Constructing Amino-Functionalized Flower-like Metal–Organic Framework Nanofibers in Sulfonated Poly(ether sulfone) Proton Exchange Membrane for Simultaneously Enhancing Interface Compatibility and Proton Conduction

A novel flower-like MIL-53(Al)-NH2 nanofiber (MNF) was successfully constructed, in which the electro-blown spinning Al2O3 nanofibers were introduced as Al precursors to coordinate with ligand in hydrothermal reaction for the formation of MOFs nanofibers. By incorporating the functional and consecutive MNFs fillers in sulfonated poly(ether sulfone) (SPES) matrix, high-performance MNFs@SPES hybrid membranes were obtained. Specifically, the peak stress strength could be strengthened to 33.42 MPa and the proton conductivity was remarkably improved to 0.201 S cm–1 as MNFs content increased to 5 wt %, achieving a simultaneous improvement on proton conduction and membrane stability. The highly promoted performance could be ascribed to the synergy advantages of unique structure and amino modification of MNFs: (1) The flower-like nanofiber structure of MNFs with high surface area could be beneficial to construct long-range and compatible interfaces between MNFs and SPES matrix, leading to sufficient continuous proton pathways as well as strengthened stability for the hybrid membrane. (2) The hydrophilic MNFs rendered the hybrid membrane with sufficient water retention for proton transfer via Vehicle mechanism. (3) Functional -NH2 groups of MNFs and -SO3H groups of SPES were consecutively and tightly bonded via acid–base electrostatic interactions, which further accelerated the proton conduction via Grotthuss hopping mechanism and effectively suppressed the methanol penetration in the meanwhile for the MNFs@SPES hybrid membranes.