Cyano-enhanced covalent organic framework with β-ketoenamine linkage for efficient photocatalytic uranium extraction from seawater

COF-CN was synthesized for uranium photocatalysis reduction by a facile process. • Cyano group enhanced COF's uranium photocatalytic reduction. • DFT calculations indicated the significant local charge polarization in COF-CN. • COF-CN exhibited an extraction capacity of 11.5 mg/g in 7 days in natural seawater. • COF-CN reduced U(VI) to U(IV), which was re-oxidized to insoluble (UO 2 )O 2 ·2H 2 O. Photocatalytic uranium extraction from seawater represents an attractive strategy for supporting the sustainable development of nuclear energy while addressing environmental concerns. Covalent organic frameworks (COFs) are emerging photocatalysts for uranium extraction, but further improvements in their synthesis, stability, and photoelectronic properties are required. Herein, a cyano-enhanced COF photocatalyst (COF-CN) was successfully synthesized via β-ketoenamine linkage. The introduction of the cyano group as a strong electron acceptor improves photogenerated charge separation and coordination with uranyl ions, resulting in a 27.7% higher uranium extraction rate than its non-cyano counterpart. Benefiting from its outstanding photocatalysis, high selectivity, and antibacterial properties, COF-CN achieves a uranium extraction capacity of 11.5 mg/g in natural seawater over a one-week assay (12 h visible light/12 h dark cycle) without sacrificial agents, surpassing some currently reported photocatalysts. Moreover, the final photocatalytic product is identified as a highly stable uranium crystalline compound ((UO 2 )O 2 ·2H 2 O), which can be readily recycled without secondary environmental risks. This study presents a strategy that expands the rational design of COF-based photocatalysts, offering new insights for developing the ocean as a sustainable nuclear fuel source. Download: Download high-res image (297KB) Download: Download full-size image