Zn vacancy-engineered Au-based catalysts for the selective oxidation of glycerol to 1,3-dihydroxyacetone

The efficient catalytic oxidation of biomass to produce high-value chemicals has become a major focus of current research. In this work, we report an Au/Zn_vAl-MMO catalyst rich in zinc vacancies, which exhibits excellent catalytic performance in the selective oxidation of glycerol (conversion of ∼97.8% and a DHA yield of ∼80.4%). Experimental studies [X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure (XAFS), and in situ CO diffuse reflectance infrared Fourier transform spectroscopy (CO-DRIFTS)] indicate that the introduction of Zn defects leads to electron enrichment on O atoms adjacent to Zn vacancies, which promotes the reduction of Au and simultaneously forms unique Au^δ+-O-Zn_v interfacial sites. Kinetic experiments further demonstrate that catalysts with a higher Au⁰ content exhibit a stronger ability to activate O₂, resulting in significantly enhanced glycerol conversion. Combined in situ Fourier-transform infrared (FT-IR) spectroscopy and density functional theory (DFT) calculations reveal that the secondary O-H bond of glycerol preferentially adsorbs and activates at the Zn sites of the Au^δ+-O-Zn_v interfacial structure. Meanwhile, the interfacial Au^δ+ species facilitate the storage and migration of OH^- and OOH^- species. In addition, the electron-rich interfacial oxygen atoms establish stronger hydrogen-bonding interactions with the secondary O-H and β-H groups, thereby synergistically promoting the cleavage of both the secondary O-H and β-H bonds. This work not only offers important insights into the oxidation pathways of polyols, but also provides a simple and effective strategy for the efficient catalytic oxidation of biomass to produce high-value chemicals.