Investigation of ZIF‐8, amine‐modified ZIF‐8 and polysulfone based mixed matrix membranes for CO2/CH4 separation

Abstract

AbstractMembrane separation is one of the techniques used for biogas upgradation. Mixed matrix membranes (MMMs) are currently being explored to overcome the trade‐off of selectivity‐permeability inherent in polymer membranes used for gas separation. A significant challenge associated with MMMs is the poor polymer‐metal–organic framework (MOF) filler interfacial compatibility, reducing the selectivity or permeability of gas. To address this issue, the present study focuses on the effect of the amine functionalization of ZIF‐8 to enhance the CO2 gas permeation without reducing the CO2/CH4 selectivity. MMMs were fabricated using unmodified ZIF‐8 and amine‐modified ZIF‐8 nanofillers dispersed in polysulfone at 5, 10, and 15 wt% loadings. MMMs were characterized by FTIR, DSC, TGA, and FESEM. X‐ray diffraction and FTIR analysis was conducted to verify the amine modification of ZIF‐8. Further, the performance of MMMs was tested with pure gasses (CO2 and CH4) and a model mixture of CO2 and CH4. In the mixed gas permeation test, the 10 wt% ZIF‐8 MMM exhibited the highest CO2 permeability of 25.4 Barrers, while 15 wt% NH2‐ZIF‐8 MMM exhibited the highest selectivity of 13.5. Notably, the ZIF‐8 MMMs demonstrated a 148% increase in CO2/CH4 selectivity, whereas the NH2‐ZIF‐8 MMMs exhibited a 155% increase compared to the pure polysulfone membrane.