【摘要】 基于半导体光催化剂将可溶的六价铀(U(Ⅵ))还原为不可溶的四价铀(U(Ⅳ))是一种简便、环保、高效的铀提取方法.实现该技术的关键是开发在无牺牲剂情况下对于光催化还原铀具有高活性和稳定性的催化剂.本文报道了一种新型CdS/COF核壳结构光催化剂(CdS@COF-10),该催化剂具有高效的化学吸附、增强的载流子分离和抗光腐蚀能力,无需额外的牺牲剂即可用于高效的光催化还原铀.COF壳层不仅为U(Ⅵ)提供了化学吸附位点,降低了U(Ⅵ)还原的活化能,而且在与CdS核的界面处形成了内建电场,促进了载流子的分离.更重要的是,具有适当COF壳含量的CdS-COF-10在结晶度、界面接触完整性、CdS核的光吸收和U(Ⅵ)化学吸附位点数量之间取得了平衡,获得了最高的载流子分离效率和光催化还原铀性能.更多还原

【Abstract】 Reduction of soluble U（Ⅵ） to insoluble U（Ⅳ）based on semiconductor photocatalysts is a favored U（Ⅵ）-extraction method,because of its simplicity,environmental friendliness,and high efficiency.The key to implement this technology is the development of efficient photocatalysts with high activity and stability for sacrificial agents-free U（Ⅵ）photoreduction.Herein,we report a new type of CdS/covalent organic framework（COF） core-shell photocatalysts（CdS@COF-X,X=5,10,15,and 20） with efficient chemisorption,enhanced carrier separation,and antiphotocorrosion ability for U（Ⅵ） photoreduction without additional sacrificial agents.The two-dimensional COF,formed by the polycondensation of 2,4,6-triformylphloroglucinol and 1,3,5-tris（4-aminophenyl）triazine,was selected to construct the hybrid materials due to its high chemical stability,matching band gaps and efficient chemisorption for U（Ⅵ）.Remarkably,CdS@COF-10 realized a record high U（Ⅵ） extraction capacity of 1825.6 mg g^-1 after 90 min.Moreover,the reduction ratio of uranium was up to 82.5%,and the product was identified as uranium dioxide（UO₂） after reaction.Further mechanistic studies indicated that the COF shell not only provided chemisorption sites for U（Ⅵ） to decrease the activation energy of U（Ⅵ） reduction,but also formed a strong built-in electric field at the interface with the CdS core to promote the carrier separation.More importantly,for all CdS@COF-X,CdS-COF-10 with appropriate COF shell content balanced the crystallinity,interfacial contact integrity,light absorption of CdS core,and number of U（Ⅵ） chemisorption sites,achieving the highest carrier separation efficiency and U（Ⅵ） photoreduction performance.更多还原