Study On Amine-rich Nanostructure Transport Channels Enhanced CO₂separation Performance Of Polyvinylamine Mixed Matrix Composite Membranes

Mixed matrix composite membranes（MMCMs）are expected to break the limitation of the"trade-off"effet and develope a new low-energy and high-efficiency direction for achiving“carbon emission peak and neutrality”.However,the gas separation performeance was restrated by the non-miscibility of two-phase between inorganic filler and polymer matrix,the agglomeration of inorganic filler in the membranes and the gas transfer rate inhibited by tortuous gas transfer pathways.Moreover,the fillers are difficult to accelerate the gas transfer rate extensively,since the micropore is pursued to discriminate gas molecule with small kinetic diameter difference.Hence,in this study,the nanofillers were hydrophilically modified and the channel environment of the nanofillers was regulated to improve the two-phase interfacial compatibility and accelerate the CO₂transport in the membrane.The specific studies are as follows:（1）ZIF-8@NENP-NH₂ nanoparticle was fabricated by growing amine functionalization nitrogen-enriched nanoporous polytriazine（NENP-NH₂）on the surface of ZIF-8.Followed by,the PVAm/ZIF-8@NENP-NH₂MMCMs were obtained through coating a mixed dispersion of ZIF-8@NENP-NH₂nanoparticles and polyvinylamine（PVAm）on a porous polysulfone（PSf）membrane.The successful preparation of core-shell ZIF-8@NENP-NH₂was demonstrated by SEM,FTIR,XRD and N₂adsorption.It was observed that ZIF-8@NENP-NH₂nanoparticles were uniformly distributed in the PVAm matrix by SEM characterization.ATR-FTIR and DSC characterization confirmed the hydrogen bonding interactions between ZIF-8@NENP-NH₂and PVAm.After that,the effects of fillers preparation conditions,loading,and operating conditions on the gas separation performance of MMCMs were systematically investigated.The gas separation performance evaluation showd that,the highest CO₂permeance of 301 GPU accompanied with a CO₂/N₂selectivity of 91 was obtained for MMCMs loaded with 7 wt%ZIF-8@NENP-NH₂,which were enhanced by 296.1%and 89.6%,respectively,when compared with PVAm membrane.The possible reasons for the enhanced gas separation performance is the continuous CO₂facilitated transport-molecular sieving nanochannels were constructed by the core-shell structure ZIF-8@NENP-NH₂to accelerate CO₂transport in the membranes.（2）A polyethyleneimine-grafted porous aromatic framework（PEI-g-PAF）was prepared via a self-assembly strategy between PEI and organic linkers.After that,a mixed dispersion of PEI-g-PAF and PVAm aqueous solution was casted onto the surface of modified PSf to fabricate PVAm/PEI-g-PAF MMCMs.The successful preparation of PEI-g-PAF nanofillers was confirmed using FTIR,XRD showed the PEI-g-PAF with an amorphous structure.The hydrogen bonding between PEI-g-PAF nanoparticles and PVAm was demonstrated by ATR-FTIR,TGA characterization showed PEI-g-PAF nanoparticles and MMCMs have good thermal stability,which could meet the industrial production requirements.After that,the effects of fillers preparation conditions,nanoparticle loading,and operating conditions on the gas separation performance of MMCMs were systematically investigated.The gas separation performance testing of PVAm/PEI-g-PAF showed a CO₂permeance of 884 GPU,a CO₂/N₂selectivity of 79 and the separation performance did not significantly decrease during 360 h stability testing.The enhanced gas separation performance may due to the amine-rich microenvironment nanochannels constructed by PEI-g-PAF,which could preferential adsorb CO₂and facilitate CO₂ transport in the MMCMs.