Insights into the Multiple Synergies of Supports in the Selective Oxidation of Glycerol to Dihydroxyacetone: Layered Double Hydroxide Supported Au

Oxidation of the secondary O–H bond of glycerol to dihydroxyacetone is an important reaction in the production of high-value-added chemicals. The heterogeneous catalytic oxidation route using supported Au as a catalyst in this crucial reaction has attracted considerable attention. However, targeted activation of the secondary O–H bond and satisfactory catalytic efficacy remain considerable challenges. This work reports layered double hydroxide (LDH) supported Au catalysts for the targeted activation of the secondary O–H bond and provides deep insights into the active sites and the roles of the LDH support in glycerol selective oxidation. By virtue of the tailorable chemical composition of the LDH brucite-like layer, Zn2Fe-, Co2Al-, Zn2Al-, Zn2Ga-, and Mg2Al-LDHs, displaying varied surface basic densities and hydroxyl vacancies (VOH), were applied as supports for Au nanoparticles in this work. A glycerol conversion of 72.9 ± 0.2% and a dihydroxyacetone selectivity of 63.8 ± 0.2% were achieved on ZnGa-LDH-supported Au. In addition to Au0, surface Aun+ (Au+ and Au3+) species are abundant in the interfacial MII–O–Aun+ linkages. Detailed investigations verify the cooperation between the surface basic sites on the LDH support for the activation of the secondary O–H bonds and the interfacial MII–O–Au+ sites for the activation of the secondary C–H bonds. Significantly, on Zn-containing LDHs, an additional synergy exists between the surface VOH sites and the interfacial ZnII–O–Au3+ species to further promote catalytic activity.