Ultrafast and Stable Proton Conduction in Polybenzimidazole Covalent Organic Frameworks via Confinement and Activation

Abstract Polybenzimidazoles are engineering plastics with superb thermal stability and this specificity has sparked a wide‐ranging research to explore proton‐conducting materials. Nevertheless, such materials encounter challenging issues owing to phosphoric acid proton carrier leakage and slow proton transport. We report a strategy for designing porous polybenzimidazole frameworks to address these key fundamental issues. The built‐in channels are designed to be one‐dimensionally extended, unidirectionally aligned, and fully occupied by neat phosphoric acid, while the benzimidazole walls trigger multipoint, multichain, and multitype interactions to spatially confine a phosphoric acid network in pores and facilitate proton conduction via deprotonation. The materials exhibit ultrafast and stable proton conduction for low proton carrier content and activation energy—a set of features highly desired for proton transport. Our results offer a design strategy for the fabrication of porous polybenzimidazoles for use in energy conversion applications.