Zn (II)-Ln (III) bimetallic MOF/polyurethane coatings for sustained antifouling: Synergistic antifoulant co-release enabled by controlled MOF degradation

The development of marine antifouling coatings that are both highly effective and environmentally sustainable presents a persistent challenge, impeding their widespread commercial application. To address this challenge, we developed sustained-release composite coatings by incorporating Zn (II)-Ln (III) bimetallic metal-organic frameworks (MOFs) into a polyurethane (PU) matrix. Four MOF variants (i.e., H₂FDA@Gd, H₂FDA@Ce, H₂OBA@Gd, and H₂OBA@Ce) were solvothermally synthesized using antifouling ligands (H₂FDA/H₂OBA) with Zn 2+ /Gd 3+ /Ce 3+ nodes, which were used as a filler for polyurethane resin, featuring bcu-topology frameworks and bidentate bridging coordination. These MOFs, which are composed of antifoulants, can degrade gradually in seawater. Therefore, the coatings demonstrated multifunctional antifouling performance, achieving 86% - 92.5% adhesion reduction against E. coli and S. aureus , as well as 75.5% against P. tricornutum , in addition to sustained lanthanide ion release and enhanced corrosion resistance. MOFs extend the path of the corrosive medium, exhibiting excellent anti-corrosion performance of the composite coatings. Field testing confirmed near-complete resistance to SRB corrosion and a maximum reduction in corrosion area of 76.28%. This work establishes an eco-friendly strategy through controlled MOF degradation that concurrently releases bioactive ligands and metal ions, enabling long-term marine protection with minimal environmental impact.