An Azo-bridged porous organic polymers modified poly(phthalazinone ether sulfone ketone) membrane for efficient O2/N2 separation

Abstract

Polymeric membranes with high permeability for oxygen separation are highly demanded for a variety of industrial sectors. We herein developed a novel multi-component membrane system with improved O2/N2 separation performance, through physical blending an azo-bridged porous organic polymers (AZOPOP) with commercially available poly(phthalazinone ether sulfone ketone) (PPESK). The AZOPOP, featuring an acceptable BET surface area and a dominant pore size centered at 0.95 nm and 27 nm, was facilely synthesized through Mills polycondensation between 2,6-dinitrosotriptycene and 2-(4-aniline)-4-(4-phenylamine) (2H) naphthyridin-1-one containing phthalazinone. The composite membrane AZOPOP/PPESK37 showed an excellent O2 permeability (e.g., PO2 = 1944 barrer) and ideal selectivity (PO2/PN2 = 2.6) for O2/N2 pair, which surpassed the 1991 Robeson upper bound and approached to the 2008 Robeson upper bound. Its higher flux over neat PPESK was attributed to abundant pores and good compatibility between the matrix resin and filler, while the decent selectivity for O2/N2 was induced by nitrogen-phobic functional groups incorporated. This work provides an alternative strategy to fabricate polymeric membranes that have great potentials for O2/N2 separations by taking advantages from the porous structures contributed by rigid chain conformations of AZOPOP.