Probing Local Coordination Environments in Proton-Conducting Metal-Organic Glasses with X-ray Total Scattering

To date, phosphate–imidazole metal-organic glasses that pair high proton conductivity with robust operation remain scarce; most lose stability below 180 °C due to imidazole decomposition. The intermediate-temperature range (180–300 °C) is therefore usually inaccessible. We now developed a strategy to suppress this failure by substituting Zn²⁺ with Al³⁺ and replacing imidazole with 4-carboxyimidazole, while tuning phosphate/ligand ratios. The derived MOGs display elevated glass transition temperatures and delayed decomposition yet retain high proton conductivity. This stabilization is a signature of strengthened metal–ligand connectivity and emergent carboxylate coordination that lowers the free-energy cost of maintaining a connected network under heat. Via X-ray total scattering at ID22, we aim to resolve whether carboxylates bind directly to the metal centers, how Al³⁺ substitution alters local topology, and how these changes govern the glass structures and their proton conductivity.