Fluorine-free superhydrophobic multi-functional robust coating

Although multifunctional superhydrophobic surfaces exhibit broad application prospects, their practical application is constrained by complicated preparation, environmental pollution, demanding equipment requirements, and poor durability. Herein, we developed a fluorine-free, ultrarobust superhydrophobic coating comprising zeolitic imidazolate framework-71 (ZIF-71)-assembled CaCO 3 microspheres and an epoxy/polydimethylsiloxane dual-network resin. This coating could be applied to various substrates, exhibiting a water contact angle of 154.5° ± 0.8° and water sliding angle of 5.4° ± 0.5°. It retained its superhydrophobic properties after severe mechanical stresses, such as those from tape peeling (300 cycles), sandpaper abrasion (12 m), high-velocity water jetting (42 L), and quartz sand impact (4.0 kg). This exceptional durability was attributed to the stable hierarchical microscale/nanoscale structure formed by ZIF-71 nanoparticles on the surface of CaCO 3 microspheres and enhanced interfacial adhesion due to the interconnected pore structure of the microspheres. Additionally, the coating exhibited strong resistance to harsh corrosive environments (pH 1–14, 3.5 wt% NaCl, and saturated NaCl solutions) as well as self-cleaning properties, which effectively prevented dirt accumulation. Electrochemical impedance spectroscopy in a 3.5 wt% NaCl solution confirmed the superior durability of the composite coating, showing an impedance modulus of 1.02 × 10 10  Ω·cm 2 . Icing delay and cyclic freeze–thaw tests confirmed that the coating could considerably delay ice nucleation by up to 458 s and maintain hydrophobicity after 25 freeze–thaw cycles.