Proton Superhighways Enabled by Hofmeister-Electrostatic Synergy in All-Inorganic Polyoxometalate Hydrogels for...

Constructing polyoxometalate-counterion systems capable of forming precise supramolecular nanostructures is critically important but highly challenging. Here ion-specific effects are exploited to orchestrate multiscale phase transitions in isopolyoxometalate-cation supramolecular assemblies, enabling on-demand transformation from macrophase separation to nanostructured hydrogels. Gelation proceeds through ion-pair-driven charge inversion of the clusters, facilitating 1D supramolecular polymerization mediated by salting-in anions through synergistic hydrogen bonding and electrostatic interactions. Crucially, these ion-engineered hydrogels exhibit anomalous proton conduction over a wide temperature range, enabling temperature sensors with ultra-wide operational range, high sensitivity, and great stability. Integration of these sensors enabled real-time thermal hazard mitigation in a prototype battery safety system. This work pioneers salting-in anions encapsulation in isopolyoxometalate-counterion systems to achieve inorganic soft superstructures, uncovering a previously unrecognized general Hofmeister-electrostatic assembly principle in cluster chemistry.