Insights on macro- and microscopic interactions between Confidor and cyclodextrin-based nanosponges

Imidacloprid is one of the most widely used soluble neonicotinoid insecticide, which is non-volatile and persists in the soil, with hazardous effects on birds, honeybees, and mammals. It is used in both agricultural and vet-erinary applications, and is found in at least 7% of European topsoils. One of the commercially available for-mulations is Confidor O-TEQ (R) that exhibits higher retention, spreading, and penetration capacity being in form of an oil suspension. In this work, porous materials based on cyclodextrin nanosponges (CDNSs) were developed for the efficient removal of imidacloprid. In the synthesis of CDNSs, alpha- and beta-cyclodextrin and two diamine monomers, hexane-1,6-diamine (HDA) and dodecane-1,12-diamine (DDA) were used. It was found that linkers with longer aliphatic chains resulted in CDNSs with higher thermal stability and crosslinking degree. alpha CD2-HDA and beta CD2-HDA showed superior sorption efficiency for Confidor O-TEQ (R), as evaluated by kinetic and equi-librium sorption analyses at optimal conditions. To better understand the effects of monomer chain length and type of cyclodextrin, the sorption performance of alpha CD and beta CD, alpha CD-HDA and beta CD-HDA, alpha CD-DDA and beta CD-DDA, dimeric alpha CD2-HDA and beta CD2-HDA, and alpha CD2-DDA and beta CD2-DDA with imidacloprid was also investigated by atomistic molecular dynamics simulations. Relevant contact patterns based on the identification of the stabilizing/destabilizing noncovalent interactions within the CD-based complexes were described in detail. Results suggest that significant modulation of the sorption performance of CDNSs for imidacloprid can be ach-ieved by imposing various features, with direct implications for the rational design of supramolecular materials with high sorption capacity for pesticides.