<p>The selective oxidation of lignin feedstock-derived alcohol is a sustainable process for the synthesis of aldehyde. Vanillyl alcohol is used as a model component of lignin feedstock-derived alcohol. Moreover, Cu-impregnated CaAl₂O₄ spinel catalysts were synthesised and investigated for their catalytic efficiency in the selective oxidation of vanillyl alcohol via thermal and photochemical routes. Copper impregnated into the CaAl₂O₄ spinel support significantly altered its structural, morphological, and catalytic properties, as confirmed by extensive characterisation techniques such as XRD, Raman spectroscopy, FTIR, XPS, HR-TEM, surface area analysis, LSV, photoluminescence studies, and ICP-AES. 5% Cu/CaAl₂O₄ catalyst showed 98.1% vanillin with 99.6% selectivity, demonstrating exceptional efficiency. Catalytic activity greatly increased due to the high surface area and evenly distributed active sites. The presence of Cu²⁺, octahedral Al³⁺, and Ca-O-Al active sites has been identified as critical to the observed activity. Moreover, the catalyst showed higher conversion and selectivity for commercially significant aliphatic and aromatic alcohols. A thorough structural-activity relationship was discovered, emphasising the influence of copper on catalyst structure. Furthermore, the study compares the mechanisms and performance of thermal and photocatalytic alcohol selective oxidation. Mechanistic insights were obtained through ATR-FTIR adsorption studies and in-situ ESR spectroscopy, which provided evidence for the formation of reactive intermediates during the reaction.</p> Graphical Abstract <p></p>