“…The PI-COOH/UiO-66/Cu 2+ TFN membranes have a high CO 2 /CH 4 selectivity (29–35) as well as high CO 2 permeance (109–350 GPU). In comparison to some polymer-based and novel material-based membranes (such as Matrimid 5218, cellulose acetate, 6FDA-BAPAF, SILMS, and SAPO), PI-COOH/UiO-66/Cu 2+ membranes show both higher CO 2 /CH 4 selectivity and higher CO 2 permeance. − Although the Kapton, PU/PVAc (80/20), and MOF-based membranes such as ZIF-8, UiO-66, and MIL-101(Zr) exhibit high CO 2 /CH 4 selectivity, their low CO 2 permeance (<10 GPU) reduces their overall separation performance. ,, The comprehensive separation performance of the PI-COOH/UiO-66/Cu 2+ TFN membranes is better than that of the most TFN membranes reported in the literature, including PA/CDC, Matrimid/Cu 3 (BTC) 2 , PIM-1/GO, Pebax 1657/C 60 (OH) 24 , and PDMS/zeolite 4 Å. ,− …”