Dual-Acid-Tailored Ionic Covalent Organic Frameworks for High-Temperature Proton Conduction under Anhydrous Conditions and the Practical Opportunities

An organic salt (DMAP/Pa-SO3H) composed of 2,5-diaminiobenzenesulfonic acid (Pa-SO3H) and dimethylaminopyridine (DMAP) was demonstrated as a linker to construct ionic covalent organic frameworks (iCOFs). The iCOF denoted as TpDMAP/Pa-SO3H was prepared by the condensation reaction of the triformylphloroglucinol (Tp) building block and DMAP/Pa-SO3H and offers the potential to accommodate an external proton source (H3PO4; PA), enabling the immobilization of PA moieties within the pore structure through a strong ionic hydrogen bonding interaction evidenced by DFT calculations. Furthermore, H3PO4-doped iCOF denoted as PA@TpDMAP/Pa-SO3H proclaimed the advantage of engineering at the linker position, which in turn promotes proton conductivity to 1.56 × 10–2 S cm–1 (increased 100-fold as related to PA@TpPa-SO3H) at 140 °C under anhydrous conditions. Finally, we investigated the adaptability of a dual-acid system in sulfonated poly(ether ether ketone) (SPEEK) membranes, a common acid-modified polymeric material. PA-doped DMAP-modified SPEEK (PA@SPEEK/DMAP) evidenced a 100-fold appreciation of proton conductivity at 120 °C, as compared to bare SPEEK membranes under anhydrous conditions.