Recently, metal–organic frameworks (MOFs) have become a dazzling star among porous materials used in many fields. Considering their intriguing features, MOFs have great prospects for application in the field of sustainable agriculture, especially as versatile pesticide-delivery vehicles. However, the study of MOF-based platforms for controlled pesticide release has just begun. Controlled pesticide release responsive to environmental stimuli is highly desirable for decreased agrochemical input, improved control efficacy and diminished adverse effects. In this work, simple, octahedral, iron-based MOFs (NH₂-Fe-MIL-101) were synthesized through a microwave-assisted solvothermal method using Fe³⁺ as the node and 2-aminoterephthalic acid as the organic ligand. Diniconazole (Dini), as a model fungicide, was loaded into NH₂-Fe-MIL-101 to afford Dini@NH₂-Fe-MIL-101 with a satisfactory loading content of 28.1%. The subsequent polydopamine (PDA) modification could endow Dini with pH-sensitive release patterns. The release of Dini from PDA@Dini@NH₂-Fe-MIL-101 was much faster in an acidic medium compared to that in neutral and basic media. Moreover, Dini@NH₂-Fe-MIL-101 and PDA@Dini@NH₂-Fe-MIL-101 displayed good bioactivities against the pathogenic fungus causing wheat head scab (Fusarium graminearum). This research sought to reveal the feasibility of versatile MOFs as a pesticide-delivery platform in sustainable crop protection.

Environmental stimuli-responsive pesticide release is desirable for enhanced efficiency and reduced side effects. In most cases, the loading and release of pesticides mainly depends on hydrophobic interactions and hydrogen bonding. Electrostatic interaction is less investigated as a weapon for achieving high loading content and controlled pesticide release. In this work, negative-charge decorated mesoporous silica nanoparticles (MSNs) were facilely fabricated by introducing sulfonate groups onto MSNs through a post-grafting method. Sulfonate-functionalized MSNs (MSN-SO₃) were synthesized by conversion of epoxy group into sulfonate group using a bisulfite ion as a ring opening reagent. Diquat dibromide (DQ), one of the globally used quaternary ammonium herbicides, was efficiently loaded into these negatively charged MSN-SO₃ nanoparticles. The loading content was increased to 12.73% compared to those using bare MSNs as carriers (5.31%). The release of DQ from DQ@MSN-SO₃ nanoparticles was pH and ionic strength responsive, which was chiefly governed by the electrostatic interactions. Moreover, DQ@MSN-SO₃ nanoparticles exhibited good herbicidal activity for the control of Datura stramonium L., and the bioactivity was affected by the ionic strength of the release medium. The strategy of cargo loading and release dependent on the electrostatic interactions could be generally used for charge-carrying pesticides using carriers possessing opposite charges to mitigate the potential negative impacts on the environment.