Unusual Hydrogen Solubility and Selectivity in Charge-Transfer Phthalonitrile Prepolymer and Polyimide Blend Membranes

Abstract

Hydrogen economy holds great promise as the next generation of clean energy. The increasing demand for H2 production from syngas and ammonia has necessitated the development of high-performance H2-selective polymers. Polyimides are considered promising materials for hydrogen purification for their excellent thermal and chemical stability; however, commercial polyimides generally possess insufficient hydrogen selectivity.For practical applications, it is critical to improving the hydrogen selectivity of polyimides. Herein, we report a facile material strategy to adjust the H2 separation performance via blending the polyimide and the crosslinkable resorcinol-based phthalonitrile prepolymer (RPN) with electron donor/acceptor properties. The novel RPN30/PI70 membrane showed outstanding H2/N2 and H2/CO2 permselectivity of 1637 and 66, respectively, with the H2 permeability about 2.7 Barrer, surpassing the H2/N2 and H2/CO2 Robeson upper bounds (2008). The improved H2 permselectivity was attributed to the tunable microstructure in the charge-transfer RPN/PI blend, giving rise to the outstanding H2 solubility and H2/N2 and H2/CO2 solubility selectivity. Moreover, the H2 permeability and selectivity of the RPN/PI membranes can be further optimized via thermal treatment. This study demonstrates a new versatile strategy for designing high-performance hydrogen-selective polymeric membranes.

Keywords: Phthalonitrile resin, Crosslinkable electron-donor-acceptor prepolymer, polyimide, Polymer blend, Hydrogen purification membrane