Breaking the Exciton Bottleneck in 1D COFs via Tailored Active‐Sites Microenvironment Enables High‐Capacity Uranium Photocatalytic

Abstract Whereas 2D COFs limit the exposure of active sites, the distinctive double‐chain structure of 1D COFs facilitates full exposure of catalytic active sites, leading to enhanced photocatalytic activity. However, their large inherent exciton binding energy ( E b ) limits photocatalytic application. Herein, precise control over E b of 1D COFs is achieved by engineering electron‐donating pendant groups (‐OH, ‐CH 3 , ‐Cl) on C 2 linkers while maintaining 4‐c sql topology. The hydroxyl‐functionalized TD‐COF demonstrates an exceptionally low E b of 86.8 meV, enabling superior visible‐light activity and outstanding U(VI) removal capacity (1312.7 mg g −1 ). This 1D architecture simultaneously enables directional charge transport and exposes triazine ring active sites. Electron‐rich N atoms within these sites selectively coordinate uranyl ions and drive U(VI)‐to‐U(IV) conversion. Systematic characterization and density functional theory (DFT) calculations reveal that ‐OH pendant groups simultaneously enhance hydrophilicity, charge mobility, and exciton dissociation efficiency, thus enhancing the photocatalytic activity. Notably, this is the first report on the application of 1D COFs in the treatment of uranium containing wastewater. This work establishes microenvironment engineering as a powerful strategy for optimizing COF photocatalysts, providing atomic‐level insights into structure‐performance relationships for nuclear wastewater treatment and sustainable uranium recovery.