Responsive slippery membrane with high efficiency in oil-water separation and mechano-bactericidal performances

Abstract

Fabrication of hydrophilic-oleophobic responsive membranes is greatly vital to satisfy the requirements of oil-water separation devices and oil droplet manipulation yet remains challenging due to the limitations imposed by surface tension theory. Herein, a seed-assisted in situ growth approach was employed to fabricate a hierarchical Zeolitic Imidazolate Framework-L (ZIF-L) layer, upon which a sodium perfluorooctanoate (PFOA-Na) solution was applied on the ZIF-L surface, thereby obtaining a highly responsive hydrophilic-oleophobic membrane (ZIF-L-F). The ZIF-L-F membrane possesses ultra-slippery properties with water as a natural lubricant, finally displaying a remarkably high oily liquid repellency with an extremely low contact angle hysteresis (CAH <3°), due to the instantaneous molecular structure reversal of the embedded PFOA-Na. Benefiting from its selective wettability towards water and oil, the ZIF-L-F can be easily applied to stainless steel mesh to get an oil-water separation membrane with high efficiency above 97 %. Also, this ZIF-L-F membrane exhibited excellent antibacterial activities (≥98 %) against gram-negative bacteria, due to its mechano-bactericidal activity of the ZIF-L nano-blade structures. These findings support the development of functional membranes that can highly maintain oil-water separation while effectively avoiding bacterial contamination in environmental protection and water treatment applications.