Tannic Acid‐Fe( III ) Modified UIO ‐66( NH 2 ) Incorporated Polyimide‐Based Mixed Matrix Membranes for Enhanced Gas Separation

ABSTRACT Mixed matrix membranes (MMMs) incorporating metal–organic frameworks (MOFs) as fillers show attractive selectivity and permeability for gas separation. However, the performance improvement is restricted by undesirable interfacial interaction and inhomogeneous dispersion of MOFs in the membrane matrix. In this paper, amino‐functionalized UIO‐66 (U6N) with high porosity was employed as a filler and further regulated by a controlled plant polyphenol‐induced surface modification strategy. The process involved the formation of tannic acid‐iron(III) complex (TA‐Fe(III)) on the U6N surface, which improved interfacial compatibility with the polyimide matrix while introducing abundant hydroxyl groups to enhance gas transport properties. Accordingly, the modified MMMs containing 30 wt.% U6N@TA‐Fe(III) achieved optimized gas separation performance. Specifically, the CO 2 permeability increased to about 2495.9 Barrer with a CO 2 /CH 4 selectivity of 19.32, which exceeded the 2008 Robeson upper limit and showed an increase of 22.1% and 25.6%, respectively, compared to the MMMs embedded with unmodified U6N. Moreover, the improved dispersion of the U6N@TA‐Fe(III) within the membrane structure is conducive to improving separation performance for CO 2 /N 2 and O 2 /N 2 . Therefore, this work provides a novel insight into the rational design of the MMMs via a facile modification strategy, which can further improve the gas separation performance of the MMMs.