Enhancing contaminant rejection efficiency with ZIF-8 molecular sieving in sustainable mixed matrix membranes

Abstract

Compared to pure polymer membranes and inorganic membranes, mixed matrix membranes (MMMs) loaded with metal–organic frameworks (MOFs) exhibit higher permeability and selectivity. Zeolitic imidazolate framework (ZIF) is widely regarded as the most promising candidate for separation membrane materials due to its precise molecular sieving properties. However, there is an urgent need for scalable fabrication methods to produce flexible and sustainable MOF MMMs, which is largely unmet. Here, we report a non-solvent induced phase separation-spin coating (NIPS-SC) strategy for the preparation of highly permeable MOF MMMs. A porous support layer is formed by non-solvent induced phase separation of polyvinylidene fluoride (PVDF) and polyvinylpyrrolidone (PVP). Chitosan (CS), polyvinyl alcohol (PVA), and ZIF-8 are then coated on the PVDF support layer to synthesize the symbiotic and continuous MMM membrane. The synthesized membrane shows excellent separation performance for organic dye and heavy metal ions, as well as significant stability. The water permeate flux of the membrane is 342 L m–2 h−1 bar−1. The micron-scale in the support layer facilitates rapid water permeation, while the porous ZIF-8 provides enhanced solute rejection selectivity. This strategy paves the way for the development of high-performance membranes for water purification.