Heterostructured CeO(2)–M (M = Co, Cu, Mn, Fe, Ni) Oxide Nanocatalysts for the Visible-Light Photooxidation of Pinene to Aroma Oxygenates

[Image: see text] Herein, we report the enhanced photocatalytic activity of heterostructured CeO(2) nanocatalysts interfaced with Cu, Co, Ni, Mn, and Fe metal oxides. The CeO(2) catalysts exhibited an enhanced red shift in the visible-light response compared to CeO(2). This improved absorption range effectively suppressed electron (e(–))/hole ((+)h) recombination by forming localized energy bands associated with defect oxygen vacancies (V(o)) induced by the M(n+) ions incorporated in CeO(2). Under visible-light irradiation, CeO(2) catalysts are active for α-pinene oxidation to the aroma oxygenates, pinene oxide, verbenol, and verbenone. Both Fe(2)O(3)–CeO(2) and NiO–CeO(2) gave the highest pinene conversions of 71.3 and 53.1%, respectively, with corresponding pinene oxide selectivities of 57.3 and 58.2%. The enhanced photocatalytic performance of the heterostructured CeO(2) catalysts compared to CeO(2) is attributed to their enhanced visible-light absorption range and efficient suppression of e(–)/(+)h recombination. The Fe(2)O(3)–CeO(2) catalyst was highly recyclable and did not show any significant loss of its photoactivity.