Nacre-Inspired Chitosan/CaCO₃ Films with High Transparency and Underwater Superoleophobic Property for Efficient Oil/Water Separation

Numerous natural architectures achieve multifunctionality through mild formation processes. Natural nacre is composed of about 90 wt % calcium carbonate aragonite flakes and 5 wt % chitin, exhibiting excellent mechanical properties, optical transmittance, and underwater superoleophobicity. In this work, a nacre-inspired biomineralized film with high transparency and mechanically robust underwater superoleophobicity was synthesized through Mg²⁺-PAA coordinated regulation under ambient conditions. The nacre-inspired film has light transmittance (exceeding 80%), hardness (1.71 ± 0.08 GPa), Young's modulus (40.9 ± 0.3 GPa), and contact angle of underwater-oil droplets (151.2° ± 1.8°) comparable to natural nacre. Notably, this substrate-independent material can be directly mineralized on diverse surfaces, including plastics, glass, and polymer meshes, while maintaining efficient oil-water separation capability. By deconstructing the multiscale structure of biomaterials, this study establishes a novel paradigm for fabricating multifunctional composites through environmentally benign processes.