Chlorosulfonated Polyphenylene Ether Metal–Organic Framework Nanomaterial Composite Proton Exchange Membranes for Fuel Cells

Proton exchange membrane (PEM) is a key part of a PEM fuel battery. It is a challenge in the development of PEMs to enhance the proton conductivity. A series of chlorosulfonated polyphenylene ether (PPO–SO2–Cl)–metal–organic framework (MOF) nanomaterial composite membranes with high proton conductivity, named MOF-SO2–PPO, were prepared by anchoring Cr-MIL-101-NH2 nanoparticles in PPO–SO2–Cl through Hinsberg reaction. A directly physically doped membrane based on sulfonated poly(phenyl ether) (SPPO) and MOF, named MOF/SPPO, was also prepared. The water absorption, swelling ratio, ion exchange capacity, and proton conductivity of the two composite membranes were tested. The MOF-SO2–PPO membranes had better thermal stability and water absorption than the membranes formed by traditional doping. At 343 K and 98% relative humidity, MOF-SO2–PPO exhibited a high proton conductivity of 4.9 × 10–2 ± 2.3% S cm–1, which was 1.96 times that of MOF/SPPO. Furthermore, additional modification entailed anchoring the MOF, modified with ionic liquid, onto PPO–SO2–Cl, yielding IL-MOF-SO2–PPO-3 with optimal content. The proton conductivity of IL-MOF-SO2–PPO-3 surpassed that of SPPO by 24 times. This work provides feasible insights into the application of MOF nanomaterials to PEMs in fuel cells.