Constructing donor–acceptor covalent organic frameworks with bex topology for efficient photocatalytic reduction of uranium

Abstract

Effective elimination of uranium from wastewater is crucial for sustainable development in the nuclear industry. Extracting U(VI) by photocatalytic reduction using covalent organic frameworks (COFs) is regarded as an effective and environmentally friendly method. However, COFs with unconventional bex topology for photocatalytic uranium reduction remain largely unexplored. Herein, we synthesized three COFs that have distinct bex topologies, and their performance in the photocatalytic reduction of U(VI) was investigated. Among these COFs, Py-TAPT-COF, in which the triazine unit acts as an electron acceptor and the pyrene unit functions as an electron donor, showed excellent photocatalytic reduction capability, achieving 92.1% reduction of U(VI). Additionally, from a mixture containing 13 competing metal ions, Py-TAPT-COF demonstrated remarkable uranium extraction selectivity and retained 78.8% of its photocatalytic efficiency after four consecutive cycles. Density functional theory (DFT) calculations revealed that the triazine and pyrene units are active photocatalytic reaction sites, which significantly promote the separation of photoelectrons from vacancies.