MOF-modified C3N4 for efficient photo-induced removal of uranium under air without sacrificial agents†

Abstract

Photocatalytic reduction of uranium from U(VI) to U(IV) is an effective method to remove uranium from wastewater, while it often requires anaerobic conditions and/or the addition of sacrificial agents, which hinders its further application. Herein, a MOF-modified C₃N₄ composite material was prepared for uranium removal under air atmosphere without the addition of sacrificial agents, achieving a notable uranium removal capacity of 1355 mg g⁻¹. The introduction of the MOF enhanced the band structure and the photoelectric properties of C₃N₄, making it able to generate and separate electrons and holes efficiently. The electrons were applied to reduce O₂ to form H₂O₂ and the holes could oxidize H₂O to O₂. The generated H₂O₂ could react with UO₂²⁺ to form (UO₂)O₂·2H₂O to realize the solidification of uranium under both air and N₂ atmospheres. This work may give a new direction to the design of photocatalysts for highly efficient uranium removal under air atmosphere without sacrificial agents.