A pH-responsive MOF for site-specific delivery of fungicide to control citrus disease of Botrytis cinerea

Pesticides have been always restricted by poor efficacy and inacceptable toxicity. In this work, a pH-sensitive controlled-release nano-capsule of fungicide, Boscalid@ZIF-67 (ZIF is a subclass of MOF), was prepared based on metal-organic framework (MOF) for higher antifungal effect and low bio-toxicity. The Boscalid@ZIF-67 was formed by physical adsorption method and it possesses uniform size and dodecahedral shape. The loading ratio is as high as 18%. In addition, the release of fungicide Boscalid showed pH sensitive response due to the weak acidic group in the MOF structure, in which the rate of release was more rapid under acid condition (＜7). Cumulative release rate release was higher about 25% and 38% adjusted from 7 to 3.5 and from 7 to 5.5 on the 6th day than that under neutral condition. At the early stage of infecting the host plant, Botrytis cinerea will produce more acidic substances such as oxalic acid, which are conducive to Boscalid@ZIF-67 disintegration for rapid release of Boscalid. Meanwhile, the antifungal effect of Boscalid@ZIF-67 was 4-6 times more of that commercially available product on Botrytis cinerea, while the bio-toxicity under the same condition is much lower than that of latter. Thus, this work not only proves that Boscalid@ZIF-67 could be used as nanoparticles platform for smart control over Botrytis cinerea, but also has great potential to improve traditional modalities by addressing the crop diseases in economic and ecological manner.