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Covalent organic frameworks (COFs), at the forefront of porous materials, hold tremendous potential in membrane separation; however, achieving high continuity in COF membranes remains crucial for efficient gas separation. Here, we present a unique approach termed assembly‐dissociation‐reconstruction for fabricating COF membranes tailored for CO2/N2 separation. A parent COF is designed from two‐node aldehyde and three‐node amine monomers and dissociated to high‐aspect‐ratio nanosheets. Subsequently, COF nanosheets are orderly reconstructed into a crack‐free membrane by surface reaction under water evaporation. The membrane exhibits high crystallinity, open pores and a strong affinity for CO2 adsorption over N2, resulting in CO2 permeance exceeding 1060 GPU and CO2/N2 selectivity surpassing 30.6. The efficacy of this strategy offers valuable guidance for the precise fabrication of gas‐separation membranes. [ABSTRACT FROM AUTHOR]

Polymer-based membrane separation technology is gaining popularity due to its cost-effectiveness and operational simplicity. Cellulose acetate (CA) stands out as an attractive biobased polymer for membrane applications due to its remarkable mechanical properties and ease of manufacturing. To improve the selectivity of CA-based membranes for carbon dioxide (CO2) separation, the incorporation of polyethylene glycol methyl ether acrylate (PEGMEA), known for its CO2 absorption properties, has emerged as a promising approach for creating high-performance membrane materials with low operating pressure. This study provides insight into the production of PEGMEA-grafted CA membranes via gamma radiation and their performance for CO2/CH4 gas separation. CO2 permeation of the obtained CA-PEGMEA membranes was successfully improved and achieved the desired selectivity for CO2/CH4 separation. A comprehensive study of the membrane properties was conducted, encompassing structural characterization, surface analysis, permeability, selectivity, thermal analysis, and crystallinity, which are essential for understanding and assessing the membrane's performance. This work emphasizes gamma radiation graft polymerization and shows its applicability for high-performance gas separation membrane materials. [ABSTRACT FROM AUTHOR]

Ionic liquid (IL)/metal–organic framework (MOF) (IL/MOF) nanocomposites have been shown to offer a broad potential in adsorption-based CO2 separation, especially at very low pressures. Selection of the most suitable ILs is crucial for synthesizing IL/MOF nanocomposites capable of achieving exceptionally high CO2 selectivities under more applicable conditions, such as at atmospheric pressure. However, the existence of a very wide range of IL-MOF pairs makes the design of such materials time-consuming when relying solely on experimental approaches. In this work, we employed a multitiered computational approach involving conductor-like screening model for realistic solvents, grand canonical Monte Carlo simulations, and density functional theory calculations. The goal was to screen 35,476 diverse ILs from various families to identify the IL that could boost the CO2 selectivity. Results of the computational screening highlighted 1-n-butyl-3-methylimidazolium tricyanomethanide ([BMIM]-[C-(CN)3]) as the promising IL candidate offering significant potential for separation of CO2 from N2 and CH4. We then experimentally incorporated this IL into a robust MOF, UiO-66, and characterized the resulting structure in deep detail. Testing of [BMIM]-[C-(CN)3]/UiO-66 for adsorption of CO2, N2, and CH4 demonstrated that the nanocomposite provides exceptional CO2 separation performance, offering an appreciable amount of CO2 uptake, while almost completely rejecting N2 and CH4 up to 1 and 0.3 bar, respectively, at 25 °C. Our results illustrated the importance of accurate selection of the IL for the design of IL/MOF nanocomposites with high performance for target gas separations. [ABSTRACT FROM AUTHOR]

Robust high‐valence metal–organic framework (MOF) membranes for CO2 separations show great promise for achieving carbon neutrality. Herein, the elegant fabrication of tetravalent zirconium Materials of Institute Lavoisier‐140A (MIL‐140A) membranes are pioneered and validated the intriguing dual role for both CO2‐selective and CO2‐rejective separations by combining structural regulation with the exploitation of the appropriate anisotropic ultramicropores. This inimitable separation ability of "hitting two targets with one arrow" with distinctive molecular size cut‐offs, which originated from the significant orientation transformation, enables the membranes to satisfy multiscenario CO2 capture requirements. The preferred (h0h)‐oriented MIL‐140A membranes exhibit superior mixed CO2/CH4 separation capacities (a separation factor of ≈30), while the highly (200)‐oriented MIL‐140A membranes exhibit remarkable mixed H2/CO2 separation capacities (a separation factor of ≈540), and they both ranked at the top among the present MOF membranes. This work highlights the promising prospects of the fresh MIL‐140 series for a given membrane‐based multiscenario CO2 separation application through microstructure customization and manipulation. [ABSTRACT FROM AUTHOR]

This study employed modified graphitic carbon nitride (g‐C3N4) nanosheets and polyether block amide (Pebax) to prepare mixed matrix membranes (MMMs) aiming to enhance CO2 separation efficiency. Through sulfonation and zinc ion (Zn2+) modification of g‐C3N4 nanosheets, high Zn2+ loaded nanofillers (SCN‐Zn2+) were synthesized. Compared to g‐C3N4, MMMs with SCN‐Zn2+ as nanofiller showed a CO2 permeance of 462 Barrer as well as the CO2/N2 selectivity of 47.5 at the feed gas pressure of 2 bar, which surpassed the 2008 Robeson upper bound. Additionally, the Pebax/SCN‐Zn2+(30) membrane was subjected to continuous gas permeability experiments for 70 h and showed good stability. The results showed that SCN‐Zn2+ nanosheets played an important role in enhancing the gas selectivity of the membranes. SEM confirmed that the SCN‐Zn2+ nanosheets had good compatibility with the Pebax substrate and the presence of hydrophilic sulfonic acid groups effectively suppressed the interfacial defects. The increase in the free volume fraction of the membranes as well as the solubility and diffusion coefficient suggested that the introduction of g‐C3N4 nanosheets led to more tortuous gas transport paths, which enhanced the permeability and selectivity of CO2. [ABSTRACT FROM AUTHOR]

This study investigated the effect of different synthesis parameters including pre- and post-hydrothermal treatment on the formation of a high-quality SSZ-13 membrane layer. The membranes were identified initially by the gas tightness test, then were characterized by single gas permeation measurements applying H2, He, CO2, N2, CH4, and SF6 at room temperature. The results showed how each parameter affects the performance of the membrane, including structural defects in the formed selective layer, CO2 permeance, and the ideal CO2/CH4 permselectivity. This work focused on optimizing these parameters. An ideal CO2/CH4 permselectivity of up to 122 with CO2 permeance of ~3.72 × 10−6 [mol/(m2sPa)] and CO2/CH4 selectivity of 111 with CO2 permeance of 8.5 × 10−7 [mol/(m2sPa)] in an equimolar mixture at room temperature and pressure drop of 0.15 MPa was achieved. This is one of the highest performances compared to other publications for SSZ-13 or all-Si membranes. [ABSTRACT FROM AUTHOR]

Carbon emission reduction has been accepted as a common concern all over the world. Currently, CO2 emission is mainly derived from the consumption of fossil fuels. To solve this issue, there is an urgent need to develop technologies for CO2 capture. The utilization of membrane technology to remove CO2 from a mixture gas attracts great interest. In the present work, poly(2-hydroxyethyl methacrylate-co-vinylamine) was synthesized by polymerization (n-vinyl formamide and 2-hydroxyethyl methacrylate), hydrolysis, and ion exchange. The surface function of graphene oxide was carried out by aerobic self-polymerization of dopamine. The mixed matrix membranes were fabricated by adding the nanofiller (before and after modification) into the polymeric matrix. The membrane properties and its structure were characterized by FTIR, TGA, XRD, and SEM. The effect of nanofiller content and operation conditions on membrane performance was investigated. Results showed that the additions of nanofiller could decrease the crystallization of these membranes and effectively improve gas permeance. Remarkably, for the addition of 2.0 wt% dopamine-modified graphene oxide, the CO2 permeance of the membrane was increased by 30.9% while achieving a CO2/N2 selectivity of 83.5. The CO2 permeation for CO2/CH4 was also increased by 16.77%. These were surpassed over the 2008 Robeson's upper bound. These resultant membranes demonstrated attractive potential for low-pressure post-combustion CO2 capture. Besides, the stability of longtime tests on membranes was studied, and it was observed that membranes exhibited excellent stabilization with continuously operated for 220 h. The excellent properties of these membranes provide new opportunities for gas separation applications. [ABSTRACT FROM AUTHOR]

Development of high-performance CO2 separation membrane materials is the most vital challenge in membrane separation technology for carbon emission reduction and carbon neutrality. Mixed matrix membranes (MMMs) were prepared using polyether-block-polyamide (Pebax-1074) as the membrane matrix and multi-walled carbon nanotubes (MWCNTs) as the filler. The morphology, microstructure, surface functional groups, and thermal properties of the MMMs were characterized by scanning electron microscope, X-ray diffraction, infrared spectroscopy, and thermogravimetric analysis, respectively. The effects of MWCNTs content, permeation temperature, and permeation pressure on the microstructure and gas separation properties of the prepared MMMs were investigated. The results show that the microstructure and the gas separation performance of the membrane can be significantly regulated through varying the content of MWCNTs. The optimal separation performance is attained to 291.4 Barrer of CO2 permeability and 160.2 of CO2/N2 selectivity for the MMMs containing 12% MWCNTs under the condition of 30 °C and 0.2 MPa. The exceptional separation performance is far beyond the commercially attractive Robeson upper-bound. [ABSTRACT FROM AUTHOR]

Defect‐engineered metal–organic frameworks (MOFs) with outstanding structural and chemical features have become excellent candidates for specific separation applications. The introduction of structural defects in MOFs as an efficient approach to manipulate their functionality provides excellent opportunities for the preparation of MOF‐based mixed matrix membranes (MMMs). However, the use of this strategy to adjust the properties and develop the separation performance of gas separation membranes is still in its early stages. Here, a novel defect‐engineered MOF (quasi ZrFum or Q‐ZrFum) was synthesized via a controlled thermal deligandation process and incorporated into a CO2‐philic 6FDA‐durene polyimide (PI) matrix to form Q‐ZrFum loaded MMMs. Defect‐engineered MOFs and fabricated MMMs were investigated regarding their characteristic properties and separation performance. The incorporation of defects into the MOF structure increases the pore size and provides unsaturated active metal sites that positively affect CO2 molecule transport. The interfacial compatibility between the Q‐ZrFum particles and the PI matrix increases via the deligandation process, which improves the mechanical strength of Q‐ZrFum loaded membranes. MMM containing 5 wt.% of defect‐engineered Q‐ZrFum exhibits excellent CO2 permeability of 1308 Barrer, which increased by 99 % compared to the pure PI membrane (656 Barrer) at a feed pressure of 2 bar. CO2/CH4 and CO2/N2 selectivity reached 44 and 26.6 which increased by about 70 and 16 %, respectively. This study emphasizes that defect‐engineered MOFs can be promising candidates for use as fillers in the preparation of MMMs for the future development of membrane‐based gas separation applications. [ABSTRACT FROM AUTHOR]

Biogas can be a viable solution for replacing the conventional fuel for reducing pollution. However, the high CO2 content in biogas must be removed for its utilization. In this study, biogas purification is carried out employing cellulose nanocrystals (CNC)/polyvinyl alcohol (PVA) “selective layered” polysulfone hollow fiber membrane. The membrane chamber is designed such that the cross-flow of the biogas can be ensured for the effective interaction of the biogas with membrane surface. From various characterization tools like field emission scanning electron microscope, FTIR, X-ray diffraction, moisture absorption and tensile test, CNC1/PVA (1 wt% of CNC in PVA) nanocomposite film demonstrated optimum crystallinity and mechanical strength while retaining higher moisture absorption. The average selective layer thickness at this CNC concentration is 1169 nm. CO2 permeability of 17,858 barrer and the selectivity of 19 for CO2 over CH4 is observed, respectively. [ABSTRACT FROM AUTHOR]

Carbon dioxide (CO2) is a greenhouse gas which is mainly found in natural gas (NG), biogas, and flue gas. Anthropogenic CO2 emissions are the direct result of burning fossil fuels. Meanwhile, pre‐ and postcombustion CO2 separation is a current state of CO2 removal method in an extensive manner. From environmental, economic, and transportation perspectives, removal of CO2 has driven the development of its separation process technology. Among the reported technologies, membrane‐based gas separation technologies have grown substantially, breakthroughs and advances in past decades. This review paper aims to provide an overview on competitive gas separation processes, different types of membranes available, gas transport mechanisms, and fabrication process of hollow fiber membranes, particularly dual‐layer hollow fiber membrane. The performance of the membranes in CO2 separation and effect of spinning parameters on the formation of hollow fiber membranes are highlighted. In addition, approaches to improve the dual‐layer adhesion, strategies to enhance the filler compatibility in the development of dual‐layer hollow fiber mixed‐matrix membranes, and effect of post‐treatments on the gas separation performance of membrane are also discussed. Finally, challenges and future perspectives of dual‐layer hollow fiber mixed‐matrix membranes toward CO2 capture, particularly on CO2/CH4 and CO2/N2 separation, are also included, due to its substantial and direct relevance to the gas separation industry. [ABSTRACT FROM AUTHOR]

Mixed matrix membranes (MMMs) have been proposed as a solution to surmount Robeson's trade‐off curves and have demonstrated efficacy in gas separation processes, particularly for CO2 capture. In this study, MMMs based on Pebax®1657 were obtained utilizing synthetic silico‐metallic mineral particles (SSMMP) functionalized with ionic liquids (ILs). The objective was to attain enhanced CO2 separation performance, thereby showcasing the potential to mitigate the environmental repercussions of industrial processes that entail greenhouse gas emissions. For membrane production, an ethanol/water mixture was used as solvent, with the SSMMP/IL content varying from 0.5 to 20% by weight of the polymer. The primary aim of this study was to assess the effect of filler addition on permeability and selectivity for CO2, CH4, and N2. Comprehensive analyses, including SEM, FTIR, TGA, DSC, and DMA were conducted to evaluate the properties of the produced membranes. Gas permeability and ideal selectivity were measured at 25°C and different pressures, ranging from 1 to 7 bar. Characterization results demonstrate that the glass transition temperature (Tg) of MMMs increased compared to pure Pebax®1657, indicating that the addition of SSMMP/IL reduces the flexibility of the PEO chains, forming a rigid interface at the polymer/filler, which may enhance selectivity. This effect, corroborated by gas permeation, was observed for both CO2/N2 and CO2/CH4. For CO2/N2, the highest selectivity was achieved at lower filler concentrations, gradually decreasing as the filler load increased. MMM‐0.5 wt% achieved the highest selectivity of 91.96. The membrane CO2 permeability rose with an elevated filler content, rising from 84.21 for pure Pebax®1657 to 192.17 Barrer for MMM‐20 wt% at 4 bar. The permeability results were influenced by the gas diffusion coefficients of the MMMs, which increased with increasing SSMMP/IL content. The effect of feed pressure on MMM‐5 wt% was also assessed, revealing that CO2 permeability increased with increasing pressure, from 126.72 Barrer at 1 bar to 165.56 Barrer at 7 bar. This work showcased the viability of MMMs incorporating SSMMP/IL for industrial use, as they displayed separation capabilities that exceeded the 2008 Robeson upper bound. Highlights: Mixed matrix membranes based on Pebax®1657 and SSMMP‐20%‐[bmim][Tf2N] were prepared.CO2 permeability of the MMMs was increased by 128% and CO2/N2 selectivity by 83%.Higher CO2 pressures increase MMMs permeability.The obtained MMMs have separation performances above the Robeson upper Bound. [ABSTRACT FROM AUTHOR]

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used to analyze poly(ether ether ketone) (PEEK) based membranes. PEEK membranes have been shown to be effective in the separation of CO2 from flue gases (post-combustion technique). The PEEK membranes were synthesized using novel aromatic ether-ketone linkages inspired by PEEK with polymeric backbone bistriflimide [Tf2N]− counterions. One of the keys to advancing this technology is developing membranes that are selective and permeable toward CO2, in which PEEK based membranes have been shown to be. Furthermore, the compatibility between various water lean solvents also needs to be investigated. Surface analytical techniques such as x-ray photoelectron spectroscopy and ToF-SIMS are useful for investigating chemical changes between membranes. Herein, we present ToF-SIMS data obtained in the negative ion mode for four different PEEK membranes designed for use in CO2 capture systems. Positive ion mode spectra are reported in Paper I. [ABSTRACT FROM AUTHOR]

Mixed matrix membranes (MMMs) could combine the advantages of both polymeric membranes and porous fillers, making them an effective alternative to conventional polymer membranes. However, interfacial incompatibility issues, such as the presence of interfacial voids, hardening of polymer chains, and blockage of micropores by polymers between common MMMs fillers and the polymer matrix, currently limit the gas separation performance of MMMs. Ternary phase MMMs (consisting of a filler, an additive, and a matrix) made by adding a third compound, usually functionalized additives, can overcome the structural problems of binary phase MMMs and positively impact membrane separation performance. This review introduces the structure and fabrication processes for ternary MMMs, categorizes various nanofillers and the third component, and summarizes and analyzes in detail the CO2 separation performance of newly developed ternary MMMs based on both rubbery and glassy polymers. Based on this separation data, the challenges of ternary MMMs are also discussed. Finally, future directions for ternary MMMs are proposed.

CO2 separation plays a crucial role in tackling the climate change induced by the greenhouse effects and improving the energy quality of natural gas and biogas. The efficient CO2 separation technology is highly required. Membrane separation technology is particularly attractive in CO2 separation processes owing to its advantages. However, the trade-off relationship limited the gas separation efficiency of polymeric membranes in gas separation processes. Therefore, it is necessary to prepare the high-performance membranes such as mixed matrix membranes (MMMs) for CO2 separation. This review mainly focuses on the preparation methods, the material properties and the CO2 separation efficiency of the MMMs containing various fillers such as modified ZIFs, MOFs, and GO, and the emerging MOF-based composites, 2D MOFs and 2D MXene. The modified fillers demonstrated higher compatibility with polymer matrix, resulting in enhanced mechanical stability and CO2 separation efficiency of MMMs. 2D materials could significantly enhance the CO2 separation efficiency of MMMs, owing to their layered structure and the effective regulation of gas transport ways. Finally, the future direction and conclusions of fillers and MMMs in gas separation processes are provided.

As atmospheric CO2 levels continue to rise, contributing to the climate crisis, there is an increasing urgency to separate this gas from others and to expedite related research. Metal-Organic Frameworks (MOFs), known for their porosity and tunability, have already made significant impacts in this field, particularly to be used as part of a membrane material. This study introduces a novel method to enhance the CO2 separation capabilities of MOFs-based mixed matrix membranes (MMMs). Instead of taking the traditional approach by functionalizing the MOF's ligands or varying the metal or metal-oxo MOF nodes, we harness the properties of metal atoms by integrating them as central elements within porphyrinic MOF linkers through a simple post-metalation method. As a result, by incorporating the post-metalated MOF-525 as fillers into the 6FDA-DAM (6FDA: 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride; DAM: 2,4,6-trimethyl-1,3-diaminobenzene) polymer to fabricate MMMs, we effectively demonstrate improved CO2/N2 and CO2/CH4 gas separation capabilities of around 20 % without the necessity to use a very high MOF loading (only 2 wt%). Further analysis on the gas transport reveals that such a performance improvement mainly comes from the enhanced CO2 solubility, which might be attributed to the presence of the metal atoms in the post-metalated MOF 525. Lastly, in order to get a more comprehensive understanding, we also carry out a computational study as a tool to validate and predict the experimental results of our MMMs. This study then opens up the possibility to further investigate the efficacy of introducing various metal atoms in other porphyrinic MOFs when they are used as fillers to significantly boost the CO2 separation performance of MMMs.

Nitrogen-doped porous carbon (NPC) has a rich microporous structure and nitrogen-rich units, and its nitrogen-containing group can interact strongly with the PEO chain segment of Pebax, synergistically improving its CO2 adsorption ability and interface compatibility. This work prepared three types of triazine-based NPCs with mesoporous and high N-content and added NPCs to Pebax-2533 to prepare NPC/Pebax-2533 MMMs. The effects of N-type, N-content, and pore structure of NPCs on the gas separation performance of MMMs were studied. Constructing a continuous meso-microporous structure within the membrane and adding alkaline N-containing groups were beneficial for promoting rapid CO2 transport. Among the three NPCs, NPC-1/Pebax MMMs prepared using NPC-1 with the highest N-content (10.91%) and suitable pore structure exhibited the best gas separation performance. To investigate the gas transport mechanism of NPC in MMMs, NPC-1 was added to Pebax-2533 and Pebax-1657. The permeability of 3NPC-1/Pebax-2533 MMMs and 0.5NPC-1/Pebax-1657 MMMs reached 423 Barrer and 178 Barrer, with a CO2/N2 selectivity of 61 and 75.8, respectively, both higher than the Pebax-2533 and Pebax-1657. Adding NPC-1 to Pebax-2533 and Pebax-1657 increased the solubility and diffusivity coefficient of MMMs by 40 ~ 80%, and the gas separation performance did not rapidly decrease after long-term stability of 120 h (15%CO2/N2). Compared with NPC-1/Pebax-1657 MMMs, NPC-1/Pebax-2533 MMMs had higher CO2 permeability, mechanical properties, solubility, and diffusivity coefficient. The above results indicated that NPC was more suitable for Pebax-2533. [ABSTRACT FROM AUTHOR]

Mixed matrix membranes (MMMs) could combine the advantages of both polymeric membranes and porous fillers, making them an effective alternative to conventional polymer membranes. However, interfacial incompatibility issues, such as the presence of interfacial voids, hardening of polymer chains, and blockage of micropores by polymers between common MMMs fillers and the polymer matrix, currently limit the gas separation performance of MMMs. Ternary phase MMMs (consisting of a filler, an additive, and a matrix) made by adding a third compound, usually functionalized additives, can overcome the structural problems of binary phase MMMs and positively impact membrane separation performance. This review introduces the structure and fabrication processes for ternary MMMs, categorizes various nanofillers and the third component, and summarizes and analyzes in detail the CO2 separation performance of newly developed ternary MMMs based on both rubbery and glassy polymers. Based on this separation data, the challenges of ternary MMMs are also discussed. Finally, future directions for ternary MMMs are proposed. [ABSTRACT FROM AUTHOR]

The development of carbon dioxide (CO2) separation technology is crucial for mitigating global climate change and promoting sustainable development. In this study, we successfully synthesized an array of cross‐linked poly(vinyl alcohol) (PVA) membranes, xALD‐PEG‐ALD‐c‐PVA, with enhanced CO2/N2 separation performance by employing dialdehyde polyethylene glycol (ALD‐PEG‐ALD) as a cross‐linker. The formation of the cross‐linked network structure not only inhibits the crystallization of PVA but also disrupts hydrogen bonding and thus increases fractional free volume of PVA chains. Under the synergistic effect of these multiple factors, the cross‐linked PVA membranes exhibit a significantly improved CO2 permeability. Moreover, they maintain high CO2/N2 selectivity, attributing to the CO2‐philic characteristic of ethylene oxide groups in the cross‐linked structure. At the ALD‐PEG‐ALD content of 1.6 mmol g−1, the xALD‐PEG‐ALD‐c‐PVA membrane demonstrates a CO2 permeability of 41.4 barrer and a CO2/N2 selectivity of 57.4 at 2 bar and 25°C. Furthermore, compared with the pristine PVA membrane, xALD‐PEG‐ALD‐c‐PVA membranes manifest superior mechanical properties and outstanding separation performance for a CO2/N2 (15/85, vol%) gas mixture. The excellent combination of permeability and selectivity makes xALD‐PEG‐ALD‐c‐PVA membranes highly promising for various CO2 separation applications. [ABSTRACT FROM AUTHOR]

Over the last decades, porous organic materials (POMs) have been extensively employed in various industrial approaches including gas separation, catalysis and energy production due to possessing indisputable advantages like great surface area, high permeability, controllable pore size, appropriate functionalization and excellent processability compared to traditional substances like zeolites, Alumina and polymers. This review presents the recent breakthroughs in the multifunctional POMs for potential use in the membrane-based CO2 separation. Some examples of highly-selective membranes using multifunctional POMs are described. Moreover, various classifications of POMs following with their advantages and disadvantages in CO2 separation process es are explained. Apart from reviewing the state-of-the-art POMs in CO2 separation, the challenges/limitations of POMs with tailored structures for reasonable application are discussed. [ABSTRACT FROM AUTHOR]

New polysilsesquioxane (PSQ)-based CO2 separation membranes with succinic anhydride and monoalkylurea units as thermally degradable CO2-philic units were prepared by the copolymerization of a 1:1 mixture of [3-(triethoxysilyl)propyl]succinic anhydride (TESPS) or [3-(triethoxysilyl)propyl]urea (TESPU) and bis(triethoxysilyl)ethane (BTESE). The succinic anhydride and monoalkylurea units underwent thermal degradation to form ester and dialkylurea units, respectively, with the liberation of small molecules (e.g., CO2 and NH3) under N2 atmosphere. The effects of thermal degradation on the performance of the obtained membranes were investigated. The TESPS-BTESE- and TESPU-BTESE-based membranes calcined at 250 °C and 200 °C exhibited good CO2/N2 permselectivities of 20.2 and 14.4, respectively, with CO2 permeances of 7.7 × 10−8 and 7.9 × 10−8 mol m−2·s−1·Pa−1, respectively. When the membranes were further calcined at elevated temperatures of 350 °C and 300 °C, respectively, to promote the thermal degradation of the organic units, the CO2 permeances increased to 1.3 × 10−7 and 1.2 × 10−6 mol m−2·s−1·Pa−1 (3.9 × 102 and 3.6 × 103 GPU), although the CO2/N2 permselectivities decreased to 19.5 and 8.4, respectively. These data indicate that the controlled thermal degradation of the organic units provides a new methodology for possible tuning of the CO2 separation performance of PSQ membranes. [ABSTRACT FROM AUTHOR]

Recently, carbon neutrality has been promoted as a potentially practical solution to global CO2 emissions and increasing energy‐consumption challenges. Many attempts have been made to remove CO2 from the environment to address climate change and rising sea levels owing to anthropogenic CO2 emissions. Herein, membrane technology is proposed as a suitable solution for carbon neutrality. This review aims to comprehensively evaluate the currently available scientific research on membranes for carbon capture, focusing on innovative microporous material membranes used for CO2 separation and considering their material, chemical, and physical characteristics and permeability factors. Membranes from such materials comprise metal‐organic frameworks, zeolites, silica, porous organic frameworks, and microporous polymers. The critical obstacles related to membrane design, growth, and CO2 capture and usage processes are summarized to establish novel membranes and strategies and accelerate their scaleup. [ABSTRACT FROM AUTHOR]

This work aims to explain the role of the structural building units of selected Zr-based Metal-Organic Frameworks (MOFs) in the separation of binary CO2/CH4 mixture. The results of the GCMC simulations imply that there is a significant difference in the adsorption capacities with respect to different guest types for different MOF topolo- gies. In most cases, the preferable interactions are with the CO2 molecule, however, depending on the MOF topology, the preference toward CH4 increases. This study is focused on the analysis of the geometrical factors of the host framework on the separation properties, which is a step forward toward the rational design of the sor- bent material. [ABSTRACT FROM AUTHOR]

This study uses Aspen Plus simulations to explore the performance of a new flowsheet for ammonia production using Three Reactor Chemical Looping (TRCL) technology. In TRCL, the solid Oxygen Carrier continuously circulates between a Fuel Reactor, a Steam Reactor and an Air Reactor. The Oxygen Carrier is reduced in the Fuel Reactor and oxidised in the Steam and Air Reactors. Hydrogen generated in the Steam Reactor and nitrogen produced from the Air Reactor form a synthesis gas that is converted to ammonia. This study compares the TRCL process with the conventional ammonia process and a pseudo-continuous Chemical Looping Reforming (CLR) process that uses packed beds. Energy and environmental indicators are evaluated for the three processes. It was found that the energy consumed in the TRCL process is higher than the other two processes because of higher steam consumption in the Steam Reactor for generating hydrogen. However, if conversion in the Steam Reactor of greater than 67.5% can be achieved, the energy performance indicators are comparable with the conventional and CLR processes. At 67.5% conversion, the specific energy consumption becomes 21.5 GJ/t NH3. It is also noted that the Specific Energy Consumption for Carbon dioxide Avoidance (SPECCA) is much better than the conventional ammonia process at a steam conversion higher than 67.5%. Although further development is needed, this study shows that TRCL holds promise for lower energy consumption and better environmental performance than other commercial ammonia production technologies. • Aspen Plus simulations revealed viability of NH 3 generation using TRCL process. • TRCL requires lower energy (28.49 GJ/t NH3) than commercial NH 3 process. • Steam demand is higher for TRCL than for commercial and CLR-PB cases. [ABSTRACT FROM AUTHOR]

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Membrane‐based gas separation technologies are one solution towards mitigating global emissions of CO2. New membrane materials with improved separation performance are still highly sought after. Composite membranes based on organic ionic plastic crystals (OIPCs) have shown preferential interaction for CO2 over N2, leading in some cases to competitive CO2/N2 selectivities. However, these ionic materials have been scarcely studied in the field of gas separation. Here, OIPCs based on the bis(trifluoromethylsulfonyl)imide ([TFSI]−) anion were investigated for use as gas separation membranes for the first time. The effect of the polymer type was also investigated, through the comparison of poly(vinylidene fluoride) (PVDF) and poly(vinylidene fluoride)‐hexafluoropropylene (PVDF‐HFP) OIPC membranes. A strong temperature dependence of the gas separation performance was found, particularly in the N‐methyl‐N‐ethylpyrrolidinium‐based composites where the material undergoes a solid‐solid phase transition within the testing temperature range. The polymer type was noted to induce a strong effect on the structure of the composites, as well as affecting the gas and ionic transport. Thus, this research provides insights on the influence of the [TFSI]− anion on the structure and separation properties of OIPC‐based composites, and new information towards the development of novel OIPC‐based membranes with enhanced gas separation performance. [ABSTRACT FROM AUTHOR]

The ability to efficiently separate CO2 from other light gases using membrane technology has received a great deal of attention due to its importance in applications such as improving the efficiency of natural gas and reducing greenhouse gas emissions. A wide range of materials has been employed for the fabrication of membranes. This paper highlights the work carried out to develop novel advanced membranes with improved separation performance. We integrated a polymerizable and amino acid ionic liquid (AAIL) with zeolite to fabricate mixed matrix membranes (MMMs). The MMMs were prepared with (vinylbenzyl)trimethylammonium chloride [VBTMA][Cl] and (vinylbenzyl)trimethylammonium glycine [VBTMA][Gly] as the polymeric support with 5 wt% zeolite particles, and varying concentrations of 1-butyl-3-methylimidazolium glycine, [BMIM][Gly] (5–20 wt%) blended together. The membranes were fabricated through photopolymerization. The extent of polymerization was confirmed using FTIR. FESEM confirmed the membranes formed are dense in structure. The thermal properties of the membranes were measured using TGA and DSC. CO2 and CH4 permeation was studied at room temperature and with a feed side pressure of 2 bar. [VBTMA][Gly]-based membranes recorded higher CO2 permeability and CO2/CH4 selectivity compared to [VBTMA][Cl]-based membranes due to the facilitated transport of CO2. The best performing membrane Gly-Gly-20 recorded permeance of 4.17 GPU and ideal selectivity of 5.49. [ABSTRACT FROM AUTHOR]

Plastic waste has captured considerable attention in gasification studies as it not only generates precious syngas rich in hydrogen but also aids in mitigating the environmental concerns linked to these substances. The proposed system employs the process of plastic waste gasification (PWG) to generate synthetic gas, which undergoes processing within multiple subsystems. Crucially, this ingenious system uses the liberated heat from the biogas-fueled chemical looping combustion (CLC) to facilitate the efficient decomposition and gasification of the plastic waste, which the CLC holds great potential as a technology for capturing CO 2 without any energy penalty. In the Aspen Plus software, a comprehensive simulation is conducted for the proposed system, with a focus on detailed modeling of CLC. Through this analysis, it is determined that the optimal operating condition for CLC occurs at a molar ratio of 2.6 between the oxygen carrier and biogas. Also, the results show that the overall thermal and exergy efficiencies of the CLC-PWG system are found to be 77.08% and 67.62%, respectively. Regarding exergy destruction distribution, it is noteworthy that the air reactor significantly contributes to the highest proportion, accounting for 35.3% of the total exergy destruction. Subsequently, the fuel reactor and gasifier also play significant roles, accounting for 13.6% and 13.1%, respectively. In addition, the proposed system has a power, heat and hydrogen production rate of 97 kW, 388 kW and 105.6 kg/hr, respectively. Moreover, the thermodynamic efficiencies increase through the elevation of the gasification reactor temperature and the mass ratio of steam to plastic waste. [Display omitted] [ABSTRACT FROM AUTHOR]

Highly permeable and selective membranes with long-term stability are needed to reduce operating and capital costs of industrial gas-separation units. In this study, we fabricate new membranes made of melamine (M)- and imidazolium-based ionic liquid (IL)-modified graphene oxide (GO) deposited on a porous support and buried with a polydimethylsiloxane (PDMS) layer. The CO2/N2 and CO2/CH4 ideal selectivities of the composite membranes are respectively 65 % and 70 % higher than those of the membranes containing only the IL. This significant improvement in ideal selectivity is attributed to synergic effects of nanochannels created by GO, fixed facilitated transport provided by the IL and numerous amine groups in the melamine structure, and the increased polarity of the membrane caused by the presence of the IL. The composite membrane has a pure CO2 permeance of 47 GPU with a high CO2/N2 ideal selectivity of 109 and a satisfactory CO2/CH4 ideal selectivity of 39. The composite membrane maintains stable performance over a 60-hour operation, highlighting its long-term reliability. The outstanding performance, coupled with the ease of fabrication, underscores the potential of these composite membranes for practical and efficient CO2 removal from both natural and flue gas streams in real-world applications.

The separation of CO2 has been recognized as a potential approach to address the impacts of climate change resulting from the emission of flue gases into the environment. Efficient separation technologies are required to effectively remove CO2 from flue gases. To resolve this problem, membrane-based gas separation is considered an economically viable and energy-efficient technology over conventional techniques. Functional polymeric membranes have gained a lot of interest for their attractive gas separation performance. Thus, this work aims to critically review the recent developments of functional polymeric membranes designed for CO2 separation from flue gases. Starting with a background on flue gases and polymeric membranes, a brief discussion on Robeson's upper bound for CO2/N2 separation is provided. After that, a detailed analysis of the current advancements in different membrane modification approaches, such as mixed matrix, grafting, layer-by-layer assembly, and interfacial polymerization, for improved performance of polymeric membranes is provided. Furthermore, the effect of CO2 on polymeric membranes (plasticization and aging), the current global market and key market players in the membranes-based gas separation field are discussed thoroughly. Finally, a concise remark on the future directions of polymeric membranes for CO2 separation from flue gases is presented.

This study investigated the effect of different synthesis parameters including pre- and post-hydrothermal treatment on the formation of a high-quality SSZ-13 membrane layer. The membranes were identified initially by the gas tightness test, then were characterized by single gas permeation measurements applying H2, He, CO2, N2, CH4, and SF6 at room temperature. The results showed how each parameter affects the performance of the membrane, including structural defects in the formed selective layer, CO2 permeance, and the ideal CO2/CH4 permselectivity. This work focused on optimizing these parameters. An ideal CO2/CH4 permselectivity of up to 122 with CO2 permeance of ~3.72 × 10−6 [mol/(m2sPa)] and CO2/CH4 selectivity of 111 with CO2 permeance of 8.5 × 10−7 [mol/(m2sPa)] in an equimolar mixture at room temperature and pressure drop of 0.15 MPa was achieved. This is one of the highest performances compared to other publications for SSZ-13 or all-Si membranes.

Membrane‐based CO2 separation is vital for various applications such as biogas upgradation. Polymer membranes are employed for CO2 separation in the industry. Polymer membranes have a trade‐off between selectivity and permeability. Blending polymers is an emerging approach for altering the gas transport in the membranes. This work investigates the fabrication and characterization of blended biodegradable cellulose acetate (CA) with polyimide (PI). Thermal stability was characterized using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), and functional groups were analyzed using Fourier transform infrared spectroscopy (FTIR). The morphology of membranes is analyzed using field‐emission scanning electron microscope (FESEM). The blend membranes were tested for separation of CO2 from model biogas (CO2/CH4) at room temperature and a low feed pressure (∼1.5 bar). The CA:PI blend membrane composed of 93% CA and 7% PI showed CO2 permeability of 19.71 Barrer, approximately 206% greater than pure CA, and CO2/CH4 selectivity was 9.42. Experimental results are compared with literature on CA‐based membranes. Highlights: Blend membrane of cellulose acetate (CA) and polyimide (PI)CO2/CH4 gas permeation testing of membranes using a model biogas mixtureBlend membranes exhibit 206% higher CO2 permeability than pure CA membranesBlend membranes demonstrated enhanced CO2/CH4 selectivity of 9.42. [ABSTRACT FROM AUTHOR]

Graphene oxide nanoparticles (GO) were firstly functionalized using p‐phenylenediamine and then utilized as nanofillers to prepare poly(ether‐block‐amide) (Pebax®‐1657)/poly(vinyl alcohol) (PVA‐60000)‐based mixed‐matrix membranes. The modified GO as well as the fabricated mixed matrix membranes underwent some characterization analyses, including FTIR, TGA, XRD, FESEM, and EDX. The influence of amine‐modified nanoparticles content (2, 4, and 6 wt%), and feed pressure on CO2, CH4, and N2 permeabilitis and ideal CO2/CH4 and CO2/N2 selectivities values of the MMMs were investigated. The permeation experiments demonstrated that Pebax/PVA (10 and 15 wt%) blend membranes caused an increase in CO2 permeability owing to the high affinity of polar CO2 molecules to polar PVA segments. Moreover, the incorporation of 6 wt% amine‐functionalized GO into the Pebax/PVA (10 wt%) and Pebax/PVA (15 wt%) blend polymer raised the CO2 permeability and CO2/CH4 and CO2/N2 selectivity by nearly 43%, 28%, and 37%, respectively, due to the higher CO2 adsorption capacity of the amine‐functionalized GO. [ABSTRACT FROM AUTHOR]

The inorganic-carbonate dual-phase membrane represents a class of dense membranes that are fabricated using diverse support materials, ranging from metals to ceramics. This dual-phase membrane consists of a porous metal or ceramic support with an introduced carbonate phase within the support pores. Compared with polymer and zeolite membranes, inorganic-carbonate dual-phase membranes exhibit exceptional CO2 selectivity at elevated temperatures (>500 °C), making them an ideal choice for high-temperature CO2 separation in power plant systems. The present paper provides a comprehensive overview of the separation principle, significant models, and preparation techniques employed in carbonate dual-phase membranes for CO2 separation. The present study aims to discuss key factors that limit the CO2 permeation performance and stability of membranes, while also exploring the potential applications of dual-phase membranes in various fields. The identification of key challenges in the future development of the carbonate dual-phase membrane has been highlighted in this work. The future trajectory of research and development should be directed toward overcoming these challenges, encompassing the synthesis technology of membranes, balance optimization of membrane structure and performance, modification of physical and chemical properties of molten carbonate, and advancement in high-temperature sealing techniques, as well as exploration of diverse membrane reactors based on carbonate dual-phase membranes for prospective applications. [ABSTRACT FROM AUTHOR]

In order to improve the energy efficiency of the Sabatier reactor-based power-to-gas process, molten carbonate fuel cells and solid oxide electrolyzers were installed instead of a conventional amine CO 2 capture system and a classical alkaline electrolyzer. The plant is a multi-module prototype with a nominal capacity of 50 kW consisting of two SOE-MCFC units. The system was commissioned in 2022. The article describes the theoretical basis. The initial assumptions that were formulated at the stage of preparing for the research investment, as well as the deviations from them that became the result of detailed design were presented. The developed startup and shutdown procedures, as well as the first results of pioneering research were shown. The trial operation of the system was intended to provide information on integrated SOE-MCFC module and its performance and efficiency. The basic barriers for market implementation and recommendations for future research were discussed. The optimal operating point for hydrogen production needed 35.8 kWh/kgH 2. Thus, electrical energy conversion to chemical energy efficiency is 93.9%. Flow preheating and electrical auxiliary heater power are not included. An MCFC at its ideal functioning point (around 4 kW el) outputs 5.4 kg/h of CO 2 separated. • Operational experience of upgraded novel P2G installation is reported. • A start-up procedure of MCFC-SOE tandem in proposed and experimentally verified. • Energy required for synthesis of a kilogram of hydrogen was 35.8 kWh/kgH 2. [ABSTRACT FROM AUTHOR]

An innovative technique to efficiently remove CO2 involves introducing a third component with a positive affinity with CO2 into a binary mixed‐matrix membrane (MMM) and eliminating interfacial defects in its structure. In this research, novel ternary MMMs (TMMMs) were synthesized by embedding 1–Hexyl–3–methylimidazolium bis(trifluoromethylsulfonyl)imide ([HMIM][NTf2]) ionic liquid (IL) and aluminum oxide (γ–Al2O3) nanoparticles into poly (ether‐block‐amide) (Pebax‐1657) matrix for enhancing CO2 removal from light gases. FESEM, DSC, ATR‐FTIR, and XRD analyses were used to evaluate the fabricated MMMs structurally. The permeation tests of gases (CH4, N2, and CO2) through prepared membranes were conducted at 25°C and 4, 6, 8, and 10 bar pressures. In accordance with the permeation outcomes, the ternary MMMs exhibited enhanced CO2 separation performances compared to the unloaded polymeric membrane. Also, the optimized MMM comprising 10 wt.% of the IL and 6 wt.% of the nanoparticles obtained a CO2 permeability of 173.90 Barrer, as well as CO2/N2 and CO2/CH4 selectivities of 77.98 and 24.29 at 10 bar and 25°C, which are higher by about 51%, 23%, and 22%, respectively than those of the pristine polymeric membrane. Based on these results, the prepared membrane appears to be a promising choice for separating CO2 from light gases. [ABSTRACT FROM AUTHOR]

Membrane separation is one of the techniques used for biogas upgradation. Mixed matrix membranes (MMMs) are currently being explored to overcome the trade‐off of selectivity‐permeability inherent in polymer membranes used for gas separation. A significant challenge associated with MMMs is the poor polymer‐metal–organic framework (MOF) filler interfacial compatibility, reducing the selectivity or permeability of gas. To address this issue, the present study focuses on the effect of the amine functionalization of ZIF‐8 to enhance the CO2 gas permeation without reducing the CO2/CH4 selectivity. MMMs were fabricated using unmodified ZIF‐8 and amine‐modified ZIF‐8 nanofillers dispersed in polysulfone at 5, 10, and 15 wt% loadings. MMMs were characterized by FTIR, DSC, TGA, and FESEM. X‐ray diffraction and FTIR analysis was conducted to verify the amine modification of ZIF‐8. Further, the performance of MMMs was tested with pure gasses (CO2 and CH4) and a model mixture of CO2 and CH4. In the mixed gas permeation test, the 10 wt% ZIF‐8 MMM exhibited the highest CO2 permeability of 25.4 Barrers, while 15 wt% NH2‐ZIF‐8 MMM exhibited the highest selectivity of 13.5. Notably, the ZIF‐8 MMMs demonstrated a 148% increase in CO2/CH4 selectivity, whereas the NH2‐ZIF‐8 MMMs exhibited a 155% increase compared to the pure polysulfone membrane. [ABSTRACT FROM AUTHOR]

This study emphasizes the importance of a sustainable energy supply with regard to climate change. A way is shown how a de‐centralized heat supply in urban areas with renewable energies can be combined with algae production. The decentrally generated CO2 emissions are made usable for biomass production by means of membrane separation technology. The operating behavior of the CO2‐selective membrane materials was observed over an operating period of almost 10 years. This provides solid evidence of the operability of the polymer membrane and membrane module technology. It enables further optimization of the separation process for future applications, also in a wider range of applications. [ABSTRACT FROM AUTHOR]

Over the last decades, porous organic materials (POMs) have been extensively employed in various industrial approaches including gas separation, catalysis and energy production due to possessing indisputable advantages like great surface area, high permeability, controllable pore size, appropriate functionalization and excellent processability compared to traditional substances like zeolites, Alumina and polymers. This review presents the recent breakthroughs in the multifunctional POMs for potential use in the membrane-based CO2 separation. Some examples of highly-selective membranes using multifunctional POMs are described. Moreover, various classifications of POMs following with their advantages and disadvantages in CO2 separation processes are explained. Apart from reviewing the state-of-the-art POMs in CO2 separation, the challenges/limitations of POMs with tailored structures for reasonable application are discussed.

Hydrotalcite exhibits the capability to adsorb CO2 at elevated temperatures. High surface area and favorable coating properties are essential to harness its potential for practical applications. Stable alcohol-based dispersions are needed for thin film applications of mixed membranes containing hydrotalcite. Currently, producing such dispersions without the need for delamination and dispersing agents is a challenging task. This work introduces, for the first time, a manufacturing approach to overcoming the drawbacks mentioned above. It includes a synthesis of hydrotalcite nanoparticles, followed by agent-free delamination of their layers and final dispersion into alcohol without dispersing agents. Further, the hydrotalcite-derived sorption agent is dispersed in a matrix based on organo-silica gels derived from 1,2-bis(triethoxysilyl)ethane (BTESE). The analytical results indicate that the interconnection between hydrotalcite and BTESE-derived gel occurs via forming a strong hydrogen bonding system between the interlayer species (OH groups, CO32−) of hydrotalcite and oxygen and silanol active gel centers. These findings lay the foundation for applications involving incorporating hydrotalcite-like compounds into silica matrices, ultimately enabling the development of materials with exceptional mass transfer properties. In part 2 of this study, the gas separation performance of the organo-silica and the hydrotalcite-like materials and their combined form will be investigated.

Design considerations concerning the maximum purity of a membrane separator, and the resultant maximum effective selectivity of the membranes were explored by modeling a binary gas membrane separator (pressure-driven permeance) using a dimensionless form. Although the maximum purity has an analytical solution at the limit of zero recovery or stage cut, this solution over-predicts the obtained purity as the recovery is increased. Furthermore, at combinations of high recovery, low feed mole fraction, and low pressure ratio, the maximum purity becomes independent of selectivity above some critical selectivity. As a consequence of this purity limitation, a maximum selectivity is defined at which further increases in selectivity will result in less than a 1% change in the final purity. An equation is obtained that specifies the region in which a limiting purity is less than unity (indicating the existence of a limiting selectivity); operating at less than the limiting pressure ratio results in a purity limitation less than unity. This regime becomes larger and more significant as the inlet mole fraction decreases (e.g., inlet feed mole fraction of 10% and pressure ratio of 100 results in a maximum useful membrane selectivity of only 130 at 95% recovery). These results suggest that membrane research should focus on increasing permeance rather than selectivity for low-concentration separations. The results found herein can be used to set benchmarks for membrane development in various gas separation applications.

Abstract The objective of this work was to produce Pebax®/polydopamine (PDA) blends and apply these blends to produce membranes for gas separation. Flat sheet membranes were tested for gas permeation, differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), wide angle x-ray diffraction (WAXD), scanning electron microscopy (SEM) and fourier transformed infrared spectroscopy (FTIR). The results show an optimal concentration of dopamine hydrochloride that produces the best results (��=100, P=114 Barrer). DSC and WAXD results indicate that polydopamine influences the crystallization of Pebax®, reducing the melting and crystallization temperatures of PA blocks and increasing the melting temperature of PEO blocks. The incorporation of PDA decreases gas permeability and increases gas selectivity. The decrease in permeability indicates that the presence of polydopamine reduces the diffusion coefficient of Pebax® by reducing the segmental mobility of PEO blocks and possibly the fraction free volume. Compared to the trade-off, Pebax®/PDA membranes surpasses the upperbound for CO2/N2 separation.

Industrial application of novel, green and effective liquid absorbents for improving the separation yield of CO2 greenhouse pollutant is an important milestone to reduce its emission to the atmosphere. In this research, the separation performance of three novel and green ionic liquids (ILs) including [bmim][PF6], [bmim][BF4] and [emim][etSO4] are compared with pure water to evaluate the feasibility of their employment to enhance the removal potency of CO2 through the membrane contactor. With the aim of reaching this goal, a finite element-based model and a numerical simulation are developed to solve the momentum/mass transfer equations and predict the results. Based on the modeling/simulation outcomes, the addition of the abovementioned ILs could substantially increase the separation of CO2 molecules compared to pure water. Based on the results, [bmim][BF4] is introduced as the most efficient IL with the separation efficiency of 100 % (100 % [bmim][BF4]> 99 % [bmim][PF6]> 97.5 % [emim][etSO4]> 55 % pure water). Furthermore, the effects of different operational/functional parameters (i.e., gas flow rate, porosity, fibers’ number and packing density) on the CO2 separation efficacy is comprehensively discussed.

Separation membranes, which have the possibility to develop energy-saving and compact processes, are expected to be applied in the field of CO2 separation and capture and are attracting considerable interest from both industries and academia. The purpose of this review is to provide an overview of recent advances in both organic and inorganic materials for high-performance CO2 separation membranes from the viewpoint of molecular design to an engineering perspective. The overview includes gas permeation theory for CO2 capture and separation, controlled intrinsic micropores and their size-sieving property, CO2 diffusivity in the membrane matrix, selective CO2 solubility and selective permeability, functionalization using chemical reactions, etc. CO2 separation mechanisms and the effects of properties of membrane materials on both the CO2 permeability and permselectivity over other light gases are discussed, and the recent developments regarding inorganic and glassy polymer membranes with intrinsic microporous structures, rubbery polymer membranes, ionic liquid-based gel membranes, and facilitated-transport membranes are reviewed. Taking into consideration the industrial applications, the characteristics of each membrane with respect to process design, such as membrane thickness, and physical aging, and dependence of CO2 permeability on gas properties, are also discussed. Finally, future research challenges and perspectives for the commercialization of CO2 capture and separation process using high-performance materials are proposed.

The use of mixed matrix membranes (MMMs) comprising metal–organic frameworks (MOFs) for the separation of CO2 from flue gas has gained recognition as an effective strategy for enhancing gas separation efficiency. When incorporating porous materials like MOFs into a polymeric matrix to create MMMs, the combined characteristics of each constituent typically manifest. Nevertheless, the inadequate dispersion of an inorganic MOF filler within an organic polymer matrix can compromise the compatibility between the filler and matrix. In this context, the aspiration is to develop an MMM that not only exhibits optimal interfacial compatibility between the polymer and filler but also delivers superior gas separation performance, specifically in the efficient extraction of CO2 from flue gas. In this study, we introduce a modification technique involving the grafting of poly(ethylene glycol) diglycidyl ether (PEGDE) onto a UiO-66-NH2 MOF filler (referred to as PEG-MOF), aimed at enhancing its compatibility with the 6FDA-durene matrix. Moreover, the inherent CO2-philic nature of PEGDE is anticipated to enhance the selectivity of CO2 over N2 and CH4. The resultant MMM, incorporating 10 wt% of PEG-MOF loading, exhibits a CO2 permeability of 1671.00 Barrer and a CO2/CH4 selectivity of 22.40. Notably, these values surpass the upper bound reported by Robeson in 2008. [ABSTRACT FROM AUTHOR]

Molybdenum sulfide (MoS 2) materials adapted into membranes have demonstrated potential for different areas dealing with molecular separations. For instance, MoS 2 -based membranes have been proposed for distinct environmental applications, such as water treatment, seawater desalination, gas separation, and solvent separation. Emergently, such membranes have been ultimately investigated for energy-relevant gas separation mixtures, such as CO 2 separation, H 2 purification, and bioethanol upgrading, among others. Therefore, this review elucidates the latest research (over the last three years) on MoS 2 -based membranes facing previous approaches. Firstly, a brief introduction to the physiochemical properties of MoS 2 -based materials. Secondly, a particular emphasis has been devoted to fabrication procedures and their effects on molecular separation in membrane processes, highlighting the most relevant outcomes and the transport mechanism reported by the research community in water treatment and purification, gas separation, and pervaporation. Finally, an analysis is conducted on the separation and stability mechanisms associated with membranes consisting of layer-stacked MoS 2. This research endeavor progressions in MoS 2 -based membranes, consequently fostering the advancement of further membranes derived from two-dimensional materials. These membranes exhibit potential for improving efficiency and mitigating the energy consumption linked to water treatment and purification processes. [Display omitted] • Composite membranes containing MoS2 exhibit potential for different environmental energy-relevant separations. • The hexagonal lattice structure of MoS2 allows the fabrication of nanoscale thickness with tunable interlayer spacing. • MoS2 membranes proved exceptional molecular sieving effect in seawater desalination. • Emerging applications in CO2 and H2 separation have been initiated over the last two years. [ABSTRACT FROM AUTHOR]