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A fluorescein‐based diamine, 2‐(3,6‐bis(4‐amino‐3‐hydroxyphenoxy)‐9H‐xanthen‐9‐yl) benzoic acid (CADA), was synthesized and copolymerized with Durene and 4,4′‐(hexafluoroisopropylidene) diphthalic anhydride (6FDA) to form a 6FDA‐Durene/CADA (3:2) copolyimide. The copolyimide was thermally cross‐linked at 300–425°C to form a series of decarboxylated cross‐linked polyimides. Compared with the 6FDA‐CADA polyimide, the incorporation of Durene diamine increased gas permeability of the pristine and the thermally cross‐linked polyimides greatly. The copolyimide cross‐linked at 375°C showed separation performance to the O2/N2 gas pair beyond the 1991 Robeson upper limit, while the CO2/CH4 separation property of the copolyimide cross‐linked at 425°C (PI‐425) was close to the 2008 Robeson upper limit. Moreover, the anti‐CO2‐induced plasticization property of the 6FDA‐Durene/CADA(3:2) copolyimides was improved by cross‐linking. The copolyimides cross‐linked at 350°C and above were not plasticized at a CO2 pressure up to 30 atm. This study showed that gas transport property of the decarboxylated cross‐linked polyimides could be improved significantly by the incorporation of bulky diamino moiety. The fluorescein‐based copolyimide had great potentials for gas separation applications. [ABSTRACT FROM AUTHOR]

• Demonstration of mixed matrix membrane using defective ZIF-78, a MOF with the highest CO 2 uptake reported in literature. • Different solvents used to prepare polysulfone lead to smooth or cracked fillers with different membrane free volume. • CO 2 permeability and CO 2 /N 2 selectivity enhanced by 140 % and 129 % with optimally loaded MMMs. Mixed matrix membranes (MMMs) provide a new possibility for membranes to exceed the tradeoff between permeability and selectivity found in pure polymeric membranes. Factors that enhance gas separation performance in MMMs include filler morphology and aspect ratio. High aspect ratio microporous ZIF-78, a metal-organic framework (MOF) demonstrated in literature to have one of the highest carbon dioxide uptake capacities, was successfully synthesized using a solvothermal method. These particles were incorporated into MMMs in non-defective and systematically defective forms by using two common solvents – chloroform and DMF. Detailed characterization of the various membranes was performed using BET, XRD, SEM, EDS, DSC, TGA, FTIR, and a custom-built gas permeability measurement apparatus. Introduction of crystals with no apparent defect results in a more tortuous pathway for permeating gas molecules, demonstrated by nitrogen permeation results. Conversely, for carbon dioxide, strong dipole-quadrupole interaction with ZIF-78 creates excellent permeation pathways through the crystal themselves. The defective system possesses more inter-filler free volume which allow all gas components to permeate more easily, in addition to the original mechanism. The gas separation performance of the resulting MMMs in this work displayed a 140 % improvement of CO 2 permeability and 129 % improvement of CO 2 /N 2 ideal selectivity over pure polysulfone membranes. This work shows the potential of using deliberately designed fillers to increase performance via special pathways for gas molecules. [Display omitted] [ABSTRACT FROM AUTHOR]

We prepared a series of microporous network polyimides (MN‐PIs) derived from tris(4‐aminophenyl)amine (TAPA), and three commercial dianhydrides such as 4,4′‐(hexafluoroisopropylidene) diphthalic anhydride (6FDA), 3,3′,4,4′‐ benzophenonetetracarboxylic dianhydride (BTDA), and pyromellitic anhydride (PMDA). Particularly, in order to obtain these free‐standing membranes before forming insoluble gel products, the self‐crosslinking rate between dianhydride and triamine functional groups was controlled via reaction temperature changing. All MN‐PIs exhibited outstanding thermal stability with high glass transition temperatures (Tg) exceeding 305°C. Gas transport experiments demonstrated that 6FDA‐derived MN‐PI membrane showed the highest gas permeabilities and well‐maintained gas‐pair selectivities rooting from the bulky ‐C(CF3)2‐ linkage groups that inhibited efficient chain‐packing and the comparable backbone rigidity relative to that of PMDA‐derived MN‐PI. The comprehensive gas transport properties of 6FDA‐based MN‐PI membrane approached the 2008 Robeson upper bound for CO2/CH4, showing CO2 permeability of 37.4 Barrer and ideal selectivity of ~56.7. Physical aging monitored for 75 days lead to a decline in gas permeabilities (e.g., 7.8% and 18.4% drop for O2 and N2) and moderately enhanced selectivity (corresponding 14.3% rise for O2/N2). Additionally, 6FDA‐derived MN‐PI also possessed excellent mixed CO2/N2 gas selectivity of 32.9, roughly equaling to its pure gas transport behaviors, which are probably related to the Lewis acid‐base interactions between CO2 and N atoms of tertiary amine in TAPA segments. [ABSTRACT FROM AUTHOR]

Polymer crosslinking via thermal oxidation is a well-established technique that enhances the gas selectivity of a polymer membrane, but usually at the expense of lower gas permeability. As thermal oxidation is typically performed at temperatures higher than the glass transition temperature (T g) of polymers, large energy footprints are incurred while pore structures in asymmetric membranes – the preferred physical configuration of polymer membranes are collapsed. To overcome these drawbacks, here we report a strategy to simultaneously enhance both gas permeability and selectivity via thermal oxidation at sub-T g temperatures. This was achieved with a copolymer consisting a component that enhanced T g , and another component with functional groups that decomposed and induced crosslinking at lower temperatures. We used a series of complementary characterization techniques to pinpoint the actual mechanism underpinning our sub-T g thermal oxidation approach. Crosslinking slightly reduced the d-space between polymer chains but increased polymer fractional free volume and most importantly, inhibited CO 2 -induced plasticization. The pure CO 2 permeability of the crosslinked polymer reached 88.5 Barrer with a CO 2 /CH 4 ideal selectivity of 38.8, while no plasticization behavior was detected at a CO 2 pressure up to 30 atm at 35 °C. When separating CO 2 :CH 4 (1:1) mixed gas at total pressures between 10 and 60 atm, the CO 2 permeability and CO 2 /CH 4 selectivity of this crosslinked polymer were reduced to 55 Barrer and 29 due to competitive permeation. Image 1 • Introducing Durene into 6FDA-MPP enhances T g and decreases crosslinking temperature. • Thermal oxidative crosslinking mechanism of the lactone ring based polyimide was elucidated. • Polyimide is crosslinked at 275 °C that is 75 °C lower than its T g. • Crosslinked polymer shows no plasticization at a CO 2 pressure of 30 atm. [ABSTRACT FROM AUTHOR]

A novel method to determine the individual diffusion coefficients of gases in a mixture during their permeation through polymeric membranes is described. The method was developed in two independent laboratories, using rubbery Pebax ® and glassy Hyflon ® AD60X membrane samples as standards, and validated using the Tröger's base containing Polymer of Intrinsic Microporosity, PIM-EA-TB. Monitoring of the permeate composition in real time by a quadrupole mass spectrometer allowed the analysis of the permeation transient for gas mixtures. Two operation modes, either with a vacuum in the permeate and a direct connection to the mass spectrometer via a heated restriction, or using a sweeping gas and a heated capillary sample inlet, give excellent agreement with the traditional time lag method for single gases. A complete overview of the method development, identification of the critical parameters, instruments calibration, data elaboration and estimation of the experimental accuracy are provided. Validation with PIM-EA-TB, shows that the method can also successfully detect anomalous phenomena, related to pressure and concentration dependency of the transport properties, physical aging or penetrant-induced dilation. Rapid online analysis of the permeate composition makes the method also very suitable for routine mixed gas permeability measurements. [ABSTRACT FROM AUTHOR]

Because of their excellent thermal, chemical and physical properties, as well as high gas selectivity, polyimides are promising polymers for gas separation membranes. However, their commercial use is limited due to their relatively poor solubility and permeability. Here, 5-(2,5-dioxotetrahydrofuryl)-3-methyl-cyclohexane-1,2-dicarboxylic anhydride (DOCDA) was used to improve the solubility of the polyimides, and various methyl-substituted diamines were introduced to increase their permeability, due to the effect of the bulky methyl groups. Polyimides based on DOCDA (DOCDA-PIs), synthesized via one-step solution polymerization, exhibited high solubility in common organic solvents and improved gas permeability due to the non-planar structure of DOCDA and the presence of methyl groups, which disturbed chain packing, an effect that was correlated with increased fractional free volume (FFV) and d-spacing. Co-polyimides based on DOCDA, DOCDA-coPIs, exhibited high gas permeability and CO 2 /CH 4 and O 2 /N 2 selectivity, comparable to commercial polymeric membranes. [ABSTRACT FROM AUTHOR]

The fundamental gas transport properties and physical aging behavior of a series of triptycene-based polyimides with various substitution groups were investigated. Wide-angle x-ray diffraction revealed that the 6FDA-1,4-triptycene polyimides exhibit two chain packing domains with d -spacing values of ~6.7 Å and ~5.3 Å, corresponding to triptycene-induced chain packing disruption and chain segments lacking the triptycene moiety, respectively. Positron annihilation lifetime spectroscopy (PALS) showed a bimodal distribution of microcavity size made up of triptycene cleft cavities that are ~3 Å diameter and larger interchain cavities with an average diameter of ~7 Å. Additionally, PALS confirmed 6FDA-1,4-trip_CH 3 has the lowest fractional free volume, primarily due to smaller contributions from the interchain cavities, and 6FDA-1,4-trip_CF 3 has the largest fractional free volume. It was also found that the addition of substituent groups had a unique and positive effect on the aging properties over nine months, in which the addition of CH 3 and CF 3 groups led to permeability increases of ~20% and ~40%, respectively. This is caused by the combination of the lowered driving force for physical aging, the substituent groups sterically hindering tighter packing with time, and the interconnectivity and/or unblocking of free volume over time through small-scale, local chain motion. [ABSTRACT FROM AUTHOR]

Polyoxyethylene (POE) exhibits great potential for selective CO 2 permeation and is tethered onto poly(methyl methacrylate) (PMMA) or poly(styrene- r -acrylonitrile) (PSt- r -PAN) by atom transfer radical polymerization (ATRP) of POE methacrylate (POEM) to endow preferential CO 2 permeability. The polymer backbones are first prepared from corresponding monomers and 4-(chloromethyl)styrene (Cl-St) with various mixture ratios by free radical polymerization. The POE grafting is then carried out by chain propagation of POEM from the Cl-St moiety by ATRP. The introduction of Cl-St to a polymer backbone is readily controlled when the monomer ratio was less than 2 mol%, and thus the average distance of POE graft chains can be tuned along the polymer backbone. ATRP also defines the length of the POE graft chains. CO 2 separation properties over N 2 of the well-defined hyper-branched polymers are investigated by comparing permeability of CO 2 and N 2 pure gases. The gas permeabilities increase with increase of POE content, and the resulting CO 2 /N 2 selectivity is also enhanced in comparison to the pristine polymers and 35 and 40 for PMMA-based and PSt- r -PAN-based hyper-branched copolymers, respectively. Higher POE content indeed gives higher diffusion coefficient for both of CO 2 and N 2 , but the CO 2 and N 2 diffusivities are almost the same. Thus the gas permeation progresses under solubility control. The CO 2 permeability is 135 Barrer with the CO 2 /N 2 selectivity 42, when the POE content is 76 wt% of PSt- r -PAN-based hyper-branched copolymer. [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]

Gas separation by membrane carries many advantages over other methods of gas separation, including the amenability of the gas separation process to simplification and scaling up, and the elimination of the need for phase change of the gas. Material composition is, by far, the most important factor in determining the gas separation effectiveness of a membrane. This article is a review of the existing research on polymers as used in the separation of carbon dioxide/methane (CO2/CH4), generally focusing on polyimide and polysulfone compounds. Data on thermally rearranged (TR) polymer membranes and mixed matrix membranes were also included. In this study, the membrane performance of different polymeric materials was examined by comparing the data on CO2/CH4 selectivity obtained through a literature review and the upper bound proposed by Robeson in 2008. Results showed that polyimide and polysulfone membranes are highly applicable to the separation of CO2/CH4 gas mixtures: polyimide showed particular promise for commercial implementation. Polysulfone membranes exhibited high selectivity but low CO2 permeability that failed to exceed the upper bound. However, case studies suggested that polysulfones in the hollow fiber membrane form have a wide variety of applications in an industrial setting. On the other hand, the TR polymer membranes, which are currently used for research, had a CO2 permeability of 5-5,903 Barrer and CO2/CH4 selectivity of 3.8-124, which exceeded the upper bound proposed by Robeson. We, thus, came to the conclusion that future research on CO2/CH4 gas separation should focus on polysulfone, polyimide, and TR membranes as materials for economically efficient and highly effective gas separation membranes. [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]

Polyvinylchloride (PVC)/Styrene-Butadiene-Rubber (SBR) (PVC:SBR, (95:5) (w/w)) blend gas separation membrane filled with zeolite was prepared by solution-casting method using tetrahydrofuran (THF) as solvent. Zeolite was also applied as inorganic filler additive in membrane preparation. The zeolite loading and pressure effects on the gas separation performance of the membranes were studied for pure He, N, CH, CO gases. The obtained results indicated that permeability was increased and (CO/N), (CO/CH) and (N/CH) selectivities all were decreased by the increase of zeolite loading ratio. Moreover, it was found that increase of feed pressure led to an increase in membrane gas permeability for all of prepared membranes. Results showed that the (CO/N) and (CO/CH) gas pair selectivities were decreased by the increase in feed pressure for all prepared membranes. Conversely, opposite trend was found for (N/CH) selectivity at 50 wt} zeolite loading ratio. The (N/CH) selectivity was improved from 1.41 to 2.33 by increase in pressure force from 2 to 8 bar. Differential scanning calorimetry was also utilized for the membrane thermal stability investigation. The results showed the glass temperature (T) and melting temperature (T) obviously were improved from 340.1 to 467.1 K and from 359.5 to 516.9 K, respectively, by the increase in zeolite loading ratio from 0 to 50 % wt in prepared membranes. [ABSTRACT FROM AUTHOR]

Abstract: Using CO2/N2 gas separation membranes for post-combustion capture, the most important problem is how to create the driving force efficiently because the feed flue gas has only ambient pressure and a relatively low CO2 content. In order to fulfill the separation target – 95mol% CO2 purity and appropriate degree of CO2 separation – multi-stage systems are necessary using feasible membranes. This paper describes a detailed parametric study for multi-stage membrane systems used in a coal-fired power plant. According to the above-mentioned boundary conditions, the investigation process was divided into two steps: (a) energy consumption and (b) capture cost analyses. In the first step, by varying the position of the compressors and vacuum pumps and recycling the flue gas to the feed side, cascade variants were developed and analyzed in detail. The cascade system was integrated in the 600MW North Rhine-Westphalia reference power plant and compared with the chemical absorption process. In the second step, an economic model was developed to make a further analysis of the cascade system. A correlation was established between the membrane parameters (selectivity, permeability) and system performance (energy consumption, capture cost). [Copyright &y& Elsevier]

Abstract: The effects of incorporation of heterocyclic moieties into fluorinated poly(ether imide) membranes on their gas transport properties were investigated. Four novel fluorinated poly(ether imide) (PEI) membranes were prepared from four different bis(ether amine)s namely, 4,4-bis[3′-trifluromethyl-4′(4′′-aminobenzoxy)bezyl]biphenyl (BAQP); 1,4-bis[3′-trifluromethyl-4′(4′′-aminobenzoxy)bezyl] benzene (BATP); 2,6-bis[3′-trifluromethyl-4′(4′′-aminobenzoxy)bezyl]pyridine (BAPy) and 2,5-bis[3′-trifluromethyl-4′(4′′-aminobenzoxy)bezyl]thiophene (BATh), and a fluorinated dianhydride, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane (6FDA) as a common dianhydride. Gas transport properties of these membranes were measured to investigate the effect of chemical structure on gas permeation and diffusion processes over four different gases (e.g., CH4, N2, O2 and CO2) at different temperatures (e.g., 35, 45 and 55°C) at an applied pressure of 3.5bar. It has been found that at 35°C the permselectivities of BAPy and BATh based polymeric membranes (6.4 and 6.6, respectively) toward O2 relative to N2 are higher in comparison to BAQP and BATP (5.5 and 5.3, respectively) containing PEI membranes. The permeability coefficient of CO2 for BAPy and BATh (51.92 and 45.31, respectively at 35°C) based PEI membranes were observed to be much higher than BAQP and BATP based membranes (36.61 and 33.51, respectively at 35°C) with comparable selectivity values of CO2 relative to CH4. All these membranes exhibit higher CO2/CH4 selectivity than those of common glassy polymers e.g., cellulose acetate, polysulfone and polycarbonate. The order of permeability of these gases was found as CO2 >O2 >N2 >CH4. The temperature dependency of permeation and diffusion processes enables to calculate the activation energies of the permeation and diffusion processes for these four different gases through four PEI membranes. [Copyright &y& Elsevier]

This paper presents a comparison of the impact of H+ and N+ ion irradiation on the chemical structure, microstructure, and gas permeation properites of the polyimide, Matrimid®. While irradiation with both ions resulted in evolution of chemical structure with loss of functional groups and crosslink formation, there was greater modification of polyimide structure following N+ irradiation at similar total deposited energy. Irradiation with N+ resulted in simultaneous large increases in permeance and permselectivity at comparatively low ion fluences or irradiation time. For example, irradiation at 4 × 1014 N+/cm2 resulted in a 2.5 fold increase in He permeance with a selectivity of He/CH4 of 340. Much higher H+ fluences were required to achieve similar total deposited energy and combined increases in permeance and permselectivity. The larger modification in chemical structure and gas permeation properties following N+ irradiation was attributed to the relatively large energy loss and damage from the nuclear energy relative to electronic energy loss. [ABSTRACT FROM AUTHOR]

Abstract: Capture of CO2 from flue gases produced by the combustion of fossil fuels and biomass in air is referred to as post-combustion capture. Chemisorbent processes are considered to be the most feasible method and are already at an advanced stage of development, but gas separation membranes are attracting more and more attention as a possible alternative. This paper describes a detailed parametric study of mass and energy balances for a simulated single membrane process. Typical operating conditions (CO2 concentration in the flue gas, pressure and temperature, etc.) together with the influence of the membrane quality (permeability, selectivity) and membrane area on membrane performance (CO2 separation degree and CO2 purity) are simulated over a wide range of parameters. [Copyright &y& Elsevier]

Abstract: The present paper discusses the tendency of solution-cast Hyflon® AD membranes to retain unexpectedly high amounts of solvent, the possible reasons of this phenomenon and its effect on the membrane performance. Dense membranes, prepared by solution-casting and subsequent evaporation, showed large differences in their thermal, mechanical and transport properties, depending on the residual solvent content. Complete solvent removal required heating under vacuum up to well above the glass transition temperature. Analysis of the permeability, diffusion and solubility coefficients of six permanent gases showed that plasticization by the residual solvent reduces the permselectivity and increases the permeability. Data of solution-cast membranes after complete solvent removal compare well with those of a melt-pressed sample. Experimental gas transport parameters were confronted with simulated data, obtained by the Gusev–Suter Transition-State Theory (TST) method and by molecular dynamics (MD) simulations. 1H High Resolution Magic Angle Spinning Nuclear Magnetic Resonance spectroscopic analysis of the residual solvent in the polymer matrix did not reveal a particular interaction between polymer and solvent, suggesting that the solvent retention is mainly diffusion controlled. [Copyright &y& Elsevier]

Abstract: A series of poly(dimethylsiloxane) (PDMS) films substituted with different bulky groups in the pendent chain having amino and hydroxy functional groups have been prepared. FT-IR, 1H- and 13C NMR, GPC, TGA, DSC and WAXD techniques were used to characterize the products. The gas transport properties, viz., permeability, solubility and diffusivity, of the functionalized PDMS films were determined for N2, O2, CH4 and CO2 gases. With the incorporation of increasingly bulkier substituents the permeability coefficient was found to decrease. The decrease in value was observed to be low compared to other reported bulky substituents. The glass transition temperature increases with increasing bulkiness of the substituent. The fractional free volume (FFV) and d-spacing values were also determined and correlated with the permeability coefficients. The permselectivity of these films for O2/N2 and CO2/CH4 gas pairs increases due to increase in the solubility selectivity value. Among these, the PDMS film functionalized with 2,6-diisopropyl phenyl amino-hydroxy groups shows high permselectivity value for the studied gas pairs without much reduction in the permeability value. [Copyright &y& Elsevier]

Mixed matrix membrane is a highly potential material that may possibly overcome the challenges faced by the membrane technology today. We explored the gas separation performance of a modified Matrimid/C60 mixed matrix membranes. The membranes were prepared by physically blending a series of benzylamine-modified fullerene, C60 with pure Matrimid 5218. The bulk Matrimid and the dispersed benzylamine-modified fullerene molecules show strong interfacial interactions as reflected by a significant increase in the Tg of the film with C60 loading.Gas permeabilities of He, O2, N2, CH4, and CO2 show a monotonous decrease with increasing benzylamine-modified C60 content. The percentage of permeation reduction at 10 wt.% benzylamine-modified C60 loading is 32% for He (kinetic diameter of 2.6 A˚), while 41.7 and 41.5%, respectively, for the O2 (3.46 A˚) and N2 (3.64 A˚) gas pair, 45.2 and 47.0%, respectively, for CH4 (3.8 A˚) and CO2 (3.3 A˚) gas pair. The decrease of the gas permeability with increasing C60 compositions is found to be mainly due to the decrease in the gas diffusivity. The presence of the benzylamine-modified C60 seems to serve as impenetrable volumes and rigidifying elements within the polymer matrix. Therefore, the diffusivity of larger penetrants is reduced to a greater extent than the smaller penetrants and results in the increase of He/N2 selectivity. This is also supported by the sorption data, which reveals that the Langmuir sorption capacity decreases with increasing C60 loading. The increase in the glass transition temperature and the measured density indicate that the presence of the chemically modified C60 molecules have rigidified the polymer and pulled the matrix together. [Copyright &y& Elsevier]

The intrinsic gas transport properties of permeation, diffusion and sorption for He, O2, N2, CH4 and CO2 in aromatic polyimide, poly(1,5-naphthalene-2,2′-bis(3,4-phthalic) hexafluoropropane) diimide (6FDA-1,5-NDA) dense membranes were investigated. The permeation of pure gases of He, O2, N2, CH4 and CO2 was measured with a temperature-controlled permeation cell while the sorption isotherm was obtained from the Cahn 2000 microbalance sorption cell.The 6FDA-1,5-NDA membrane has a selectivity of 49 for CO2/CH4 with a permeability of 22.6 Barrers for CO2 under 10 atm at 35 °C. The Henry’s diffusivity holds a dominating effect over the Langmuir diffusivity and decreases in the order of O2>CO2>N2>CH4, in fair agreement with the apparent diffusivity. The activation energies of permeation and diffusion increase with increasing gas kinetic diameters in the order of CO2, O2, N2 and CH4.The solubility of gases tested adopts a parallel trend with their critical temperatures. Upon pressure acceleration, the gas diffusivity increases while the solubility decreases. The overall gas permeability of 6FDA-1,5-NDA decreases with increasing pressure, which can be explained by using the dual-mode sorption model and the partial immobilisation model. More than 50% of the entire total gas sorbed is distributed in the Langmuir environment when pressure is less than 25 atm. The fractional mobility of Langmuir species decreases while the fractional mobility of the Henry species increases when the feed pressure increases. CO2 exhibits the most significant pressure-dependent properties due to its the strongest interaction and highest condensability. [Copyright &y& Elsevier]

A new azide modified biscatechol monomer was first obtained and characterized by single-crystal XRD, but its polymerization only afforded a low molecular weight azide-containing polymer of intrinsic microporosity (PIM-N3). The high-molecular PIM-N3 was then obtained via post-modification on PIM-Me, prepared by the fluoride-mediated PIM synthesis method developed by our group in 2015. The crosslinking temperature was set at 220 °C based on the thermogravimetric analysis (TGA) data. The thermal self-crosslinking of PIM-N3 significantly enhanced gas permeability. The 6-h crosslinked PIM-N3 (PIM-N3-6 h) exhibited the best combination of CO 2 permeability, and selectivity for CO 2 over N 2 and CH 4 , traversing the 2008 Robeson upper bound. [Display omitted] • An azide modified biscatechol monomer (TTSBI-N 3) was first synthesized, and its single crystal structure was obtained. • PIM-N3 was prepared by post-modification on a high M w PIM-Me obtained via fluoride-mediated polymerization method. • Thermal crosslinking of PIM-N3 at selected 220 °C significantly increased gas permeabilities. • The PIM-N3-6 h showed the best combination of CO 2 /N 2 and CO 2 /CH 4 selectivities and CO 2 permeability. [ABSTRACT FROM AUTHOR]