Highly Efficient Oil–Water Separation in Different Scenarios through Synergistic Self-Assembly of ZIF-67@PPy Coatings with Unique Wetting Properties

In recent years, oil pollution and industrial organic pollutants discharge has become a major problem affecting the ecological and human living environment, and the removal of oil in oily wastewater is increasingly urgent, especially for emulsion separation. Therefore, it is crucial to develop efficient oil-water separation membranes with low cost, green sustainability, and ease of operation. Herein, an ingenious spraying hybrid coatings containing ZIF-67 (Zeolitic Imidazolate Framework-67) and polypyrrole (PPy) onto stainless steel mesh (SSM) and polyvinylidene fluoride (PVDF) was proposed. Through solidification and cooperative self-assembly to build rough structures, oil-water separation membranes ZIF-67@PPy SSM and ZIF-67@PPy PVDF have been obtained, which are hydrophilic and oleophilic in air and superoleophobic underwater. Depending on the scenario, on-demand separation of light oil/water mixtures and oil-in-water emulsions can be easily realized. The resulting oil-water separation membranes performed well that the separation efficiency of ZIF-67@PPy SSM can exceed 99.3% for all kinds of light oil/water mixtures, with a water flux of up to 66250 L/(m²·h), and maintains a separation efficiency of 98.5% even after 50 cycles. ZIF-67@PPy PVDF has a separation efficiency of more than 99.4% for various oil-in-water emulsions, and sustains outstanding performance despite undergoing 10 cycles. In addition, ZIF-67@PPy SSM and ZIF-67@PPy PVDF are sustainable in harsh environments, with good mechanical durability and some antimicrobial properties. The coatings prepared in this work that can be used for the separation of light oil/water mixtures and oil-in-water emulsions, and the proposed combination of multiple separation strategies are expected to improve the selectivity, improve efficiency, enhance contamination resistance, and increase accessibility of oil-water separation technologies.