Disclosing the Role of Defect-Engineered Metal–Organic Frameworks in Mixed Matrix Membranes for Efficient CO2 Separation: A Joint Experimental-Computational Exploration

Incorporation of defects in metal–organic frameworks (MOFs) offers new opportunities for manipulating their microporosity and functionalities. The so-called “defect engineering” has great potential to tailor the mass transport properties in MOF/polymer mixed matrix membranes (MMMs) for challenging separation applications, for example, CO₂ capture. This study first investigates the impact of MOF defects on the membrane properties of the resultant MOF/polymer MMMs for CO₂ separation. Highly porous defect-engineered UiO-66 nanoparticles are successfully synthesized and incorporated into a CO₂-philic crosslinked poly(ethylene glycol) diacrylate (PEGDA) matrix. A thorough joint experimental/simulation characterization reveals that defect-engineered UiO-66/PEGDA MMMs exhibit nearly identical filler–matrix interfacial properties regardless of the defect concentrations of their parental UiO-66 filler. In addition, non-equilibrium molecular dynamics simulations in tandem with gas transport studies disclose that the defects in MOFs provide the MMMs with ultrafast transport pathways mainly governed by diffusivity selectivity. Ultimately, MMMs containing the most defective UiO-66 show the most enhanced CO₂/N₂ separation performance—CO₂ permeability = 470 Barrer (four times higher than pure PEGDA) and maintains CO₂/N₂ selectivity = 41—which overcomes the trade-off limitation in pure polymers. The results emphasize that defect engineering in MOFs would mark a new milestone for the future development of optimized MMMs.     

Hydrogen‐Bonded Polyimide/Metal‐Organic Framework Hybrid Membranes for Ultrafast Separations of Multiple Gas Pairs

Membranes have seen a growing role in mitigating the extensive energy used for gas separations. Further expanding their effectiveness in reducing the energy penalty requires a fast separation process via a facile technique readily integrated with industrial membrane formation platforms, which has remained a challenge. Here, an ultrapermeable polyimide/metal‐organic framework (MOF) hybrid membrane is reported, enabling ultrafast gas separations for multiple applications (e.g., CO₂ capture and hydrogen regeneration) while offering synthetic enhanced compatibility with the current membrane manufacturing processes. The membranes demonstrate a CO₂ and H₂ permeability of 2494 and 2932 Barrers, respectively, with a CO₂/CH₄, H₂/CH₄, and H₂/N₂ selectivity of 29.3, 34.4, and 23.8, respectively, considerably surpassing the current Robeson permeability–selectivity upper bounds. At a MOF loading of 55 wt%, the membranes display a record‐high 16‐fold enhancement of H₂ permeability comparing with the neat polymer. With mild membrane processing conditions (e.g., a heating temperature less than 80 °C) and a performance continuously exceeding Robeson upper bounds for over 5300 h, the membranes exhibit enhanced compatibility with state‐of‐the‐art membrane manufacturing processes. This performance results from intimate interactions between the polymer and MOFs via extensive, direct hydrogen bonding. This design approach offers a new route to ultraproductive membrane materials for energy‐efficient gas separations.     

Self-Standing Covalent Organic Framework Membranes for H2/CO2 Separation

Covalent organic frameworks (COFs) are proposed as promising candidates for engineering advanced molecular sieving membranes due to their precise pore sizes, modifiable pore environment, and superior stability. However, COFs are insoluble in common solvents and do not melt at high temperatures, which presents a great challenge for the fabrication of COF-based membranes (COFMs). Herein, for the first time, a new synthetic strategy is reported to prepare continuous and intact self-standing COFMs, including 2D N-COF membrane and 3D COF-300 membrane. Both COFMs show excellent selectivity of H₂/CO₂ mixed gas (13.8 for N-COF membrane and 11 for COF-300 membrane), and especially ultrahigh H₂ permeance (4319 GPU for N-COF membrane and 5160 GPU for COF-300 membrane), which is superior to those of COFMs reported so far. It should be noted that the overall separation performance of self-standing COFMs exceeds the Robeson upper bound. Furthermore, a theoretical study based on Grand Canonical Monte Carlo (GCMC) simulation is performed to explain the excellent separation of H₂/CO₂ through COFMs. Thus, this facile preparation method will provide a broad prospect for the development of self-standing COFMs with highly efficient H₂ purification.     

Hydrogen Selective NH2‐MIL‐53(Al) MOF Membranes with High Permeability

Hydrogen‐based energy is a promising renewable and clean resource. Thus, hydrogen selective microporous membranes with high performance and high stability are demanded. Novel NH₂‐MIL‐53(Al) membranes are evaluated for hydrogen separation for this goal. Continuous NH₂‐MIL‐53(Al) membranes have been prepared successfully on macroporous glass frit discs assisted with colloidal seeds. The gas sorption ability of NH₂‐MIL‐53(Al) materials is studied by gas adsorption measurement. The isosteric heats of adsorption in a sequence of CO₂ > N₂ > CH₄ ≈ H₂ indicates different interactions between NH₂‐MIL‐53(Al) framework and these gases. As‐prepared membranes are measured by single and binary gas permeation at different temperatures. The results of singe gas permeation show a decreasing permeance in an order of H₂ > CH₄ > N₂ > CO₂, suggesting that the diffusion and adsorption properties make significant contributions in the gas permeation through the membrane. In binary gas permeation, the NH₂‐MIL‐53(Al) membrane shows high selectivity for H₂ with separation factors of 20.7, 23.9 and 30.9 at room temperature (288 K) for H₂ over CH₄, N₂ and CO₂, respectively. In comparison to single gas permeation, a slightly higher separation factor is obtained due to the competitive adsorption effect between the gases in the porous MOF membrane. Additionally, the NH₂‐MIL‐53(Al) membrane exhibits very high permeance for H₂ in the mixtures separation (above 1.5 × 10^?6 mol m^?2 s^?1 Pa^?1) due to its large cavity, resulting in a very high separation power. The details of the temperature effect on the permeances of H₂ over other gases are investigated from 288 to 353 K. The supported NH₂‐MIL‐53(Al) membranes with high hydrogen separation power possess high stability, resistance to cracking, temperature cycling and show high reproducibility, necessary for the potential application to hydrogen recycling.     

High‐Performance CO2 Capture through Polymer‐Based Ultrathin Membranes

Thin film composite (TFC) membranes have attracted great research interest for a wide range of separation processes owing to their potential to achieve excellent permeance. However, it still remains challenging to fully exploit the superiority of thin selective layers when mitigating the pore intrusion phenomenon. Herein, a facile and generic interface‐decoration‐layer strategy collaborating with molecular‐scale organic–inorganic hybridization in the selective layer to obtain a high‐performance ultrathin film composite (UTFC) membrane for CO₂ capture is reported. The interface‐decoration layer of copper hydroxide nanofibers (CHNs) enables the formation of an ultrathin selective layer (≈100 nm), achieving a 2.5‐fold increase in gas permeance. The organic part in the molecular‐scale hybrid material contributes to facilitating CO₂‐selective adsorption while the inorganic part assists in maintaining robust membrane structure, thus remarkably improving the selectivity toward CO₂. As a result, the as‐prepared membrane shows a high CO₂ permeance of 2860 GPU, superior to state‐of‐the‐art polymer membranes, with a CO₂/N₂ selectivity of 28.2. The synergistic strategy proposed here can be extended to a wide range of polymers, holding great potential to produce high‐efficiency ultrathin membranes for molecular separation.     

Metal Organic Framework Crystals in Mixed‐Matrix Membranes: Impact of the Filler Morphology on the Gas Separation Performance

Mixed‐matrix membranes comprising NH₂‐MIL‐53(Al) and Matrimid or 6FDA‐DAM have been investigated. The metal organic framework (MOF) loading has been varied between 5 and 20 wt%, while NH₂‐MIL‐53(Al) with three different morphologies, nanoparticles, nanorods, and microneedles has been dispersed in Matrimid. The synthesized membranes have been tested in the separation of CO₂ from CH₄ in an equimolar mixture. At 3 bar and 298 K for 8 wt% MOF loading, incorporation of NH₂‐MIL‐53(Al) nanoparticles leads to the largest improvement compared to nanorods and microneedles. The incorporation of the best performing filler, i.e., NH₂‐MIL‐53(Al) nanoparticles, into the highly permeable 6FDA‐DAM has a larger effect, and the CO₂ permeability increases up to 85% with slightly lower selectivities for 20 wt% MOF loading. Specifically, these membranes have a permeability of 660 Barrer with a CO₂/CH₄ separation factor of 28, leading to a performance very close to the Robeson limit of 2008. Furthermore, a new non‐destructive technique based on Raman spectroscopy mapping is introduced to assess the homogeneity of the filler dispersion in the polymer matrix. The MOF contribution can be calculated by modeling the spectra. The determined homogeneity of the MOF filler distribution in the polymer is confirmed by focused ion beam scanning electron microscopy analysis.     

Synergistic CO2‐Sieving from Polymer with Intrinsic Microporosity Masking Nanoporous Single‐Layer Graphene

High‐flux nanoporous single‐layer graphene membranes are highly promising for energy‐efficient gas separation. Herein, in the context of carbon capture, a remarkable enhancement in the CO₂ selectivity is demonstrated by uniquely masking nanoporous single‐layer graphene with polymer with intrinsic microporosity (PIM‐1). In the process, a major bottleneck of the state‐of‐the‐art pore‐incorporation techniques in graphene has been overcome, where in addition to the molecular sieving nanopores, larger nonselective nanopores are also incorporated, which so far, has restricted the realization of CO₂‐sieving from graphene membranes. Overall, much higher CO₂/N₂ selectivity (33) is achieved from the composite film than that from the standalone nanoporous graphene (NG) (10) and the PIM‐1 membranes (15), crossing the selectivity target (20) for postcombustion carbon capture. The selectivity enhancement is explained by an analytical gas transport model for NG, which shows that the transport of the stronger‐adsorbing CO₂ is dominated by the adsorbed phase transport pathway whereas the transport of N₂ benefits significantly from the direct gas‐phase transport pathway. Further, slow positron annihilation Doppler broadening spectroscopy reveals that the interactions with graphene reduce the free volume of interfacial PIM‐1 chains which is expected to contribute to the selectivity. Overall, this approach brings graphene membrane a step closer to industrial deployment.     

Ultrathin ionic COF Membrane via Polyelectrolyte-Mediated Assembly for Efficient CO2 Separation

Fabricating ultrathin covalent organic framework (COF) membranes toward high-permeance molecular separations is highly desired yet challenging. Herein, a polyelectrolyte-mediated assembly (PMA) strategy is developed to fabricate ultrathin ionic COF membrane for efficient CO₂ separation. The PMA strategy allows a facile control over the assembly mode between polyethyleneimine (PEI) and TpPa-SO₃H, yielding PEI-bridged ultra-large COF nanosheets which are readily processed into COF membranes with thickness down to 8 nm. The resulting COF membranes exhibit a high CO₂ permeances of 1371 GPU and CO₂/N₂ selectivity of 33 for stimulated flue gas. This PMA strategy may open up a new avenue to fabricating ultrathin 2D material membranes for diverse applications.     

Highly CO2 Selective Metal–Organic Framework Membranes with Favorable Coulombic Effect

The topology and chemical functionality of metal–organic frameworks (MOFs) make them promising candidates for membrane gas separation; however, few meet the criteria for industrial applications, that is, selectivity of >30 for CO₂/CH₄ and CO₂/N₂. This paper reports on a dense CAU-10-H MOF membrane that is exceptionally CO₂-selective (ideal selectivity of 42 for CO₂/N₂ and 95 for CO₂/CH₄). The proposed membrane also achieves the highest CO₂ permeability (approximately 500 Barrer) among existing pure MOF membranes with CO₂/CH₄ selectivity exceeding 30. State-of-the-art atomistic simulations provide valuable insights into the outstanding separation performance of CAU-10-H at the molecular level. Adsorbent–adsorbate Coulombic interactions are identified as a crucial factor in the design of CO₂-selective MOF membranes.     

Basic Alkylamine Functionalized PAF-1 Hybrid Membrane with High Compatibility for Superior CO2 Separation from Flue Gas

Functionalized porous aromatic frameworks (PAFs) are excellent candidate materials for hybrid membrane fabrication. However, tailoring PAFs for membrane CO₂ separation with desirable performance is still a challenge. Here, facile fabrication of functional hybrid alkylamine-modified PAF-1 containing membranes with high compatibility for efficient CO₂/N₂ separation is reported. The methylamino groups are installed on PAF-1 resulting in PAF-1-CH₂NH₂ that has a high surface area of over 1400 m² g^–1 and unique CO₂ adsorption with CO₂/N₂ thermodynamic selectivity of over 1000. Amidation reaction is developed for PAF-1-CH₂NH₂ cross linking with cPIM-1 (carboxylic polymer of intrinsic microporosity), giving a homogenous compatible membrane of PAF-1-CH₂NH₂—cPIM-1 with outstanding CO₂ permeability (≈10790 Barrer) and high CO₂/N₂ permselectivity (≈43). This membrane outperforms the counterparts derived from parent PAF-1 and phenylamine PAF-1 and possesses superior performance to other relevant membranes for CO₂/N₂ separation. Such a membrane can selectively and stably separate CO₂ from N₂ in a simulated flue gas mixture, demonstrating its huge potential in carbon capture.     

Designing Defective Crystalline Carbon Nitride to Enable Selective CO2 Photoreduction in the Gas Phase

Polymeric carbon nitrides are promising photocatalysts for CO₂ photoreduction, but still show lower activity and selectivity. Herein, the synthesis of an ordered crystalline carbon nitride is reported which is simultaneously rich in special defects, accomplished via the co‐condensation of guanidine hydrochloride and dicyandiamide under acetonitrile‐promoted solvothermal conditions. The high crystallinity boosts charge migration, and the structural terminations with cyano and carboxyl groups result in the improvement of optical absorption, the ability to store charges at the surface, and CO₂ binding. The crystalline carbon nitride with surface defect design enables the effective gas‐phase CO₂ photoreduction into hydrocarbon fuels while oxidizing water to oxygen, at a rate of 12.07 µmol h^?1 g^?1 and a selectivity of 91.5%, both values of which are remarkably higher than those of most previous carbon nitride photocatalysts. This study highlights the preparation of defective crystalline carbon nitride using a low‐temperature solvothermal synthesis, as well as a resultant good selectivity toward hydrocarbons in the application of gas‐phase CO₂ photoreduction in the absence of any cocatalyst or sacrificial agent.     

2D MXene Nanofilms with Tunable Gas Transport Channels

2D materials' membranes with well‐defined nanochannels are promising for precise molecular separation. Herein, the design and engineering of atomically thin 2D MXene flacks into nanofilms with a thickness of 20 nm for gas separation are reported. Well‐stacked pristine MXene nanofilms are proven to show outstanding molecular sieving property for H₂ preferential transport. Chemical tuning of the MXene nanochannels is also rationally designed for selective permeating CO₂. Borate and polyethylenimine (PEI) molecules are well interlocked into MXene layers, realizing the delicate regulation of stacking behaviors and interlayer spacing of MXene nanosheets. The MXene nanofilms with either H₂‐ or CO₂‐selective transport channels exhibit excellent gas separation performance beyond the limits for state‐of‐the‐art membranes. The mechanisms within these nanoconfined MXene layers are discussed, revealing the transformation from “diffusion‐controlled” to “solution‐controlled” channels after chemical tuning. This work of precisely tailoring the 2D nanostructure may inspire the exploring of nanofluidics in 2D confined space with applications in many other fields like catalysis and energy conversion processes.     

Covalent Organic Framework Hosting Metalloporphyrin‐Based Carbon Dots for Visible‐Light‐Driven Selective CO2 Reduction

The visible‐light‐driven photocatalytic CO₂ reduction is one appealing approach to simultaneously mitigate the energy crisis and environmental issues. It is highly desirable but challenging to selectively and efficiently convert CO₂ into desirable products. Herein, a covalent organic framework hosting metalloporphyrin‐based carbon dots (M‐PCD@TD‐COF, M = Ni, Co, and Fe) is first presented, which serves as heterogeneous catalysts for CO₂ photoreduction. M‐PCD@TD‐COF not only enriches available COF‐based catalytic materials, but also provides suitable environment for CO₂ adsorption and activation on metalloporphyrin‐based carbon dots. The advantages of the host environment in COFs are highlighted by the satisfactory catalytic activity and remarkable selectivity of CO₂‐to‐CO conversion over H₂ generation up to 98%. The photocatalytic system is effective for both pure CO₂ and the simulated flue gas. This work provides new protocols for the rational design of COF‐based heterogeneous catalysts for selective CO₂ photoreduction.     

Negative Charge Confined Amine Carriers within the Nanowire Network for Stable and Efficient Membrane Carbon Capture

Membrane‐based carbon dioxide (CO₂) capture has attracted great research interest owing to its potential for higher separation efficiency and lower energy consumption. However, it is still a challenging task to capture CO₂ with membrane from flue gas, especially under moderate‐temperature and high‐humidity conditions. In this work, a stable CO₂‐selective membrane that can operate at temperatures up to 90 °C and under high humidity is reported. The positively charged amine carriers for CO₂ are confined within the negatively charged polymer modified carbon nanotube (CNT) network. In this structure, interconnected CNTs act as the framework for the selective layer and provide numerous nanochannels for gas transport. The negatively charged polymer ensures the carrier stability and further regulates the size of nanochannels in the CNT network. By virtue of carrier‐facilitated transport, high CO₂ permeance (up to 3300 gas permeation units) and high CO₂/N₂ selectivity (400) are achieved under simulated flue gas conditions. Moreover, theoretical calculations verify that the stable separation performance is due to the strong electrostatic interaction between the amine carriers and polymer matrix. The high performance and good stability indicate the great potential of this novel membrane structure for practical application in CO₂ capture.     

Nanostructured Poly(styrene‐b‐butadiene‐b‐styrene) (SBS) Membranes for the Separation of Nitrogen from Natural Gas

The preparation and characterization of new, tailor‐made polymeric membranes using poly(styrene‐b‐butadiene‐b‐styrene) (SBS) triblock copolymers for gas separation are reported. Structural differences in the copolymer membranes, obtained by manipulation of the self‐assembly of the block copolymers in solution, are characterized using atomic force microscopy, transmission electron microscopy, and the transport properties of three gases (CO₂, N₂, and CH₄). The CH₄/N₂ ideal selectivity of 7.2, the highest value ever reported for block copolymers, with CH₄ permeability of 41 Barrer, is obtained with a membrane containing the higher amount of polybutadiene (79 wt%) and characterized by a hexagonal array of columnar polystyrene cylinders normal to the membrane surface. Membranes with such a high separation factor are able to ease the exploitation of natural gas with high N₂ content. The CO₂/N₂ ideal selectivity of 50, coupled with a CO₂ permeability of 289 Barrer, makes SBS a good candidate for the preparation of membranes for the post‐combustion capture of carbon dioxide.     

Solubility-Boosted Molecular Sieving-Based Separation for Purification of Acetylene in Core–Shell IL@MOF Composites

Considering the small amount of CO₂ as a contaminant in industrial gas mixtures, developing CO₂-selective adsorbents exhibit advantages in directly obtaining pure C₂H₂ in one-step to reduce the energy consumption. However, it is still a great challenge due to the essential molecular feature of C₂H₂, including the triple bond and high polarizability. Herein, a simple but effective CO₂-facilitated transport strategy is presented to realize the overwhelming adsorption of CO₂ over C₂H₂ by constructing core–shell composite structures using ionic liquid (IL) and metal-organic framework (MOF). With the aid of excellent solubility of CO₂ in IL and almost total exclusion of C₂H₂, the obtained materials boost molecular sieving-based separation of CO₂/C₂H₂. Density functional theory calculations combining molecular dynamic simulations revealed the solution-diffusion mechanism for CO₂, which is rarely reported in solid adsorbents. Ideal adsorbed solution theory selectivity for CO₂/C₂H₂ with 1/1 and 1/3 volume ratios can reach over 10⁴ and 4000 at 100 kPa with a high CO₂ uptake of 40.3 cm³ g⁻¹, superior to those of the reported materials so far. More importantly, this solution-based separation strategy can avoid the difficulty for precise control of the regulation of adsorbent structure, which may be beneficial to practical production.     

Nanoconfined Molecular Catalysts in Integrated Gas Diffusion Electrodes for High-Current-Density CO2 Electroreduction

Molecular catalysts are promising catalysts to electrochemically convert CO₂ into CO with high selectivity. However, achieving industrial-level current density remains challenging due to the limitation of charge- and mass-transport in gas diffusion electrode. Herein, a novel gas diffusion electrode architecture by confining highly dispersed cobalt(II) phthalocyanine (CoPc) molecules into -graphene oxide (GO) nanosheets (denoted as CoPc@GO) is designed. Benefiting from the accelerated CO₂ diffusion and charge transport in the nanoconfined structure, the designed electrode achieves a high CO partial current density of 481.65 ± 12.50 mA cm⁻² and a cathode energy efficiency over 64% for CO. The experimentally measured CO₂ transport dynamics and molecular dynamics simulation confirm the accelerated CO₂ diffusion, while theoretical calculations reveal the decreased energy barrier of the CO₂ activation in the confined space. This study paves a new way for electrode architecture design that would accelerate the implementation of CO₂ electrolysis technology.     

Submicrometer‐Sized ZIF‐71 Filled Organophilic Membranes for Improved Bioethanol Recovery: Mechanistic Insights by Monte Carlo Simulation and FTIR Spectroscopy

Template‐free self‐assembly synthesis of nano‐sized metal‐organic frameworks (MOFs) is of particular interest in MOF research since organized nanostructures possessing distinctive properties are useful for many advanced applications. In this work, the facile room temperature synthesis of robust submicrometer‐sized ZIF‐71 crystals with different particle sizes (140, 290, or 430 nm), having a high permanent microporosity (S_BET = 827 cm² g^?1) and synthesis yield up to 80% based on Zn on a gram‐scale, is reported. These small ZIF‐71 particles are ideal filler for the fabrication of thinner and homogeneous polydimethylsiloxane (PDMS) based mixed matrix membranes (MMMs) with excellent filler dispersion and filler‐polymer adhesion at high loading up to 40 wt%, as confirmed by scanning electron microscopy. Pervaporation tests using these submicrometer‐sized ZIF‐71 filled MMMs show significant improvement for bioethanol recovery. Interesting phenomena of i) reversible ethanol‐ethanol hydrogen interaction in the ethanol liquid‐phase and ii) irreversible hydrogen interaction of ethanol and –Cl functional group in the α‐cages and octagonal prismatic cages of ZIF‐71 in ethanol vapor‐phase are discovered for the first time by a Fourier transform infrared spectroscopy (FTIR) study. In full agreement with molecular simulation results, these explain fundamentally the ZIF‐71 filled MMMs pervaporation performance.     

New-Generation Anion-Pillared Metal–Organic Frameworks with Customized Cages for Highly Efficient CO2 Capture

The rational design of porous materials for CO₂ capture under realistic process conditions is highly desirable. However, trade-offs exist among a nanopore's capacity, selectivity, adsorption heat, and stability. In this study, a new generation of anion-pillared metal-organic frameworks (MOFs) are reported with customizable cages for benchmark CO₂ capture from flue gas. The optimally designed TIFSIX-Cu-TPA exhibits a high CO₂ capacity, excellent CO₂/N₂ selectivity, high thermal stability, and chemical stability in acid solution and acidic atmosphere, as well as modest adsorption heat for facile regeneration. Additionally, the practical separation performance of the synthesized MOFs is demonstrated by breakthrough experiments under various process conditions. A highly selective separation is achieved at 298–348 K with the impressive CO₂ capacity of 2.1–1.4 mmol g⁻¹. Importantly, the outstanding performance is sustained under high humidity and over ten repeat process cycles. The molecular mechanism of MOF's CO₂ adsorption is further investigated in situ by CO₂ dosed single crystal structure and theoretical calculations, highlighting two separate binding sites for CO₂ in small and large cages featured with high CO₂ selectivity and loading, respectively. The simultaneous adsorption of CO₂ inside these two types of interconnected cages accounts for the high performance of these newly designed anionic pillar-caged MOFs.     

Solvent‐Mediated Reconstruction of the Metal–Organic Framework HKUST‐1 (Cu3(BTC)2)

The principle of integral metal–organic framework (MOF) reconstruction is demonstrated for differently degraded HKUST‐1 via a facile, one‐step, solvent‐assisted treatment. Controlled MOF degradation by exposure to 77% humidity, liquid water, and diluted hydrochloric acid produces a mixture of non‐porous crystalline hybrid materials containing protonated linker and copper‐oxo species, which are then reconstructed back into high‐quality HKUST‐1 by contacting them with ethanol. X‐ray diffraction and sorption kinetics reveal a true memory effect of the system from completely degraded materials. The reconstruction approach is consequently extrapolated to gas‐ and liquid‐phase treatments in a fixed‐bed reactor with ethanol and ethanol/water mixtures for use in CO₂ capture from a simulated pre‐combustion gas stream. Up to a maximum of 94% porosity and 85% CO₂ sorption capacity can be recovered from a steamed material. A degradation‐reconstruction model is put forward based on X‐ray diffraction observations and structural analyses, microscopy, N₂ sorption, thermogravitry–mass spectrometry and IR spectroscopy observations, particularly elucidating the influence of various degradation pathways on the reconstruction.