Weak localized electrons enhance electronic coherence for efficient photocatalytic uranium removal from nuclear wastewater.

Abstract

Photocatalytic uranium removal from nuclear wastewater is a promising strategy for radionuclide mitigation, yet its practical deployment is greatly hampered by inefficient charge separation of electron-hole pairs in photocatalytic systems, which critically limits the generation of reactive oxygen species essential for uranium precipitation. Herein, we propose a approach that leverages weakly localized electrons to enhance electronic coherence in fluorine-functionalized covalent organic frameworks, thereby strengthening charge separation and promoting directional electron transport for greatly boosting photocatalytic uranium removal from nuclear wastewater. We demonstrate that the partial fluorination in covalent organic frameworks induce weak electron localization and strong electronic coherence, which delivers a record-high solar-to-chemicals conversion efficiency of 1.52% and achieves 100% uranium removal efficiency within the pH range of 3-6, outperforming non-fluorinated (0.31%) and over-fluorinated (0.85%) counterparts. More importantly, a self-designed flow-type reactor achieves 99% uranium removal efficiency and superior U processing capacity of 281.3 g m^-2 day^-1 under natural sunlight, significantly surpassing reported photocatalytic systems and meeting World Health Organization discharge limits. Mechanism investigation reveal that the partial fluorination enhanced electronic coherence improves photogenerated carrier transport and reparation for accelerating reactive oxygen species synthesis, thereby promoting uranium removal from nuclear wastewater.