Fluorine‐Free <scp>POSS</scp> ‐Based Silane Coatings for Robust Superhydrophobic and Self‐Cleaning Cotton Fabrics With Efficient Oil–Water Separation Performance

ABSTRACT The widespread use of fluorinated silane coupling agents in hydrophobic textile coatings has raised increasing concerns due to their bioaccumulation and environmental persistence. In this study, a series of fluorine‐free, POSS‐based silane coupling agents were synthesized via hydrosilylation between octavinyl polyhedral oligomeric silsesquioxane (OV‐POSS) and two functional silanes—trimethoxyhydrosilane (MTMS) and bis(trimethylsiloxy)methylsilane (MDHM)—with tunable molar ratios. These hybrid silanes were applied to cotton fabric using a simple one‐step dip‐coating method. Among them, the POSS‐4MTMS‐4MDHM formulation, at a concentration of 0.2 wt%, imparted superhydrophobicity with a water contact angle (WCA) of 151° and a sliding angle (SA) of 8°. The modified fabric exhibited outstanding mechanical durability, maintaining a WCA of 147° after 100 abrasion cycles under 200 g loading, and retained excellent water repellency after ultrasonic washing and tape‐peeling tests. Furthermore, the coating demonstrated chemical resistance over a wide pH range, while preserving the inherent softness and improving the surface smoothness of the fabric. In oil–water separation tests, the coated fabric achieved a separation efficiency of 98.5% and an oil flux of 11.59 L m −2 s −1 , with efficiency remaining above 97% after 30 reuse cycles. This scalable, fluorine‐free strategy enables the fabrication of multifunctional, robust textile coatings with hydrophobic, antifouling, and separation properties.