Metal-organic framework anchored sulfonated poly(ether sulfone) as a high temperature proton exchange membrane for fuel cells

Abstract

A proton-conducting sulfonated poly(ether sulfone)-metal-organic framework membrane with high proton conductivity at high temperature and anhydrous conditions was synthesized by anchoring the Cr-MIL-101-NH2 to the aromatic polymer backbone via a Hinsberg reaction. The effect of metal-organic frameworks as the pendant porous aminated moieties on membrane features such as water uptake, swelling ratio, mechanical, oxidative and thermal stabilities, morphology, acid retention capacity, ion exchange capacity, long-term durability, hydrogen crossover, proton conductivity and fuel cell performance was methodically studied. The presence of holes and -NH2 groups in the metal-organic frameworks structure enhanced the acid retention capacity of the sulfonated poly(ether sulfone)-metal-organic framework membrane. This behavior resulted in the satisfactory performance of the membrane at high temperatures and low humidity (the proton conductivity of the membrane was increased to 0.041 S cm−1 (as compared to Nafion = 0.003 S cm−1) at 160 °C). Moreover, the crosslinking process which produced by metal-organic frameworks increased the dimensional stability (the swelling ratio was reduced from 57% to 4%), oxidative resistance, tensile strength, water uptake, and hydrogen crossover of the polymer.