Z-scheme H-PDI supermolecule/NH2-MIL-101(Fe) for enhanced malathion degradation: Mechanism, pathway, and toxicity assessment

Malathion (MA) is a widely used organophosphorus pesticide globally. Developing efficient photocatalysts is crucial for eliminating MA pollution in water by photocatalytic technology. This study focuses on preparing a series of H-PDI supermolecule/NH 2 -MIL-101(Fe) (PM) materials by amidating NH 2 -MIL-101(Fe) with the more stable H-PDI supermolecule, forming a covalent O C–NH bond. Among these materials, 40 %PM (indicating a mass percentage content of 40 % H-PDI supermolecule in PM) exhibited the best performance for degradation of MA. Under simulated sunlight irradiation of a 10 mg·L 1 MA solution for 180 min, the reaction rate constants of 40 %PM were 5.95 times and 3.13 times higher than those of NH 2 -MIL-101(Fe) and H-PDI supermolecule, respectively. The enhanced performance is attributed to the formation of Z-scheme heterojunctions in the 40 %PM composite lead to fast separation of photogenerated e − and h + . Combining the results of HPLC-MS with Fukui Function, the HOMO, LUMO, and pathway of degradation of MA attracted by 1 O 2 , •OH, and h + were speculated. The pathway involves oxidation, demethylation, P-S bond breakage, decarboxylation, and final conversion to some inorganic molecules. The toxicity of the degradation byproducts were lower than that of MA estimated by Toxicity Estimation Software Tool.