CsHSO4 — Proton conduction in a crystalline metal–organic framework
Abstract The approach, combining metal–organic frameworks and functional guests such as proton conductors of M m H n (XO 4 ) p family has been proposed and successfully realized in the (1 − x)CsHSO 4 –xCr-MIL-101 nanocomposites. The (1 − x)CsHSO 4 –xCr-MIL-101 (x = 0–0.07) hybrid compounds with unusual transport, structural and thermodynamic properties have been synthesized and investigated by impedance, infrared spectroscopy and XRD methods. The addition of the nonconducting matrix to CsHSO 4 results in decrease of the temperature of superionic phase transition and considerable increase (up to 2 orders of magnitude) of proton conductivity of CsHSO 4 in low temperature phase due to its disordered state in cavities of Cr-MIL-101 with the maximum conductivity at x = 0.02–0.04. As a result (1 − x)CsHSO 4 –xCr-MIL-101 nanocomposites have proton conductivity 10 − 7 –10 − 2  S/cm at temperatures 50–200 °C and thermal stability up to 190 °C. Nanocomposite effect is similar to known CsHSO 4 –SiO 2 and CsHSO 4 –TiO 2 systems, however is not so high. The used approach may be perspective for the other composite systems with proton conductivity.