Tailoring photocatalytic activity in porphyrin-MOFs: the role of amino-functionalized pillars in CO₂ adsorption and band structure modulation

Abstract

The urgent need for sustainable carbon capture and conversion technologies has driven the development of advanced photocatalytic materials. Cobalt-porphyrin metal–organic frameworks (MOFs), engineered with tailored pore sizes, Lewis-basic functional groups, and optimized catalytic site densities, exhibit enhanced CO₂ adsorption capacity while facilitating efficient light harvesting and charge separation. Herein, we report two cobalt-based pillared-layer porphyrinic MOFs (TCPP-Pyz-Co and TCPP-NH₂Pyz-Co) designed for efficient CO₂ photoreduction. By incorporating amino-functionalized pillars, TCPP-NH₂Pyz-Co demonstrates a high CO₂ adsorption capacity of 82.8 cm³ g⁻¹ at 273 K. Furthermore, the introduced NH₂ groups narrow the bandgap and improve charge separation efficiency. As a result, TCPP-NH₂Pyz-Co achieves a remarkable CO production rate of 2221.4 μmol g⁻¹ h⁻¹, surpassing that of TCPP-Pyz-Co (1807.6 μmol g⁻¹ h⁻¹). Density functional theory (DFT) calculations reveal that the Co–Co paddlewheel nodes serve as the primary CO₂ adsorption sites, while the –COO group acts as an H₂O adsorption site. The amino functionality synergistically enhances CO₂ adsorption affinity due to the secondary sites in a position near to the primary CO₂ adsorption sites. This work underscores the pivotal role of Lewis-base functionalization in optimizing MOFs for dual CO₂ capture and conversion, providing a blueprint for next-generation photocatalysts.

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Zihao Xing

Dr Zi-Hao Xing is an Associate Professor at Northeast Normal University. He was recognized as the Young Talent Lift Project in Jilin Province. Dr Xing graduated with a bachelor's degree in applied chemistry from Jilin University in 2013 and a PhD in Physical Chemistry in 2019. He conducted postdoctoral research at Shenzhen University from September 2019 to May 2022 and was a visiting scholar at Ilmenau University of Technology in Germany in 2020. His research focuses on the design and controlled synthesis of low-cost non-precious metal electrocatalysts for fuel cells; dynamic restructuring and catalytic mechanisms during electrocatalysis; and the photocatalytic performance of advanced materials such as MOFs and COFs. He has published over 30 papers in journals including J. Am. Chem. Soc., Angew. Chem. Int. Ed., Adv. Mater., Adv. Energy Mater.

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Introduction

The increasing atmospheric concentration of carbon dioxide (CO₂), a major greenhouse gas, poses a severe threat to global climate stability, necessitating the urgent development of sustainable and efficient carbon capture and conversion technologies.^1–5 Among the various strategies under investigation, the photocatalytic CO₂ reduction reaction (CO₂RR), which utilizes solar energy to convert CO₂ into value-added fuels and chemicals, has emerged as a promising approach toward a circular carbon economy.^6–10

The design of novel photocatalytic materials with enhanced performance and selectivity remains a crucial challenge.^11–13 Porphyrins, inspired by their central role in natural photosynthesis, exhibit strong visible-light absorption, long-lived excited states, and tunable redox potentials, making them ideal candidates for light-harvesting and catalytic applications.^14–18 Despite their potential, homogeneous porphyrin-based photocatalysts often suffer from aggregation, photobleaching, and difficulties in separation and recycling.^19–22 Porphyrin-MOFs, which integrate porphyrin units as organic linkers within a rigid framework, overcome these limitations by providing a stable and ordered environment that enhances light absorption, CO₂ diffusion, and catalytic efficiency.

In porphyrin-MOFs, the catalytic activity of cobalt centers can be finely tuned by the surrounding porphyrin ligands and the MOF architecture. The π-d orbital overlaps between porphyrin units and metal clusters facilitate electron transfer ability and suppress charge recombination, thereby improving CO₂RR activity.^23–25 To further enhance CO₂ conversion efficiency, it is essential to integrate Lewis-basic functional groups, which improve CO₂ adsorption with photocatalytic active sites during MOF construction.^26–30 Pillared-layer porphyrin-MOFs offer a versatile platform for such modifications, as their porosity and electronic band structure can be systematically tuned by incorporating Lewis-basic pillar ligands.^31–35 Thus, the rational design of cobalt-porphyrin MOFs with tailored pore environments, functional groups, and catalytic site densities is crucial for optimizing CO₂ adsorption, light harvesting, and charge separation, which are key factors in advancing heterogeneous CO₂ photocatalysts.

In this work, we synthesized two pillared-layer porphyrinic MOFs (TCPP-Pyz-Co and TCPP-NH₂Pyz-Co) by linking porphyrin carboxylic acid ligands with paddlewheel Co₂(COO⁻)₄ clusters to form two-dimensional layers, bridged by pyrazine (Pyz) and aminopyrazine (NH₂Pyz) pillars. The introduction of Lewis-basic NH₂ groups modulates the pore environment and electronic band structure of the MOF. Compared to the non-functionalized analogue, TCPP-NH₂Pyz-Co exhibits a 20% increase in CO₂ uptake capacity. Moreover, the NH₂ groups optimize the local electron density and charge separation kinetics, significantly enhancing photocatalytic CO₂ reduction performance. Under visible-light irradiation, TCPP-NH₂Pyz-Co achieves a CO production rate of 2221.4 μmol g⁻¹ h⁻¹, offering valuable insights for the design of high-performance photocatalysts.

Results and discussion

The cobalt-based pillared-layer porphyrinic MOF materials were self-assembled using meso-tetra(4-carboxyphenyl) porphine (H₄TCPP), CoCl₂·6H₂O, and pyrazine (Pyz)/amino-pyrazine (NH₂Pyz) (Fig. S1†). As illustrated in Fig. 1a, the dinuclear Co(II) paddle-wheel nodes are linked by TCPP ligands to form two-dimensional (2D) square grids. These square grids are pillared by Pyz or NH₂Pyz ligands, which connect to the dinuclear Co(II) paddle-wheel nodes and the Co center of the porphyrin, forming a three-dimensional framework with a staggered arrangement as shown in Fig. 1b and c. Two cobalt-based pillared-layer single-crystal structures were confirmed by single crystal X-ray diffraction (SCXRD) (crystal data and structure refinement are provided in Table S1†) and optical micrographs (Fig. S2†). These MOFs were denoted as TCPP-Pyz-Co and TCPP-NH₂Pyz-Co. The simulated pore sizes of TCPP-Pyz-Co and TCPP-NH₂Pyz-Co, obtained using Mercury software, were 4.3 Å and 4.1 Å, respectively.

Fig. 1 Structures of pillared-layer (a) TCPP-Pyz-Co and TCPP-NH₂Pyz-Co. Pore structures of (b) TCPP-Pyz-Co and (c) TCPP-NH₂Pyz-Co. Powder X-ray diffraction patterns of (d) TCPP-Pyz-Co and (e) TCPP-NH₂Pyz-Co.

Powder X-ray diffraction (PXRD) and infrared (IR) spectroscopy (Fig. 1d, e and S3†) confirmed the successful synthesis of both MOFs. The experimental PXRD patterns matched the simulated results, indicating high phase purity. In TGA analysis (Fig. S4†), weight loss primarily occurs in three distinct stages: the first stage, observed below 300 °C, is attributed to the departure of residual solvent molecules from the framework material. The second stage occurring between 400 °C and 500 °C is the decomposition of the Co₂(COO⁻)₄ clusters. Finally, the weight loss observed above 500 °C is ascribed to the collapse of the framework due to the degradation of the porphyrin ligands.³⁶

The morphology and elemental distribution of TCPP-Pyz-Co and TCPP-NH₂Pyz-Co were characterized by scanning electron microscopy (SEM) (Fig. S5 and S6†). Both TCPP-Pyz-Co and TCPP-NH₂Pyz-Co exhibited block-like structures, with uniform distribution of C, N, O, and Co, as confirmed by energy-dispersive X-ray spectroscopy (EDS). X-ray photoelectron spectroscopy (XPS) further verified the presence of these elements, with peaks corresponding to Co 2p (781.8 eV), O 1s (531.8 eV), N 1s (399.8 eV), and C 1s (284.8 eV) (Fig. S7†). The Co 2p spectra of both TCPP-Pyz-Co and TCPP-NH₂Pyz-Co were deconvoluted into Co–O (797.0 eV for Co 2p_1/2 and 781.3 eV for Co 2p_3/2) and satellite peaks (802.3 eV and 785.1 eV). The O 1s spectra were resolved into Co–O (530.8 eV), C–O (531.7 eV) and C=O (530.1 eV). The N 1s spectra were divided into N–C (401.0 eV for TCPP-Pyz-Co and 400.5 eV for TCPP-NH₂Pyz-Co), pyrazine N (399.7 eV) and Co–N (398.8 eV), while the difference in binding energy of N–C is due to the introduced Lewis base –NH₂. Meanwhile, the C 1s spectra can be resolved into C=O (288.4 eV), C–O (286.5 eV), C–C (285.1 eV), C=C (284.5 eV) and C–N (284.0 eV). In addition, with the incorporation of amino functional groups, we further analyzed the N 1s spectra. The XPS peak area ratios for TCPP-Pyz-Co and TCPP-NH₂Pyz-Co are presented in Table S2.† A comprehensive analysis of the spectral areas reveals that upon introducing the NH₂ group, the content of C–N increased from 26.5% to 31.84%, whereas the contents of pyrazine-N and Co–N decreased slightly. These structural analyses confirmed the consistent framework integrity of both MOFs.

To investigate the influence of Pyz and NH₂Pyz ligands on the Co-porphyrinic MOFs, gas adsorption experiments were conducted (Fig. 2). N₂ adsorption isotherms at 77 K confirmed the permanent porosity of the samples (Fig. 2a). The pore sizes of TCPP-Pyz-Co and TCPP-NH₂Pyz-Co were approximately 3.7 Å and 3.9 Å, respectively, indicating their ultramicroporous nature (Fig. 2b). The measured pore sizes were slightly smaller than the theoretical values (Fig. 1b and c), likely due to residual non-activated solvents in the structure. The Brunauer–Emmett–Teller (BET) surface areas were 756 m² g⁻¹ and 684 m² g⁻¹ for TCPP-Pyz-Co and TCPP-NH₂Pyz-Co, respectively (Fig. 2c). The CO₂ adsorption studies revealed that the incorporation of Lewis-basic amino (–NH₂) functionalities significantly enhanced CO₂ uptake. At 273 K and 1 bar, TCPP-Pyz-Co and TCPP-NH₂Pyz-Co exhibited a CO₂ adsorption capacity of 54.3 cm³ g⁻¹ and 82.8 cm³ g⁻¹, respectively (Fig. 2d). Moreover, at 298 K and 1 bar, TCPP-NH₂Pyz-Co achieved a maximum CO₂ uptake of 54.3 cm³ g⁻¹, compared to 44.5 cm³ g⁻¹ for TCPP-Pyz-Co (Fig. 2e). The isosteric adsorption enthalpy (Q_st) values were calculated to be 17.9 kJ mol⁻¹ and 24.6 kJ mol⁻¹ for TCPP-Pyz-Co and TCPP-NH₂Pyz-Co respectively, indicating strong CO₂ affinity for the –NH₂-functionalized framework (Fig. 2f). The amino groups and organic linkers serve as high-affinity sites for CO₂ adsorption, with TCPP-NH₂Pyz-Co outperforming many recently reported MOFs (Table S3†).

Fig. 2 (a) 77 K nitrogen adsorption isotherms of TCPP-Pyz-Co and TCPP-NH₂Pyz-Co. (b) Pore size distribution analysis of TCPP-Pyz-Co and TCPP-NH₂Pyz-Co. (c) BET specific surface area calculation of TCPP-Pyz-Co and TCPP-NH₂Pyz-Co. CO₂ adsorption isotherms of (d) TCPP-Pyz-Co and (e) TCPP-NH₂Pyz-Co at 273 K and 298 K. (f) Isosteric heat of adsorption on TCPP-Pyz-Co and TCPP-NH₂Pyz-Co.

The excellent CO₂ adsorption properties of these TCPP-Pyz-Co and TCPP-NH₂Pyz-Co make them promising candidates for light-driven CO₂ reduction. Photoelectrochemical characterization (Fig. 3) revealed strong light absorption in the range of 500 to 800 nm (Fig. 3a). TCPP-NH₂Pyz-Co exhibited a photocurrent response twice as strong as that of TCPP-Pyz-Co (Fig. 3b), suggesting enhanced carrier separation and transfer efficiency. Electrochemical impedance spectroscopy (EIS) Nyquist plots showed the smallest semicircle for TCPP-NH₂Pyz-Co (Fig. 3c), indicating faster charge transfer kinetics and charge separation. The strong charge separation capability of TCPP-NH₂Pyz-Co can also be validated through photoluminescence (PL) spectroscopy in which the PL intensity of TCPP-NH₂Pyz-Co was weaker than that of TCPP-Pyz-Co (Fig. 3d), further confirming improved separation of photogenerated electron–hole pairs in TCPP-NH₂Pyz-Co. The band structures of TCPP-Pyz-Co and TCPP-NH₂Pyz-Co were measured as shown in Fig. 3e and f. The band gaps for TCPP-Pyz-Co and TCPP-NH₂Pyz-Co were determined to be 1.30 eV and 1.24 eV (Fig. 3e), respectively, by Tauc plot analysis. The NH₂ groups narrowed the band gap of TCPP-NH₂Pyz-Co to broaden the light absorption. Meanwhile, Mott–Schottky plots were obtained to evaluate the semiconductor characteristics of the MOFs and their potential for photocatalytic CO₂ reduction at frequencies of 1500, 2000 and 2500 Hz, shown in Fig. S10.† The positive slopes observed in the plots confirm the n-type semiconducting behaviour of TCPP-Pyz-Co and TCPP-NH₂Pyz-Co. Herein, the flat band potentials (E_fb) (the flat-band potentials are typically equal to the conduction-band potentials in n-type semiconductors) for TCPP-Pyz-Co and TCPP-NH₂Pyz-Co were determined to be −1.21 V and −0.99 V vs. NHE respectively, which are more negative than the reduction potential of CO₂/CO (0.53 V vs. NHE). Meanwhile, the corresponding valence band maximum (VBM) values of TCPP-Pyz-Co and TCPP-NH₂Pyz-Co were calculated to be 0.09 V and 0.25 V vs. NHE (Fig. 3f). In light of these cumulative findings, we conclude that TCPP-Pyz-Co and TCPP-NH₂Pyz-Co function as promising photocatalysts in light-driven CO₂RR. The intrinsic structural design incorporating these ligands enables robust light absorption and efficient photon harvesting capabilities. Furthermore, the introduction of the Lewis base functionality in TCPP-NH₂Pyz-Co narrows the band gap to broaden the light absorption range to increase the electrical conductivity.

Fig. 3 (a) UV-vis diffuse reflectance spectra of TCPP-Pyz-Co and TCPP-NH₂Pyz-Co. (b) The photocurrent densities over TCPP-Pyz-Co and TCPP-NH₂Pyz-Co with the reaction time under chopped visible light illumination. (c) EIS analysis of TCPP-Pyz-Co and TCPP-NH₂Pyz-Co. (d) Photoluminescence spectroscopy spectra of TCPP-Pyz-Co and TCPP-NH₂Pyz-Co. (e) Tauc plots of TCPP-Pyz-Co and TCPP-NH₂Pyz-Co. (f) Schematics illustrating the energy band structures of TCPP-Pyz-Co and TCPP-NH₂Pyz-Co.

Hence, the pillar-layered MOF structure is primarily responsible for facilitating CO₂ adsorption, which makes it suitable for catalysing the CO₂ reduction process. Based on this, artificial CO₂ photoreduction experiments were conducted by irradiating TCPP-Pyz-Co and TCPP-NH₂Pyz-Co with a visible light of 420 nm in a CO₂-saturated CH₃CN/H₂O solution. The experiments utilized triethanolamine (TEOA) as a sacrificial agent and Ru(bpy)₃Cl₂ as a photosensitizer, and gaseous products were quantitatively analysed by gas chromatography (GC). As shown in Fig. 4a, the amount of CO production significantly increased with extended reaction time. The CO yield of TCPP-NH₂Pyz-Co can reach 8885.5 μmol g⁻¹ after 4 hours of reaction, corresponding to a production rate of 2221.4 μmol g⁻¹ h⁻¹. In comparison, the activity of TCPP-Pyz-Co was slightly lower, with CO production reaching 7230.5 μmol g⁻¹ and a rate of 1807.6 μmol g⁻¹ h⁻¹. Furthermore, the photocatalytic process also induces the hydrogen evolution reaction (HER) as shown in Fig. 4b. TCPP-NH₂Pyz-Co demonstrated the highest HER catalytic performance producing 11 220.6 μmol g⁻¹ of hydrogen gas at a rate of 2805.2 μmol g⁻¹ h⁻¹, exhibiting an extremely high hydrogen production rate, which is higher than that of TCPP-Pyz-Co (10 929.0 μmol g⁻¹ and 2732.3 μmol g⁻¹ h⁻¹). Benefiting from NH₂ functionalization, TCPP-NH₂Pyz-Co exhibited a higher CO production rate compared to its non-NH₂-functionalized counterpart and other published studies^37–43 (Fig. 4c). The isotopic labelling experiments show that ¹³CO (m/z = 29) originated from the reactant of ¹³CO₂, which verifies that the generated CO comes from CO₂ rather than from the decomposition of the MOFs (Fig. 4d). Meanwhile, control experiments were conducted (Fig. 4e; the detailed information is provided in Table S4†); the absence of Ru(bpy)₃Cl₂ in the control experiments can produce only a little CO, and there is no CO gas produced in the absence of light, catalyst or TEOA. Moreover, TCPP-NH₂Pyz-Co demonstrated excellent robustness and durability during photocatalytic CO₂ reduction reactions. The catalyst maintained consistent performance with minimal activity loss over at least three consecutive test cycles (Fig. 4f). The stability of the TCPP-NH₂Pyz-Co photocatalyst structure was further confirmed by XRD analyses after cyclic testing, which showed no significant structural changes as shown in Fig. S11.†

Fig. 4 (a) Photocatalytic CO production and (b) H₂ production activity of TCPP-Pyz-Co and TCPP-NH₂Pyz-Co. (c) The performance comparison of TCPP-Pyz-Co and TCPP-NH₂Pyz-Co and other MOF catalysts in reference literature.^36–43 (d) ¹³C isotope labelling result based on GC-MS for TCPP-NH₂Pyz-Co. (e) Effect of TCPP-NH₂Pyz-Co photocatalytic CO₂ reduction under different conditions. (f) Recyclability of TCPP-NH₂Pyz-Co in CO₂ photoreduction.

To elucidate the active sites of the TCPP-NH₂Pyz-Co catalyst, a theoretical investigation was conducted via the model of TCPP-NH₂Pyz-Co (Fig. 5a). First, the CO₂ adsorption energies at Co–Co, Co–N₄, and –NH₂ sites were −27.09 kJ mol⁻¹, −22.90 kJ mol⁻¹, and −23.79 kJ mol⁻¹ respectively (Fig. 5b and S12†). Notably, these calculated values matched well with the Q_st value in Fig. 2f, proving the reliability of the theoretical calculation results. Herein, the Co–Co site exhibits the highest affinity for CO₂ adsorption, while the –NH₂ group also demonstrates a substantial adsorption energy, indicating a strong interaction with CO₂. The incorporation of –NH₂ groups effectively increases the density of potential CO₂ adsorption sites, thereby enhancing the material's overall CO₂ capture performance. In parallel, we examined the H₂O adsorption behaviour at the –COO and N₄ sites. Density functional theory (DFT) calculations indicate adsorption energies of −38.04 kJ mol⁻¹ and −27.63 kJ mol⁻¹ respectively (Fig. 5c and S13†). This suggests that the –COO site has a stronger affinity for H₂O compared to the Co–N₄ site. Meanwhile, the charge density difference (CDD) analysis illustrates CO₂ adsorption on the Co–Co sites and H₂O adsorption on the –COO groups of MOFs as presented in Fig. S14 and S15.† The results indicate that the adsorbed CO₂ and H₂O molecules exhibit significant charge interaction with the MOF, leading to effective activation of both species (specifically, the CO₂ adsorption density of TCPP-NH₂Pyz-Co is higher than that of TCPP-Pyz-Co as shown in Fig. 5d and S16†). Furthermore, we established the steps of TCPP-NH₂Pyz-Co reacting with CO₂ in Fig. S17.† Herein, [Ru(bpy)₃]²⁺ first absorbs a photon and reaches the excited state [Ru(bpy)₃]²⁺*. The excited state [Ru(bpy)₃]²⁺* then directly transfers an electron to the Co active site, thereby becoming the oxidized state [Ru(bpy)₃]³⁺. This oxidized state is subsequently reduced back to the ground state [Ru(bpy)₃]²⁺ by the sacrificial hole scavenger (TEOA).

Fig. 5 Photocatalytic mechanism. (a) The model of TCPP-NH₂Pyz-Co. Adsorption energy values for (b) CO₂ and (c) H₂O on various adsorption sites. (d) The CO₂ adsorption density of TCPP-NH₂Pyz-Co. (e) Calculated Gibbs free energy diagrams of the CO₂RR for TCPP-Pyz-Co and TCPP-NH₂Pyz-Co. (f) In situ DRIFT spectra over the TCPP-NH₂Pyz-Co catalyst at different irradiation times.

As illustrated in Fig. 5e, TCPP-Pyz-Co and TCPP-NH₂Pyz-Co undergo an adsorption process for CO₂, with the Gibbs free energy change from 0.0 eV to 0.19 eV and 0.25 eV (Fig. S18,† the computational model for each step). Subsequently, *CO₂ overcomes an energy barrier of 1.59 eV and 1.49 eV to obtain a proton (H⁺) and an electron (e⁻) to form *COOH. Following this, *COOH undergoes a thermodynamically spontaneous dehydration process to generate *CO and finally *CO undergoes a desorption process to convert to CO. In the CO₂RR process, the rate-determining step (RDS) was identified as the *CO₂ hydrogenation process (*CO₂ → *COOH). The energy barrier for the RDS of TCPP-NH₂Pyz-Co is lower than that of TCPP-Pyz-Co, implying the exceptional performance of TCPP-NH₂Pyz-Co in the critical intermediate step in the reduction of CO₂ to CO. Regarding the CO₂ reduction intermediates, we utilized in situ FTIR spectroscopy for verification. During illumination, peaks corresponding to *CO₂⁻, *COOH, and *CO₃²⁻/HCO₃⁻ were observed; the peak at 1348 cm⁻¹ is assigned to the bidentate carbonate (b-CO₃²⁻), and the peaks at 1378 cm⁻¹ and 1527 cm⁻¹ are assigned to monodentate carbonates (m-CO₃²⁻). The peaks corresponding to *CO₂⁻ are at 1247 cm⁻¹, 1278 cm⁻¹, 1689 cm⁻¹ and 1727 cm⁻¹, *COOH are at 1610 cm⁻¹ and 1646 cm⁻¹, and HCO₃⁻ are at 1178 cm⁻¹, 1208 cm⁻¹, 1439 cm⁻¹ and 1473 cm⁻¹, which are considered key intermediates in the formation and conversion of *CO into CO providing strong evidence for the computational data related to the CO₂ photocatalytic reduction process.^44–46 Collectively, the mechanism proposed for the CO₂RR facilitated by TCPP-NH₂Pyz-Co is that the dinuclear paddlewheel cobalt centers within TCPP-NH₂Pyz-Co serve a dual role during photocatalytic CO₂ reduction. These sites act as both effective catalytic centers and regions with enhanced CO₂ adsorption affinity. The high CO₂ adsorption density on the porphyrin framework corroborates this (Fig. S16†), indicating a notable kinetic advantage for photocatalytic CO₂ reduction. The Lewis base amino groups we introduced play multiple roles: (1) serving as secondary adsorption sites adjacent to the primary adsorption sites, synergistically enhancing CO₂ adsorption capacity of the framework; (2) modulating the band gap of the framework material thereby reducing carrier recombination. This work utilizes a simple Lewis base-introduced ligand strategy to enhance photocatalytic activity by modulating the CO₂ adsorption and band structure of the MOF, providing guiding significance for the design of porphyrin-based high-efficiency CO₂ reduction catalysts.

Conclusions

In summary, we report the design and construction of novel porphyrin-based pillared-layer MOFs using a Lewis base functionalization strategy, successfully fabricating TCPP-Pyz-Co and TCPP-NH₂Pyz-Co photocatalysts. The –NH₂ groups increased the density of high-affinity CO₂ adsorption sites, narrowed the band gap, and broadened the light absorption, promoting efficient charge separation and strengthening interactions with CO₂. The optimized TCPP-NH₂Pyz-Co exhibited superior performance in light-driven CO₂ reduction achieving a CO production rate of 2221.4 μmol g⁻¹ h⁻¹ (8885.5 μmol g⁻¹ over 4 h) and a hydrogen evolution rate of 2805.2 μmol g⁻¹ h⁻¹, significantly outperforming its non-functionalized counterpart. DFT calculations demonstrated that TCPP-NH₂Pyz-Co has active sites for CO₂ and H₂O, namely the Co–Co site and –COO site. This work provides a new direction for the design and synthesis of novel MOFs for CO₂ capture and photoreduction applications.

Data availability

The data that support the findings of this study are available from the corresponding author Zihao Xing (E-mail: xingzh612@nenu.edu.cn) upon reasonable request.

Author contributions

The study was conceptualized by X. G. and Z. X., who also conducted the experiments and drafted the manuscript. Samples were prepared by C. C. and W. L. Initial research planning and experimental setup were contributed by Z. X. SEM analysis was performed by W. X., while N. M. conducted the sample characterization. X. Z. also took the input through discussions. J. C. and Z. X. supervised the research, supported the discussions and facilitated the acquisition of necessary equipment. All authors reviewed and approved the final manuscript. Notably, X. G., C. C., and W. L. made equal contributions to this work.

Conflicts of interest

The authors declare no competing financial interest.

Acknowledgements

This work was supported by the Science and Technology Development Plan Project of Jilin Province, China (20240101192JC). This work was also supported by the National Natural Science Foundation of China (22202037 and 22472023) and the Fundamental Research Funds for the Central Universities (2412024QD014 and 2412023QD019).

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Footnotes

† Electronic supplementary information (ESI) available. CCDC 2447987 and 2447985. For ESI and crystallographic data in CIF or other electronic format see DOI: https://doi.org/10.1039/d5ta03720d

‡ These authors contributed equally to this work.

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