ZIF-8-modified MnFe2O4 with high crystallinity and superior photo-Fenton catalytic activity by Zn-O-Fe structure for TC degradation

In this work, a novel Zeolite imidazole framework-8-modified MnFe2O4 magnetic catalyst was successfully synthesized by one step method. The 10% ZIF-8/MnFe2O4 exhibited superior photo-Fenton catalytic performance in TC degradation at a wider pH range (pH = 3-11). The excellent photo-Fenton catalytic effects were possibly attributed to the formation of Zn-O-Fe structure by ZIF-8-modified MnFe2O4, which could increase the absorption of visible light, promote the formation of crystal structure, and facilitate the generation and separation of photo-induced carrier. The existence of Zn-O-Fe structure formed by the occupation of Zn in ZIF-8 of tetrahedral sites in spinel structure was determined by X-ray diffraction (XRD). Meanwhile, the UV-vis diffuse reflectance spectrophotometer (UV-vis DRS), photocurrent and impedance characterization confirmed that the Zn-O-Fe structure could promote the separation of charge carriers. The possible two mechanisms were proposed and the Zn-O-Fe structure played different roles in different mechanism. In mechanism I, the Zn-O-Fe structure transfers of electrons from MnFe2O4 to ZIF-8. In mechanism II, the Zn-O-Fe structure can generate photo-electron and holes under visible light irradiation and transfer of electrons from ZIF-8 to MnFe2O4. This work is expected to provide valuable information for the design and synthesis of metal-organic framework modified spinel bimetallic oxides in heterogeneous photo-Fenton reactions.