Double layer MOFs M-ZIF-8@ZIF-67: The adsorption capacity and removal mechanism of fipronil and its metabolites from environmental water and cucumber samples

In this study, a novel metal-organic framework (M-ZIF-8@ZIF-67) was successfully prepared using the single layer Fe3O4-ZIF-8 as magnetic core and wrapped a layer of ZIF-67 outer. This M-ZIF-8@ZIF-67 was employed as an adsorbent for the adsorption and removal of fipronil and its metabolites from environmental water and cucumber samples. The characterization results suggested that M-ZIF-8@ZIF-67 has the double layer structure a polyhedral structure with uniform pores, while ZIF-67 was successfully coated on the surface of Fe3O4-ZIF-8. The unique structure endowed M-ZIF-8@ZIF-67 a high surface area (219 m2 /g) and high adsorption capacity for fipronil, fipronil desulfinyl, fipronil sulfide and fipronil sulfone. To our knowledge, this is the first report detailing the adsorption properties of M-ZIF-8@ZIF-67 with double layer structure relating to the adsorption and removal of pesticides. Furthermore, the adsorption model analysis demonstrated that the static adsorption data fitted the Freundlich bimolecular layer adsorption model better than the Langmuir monolayer adsorption model. This study indicates that M-ZIF-8@ZIF-67 has significant potential in the adsorption and removal of fipronil and its metabolites in water and vegetable samples.