Proton Conductivity, Stability and Potential for Polymorphism in Metal-Organic Framework Minerals

We demonstrate that rare metal-organic framework (MOF) minerals stepanovite and zhemchuzhnikovite can exhibit properties comparable to known oxalate MOFs, including high proton conductivity at 25 <sup>o</sup>C, and retention of the framework structure upon thermal dehydration. They also have high thermodynamic stability, with a pronounced stabilizing effect of substituting aluminium for iron, illustrating a simple design to access stable, highly proton-conductive MOFs without using complex organic ligands. <br>