Sulfur doping-induced morphological and electronic structure modification of polyoxometalate FeWO for enhanced removal of organic pollutants from water.

Wolframite (FeWO), a typical polyoxometalate, serves as an auspicious candidate for heterogeneous catalysts, courtesy of its high chemical stability and electronic properties. However, the electron-deficient surface-active Fe species in FeWO are insufficient to cleave HO via Fe redox-mediated Fenton-like catalytic reaction. Herein, we doped Sulfur (S) atom into FeWO catalysts to refine the electronic structure of FeWO for HO activation and sulfamethoxazole (SMX) degradation. Furthermore, spin-state reconstruction on S-doped FeWO was found to effectively refine the electronic structure of Fe in the d orbital, thereby enhancing HO activation. S doping also accelerated electron transfer during the conversion of sulfur species, promoting the cycling of Fe(III) to Fe(II). Consequently, S-doped FeWO bolstered the Fenton-like reaction by nearly two orders of magnitude compared to FeWO. Significantly, the developed S-doped FeWO exhibited a remarkable removal efficiency of approximately 100% for SMX within 40 min in real water samples. This underscores its extensive pH adaptability, robust catalytic stability, and leaching resistance. The matrix effects of water constituents on the performance of S-doped FeWO were also investigated, and the results showed that a certain amount of Cl, SO, NO, HCO and PO exhibited negligible effects on the degradation of SMX. Theoretical calculations corroborate that the distinctive spin-state reconstruction of Fe center in S-doped FeWO is advantageous for HO decomposition. This discovery offers novel mechanistic insight into the enhanced catalytic activity of S doping in Fenton-like reactions and paves the way for expanding the application of FeWO in wastewater treatment.