Modifier-Driven Proton Conductivity in Hybrid Glasses above 200 °C

Compositional tuning is a cornerstone of inorganic glass science, yet analogous strategies remain underdeveloped for emerging metal-organic hybrid glasses. We introduce phosphate modification of zinc imidazolate glass as a route to hybrid glasses with tunable network connectivity and proton-conductive functionality. Melt-quenching of ZIF-zni with benzimidazolium dihydrogen phosphate (BP) affords a series of cm-scale, transparent bulk glasses across a wide compositional range. Systematic characterization reveals that modification proceeds through ligand exchange at zinc centers, increasing the average coordination number from 4 to above 5 and progressively depolymerizing the imidazolate network. Despite macroscopic homogeneity, X-ray total scattering identifies a quasi-periodic ordering at ∼11 Å, and 1H NMR spin relaxation establishes nanoscale phase segregation between ZIF-derived and BP-rich domains of 2-70 nm. This heterogeneity underpins proton transport under anhydrous conditions; conductivities of 10-5-10-3 S cm-1 at 240 °C follow Vogel-Tammann-Fulcher dynamics, confirming that segmental motion couples to ion mobility. Infiltrating the glass into a porous PTFE scaffold yields a composite membrane that achieves 8.4 × 10-5 S cm-1 at 170 °C under humidification and sustains steam electrolysis with near-unity Faradaic efficiency. These results establish network-modified hybrid glasses as a scalable and designable platform for intermediate-temperature solid electrolytes.