Highly conductive and robust composite anion exchange membranes by incorporating quaternized MIL-101(Cr)

With well-defined channels and tunable functionality, metal-organic frameworks(MOFs) have inspired the design of a new class of ion-conductive compounds. In contrast to the extensive studies on protonconductive MOFs and related membranes attractive for fuel cells, rare reports focus on MOFs in preparation of anion exchange membranes. In this study, chloromethylated MIL-101(Cr) was prepared and incorporated into chloromethylated poly(ether ether ketone)(PEEK) as a multifunctional filler to prepare imidazolium PEEK/imidazolium MIL-101(Cr)(Im PEEK/Im MIL-101(Cr)) anion exchange membrane after synchronous quaternization. The successful synthesis and chloromethylation of MIL-101(Cr) were verified by transmission electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy while the enhanced performance of composite membranes in hydroxide conductivity, mechanical strength and dimensional stability were evaluated by alternating-current impedance, electronic stretching machine and measurement of swelling ratio. Specifically, incorporating 5.0 wt% Im MIL-101(Cr)afforded a 71.4% increase in hydroxide conductivity at 20 °C, 100% RH. Besides, the composite membranes exhibited enhanced dimensional stability and mechanical strength due to the rigid framework of Im MIL-101(Cr). At room temperature and the Im MIL-101(Cr) content of 10 wt%, the swelling ratio of the Im PEEK/Im MIL-101(Cr) was 70.04% lower while the tensile strength was 47.5% higher than that of the pure membrane.