Construction of 3DOM TiO2/CuO S-scheme heterostructures with tuned oxygen vacancies for high-performance photocatalytic U(VI) sequestration from wastewater

3DOM-TiO 2 /CuO S-scheme heterojunction synthesized via hard templating • Removes 99.06% U(VI) in 120 min; capacity of 1751.33 mg/g • Dynamic Cu valence change & O-vacancy evolution restrain charge recombination. • In situ multi-spectra & DFT reveal charge transfer and U(VI) reduction mechanism. Photocatalysis offers a sustainable approach for uranium-containing wastewater remediation, yet conventional materials still suffer from limited solar-light utilization and rapid charge recombination. Herein, a three-dimensional ordered macroporous TiO 2 /CuO composite (3DOM-TC) was synthesized using resorcinol–formaldehyde resin spheres as a hard template. The ordered macroporous TiO 2 framework enables slow-photon-assisted light harvesting and multiple light scattering, while CuO coupling broadens the light-response range and constructs an S-scheme TiO 2 /CuO heterojunction to promote directional charge separation. Meanwhile, oxygen vacancies mainly serve as electron-trapping and O 2 /intermediate adsorption–activation sites, which are coupled with the dynamic Cu 2+ /Cu + variation during photocatalysis. As a result, 3DOM-TC achieves 99.06% U(VI) removal within 120 min, corresponding to a maximum extraction capacity of 1751.33 mg/g. Photoelectrochemical tests confirm enhanced photocurrent density and efficient interfacial charge transport compared with pristine TiO 2 . In situ EPR, XPS, and DFT calculations reveal the photoinduced charge-transfer pathway and illumination-enhanced oxygen-vacancy signals. Moreover, in situ FTIR spectroscopy confirms that photogenerated ·O 2 − can further convert to H 2 O 2 -related species, thereby promoting U(VI) precipitation as (UO 2 )O 2 ·4H 2 O. This work highlights the synergistic integration of 3DOM-enabled light harvesting, S-scheme charge separation, and vacancy-assisted electron transfer and O 2 activation, providing a promising strategy for efficient photocatalytic U(VI) sequestration. Download: Download high-res image (232KB) Download: Download full-size image