Accumulation of Sulfonic Acid Groups Anchored in Covalent Organic Frameworks as an Intrinsic Proton-Conducting Electrolyte

Covalent organic frameworks (COFs) are a novel class of crystalline porous polymers, which possessed high porosity, excellent stability, and regular nanochannels. Two-dimensional (2D) COFs provided 1D nanochannel to form the proton transport channels. The abovementioned features afforded a powerful potential platform for designing materials as proton transportation carriers. Herein, we incorporated sulfonic acid groups on the pore walls as proton sources for enhancing proton transport conductivity in the 1D channel. Interestingly, the sulfonic acid COFs (S-COFs) electrolytes with binder free exhibited excellent proton conductivity about 1.5 × 10^-2 S cm^-1 at 25 ℃ and 95% relative humidity (RH), which ranked the excellent performance in standard proton-conducting electrolytes. The S-COFs electrolytes kept the high proton conduction over the 24 h. The activation energy was estimated to be as low as 0.17 eV, which was much lower than most reported COFs. This research opens a new window to evolve great potential of structural design for COFs as the high proton-conducting electrolytes