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[Display omitted] • CO 2 was preferentially adsorbed due to the aldehyde group in the imidazolide skeleton of ZIF-93 zeolite. • CO 2 permeability and CO 2 /N 2 selectivity were improved with NH 2 -ZIF-93 addition. • Gas storage space is formed to improve gas separation efficiency of Pebax MMMs. In this study, amino organic compounds were grafted on the porous ZIF-93 surface by grafting modification to create a villous organic layer with CO 2 adsorption. Pebax-1657-based mixed matrix membrane (MMMs) is created using modified ZIF-93 as filler. The presence of this organic layer not only improves the adsorption of CO 2 gas by the filler, but also improves the rich storage space for the gas transport in the MMMs. Thus, the permeability and CO 2 /N 2 selectivity are improved. The MMMs with 10 wt% NH 2 -ZIF-93 showed the best separation performance, exhibiting distinct increases of 87.32% and 96.32% compared to primitive Pebax-1657 membrane, and passed Robeson's upper bound. [ABSTRACT FROM AUTHOR]

[Display omitted] • PSA modified hollow NH 2 -ZIF-8 (PHNZ) with high amino content was designed. • PSA hard template strategy was used to synthesis NH 2 -ZIF-8 rapidly. • The vesicle shape of PHNZ constructs low-resistance region to improve CO 2 permeability. • CO 2 /N 2 selectivity is improved by PSA layer and CO 2 affinity of amino groups. The amino functionalization of MOFs has been verified to be effective in improving the selective permeation of CO 2. However, the introduction of amino groups into ZIF-8 by mixed ligands strategy is hard to achieve due to the high steric hindrance of benzene ring in 2-aminobenzimidazole ligand, resulting in insufficient content of amino groups. Therefore, in this work, polystyrene-acrylate (PSA) template is proposed to provide abundant adsorption and reaction sites for the rapid synthesis of NH 2 -ZIF-8 with high content of 2-aminobenzimidazole. Furthermore, the incomplete etching strategy is used to construct PSA modified hollow NH 2 -ZIF-8 nanospheres (PHNZ). Importantly, the thickness of PSA layer and the hollow size are adjusted by the etching time, as revealed by the SEM and TEM images. In this PHNZ, the modified PSA can provide good interface compatibility between PHNZ and Pebax matrix to enhance the CO 2 selectivity, while the hollow structure can reduce the mass transfer resistance and improve the gas permeability. Moreover, the introduced amino groups can enhance the CO 2 affinity of PHNZ and further improve the CO 2 /N 2 selectivity of the PHNZ-based mixed matrix membranes (MMMs). Benefiting from the synergy of good interface compatibility and enhanced CO 2 affinity from the amino groups, the PHNZ/Pebax MMMs present greatly improved CO 2 /N 2 selectivity in contrast with pure Pebax and NH 2 -ZIF-8 based membranes. Besides, as the etching time increases, the PHNZ-2 and PHNZ-3 based MMMs present a higher CO 2 permeability than that of NH 2 -ZIF-8 based MMM, revealing the significance of the hollow structure. The PHNZ-2/Pebax MMM with filler loading of 10 wt% expresses the best gas separation performance with the CO 2 permeability of 121.9 Barrer and CO 2 /N 2 selectivity of 96.6, respectively, showing an increase of 54.7 % and 98.0 % in contrast with pure Pebax membrane. Meanwhile, this CO 2 separation performance is far beyond the Robeson upper bound in 2008 and close to the McKeown upper bound in 2019, demonstrating that the proposed PHNZ displays a promising and competitive potential in MMM based CO 2 capture. [ABSTRACT FROM AUTHOR]

[Display omitted] • PEI was introduced into ZIF-8 HNTs to obtain versatile filler for MMM. • The –NH 2 groups in PEI can facilitate CO 2 transport in presence of H 2 O. • Residence of PEI into nanocages of ZIF-8 can adjust its effective sieving size. • Hydrogen bond between PEI and Pebax can strengthen interfacial compatibility. • 1D hollow nanotube provides fast transport channel with low resistance. 1D nanotube (HNT) based MMM presents high CO 2 permeation due to its long and hollow structure. However, the improvement of selectivity is still challenging. In this study, small PEI molecules with abundant amino groups were introduced into the nanocages of ZIF-8 HNTs to construct facilitated CO 2 transmission channel with low resistance. In the PEI@ZIF-8 HNTs, the –NH 2 groups can facilitate CO 2 transport in presence of H 2 O, resulting in an improvement in both CO 2 permeability and selectivity. Second, the introduction of PEI into the nanocages of ZIF-8 can adjust the effective sieving size to enhance CO 2 selectivity. Third, the hydrogen bond between PEI and Pebax can strengthen the interfacial compatibility, further improving CO 2 /N 2 selectivity of the MMMs. Finally, the 1D hollow structure of PEI@ZIF-8 HNTs provides CO 2 molecules with low-resistance and fast transport channel, enhancing the CO 2 permeability. Consequently, both the high CO 2 permeability and the high CO 2 /N 2 selectivity are acquired by the versatile filler of PEI@ZIF-8 HNTs. PEI@ZIF-8 HNTs based MMM at filler loading of 7 wt% under dry mixed gas, presents CO 2 permeability of 177 Barrer and CO 2 /N 2 selectivity of 72, which are 40% and 10.8% higher than those of ZIF-8 HNTs based MMM, respectively. Moreover, the permeability of CO 2 and the selectivity of CO 2 /N 2 reach 306 Barrer and 79 respectively under the wet mixed gas, which is far beyond the Robeson upper bound in 2008 and exceeds the McKeown upper bound in 2019. The proposed PEI@ZIF-8 HNTs are believed to be promising filler for MMMs based CO 2 capture. [ABSTRACT FROM AUTHOR]

[Display omitted] • Highly permeable PTMSP fibers provide continuous and fast transport pathway. • EFCM was obtained by in-situ polymerization of PEG within fibers voids. • PTMSP fibers skeleton reinforces the membrane mechanical properties. • Both high CO 2 permeability and selectivity were acquired. • High CO 2 selectivity was mainly due to the high affinity between PEO and CO 2. Electrospun fibers composite membrane shows an insufficient CO 2 permeability due to the impermeable polymer fibers. In this work, highly permeable poly(1-trimethylsilyl-1-propyne) (PTMSP) electrospun fiber were utilized to construct continuous and fast transport pathway with low-resistance for gas molecules in PEO matrix. The PEO/PTMSP electrospun fiber composite membrane (EFCM) was obtained by the in-situ polymerization of polyethylene glycol (PEG) into the voids of PTMSP electrospun fibers, which is demonstrated by FTIR and XPS characterizations. Furthermore, the obtained EFCM is dense and defect-free, which is confirmed by SEM images. Specifically, the PTMSP fibers and PEO matrix present good interfacial compatibility, as revealed by DSC results. In addition, PTMSP electrospun fibers perform as skeleton for EFCM to reinforce the membrane mechanical properties. The PEO/PTMSP EFCM shows CO 2 permeability of 281 Barrer and CO 2 /N 2 selectivity of 32.94. The CO 2 permeability is 280% higher than that of pure PEO membrane, which is resulted from the continuous and fast transport pathway provided by PTMSP electrospun fibers. The CO 2 /N 2 selectivity is enhanced by 4 to 6 times in comparison with pure PTMSP membrane and PTMSP c-EFM, which can be attributed to the affinity between EO groups of PEO matrix and CO 2 molecules and also the screening effect from the tortuous pathway of PTMSP fibers. This superior gas separation performance of PEO/PTMSP EFCM exceeds most reported PTMSP based membranes, especially its selectivity of CO 2 over N 2 is significantly high. Consequently, this proposed EFCM with continuous and fast transport pathway holds a competitive prospect for polymer based CO 2 capture. [ABSTRACT FROM AUTHOR]

[Display omitted] • MMMs based on Pebax-1657 and microporous CNs were successfully prepared. • CO 2 permeability and CO 2 /N 2 selectivity were improved with CNs addition. • Microporous CNs with accessible inner channels provided low-resistance transport channels for CO 2. • The CNs-600(0.5 wt%)/Pebax MMMs showed the best CO 2 permeability and selectivity. We investigated the use of microporous carbon nanospheres (CNs) as fillers to prepare mixed matrix membranes (MMMs) for permeable and selective CO 2 separation. CNs with a uniform size of 650 nm and unique amorphous structure were characterized by SEM and XRD. The N content of CNs with different carbonization temperatures was determined by XPS. The surface area and micropore size of the samples could be easily adjusted by varying the carbonization temperature; in particular, increasing the carbonization temperature improved both parameters. At 600 °C, the particles (CNs-600) exhibited a higher N content and narrower micropores, which ensured higher affinity and enhanced capture of CO 2 molecules. Thus, CNs-600/Pebax MMMs exhibited superior CO 2 separation performances compared to other CNs-based MMMs. Furthermore, when the loading of CNs-600 was 0.5 wt%, the MMMs exhibited the best CO 2 /N 2 separation properties, with a 39.51% improvement compared to pristine Pebax membranes. These outstanding performances are attributed to the fact that microporous CNs with accessible inner channels can provide a low-resistance transport pathway to gas molecules. Moreover, the strong interaction between CO 2 and the pore walls, along with the high N content, enabled an effective separation of CO 2 from other gas molecules. Importantly, the CNs-600/Pebax MMMs displayed superior CO 2 /N 2 selectivity compared to previously reported Pebax-based MMMs with other fillers. The proposed CNs, with microporous structure and high N content, may represent a promising alternative for the fillers of MMMs. [ABSTRACT FROM AUTHOR]