Gating hole back-transfer with molecular spacers programs rapid micropollutant decontamination.

Precise control of oxygen activation to generate reactive oxygen species (ROS) for on-demand micropollutant removal remains challenging. Herein, we develop a bottom-up molecular approach to systematically tailor dithienyl spacers (alkene/alkyl/benzene), from model fragments, amorphous polymers to high crystalline covalent-organic frameworks (COFs). We observe that the ordered assembly of benzene-bridged bithiophene units facilitates long-range electron transport, thereby suppressing the spatial recombination of photogenerated electron-hole pairs. These effects synergically reduce the oxygen adsorption barrier, efficiently generating superoxide radicals as the dominant ROS, with subsequent singlet-oxygen formation. Therefore, the removal of acetaminophen in water via the optimized Tapt-BDD COF catalyst achieves a reaction rate constant of 0.80 min-1. The degradation rates are enhanced by 63-95 fold over fragments (local repeating unit structure of the COF) and 5-8 fold over polymers (disordered COFs). Additionally, the proposed system demonstrates efficient retention in complex wastewater treatment scenarios, and under continuous operation. This work establishes a strategy of spacer-directed supermolecule preorganization for environmental catalysis.