Nanoflower-like covalent organic framework/indium sulfide step scheme heterojunction for selective electrochemical...

The selective extraction of uranium from seawater is crucial for sustainable resource recovery and environmental protection, yet remains challenging due to severe interference from coexisting ions. Herein, we reported a step scheme (S-scheme) heterojunction, denoted as TD-COF@IS, based on a spherical Schiff-based covalent organic framework (TD-COF) and indium sulfide (In₂S₃), engineered to enable efficient electrochemical uranium capture. The heterostructure establishes an internal electric field that promotes directional charge transfer, enhances carrier separation, and increases the accessibility of redox-active sites. As a result, the optimized TD-COF@IS-2 electrode exhibited a high uranium uptake capacity (up to 778.8 mg g^-1) with pronounced selectivity under complex ionic conditions and stable cycling performance, while its effective and selective electrochemical uranium extraction was further validated in real seawater. Ex-situ characterizations combined with theoretical calculations elucidate both the interfacial electrosorption behavior of uranyl ions and the intrinsic mechanism of heterostructure-enhanced uranyl adsorption. This work demonstrates a viable strategy for designing heterojunction electrodes for selective ion capture and provides insights into interfacial charge engineering for electrochemical separations.