Conjugated organic polymer enables external-sacrificial-agent-free photocatalytic uranium extraction with efficiency boosted by oxygen pre-activation

Abstract

Efficient extraction of uranium from seawater is critical for sustainable nuclear energy. Photocatalysis offers a promising route, while the reliance on sacrificial agents and the limited extraction capacity necessitate the development of new photocatalysts. Here, we report the first conjugated organic polymer (COP), BB-COP-AO, that enables external-sacrificial-agent-free photocatalytic uranium extraction from natural seawater. Rational incorporation of benzothiadiazole and pyridine units optimizes the band structure, enhances intramolecular donor–acceptor interactions, and facilitates charge separation, endowing it with high photocatalytic activity. Pyridine nitrogen atoms benefit dissolved oxygen adsorption and pre-activation to promote ·O₂⁻ generation, boosting the uranium recovery efficiency. Furthermore, the suitable valence band enables photogenerated holes to oxidize H₂O to H₂O₂, thereby eliminating the need for external sacrificial agents. Concurrently, amidoxime functionalities ensure selective uranyl binding. Consequently, BB-COP-AO drives selective conversion of the uranyl ions into highly stable metastudtite via a dual-pathway mechanism coupling dissolved oxygen activation and water oxidation. Benefiting from these synergistic effects, BB-COP-AO exhibits an outstanding uranium extraction capacity of 19.80 mg g⁻¹ in natural seawater within 7 d, along with excellent selectivity and recyclability. This work expands the application scope of COP-based materials and offers a generalizable molecular design strategy for developing multifunctional photocatalysts toward sustainable uranium recovery from seawater.