Fast Conduction of Organic Cations in Metal Sulfate Frameworks

We demonstrated a new method of synthesizing crystalline organic cation conductors. The conductivities of various organic cations involved in a one-dimensional zinc sulfate framework were studied. The optimized structure (EMIm)2[Zn­(SO4)2] exhibited an ionic conductivity of 3.8 × 10–3 S cm–1 at 210 °C, which is comparable to that of highly conductive organic ionic plastic crystals. The high ionic conductivity is attributable to the defect structures of the organic cations in the inorganic frameworks. The pulsed-field gradient solid-state NMR technique revealed that the self-diffusion coefficient of organic cations in the zinc sulfate at 80 °C is comparable to that of the popular ionic liquid EMIm-BF4 at 30 °C, which indicates that liquid-like fast transporting of organic cation is achieved in the robust crystal structure.