Mixed Ionic–Electronic Transport in Metal–Organic Frameworks

Ion transport in metal-organic frameworks (MOFs) is attracting increasing attention, as ions can be easily incorporated into porous MOF structures as guest species, promising a variety of possible applications. While electronically insulating but ionically conductive MOFs show great potential as solid electrolytes, the precise structure and tunability of MOFs also enable a rational combination of electronic and ionic conductivity to create intrinsic mixed conductors. In this perspective, we discuss structure-function relationships in ionically conductive MOFs, pointing toward fundamental research opportunities, and lay out strategies to enable and characterize mixed ionic-electronic transport properties.