Ultrahigh Proton Conduction via Extended Hydrogen-Bonding Network in a Preyssler-Type Polyoxometalate-Based Framework Functionalized with a Lanthanide Ion

The exploration of composition–structure–function relationship in proton-conducting solids remains a challenge materials chemistry. Polyoxometalate-based compounds have been long considered as candidates for proton conductors; however, their low structural stability and large decrease conductivity under reduced relative humidity (RH) limited applications. To overcome such limitations, the hybridization polyoxometalates with polymers has emerged promising method. Besides, 4f lanthanide ions possess high coordination number, which can be utilized to attract water molecules build robust frameworks. Herein, Preyssler-type polyoxometalate functionalized 9-coordinate Eu3+ (Eu[P5W30O110K]11–) is newly synthesized combined poly(allylamine) amine moieties protonation sites. resulting crystalline composite exhibits an ultrahigh >10–2 S cm–1 at 368 K 90% RH, still >10–3 50% due strengthened extended hydrogen-bonding network.