Enhanced separation and purification of vanillin in aqueous-phase through specific Achiff base covalent imprinting.

Conventional hydrogen-bonded molecularly imprinted polymers (MIPs) suffered from significantly compromised adsorption performance in aqueous environments due to competitive interference from water molecules. To overcome this limitation, this study developed a novel imprinting strategy based on reversible Schiff base bonding. Schiff base covalent imprinting utilizes aldehyde groups and amino groups to form reversible covalent bonds (C = N), achieving specific recognition between template molecules and functional monomers. Schiff base has strong affinity and selectivity, which can effectively reduce the competitive interference of water molecules in aqueous environments. The amino groups of the functional monomer (4-vinyl aniline, 4-VAn) and the aldehyde groups of vanillin (Vnl) formed a precursor via Schiff base reaction, which was then copolymerized with the crosslinker divinylbenzene (DVB) to fabricate molecularly imprinted polymer microspheres (S-MIPs). The adsorption of Vnl by S-MIPs follows a chemisorption mechanism dominated by covalent recognition, which is significantly influenced by the pH of the aqueous solution. S-MIPs demonstrated excellent specificity and reusability, with an adsorption capacity of 163.95 mg·g-1, an imprinting factor of 3.27, and the recoveries of Vnl ranged from 91.76% to 96.02% in milk tea samples. This strategy effectively enhances the aqueous-phase adsorption performance of molecularly imprinted polymers by constructing stable covalent recognition sites, providing a new approach for the development of high-performance aqueous-phase recognition materials.