Multivariate synergy for heightening ionic HOF robustness and proton conductivity

Multicomponent crystalline materials construct more complex and diversified structures with different combinations and modes, which expands the material structure space and application fields. In this work, we have successfully synthesized two two-component ionic hydrogen-bonded organic frameworks (iHOF-32 and iHOF-33) and a three-component iHOF (iHOF-34). Guanidine hydrochloride which is rich in N and H and has a short chain length strengthens the hydrogen bonding network of iHOF, thereby aiding in the efficient migration of protons. The rigid architecture of 1,1 '-diamino-4,4 '-bipyridine diiodide furnishes additional scaffolding for the iHOFs and enhances its robustness under harsh conditions. iHOF-34 accomplishes the combination of the ultra-high proton conductivity of iHOF-32 and the robustness of iHOF-33 by the synergistic interaction among the three components of ligands. In addition, iHOF-34 was fabricated as a composite membrane with a peak proton conductivity of 1.55 x 10-1 S cm-1, which is 3.8 times higher than that of recast Nafion, and has extensive potential in fuel cells. The self-assembly strategy of multicomponent HOFs opens up new avenues for constructing diverse structures while promising new opportunities for applications in the fields of proton conduction and energy storage.