Guest-Assisted Proton Conduction in the Sulfonic Mesoporous MIL-101 MOF

Post-synthesis modification of MIL-101(Cr)-NO₂ was explored in order to decorate the organic backbone by propyl-sulfonic groups, with the aim to incorporate mobile and acidic protons for solid-state proton electrolyte applications. The resulting solid switched from insulating towards proton superconductive behavior under humidity, while the conductivity recorded at 363 K and 95 % relative humidity reached 4.8×10^-3  S cm^-1 . Propitiously, the impregnation of the material by strong acidic molecules (H₂ SO₄ ) further boosted the proton conductivity performances up to the remarkable σ value of 1.3×10^-1  S cm^-1 at 363 K/95 % RH, which reaches the performances of the best proton conductive MOF reported so far.