Polybenzimidazole-based polymers of intrinsic microporosity membrane for high-temperature proton conduction

Anhydrous proton conducting polymer membrane materials have raised much attention in the application of high-temperature proton-exchange membranes (HT-PEMs) fuel cells, which convert chemical energy into electrical energy. Polybenzimidazole-based polymers, as typical materials for HT-PEMs, their compact structures result in small fractional free volumes (FFV), which is not conducive to the adsorption and retention of proton carriers. Herein, a series of polybenzimidazole-based polymers of intrinsic microporosity (PIM-PBIs) were synthesized. PIM-PBIs possess the benzimidazole units and porous structures, and have good thermal stability and large specific surface area (100 ∼ 400 m²/g). PIM-PBIs are further embedded in polyvinylidene fluoride (PVDF) to form mixed matrix membranes for high-temperature proton conduction. The resulting membranes exhibit high proton conductivity up to 90.11 mS cm⁻¹ at 140 ℃ and high phosphoric acid (PA) retention rate of 90.0 %. This work provides a facile method for the precise design and preparation of proton-conducting porous materials.