Coherent Fusion of Water Array and Protonated Amine in a Metal–Sulfate-Based Coordination Polymer for Proton Conduction

A new function of metal–sulfate-based coordination polymer (CP) for proton conduction was investigated through rational integration of a continuous water array and protonated amine in the coordination space of the CP. The H-bonded arrays of water molecules along with nitrogen-rich aromatic cation (protonated melamine) facilitate proton conduction in the compound under humid conditions. Although several reports of metal–oxalate/phosphate-based CPs showing proton conduction are known, this is the first designed synthesis of a metal–sulfate-based CP bearing water arrays functioning as a solid-state proton conductor.