, ACS Appl. Mater. Interfaces, 2021, 13, 35837.
261. S. Mondal, P. Samanta, R. Sahoo, T. Kuila and M. C. Das, Chem. Eng. J., 2023, 470, 144340.
262. V. Soundharrajan, B. Sambandam, S. Kim, M. H. Alfaruqi, D. Y. Putro, J. Jo, S. Kim, V. Mathew, Y.-K. Sun and J. Kim, Nano Lett., 2018, 18, 2402.
263. B. He, Q. Zhang, P. Man, Z. Zhou, C. Li, Q. Li, L. Xie, X. Wang, H. Pang and Y. Yao, Nano Energy, 2019, 64, 103935.
264. Y. Ding, Y. Peng, S. Chen, X. Zhang, Z. Li, L. Zhu, L. E. Mo and L. Hu, ACS Appl. Mater. Interfaces, 2019, 11, 44109.
265. Y. Ding, Y. Peng, W. Chen, Y. Niu, S. Wu, X. Zhang and L. Hu, Appl. Surf. Sci., 2019, 493, 368.
266. L. Gong, Y. Zhang and Z. Li, Mater. Today Chem., 2022, 23, 100731.
267. M. Liu, Z. Li and Y. Zhang, J. Electroanal. Chem., 2023, 942, 117576.
268. H. Xiaoshi, X. Lou, C. Li, Q. Yang, Q. Chen and B. Hu, ACS Appl. Mater. Interfaces, 2018, 10, 14684.
269. Y. Xia, Z. Xiao, X. Dou, H. Huang, X. Lu, R. Yan, Y. Gan, W. Zhu, J. Tu, W. Zhang and X. Tao, ACS Nano, 2013, 7, 7083.
270. R. Mehdizadeh, L. A. Saghatforoush and S. Sanati, Superlattices Microstruct., 2012, 52, 92–98.
271. F. Heshmatpour and R. Abazari, RSC Adv., 2014, 4, 55815–55826.
272. L. You, Y. Wen, G. Li, B. Chu, J. Wu, T. Huang and A. Yu, J. Mater. Chem. A, 2022, 10, 5631.
273. D. Xia, F. Gong, X. Pei, W. Wang, H. Li, W. Zeng, M. Wu and D. V. Papavassiliou, Chem. Eng. J., 2018, 348, 908.
274. W. Ren, D. Liu, C. Sun, X. Yao, J. Tan, C. Wang, K. Zhao, X. Wang, Q. Li and L. Mai, Small, 2018, 14, 1800659.
275. G. Huang, F. Zhang, L. Zhang, X. Du, J. Wang and L. Wang, J. Mater. Chem. A, 2014, 2, 8048.
276. F. Gong, D. Xia, C. Bi, J. Yang, W. Zeng, C. Chen, Y. Ding, Z. Xu, J. Liao and M. Wu, Electrochim. Acta, 2018, 264, 358.
277. G. Zhu, L. Wang, H. Lin, L. Ma, P. Zhao, Y. Hu, T. Chen, R. Chen, Y. Wang, Z. Tie, J. Liu and Z. Jin, Adv. Funct. Mater., 2018, 28, 1800003.
278. X. Kong, A. Pan, Y. Wang, D. Selvakumaran, J. Lin, X. Cao, S. Liang and G. Cao, J. Mater. Chem. A, 2018, 6, 12316.
279. Y. Guo, T. Feng, J. Yang, F. Gong, C. Chen, Z. Xu, C. Hu, S. Leng, J. Wang and M. Wu, Nanoscale, 2019, 11, 10763.
280. D. Sun, Y. Tang, D. Ye, J. Yan, H. Zhou and H. Wang, ACS Appl. Mater. Interfaces, 2017, 9, 5254.
281. X.-M. Tian, D.-L. Zhao, W.-J. Meng, X.-Y. Han, H.-X. Yang, Y.-J. Duan and M. Zhao, J. Alloys Compd., 2019, 792, 487.
282. J. L. Niu, G. X. Hao, J. Lin, X. Bin He, P. Sathishkumar, X. M. Lin and Y. P. Cai, Inorg. Chem., 2017, 56, 9966.
283. S. Chen, D. Cai, X. Yang, Q. Chen, H. Zhan, B. Qu and T. Wang, Electrochim. Acta, 2017, 256, 63.
284. X. Hu, Q. Huang, Y. Zhang, H. Zhong, Z. Lin, X. Lin, A. Zeb, C. Xu and X. Xu, Sustainable Energy Fuels, 2022, 6, 1175.
285. K. Z. Cao, L. F. Jiao, H. Xu, H. Q. Liu, H. Y. Kang, Y. Zhao, Y. C. Liu, Y. J. Wang and H. T. Yuan, Adv. Sci., 2015, 3, 1500185.
286. C. Yuan, H. B. Wu, Y. Xie and X. W. Lou, Angew. Chem., Int. Ed., 2014, 53, 1488.
287. H. Li, X. Liu, T. Zhai, D. Li and H. Zhou, Adv. Energy Mater., 2013, 3, 428.
288. A. Banerjee, U. Singh, V. Aravindan, M. Srinivasan and S. Ogale, Nano Energy, 2013, 2, 1158.
289. V. Soundharrajan, B. Sambandam, J. Song, S. Kim, J. Jo, S. Kim, S. Lee, V. Mathew and J. Kim, ACS Appl. Mater. Interfaces, 2016, 8, 8546.
290. H. Hu, X. Lou, C. Li, X. Hu, T. Li, Q. Chen, M. Shen and B. Hu, New J. Chem., 2016, 40, 9746.
291. Y. Fang, Y. Chen, L. Zeng, T. Yang, Q. Xu, Y. Wang, S. Zeng, Q. Qian, M. Wei and Q. Chen, J. Colloid Interface Sci., 2021, 593, 251.
292. D. Lin and Y. Li, Adv. Mater., 2022, 34, 2108856.
293. D. J. Kim, Y. H. Jung, K. K. Bharathi, S. H. Je, D. K. Kim, A. Koskun and J. w. Choi, Adv. Energy Mater., 2014, 4, 1400133.
294. Y. You, X.-L. Wu, Y.-X. Yin and Y.-G. Guo, Energy Environ. Sci., 2014, 7, 1643.
295. J.-H. Lee, G. Ali, D. H. Kim and K. Y. Chung, Adv. Energy Mater., 2017, 7, 1601491.
296. P. G. Bruce, S. A. Freunberger, L. J. Hardwick and J.-M. Tarascon, Nat. Mater., 2011, 11, 19.
297. S. H. Kim, Y. J. Lee, D. H. Kim and Y. J. Lee, ACS Appl. Mater. Interfaces, 2018, 10, 660.
298. D. Wu, Z. Guo, X. Yin, Q. Pang, B. Tu, L. Zhang, Y.-G. Wang and Q. Li, Adv. Mater., 2014, 26, 3258.
299. T. P. Senftle and E. A. Carter, Acc. Chem. Res., 2017, 50, 472.
300. M. Ding and H.-L. Jiang, ACS Catal., 2018, 8, 3194.
301. H. Lv, X. L. Huang, X. Zhu and B. Wang, J. Mater. Chem. A, 2022, 10, 25406.
302. S. Li, Y. Liu, J. Zhou, S. Hong, Y. Dong, J. Wang, X. Gao, P. Qi, Y. Han and B. Wang, Energy Environ. Sci., 2019, 12, 1046.

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