Intercalated MOF nanocomposites: robust, fluorine-free and waterborne amphiphobic coatings

Transparent non-wetting surfaces with mechanical robustness are critical for applications such as contamination prevention, (anti-)condensation, anti-icing, anti-biofouling, etc. The surface treatments in these applications often use hazardous per- and polyfluoroalkyl substances (PFAS), which are bio-persistent or have compromised durability due to weak polymer/particle interfacial interactions. Hence, developing new approaches to synthesise non-fluorinated liquid-repellent coatings with attributes such as scalable fabrication, transparency, and mechanical durability is important. Here, we present a water-based spray formulation to fabricate non-fluorinated amphiphobic (repellent to both water and low surface tension liquids) coatings by combining polyurethane and porous metal-organic frameworks (MOFs) followed by post-functionalisation with flexible alkyl silanes. Owing to intercalation of polyurethane chains into MOF pores, akin to robust bicontinuous structures in nature, these coatings show excellent impact robustness, resisting high-speed water jets (∼35 m s^-1), and a very low ice adhesion strength of ≤30 kPa across multiple icing/de-icing cycles. These surfaces are also smooth and highly transparent, and exhibit excellent amphiphobicity towards a range of low surface tension liquids from water to alcohols and ketones. The multi-functionality, robustness and potential scalability of our approach make this formulation a good alternative to hazardous PFAS-based coatings or solid particle/polymer nanocomposites.