Superprotonic Conductivity in Metal-Organic Frameworks by Charged-Layer-Mediated Proton Conduction

Through a stepwise functionalization strategy, LiCl@UiO-66-F ( 2 ) (SO ( 3 ) H) ( 2 ) manifestsa superprotonicconductivity of 2.86 S cm(-1) (at 90% RH and 90 & DEG;C),a record breaker so far. Supported by joint experimental-theoreticalstudies, the ultrahigh conductivity originates from conduction byprotons rather than ions and is rationalized to result from the enhancedacidity of -SO3H by introduction of electronegative-F followed by the formation of double charged layers composedof Li+ and -SO3 (-) layersafter encapsulation of LiCl. Importantly, the effect of charged layershas been verified, and charged-layer-mediated proton conduction isunprecedentedly proposed to fill in the missing pieces in existingproton conduction mechanisms, giving insight into the rational designof superprotonic conducting framework materials potentially appliedas proton exchange membranes in fuel cells.