High proton conductivity of MOFs-polymer composite membranes by phosphoric acid impregnation

Abstract Metal-organic frameworks (MOFs) show promise as potential components in proton exchange membranes (PEMs). Powder-form MOFs lacks flexibility and processability, issues which can be overcome with the addition of polymers. We demonstrate a novel MOFs-polymer composite membrane with relatively high flexibility and proton conductivity. The composite membrane, denoted Ni-BDC-PAN, was fabricated from Ni-BDC (BDC = 1,4-benzenedicarboxylate) nanosheets and polyacrylonitrile (PAN), which endows the crystalline MOFs with exceptional flexibility and acid stability. Soaking this Ni-BDC-PAN membrane in phosphoric acid solutions produced a new proton-conducting membrane, H3PO4@Ni-BDC-PAN, which exhibited a super protonic conductivity up to 1.05 × 10−2 S cm−1 at 353 K under 90% relative humidity (RH). Additionally, the activation energy (Ea) was investigated in order to better understand the proton conduction mechanism in the hybrid membrane.