Photocatalytic partial oxidation of 4-vinylguaiacol to vanillin over TiO2: a biomimetic approach inspired by spirit aging

Inspired by natural oxidative aging processes observed in traditionally matured distilled spirits, we developed a biomimetic photocatalytic approach for the partial oxidation of 4-vinylguaiacol (4-VG)—a ferulic acid-derived aromatic compound—to vanillin using titanium dioxide (TiO 2 ) under ultraviolet (UV) light. The choice of 4-VG as the reaction substrate is rooted in its documented transformation during long-term spirit aging, which we sought to replicate and accelerate under controlled catalytic conditions. By optimizing the pH of aqueous ethanol media, vanillin selectivity reached up to S = 36 % under mild alkaline conditions. The observed pH dependence and solvent effect are consistent with a tentative mechanism involving β‑hydrogen abstraction and radical propagation, which may account for the enhanced selectivity under alkaline conditions. The photocatalytic performance was further evaluated in fermentation-derived multicomponent systems, where inhibitory effects from background silicate anions were identified, whereas low-concentration organic constituents had minimal impact. Ion exchange pretreatment successfully restored photocatalytic activity, underscoring the method's robustness. Product characterization, including sensory validation, confirmed the formation of vanillin, thereby supporting the proposed reaction pathway. This biomimetic oxidation approach offers a sustainable and scalable route for the transformation of bio-derived aromatic compounds under mild, water compatible conditions using non-biological catalysis. It effectively accelerates a naturally slow transformation into a rapid photocatalytic reaction completed within hours. • A biomimetic photocatalytic approach mimicking spirit aging was developed using TiO 2 . • Partial oxidation of 4-vinylguaiacol to vanillin proceeds under mild alkaline conditions. • Radical propagation appears to be promoted by β‑hydrogen abstraction from ethanol and pH effects. • The method remains effective in multicomponent matrices despite inorganic interference. • This study demonstrates a sustainable approach to bio-derived fine chemical production.