In-Situ Gelled Covalent Organic Framework Membrane with Vacancies-Enhanced Anhydrous Proton Conductivity

The development of high-performance anhydrous proton-exchange membranes (APEMs) for electrochemical techniques remains a significant challenge. Covalent organic frameworks (COFs) offer a promising solution for APEMs due to their tunable channels and functionalizable skeletons. However, COFs are typically porous powders, which create extreme difficulties in processing them into self-standing APEMs, thereby limiting their practical applications. In this study, we propose a novel strategy for preparing COF-based APEMs for high-temperature proton exchange membrane fuel cell (HT-PEMFC) applications through acidification and gelation. In the gel, COF acts as both a gelling agent and proton trap, inhibits guest acid flow, and captures protons from the acid, leading to the formation of proton vacancies in the COF gel and greatly accelerating proton migration. As a result, COF gel membranes exhibit conductivities that far surpass that of the guest acid itself, exceeding 0.1 S cm^-1 at temperatures above 140 °C, outperforming most reported COF materials. Notably, membrane electrode assemblies of HT-PEMFCs fabricated with a COF gel achieve a maximum power density of 150 mW cm^-2 at 180 °C and anhydrous conditions. Our approach introduces an innovative strategy for the fabrication of self-standing COF-based APEMs, representing a significant breakthrough in the field of COF-based APEMs for fuel cell technology.