Recent advances in polymeric materials for direct carbon dioxide capture from ambient air

Abstract

The continuous rise in the atmospheric carbon dioxide (CO₂) concentration has led to increasingly severe climate problems. Direct air capture (DAC) technology is regarded as a promising “negative emission” approach, which has been attracting considerable attention in recent years. The design of DAC materials that combine high efficiency, long-term stability, and economic feasibility has become a major challenge. This review highlights the recent advances in the synthesis and CO₂ capture performance of polymer-based DAC systems, with particular emphasis on functional polymers, polymer composites, metal–organic frameworks (MOFs) and covalent organic frameworks (COFs). By summarizing key synthetic strategies and structure–property relationships, this article aims to provide theoretical guidance and technical references for the development of next-generation high-performance carbon capture materials while outlining emerging opportunities for DAC material innovation.

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1. Introduction

The industrial revolution lasted for over two hundred years. The massive combustion of fossil fuels pushed the atmospheric carbon dioxide (CO₂) concentration from approximately 280 ppm to 420 ppm, triggering a global average temperature increase of 1.1 °C compared with the pre-industrial level. According to the Intergovernmental Panel on Climate Change (IPCC), global carbon emissions must peak before 2025 and then decline by 43% by 2030; otherwise, it will trigger irreversible chain reactions such as polar ice sheet collapse, ocean current disturbances, and extreme climate events.^1–3 According to the IPCC climate change 2023 synthesis report, to constrain warming to within 1.5 °C, the capture and storage of 5–10 Gt of CO₂ annually will be required by mid-century. Consequently, carbon capture has evolved from a peripheral industrial practice into a critical necessity for climate change mitigation.^4–22

The current mainstream carbon capture and storage (CCS) strategies are primarily designed for large, centralized emission sources, such as fossil fuel power plants and energy-intensive industries (e.g., cement and steel production industries).^23–25 These approaches generally fall into three technical pathways: post-combustion capture, in which CO₂ is separated from flue gases; pre-combustion capture, which involves the conversion of fuel to syngas followed by CO₂ separation prior to combustion; and oxyfuel combustion, wherein oxygen replaces air as the oxidant to generate CO₂-rich streams that facilitate capture.²⁶ These approaches have made significant contributions to carbon emission reduction.^27,28 Nonetheless, several fundamental challenges remain. First, nearly 55% of global greenhouse gas emissions originate not from large stationary sources but from diffuse, mobile, or distributed activities, including transportation (e.g., vehicles, ships, and aircraft) and agricultural practices (e.g., soil management and livestock breeding).^29–31 Such emissions are widely dispersed and often occur remotely, rendering them inaccessible to current CCS strategies.^32–34 Second, even if the world were to transition immediately to net-zero emissions, the vast amount of anthropogenic carbon dioxide accumulated in the atmosphere since the Industrial Revolution (≈1.6 × 10¹² t) would persist, continuing to drive long-term impacts such as warming inertia and sea-level rise.^35–37 Third, suitable geological storage sites are unevenly distributed and frequently distant from major emission hubs, necessitating extensive pipeline networks spanning hundreds to thousands of kilometers or reliance on more costly modes of transport, such as shipping and trucking.^38–40 Accordingly, the large-scale deployment of “negative-emission” technologies, particularly the direct air capture of CO₂, is imperative for removing the legacy carbon already accumulated in the atmosphere. The development of advanced CO₂ capture strategies that are capable of overcoming the aforementioned limitations is therefore of critical scientific and technological importance.^41–43

Direct air capture (DAC), as a new CO₂ capture technology, is presented in Fig. 1.^44–47 Unlike other technological approaches, DAC does not target specific emission sources but directly captures CO₂ from the global atmospheric background concentration (about 420 ppm). It does not require the modification of dispersed sources and is capable of actively removing historical carbon emissions. DAC technology is like “catching” CO₂ molecules in the air. Its core lies in the fact that it can enable the contact between ambient air and adsorption material that is specially designed for low-concentration CO₂ through a specific engineering system.^48–51 The technical process usually consists of two key steps: “adsorption” and “desorption”.^52–54 During the adsorption stage, a large amount of air is brought into contact with the specific adsorption material, and the active sites on its surface selectively capture CO₂ molecules. In the desorption stage, by applying heat, vacuum, or changing the humidity conditions of the adsorbent, high-concentration CO₂ is released for storage or resource utilization. At present, the commercialization of DAC is still in its early stages, and the capture cost varies significantly depending on the technical route, project scale, and calculation method. The mainstream estimates range from several hundred dollars to several thousand dollars per ton of CO₂.⁵⁵ Therefore, the efficiency, energy consumption, and cost of DAC technology largely depend on the design of the adsorption material. High-performance absorbers are the key to achieving large-scale, low-energy consumption for CO₂ capture from the air.^56,57

Fig. 1 Diagram showing the direct air capture of CO₂. The adsorbent directly captures CO₂ at a concentration of around 420 ppm in the air and then gathers and concentrates the captured CO₂ for subsequent utilization.

2. Overview of different DAC sorbent materials

DAC sorbent materials are traditionally classified into liquid absorbents and solid adsorbents.⁵⁸ Liquid systems are dominated by alkaline hydroxide solutions (e.g., NaOH), which exhibit rapid CO₂ uptake kinetics but require extremely energy-intensive regeneration at temperatures approaching 900 °C. Amine-based solutions, such as monoethanolamine (MEA), operate at lower regeneration temperatures. However, their practical deployment is hindered by volatility, toxicity, and limited regeneration efficiency.

In response to these limitations, increasing attention has been directed toward solid polymer adsorbents as next-generation DAC materials.^59–62 Solid polymer-based sorbents combine rapid sorption kinetics with reduced corrosivity and volatility, as well as substantially lower regeneration energy requirements relative to conventional liquid systems.^63–66 Therefore, this review concentrates on recent advances in the molecular design, structure–property relationships, and performance evaluation of solid polymer adsorbents for direct air capture, highlighting their potential to overcome the key bottlenecks associated with existing DAC technologies.

3. Polymeric materials for the direct air capture of CO₂

Unlike capture from concentrated point sources (e.g., flue gas from coal-fired power plants, CO₂ > 10%), DAC must overcome the inherent challenges of low CO₂ partial pressure, substantial mass-transfer resistance, and elevated energy demand.⁶⁷ These constraints impose stringent requirements on sorbent materials, which must combine high adsorption capacity under low pressure, good selectivity over major air components (N₂ and O₂), rapid adsorption–desorption kinetics suitable for cyclic operation, long-term stability under environmental perturbations (e.g., water vapor and temperature fluctuations), and scalability with low cost to enable practical deployment. Among the candidate sorbent classes, polymers have emerged as particularly promising owing to their exceptional structural tunability, wherein functional groups, pore architectures, and surface chemistries can be precisely engineered at the molecular level, together with their favorable processability into films, particulates, or monolithic forms, their amenability to postsynthetic functionalization for enhancing CO₂ affinity, and their comparatively low manufacturing cost. Based on their composition and structural features, polymer-based DAC materials can be systematically classified into the following categories: (1) organic polymers, (2) polymer composites, (3) metal–organic frameworks (MOFs), and (4) covalent organic frameworks (COFs) (Fig. 2). The adsorption properties and desorption conditions of different types of DAC materials are summarized in Table 1.

Fig. 2 Four different types of DAC materials.

Table 1 Comparison of the adsorption properties and desorption conditions of different types of DAC materials

Sorbent	Uptake (mmol g^−1)	Absorption conditions			Regeneration condition	Cyclic number	Ref.
		Temp. (°C)	RH^a (%)	CO2 concentration
a RH: relative humidity. b N. D.: no description.
[bmim][BF4]	0.12	22	N. D.	529.3 mm Hg	Vacuum	4	73
PF-15-TAEA	0.8	25	0	400 ppm	70 °C	15	74
DADMA(OH)-PSf	0.048	25	30	400 ppm	Moisture-swing	N.D.	75
QA-Poly(AES)	0.032	22	30	400 ppm	Moisture-swing	12	76
Polyanthraquinone	N. D.^b	25	N. D.	6000 ppm	Electrochemistry	7000	77
PEIBr_MCF_39	1.72	25	N. D.	400 ppm	110 °C	N. D.	84
T-PEI/silica	2.16	25	0	400 ppm	110 °C	4	85
PEI/Si	2.27	50	0	10%	110 °C	10	86
MSF	1.41	25	25	400 ppm	100 °C	10	89
PPN-6-CH2DETA	1.04	21.85	N. D.	400 ppm	N. D.	N. D.	92
F–GO sorbent	3.24	25	20	400 ppm	Moisture-swing	50	93
PEI/resin	2.256	25	0	400 ppm	N. D.	5	95
NH2–Mg/DOBDC	1.5	25	0	400 ppm	120 °C	4	101
en-Mg2(dobpdc)	2.83	25	0	390 ppm	120 °C	20	103
UiO-66-NH2	3.2	25	0	1 bar	150 °C	8	107
Zn(ZnO2CCH3)4(bibta)3	2.2	26.85	0	400 ppm	100 °C	5	109
Mg-Mof-74	0.143	25	15	400 ppm	180 °C	N. D.	111
CALF-20	4.07	19.85	0	1.2 bar	Steam regeneration	30	112
NbOFFIVE-1-Ni	1.3	25	0	400 ppm	55 °C	24	114
SIFSIX3-Cu	1.24	25	0	400 ppm	N. D.	N. D.	115
COF-609	0.393	25	50	400 ppm	100 °C	N. D.	119
COF-999	2.05	25	50	400 ppm	60 °C	100	120
COF-709	1.24	25	75	400 ppm	95 °C	10	121

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3.1 Organic polymers

Organic polymers constitute a versatile class of macromolecular materials in which repeating units are covalently linked into well-defined architectures. Their principal advantage for DAC resides in the ability to precisely tailor chain functionality, pore topology, and physicochemical properties through judicious monomer design and polymerization strategies.^68,69 In particular, the incorporation of amine functionalities into polymer backbones markedly enhances CO₂ selectivity by enabling specific chemisorptive interactions, such as the formation of carbamate or carbonate-type intermediates. These amine-containing polymers are therefore capable of reversibly binding CO₂ through well-defined reaction mechanisms, which proceed predominantly via two distinct pathways:

Anhydrous condition:

2R–NH₂ + CO₂ → R–NH₃⁺ + R–NHCOO⁻, ΔH ≈ −60 to −80 kJ mol⁻¹

Hydrous condition:

R–NH₂ + CO₂ + H₂O → R–NH₃⁺ + HCO₃⁻, ΔH ≈ −40 kJ mol⁻¹

Under rigorously anhydrous conditions, primary and secondary amines (RNH₂/R₂NH) react directly with CO₂ to form carbamate species. Because proton transfer is required in this process, each CO₂ molecule is captured by two amine molecules—one forming the carbamate and the other being protonated. In the presence of water, the reaction pathway is fundamentally altered. Amines initially associate with CO₂ to generate a highly energetic amphiprotic ion intermediate, which is intrinsically unstable and is rapidly attacked by water to yield bicarbonate anions and protonated amines. Alternatively, CO₂ may first hydrate to carbonic acid, after which amines facilitate its dissociation, likewise producing bicarbonate species accompanied by protonated amines.

Recently, a class of humidity-swing polymeric sorbents has been developed that enables reversible CO₂ capture from ambient air at room temperature through simple modulation of environmental humidity.^70,71 Jacob Schaefer et al. investigated humidity-swing CO₂ adsorption–desorption mechanisms using solid-state nuclear magnetic resonance spectroscopy.⁷² They found that at low humidity levels, CO₂ is absorbed in the form of HCO₃⁻; at high humidity levels, HCO₃⁻ is replaced by hydrated OH⁻, and the absorbed CO₂ is released (Fig. 3a).

Fig. 3 Polymers (a–f) with the humidity fluctuation-type CO₂ absorption–desorption cycle.

Weilin Sun et al. discovered that poly(ionic liquid)s (PILs) formed from monomers with ionic liquid groups outperformed room-temperature ionic liquids in terms of CO₂ adsorption capacity and adsorption/desorption rate (Fig. 3b–f).⁷³ For example, poly[1-(vinylbenzyl) trimethylammonium tetrafluoroborate] (P[VBTMA]–[BF₄]) has a CO₂ adsorption capacity of 10.2 mol% per polymer monomer unit at a CO₂ pressure as low as 0.78 bar (22 °C), which is 6.6 times that of room-temperature ionic 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]). PILs create a hydrophilic, ionized microenvironment that facilitates water ingress and diffusion, shifting the reaction mechanism toward bicarbonate formation and enabling higher CO₂ uptake capacities and accelerated sorption kinetics under moderately humid conditions. These observations underscore that the rational modulation of pore topology and functional group chemistry provides a powerful means to tune the reaction pathway, thermodynamics, and kinetics of amine-CO₂ chemistry, ultimately allowing the optimization of capture efficiency and regeneration energy under realistic atmospheric environments.

PIMs feature rigid, hydrophobic pore architectures that effectively exclude water, thereby favoring CO₂ capture through the carbamate formation pathway and rendering them particularly well suited for DAC operation under fluctuating humidity. David Hopkinson obtained the target PIMs by conducting a polymerization reaction between 3,3,3,3-tetramethyl-1,1-bicyclohexane-5,5,6,6-tetrol and 2,3,5,6-tetrachlorobenzonitrile, and then adding hydroxylamine. The surface of the product has amide oxime and amine functional groups and was prepared into a high-performance CO₂ adsorbent. The fibrous adsorbent is composed of a single porous polymer, and its molecular amine functional groups can increase the CO₂ capture capacity and adsorption rate (Fig. 4).⁷⁴ This material exhibits a Brunauer–Emmett–Teller (BET) surface area of 503 m² g⁻¹ and displays pronounced CO₂ uptake at ultralow partial pressures. Specifically, PF-15-TAEA achieves a gravimetric capacity of 3.3 wt% (17 mL g⁻¹, corresponding to 0.8 mmol g⁻¹) at 400 ppm CO₂ and 298 K. The systematic modulation of the degree of functionalization and screening of a series of alkylamine moieties resulted in marked enhancements in both CO₂ adsorption capacity and CO₂/N₂ selectivity, with performance exceeding that of PIM-1 by more than a factor of four.

Fig. 4 Polymer fibers with an internal microporous structure.

Polysulfone (PSF) is an important material due to its good strength and thermal stability, making it suitable for various applications. Quaternary ammonium salt polymers are also useful materials due to their ion-exchange properties, and such materials with basic counterions can capture CO₂ from ambient air through a water-driven mechanism. Daniel M. Knauss et al. designed sulfone-based copolymers with ammonium functional groups and demonstrated their potential in CO₂ capture. Specifically, a series of multiblock copolymers containing polydiallyl-dimethylammonium (PDADMA) and polysulfone segments was synthesized. The PSF segment provided mechanical integrity, while the PDADMA segment achieved direct CO₂ capture from the ambient air. The multiblock copolymers were synthesized with high yield, forming PDADMA(OH)-PSF copolymer films with good flexibility and strength (Fig. 5a).⁷⁵ Matthew D. Green et al. synthesized a series of quaternary (QA) functionalized poly (arylene ether sulfone) copolymers with different charge content molar ratios and demonstrated their potential as DAC adsorbents (Fig. 5b).⁷⁶ When this material is exposed to air with a relative humidity of 30%, these polymers capture CO₂, and their capacity increases with the increase in ionic exchange capacity (IEC). When the relative humidity reaches 95%, the samples release CO₂. This demonstrates a promising DAC adsorbent for CO₂. By attaching these polymers with DAC properties onto a substrate with a supporting structure through casting, extrusion, electrospinning, or coating methods, the chemical reactions can be more directly linked to practical applications.

Fig. 5 (a) Multiblock copolymer composed of the PDADMA and PSF segments. (b) QA-functionalized poly(arylene ether sulfone) copolymers.

Anthraquinone derivatives have been identified as promising redox-active motifs for electrochemically mediated CO₂ capture. Sahag Voskian and T. Alan Hatton reported the synthesis and implementation of polyanthraquinone in a solid-state faradaic electrochemical adsorption platform, in which CO₂ uptake is driven by the reversible redox reaction between quinone units and CO₂ (Fig. 6).⁷⁷ In the intake flow, the CO₂ concentration in the feed stream ranged from 0.6% (6000 ppm) to 10%. At a fixed CO₂ inventory, the electrochemical system achieved an apparent faradaic efficiency of up to 490% in a sealed, pure-CO₂ environment, while requiring only 40–90 kJ of work per mole of CO₂ captured. The device further demonstrated excellent operational durability, retaining ∼70% of its initial capacity after 7000 charge–discharge cycles under 100% CO₂.

Fig. 6 CO₂ capture and release under the electrochemical action of polyanthraquinone. Reproduced with permission from ref. 77. Copyright 2019, the Royal Society of Chemistry.

3.2 Polymer composites

To circumvent the inherent limitations of single-component organic polymers with respect to pore architecture, surface chemistry, and mechanical robustness, polymers have been integrated with complementary functional components, including inorganic fillers, porous aromatic frameworks, and carbon-based materials, to construct multiscale, synergistic composite sorbents with enhanced overall performance.⁷⁸ Representative design strategies encompass polymer–inorganic filler composites, polymer–porous aromatic framework hybrids, and polymer–carbon material composites (Fig. 7).⁷⁹

Fig. 7 PEI doped into different substrates.

Polymer–inorganic filler composites are typically prepared by dispersing SiO₂ nanoparticles, zeolites, or metal oxides (e.g., MgO and CaO) within polymer matrices such as polyethyleneimine (PEI).⁸⁰ The incorporation of rigid inorganic phases enhances the mechanical integrity of the sorbent while simultaneously introducing additional adsorption sites.^81–83 For example, Christopher W. Jones and co-workers synthesized low-molecular-weight polyacrylamide via free-radical polymerization and subsequently impregnated the polymer into mesoporous silica foams at varying amine loadings.⁸⁴ The resulting poly(acrylamide)–silica composites were demonstrated to be highly effective for CO₂ capture from both dilute streams representative of flue gas and ultra-dilute streams simulating ambient air.

In the same year, Christopher W. Jones et al. prepared silica-loaded PEI materials by an impregnation method and proved that they were highly potential CO₂ capture agents suitable for capturing CO₂ from ultra-dilute gas streams, including ambient air.⁸⁵ George A. Olah and colleagues similarly reported solid sorbents, based on gas-phase silica loaded with PEI, which were effective for direct air capture. Subsequent studies revealed that the incorporation of additives into polymeric amines and their immobilization on mesoporous oxide supports constitute an efficient strategy for further enhancing capture performance. In this context, the synthesis of well-defined poly(acrylamide) (PGA) via controlled anionic polymerization was described, followed by post-polymerization modification and immobilization on mesoporous silica (SBA-15), which enabled efficient CO₂ capture from both dilute flue-gas streams and ultra-dilute ambient air.⁸⁶

Aldo Steinfeld et al. designed a temperature-vacuum fluctuation (TVS) process for extracting pure CO₂ from dry and humid ambient air.⁸⁷ This process operates through cyclic adsorption–desorption in a packed bed comprising amine-functionalized commercial silica gel under both equilibrium and short-cycle, non-equilibrium conditions. Compared with ungrafted PEI/SiO₂, the functionalized sorbent exhibited an enhanced CO₂ uptake of 1.4 mmol g⁻¹ and maintained its performance following aging under 50% relative humidity. George A. Olah and colleagues subsequently optimized the composition of PEI–polyethylene glycol composites, affording regenerable materials with the requisite attributes for practical implementation, including effective capture from both concentrated sources such as flue gas and natural gas streams and ultra-dilute ambient air.⁸⁸ Nader Mahinpey and co-workers further demonstrated that in situ polymerization of amine functionalities within mesoporous silica frameworks significantly enhances CO₂ adsorption capacity.⁸⁹ Building on these concepts, Jiping Chen and co-workers developed an efficient capture material via a co-grafting strategy in which PEI was covalently anchored onto mesoporous silica foams using (3-glycidoxypropyl)triethoxysilane (GPTES) as a molecular linker (Fig. 8).⁹⁰

Fig. 8 PEI co-grafted onto mesoporous silica foam, using GPTES as the linking agent. Reproduced with permission from ref. 90. Copyright 2023, Elsevier B.V.

Polymer–porous polymer hybrid materials are constructed by integrating porous organic polymers with conventional polymer matrices, such as polyimides or polyurethanes, thereby leveraging the high surface areas and well-defined pore architectures of the porous components to promote CO₂ diffusion and enhance adsorption selectivity.⁹¹ Concomitantly, the continuous polymer phase improves the dispersibility of the porous domains and confers superior mechanical integrity to the composite. In this context, Hong-Cai Zhou and co-workers reported amine-functionalized porous polymer networks capable of capturing CO₂ directly from ambient air. Purely organic porous polymers exhibit surface areas comparable to those of MOFs yet benefit from fully covalent frameworks that impart exceptional chemical and thermal stability. The incorporation of polyamine functionalities into these networks markedly increases low-pressure CO₂ uptake and enables sorbent regeneration under mild conditions (Fig. 9).⁹²

Fig. 9 Utilizing amine-grafted porous polymer networks to capture CO₂ from the air.

Polymer–carbon material composites are formed by introducing activated carbon, graphene, or carbon nanotubes into the polymer network. The high conductivity (suitable for electro-assisted regeneration) and hydrophobicity (resistant to water vapor competitive adsorption) of the carbon materials can synergistically enhance the material's cycle stability and adsorption efficiency.

Cataldo Simari et al. used commercial graphene flakes and added glycidyltrimethylammonium chloride to incorporate quaternary ammonium groups sensitive to CO₂. The functionalized adsorbent (fGO) exhibited exceptional CO₂ capture performance under ultra-dilute conditions, achieving an uptake of 3.24 mmol g⁻¹ at 400 ppm CO₂ and 20% relative humidity (Fig. 10), thereby outperforming representative state-of-the-art DAC sorbents. Over 50 adsorption–desorption cycles, the capacity decreased by only 7.5%, with the adsorption kinetics reaching a steady state within 200 min. Regeneration was accomplished via a humidity-swing mechanism.⁹³ Lackner and Chen et al. reported a humidity-responsive, energy-efficient composite system comprising ion-exchange or nanoporous materials in conjunction with carbonate species for direct air capture. In this platform, CO₂ uptake and release are modulated solely by controlling the local water activity: under dry conditions the material spontaneously absorbs CO₂ from ambient air, whereas exposure to humid environments triggers CO₂ desorption. Quantum mechanical simulations, corroborated by experimental validation, revealed that this reversible behavior originates from variations in the free energy of the carbonate-water reaction as a function of hydration level, with decreased water content leading to a more favorable free-energy change for CO₂ binding. The study further elucidated the roles of key structural parameters, including pore dimensions, cation–cation separation distances, and surface hydrophobicity, in governing capture efficiency. These insights establish fundamental design principles for the rational optimization of next-generation, low-energy DAC materials.⁹⁴

Fig. 10 Quaternary ammonium graphene used for high-performance moisture-swing direct air CO₂ capture. Reproduced with permission from ref. 93. Copyright 2024, John Wiley and Sons.

Gang Yu and co-workers reported a highly efficient adsorbent for CO₂ capture from both simulated flue gas and ambient air, based on PEI-impregnated resins.⁹⁵ The CO₂ adsorption on this material proceeds rapidly at 75 °C, reaching equilibrium within 6 min, and the adsorption capacity remains essentially unchanged over multiple adsorption–desorption cycles. In a complementary approach, Krzysztof Matyjaszewski and colleagues employed hyperbranched polymers functionalized with carbon black for reversible CO₂ capture.⁹⁶ These porous polymers exhibited an order-of-magnitude enhancement in both absorption and desorption rates, along with substantial increases in oscillation amplitude. Collectively, these studies provide valuable insights into the design of porous polymeric materials for efficient CO₂ capture from air.

3.3 MOFs

In addressing the formidable challenges associated with DAC, MOFs offer distinct advantages owing to their exceptional structural tunability.⁹⁷ Current efforts in MOF-based adsorbent development are directed toward creating materials that combine high CO₂ selectivity, reversible adsorption, and robust stability.^98,99 To be effective, such adsorbents must exhibit strong affinity and selectivity for CO₂. Moreover, practical implementation imposes additional constraints, including competitive adsorption of water vapor, temperature fluctuations, and requirements for long-term operational stability, all of which further complicate material design and performance optimization.

Compared to conventional adsorbents such as zeolites, activated carbon, and amine-functionalized resins, MOFs offer distinct advantages for DAC. By the rational selection of metal nodes and organic linkers, the pore size (0.5–5 nm), geometry, and surface chemical environment of MOFs can be precisely tuned to achieve selective recognition of CO₂ molecules. In addition, MOFs exhibit exceptionally high specific surface areas (1000–7000 m² g⁻¹), providing a dense network of adsorption sites.¹⁰⁰ Furthermore, the incorporation of diverse functional groups, including amino functionalities, open metal sites, and fluorinated moieties, onto the pore surfaces can markedly enhance CO₂ binding, enabling highly efficient capture under ambient conditions.

Amine-functionalized MOFs represent a prototypical class of chemisorption-dominated adsorbents. In these materials, amino groups are introduced into the MOF pores, where they undergo reversible chemical reactions with CO₂ to form carbamate or bicarbonate species, enabling efficient capture. On the synthesized MOF scaffold, the amino functionalities are covalently grafted through postsynthetic modification. Among the MOFs, Mg/DOBDC exhibits the highest known CO₂ adsorption capacity, with a partial pressure range suitable for flue gas capture; however, its poor regenerability limits its applicability in cyclic operation. In seminal work by Christopher W. Jones and co-workers, the open metal sites of Mg/DOBDC were functionalized with ethylenediamine (ED), introducing terminal amino groups into the micropores.¹⁰¹ Characterization revealed an average of one ED molecule per unit cell. This modification not only enhances CO₂ uptake at ultra-low partial pressures but also improves the material's recyclability, maintaining consistent adsorption–desorption performance over multiple cycles. Notably, this represents one of the first MOF-based materials to achieve significant CO₂ capture from simulated ambient air (400 ppm), with performance comparable to the most effective amine–oxide complex adsorbents.

Jeffrey R. Long and co-workers functionalized mmen-Mg₂(dobpdc) with alkylamines via unsaturated metal coordination (Fig. 11a).¹⁰² This material exhibits strong CO₂ adsorption at low pressures, achieving a cycle capacity of 1.05 mmol g⁻¹ (4.4 wt%) after 1 h exposure to simulated air containing 390 ppm CO₂ at 25 °C, and 2.52 mmol g⁻¹ (9.9 wt%) after 15 min exposure to 15% CO₂ in N₂ at 40 °C. The purity of the separated CO₂ from dry air and flue gas was estimated at 96% and 98%, respectively, although long-term cycling beyond 500 cycles was not evaluated. Chang Seop Hong and colleagues developed a binary amine-functionalized MOF via postsynthetic modification, which exhibited both high CO₂ uptake from ambient air and flue gas and ultra-fast adsorption kinetics. At 0.15 Pa, the material captured 3.62 mmol g⁻¹ (13.7 wt%), comparable to post-combustion CO₂ partial pressures, while at 0.39 mbar, near atmospheric CO₂ levels, it achieved 2.83 mmol g⁻¹ (11.1 wt%). Notably, the CO₂ capacity remained nearly constant over repeated adsorption–desorption cycles, demonstrating potential for practical DAC applications.¹⁰³

Fig. 11 Different MOFs (a–i) with good CO₂ capture performance or the capability for directly capturing CO₂ from the air. Reproduced with permission from ref. 102, 106–109, 111, 112, 114 and 115. Copyright 2014–2018, Springer Nature Group, John Wiley and Sons and the American Chemical Society. Copyright 2020, the American Chemical Society. Copyright 2021, the American Association for the Advancement of Science. Copyright 2023, Springer Nature Group.

Christopher W. Jones and co-workers reported that MIL-101(Cr) functionalized with branched poly(ethyleneimine) exhibits improved cycle stability for CO₂ capture from simulated air.¹⁰⁴ In a complementary study, Long and colleagues evaluated nine amine-grafted Mg₂(dobpdc) variants, revealing stepwise adsorption isotherms arising from synergistic, reversible CO₂ insertion into metal–amine bonds. Minor modifications to the amine structure were found to increase the threshold pressure for cooperative CO₂ adsorption by more than four orders of magnitude at a given temperature.¹⁰⁵ Nataša Zabukovec Logar et al. investigated ethylenediamine-functionalized HKUST-1 (Fig. 11b), showing that while grafting reduced surface area and total CO₂ capacity, it increased CO₂ binding energy by 85% (from −20.3 to −36.8 kJ mol⁻¹) and doubled CO₂/N₂ selectivity at 0.15/0.85 bar, while also enhancing adsorption kinetics.¹⁰⁶

Ahad Ghaemi and co-workers synthesized UiO-66-NH₂ (Fig. 11c) via an ultrasonic-assisted method in only 1 h.¹⁰⁷ The material exhibited a CO₂ uptake of 3.2 mmol g⁻¹ at 25 °C and 1 bar, ∼0.9 mmol g⁻¹ higher than the conventional solvothermal analogue, with minimal capacity loss (0.6 mmol g⁻¹) over eight consecutive cycles. Xiao-Ming Chen and colleagues reported the hydroxyl-functionalized porous framework MAF-X27ox (Fig. 11d), which achieved high CO₂ affinity, adsorption capacity, and CO₂/N₂ selectivity via reversible carbonic acid formation/decomposition. The material captured up to 13.4 wt% CO₂ from simulated flue gas under 82% relative humidity and allowed rapid desorption under mild conditions (N₂ purge at 182 °C).¹⁰⁸ W. S. Winston Ho et al. prepared a zinc benzotriazole ester MOF (Zn(ZnOAc)₄ SBUs; Fig. 11e), in which postsynthetic ligand exchange and thermal activation generated nucleophilic Zn–OH groups analogous to the α-carbonic anhydrase active site.¹⁰⁹ This modification enabled efficient trace CO₂ capture with facile regeneration at mild temperatures.

Physisorption-dominated MOFs capture CO₂ primarily through electrostatic interactions, van der Waals forces, and dipole–quadrupole interactions. These materials typically feature high specific surface areas and precisely engineered pore architectures, enabling relatively low regeneration energies. A particularly effective strategy involves the construction of coordinatively unsaturated metal sites (open metal sites, OMSs). Upon activation, the removal of bound solvent molecules from metal centers such as Mg²⁺, Mn²⁺, Ni²⁺, and Co²⁺ exposes Lewis-acidic OMSs that interact strongly with CO₂. Owing to the large quadrupole moment of CO₂ (13.4 × 10⁻⁴⁰ C m²), the electronegative oxygen atoms engage in strong dipole–quadrupole interactions with positively charged OMSs. In Mg-MOF-74 (Mg₂(dobdc)), for example, each Mg²⁺ site can bind one CO₂ molecule, affording an isosteric heat of adsorption (Q_st) of 40–50 kJ mol⁻¹ at low loadings, substantially exceeding that of conventional physisorbents and enabling high capture capacities even at 400 ppm CO₂.

Despite these advantages, the primary limitation of OMS-containing MOFs is their pronounced sensitivity to moisture. Water competes directly with CO₂ for coordination to metal sites, resulting in diminished adsorption performance. The average adsorption energy of water within hydrogen-bonded chains in the MOF unit cell is 13.3 kcal mol⁻¹.¹¹⁰ In a systematic study, Michael J. Zaworotko and co-workers evaluated the direct air capture performance of TEPA-SBA15, zeolite 13X, HKUST-1, Mg-MOF-74 (Mg₂(dobdc); Fig. 11f),¹¹¹ and SIFSIX-3Ni. Although several MOFs displayed efficient CO₂ uptake from mixed gases with elevated CO₂ concentrations, competitive adsorption and reaction with atmospheric water severely compromised their performance under true direct air capture. George K. H. Shimizu and co-workers reported the scalable zinc-based MOF CALF-20 (Fig. 11g),¹¹² which captures CO₂ predominantly via physisorption. The centrally located binding sites within its pores suppress the formation of extended hydrogen-bonded water networks, enabling preferential CO₂ uptake at 40% relative humidity and sustained performance under flue-gas conditions up to 150 °C.

Michael J. Zaworotko and co-workers introduced a crystal-engineering, or “network,” strategy to precisely control pore functionality and dimensions, leading to a family of hexafluorosilicate (SiF₆) molecular encapsulants in the SIFSIX series.¹¹³ In these frameworks, periodically arranged SiF₆²⁻ anions generate a highly electronegative fluorine array within the channels. The resulting strong electrostatic field interacts favorably with the electropositive carbon center of CO₂, markedly enhancing the isosteric heat of adsorption (Q_st) and selectivity. These interactions, intermediate in strength between physisorption and chemisorption, are often described as “strong physisorption” or cooperative adsorption, combining rapid adsorption–desorption kinetics with relatively low regeneration energies. The SIFSIX materials exhibit high volumetric uptake at low CO₂ partial pressures (<0.15 bar) and outstanding selectivity over N₂, H₂, and CH₄ in post-combustion, pre-combustion, and natural gas upgrading scenarios.

Building on this concept, Mohamed Eddaoudi and co-workers constructed SIFSIX-3-Cu (Fig. 11h) from a two-dimensional pyridine–Cu(II) square grid supported by hexafluorosilicate anions, achieving a Q_st of 53.4 kJ mol⁻¹ at room temperature and exceptional CO₂ selectivity under ultralow partial pressures relevant to air capture and trace CO₂ removal.^114,115 They further developed a water-stable fluorinated framework, NbOFFIVE-1-Ni (Fig. 11i), whose tailored pore size, geometry, and functionality enable energy-efficient removal of trace CO₂.

Thermal and hydrolytic stability remain central challenges for MOFs in practical DAC applications, particularly for high-performance materials containing open metal sites. Current mitigation strategies include the following: (i) employing high-valent metal clusters (e.g., Zr⁴⁺, Cr³⁺, Al³⁺ in UiO-66, MIL-101, and CAU-10) to strengthen metal–ligand bonds; (ii) introducing hydrophobic functionalities such as –CH₃, –F, or aromatic groups to repel water; and (iii) constructing core–shell architectures in which a water-resistant shell protects a CO₂-selective core.

3.4 COFs

COFs constitute a class of crystalline porous solids assembled exclusively from light elements (B, C, N, O, and H) through robust covalent linkages, affording precisely defined and tailorable pore architectures. In contrast to MOFs, the fully organic nature of COFs typically endows them with superior chemical and thermal stability, rendering them particularly attractive for CO₂ capture under chemically aggressive conditions, including the presence of water vapor and acidic components in flue gas streams. The modular design principle underlying COF synthesis enables atomic-level control over pore size, geometry, and chemical environment via the rational selection of organic building blocks, thereby allowing the deliberate construction of high-performance CO₂ sorbents. CO₂ uptake in COFs arises primarily from the combination of highly ordered pore channels and judicious framework functionalization.^116,117 Design strategies may be broadly categorized into those dominated by physisorption and those leveraging chemisorptive interactions. Precise tuning of pore dimensions is achieved by varying the length and symmetry of the monomers; in particular, COFs with pore apertures approaching the kinetic diameter of CO₂ (≈3.3 Å) maximize confinement effects and enhance host–guest interactions, leading to improved low-pressure adsorption capacities.¹¹⁸ Furthermore, the incorporation of polar functionalities into the framework, such as hydroxyl (–OH), ether (–O–), or triazine moieties, amplifies interactions with the quadrupolar CO₂ molecule via dipole–quadrupole forces, thereby increasing the Q_st and improving both selectivity and capacity.

Amino functionalization represents the most direct strategy to emulate the industrial amine scrubbing process within solid sorbents. In COFs, amine moieties can be incorporated either via postsynthetic modification, through grafting of amine-containing species onto the pore walls, or through direct synthesis using amine-bearing monomers. The resulting primary (–NH₂) and secondary (–NH–) amines reversibly react with CO₂ to form carbamate species, imparting high selectivity toward CO₂ capture.

In 2022, Yaghi and co-workers reported the first example of covalently anchoring aliphatic amines within a COF.¹¹⁹ The approach involved the crystallization of an indole-linked framework (COF-609, Fig. 12), followed by conversion of the indole linkage into a tetrahydroquinoline unit via an amine-driven Dresch–Adel-type ring-addition reaction across imine bonds, enabling the subsequent covalent attachment of tri(3-aminopropyl)amine. The resulting COF-609 exhibited a CO₂ uptake 1360-fold higher than that of the parent framework, with a further 29% enhancement under humid conditions.

Fig. 12 Covalent organic frameworks used for capturing CO₂ in the air. Reproduced with permission from ref. 119. Copyright 2022, the American Chemical Society.

In 2024, Yaghi and co-workers reported COF-999 (Fig. 13), which achieved a high CO₂ adsorption capacity of 2.05 mmol g⁻¹ at 50% relative humidity under ultra-dilute conditions (400 ppm CO₂) by embedding amine moieties within a hydrophobic crystalline scaffold composed of robust C–N and C–C linkages.¹²⁰ The superior DAC performance of this COF arises from rational molecular-level design. First, pore channels constructed from hydrophobic building units effectively suppress competitive adsorption by water vapor and substantially reduce the regeneration temperature; notably, COF-999 can be regenerated at 60 °C, with an energy requirement far lower than that of conventional DAC systems operating above 100 °C. Second, postsynthetic modification, such as the covalent attachment of amine initiators, enables the in situ formation of polyamines within the pores, thereby enhancing CO₂ affinity while preventing amine loss during cycling and maintaining stable performance over more than 100 adsorption–desorption cycles. Moreover, the high crystallinity and well-ordered pore architecture of COFs, exemplified by the olefin-linked framework of COF-999, provide efficient mass-transport pathways for CO₂ diffusion, while the fully organic composition imparts excellent chemical stability, allowing sustained capture performance under complex atmospheric conditions, including humidity fluctuations.

Fig. 13 COFs with good DAC performance. Reproduced with permission from ref. 120 and 121. Copyright 2024, the American Chemical Society and Springer Nature Group.

In 2024, Yaghi and co-workers developed a PEI-functionalized COF-709, which delivered efficient and stable CO₂ capture under ultra-dilute conditions (400 ppm CO₂) and high humidity.¹²¹ The synthesis of COF-709 exemplifies the integration of modular framework construction with postsynthetic modification. An imine-linked crystalline precursor (imin-COF-709) was first prepared via imine condensation, affording a porous, highly crystalline square lattice with AA stacking. Subsequent oxidation of the imine (C=N) linkages to more robust amide (O=C–N) bonds using aqueous NaClO₂ yielded amide-COF-709, markedly enhancing the chemical stability of the framework. Under NaOH catalysis, sulfur-containing branched PEI (SH-bPEI) was then covalently grafted onto the framework through aromatic nucleophilic substitution, forming stable C–S linkages. This covalent anchoring effectively suppresses amine volatilization and hydrolysis during cycling, thereby addressing the degradation issues commonly encountered in physically impregnated amine sorbents.

This stepwise strategy leverages the predictable crystal structure and high surface area of COFs to uniformly and permanently introduce active amine sites into hydrophobic pores. Under simulated DAC conditions (25 °C, 400 ppm CO₂), COF-709 exhibits a CO₂ uptake of 0.48 mmol g⁻¹ under dry conditions (0% RH), which increases to 1.24 mmol g⁻¹ at 75% RH, corresponding to a 2.58-fold enhancement. This humidity-promoted behavior is attributed to the participation of water in facilitating the formation of carbonic acid salts from amine–CO₂ reactions, thereby improving amine utilization efficiency. COF-709 also displays excellent cycling stability: PEI is covalently anchored via C–S bonds, preventing amine loss, while the intrinsic hydrophobicity of the organic framework mitigates moisture-induced degradation yet allows water to promote CO₂ capture. Owing to this structural robustness, complete CO₂ desorption is achieved at a regeneration temperature of only 95 °C, substantially lower than that required for many liquid amine systems (>100 °C) and certain MOFs. After 10 consecutive adsorption–desorption cycles under simulated DAC conditions (400 ppm CO₂, 75% RH, 25 °C), the CO₂ capacity remains unchanged at 1.23 mmol per g per cycle, confirming the outstanding durability of COF-709.

The design strategy embodied by COF-709 is complementary to that of the previously reported COF-999, with both materials representing state-of-the-art COF platforms for direct air capture yet addressing distinct performance priorities. COF-709 establishes the viability of integrating commercial PEI into a chemically robust COF scaffold via postsynthetic modification, enabling high amine loadings within a well-defined porous architecture that is readily compatible with existing amine-based capture chemistries. In contrast, COF-999 showcases the potential of directly constructing intrinsically stable alkene-linked COFs with built-in amine functionality, delivering more aggressive gains in adsorption capacity and cycling performance. Relative to conventional amine-loaded silicas and many MOFs, which commonly suffer from hydrolytic instability, amine volatilization, and high regeneration energy penalties, COF-709 and COF-999 effectively mitigate these limitations through strong covalent anchoring of polyamines and the creation of a hydrophobic pore environment.

4. Summary and outlook

Solid polymer-based sorbents have emerged as a central focus in the development of DAC sorbents owing to their structural tunability, functional diversity, and potential for cost-effective scalability. This review systematically highlights recent advances across diverse classes of polymer-based materials.

Organic polymers, benefiting from precise molecular and functional group design, have enabled efficient CO₂ capture while leveraging low-energy environmental fluctuations such as humidity to drive adsorption–desorption processes. These features position them as promising candidates for next-generation DAC systems with high selectivity, rapid response, and robust mechanical performance. Although many significant advancements have already been reported, many conventional polymeric sorbents lack continuous, interconnected pore networks, such that adsorbates, including gas molecules, ions, or organic contaminants, can access internal active sites only through slow bulk-phase diffusion. This transport process is typically associated with large energetic barriers and extended diffusion lengths, leading to sluggish adsorption kinetics and diminished overall performance. For instance, in desiccant composites or hydrogel-based adsorbents, the dense polymer matrix severely impedes the diffusion of water molecules, thereby limiting uptake rates.¹²²

At present, the most effective strategy for overcoming these mass-transport limitations is the rational engineering of pore architectures, primarily along two complementary dimensions. First, the construction of continuous, cross-linked pore networks affords low-barrier diffusion pathways that enable rapid sorbate transport, particularly under high-loading conditions where localized site saturation would otherwise precipitate sharp performance losses. Second, the incorporation of mesoporous templates, employing either soft templates such as surfactants or hard templates such as nanoparticles, allows the precise generation of mesostructures with tunable pore sizes. This approach yields hierarchical pore systems in which macropores and mesopores function as high-flux transport “highways”, while micropores furnish abundant adsorption sites, collectively minimizing internal diffusion distances and markedly enhancing sorption kinetics.¹²³

Polymer composites extend this versatility by integrating amino polymers with inorganic matrices (e.g., mesoporous silica) or carbon supports. Such hybrid architectures enhance mechanical stability and surface area, improving amine utilization via interfacial effects. This strategy provides a pathway to overcome the intrinsic limitations of single-component polymer sorbents. A persistent challenge is the mechanical degradation of polymer components within composite sorbents during repeated adsorption–desorption cycles, manifested as cracking or delamination from inorganic fillers. To enable practical scale-up and commercialization, several mitigation strategies are available. The incorporation of elastomeric polymer matrices or appropriate plasticizers can accommodate cyclic strain, whereas the establishment of robust covalent interfacial linkages, such as those formed using silane coupling agents (e.g., GPTES), provides substantially stronger adhesion than physical impregnation. In addition, the rational design of interpenetrating polymer networks or core–shell architectures offers a viable route to redistribute mechanical stress, thereby enhancing the structural integrity and long-term durability of the composites under operating conditions.⁹⁰

Crystalline porous materials, such as MOFs and COFs, represent the design frontier of DAC sorbents. Their exceptionally high surface areas, tunable pore architectures, and functionalizable pore environments provide a unique platform for tailoring CO₂ binding sites at the molecular level. In particular, the incorporation of unsaturated metal coordination sites or amine functionalities imparts strong affinity toward ultra-dilute CO₂. Nevertheless, the challenges, including the hydrolytic instability of MOFs and the large-scale synthesis and processing of COFs, remain critical barriers to their practical implementation.

Overall, various polymer-based DAC materials have achieved significant breakthroughs in adsorption capacity, selectivity, and stability. However, many common opportunities and challenges remain for the future.

(1) Low-molecular-weight amines, particularly PEI introduced via physical impregnation, are susceptible to volatilization and chemical degradation, including oxidative pathways and urea formation, during prolonged temperature-humidity swing cycling. These processes result in irreversible losses in effective sorption capacity, necessitating frequent sorbent replenishment or replacement and thereby increasing material consumption and operational costs. Moreover, amine volatilization poses risks of secondary environmental contamination. From a life-cycle assessment (LCA) perspective, these factors mandate explicit accounting of the resource and carbon burdens associated with amine synthesis, makeup, and potential volatile organic compound emissions. Strategies such as the covalent grafting of amines onto polymer backbones, the deployment of sterically hindered amines, and the use of solid amine precursors can substantially mitigate these liabilities and are central to improving sorbent sustainability. In addition, solvent production, recovery, and disposal constitute non-negligible environmental burdens that must be incorporated into LCA. Regeneration energy, particularly when relying on high-grade thermal inputs, typically dominates the operational carbon footprint of DAC systems. Accordingly, comparative evaluation of annual energy demands and associated emissions for distinct regeneration protocols, such as low-pressure steam stripping versus high-temperature inert-gas sweeping, is essential. Rational adsorbent design aimed at lowering regeneration temperatures and energy requirements is, therefore, a primary lever for enhancing overall environmental performance.¹²⁴

(2) Polymer-based sorbents may further suffer from mechanical attrition, pore collapse, or diminished structural integrity under repetitive swelling–deswelling cycles, thermal stress, and moisture exposure. Such degradation can increase bed pressure drop, impair mass transfer, and ultimately necessitate premature sorbent replacement. The resulting escalation in material consumption and solid-waste generation is reflected in elevated resource-depletion and waste-management impacts in LCA. Consequently, the development of mechanically robust polymer matrices, such as cross-linked networks or composite architectures incorporating porous carriers, is imperative for extending sorbent lifetime and minimizing life-cycle environmental burdens.¹²⁵

(3) The translation of polymeric sorbents from laboratory-scale powders or films into structured architectures compatible with practical DAC modules constitutes a pivotal step toward large-scale deployment. Polymer solutions can be uniformly deposited onto rigid or flexible supports, including metal foils, ceramic honeycombs, and polymeric textiles, to afford thin-film adsorption membranes that are readily scalable and provide efficient gas–solid interfacial contact. Thermoplastic sorbents, such as polysulfone- or partially cross-linked PEI-based composites, can be shaped into pellets or monolithic columns via melt extrusion or dry compaction, yielding materials with high mechanical integrity and low pressure drop that are suitable for fixed- or fluidized-bed configurations.⁸⁰ In parallel, solution or melt spinning enables the fabrication of nanometer- to micrometer-scale fibrous mats characterized by high specific surface areas, interconnected pore networks, and mechanical flexibility, all of which facilitate rapid gas diffusion and reversible adsorption–desorption cycling. An alternative strategy involves the impregnation or covalent grafting of functional polymers onto preformed three-dimensional porous scaffolds, including silica foams, activated carbon felts, and MOF monoliths, thereby synergistically combining the intrinsic selectivity of polymer sorbents with the structural robustness and favorable mass-transfer properties of the host matrices. A prominent example is PEI supported on mesoporous silica, which has been extensively implemented in pilot-scale DAC demonstrations.¹²⁶

(4) Conventional solvothermal syntheses of polymer-based DAC materials typically rely on large volumes of organic solvents, resulting in high production costs and nontrivial environmental burdens. The establishment of low-solvent or solvent-free manufacturing routes, including mechanochemical methods, vapor-phase deposition, and continuous-flow processes, represents a critical strategy for cost reduction. Notably, hydrothermal optimization of the UiO-66 family has enabled kilogram-scale production while preserving structural integrity, exemplifying the feasibility of scalable framework synthesis. Continuous-flow methodologies offer enhanced reaction efficiency, improved batch-to-batch reproducibility, and a practical foundation for downstream process scale-up. In parallel, modular synthetic concepts based on prefunctionalized monomers can streamline synthetic sequences and further improve material consistency. Recent demonstrations of self-supporting sorbents, including extruded CALF-20 particles and electrospun amine-functionalized polymer fibers, underscore the promise of extrusion moulding, three-dimensional printing, and electrospinning techniques, which obviate the need for inert binders that often compromise sorption performance.¹²⁷

(5) Dynamic, stimuli-responsive polymeric sorbents that reversibly modulate their adsorption–desorption behavior in response to external triggers such as light, electrical potential, humidity, or temperature constitute a particularly promising platform for minimizing regeneration energy requirements. Beyond conventional thermal swing adsorption (vacuum levels (<100 mbar) and temperature increase range (80–120 °C)),¹²⁸ sustainable regeneration strategies such as photothermal, electrochemical, microwave-assisted, or variable-humidity processes, particularly when coupled with renewable energy inputs (e.g., solar, geothermal), hold considerable promise for lowering energy intensity. For example, solar-driven photothermal regeneration can be realized by embedding carbon nanotubes, graphene, or plasmonic nanoparticles (e.g., Au or Cu) within polymer matrices, thereby enabling efficient conversion of incident solar radiation into localized thermal energy. This strategy affords rapid, mild-temperature CO₂ desorption and substantially reduces dependence on external heat sources. In a complementary approach, electrochemical regeneration harnesses renewable electricity to reversibly modulate the CO₂ affinity of polymer–carbon composite electrodes, such as conductive polymer/carbon nanotube systems, via applied potentials, enabling adsorption–desorption cycling with minimal energy input. Together, these material-enabled, energy-integrated regeneration schemes delineate a promising pathway toward low-energy, low-cost DAC operation, and recent demonstrations of photothermal and electrochemical desorption in polymer–carbon composites underscore their potential as next-generation DAC technologies.¹²⁹

In summary, the trajectory of polymer-based DAC materials is shifting from a singular focus on performance optimization toward intelligent design and scalable engineering applications. Through interdisciplinary integration of materials science, chemical engineering, artificial intelligence, and environmental science, continued innovation in both sorbent design and process development is expected to establish polymer-based DAC as an indispensable technology for achieving global carbon neutrality and addressing the challenges of climate change.

Conflicts of interest

The authors declare that there are no conflicts of interest regarding the publication of this manuscript.

Data availability

No primary research results, software or code have been included and no new data were generated or analysed as part of this review.

Acknowledgements

This work was financially supported by the Fund of Guangdong Provincial Key Laboratory of Luminescence from Molecular Aggregates (2023B1212060003).

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