Controlled-release herbicide spheres: co-crystallization of 2,4-dichlorophenoxyacetic acid with l-menthol via green oiling-out process for low leaching and high activity

Background Excessive pesticide soil leaching (>99% loss) poses a critical environmental challenge. This study aimed to develop carrier free, slow release herbicide particles by integrating crystal engineering and spherical particle technology. Results A 2,4 dichlorophenoxyacetic acid–l menthol cocrystal was synthesized solvent free into spherical particles ( D 50 = 100–600 μm). These cocrystal particles reduced solubility by 21.6%, decreased dissolution rate by >50%, and reduced soil leaching by up to 93%, eliminating the need for carriers and avoiding secondary pollution. The release mechanism was governed by a multiscale diffusion limited process: enhanced hydrogen bonding networks elevated lattice energy, while solution mediated recrystallization transformed nanofibrous microstructures into diffusion restricting lamellar domains. Kinetic modeling indicated a transition from Fickian to hindered diffusion. Biological validation demonstrated superior weed control efficacy against chicory and shepherd's purse. Conclusion This integrated approach establishes a sustainable paradigm for precision agrochemical delivery by significantly reducing environmental leaching while maintaining high herbicidal activity. © 2026 Society of Chemical Industry.