Tuning sulfonated crystalline nanochannels to accelerate proton transport in aramid nanofibers-reinforced CONs membranes

Covalent organic framework nanosheets (CONs) have become intriguing nanoscale building blocks for proton transport due to tunable pore parameters and facile film-forming properties. However, insufficient interlamellar linkages among CONs bring some sacrifice in integrity and compactness on CONs membranes. Also, it remains elusive to establish direct correlations between pore nanostructure and proton conductivity. Herein, three sulfonated CONs with similar skeletons but different pore microstructures are synthesized and restacked into intact sulfonated CONs-based composite membranes through the “bridge effect” of aramid nanofibers (ANFs) exfoliated from macroscopic Kevlar fibers. The pore size, structural regularity, −SO 3 H groups distance/amount, flake thickness and lateral size of sulfonated CONs are adjusted by changing amine monomer/solvent types of interface polymerization reactions. ANFs-linked sulfonated CONs-based membranes (CONs as the primary components) harvest dense inner structure, decent sulfonation degree/surface hydrophilicity and desirable dimensional/mechanical/thermal/antioxidative/chemical stabilities. It is observed that − SO 3 H carrier distance, carrier concentration and pathway crystallinity have synergistic effects on H-bond proton migration networks constructed by tethered − SO 3 H and entrapped H 2 O within porous nanosheet-stacked channels. The optimal sulfonated CONs-based membrane affords superprotonic conductivity of 439 mS cm −1 (80 °C, 95 % RH). This work offers inspiration and guideline for designing function-oriented CONs and constructing well-integrated nanoporous transfer channels.