摘要
Benzothiazole/benzothiazole-based COFs exhibited pronounced stability and π-π conjugation. • The “dual-lock” structure of Tp-BTZ exhibited the π-electron delocalization effect. • The photoreduction rate of Tp-BTZ was 5.47 and 1.88 times that of Tb-DBD and Tp-DBD. • Photogenerated e - , •O 2 – , H 2 O 2 were the principal active species in U(VI) reduction. The intrinsic characteristics of covalent organic frameworks (COFs) have drawn considerable attention for uranium recovery applications. Herein, we constructed three robust and highly π-π conjugated COFs (Tb-DBD, Tp-DBD, Tp-BTZ) for photocatalytic U(VI) reduction. Where π-electron delocalization featured the extension of π-electron clouds within organic molecules, the incorporation of highly planar-conjugated benzoxazole and benzothiazole monomers into the backbone structure enabled efficient π-π stacking interactions, thereby introducing expanded π-electron clouds, facilitating charge transport and optimizing the photochemical performance of COFs. Research findings indicated that Tp-BTZ possessed an intramolecular ‘dual-locked’ structure, achieving ‘heteroatom locking’ via its benzothiazole ring and ‘hydrogen-bond locking’ through its β-ketoenamine bond, endowing it with abundant adsorption sites and in-plane π-electron delocalization effects. Specifically, the addition of 5 mg Tp-BTZ at pH 6.0 during the photocatalytic reaction for 210 min yielded the removal efficiency of U(VI) at 91.85%, and the reaction rate of 0.662 h −1 as fitted by pseudo-first-order kinetics, representing 5.47 and 1.88 times that of Tb-DBD and Tp-DBD respectively. Furthermore, compared to Tb-DBD and Tp-DBD, Tp-BTZ exhibited more pronounced O 2 activation properties, demonstrating highly efficient photocatalytic H 2 O 2 production and facilitating the deposition of U(VI) in the form of (UO 2 )O 2 ·2H 2 O onto the catalyst surface. Download: Download high-res image (194KB) Download: Download full-size image
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