MOFs自牺牲模板法制备CoNx/g-C3N4纳米材料用作高效光催化还原U(VI)

近年来, 利用石墨氮化碳(g-C₃N₄)光催化法将易溶的U(VI)还原为难溶的U(IV)来清除铀, 已逐渐成为放射性核素研究的热点。本研究将一种含金属钴的金属有机框架材料(MOFs)作为自牺牲模板, 利用简单热共聚法成功合成了含有Co-N_x构型的CoN_x/g-C₃N₄催化剂。在固液比为1.0 g/L、pH 5.0、可见光照射45 min下, 制备的催化剂(w(Co-MOFs) : w(g-C₃N₄)=1 : 1)对50 mg/L的U(VI)标准溶液还原率达到100%。从形貌, 微观结构和光学性能等方面对催化剂进行了表征,结果显示, 引入Co有效拓宽了g-C₃N₄对可见光的吸收范围, 抑制了光生电子与空穴的复合, 从而促进了U(VI)的还原反应。此外, 基于捕获实验深入探究了U(VI)在CoN_x/g-C₃N₄材料表面催化可能的反应机理。研究表明, CoN_x/g-C₃N₄复合光催化剂光学性能优异, 制备方法简单且绿色环保, 对放射性废水中的U(VI)的光催化还原去除效果较好。本工作对后续石墨氮化碳类新型材料的设计、合成与实际应用具有一定的参考作用。

CoNx/g-C3N4 Nanomaterials Preparation by MOFs Self-sacrificing Template Method for Efficient Photocatalytic Reduction of U(VI)

Broad application of nuclear energy has resulted in the release of radionuclides such as uranium U(VI)], into the environment, and its potential toxic and irreversible effects on the environment are among the paramount issues in nuclear energy use. Graphite carbon nitride (g-C₃N₄) is a kind of non-metallic material with the triazine structure. In recent years, the reduction of U(VI) to insoluble U(IV) by g-C₃N₄ photocatalysis has become a major research focus on the area of radioactive pollutants. In this work, a metal-organic framework (MOF) material containing cobalt metal was used as a self-sacrificial template. Through simple thermal copolymerization, the Co-N_x coordination was successfully incorporated into g-C₃N₄ to synthesize the CoN_x/g-C₃N₄ photocatalyst. The effects of the morphology, structure, and photoelectric properties of CoN_x/g-C₃N₄ on the photocatalytic reduction of U(VI) were investigated using macroscopic batch experiments. The results showed that the introduction of Co effectively broadened the absorption range of g-C₃N₄ to visible light, inhibited recombination of the photogenerated electrons and holes, and facilitated the reduction of U(VI). Under irradiation in visible light for 45 min, pH 5.0 and solid-liquid ratio of 1.0 g/L, the photocatalytic reduction of a standard 50 mg/L U(VI) solution reached 100% by CoN_x/g-C₃N₄(w(Co-MOFs) : w(g-C₃N₄)=1 : 1). Furthermore, the photocatalytic mechanism of CoN_x/g-C₃N₄ was investigated through capture experiments. In summary, the CoN_x/g-C₃N₄ composite exhibits excellent optical performance, has simple operation, is eco-friendly, and has a significant photocatalytic effect on U(VI) in radioactive wastewater. This work also provides design strategy and technical reference for applying g-C₃N₄ materials to treat radioactive wastewater.