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• Matrimid-based MMM incorporating NH 2 -MIL-101(Cr) impregnated by IL was fabricated. • The CO 2 permeability increased from 7.33 to 19.22 Barrer (about 162%). • The CO 2 /CH 4 selectivity significantly increased from 34.9 to 113.1 (about 224%). • Immobilizing IL in MOF improved interfacial adhesion in polymer/filler interphase. • MMM containing IL@NH 2 -MIL-101 suppressed CO 2 induced plasticization up to 25 bar. Immobilizing an ionic liquid (IL) on a metal-organic framework (MOF) is proposed as a novel selective and CO 2 facilitated transport material to improve gas perm-selectivity and plasticization pressure of Matrimid-based mixed matrix membranes (MMM) for CO 2 /CH 4 separation. NH 2 -MIL-101(Cr) was synthesized and then impregnated with 1-butyl-3-methyl imidazolium bis(trifluoromethanesulfonyl)imide ([Bmim][Tf 2 N]) to prepare IL@NH 2 -MIL-101(Cr). The particles were analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) analysis, and scanning/transmission electron microscopy (SEM/TEM). The particles were then dispersed in Matrimid to prepare MMM with 3, 5, and 7 wt.% contents. The membranes microstructure was investigated by FTIR and XRD, and the uniformity of MOF distribution was examined by SEM. Differential scanning calorimetry (DSC) displayed an increase in glass transition temperature (T g) for the MMM associated with the polymer chains rigidification in the polymer/filler interphase. Permeation experiments showed that maximum separation performance was found for the MMM containing 7 wt.% IL@NH 2 -MIL-101 with increased CO 2 permeability (162%) and CO 2 /CH 4 selectivity (224%) over pristine Matrimid. This MMM increased plasticization pressure of the Matrimid membrane from 12 to 25 bar. Tensile strength and Young's modulus of the optimum MMM were 25% and 37% higher than those of pristine Matrimid membrane, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

Zeolite crystals as inorganic fillers were widely applied in fabricating mixed matrix membranes (MMMs) for CO 2 separation. The poor filler-matrix interaction and the aggregation of high-loaded fillers in MMMs restrict their advantage of overcoming the trade-off limitation between permeability and selectivity. The novel MMMs with two-dimensional (2D) MFI nanosheets as inorganic fillers and Pebax MH 1657 as the matrix were synthesized and applied to achieve an efficient separation of CO 2 /CH 4 gas mixture for the first time. The large interfacial contact areas between MFI nanosheets and Pebax matrix improve their compatibility to form defect-free MMMs with better mechanical properties. The high-aspect-ratio MFI nanosheets function as solid and selective barriers to make MMMs possess a significant promotion in both CO 2 permeability and CO 2 /CH 4 selectivity without the trade-off limitation. The MMM containing 5 wt% of MFI nanosheets exhibited the optimum performance with CO 2 permeability of 159.1 Barrer and CO 2 /CH 4 selectivity of 27.4. The as-prepared MMMs showed an improvement of 63.5% in CO 2 permeability and 76.4% in CO 2 /CH 4 selectivity, compared to pristine Pebax membranes. [Display omitted] • MFI nanosheets were used as 2D inorganic fillers to fabricate new Pebax-based MMMs. • CO 2 permeability and CO 2 /CH 4 selectivity of MMMs could be increased by 63% and 76%. • MFI nanosheets with preferential adsorption offered short transport paths for CO 2. • 2D nanosheets as fillers provided shorter CO 2 diffusing paths than particulate MFI. • MMMs possessed promoted separation performances without trade-off limitation. [ABSTRACT FROM AUTHOR]

One of the biggest challenges in membrane-based gas separation application is how to obtain highly efficient membranes with both high permeability and selectivity. To achieve this target, we reported a novel simple method to modify polymer of intrinsic microporosity (PIM-1) membranes by direct sulfonation using sulfur trioxide (SO 3)/dichloromethane solution to get a series of sulfonated PIM-1 (SPIM-1) membranes. The SO 3 H group was bonded to the main chain of the SPIM-1 and distributed homogeneously in the entire membrane that was confirmed by FTIR, XPS and SEM/EDS mapping. As the sulfonation time increased from 2 to 6 min, the concentration of sulfonic acid (SO 3 H) group in the repeat unit increased from 12.3% to 30.1%. The introduction of SO 3 H groups resulted in a decreased surface area and denser polymer chain packing. The resulting SPIM-1 membranes exhibited huge improved selectivity with separation performance much better than the pristine PIM-1. In which, the 6 min sulfonated PIM-1 membrane (SPIM-1-6) showed excellent gas separation properties with its performance approaches or even exceeds the latest trade-off curves for O 2 /N 2 , CO 2 /N 2 , H 2 /N 2, and CO 2 /CH 4. This is due to the SO 3 H group induced a compact packing of polymer main chain that remarkably enhanced the diffusion selectivity. The 60 days aged SPIM-1-6 demonstrated even higher gas pair selectivity, and the H 2 /N 2 and O 2 /N 2 selectivity reached as much as 125 and 8.43 coupled with H 2 and O 2 permeability of 1077 and 73.4 Barrer, respectively. Additionally, the SPIM-1-6 also showed excellent mixed-gas separation properties, with CO 2 /CH 4 mixed-gas selectivity over 40 coupled with CO 2 permeability of 296 Barrer even at the upstream pressure of 20 bar. These results suggested the great potential for this mild sulfonation method and sulfonated PIM-1 membranes in advanced membrane-based gas separation applications. [Display omitted] • PIM-1 membrane was sulfonated by SO 3 /dichloromethane solution at mild condition for the first time. • SPIM-1 membranes showed a denser chain packing than that of PIM-1. • SPIM-1-6 exhibited a H 2 /N 2 separation property above the latest upper bound. • 60 days aged SPIM-1-6 showed remarkable O 2 /N 2 and CO 2 /CH 4 selectivity of 8.53 and 65. • SPIM-1-6 showed both high P CO2 of 296 Barrer and a CO2/CH4 of 40 for mixed-gas testing at 20 bar. [ABSTRACT FROM AUTHOR]

Processes, such as biogas upgrading and natural gas sweetening, make CO2/CH4 separation an environmentally relevant and current topic. One way to overcome this separation issue is the application of membranes. An increase in separation efficiency can be achieved by applying mixed-matrix membranes, in which filler materials are introduced into polymer matrices. In this work, we report the covalent triazine framework CTF-biphenyl as filler material in a matrix of the glassy polyimide Matrimid®. MMMs with 8, 16, and 24 wt% of the filler material are applied for CO2/CH4 mixed-gas separation measurements. With a CTF-biphenyl loading of only 16 wt%, the CO2 permeability is more than doubled compared to the pure polymer membrane, while maintaining the high CO2/CH4 selectivity of Matrimid®. [ABSTRACT FROM AUTHOR]

The effects of a sub-nanometer grain boundary in all-silica chabazite (CHA) zeolite membranes on their permeation properties were investigated by non-equilibrium molecular dynamics (NEMD). The results indicated that at the total pressure of 0.5 MPa, at 298 K, the CO 2 selectivity toward CH 4 drastically increased due to the presence of a grain boundary region inside the membrane. This was a consequence of the selective condensation of CO 2 in the grain boundary. The calculated CO 2 selectivity for the perfect crystal CHA membranes was in the range of 183–278 and depended on the surface orientation of the modeled membranes. Notably, the selectivity was comparable to the previously reported values. Two different membrane structures containing a grain boundary of approximately 0.6 nm were modeled using NEMD. In the case of the grain boundary located inside the membrane, the condensed CO 2 molecules in the grain boundary region prevented permeation of CH 4 , resulting in significantly increased CO 2 selectivity. The NEMD results suggest that compared to perfect zeolite crystal membranes, the presence of a grain boundary inside a CHA membrane increases the membrane performance, selectivity, and permeability. [Display omitted] • The mixture gas permeation through sub-nanometer grain boundary in all-silica chabazite (CHA) zeolite membranes are investigated and demonstrated by non-equilibrium molecular dynamics (NEMD). • For perfect crystal membrane models, calculated selectivity and permeability were comparable to the previously reported values. • At the total pressure of 0.5 MPa, at 298 K, the CO 2 selectivity toward CH 4 drastically increased due to the presence of a grain boundary region inside the membrane. • The presence of a grain boundary inside a CHA membrane would increase the membrane performance, selectivity, and permeability. [ABSTRACT FROM AUTHOR]

[Display omitted] • UiO-66-PEI@pSBMA particles were fabricated by Schiff's base and ATRP reaction. • PEI grafting on UiO-66-NH 2 can enhanced the interface morphology of MMMs. • Polyzwitterion can strongly bonded water to facilitate the transport of CO 2 molecule. • The PI/UiO-66-PEI@pSBMA MMM shows the optimum CO 2 /CH 4 selectivity of 60.32. In this study, UiO-66-NH 2 fillers were grafted with polyethyleneimine (PEI) and poly(sulfobetaine methacrylate) (pSBMA) and subsequently incorporated into a sythesized 6FDA-ODA matrix to prepare mixed matrix membranes (MMMs). XRD, FTIR, SEM and TGA characterization techniques were used to evaluate the structure and properties of UiO-66-PEI@pSBMA and MMMs. It was found that the introduction of branched PEI and pSBMA can not only avoided the agglomeration of UiO-66-NH 2 , but also improved the compatibility between the polymer matrix and filler particles. In addition, the UiO-66-PEI@PSBMA was able to bond with a noticeable amount of amino groups and water molecules, and to promote the transportation of CO 2 in the membrane. The resulting PI/UiO-66-PEI@pSBMA MMM achived remarkably enhanced gas perm-selectivity compared to pristine 6FDA-ODA membrane and exceeded the Robeson upper bound. The strategy of PEI and polyzwitterion post covalent modification for UiO-66-NH 2 provides an effective way to eliminate interface defects and enhance the gas separation of MMMs. [ABSTRACT FROM AUTHOR]

Continuous SSZ-13 zeolite membranes were reproducibly synthesized on the inner surface of 7-channel monolith supports for the first time. Packing density and mechanical strength were much greater than those using normal tubular and disc membranes. The membrane in the central channel of monolith was thinner than these of the side channels. The best monolith supported SSZ-13 membrane (with spacers) showed a CO 2 /CH 4 selectivity of 72 and a CO 2 permeance of 163 × 10-8 mol/(m2 s Pa) at pressure drop of 2.0 MPa and feed flow rate of 20 standard L/min for an equimolar CO 2 /CH 4 mixture. Such separation performance was higher than most of zeolite membranes prepared on single-channel tubes or discs. The effects of temperature, pressure drop and fluid state on separation performance of the membranes were investigated. The extent of concentration polarization through monolith supported membrane was modelled by the concentration polarization index (CPI). Increasing feed flow rate and inserting spacers into the channels were effective ways to reduce the negative influence of concentration polarization. The latter way was more effective for our monolith supported membranes than the former because the dead volume was reduced greatly. Carbon dioxide permeance and CO 2 /CH 4 selectivity increased by 24% and 85%, respectively, when the CPI increased from 0.79 (without spacer) to 0.89 (with spacer) at feed flow rate of 20 standard L/min. [Display omitted] • Monolith-supported SSZ-13 membranes were prepared for the first time. • Monolith membranes were still highly CO 2 -selective at high pressures. • Their separation performances exceeded those of most tubular and disc membranes. • The model of concentration polarization was established and discussed. [ABSTRACT FROM AUTHOR]

This work aims at obtaining a systematic description and prediction of the multicomponent gas separation behavior of membranes, using the Non-Equilibrium Lattice Fluid (NELF) model for gas sorption and the Standard Transport (ST) model for gas permeation. The scheme is applied to a comprehensive analysis of CO 2 /CH 4 separation with cellulose acetate membranes. A dedicated experimental campaign (pressure-volume-temperature (P V T), differential scanning calorimetry (DSC) and pure gas sorption tests) was performed to obtain reliable model parameters, accounting also for crystallinity. The approach was validated against a complete set of literature data, including mixed gas sorption and permeation. The parameters obtained were used to perform predictive simulations of mixed CO 2 /CH 4 sorption and permeation in a wide mixture composition range. The NELF model accurately predicts the effect of temperature on sorption, as well as the strong competitive exclusion of CH 4 when CO 2 is present, that enhances the solubility-selectivity. The ST model correctly estimates the experimentally observed lower-than-ideal CO 2 /CH 4 perm-selectivity. The model shows that low perm-selectivity is due to mixed gas diffusivity-selectivity (which is not available experimentally): even though solubility-selectivity increases in the mixed gas case, diffusivity-selectivity suffers a larger departure from pure gas conditions, ultimately leading to a lower perm-selectivity under multicomponent conditions. [Display omitted] • A framework to model gas transport through semicrystalline glasses was presented. • Sanchez-Lacombe equation of state parameters were obtained for cellulose acetates. • The models gave good predictions of CO 2 /CH 4 mixed-gas solubility and permeability. • A comprehensive analysis of mixed-gas sorption and diffusion effects was carried out. [ABSTRACT FROM AUTHOR]

• ZIF-301 MOF was incorporated into 6FDA-DAM polyimide membrane. • Solvent exchange approach was used to remove high-boiling-point solvent in membrane. • Incorporating ZIF-301 enhanced CO 2 permeability and CO 2 /CH 4 selectivity of 6FDA-DAM. Compared with traditional separation methods, membrane-based technology shows advantages in energy efficiency for natural gas purification. To overcome the performance trade-off of conventional polymeric membranes, in this study, ZIF-301 MOF was employed as novel filler to fabricate 6FDA-DAM polyimide mixed-matrix membranes (MMMs) for CO 2 /CH 4 separation. A solvent exchange approach was proposed to remove the high-boiling-point solvent used for fabricating the MMMs. The microstructures and physico-chemical properties of the ZIF-301 fillers and ZIF-301/6FDA-DAM MMMs were characterized by SEM, EDX, XRD, IR, TGA, DSC and high-pressure sorption isotherms. The CO 2 /CH 4 transport properties through the MMMs were evaluated by permeation measurement at various feed pressures and analyzed by solution-diffusion model. The results showed that the incorporation of ZIF-301 into 6FDA-DAM enhanced both the CO 2 permeability and CO 2 /CH 4 selectivity, attributing to the preferential CO 2 sorption and aperture molecular sieving effect of the ZIF-301 filler. The MMM with optimal ZIF-301 loading of 20 wt% exhibited CO 2 permeability of 891 barrer and CO 2 /CH 4 of 29.3 that surpassed the 2008 Robeson upper-bound, suggesting that ZIF-301 based membrane could be a potential candidate for natural gas purification. [ABSTRACT FROM AUTHOR]

Polymeric membranes performance in gas separation can be improved by using zeolites as the filler in the polymer matrix to form mixed matrix membranes (MMMs). Pure-silica Si-CHA zeolite and Pebax-1657 copolymer are individually capable of separating acid gases from natural gas. However, the corresponding MMM has not been investigated in the literature. Therefore, in this work, Si-CHA zeolite was incorporated in the Pebax-1657 copolymer by solvent evaporation method to evaluate its performance in CO 2 separation from CH 4. The fillers distribution in the polymeric matrix, structural characteristics, and interaction of fillers with the polymer in MMMs were characterized via SEM, FTIR, DSC, XRD, and stress-strain analyses. Moreover, the CO 2 /CH 4 separation tests of the membrane as a function of zeolite content and applied feed pressure was explored. The structural analyses of the membranes showed the best filler distribution and the filler-polymer interaction in the membrane for the sample containing 10 wt% of the filler. Furthermore, pure gas permeation tests revealed that the best separation performance was obtained for the same membrane at an applied gauge pressure of 4 bar. In this membrane, 103% improvement in CO 2 permeability, and 71% increase in CO 2 /CH 4 ideal selectivity was achieved compared to the neat polymeric membrane. The separation performance of the MMM 10% was evaluated using CO 2 –CH 4 mixed gas. In this situation, decreased CO 2 /CH 4 separation factor was observed due to the plasticization of PEO chains with polar CO 2 gas. • Si-CHA zeolite was incorporated into Pebax-1657 membrane for CO 2 separation from CH 4. • The membranes include one polymer-based layer and one inorganic-based layer. • The MMM containing 10 wt% of the filler showed the best separation performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nickel-Organic Framework was synthesized. • Crystal structure of the title compound was determined. • GCMC simulations performed on synthesized Frameworks. • DFT calculations were performed at B3LYP/Def2-TZVP level of theory. • Experimental parameters were compared with calculated ones. Two new Metal-organic frameworks, [Na 1 Ni 3 (µ 3 -OH)(µ 5 -BTC)(µ 6 -BTC)(H 2 O) 3 ].4H 2 O (BTC = Benzene tri-carboxylate ion) (1) and [Na 1 Co 3 (µ 3 -OH)(µ 5 -BTC)(µ 6 -BTC)(H 2 O) 3 ].4H 2 O (2) were synthesized under hydrothermal conditions and characterized by FT-IR, TGA, elemental analyses, single crystal and powder X-ray diffraction techniques. The porous structure of 1 and 2 were investigated by BET, crystal voids, topological analysis, gas adsorption and GCMC simulations. In the pressure range from 0.1 to 1.5 bar the adsorption selectivity of CO 2 over CH 4 at 273 K, 288 K and 298 K, is high in the activated MOFs. However, the adsorption selectivity reduces to 1.3 by increasing the pressure to 10 bar. GCMC simulations indicated probable interactions of CO 2 around metal nodes and CH 4 near the carboxylate groups. Experimental gas adsorption together with the GCMC simulation suggested 1 and 2 can be potential candidates for greenhouse gas capture or CO 2 /CH 4 separation. [ABSTRACT FROM AUTHOR]

Polymers of intrinsic microporosity (PIMs) with high free volumes have been synthesized by incorporating contorted rigid moieties into polymers backbones. Despite their many appealing properties, membranes made of these polymers have not been used industrially because of their fast physical aging. The unprecedented CO 2 permeability and satisfactory CO 2 /N 2 and CO 2 /CH 4 selectivity of PIMs have led to establishing the new 2019 upper bounds for the gas mixtures. This article reviews recent advances in the field of PIM-based membranes. It discusses polymer synthesis strategies to modify PIM structures such that the resulting membranes have improved CO 2 separation performance and lower physical aging. The strategies include the use of monomers with suitable side chains, kinked moieties, and stable structures. [ABSTRACT FROM AUTHOR]

• Polyimide dense membranes were crosslinked using a liquid-phase crosslinking process. • The membranes were crosslinked in various solvents. • The crosslinking degree of the membranes: NMP > DMF > DMSO > THF > chloroform. • The solvent effect was verified using Hansen solubility parameter. • The better compatibility offered a higher degree of crosslinking. The crosslinking within a polyimide membrane was investigated by means of a liquid-phase crosslinking process (L-PCP) in which a polymer and crosslinker are mixed in a solvent to prepare crosslinked membranes in a single step. To prepare crosslinked membranes, the polyimide polymer was dissolved in various solvents including tetrahydrofuran (THF), chloroform, dimethylsulfoxide (DMSO), dimethylformamide (DMF), and N-methylpyrrolidone (NMP) with p-phenylenediamine as a crosslinker, and the crosslinked membranes were then obtained by casting the polymer solution. The crosslinked membranes showed different degrees of crosslinking according to the solvent (NMP > DMF > DMSO > THF > chloroform). The highest degree of crosslinking was obtained with the membrane crosslinked in NMP, which also presented the best chemical stability and plasticization resistance against condensable CO 2 gas. On the other hand, the membranes crosslinked in THF and chloroform exhibited poor chemical stability and plasticization resistance. This difference in crosslinking degrees arising from the use of various solvents can be correlated with solubility parameters of the polymer and solvent. A good solvent can swell the polymer chains and provide higher crosslinker diffusivity and more effective crosslinking conditions, and vice versa. For CO 2 /CH 4 separation, the highest CO 2 permeability was obtained from the crosslinked membrane in THF and chloroform (~8.2 barrer) with a modest CO 2 /CH 4 selectivity of 35 at high pressure (30 barg) despite plasticization. Moreover, the highest CO 2 /CH 4 selectivity (~39) could be obtained with the membranes crosslinked in DMSO and DMF with CO 2 permeability of 5 barrer. The membrane crosslinked in NMP exhibited the lowest CO 2 permeability of 2.8 barrer at 30 barg due to the highly inter-crosslinked polymer structure, which hinders gas diffusion. [ABSTRACT FROM AUTHOR]

• Triethylenetetramine incorporated UiO-66 has shown high CO 2 adsorption capacity. • The CO 2 /CH 4 selectivity was also higher for triethylenetetramine loaded UiO-66. • Heat of CO 2 adsorption was 54.6 KJ/mole for triethylenetetramine loaded UiO-66. • The CO 2 adsorption capacity was constant in multiple CO 2 adsorption cycles. UiO-66 and TETA/UiO-66 were synthesized by the solvothermal and impregnation methods for the study of CO 2 adsorption and separation of CO 2 /CH 4 by volumetric method. Adsorbents were characterized by X-ray diffraction (XRD), N 2 adsorption-desorption isotherm (BET analyzer), FT-IR spectroscopy, Thermogravimetric analysis (TGA), Scanning electron microscopy (SEM), and elemental analysis. All characterization results have confirmed that incorporated TETA was present and occupied pores of UiO-66. High adsorption of CO 2 was obtained for 25TETA/UiO-66 compared with UiO-66 by chemical interaction between CO 2 and adsorbent. Along with this, a decrease in CH 4 adsorption has been observed by a change in surface area and no interaction between them. The selectivity of CO 2 /CH 4 was higher for 25TETA/UiO-66 because of the large difference in adsorption capacities of CO 2 and CH 4. The heat of CO 2 adsorption for TETA incorporated UiO-66 was 54.6 KJ/mol at low coverage of CO 2 and CO 2 adsorption capacity was constant in multiple adsorption cycles. [ABSTRACT FROM AUTHOR]

The porous and highly stable filler material CTF-fluorene was incorporated with 8, 16 and 24 wt% into the polymer matrices polysulfone (PSF) and Matrimid®. The resulting mixed matrix membranes (MMMs) were investigated by binary mixture CO 2 /CH 4 mixed gas measurements. With increasing filler content in the MMMs, CO 2 and CH 4 permeabilities were enhanced with no loss of CO 2 /CH 4 selectivity. All membrane systems were compared to theoretical permeability models and the best agreement could be found applying the Maxwell model. Further, calculations of the fractional free volume (FFV) confirm the contribution of filler porosity to improve the membrane permeability. Image 1 • CTF-fluorene was synthesized via Friedel-Crafts -alkylation. • CTF was applied as filler material in PSF and Matrimid® mixed-matrix membranes. • CO 2 and CH 4 permeabilities were enhanced for both membrane systems. • Permeability (P) followed Maxwell and Bruggeman model with P d > P c. • Log P correlates linearly with reciprocal free fractional volume (1/FFV). [ABSTRACT FROM AUTHOR]

Mixed matrix membranes (MMM) incorporating metal-organic framework (MOF) fillers have gained increasing attention in addressing environmental and sustainability challenges. Hierarchical materials combining pore sizes of different length scales are expected to facilitate molecular diffusion and mass transfer for the optimization of catalysis and separation processes. Herein, a novel preparation method for hierarchical ZIF-8 (H-ZIF-8) particles is presented for the synthesis of polyimide (PI)-based MMMs with good compatibility between filler and polymer. Gas permeability measurements of polyimide-Matrimid®/H-ZIF-8 MMMs showed 4-fold improvements in permeability of both CO 2 and CH 4 coupled with a marked increase in selectivity and plasticization resistance for MMM with 30 wt% H-ZIF-8 loading. Gas transport analysis in these MMMs revealed that the enhanced gas separation performance of the MMMs can be related to the imidazolate modification of the PI structure and the hierarchical structure of H-ZIF-8, as confirmed by N 2 , Ar, mercury porosimetry, SEM, TEM analysis. CO 2 permeability for all MMMs increases with increasing CO 2 concentration and by decreasing temperature. The proof of concept, as demonstrated in this study, could be extended for the preparation of other hierarchical ZIFs and related MMMs. Image 1 • A novel synthesis method to prepare sub-micron size hierarchical ZIF-8 MOF. • Mixed matrix membranes (MMMs) fabricated with hierarchical ZIF-8 and polyimide. • MMMs showed improved thermal, mechanical and CO 2 plasticization properties. • H-ZIF-8 MMMs showed four times increase in permeability compared to polyimide. • Improved H-ZIF-8 MMMs selectivity is mainly governed by diffusion selectivity. [ABSTRACT FROM AUTHOR]

• A 6FDA-sulfonated trimethyl- m -phenylene diamine-derived polyimide was synthesized. • Hydrogen bonding and charge transfer complex formation resulted in tight polymer structure. • The sulfonic acid group boosted selectivity but lowered gas permeability. • Sulfonic acid functionalization did not mitigate CO 2 -induced plasticization. A sulfonic acid-functionalized trimethyl-substituted polyimide was synthesized by reacting 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 3,5-diamino-2,4,6-trimethylbenzenesulfonic acid (TrMSA). The properties of 6FDA-TrMSA were compared to the related 6FDA-derived polyimide analogues made from 2,4,6-trimethylbenzene-1,3-diamine (6FDA-TrMPD) and 3,5-diamino-2,4,6-trimethylbenzene benzoic acid (6FDA-TrMCA). Compared to 6FDA-TrMPD and 6FDA-TrMCA, sulfonic acid functionalization resulted in significantly lower surface area, reduced fractional free volume, and tighter chain d -spacing. Consequently, 6FDA-TrMSA displayed lower gas permeabilities with a commensurate increase in permeability-based gas-pair selectivities. The enhanced CO 2 /CH 4 selectivity of 6FDA-TrMSA was caused exclusively by higher diffusion selectivity, which was promoted by strong hydrogen bonding induced by the SO 3 H functionalization. Permeation experiments of 6FDA-TrMSA with a 1:1 CO 2 -CH 4 mixture revealed the occurrence of competitive sorption effects (depressing CO 2 gas permeability) and CO 2 -induced polymer matrix plasticization, which reduced the polymer selectivity by enhancing CH 4 permeability. At ~20 atm total pressure, 6FDA-TrMSA showed a CO 2 permeability of ~15 Barrer and an equimolar CO 2 /CH 4 mixed-gas selectivity of 55, which are ~2-fold higher performance values than those of the state-of-the-art polymer used for industrial scale natural gas sweetening, i.e., cellulose triacetate. [ABSTRACT FROM AUTHOR]

CO2 enhanced oil recovery (CO2-EOR) technology is a competitive strategy to improve oil field economic returns and reduce greenhouse gas emissions. However, the arbitrary emissions or combustion of the associated gas, which mainly consists of CO2 and CH4, will cause the aggravation of the greenhouse effect and a huge waste of resources. In this paper, the high-performance facilitated transport multilayer composite membrane for CO2/CH4 separation was prepared by individually adjusting the membrane structure of each layer. The effect of test conditions on the CO2/CH4 separation performance was systematically investigated. The membrane exhibits high CO2 permeance of 3.451 × 10−7 mol·m−2·s−1·Pa−1 and CO2/CH4 selectivity of 62 at 298 K and 0.15 MPa feed gas pressure. The cost analysis was investigated by simulating the two-stage system. When the recovery rate and purity of CH4 are 98%, the minimum specific cost of separating CO2/CH4 (45/55 vol%) can be reduced to 0.046 $·Nm−3 CH4. The excellent short-to-mid-term stability indicates the great potential of large industrial application in the CH4 recovery and CO2 reinjection from oilfield associated gas. [ABSTRACT FROM AUTHOR]

• Novel 6FDA-based co-polyimide MMM with high crystallinity microporous SSZ-16. • CO 2 /CH 4 binary feed with variation of CO 2 content and transmembrane pressure. • At the optimum loading, P CO2 was improved by ±100%, maintaining its high α CO2/CH4 of ~35. • At the highest loading, polymer rigidification and defective morphologies identified. The development, characterization, and CO 2 /CH 4 separation properties of a new mixed matrix membrane (MMM), comprises of 6FDA-DAM:DABA and small pore zeolite SSZ-16 were investigated. The MMMs were prepared with different zeolite loadings to study the filler content effects on the membrane physical and gas transport properties. Consequently, their gas separation performances were investigated at several transmembrane pressures (2, 4, 6 and 8 bar) using different binary feed gas compositions (25/75, 50/50, 75/25 vol.% of CO 2 /CH 4) at 25 °C. Besides improving the membrane physical properties, SSZ-16 addition is proven to enhance the gas separation performance effectively. The MMM with 5 wt.% SSZ-16 presents an excellent filler dispersion and increased CO 2 permeability by almost 2-fold while maintaining its high CO 2 /CH 4 selectivity, with respect to the unfilled membrane (P CO2 = 199.4 Barrer; α CO2/CH4 = 35.9). Higher filler loadings show slightly lower permeability, indicating a possible polymer rigidification in the filler-polymer region. Most importantly, MMM with the highest loading presents selectivity drop by ~50% due to defective polymer-filler interfaces, which directly increased the CH 4 permeability, concluding SSZ-16 addition is able to achieve the ideal MMM improvement only at low loadings. All the findings concerning different feed composition and transmembrane pressures are presented and discussed accordingly. [ABSTRACT FROM AUTHOR]

A combined experimental and molecular dynamics (MD) simulation approach was used to investigate the effects of the nanoconfinement of a highly CO 2 /CH 4 -selective ionic liquid (IL), 1-ethyl-3-methylimidazolium thiocyanate ([EMIM][SCN]), in porous poly(vinylidene fluoride) (PVDF) matrices on the gas separation performance of the resulting membranes. The observed experimental CO 2 /CH 4 permselectivity increased by about 46% when the nominal pore diameter in PVDF, which is a measure of nanoconfinement, decreased from 450 to 100 nm, thus demonstrating nanoconfinement improvements of gas separation. MD simulations corroborated these experimental observations and indicated a suppression in the sorption of CH 4 by [EMIM][SCN] when the IL nanoconfinement length decreased within the nonpolar PVDF surfaces. This is consistent with the experimental observation that the CH 4 permeance through the IL confined in nonpolar PVDF is significantly less than the CH 4 permeance through the IL confined in a water-wetting polar formulation of PVDF. The potential of mean force calculations further indicated that CO 2 has more affinity to the nonpolar PVDF surface than CH 4 . Also, a charge/density distribution analysis of the IL in the PVDF-confined region revealed a layering of the IL into [EMIM]- and [SCN]-rich regions, where CH 4 was preferentially distributed in the former and CO 2 in the latter. These molecular insights into the nanoconfinement-driven mechanisms in polymer/IL membranes provide a framework for a better molecular design of such membranes for critical gas separation and CO 2 capture applications.

Membrane technology is a simple and energy-conservative separation option that is considered to be a green alternative for CO2 capture processes. However, commercially available membranes still face challenges regarding water and chemical resistance. In this study, the effect of water and organic contaminants in the feed stream on the CO2/CH4 separation performance is evaluated as a function of the hydrophilic and permselective features of the top layer of the membrane. The membranes were a commercial hydrophobic membrane with a polydimethylsiloxane (PDMS) top layer (Sulzer Chemtech) and a hydrophilic flat composite membrane with a hydrophilic [emim][ac] ionic liquid–chitosan (IL–CS) thin layer on a commercial polyethersulfone (PES) support developed in our laboratory. Both membranes were immersed in NaOH 1M solutions and washed thoroughly before characterization. The CO2 permeance was similar for both NaOH-treated membranes in the whole range of feed concentration (up to 250 GPU). The presence of water vapor and organic impurities of the feed gas largely affects the gas permeance through the hydrophobic PDMS membrane, while the behavior of the hydrophilic IL–CS/PES membranes is scarcely affected. The effects of the interaction of the contaminants in the membrane selective layer are being further evaluated. [ABSTRACT FROM AUTHOR]

The goal of this study is to develop a cost-efficient carbon adsorbent for effective CO 2 capture and CO 2 /CH 4 separation. Using anthracite as the precursor, highly microporous nitrogen-doped (N-doped) carbons are fabricated through a combination of KOH activation and urea treatment. The as-prepared carbon samples possess developed microporosity and large nitrogen content. The sample synthesized under mild KOH/anthracite ratio (KOH/anthracite = 2), following with urea treatment shows a remarkable CO 2 uptake of 4.46 mmol g−1, among the highest achieved for N-doped porous carbons. This high CO 2 capture capability should be attributed to the synergistic effect of large amount of narrow micropores (pore with＜1 nm) and nitrogen doping in the carbon adsorbent. Experiment evidence suggests that nitrogen doping contributes much on CO 2 /CH 4 selectivity than that on CO 2 capture. According to ideal adsorption solution theory (IAST), assuming different binary mixture proportions of 50/50, 30/70 and 15/85, the sample possessing the largest nitrogen content (6.48 wt %) exhibits CO 2 /CH 4 IAST selectivities of 8.83, 7.02 and 8.09, respectively. Combining excellent CO 2 capture capacity and desirable CO 2 /CH 4 separation property, the microporous N-doped carbons prepared in this work appear to be a very promising candidate for greenhouse gas treatment and natural gas upgrading. Image 1 • Low-cost anthracite is used as precursor. • A simple pathway is used to prepare highly microporous N-doped carbons. • Synergistic effect of narrow micropores and nitrogen doping is adopted. • Effective CO 2 capture and CO 2 /CH 4 separation are achieved. [ABSTRACT FROM AUTHOR]

Amorphous and glassy polyhexafluoropropylene (PHFP) has been used for the first time as the matrix of mixed matrix membranes (MMMs). The preparation and the gas transport modeling of defect-free MMMs based on PHFP and 200 nm SAPO-34 crystals are described. By grafting SAPO-34 with perfluorinated tails the filler was well dispersed in the polymer and a good interfacial adhesion was guaranteed. The nano-particles determine a marked increase in gas permeability and a modest enhancement of the CO 2 /CH 4 permselectivity with respect to the neat polymer. Unexpectedly, the increase of permeability of the MMMs is not monotonous with the amount of SAPO-34. Following a recent approach, unrestricted gas diffusivity and solubility in SAPO-34 and PHFP are the inputs of the four-phase macroscopic modelling of gas transport through the MMMs. A four-phase approach to MMM modelling is dictated by the evidences of two distinct interfacial changes with respect to the ideal, nominal two phase MMM made of bulk-like SAPO-34 particles embedded in the pristine PHFP polymer matrix: a modified polymer phase of larger free volume (increasing permeability), which surrounds SAPO-34 particles, and barriers to the transport of gas (making the filler less permeable than PHFP), in the interior or on the surface of SAPO-34. The four-phase modelling, which delivers total gas transport features in excellent agreement with the experiments, is carried out by means of numerical optimization procedures based on a) Maxwell's effective medium analytical formulas, and b) a finite element solution of the transport differential equations. The latter approach reveals additional details, with respect to the first one, by delivering the different paths of gases through or around the SAPO-34 crystals in the MMMs. This work demonstrates the need to identify the real phenomena at work for a fruitful modelling of mass transport in MMMs, by overcoming the simplistic assumptions of MMMs obtained by the mere addition of the two original components. Image 1 • First polyhexafluoropropylene mixed matrix membranes have been prepared. • SAPO-34 improves both CO 2 permeability and CO 2 /CH 4 selectivity. • Larger polymer free volume and transport barriers at SAPO-34 coexist. • Both interfacial effects concur to the non-monotonous increase of permeability. • Analytical and numerical models of gas transport validate a 4-phase structure. [ABSTRACT FROM AUTHOR]

A well-shaped Ce (IV)-based metal organic framework (Ce-BDC) is prepared under solvothermal method. The influence of synthesis time, temperature and the amount of acetic acid (HAc) as a modulator is studied to develop a new strategy for the synthesis of well-shaped Ce-based MOF. The relationship between the synthesis parameters and morphology as well as crystallinity of Ce-BDC is investigated by XRD and SEM. Furthermore, the obtained well-shaped Ce-BDC shows a CO 2 uptake capacity of 2.28 mmol g−1 at 0 °C and 1.0 bar. Meanwhile, the breakthrough curve behaviors of Ce-BDC are investigated for a CO 2 /CH 4 and CO 2 /N 2 mixture gas. It is found that the Ce-based MOF adsorbs CO 2 under ambient temperature and pressure, but completely excludes CH 4 and N 2 , suggesting that it is a promising adsorbent for efficient separation of CO 2 from natural gas. Image 1 • Well-octahedral Ce-BDC MOF is prepared by solvothermal method. • The influence of different synthesis parameters are investigated for the synthesis of well-shaped MOF. • The prepared Ce-BDC exhibits high CO 2 /CH 4 and CO 2 /N 2 adsorption selectivity. [ABSTRACT FROM AUTHOR]

• Facilitated transport membranes were fabricated by incorporating 2D CONs into Pebax Matrix. • TpDT CONs were obtain through a self-exfoliation manner during the synthetic process. • The amino groups and porous structures facilitated the transportation of CO 2 molecules. • The as-prepared membranes showed elevated permeance and selectivity simultaneously. Two-dimensional (2D) covalent organic nanosheets (CONs) present versatile 2D materials, which hold great promise in mixed matrix membranes. The facile synthesis of CONs for the fabrication of mixed matrix membranes represents the development trend. Herein, mixed matrix membranes with facilitated transport ability were prepared based on self-exfoliated covalent organic nanosheets (CONs) and poly(ether-block-amide) (Pebax® MH 1657) matrix. The self-exfoliated TpDT CONs were facilely synthesized via Schiff base condensation reaction between 1,3,5-Triformylphloroglucinol (Tp) and 3, 5-diamino-1,2,4-triazole (DT). Abundant amine groups on TpDT CONs skeleton served as facilitated transport carriers to promote the transport of CO 2 by reversible nucleophilic addition reactions. And the highly ordered channels of TpDT CONs allowed the rapid transportation of CO 2 molecules to reach the facilitated transport carriers. Moreover, the incorporated TpDT CONs disturbed the packing of the Pebax chains by the intervention effects and increased the chain mobility. The facilitated transport carriers from TpDT CONs and the optimized structure endowed the as-prepared membranes with elevated permeance and selectivity. Specially, the Pebax-TpDT/PVDF membranes with 1 wt% TpDT CONs achieved an optimum CO 2 /CH 4 separation performance with a separation factor of 36.0 and a CO 2 permeance of 142.3 GPU, which were increased by 68% and 131%, respectively, compared with the pristine Pebax membrane. [ABSTRACT FROM AUTHOR]

Polysulfone-based mixed matrix membranes (MMMs) embodying metal-organic framework ZIF-11 with extremely narrow pore-openings (~3.0 Å of aperture windows) as the nano-fillers were fabricated and applied in CO 2 /CH 4 separation for natural gas upgrading. The proper dispersion of ZIF-11 nano-fillers, below a threshold loading, led to defect-free free-standing membranes. The CO 2 /CH 4 separation factor and CO 2 permeability of MMMs with filler loading of 24 wt% showed a 43.5% and 99.5% of increment compared with the pure polysulfone (PSF) membrane, respectively. Adsorption/diffusion coefficients and the corresponding selectivities of gases for ZIF-11/PSF MMMs were quantitatively determined. Importantly, the diffusion coefficient of CO 2 of MMMs with 24 wt% of ZIF-11 nanoparticles increased by 48.8% compared with that of the pure polymer membrane, but the diffusion coefficient of CH 4 decreased by 42.7%. Accordingly, the CO 2 /CH 4 diffusion selectivity increased by 160%, indicating that the restricted aperture windows of ZIF-11 permit CO 2 to pass through but imped CH 4. A clear molecular sieving process was realized in MMMs with ZIF-11 nano-fillers. Image 1 • ZIF-11 with extremely narrow pores are used as nano-fillers of mixed matrix membranes. • A notably improved CO 2 /CH 4 separation performance emerged at 24 wt% of ZIF-11 loading. • ZIF-11 nano-fillers promoted CO 2 diffusion but impeded CH 4 diffusion. The optimum CO 2 /CH 4 diffusion selectivity of membranes increased by 160%. • The optimum CO 2 /CH 4 diffusion selectivity of membranes increased by 160%. [ABSTRACT FROM AUTHOR]

CO 2 -selective AlPO-18 membranes were prepared hydrothermally on macroporous supports with a low-cost template N, N -diisopropylethylamine (DIPEA). The effects of synthesis parameters (such as gel dilution, synthesis temperature, synthesis time and aging time) on the structure, morphology and single gas permeation properties of CO 2 and CH 4 through AlPO-18 membranes were investigated in detail. The synthesis conditions had little effect on the membrane morphology but strongly affected the CO 2 /CH 4 gas permeation properties of as-synthesized AlPO-18 membranes. The best membrane was obtained at a synthesis temperature of 433 K for 15 h after aging the precursor gel (1Al 2 O 3 : 1P 2 O 5 : 4DIPEA: 120H 2 O: 4IPA) for 24 h. The CO 2 single gas permeance of this membrane was 1.1 × 10−6 mol/(m2 s Pa), with an ideal CO 2 /CH 4 selectivity of 56 at 303 K and a 0.1 MPa pressure drop. The mixed gas CO 2 permeance of same membrane with an equimolar CO 2 /CH 4 mixture was 1.1 × 10−6 mol/(m2 s Pa) with a CO 2 /CH 4 selectivity of 75 at 303 K and a 0.2 MPa pressure drop. Image 1 • Effects of synthesis parameters on growth and separation performances of AlPO-18 membranes were discussed. • Synthesis temperature and synthesis time were reduced for the preparation of AlPO-18 membranes. • CO 2 -selective AlPO-18 membranes were prepared on macroporous mullite support with single DIPEA as a template. • AlPO-18 membrane showed high CO 2 /CH 4 separation performance with a CO 2 permeance of 1.1 × 10−6 mol/(m2 s Pa). [ABSTRACT FROM AUTHOR]

• 3-stage membrane pilot plant was designed and constructed for 100 Nm3/h biogas. • Polysulfone hollow fiber membrane modules were developed for CH 4 /CO 2 separation. • Separation behaviors of CH 4 /CO 2 were investigated by changing process parameters. • Optimized process produced high purity CH 4 and CO 2 at high recovery, respectively. In this work, we report on the design, construction and optimization of a pilot scale 3-stage membrane plant operated by a single compressor for production of high-purity CH 4 and CO 2 from crude biogas. In our previous works, we developed asymmetric polysulfone hollow fiber membranes with high CO 2 /CH 4 separation properties and a numerical simulation program for a 3-stage membrane process for biogas separation. Herein, utilizing a pure gas permeation test, we report the effects of feed pressure and temperature on gas separation properties of the developed membrane modules. We also report the effects of various operating conditions on CH 4 purity and recovery at the retentate, which were investigated using mixed gases as a function of stage-cut. Using a simulation program and the gas permeation data, we designed and constructed a 3-stage membrane plant that can treat 100 Nm3/h of crude biogas (65–75 vol% CH 4 , balanced CO 2). It was confirmed that, in the constructed 3-stage pilot plant, the final purity and recovery ratios for CH 4 and CO 2 of the 3-stage membrane plant were significantly influenced by the operation conditions. Under optimized operation conditions, the 3-stage membrane plant exhibited outstanding biogas separation performance; high CH 4 purity and good recovery (98.4% and 98.7%, respectively) were observed, together with high CO 2 purity and recovery (97.2% and 97.0%, respectively). This study demonstrates the commercial applicability of the 3-stage membrane pilot plant using polysulfone hollow fiber membranes for simultaneous production of high purity CH 4 and CO 2 from crude biogas. [ABSTRACT FROM AUTHOR]

The aim of current work is to study the interaction of process parameters including, temperature, CO 2 feed composition and feed pressure were towards CO 2 separation from CO 2 /CH 4 binary gas mixture over hollow fiber mixed matrix membrane using design of experiment (DoE) approach. The hollow fiber mixed matrix membrane (HFMMM) containing NH 2 -MIL-53(Al) filler and cellulose acetate polymer was successfully spun and fibers with outer diameter of approximately 250–290 nm were obtained. The separation results revealed that the increment of temperature from 30 °C to 50 °C reduced the CO 2 /CH 4 separation factor while, increasing feed pressure from 3 bar to 15 and increment of CO 2 feed composition from 15 to 42.5 vol% increased the separation factor of HFMMM. The DoE results showed that the feed pressure was the most significant process parameter that intensely affected the CH 4 permeance, CO 2 permeance and CO 2 /CH 4 separation factor. Based on the experimental results obtained, maximum CO 2 permeance of 3.82 GPU was achieved at feed pressure of 3 bar, temperature of 50 °C and CO 2 feed composition of 70 vol%. Meanwhile, minimum CH 4 permeance of 0.01 GPU was obtained at feed pressure of 15 bar and temperature of 30 °C and CO 2 feed composition of 70 vol%. Besides, maximum CO 2 /CH 4 separation factor of 14.4 was achieved at feed pressure of 15 bar and temperature of 30 °C and CO 2 feed composition of 15 vol%. Overall, the study on the interaction between separation processes parameters using central composite design (CCD) coupled with response surface methodology (RSM) possesses significant importance prior to the application of NH 2 -MIL-53(Al)/Cellulose Acetate HFMMM at industrial scale of natural gas purification. Image 1 • Interaction of process parameters on CO 2 /CH 4 binary gas separation performance over cellulose acetate based HFMMM. • CCD-RSM method is used to investigate the interaction of separation process parameters over the HFMMM. • Increment in feed pressure increased CO 2 /CH 4 separation factor from 4.2 to 14.4. • Maximum CO 2 /CH 4 separation factor of 14.4 was achieved. [ABSTRACT FROM AUTHOR]

Three new lanthanide metal-organic frameworks IRHs-( 1-3 ) supported by cyamelurate linkers have been synthesized and structurally characterized. The incorporation of numerous heteroatoms (N and O) into the pore walls and the relatively small microchannels of these porous solids enhance bonding force of the host-guest interactions, thus promoting the adsorption of carbon dioxide (CO 2 ) over methane (CH 4 ). The nonpolar covalent bonds in methane also favor the less uptake due to the hydrophilic walls of these frameworks. Grand canonical Monte Carlo simulations were performed to determine the origin of the adsorption. The density isocontour surfaces show that CO 2 is mainly adsorbed on the walls composed of organic linkers and around the metal sites, whereas no specific adsorption site is observed for CH 4 , which indicates weak interactions between the framework and the adsorbed gas. As expected, the simulations show that CH 4 is not observed around the metal center due to the presence of H 2 O molecules. The excellent selectivity of CO 2 /CH 4 binary mixture was predicted by the ideal adsorbed solution theory (IAST) via correlating pure component adsorption isotherms with the Toth model. At 25 °C and 1 bar, the CO 2 and CH 4 uptakes for IRH -3 were 2.7 and 0.07 mol/kg, respectively, and the IAST predicated selectivity for CO 2 /CH 4 (1:1) reached 27, which is among the best value for MOF materials.

In this study, polymeric nanocomposite gas separation membranes were fabricated by incorporating different contents of aluminum oxide (Al 2 O 3) (0, 2, 4, 6 and 8 wt %) into the matrix of poly (ether-block-amide) (Pebax). The resultant membranes properties were characterized by using FTIR, FESEM, XRD, and TGA. Permeation rates of pure CO 2 and CH 4 gases through the fabricated pristine and the nanoparticles-incorporated membranes were measured at different pressures (3, 6, 9, 12 and 15 bar) and a fixed temperature of 25 °C. The results revealed better separation efficiency (CO 2 permeability and CO 2 /CH 4 selectivity) of the nanocomposite membranes than the pristine membrane. For example, the CO 2 permeability and ideal CO 2 /CH 4 selectivity values for the neat membrane at the pressure of 3 bar were 123.46 Barrer and 21.21, respectively while those values for the membrane comprising 8 wt % of Al 2 O 3 were 159.27 Barrer and 24.73. • Al 2 O 3 was embedded into Pebax-1657 matrix to fabricate nanocomposite membranes. • Permeabilities of CO 2 and CH 4 through the fabricated membranes were studied. • The membranes were characterized via XRD, FTIR, FESEM, TGA analyses. • Addition of the Al 2 O 3 into Pebax-1657 matrix improved the membranes performance. [ABSTRACT FROM AUTHOR]

The CO 2 /C2-hydrocarbons over CH 4 separation processes are important for the purification of methane fuel. Towards to this purpose, we have designed two isostructural indium-terephthalate metal-organic frameworks (MOFs) decorated with inorganic OH− anions and/or organic –OH Lewis basic groups, namely SNNU-120 and -121. One-dimensional (1D) [In(OH)(COO) 2 ] chains act as rod-shaped secondary building units (SBUs) linking adjacent four SBUs to form robust 3D rod-packing architecture with two types of 1D channels. Under 273 and 298 K, SNNU-120 and -121 have remarkable CO 2 , C 2 H 2 and C 2 H 4 uptakes but negligible CH 4 adsorption. IAST calculations indicate both of them can effectively separate CO 2 /C2-hydrocarbons from CH 4. The gas adsorption and separation performance of inorganic OH− and organic –OH group co-functionalized SNNU-121 MOF are superior to SNNU-120 only with inorganic OH− anions. Specially, the excellent IAST CO 2 /CH 4 (214.4) and C 2 H 4 /CH 4 (200) selectivity values for SNNU-121 are considered top-level among all rod-packing MOFs and also surpass the values of most famous MOF materials up to now. Two robust rod-packing In–OH-BDC metal-organic frameworks decorating with inorganic OH- anions and/or organic –OH Lewis basic groups show top-level CO 2 /C2-hydrocarbons over CH 4 seperation performance. Image 1 • Robust rod-packing indium-carboxylate frameworks. • Co-existence of ultramicroporous and microporous channels. • Top-level CO 2 /CH 4 and C 2 H 4 /CH 4 separation performance. [ABSTRACT FROM AUTHOR]

The bottleneck of conventional polymeric membranes applied in industry has a tradeoff between permeability and selectivity that deters its widespread expansion. This can be circumvented through a hybrid membrane that utilizes the advantages of inorganic and polymer materials to improve the gas separation performance. The approach can be further enhanced through the incorporation of amine-impregnated fillers that has the potential to minimize defects while simultaneously enhancing gas affinity. An innovative combination between impregnated Linde T with different numbers of amine-functional groups (i.e., monoamine, diamine, and triamine) and 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA)-derived polyimide has been elucidated to explore its potential in CO2/CH4 separation. Detailed physical properties (i.e., free volume and glass transition temperature) and gas transport behavior (i.e., solubility, permeability, and diffusivity) of the fabricated membranes have been examined to unveil the effect of different numbers of amine-functional groups in Linde T fillers. It was found that a hybrid membrane impregnated with Linde T using a diamine functional group demonstrated the highest improvement compared to a pristine polyimide with 3.75- and 1.75-fold enhancements in CO2/CH4 selectivities and CO2 permeability, respectively, which successfully lies on the 2008 Robeson's upper bound. The novel coupling of diamine-impregnated Linde T and 6FDA-derived polyimide is a promising candidate for application in large-scale CO2 removal processes. [ABSTRACT FROM AUTHOR]