Structurally Intelligent Recognition and Enrichment of Photo-Responsive Dual-Monomer Imprinted Polymers for β-Sitosterol in Camellia Oil

To address the challenge of selectively extracting β-sitosterol from Camellia oil—a complex, lipid-rich matrix containing structurally similar sterols—a photo-responsive molecularly imprinted polymer (MIP) was developed using a hybrid functional monomer system. Functional monomers were systematically screened via UV–Vis spectroscopy and density functional theory (DFT) to ensure molecular-level selectivity and optimal cavity matching. The imprinting system combined methacrylic acid (MAA) with either acrylamide (AAm) or 3-aminopropyltriethoxysilane (APTES), introducing synergistic hydrogen bonding and π-π stacking. A photo-responsive azobenzene monomer enabled reversible photo-isomerization under 365/440 nm light, allowing precise spatiotemporal control of β-sitosterol adsorption/release. Co-assembly behavior was validated by 1 H-NMR spectroscopy. The MIPs were characterized by FT-IR, XPS, TGA, SEM, BET, DSC and UV-DRS, while molecular docking elucidated the photo-responsive mechanism. Adsorption performance was evaluated using isothermal, kinetic, and thermodynamic models, alongside imprinting factor analysis. When applied to solid-phase extraction (SPE) from crude Camellia oil, the MIPs exhibited excellent selectivity, reusability, and enrichment efficiency. The maximum adsorption capacity reached 11.02 mg/g, and β-sitosterol purity increased to 78.3% ~ 82.1%. This work offers a green, reusable, and light-controllable platform for selective sterol recovery from edible oil systems.