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Imidazole ionic liquids (ILs) have good affinity and good solubility for carbon dioxide (CO2). Such ionic liquids, combined with polyimide membrane materials, can solve the problem that, today, CO2 is difficult to separate and recover. In this study, the ionic liquid (IL) of 1-ethyl-3-methylimidazolium tetrafluoroborate (IL1), 1-pentyl-3-methylimidazolium tetrafluoroborate (IL2), 1-octyl-3-methylimidazolium tetrafluoroborate (IL3), and 1-dodecylimidazolium tetrafluoroborate (IL4) with different contents were added to a polyimide matrix, and a series of polyimide membranes blended with ionic liquid were prepared using a high-speed mixer. The mechanical properties and gas separation permeability of the membranes were investigated. Among them, the selectivity of the PI/IL3 membrane for CO2/CH4 was 180.55, which was 2.5 times higher than the PI membrane, and its CO2 permeability was 16.25 Barrer, which exceeded the Robeson curve in 2008; the separation performance of the membrane was the best in this work. [ABSTRACT FROM AUTHOR]

Carbon molecular sieve (CMS) membranes show attractive potential for energy-efficient separation of C 2 H 4 /C 2 H 6 due to their unique slit-like pore structure. In this work, a novel precursor polymer of phenolphthalein-based poly(arylene ether ketone) (PEK-C) was introduced to prepare high-performance CMS membranes for C 2 H 4 /C 2 H 6 separation. Molecular insight into the effect of the sp 3/ sp 2 hybridized carbon ratio on the packing morphology of carbon layers, pore size and configuration, and C 2 H 4 /C 2 H 6 diffusion and separation properties of CMS membranes was investigated via using in-depth characterization techniques combined with molecular simulations. Results show that the carbon layers with more sp 3 hybridized carbons lead to forming a loose and disordered carbon structure and pore structure with large pore volume and micropore size (steric voids), resulting in low C 2 H 4 /C 2 H 6 permselectivity of CMS membrane. With the reduction of the sp 3/ sp 2 hybridized carbon ratio, a compact and graphite-like carbon structure with the two-dimensional slit-like ultramicropore structure is formed, and the C 2 H 4 /C 2 H 6 permselectivity is obviously enhanced. The CMS membranes derived from the novel precursor of PEK-C exhibit high C 2 H 4 permeability with superior C 2 H 4 /C 2 H 6 selectivity, which have surpassed the trade-off bounds of both polymeric membrane and CMS membrane, and reveal a great potential in the industrial applications of C 2 H 4 /C 2 H 6 separation. [Display omitted] • A novel precursor was introduced to prepare high-performance CMS membranes. • The structure-property relationships between microstructure and gas separation performance were investigated. • The sp3/ sp 2 hybridized carbon ratio obviously affects the C 2 H 4 /C 2 H 6 diffusion selectivity. • The C 2 H 4 /C 2 H 6 separation performance of CMS membranes exceed the trade-off bounds of polymeric and CMS membranes. [ABSTRACT FROM AUTHOR]

• Pebax-based membranes containing different 2D materials for CO 2 capture. • The separation mechanism and properties of Pebax materials are discussed. • The transport mechanism of CO 2 in the membrane was explained. • The challenges and future directions of the Pebax gas separation field are presented. Since the onset of the industrial age, annual global CO 2 emissions have risen, significantly affecting the climate and natural ecosystems. Addressing this, the development of carbon capture, utilization, and storage (CCUS) technologies becomes crucial. Gas membrane separation, recognized for its efficiency, low energy consumption, and eco-friendly nature, is rapidly gaining prominence in global carbon capture efforts. Polyether-block-polyamide (Pebax), with its high CO 2 affinity and resilient mechanical properties (attributed to its elastic polyether and robust polyamide segments) is gaining traction in CO 2 separation research. Yet, the inherent trade-off effect poses challenges for its industrial application. This article delves into the current research landscape of gas separation membranes made of Pebax and assorted 2D nanomaterials for CO 2 separation. It outlines the separation mechanism of Pebax materials and elucidates the CO 2 separation membrane's transport mechanism. Further, the application of gas separation membranes formed by combining Pebax with various 2D nanomaterials for CO 2 capture is also described in detail. Relevant studies underscore that these gas separation membranes offer enhanced separation efficacy and stability, positioning them as potential leaders in CO 2 separation solutions. The paper concludes by highlighting challenges in Pebax-based research and suggesting future research avenues. [ABSTRACT FROM AUTHOR]

• Review the macromolecular structures of microporous polymers for O 2 /N 2 separation. • Explore the aging behavior of innovative microporous materials. • Review the impacts of thermal treatments to reset microporosity and O 2 /N 2 separation. • Investigate the application of polymers and process design in membrane systems. This review summarizes the performance of recently developed microporous polymers for practical industrial O 2 /N 2 separations. The macromolecular design of innovative polymers of intrinsic porosity and derivatives is evaluated from the perspective of pore structure regulation for their outstanding O 2 /N 2 separation performance. The structural groups that could fine-tune the free volume elements are examined to discern the promising moiety and architectures to improve size-based sieving. The long-term aging behaviors of the state-of-the-art macromolecules are also screened to explore the impacts of improved pore/free volume configuration. The strategies using thermal treatments to reset the structure of microporosity are inspected for their potential to improve the gas permeability or enhance size-specific molecular sieving, including the thermal rearrangement of polymeric membranes and pyrolyzed carbon molecular membranes using pre-crosslinked precursors and PIM-derived precursors. Membrane process design and optimization are summarized to evaluate the prospects of these novel membrane materials for large-scale industrial applications. [ABSTRACT FROM AUTHOR]

Chemical structure and morphology of polymers are directly related with the membrane separation performance. Poly(imide)s (PIs) are the most widely used polymers in the preparation of membranes for gas separation applications; thus, research on the structural design of polymers is of great interest to develop new membranes. In the present work, we reported the synthesis, characterization, and measurement of the gas transport properties of a new co-poly(imide)s (PI-D2a-D2b-6FDA) prepared from a mixture of isomeric diamines. The co-poly(imide) synthetic route involved several steps, starting by a bromination reaction, followed by a double nucleophilic aromatic substitution giving an isomeric mixture of precursors, which suffered a Suzuki-Miyaura C–C cross-coupling reaction followed by the reduction of nitro groups to give two new isomeric diamines. Finally, diamines simultaneously reacted with the dianhydride 6FDA to obtain PI-D2a-D2b-6FDA. The co-poly(imide) had a M n of 47.7 kDa and a M w of 74.0 kDa with a PDI of 1.6. The sample exhibited a 10% weight loss at 540 °C, T g of 280 °C, BET surface area of 110 m2 g−1, and wide-angle X-ray diffraction (WAXD) interchain d- spacing at 9.5 Å and 6.3 Å. Tensile strength, elongation at break and Young's modulus were 109.6 MPa, 6.66% and 2.18 GPa, respectively. co-Poly(imide) was soluble in various polar aprotic organic solvents such as DMSO, NMP, DMF, DMAc, THF, and chloroform, forming a self-standing dense film whose gas transport properties were measured. Pure gas permeability coefficients for H 2 , CO 2 , O 2 , N 2 , and CH 4 , were 47.28, 24.04, 4.35, 1.02, and 0.76 (Barrer), respectively, which follows a decreasing order by the increasing kinetic diameters of the respective gases. Ideal gas selectivities H 2 /N 2 , O 2 /N 2 , CO 2 /CH 4 , and CO 2 /N 2 were 46.4, 4.3, 31.6, and 23.6, respectively. These gas transport properties were compared with the commercial polymer Matrimid®, showing higher gas permeability coefficients than Matrimid®. Synthetic route to obtain a new self-standing co-polyimide. [Display omitted] • A new co-poly(imide)s was prepared from a mixture of isomeric diamines (position monomers). • The co-poly(imide) was soluble even in low boiling point solvents like THF and chloroform, forming a self-standing dense film. • Isomeric structures in the polymer lead to irregular growth, achieving higher diffusion coefficients than Matrimid®. [ABSTRACT FROM AUTHOR]

Compared with current conventional technologies, oxygen/nitrogen (O2/N2) separation using membrane offers numerous advantages, especially in terms of energy consumption, footprint, and capital cost. However, low product purity still becomes the major challenge for commercialization of membrane-based technologies. Therefore, numerous studies on membrane development have been conducted to improve both membrane properties and separation performance. Various materials have been developed to obtain membranes with high O2 permeability and high O2/N2 selectivity, including polymer, inorganic, and polymer-inorganic composite materials. The results showed that most of the polymer membranes are suitable for production of low to moderate purity O2 and for production of high-purity N2. Meanwhile, perovskite membrane can be used to produce a high-purity oxygen. Furthermore, the developments of O2/N2 separation using membrane broaden the applications of oxygen enrichment for oxy-combustion, gasification, desulfurization, and intensification of air oxidation reactions, while nitrogen enrichment is also important for manufacturing pressure-sensitive adhesive and storing and handling free-radical polymerization monomers. [ABSTRACT FROM AUTHOR]

Metal-organic framework (MOF) membranes have become promising candidates for gas separation due to their adjustable structure, high separation performance, and environmental friendliness. However, the emergence of grain boundary defects, and interface defects between the support layer and separation layer significantly decrease the gas separation performance of MOF membranes. Herein, a self-supported ZIF (zeolitic imidazolate framework) glass membrane is fabricated, eliminating grain boundary defects and cracks through the molten-liquid phase. The fluorine-based linkers with high electronegativity and polarizability are introduced to enhance a g ZIF-62(a and g denote amorphous and glass, respectively) interaction of CO 2 and CH 4. The CO 2 /N 2 and CH 4 /N 2 ideal selectivity of a g ZIF-UC-4 membrane (fluorine-based, UC-4 named by Cambridge University) reach 36 and 6.2, respectively. In addition, the CO 2 and CH 4 permeance of the a g ZIF-UC-4 membrane with an independent separation layer and the non-grain boundary has improved to 4752 and 818 GPU, respectively. Under the mixed gas condition, a g ZIF-UC-4 membrane exhibits good separation performance, exceeding the 2019 Mckeown upper bond of CO 2 /N 2. Moreover, a g ZIF-UC-4 membrane has good stability for CO 2 /N 2 and CH 4 /N 2 under continuous operation and variable pressure testing. Hence, the self-supported a g ZIF-UC-4 membrane is a potential candidate for preparing MOF glass membranes with good gas separation performance. [Display omitted] • A self-supported a g ZIF-UC-4 glass membrane is fabricated for gas separation. • The glass membrane can eliminate grain boundary defects by the molten-liquid phase. • The a g ZIF-UC-4 membrane has enhanced CO 2 and CH 4 permeance of 4752 and 818 GPU, respectively. • The a g ZIF-UC-4 membrane has good stability for CO 2 /N 2 and CH 4 /N 2. • The performance of a g ZIF-UC-4 membrane surpasses the corresponding upper bounds. [ABSTRACT FROM AUTHOR]

Carbon molecular sieve (CMS) membranes are ideal candidates for natural gas separation due to their rigid pore structures and stability. The chemical composite and spatial configuration of the used precursors for deriving CMS membranes can greatly influence the final microporous structure and separation performance of the membranes. Most CMS membranes are transformed from amorphous precursors such as polymers nowadays. Here, for the first time, we report a new type of CMS membrane derived from a crystalline porous hydrogen-bonded organic framework membrane (named HCMS). The conversion process has been studied with the characterization of TGA, FTIR, XRD, SEM, and pore size distribution. The effect of pyrolysis temperature on the membrane structure has been investigated to achieve optimized CO 2 /CH 4 separation performance. On the one hand, as the pyrolysis temperature increases from 550 to 650 °C, the pore size distribution of HCMS membrane is narrowed, which is conducive to improving the molecular sieving effect of the membrane. On the other hand, higher ratios of graphitic N and pyrrolic N, which show better affinity for CO 2 molecules than pyridinic N, are obtained on the HCMS membranes, leading to more favorable adsorption of CO 2. The optimized HCMS membrane pyrolyzed at 600 °C shows a remarkable CO 2 /CH 4 selectivity of 128 and excellent separation stability at varying temperatures and pressures. The HCMS membranes derived from the crystalline HOF precursor can also maintain a stable separation performance against physical aging. The results reported in this work may open the door to constructing CMS membranes with the precursor of crystalline porous membranes. Crystalline porous hydrogen-bonded organic framework membrane is employed as a new kind of precursor for the first time to derive carbon molecular sieve membrane with a narrow pore size distribution, which reveals good separation selectivity and stability for CO 2 /CH 4. [Display omitted] • For the first time, a HOF membrane is used as a precursor to derive HCMS membrane. • Ordered porosity of HOF leads to a narrow pore size distribution of HCMS membrane. • Effect of pyrolysis temperature on membrane structure and CO 2 affinity is studied. • The HCMS-600 membrane reveals the optimized CO 2 /CH 4 separation selectivity of 128. • The HCMS-600 membrane is long-term stable at variable temperatures and pressures. [ABSTRACT FROM AUTHOR]

Commercially available polycarbosilane has been chemically modified with primary and secondary amino silane derivatives in order to provide amine-functionalized polycarbosilane as hydrophobic solid sorbent capable of reversibly capturing CO 2 from flue gas streams. CO 2 uptake by the samples was investigated at the molecular level using thermogravimetric analysis under CO 2 atmosphere, in situ DRIFTS analysis, and CO 2 sorption isotherm. The reaction paths and sorption mechanisms were examined by comparing with the CO 2 adsorbing behaviors previously studied for amine-functionalized SiO 2 , and proven to be related to the presence of adsorbed water, as well as the nature of the grafted amino silanes. With effective CO 2 adsorption rate, regeneration capacity at 40–50 °C, and lesser sensitivity to moist due to its hydrophobic Si-C backbone, secondary amine-functionalized polycarbosilane hybrids have potential applications in membrane gas separation through facilitated transport of CO 2 . [ABSTRACT FROM AUTHOR]

Mixed matrix membranes (MMMs) with easy scale-up architectures have shown great potential to achieve superior CO 2 permeance, while their performances are often restricted by the poor interfacial compatibility between fillers and the matrix, and also by blocking of the original channel for gas transmission. Here, a rational design and facile construction of highly permeable MMMs is presented by dispersing triphenyltriazine-based β-ketoenamine-linked covalent organic framework (TpTta-COF) within solution-processable polymer of intrinsic microporosity (PIM-1). An intimate mixing was achieved by improved compatibility of the components induced by the hydrogen bond interaction between -N-H in TpTta-COF and C N of PIM-1. The good adhesion avoids the formation of interface defects, preserving the original gas transmission channel. TpTta-COF particles with strong CO 2 affinity are evenly distributed in the matrix, forming a fast and continuous channel for CO 2 transmission. The physical properties of MMMs were easily tuned, and the as-prepared PIM-1/TpTta–COF–6wt% demonstrates extraordinary stability, high CO 2 permeability and CO 2 /N 2 selectivity, surpassing the β-ketoenamine-free MMM counterparts. This study provides a feasibly pathway for the development of efficient and high performances separation membranes. A facile strategy to improve the compatibility between the matrix and filler through hydrogen-bonded interaction was presented for the construction of high performance MMMs with extraordinary long-term stability. [Display omitted] • A facile strategy to improve matrix-filler compatibility was developed through hydrogen-bonded interaction. • The CO 2 -philic COF fillers and defect-less interface provided fast channels for CO 2 diffusion. • The MMMs exhibited superior CO 2 permeability and CO 2 /N 2 and CO 2 /CH 4 selectivity than the β-ketoenamine-free counterparts. [ABSTRACT FROM AUTHOR]

Here we report the synthesis of branched Tröger's base polymers (x -BTB) with different degree of tetraphenylmethane branch structure by incorporating varied amounts of tetrakis(4-aminopheny)methane into the main chains of Tröger's base polymer (TB). We show that branching increases porosity of x -BTB, leading to improved gas permeability. Specifically, the BET surface area and pore volume of x -BTB polymers increase continuously from 410 to 544 m2 g−1 and 0.584–0.607 cm3 g−1, respectively, for branched polymers containing progressively more branch structure. For CO 2 /N 2 , CO 2 /CH 4 , and O 2 /N 2 binary gas separation, a significant improvement in the gas permeability without obvious compromising the membrane selectivity is observed on the x -BTB membranes with higher branch degree. In particular, for CO 2 /N 2 binary gas separation, the CO 2 permeability of 5 wt%-BTB membrane is 145 Barrers, creating an enhancement of 64.8% as compared to TB membrane. Moreover, x -BTB membranes are much more resistant to physical aging than TB membrane. These results suggest that introduction of tetraphenylmethane branch structure is an effective strategy to fabricate polymeric membranes with high performance suitable for gas separation applications. [Display omitted] • Tetrakis(4-aminopheny)methane (TAPM) exhibited a rigid tetrahedral structure. • Incorporating TAPM into the backbones of TB yielded branched TB polymer (x -BTB). • x -BTB polymers exhibited higher BET surface area than that of TB polymer. • The obtained x -BTB membranes showed a significantly improved gas permeability. [ABSTRACT FROM AUTHOR]

• A novel phthalide-containing polyimide precursor was synthesized and employed to prepare the CMSMs for hydrogen purification. • The structural evolution from precursor to CMS was investigated. • The H 2 separation performance of CMSMs was optimized by the pyrolysis temperature. • The optimized CMSMs show a high H 2 permeability with superior H 2 separation property. Hydrogen-based economy has been considered as a potential solution for energy security and sustainability in the future. And the ever-increasing demand for high-purity hydrogen (H 2) provides an urgent force for the H 2 purification technologies. Herein, a novel polyimide (BATPPP-6FDA) with rigid and contorted structure was synthesized and used as a precursor to fabricate the carbon molecular sieve membranes (CMSMs) for H 2 purification. The structural changes from precursor to CMS were detected and the H 2 separation performance of the membranes was optimized by the pyrolysis temperature. The CMSM pyrolyzed at 550 °C exhibited the highest H 2 permeability of 10054.1 Barrer and moderate H 2 permselectivity due to its highly disordered and turbostratic carbon structure originated from the generally decomposition of thermally labile -CF 3 groups and the lactone rings of phthalide structure in the early stages (<550 °C) of pyrolysis. As the pyrolysis temperature raised, the H 2 permeability of the derived CMSM decreased, and the H 2 permselectivity enhanced greatly. The CMSM pyrolyzed at 800 °C demonstrated a high H 2 permeability of 2622.4 Barrer and superior selectivity with H 2 /N 2 of 524.48, H 2 /CH 4 of 1248.76 and H 2 /CO 2 of 7.51, respectively, which was attributed to the low densification of carbon structure resulting from the rigid and contorted structure of the BATPPP-6FDA precursor. The excellent H 2 separation performance showed a great potential in hydrogen purification application. [ABSTRACT FROM AUTHOR]

Abstract: Membrane technology has been used for hydrogen purification. In this work, two-dimensional g-C3N3 monolayer was proposed as an effective hydrogen separation membrane on basis of density functional theory computations. The structure of g-C3N3 monolayer was optimized first, and the computed phonon dispersion confirmed its stability and supported the experimental feasibility. The permeability of H2 and impurity gases, including CO, N2 and CH4, was investigated. Compared with H2, it is more difficult for the impurity gases to penetrate through g-C3N3 monolayer. The high selectivity of H2 vs. CO, N2, and CH4 ensures a superior capability to conventional carbon and silica membranes. With high H2 permeability and selectivity, g-C3N3 monolayer is a potential H2 purification membrane. [Copyright &y& Elsevier]

The rapid advancement of membrane gas separation processes has spurred the development of new and more efficient membrane materials, including polymers of intrinsic microporosity. The full exploitation of such materials requires thorough understanding of their transport properties, which in turn necessitates the use of powerful and reliable characterization methods. Most methods focus on the permeability, diffusivity and solubility of single gases or only the permeability of mixed gases, while studies reporting the diffusion and solubility of gas mixtures are extremely rare. In this paper we report the use of a mass-spectrometric residual gas analyser to follow the transient phase of mixed gas transport through a benzotriptycene-based ultrapermeable polymer of intrinsic microporosity (PIM-DTFM-BTrip) and a polydimethylsiloxane (PDMS) membrane for comparison, via the continuous online analysis of the permeate. Computational analysis of the entire permeation curve allows the calculation of the mixed gas diffusion coefficients for all individual gases present in the mixture and the identification of non-Fickian diffusion or other anomalous behaviour. The mixed gas transport parameters were analysed by three different approaches (integral, differential and pulse signal), and compared with the results of the 'classical' time lag method for single gases. PDMS shows very similar results in all cases, while the transport in the PIM gives different results depending on the specific method and instrument used. This comparative study provides deep insight into the strengths and limitations of the different instruments and data elaboration methods to characterize the transport in rubbery and high free volume glassy membranes with fundamentally different properties and will be of help in the development of novel membrane materials. [Display omitted] • A critical analysis of the methods to analyse mixed gas transport in membranes is presented. • Mass spectrometry allows the analysis of mixed gas permeation AND diffusion coefficients. • A fit of the entire permeation curve reveals anomalous, non-Fickian transport, if present. • The fit of the permeation curve highlights the limitations of the traditional time lag method. • The presence of CO 2 accelerates the diffusion of CH 4 in both rubbery PDMS and glassy PIM-DTFM-BTrip. [ABSTRACT FROM AUTHOR]

We reported a micro-phase separated PES-g-PEG comb-like copolymer membrane with PEG micro-regions which acted as transfer channels for efficient CO 2 separation. [Display omitted] • PES-g-PEG comb-like copolymers prepared by polycondensation and thiol-ene chemistry. • The density and length of PEG side chains were manipulated for optimization. • Gas separation performance was improved by thermal annealing. • Low MW PEG achieved high grafting density and better phase separation. • The PEG side density is the major factor affecting membrane permeability. As a common CO 2 separation membrane material, polyethylene glycol (PEG) with ether oxygen groups shows high dissolution selectivity to CO 2. However, high molecular weight PEG has strong crystallinity, resulting in low gas flux, while the low molecular weight PEG has poor mechanical properties. Block copolymers containing PEG segments can address this challenge but are difficult to synthesize. In this work, a series of polyether sulfone (PES) comb-like copolymer with PEG side chains were prepared by the polycondensation followed by the thiol-ene click chemistry. By manipulating the density and length of PEG side chains (M n = 550, 1000, 2000) to adjust the fine structure of the micro-phase separation, the gas separation performance of the PES-g-PEG membrane was optimized. The PES-g-PEG polymers have two glass transition temperatures (T g), which are attributed to the PES main chain and PEG side chains. The T g-PEG and T g-PES difference (Δ T g) is highly correlated with the PEG side chain density and can be used to interpret the phase separation degree. The copolymer membrane with shorter PEG side chains achieved higher chain density and more developed micro-phase separation, which was facilitated by thermal annealing. As a result, PES A-g-PEG550 membrane shows the best gas separation performance with the CO 2 permeability of 26.8 Barrer and the CO 2 /N 2 selectivity of 27.6. The permeability variation with the microstructure of PES-g-PEG mostly relies on the side chain density rather than volume fraction or side chain molecular weight. We believe this study of the gas separation performance of the comb-like copolymer material is meaningful for the further application of membrane technology in CO 2 capture and separation. [ABSTRACT FROM AUTHOR]

Novel thermally rearranged polybenzoxazole (TR-PBO) -based silica hybrid membranes were prepared via thermal rearrangement and sol – gel processes, and their gas transport properties were investigated. The pristine TR-PBOs rearranged at different temperatures showed higher fractional free volume (FFV) and d -spacing values than the poly(ortho -hydroxy imide) as a precursor polymer. Gas permeability of TR-PBO – silica hybrids increased with increasing silica content. The increased gas permeability was mainly attributed to increased gas diffusivity, suggesting the formation of free volume holes at polymer/silica interfacial region. The TR-PBO – silica hybrids possessed an outstanding CO 2 /CH 4 selectivity, exceeding the upper bound trade-off line for CO 2 /CH 4 separation. The notable CO 2 /CH 4 selectivity was achieved by synergistic effects of (1) enlarged FFV and d -spacing by the thermal rearrangement towards PBO and (2) the additional formation of characteristic free volume holes with a size-selective CO 2 /CH 4 separation ability at polymer/silica interfacial region by the hybridization with silica. Image 1 • Novel TR-PBO – silica hybrid membranes for gas separation were prepared. • The TR-PBO – silica hybrids possess high gas permeability and CO 2 /CH 4 selectivity. • The CO 2 /CH 4 selectivity is enhanced with increasing silica content. • Free volumes created at polymer/silica interfaces contribute to CO 2 /CH 4 separation. [ABSTRACT FROM AUTHOR]

• A new Pebax based mixed matrix membrane is used for CO 2 /N 2 separation. • The MWCNTs avoid the aggregation of ZIF-8 particles and improve the selectivity. • The MWCNTs provide channels for CO 2 and mechanical properties for membranes. It is imperative to research CO 2 separation membrane in terms of the issues of greenhouse gas emission. In this work, zeolitic imidazolate frameworks-8 (ZIF-8) particles in situ inserted by multiwalled carbon tubes (MWCNTs) (MWCNTs@ZIF-8) were embedded into Pebax matrix to fabricate mixed matrix membranes (MMMs). The incorporated ZIF-8 particles increased the free volume of membranes, resulting in the improvement of the CO 2 permeability. The functionalized MWCNTs in situ inserted into ZIF-8 particles not only avoided the aggregation of ZIF-8 particles but also enhanced the CO 2 adsorption property, resulting in the improvement of the CO 2 /N 2 selectivity. Furthermore, the MWCNTs can provide rapid transport channels for CO 2 molecules between two adjacent ZIF-8 particles and high mechanical properties for membranes. As a result, the MMMs with 8 wt% MWCNTs@ZIF-8 exhibited an excellent separation performance with CO 2 permeability of 186.3 Barrer and CO 2 /N 2 selectivity of 61.3, which surpassed the 2008 Robeson upper-bound. This study provided a new strategy for preparing high-performance CO 2 separation membranes. [ABSTRACT FROM AUTHOR]

• Criteria in selecting microporous meterials for CO 2 separation membrane is given. • The membrane fabrication based on MOFs, POFs, TR polymers, and PIMs is summarized. • The membrane performance in CO 2 separation under differents conditions is analyzed. • The challenge and perspective for future development are pointed out. Membrane technology has gained great attention as one of the promising strategies for carbon capture and separation. Intended for such application, membrane fabrication from various materials has been attempted. While gas separation membranes based on dense polymeric materials have been long developed, there is a growing interest to use porous materials as the membrane material. This review then focuses on emerging organic-containing microporous materials to be used for the fabrication of membranes that are designed for CO 2 separation. Criteria for selecting the materials are first discussed, including physical and chemical properties, and parameters in membrane fabrication. Membranes based on these materials, such as metal-organic frameworks, porous organic frameworks, and microporous polymers, are then reviewed. Finally, special attention is given to recent advances, challenges, and perspectives in the development of such membranes for carbon capture and separation. [ABSTRACT FROM AUTHOR]

Carboxylate-functionalised polymers of intrinsic microporosity (C-PIMs) are highly desirable materials for membrane separation applications. The recently reported method to afford C-PIMs was via an extensive base hydrolysis process requiring 360 h. Herein, a novel and effective method to convert PIM-CONH2 to C-PIM using nitrous acid was studied. The chemical structure of C-PIM was characterised by 1H NMR, 13C NMR, FTIR, elemental analysis, UV-Vis, TGA and TGA-MS. Complete conversion from amide to carboxylic acid groups was confirmed. Decarboxylation of C-PIM was also successfully studied by TGA-MS for the first time, with a loss of m/z 44 amu (CO2) observed at the first degradation stage. TGA also revealed decreased thermal stability of C-PIM relative to PIM-CONH2 under both N2 and air atmosphere. Gel permeation chromatography (GPC) analysis showed continuous molecular weight degradation of C-PIM with extended reaction time. Aromatic nitration was also observed as a side reaction in some cases. [ABSTRACT FROM AUTHOR]