Construction of ordered OH- migration channels in anion exchange membrane by synergizes of cationic metal-organic framework and quaternary ammonium groups

A series of anion exchange membranes (quaternized chitosan/cation metal-organic framework [MIL-X-QCS]) were prepared via purposeful inserting the cationic metal-organic framework as the multifunctional filler into quaternized chitosan (QCS). The successful preparation of the anion exchange membrane was confirmed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and Scanning electron microscope (SEM). In this research, we converted the charge-balanced MOFs skeleton Cr-MIL-101 into the cationic metal skeleton (Cr-MIL-101)Cl-+(-) by anion stripping, and cooperated with quaternary amine groups to construct a high-speed OH- transmission channel. The introduction of a rigid MOF structure reduces the water uptake and swelling ratio of the composite membrane by 27% and 37%, respectively. At 80 degrees C, the OH- conductivity of the MIL-9-QCS membrane (The composite membrane doped with 9 wt% Cr-MIL-101 crystals) reaches 2.30 x 10(-2) S center dot cm(-1) and the power density reached its maximum (90.2 mW center dot cm(-2)), and the tensile strength reaches 20.12 MPa, which was higher than 18.7 MPa of Nafion-115 membrane. The spatial network structure of MOFs reduced the methanol permeability of MIL-9-QCS membrane by 24% compared with the original QCS membrane. Furthermore, the MIL-9-QCS composite membrane exhibited excellent alkali stability, where after being soaked in 2 mol L-1 NaOH solution at 60 degrees C for 240 hours, its OH- conductivity still reached 77% of the initial value.

Automated summary

A series of anion exchange membranes were prepared by inserting cationic metal-organic framework into quaternized chitosan, resulting in improved OH- conductivity and alkali stability. The introduction of MOFs structure reduced water uptake, swelling ratio, and methanol permeability of the composite membranes.