Enhancing the selective conversion of alcohols to aldehydes using oxygen over heterogeneous photocatalysts — critical factors with emphasis on benzyl alcohol

Abstract Heterogeneous photocatalysis is an advanced oxidation technique widely explored for the selective conversion of benzyl alcohol (C 7 H 8 O) into benzaldehyde, an important intermediate in organic synthesis. This review critically examines the influence of key operational and morphological factors—including solvent choice, temperature, and light intensity—on photocatalytic performance. The synthesis method notably affects catalyst activity, with solvothermal preparation of TiO 2 significantly enhancing the reaction rate constant. Photo-deposition emerges as an effective alternative when both catalyst and support materials are available. Among various TiO 2 nanostructures (nanowires, nanotubes, nanofibers, nanosheets, and hollow nanospheres), hollow nanospheres exhibit superior photocatalytic activity due to improved light absorption and charge separation. Elevated light intensity and temperature further accelerate the reaction rate, resulting in higher rate constants. A range of catalysts—including C-ZnInS 4 , ZnInS 4 , Pt-TiO 2 , RuO 2 /TiO 2 nanobelts, 0.95Ru/3DOM BiVO 4 -Ar-300, Pt/Bi 2 MoO 6 -glycerol, Ni-OTO 2 , W 10 O 32 4− ,WO 3 (7.6)/TiO 2 , TiO 1.966 .N 0.034 , and Bi 2 WO 6 —demonstrate promising rate constants of 75.0, 53.75, 57, 46.0, 38.0, 34.0, 33.25, 29.6, 28.0, 27.0 and 22.25 g cat −1 h −1 for alcohol oxidation. Notably, TiO 2 N 0.034 and ZnIn 2 S 4 achieve 100% conversion with > 99% selectivity within 4 and 2 h, respectively, underscoring their excellent photocatalytic potential.