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 oC, 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.