Polyimide gas separation membrane with an ultrahigh molecule sieving ability by interchain hydrogen-bonding and thermo-oxidative cross-linking networks

A series of highly selective polyimide gas separation membranes were successfully synthesized by reacting the newly synthesized dianhydride monomers containing the amide unit and benzyl group with a commercial diamine, 1,3,5-trimethyl-2,4-phenylenediamine (DAM). The combination of the intermolecular hydrogen-bonding interaction from the amide-imide backbone and the thermo-oxidative cross-linking network induced by the benzyl units endows the membrane with a strong size-sieving capability with an ideal CO 2 /CH 4 selectivity > 125 (over six times higher than that of the commercial Matrimid 5218) with a moderate CO 2 permeability, ranking the top among that of the polyimide gas separation membranes reported so far. The comprehensive separation performance for the CO 2 /CH 4 gas pair surpasses the state-of-the-art 2008 upper bound. Moreover, the prepared membrane showed an increased stability toward high CO 2 pressure of 12 bar, demonstrating an excellent plasticization resistance due to the tightened molecular packing and confined molecular chain motion as well as the rigid nature of the polymer backbone, which also enabled high glass transition temperatures (>400 °C) and fine mechanical properties (tensile strength > 52 MPa) as well as an anti-aging property of the prepared membranes. This study provides a reliable route for constructing polymer membranes with an accurate gas molecular sieving ability and high durability.