The water-mediated proton conductivity of a 1D open framework inorganic-organic hybrid iron phosphate and its composite membranes

•The 1D open framework metal phosphate exhibits high storage, aqua and thermal stability.•It has remarkable proton conductivity of 5.14 × 10-4 S.cm−1 at 313 K and 99% RH.•Its composite membranes with PVDF exhibit a considerable proton conductivity as powder at similar condition.