Stimuli-responsive composite coating based on dynamic metal-ligand interactions for sustainable marine antifouling

While copper-based antifoulants represent effective solutions for marine biofouling prevention, their utilization efficiency remains a critical challenge. This investigation demonstrates a pH-responsive hydrogel composite through synergistic integration of poly(acrylic acid) networks with histidine-coordinated cupric nanoclusters. The main ligand configuration of histidine and Cu²⁺ was identified as “imidazole-dominated and carboxyl-assisted” by density functional theory (DFT) simulation, which provides theoretical support for the pH sensitivity of hydrogel. This coating releases Cu²⁺ precisely “on demand” in response to external pH changes, effectively preventing algae and fouling organisms from adhering and achieving high bactericidal rates against Pseudomonas aeruginosa and E. coli. The distinctive molecular design of the coating combines multiple amide motifs that self-assemble into a honeycomb network via strong hydrogen bonding, while the coordination between Cu²⁺ and histidine establishes a dynamic metal-ligand interaction with tunable dissociation kinetics and cohesion strength. This intelligent controlled-release composite hydrogel significantly reduces the risk of marine fouling by releasing antifouling agents precisely and efficiently, providing an innovative solution for building a sustainable marine antifouling system.