Hierarchically Macro-Microporous Covalent Organic Frameworks for Efficient Proton Conduction

Assembling molecular proton carriers into crosslinked networks is widely used to fabricate proton conductors, but they often suffer losses in conduction efficiency and stability accompanied by unclear causes. Covalent organic frameworks (COFs), with well-defined crystal frameworks and excellent stability, offer a platform for exploring the proton transfer process. Herein, a strategy to construct proton conductors that induce conductivity and stability by introducing bottom-up hierarchical structure, mass transport interfaces, and host-guest interactions into the COFs is proposed. The proton-transport platforms are designed to possess hierarchically macro-microporous structure for proton storage and mass transport. The protic ionic liquids, with low proton dissociation energies investigated by DFT calculation, are installed at open channel walls for faster proton motion. As expected, the resultant proton conductors based on a covalent organic framework (PIL0.5@m-TpPa-SO3H) with hierarchical pores increase conductivity by approximately three orders of magnitude, achieving the value of 1.02 x 10(-1) S cm(-1) (90 degrees C, 100% RH), and maintain excellent stability. In addition, molecular dynamics simulations reveal the mechanism of "hydrogen-bond network" for proton conduction. This work offers a fresh perspective on COF-based material manufacturing for high-performance proton conductors via a protocol of macro-micropores.