Fish Scale-Inspired β-Cyclodextrin Cross-Linked Polyacrylamide Hydrogels for Oil–Water Separation

Cyclodextrins (CDs), a low-polysaccharide class, possess a hydrophilic outer surface due to their hydroxyl groups, which can be functionalized for various applications. In this study, the hydroxyl groups on β-cyclodextrin were functionalized with acrylates (CD-A) and were subsequently used as a cross-linker in the copolymerization with acrylamide to form a polyacrylamide-cyclodextrin hydrogel (PAC). Compared with polyacrylamide (PAM), PAC exhibited enhanced water absorption abilities and mechanical strength. Inspired by fish scales' surface structural properties, microporous stainless steel meshes were coated with PAC, and we could demonstrate an excellent oil-water separation due to excellent superhydrophilicity and underwater superoleophobicity. The mesh effectively separated various oil-water mixtures by using gravity filtration, achieving separation efficiencies of over 99%. Repeated use with different oil types confirmed the durability and effectiveness of the hydrogel-coated mesh for practical applications in oil-water separation.