Superprotonic Conduction over Wide Humidity Range Driven by Enhanced Proton Dissociation

Proton-conducting materials play a key role in various fields, and their proton conduction is profoundly restricted by the proton dissociation process. This process has two components: dissociation from acidic groups (e.g., -SO3H) and dissociation from intermediate species (e.g., H3O+, C─F···H+). Extensive research has concentrated on the former, utilizing acidic groups with minimal proton dissociation energy or low pKa values, while the latter's substantial effects have been largely overlooked. In reality, proton-accepting atoms within intermediates, such as oxygen and nitrogen, typically produce a higher electron cloud density compared to those in acidic groups. This results in a pronounced electrostatic binding effect on mobile protons, as well as high dissociation energies. Thus, diminishing the dissociation energy associated with intermediates is paramount in the development of high-performance proton conductors. Herein, we construct one covalent organic framework-based proton conductor, achieving superprotonic conduction over a wide humidity range by decreasing the dissociation energy of protons from intermediates. The success of this approach can be attributed to two key factors: the crowded guest molecules within the framework that mitigate proton hydration, and the concurrent establishment of C─H···H+ interactions. These combined effects significantly reduce the electrostatic attraction exerted on mobile protons, thereby enhancing proton conduction.