Affinity between Metal–Organic Frameworks and Polyimides in Asymmetric Mixed Matrix Membranes for Gas Separations

A series of flat-sheet asymmetric mixed matrix membranes (MMMs) have been fabricated with MOF-5, Cu 3 (BTC) 2, and MIL-53(Al) as fillers and PI polymer as a matrix through the dry–wet phase inversion method. After the surface modification by coating a PAA solution (15% wt) on the top of the obtained membrane, a thin defect-free selective skin in the MMM is obtained. The permeance of various gases such as H 2, He, CH 4, N 2, and CO 2 and their gas pair selectivity have been investigated, respectively. The results show that Cu 3 (BTC) 2 /PI MMM possesses the best gas separation performance with H 2 permeance of 0.44 GPU and H 2 /CH 4 selectivity of 100. In addition, the mechanism of MOF fillers in MMMs has been further revealed by the interaction analysis between MOF fillers and PI chains.