A proton-conductive metal–organic framework based on imidazole and sulphate ligands

A metal-organic framework (MOF) built from a combination of metal cations, neutral azole ligands and sulphate anions, [Cu₂(DHBDI)₃(SO₄)₂]_n (1, DHBDI = 1H,5H-benzo[1,2-d:4,5-d']diimidazole), was synthesized. MOF 1 exhibits good chemical stability in acids, bases and boiling water while showing high hydrophilicity. Meanwhile, MOF 1 exhibits a proton conductivity of 1.14 × 10^-3 S cm^-1 at 90 °C and 98% RH, among the best for MOF materials with uncoordinated N sites. Temperature-dependent conductivity measurements suggest a vehicle mechanism (E_a = 0.64 eV) for proton transport.