The decline of fossil fuels is fostering research on carbon–neutral fuels such as nuclear energy, yet uranium supply is limited by actual techniques of uranium extraction from seawater. In particular, biofouling by marine bacteria and adsorbent instability are major drawbacks. Here we synthesized a novel amidoxime-functionalized antibacterial covalent organic framework that displays high stability and inhibits more than 90% the growth of marine bacteria, thus resulting in an enhanced uranium recovery capacity of 6.64 mg/g. Meanwhile, due to its exceptional fluorescence properties, the adsorbent can also be applied to highly sensitive on-site and real-time monitoring of UO22+.