Guided electron flow in anthraquinone-methoxy donor-acceptor1-acceptor2 covalent triazine frameworks enabling superior selective uranium capture.

Rational design and synthesis of stable and efficient photocatalysts for selective U(VI) capture in water remains a great challenge due to the complicated water environment. Herein, considering the synergistic interaction between anthraquinone (-AQ, electron acceptor) and methoxy (-OCH3, electron donor), a series of ternary donor-acceptor-acceptor (D-A1-A2) covalent triazine frameworks named as OCH3(x)-AQ(y) (x and y represent different content ratios) were rationally designed and synthesized via molecular regulation. This work not only constructed a directional charge-transfer pathway, but also greatly improved the utilization efficiency of photogenerated electrons in OCH3(x)-AQ(y) framework, which was also further verified by density functional theory (DFT) calculations. Finally, OCH3(2)-AQ(3) could reach nearly 100% removal efficiency of U(VI) within 240 min under visible light irradiation in air. Meanwhile, OCH3(2)-AQ(3) showed an extremely high distribution coefficient (Kd, 1.07 × 106 mL·g-1) for U(VI) under multicomponent ion competition and further performed high removal efficiencies (>98%) in real water environments, such as seawater and groundwater. Importantly, the machine learning results also demonstrated that the structural characteristics would greatly influence the catalytic performance of CTF catalysts. The component tuning of donor-acceptor groups achieved synergistic effects in stepwise charge transport and target-selective site accessibility, which offered an effective photocatalytic strategy for U(VI) extraction in complex water environment.