Green synthesis of water-compatible layer-by-layer assembled sandwich bread-like molecularly imprinted polymers for selective recognition of baicalin from Scutellariae Radix.

Molecularly imprinted polymers (MIPs) are typically synthesized in organic solvents, leading to poor compatibility with water, weak affinity and selectivity for target molecules in aqueous media. To address these challenges, a green and sustainable synthesis of sandwich bread-like ATP@MIP was conducted using polyethylenimide (PEI) and deep eutectic solvent (DES) as hydrophilic bi-functional monomers via layer-by-layer self-assembly on the attapulgite (ATP) carrier. The new ATP@MIP can provide a higher density of imprinting sites with more orderly and uniform distribution due to inhibiting the competitive polymerization between PEI and DES, thereby significantly enhancing recognition ability. Moreover, the ATP@MIP was synthesized in water, aligning with green chemistry principles and establishing a sustainable preparation method for MIP materials. Equipped with the remarkable merits of good water compatibility, excellent selectivity (IF=3.6), high adsorption capacity (77.6 mg g-1) and desirable repeatability (8 times), the as-prepared materials were used as a solid phase extraction adsorbent for efficient separation and enrichment of baicalin from Scutellariae Radix. More importantly, the recognizing performance of ATP@MIP for baicalin increased 1.40-1.69 times than other MIP materials, and its excellent specificity was demonstrated in comparison with several common commercial adsorbents (C18, HLB, MCX and SAX). Therefore, this work introduces a feasible and green strategy to synthesize water-compatible MIP materials for highly selective enrichment and separation of active components from natural products.