Crisscross metal–organic frameworks superhydrophobic structure for high efficient emulsion separation and anti-icing

To address the limitations of current superhydrophobic materials for oil–water separation, such as the use of non-environmentally friendly raw materials, non-degradability and poor coating durability. This study presents the design of a superhydrophobic fabric that is robust, versatile, and free from fluorine. Inspired by the microstructure of lotus leaf mastoids, the zeolitic imidazolate framework nanoleaves (ZIF-L)/polymethyl methacrylate (PMMA)/polydimethylsiloxane (PDMS) superhydrophobic cotton fabric is prepared by introducing carboxyl groups onto the cotton fabric surface via a diazonium chemical method, followed by in-situ growth of crisscrossed metal–organic frameworks (MOF) structure ZIF-L, and subsequent modification with low surface energy substances PDMS. PMMA was bonded bind to the ZIF-L through hydrogen bonds and van der Waals forces, these interactions significantly improve the resistance to washing and abrasion. The ZIF-L/PMMA/PDMS superhydrophobic cotton fabric exhibits an exceptional water contact angle of 162.2° and a remarkably low sliding angle of only 5.6°. In assessments of durability, the constructed fabric displays exceptional durability, enduring 30 cycles of washing and abrasion without significant degradation of its superhydrophobic properties. It also demonstrates robust anti-fouling and self-cleaning characteristics, alongside outstanding oil–water separation efficiency of over 98 %, and a 95 % efficiency in water-in-oil emulsion separation, coupled with notable reusability. The ZIF-L/PMMA/PDMS superhydrophobic cotton fabric also exhibits superior anti-icing performance as water droplets formed an insulating air layer upon contact with the superhydrophobic surface, thereby reducing heat transfer. Its displays a low ice adhesion strength of 39 kPa at −25 °C, endured over 30 freeze–thaw cycle, and delayed ice formation for more than 120 s at −25 °C. The diminished adhesion strength as a result of the increase of air layer between the water and the superhydrophobic cotton, high surface roughness and PDMS modification, which minimizes ice adhesion.