Fe₃O₄ Magnetic Cores Coated with Metal–Organic Framework Shells as Collectable Composite Nanoparticle Vehicles for Sustained Release of the Pesticide Imidacloprid

A magnetic metal–organic framework nanocomposite as a collectable pesticide delivery vehicle was developed through the incorporation of UiO-66 with polydopamine-coated Fe₃O₄ (Fe₃O₄@PDA@UiO-66). The obtained Fe₃O₄@PDA@UiO-66 nanocomposite was verified by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and zeta potential test. The magnetic collectability of Fe₃O₄@PDA@UiO-66 was demonstrated through a magnetic hysteresis loop study (∼2 emu/g) and magnetic collection experiment (up to a 96% collection rate). Imidacloprid (IMI) was employed as a model pesticide to be loaded into the Fe₃O₄@PDA@UiO-66 nanocomposite, with 15.87% drug loading. IMI was found to exhibit sustained-release behavior after being loaded into the delivery vehicle, and magnetic Fe₃O₄@PDA@UiO-66 can be readily collected after IMI release, which is beneficial to constrain the hazardous effects of the vehicles and the residual pesticide on the ecosystem. The insecticidal activity of IMI@Fe₃O₄@PDA@UiO-66 toward Aphis craccivora Koch was found to be superior to that of free IMI, and the efficacy was comparable to that of the commercial 70% IMI water dispersible granule, indicating its potential as a magnetic collectable green carrier for pesticides in agriculture.