Tannic Acid-Fe3+ Network-Coated Defective Bimetallic ZnM-ZIF (M = Cu and Ni) for Enhanced Pesticide-Loading Capacity and Pest Control

Zeolite imidazolate frameworks (ZIFs) are ideal candidates for pesticide carriers due to their simple preparation and biocompatibility. However, the reported ZIF carriers generally have low loading capacity with an unclear structure-property relationship. Herein, two novel defective bimetallic ZnM-ZIFs (M = Cu and Ni) based on leafy ZIF-L were prepared as carriers, and the correlation between structural property and loading capacity was studied using gray correlation analysis. The results showed that the second metal created defects in leafy ZnM-ZIFs that increased its mesoporosity and oxygen vacancy, thus improving the pesticide loading rate. Among them, Zn0.6Cu0.4-ZIF (30.96%) and Zn0.4Ni0.6-ZIF (19.03%) showed the highest loading rate for imidacloprid (IMI), which was 2.31 and 1.42 times higher than that of ZIF-L, respectively. After coating the metal-phenolic network (MPN) as a blocker, the final ZnM-ZIF@IMI@MPN showed higher insecticidal activity against Bemisia tabaci (1.47-1.98 times) and longer efficacy duration (1.51-1.65 times) than IMI technical (TC). Besides, the ZnM-ZIF@IMI@MPN exhibited higher photostability (2.33-2.97 times that of the TC), good pH-responsive release, stronger foliar adhesion, and favorable safety. This work gives deep insight into the effect of the second metal on the loading performance of ZnM-ZIF and provides a strategy for developing a defective bimetallic ZIF pesticide system.