High Li⁺ and Mg²⁺ Conductivity in a Cu-Azolate Metal-Organic Framework

A Cu-azolate metal-organic framework (MOF) uptakes stoichiometric loadings of Groups 1 and 2 metal halides, demonstrating efficient reversible release and reincorporation of immobilized anions within the framework. Ion-pairing interactions lead to anion-dependent Li⁺ and Mg²⁺ transport in Cu₄(ttpm)₂·0.6CuCl₂, whose high surface area affords a high density of uniformly distributed mobile metal cations and halide binding sites. The ability to systematically tune the ionic conductivity yields a solid electrolyte with a Mg²⁺ ion conductivity rivaling the best materials reported to date. This MOF is one of the first in a promising class of frameworks that introduces the opportunity to control the identity, geometry, and distribution of the cation hopping sites, offering a versatile template for application-directed design of solid electrolytes.