Molecularly Programmed Twisting in Hydrogen-Bonded Organic Crystal Enables Anhydrous Superprotonic Conductivity at High Temperatures.

Abstract

A Hydrogen-Bonded Organic Crystal (HOC-88) is reported that achieves unprecedented anhydrous superprotonic conductivity through a molecular topology-driven hierarchical assembly strategy. Single-crystal analysis uncovers a saddle-distorted π-conjugated monomer with eight phenolic hydroxyl groups, whose synergistic geometric confinement enables spontaneous formation of self-templated 3D proton highways-a phenomenon yet to be observed in crystalline organic conductors. The double torsion of the π-system induces helical cooperativity between hydrogen-bonded lamellae and π-π stacked columns, generating interconnected proton pathways with negative thermal expansion behavior along the c-axis. This unique mechanism allows HOC-88 to maintain ultrastable proton conduction without humidity dependence, surpassing all known HOCs and routing state-of-the-art MOF/COF analogues. Crucially, the framework demonstrates chemical omniphobicity-retaining crystallinity in boiling water (100 °C), concentrated acid (0.5 m H₂SO₄ and 1 m HCl), and 300 °C in air conditions. When deployed in an H₂-O₂ fuel cell prototype, it establishes the first experimental evidence of HOC operating in practical high-temperature electrochemical devices. The findings reveal that controlled helical distortion in π-systems can programmatically dictate long-range proton ordering, opening an unexplored dimension for designing next-generation solid electrolytes.