High Li + and Mg 2+ conductivity in a Cu-azolate metal-organic framework.

A Cu-azolate metal-organic framework uptakes stoichiometric loadings of Group 1 and 2 metal halides, demonstrating effi-cient 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 versa-tile template for application-directed design of solid electro-lytes.