Metal single-atom coordination to manipulate photogenerated electron transfer pathway of imine-based COFs for highly efficient persulfate activation on thiamethoxam degradation

Herein, we proposed a strategy to activate persulfate (PMS) for thiamethoxam (THI) photodegradation by metal single-atom coordination COFs, forming Fe@RTCOF-1Acb with a wider spectral absorption range and enhanced electron separation & transfer capability. The periodic it-it conjugated structure of RTCOF-1Acb with imine bonds provided many sites for the anchoring of Fe atoms. DFT calculations showed that the Fe single atom acted as an electron acceptor mediator connecting the benzene ring of RTCOF-1Acb to construct a channel for fast charge transfer. Based on molecular docking and genetic algorithm results, Fe@RTCOF-1Acb was maintained with THI through hydrophobic and it-related forces. Benefiting from the strong oxidation of center dot O2-, h+, SO4 center dot- and center dot OH, the synergistic degradation efficiency of THI by the "Fe@RTCOF-1Acb + PMS" system reached 93.09 %. In addition, Fe@RTCOF-1Acb had remarkable recyclability and was suitable for the degradation of THI in field water, river water, domestic wastewater, and laboratory wastewater. Based on the reaction pathway of HSO5- -*SO4 center dot--*SO42--*center dot OH, THI was decomposed into 19 intermediates by demethylation, nitro reduction, oxadiazine ring rupture, and ring opening. With the help of quantitative structure-activity relationship (QSAR), Fe@RTCOF-1Acb was effective for photocatalytic activation of PMS to remove the acute toxicity of THI. This work revealed the promising application of metal single-atom anchored COFs in the treatment and remediation of pesticide wastewater.