Construction of UiO-66-NH2/g-C3N4 heterojunction for enhanced photocatalytic reduction of U(VI) under visible light

Effectively isolating uranium from aqueous solutions is crucial for the sustainable development of the nuclear industry and for ensuring environmental safety. In this study, a series of heterostructured composite photocatalysts (UON/CN) were synthesized using a straightforward solvothermal method. These composites, consisting of UiO-66-NH₂ (UON) and g-C₃N₄ (CN), were designed to reduce U(VI) under illuminated conditions. Among all synthesized composite materials, the UON/CN-20 variant demonstrated optimal photocatalytic performance, achieving a U(VI) separation ratio of 97.4 % after 1.5 h of visible light exposure, with an apparent rate constant of 2.97 h⁻¹ in the presence of ascorbic acid (AA) as a sacrificial agent. Furthermore, the UON/CN-20 composite exhibited excellent reusability and stability, maintaining a U(VI) separation ratio greater than 90 % even after five cycles. The superior photocatalytic performance observed in the UON/CN-20 composite can be primarily attributed to two key factors: (i) The incorporation of CN significantly enhanced the light absorption capacity of UON while effectively separating electron-hole pairs generated by light induction and providing active sites for oxidation reaction of water, (ii) The amino groups present in UON acted as efficient binding sites for U(VI) reduction, thereby promoting adsorption capacity and further lowering the reduction potential required for U(VI). This study presented an effective UiO-66-based photocatalyst, distinguished by its remarkable stability and outstanding photocatalytic activity, making it well-suited for applications in environmental remediation.