A Composite MembraneEnabled by MOF Porous Liquidfor Synergistic Enhancement of CO/H Selectivityand Permeance

Membranes that can overcome the permeance-selectivity trade-off are highly desirable for gas separations. Composite membranes have attracted increasing attention by integrating the excellent properties of various single-layer materials. In this work, we report a series of composite membranes with an MOF-based porous liquid (PL) layer, a PIM-1-polyurethane (PU) layer, and a polyacrylonitrile (PAN) substrate for effective CO2 capture. The synergistic effect arising from the fast screening channels of the PIM-1-PU polymer layer and the high selectivity of the PL layer induced by enhanced CO2 adsorption endows the resulting membranes with excellent CO2/H2 separation performance. The obtained ZIF-8@[bmim][Tf2N]/PIM-1-PU membrane exhibits a high CO2 permeance of 32 GPU and a CO2/H2 selectivity of 14.6 with a binary CO2/H2 (50/50, v/v) mixture at room temperature, surpassing the 2008 Robeson upper bound. Furthermore, the membrane maintains its stability after 100 h of stability testing as well as a high-pressure testing of 500 kPa. This research provides insights into the strategic design of porous liquid-based composite membranes for advanced gas separation.