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.