Rational design and application of superhydrophobic fluorine-free coating based on double-decker silsesquioxane for oil-water separation

A superhydrophobic coating of methoxysilane-functionalized double-decker silsesquioxane (M-DDSQ) on cotton fabric was synthesized using the dip-coating method. Characterizations using FT-IR, XPS, SEM, and AFM demonstrated that M-DDSQ-fabric has chemically covalently grafted M-DDSQ on the fabric surface and exhibits excellent chemical stability and antifouling properties compared to the pristine fabric. Interestingly, the novel fluorine-free fabric has a superhydrophobicity property with a water contact angle (WCA) of 150°, which efficiently and quickly separates oil from water. The maximum flux reaches 88420 L m-2 h-1, and the separation efficiency is greater than 99%. Furthermore, its outstanding superhydrophobic durability against tape-peeling, abrasion, and chemicals such as strong acidic and alkaline solutions is attributed to the strong chemical bonding between M-DDSQ and the fabric surface. This simple and efficient method enables the preparation of a durable superhydrophobic fluorine-free coating, which can be applied to synthesize other superhydrophobic materials for self-cleaning, especially for oil-water separation applications.