Fluorine-free and self-repairing superhydrophobic polyimine/MOF composite coating on copper mesh for oil-water separation and photocatalytic degradation

Fluorine-free superhydrophobic coatings are environmental-friendly and have attracted great attention in the field of oil-water separation, yet their practical applications are limited by poor surface stability and the lack of self-repairing ability. Herein, a self-repairing and fluorine-free superhydrophobic polyimine/metal-organic framework (MOF) composite coating on copper mesh was prepared through in situ growth of MOF on etched copper mesh, followed by the formation of crosslinked polyimine layer with long alkyl chains. The obtained coating on copper mesh showed superhydrophobicity with a high water contact angle of 162° and a low water sliding angle of 4°. After heat treatment, sandpaper abrasion, tape peeling and immersion in different solvents and acid/alkali aqueous solutions, the coating still maintained superhydrophobic state. Interestingly, even if the coating was damaged by oxygen plasma and a knife, it was able to be self-repaired and recover superhydrophobicity after heating at 70 °C for 30 min, attributing to the reformation of dynamic imine bonds and the migration of long alkyl chains. The coated copper mesh exhibited not only excellent oil-water separation performance with a separation efficiency of 99.24 % and a permeation flux of 1.16 × 10⁵ L·m⁻²·h⁻¹ but also good photocatalytic degradation ability for organic dyes. The prepared fluorine-free and superhydrophobic coating on copper mesh has the characteristics of excellent surface stability, self-repairing ability and photocatalytic degradability, showing great application potential in oil spill accidents and industrial sewage emissions.