In-situ growth of COF on BiOBr 2D material with excellent visible-light-responsive activity for U(VI) photocatalytic reduction

By integrating of adsorption and photoreduction for uranium(U), the covalent organic frameworks (COF, TpPa-1) and the heterostructure BiOBr@TpPa-1 were investigated. The results of electron spin resonance and photo electrochemical tests (UV-vis DRS, PL, EIS, I-t and Mott-Schottky plots) showed, TpPa-1 not only was provided with oxygen vacancies, which could act as inter-band level to enhance visible light capture and reduce the recombination of photogenerated carriers, but also possessed pi-electron conjugated structure, which could broaden the spectral absorption range and prolong the lifetime of photo-generated charges by surface hybridization. Consequently, the in-situ formation of TpPa-1 on BiOBr surface can significantly improve the photo catalytic performance of BiOBr for U(VI) reduction. Under visible-light irradiation, the superior photocatalytic performance of BiOBr@TpPa-1 generated reactive oxygen species and photoelectrons, which can efficiently reduce U(VI) pre-enriched in the framework of TpPa-1. Approximately 91% of U(VI) was photo-reduced within 540 min. Meanwhile, combined with surface analysis techniques (SEM, TEM, XRD and XPS) to reveal the mechanism of U(VI) photoreduction. Thus, the application of COFs as photocatalytic reductant was expanded, providing a sustainable alternative for visible-light-driven the conversion of high valent radionuclide ions in wastewater.

Automated summary

The study investigated the photocatalytic performance of covalent organic frameworks and heterostructure BiOBr@TpPa-1 for uranium, revealing TpPa-1's enhancements in visible light capture and carrier recombination reduction. BiOBr@TpPa-1 efficiently reduced pre-enriched U(VI) within a short time under visible light irradiation. The results suggest a sustainable alternative for visible-light-driven conversion of high valent radionuclide ions in wastewater.