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

Abstract A 1D open framework inorganic-organic hybrid metal phosphate, compound (C4H12N2)1.5[Fe2(OH)(H2PO4)(HPO4)2(PO4)].0.5(H2O) was synthesized via solvothermal method. The inorganic anion layer is built from FeO6 cluster units, and the interlayer spaces are filled by the charge-compensated piperazinium cations. The resultant compound had high storage, aqua and thermal stability by placing its samples in the air for one year, immersing in water for 7 days and performing in the temperature range of 298–1073 K with TG analysis, respectively. This compound exhibited significant temperature and humidity dependence proton conductivity, achieving 5.14 × 10-4 S.cm−1 at 313 K and 99% RH. Moreover, its composite membranes with PVDF also possessed good and sustaining proton conduction behavior (3.78 × 10-4 S.cm−1 at 323 K and 99 %RH), closing to that of its powder although the PVDF isn’t electric conductive.