Water-\nand Acid-Sensitive Cu<sub>2</sub>O@Cu-MOF Nano\nSustained-Release Capsules with Superior Antifouling Behaviors

Marine\nbiofouling is one of the technical bottlenecks restricting\nthe development of the global marine economy. Among the commercial\nself-polishing antifouling coatings, cuprous oxide is an irreplaceable\ncomponent because of its efficiency and broad-spectrum antibacterial\nactivity. However, one of the biggest obstacles to achieving long-term\nantifouling is the “initial burst and final decay” of\ncuprous oxide in the coating. Here, we lock the copper ions by establishing\nan antifouling unit composed of Cu₂O (core) and Cu-based\nmetal–organic framework (Cu-MOF, shell). Cu-MOF is densely\ngrown in situ on the periphery of Cu₂O by acid proton etching.\nThe shell structure of Cu-MOF can effectively improve the stability\nof the internal Cu₂O and thus achieve the stable and slow\nrelease of copper ions. Furthermore, Cu₂O@Cu-MOF nanocapsules\ncan also achieve active defense by rapid and complete dissolution\nof Cu₂O@Cu-MOF at local acidic microenvironment (pH ≤\n5) where the adhesion of fouling organisms occurs. Super-resolution\nfluorescence microscopy is used to explain the sterilization mechanism.\nRelying on the water- and acid-sensitive properties of Cu-MOF shell,\nthe stable, controlled and efficient release of copper ions has been\nachieved for the Cu₂O@Cu-MOF nanocapsules in the self-polishing\nantifouling coatings. Thus, these controlled-release nanocapsules\nmake long-term antifouling promising.