Fenton reaction-driven pro-oxidant synergy of ascorbic acid and iron oxide nanoparticles in MIL-88B(Fe)

Abstract

MIL-88B, a promising Fe-based 3D porous metal–organic framework (MOF) catalyst for the Fenton reaction, requires modifications to enhance its pro-oxidant activity and enable magnetic control of the sample. This study reports the successful modification of MIL-88B with iron oxide (Fe₃O₄) and ascorbic acid (AA). The characterization of the crystal structure and morphology of the Fe₃O₄–AA MOF sample using X-ray diffraction, Raman and Mössbauer spectroscopy, and scanning electron microscopy revealed that AA facilitated the formation of magnetite with a composition approaching a stoichiometry of Fe_2.96O₄ while preserving the MOF structure. Specifically, in the presence of hydrogen peroxide (H₂O₂), Fe₃O₄–AA–MOF exhibited a 3-fold increase in the Fenton reaction rate for methylene blue degradation compared to the conventional homogeneous system at pH 4.5. Furthermore, Fe₃O₄–AA–MOF retained the antibacterial properties of AA, as evidenced by its ability to increase reactive oxygen species in luminescent marine bacterium Photobacterium phosphoreum at low concentrations while exhibiting moderate cytotoxicity. The enhanced pro-oxidant activity of the Fe₃O₄–AA–MOF/H₂O₂ system is attributed to an AA-promoted surface Fe²⁺/Fe³⁺ cycle. A possible mechanism for this system is proposed.