Rationally designed hybrid molecularly imprinted polymer foam for highly efficient λ-cyhalothrin recognition and uptake via twice imprinting strategy

Herein we reported a novel method for preparation of hybrid molecularly imprinted polymer foams (MIPFs) via a twice imprinting strategy. Firstly, based on halloysite nanotubes (HNTs) cores, three molecularly imprinted nanomaterials (MIPs-S, MIPs-M and MIPs-L) with controlled thickness of imprinted shells (i.e., 7.0   nm, 17   nm and 36   nm, respectively), were prepared by precipitation polymerization. The surface hydrophobicity of MIP nanomaterials gradually enhanced with the increasing thickness of imprinted shells. Secondly, three hybrid MIP foams (MIPFs-S, MIPFs-M, MIPFs-L) were successively fabricated by W/O Pickering high internal phase emulsions (HIPEs) template stabilized by the corresponding MIPs nanomaterials. Due to the increased hydrophobicity of the MIPs nanomaterials, the amount of interconnecting pores in hybrid MIPFs was continuously decreased until a closed-cell structure appeared, while the average void diameter increased from 10   μm to 28   μm. Binding experiments demonstrated that optimized hybrid MIP foams (MIPFs-M) possessed enhanced adsorption capacity, fast kinetics and excellent recognition ability towards λ-cyhalothrin (LC). Therefore, this two-step imprinting strategy could not only figure out the difficulty in solid–liquid phase separation and the recycling of nano-sized MIPs but also overcome the disadvantage of stabilizing solid particles on the surface of MIPFs referring to the lack of specific adsorption activity.