Cyano-Functionalized Polyarylether-Based Covalent Organic Framework for Highly Efficient Photocatalytic Uranium Extraction

Uranium is the primary fuel for nuclear power. Extracting uranium from uranium-containing water bodies is of great strategic importance to solve the problems in the advance of nuclear energy. Photocatalytic uranium separation technology has the advantages of high uranium extraction efficiency and easy separation of products. It is of great significance to develop photocatalytic materials that can extract uranium effectively under visible light without sacrificial agents. In this work, polyarylether covalent organic frameworks containing different amounts of cyano groups were prepared, and the photocatalytic performance and mechanism of uranium extraction were studied. PAE-COF-DC exhibited superior uranium extraction efficiency under air and visible light conditions, and the uranium extraction efficiency in uranium-spiked seawater and groundwater was 80% and 93%, respectively. PAE-COF-DC also showed excellent reusable performance and anti-ion interference ability. The mechanism study demonstrated that, driven by visible light, PAE-COF-DC used superoxide radicals as important intermediates to efficiently generate hydrogen peroxide in situ through oxygen reduction reaction, which promoted the solidification of uranium in the form of metastudtite. This work provides insights into the design of highly efficient photocatalytic uranium extraction materials.