Assembly of a Pebble-Type Giant Polyoxometalate Cage {Mo₁₀₈} for Proton Conduction

The modular assembly for high-nuclearity clusters is crucial for elucidating structure-activity relationships and broadening their functional applications. Herein, we prepared a novel pebble-type giant polyoxomolybdate cage Na₆H₁₄[Mo^VI₈₄Mo^V₂₄O₃₀₆(OH)₃₂]·130H₂O {Mo₁₀₈} via hydrothermal methods. The {Mo₁₀₈} cage features an elliptical molybdenum wheel {Mo₉₀} capped by three different small molybdenum building blocks with a flat inner cavity (6 Å). Moreover, {Mo₁₀₈} exhibits a proton conductivity of 5.14 × 10^-3 S·cm^-1 at 95 °C under 98% relative humidity.