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, CH4, N-2, and CO2 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/CH4 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.