Hybrid proton exchange membrane used in fuel cell with amino-functionalized metal–organic framework in sulfonated polyimide to construct efficient ion transport channel

This paper focuses on the preparation and fuel cell application of an organic–inorganic composite membrane. The composite membranes are based on sulfonated polyimide and MIL-101(Fe)-NH2 metal–organic framework containing amino flexible side chains is introduced as filler which can form an acid–base pair through hydrogen bonding with sulfonic acid groups on the polymer main chain to increase ion transport channels. Then, the proton transport mechanism in the membrane is explained by discussing the internal structure of the filler and the blend membrane. Specifically, the peak stress intensity of the composite membrane can be enhanced to 132.5 MPa, and the proton conductivity can be significantly increased to 0.194 S cm−1, respectively. This improved performance can be attributed to the unique structure of MOF and the synergistic effect of amino modification, and the porous structure is conducive to the formation of continuous transmission path and the tightly acid–base electrostatic interactions can accelerates proton conduction through the Grotthus mechanism.Graphical abstractStructure and possible conduction mechanism of SPI-Fe@MOF hybrid membranes