Proton conduction in crystalline and porous covalent organic frameworks

Progress over the past decades in proton-conducting materials has generated a variety of polyelectrolytes and microporous polymers. However, most studies are still based on a preconception that large pores eventually cause simply flow of proton carriers rather than efficient conduction of proton ions, which precludes the exploration of large-pore polymers for proton transport. Here, we demonstrate proton conduction across mesoporous channels in a crystalline covalent organic framework. The frameworks are designed to constitute hexagonally aligned, dense, mesoporous channels that allow for loading of N-heterocyclic proton carriers. The frameworks achieve proton conductivities that are 2-4 orders of magnitude higher than those of microporous and non-porous polymers. Temperature-dependent and isotopic experiments revealed that the proton transport in these channels is controlled by a low-energy-barrier hopping mechanism. Our results reveal a platform based on porous covalent organic frameworks for proton conduction.