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

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.