Oxygen Insertion-Driven Aerobic Oxidation of Diols over Pd Atomic Layers on Au Decahedra

The aerobic oxidation of aliphatic diols to lactones, such as 1,4-butanediol (BDO) to γ-butyrolactone (GBL), is of great interest but challenging in terms of catalytic efficiency and selectivity. While Pd-Au-based catalysts have been extensively investigated, research to date has largely focused on enhancing catalytic activity by lowering the activation barrier for C-H bond cleavage and increasing the number of sites available for O₂ activation. Herein, we report that a Pd-Au/TiO₂ catalyst featuring Pd atomic layers supported on Au decahedra delivers 96.0% GBL selectivity at 98.7% BDO conversion in aerobic oxidation. The turnover frequency (TOF) over 30Pd-Au/TiO₂ reaches 22038 h^-1, a value markedly higher than those reported previously for either Pd or Au catalysts. An abnormal ¹⁸O₂ KIE effect and the generation of singly ¹⁸O-labeled 2-hydroxytetrahydrofuran (2-HTHF, 53.4%) and GBL (58.0%) over Pd-Au/TiO₂, combined with in situ FTIR and DFT simulations, point to a mechanism involving insertion of oxygen species into the α-C-H bond to generate a COO* intermediate. Subsequent cleavage of the C-O bond within the COO* to yield an absorbed carbonyl, followed by intramolecular cyclization, constitutes the rate-determining step.