Engineering charge transfer channels in D–π–A structured multicomponent COFs for efficient photocatalytic uranium extraction coupled with organic degradation

Abstract

Photocatalysis provides a promising way to simultaneously extract uranium and degrade organics in uranium-bearing water through the in situ-generated reactive oxygen species (ROS). However, conventional donor–acceptor covalent organic frameworks (D–A COFs) are hampered by inefficient charge separation and sluggish interfacial transfer. Here, a multi-component COF (MC-COF) was designed and prepared with a donor–π–acceptor (D–π–A) structure and a cyano-bearing π-bridge (named MC-COF-Db), which could effectively modulate the visible light harvesting and inhibit charge recombination. Impressively, MC-COF-Db achieved a uranium extraction efficiency of over 90%, while concurrently degrading tetracycline, ciprofloxacin, bisphenol A and sulfamethoxazole with efficiency exceeding 96%. Experimental and theoretical data reveal that the cyano site provides an additional charge transfer pathway, promoting exciton dissociation/transfer and boosting the generation of ˙O₂⁻ and H₂O₂. The in situ-generated ROS could simultaneously transform dissolved uranyl ions to metastudtite solids and degrade organic pollutants. This work underscores the pivotal role of π-bridge design in unlocking the full photocatalytic potential of COFs for coupled uranium recovery and water remediation.