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

Abstract

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. This work demonstrates that molecularly designed COF spacers enhance charge transport and oxygen activation, enabling efficient reactive oxygen species generation and rapid micropollutant removal from water.