Molecularly imprinted core–shell hybrid microspheres for the selective extraction of vanillin

Abstract

Molecularly imprinted polymers (MIPs) with a core–shell structure for efficient, reliable, and selective extraction of vanillin via solid-phase extraction (SPE) and incubation methods were developed using a sol–gel process based on (3-aminopropyl)triethoxysilane (APTES) as the functional monomer, tetraethoxysilane (TEOS) as the cross-linker, and vanillin as the template. An inorganic core composed of porous (SM1) and non-porous (SM2) silica microspheres was prepared by co-condensation of TEOS and (3-aminopropyl)trimethoxysilane (APTMS) in a water-in-oil (W/O) macroemulsion. The thus synthesized materials were characterized in detail, and their molecular recognition properties and selectivity were demonstrated by evaluating their adsorption capacity and binding kinetics at imprinted (MIP) and non-imprinted (NIP) control materials. The proposed binding mechanism takes advantage of the amino groups associated with APTES interacting with the functional groups of the template molecules to form hydrogen-bonded complexes. Furthermore, synthesis conditions were optimized such that the imprinting efficiency and adsorption capacity were maximized. Finally, it was demonstrated via incubation experiments that the thus generated MIP core–shell hybrid microspheres provide rapid adsorption with high binding capacities (up to 5.64 mg g⁻¹), excellent imprinting factors (IF up to 2.37), and exceptional reusability (reused >20 times).