Synergistic generation of ROS via covalent organic frameworks with excellent energy transfer and charge transfer characteristics for phenolic pollutants treatment

Charge transfer (C.T) and energy transfer (E.T) are the two modes of reactive oxygen species (ROS) generation in photocatalytic advanced oxidation processes (PAOPs). These ROS are essential for the completely mineralization of aromatic organics. Up to now, there are no photocatalysts that can perfectly achieve efficient ROS generation through the synergistic of C.T and E.T. Hence, we enhance the adsorption and photocatalytic synergistic ability of the catalysts through site engineering strategy of quaternization and metal ions coordination on pyrene-based donor-acceptor type covalent organic framework. Among them, Co-PyBpy+-COF shows excellent removal of phenol at low concentration in wastewater within 30 min. Mechanistic studies reveal that the excellent carrier transport efficiency of Co-PyBpy+-COF promotes the generation of superoxide radicals (center dot O2- ), hydroxyl radicals (center dot OH), and hydrogen peroxide (H2O2) through C.T process. Simultaneous pyrene units with long-lived excited state ensure the continuous generation of singlet oxygen (1O2) via E.T process. Therefore, the aromatic organics in wastewater are effectively mineralized by ROS that are continuously generated under light irradiation. This study provides a reference for designing photocatalysts with strong oxidative ROS generated through the synergy of C.T and E.T process.