An imidazole ionic liquid(IL)is selected to modify ZnBDC,a metal organic framework filler,to prepare IL@ZnBDC nanocomposite filler that is added into polyimide(PI)through physical blending route to prepare PI-IL@ZnBDC mixed matrix membrane.It is found that the addition of nanocomposite filler improves the compatibility between filler and PI,and increases the molecular chain spacing of the mixed matrix membrane,therefore enhancing the CO2 diffusion process in the membrane.Meanwhile,the trifluoromethyl group,sulfonic acid group and imidazole group contained in the IL have strong affinity with CO2,which promotes the dissolution of CO2 in the membrane,further synergistically enhances the dissolution-diffusion mechanism of PI-IL@ZnBDC mixed matrix membrane,and simultaneously improves the CO2 permeability and the selectivity of CO2/CH4.Compared with pure PI membrane,PI-IL@ZnBDC-2 membrane shows excellent gas separation performance,with a CO2 permeability of 10.97 Barrer,and a CO2/CH4 selectivity of 42.21,which are 59.9％and 41.5％respectively higher than those by pure membrane.
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