MOF gel network templated polyimide mixed-matrix membranes for high-efficiency CO2/CH4 separation

Efficient separation of CO 2 from CH 4 is a critical unit operation for biogas upgrading and achieving carbon neutrality goals. While mixed-matrix membranes (MMMs) offer an energy-efficient alternative to traditional separation processes, their industrial deployment is often restricted by engineering challenges, specifically filler agglomeration and non-selective interfacial defects. Herein, we report a novel MOF (metal–organic framework) gel network templated polymerization strategy that effectively circumvents these limitations. In this approach, a continuous, pre-formed network of UiO-66 MOF gel serves as a structural scaffold, within which the 6FDA-ODA polyimide matrix is directly polymerized. This method fosters exceptional interfacial adhesion and uniform dispersion of the filler, successfully eliminating non-selective defects. The resulting MMMs exhibit remarkable gas separation performance, with the optimal membrane (MA-0.075, with 1.6 wt% UiO-66 gel loading) achieving a CO 2 permeability of 30.9 Barrer and a CO 2 /CH 4 selectivity of 135.5 under mixed-gas conditions. This represents enhancements of 212 % and 162 %, respectively, over the pristine 6FDA-ODA polyimide membrane, surpassing the 2008 Robeson upper bound. Furthermore, the membrane demonstrated excellent operational stability over 120 h. This work provides a scalable fabrication route for advanced MMMs, demonstrating significant potential for energy-efficient gas separation applications.