Water strider-inspired floating catalyst with CN/ laccase spatial segregation for efficient dye wastewater decontamination

Traditional photoenzymatic systems for dye wastewater face critical bottlenecks, including radical-induced enzyme inactivation, inadequate light/oxygen exposure, and cumbersome catalyst recovery. Herein, a biomimetic floating catalyst (EP-CN-LC) was prepared using porous natural expanded perlite (EP) as the buoyant scaffold. Graphitic carbon nitride (CN) was anchored at the air-water interface, and laccase (LC) was immobilized in the subaqueous region via adsorption-covalent grafting. Successful spatial segregation endows CN with enhanced visible-light absorption (band gap = 2.63 eV), and the porous structure of EP protects LC from radical-induced inactivation. Under optimal conditions (13 mg LC loading, pH 4, 50°C), EP-CN-LC achieved 86.3% Rhodamine B degradation efficiency, 1.25 times higher than pure CN. Radical trapping experiments identified photogenerated holes (h⁺) and superoxide radicals (•O₂⁻) as the dominant active species, with the spatial design confining reactive species to the interfacial region. The catalyst exhibits excellent pH and temperature adaptability. After direct recovery, EP-CN-LC retains a high degradation efficiency of 80.5% over 5 consecutive cycles, demonstrating outstanding reusability. Its inherent floating property enables direct and facile separation during recycling, eliminating cumbersome operations and reducing application costs. This biomimetic design synergistically integrates efficient dye degradation, effective protection of LC from radical damage, and convenient recyclability, providing a green and practical technical solution for refractory dye wastewater treatment.