A series of MIL-101-SO3H/Nafion composite membranes was synthesized. They show an improved proton conductivity, due to the abundance of SO3H groups, which fosters proton conduction by binding the water molecules and enabling a larger number of conducting sites. Gas (including water vapor, hydrogen, and oxygen) permeability, crystallinity, and free volumes of the MIL-101-SO3H/Nafion composite membranes were investigated, as well as their correlation. By increasing the MIL-101-SO3H content, the gas permeability of the membranes significantly decreases, since the crystalline region is larger and ...
