Dual-coated photoresponsive metal-organic framework Microcarriers: Low-Toxicity paraquat delivery for efficient and sustainable weed control

Paraquat, an effective non-selective herbicide, has been widely utilized in agriculture, posing significant risks of human poisoning. In this study, paraquat is encapsulated within amino-functionalized metal-organic frameworks (UiO-66-NH 2 ), with cinnamic acid derivatives employed as “gatekeepers” and microparticles coated through host-guest interactions with β-cyclodextrin to regulate paraquat release, forming a dual-coated photoresponsive controlled-release system (PQ@MOF@CC@CD). The synthesized PQ@MOF@CC@CD microparticles exhibit an octahedral morphology, with an average particle size of 457.37 nm and a paraquat loading capacity of 22.07 %. Upon exposure to UV/sunlight irradiation, cinnamic acid derivatives on the microparticle surface undergo trans-cis isomerization, leading to their dissociation from β-CD cavities. This process induces coating shedding, pore opening, and paraquat release. In vitro release studies confirm the microparticles’ strong photoresponsiveness and sustained-release properties. Furthermore, these microparticles effectively prevent paraquat degradation in alkaline environments. Herbicidal activity assessments indicate that PQ@MOF@CC@CD exhibits comparable efficacy to free paraquat at equivalent doses under sunlight. Compared to paraquat technical formulations, PQ@MOF@CC@CD microparticles demonstrate improved safety in cellular models and murine assays. Overall, PQ@MOF@CC@CD represents a cleaner agrochemical strategy, offering a dual benefit of minimizing human exposure risks and environmental impact through controlled pesticide release and safeguarding agricultural productivity, thereby advancing sustainable herbicide management practices.