Highly permeable biocatalytic membrane prepared by 3D modification: Metal-organic frameworks ameliorate its stability for micropollutants removal

Aquatic micropollutants seriously affect human health. Biocatalytic membranes with immobilized laccase show a great potential for micropollutants removal. However, highly efficient and stable biocatalytic membranes are still under development. Herein, the separation and support layers of polyacrylonitrile (PAN) ultrafiltration membrane are sequentially modified by polyethyleneimine (PEI), metal-organic frameworks (MOFs), laccase and polydopamine (PDA), termed as three dimensional (3D) modification. The PEI polymers inserted in the selective separation layer result in charge reversal, thus immobilizing laccase mainly by electrostatic adsorption. The water-stable MOFs particles adhered on the support layer fibers can enhance the membrane adsorption capacity to laccase and micropollutants (called dual adsorption effect). PEI and MOFs dominate laccase loading and distribution in the membrane, thus greatly affecting micropollutants removals. The LacPAN-MIL-101-L biocatalytic membrane shows high permeability with desirable micropollutants removal, wide pH operating range and good reusability. Theoretically, this 3D modification strategy can enable all the composite membranes to be biocatalytic membrane prepared by simple reverse filtration and subsequent coating.