Insights into the Role of Dual-Interfacial Sites in Cu/ZrO Catalysts in 5-HMF Hydrogenolysis with Isopropanol.

In this work, we synthesized a series of Cu/ZrO catalysts with tunable V-Cu (oxygen vacancy adjacent to Cu metal) and V-Cu (zirconium vacancy adjacent to electron-deficient Cu species) dual-interface sites and investigated the role of the dual-interface sites in the 5-hydroxymethylfurfural (5-HMF) hydrogenolysis reaction with isopropanol as the hydrogen source. By combining a series of infrared characterization and catalytic performance analysis, it is identified that V-Cu interface sites were responsible for activating isopropanol dehydrogenation and C═O dissociation of 5-HMF, while the V-Cu interface sites were responsible for the dehydroxylation of an intermediate product 5-methyl-2-furfuryl alcohol (5-MFA). Specifically, C-OH was first deprotonated on the V at the V-Cu interface site to reduce the activation energy of 5-MFA dehydroxylation and then adjacent Cu promoted the dissociation of the C-O bond by enhancing the adsorption energy while elongating the C-O bond, as confirmed by the density functional theory calculations. Because the dual-interface sites provided separate sites for activating intermediate products and reactants, the coupling reaction caused by competitive adsorption is thus well avoided. Therefore, the optimized Cu/ZrO catalyst with the most V-Cu and moderate V-Cu sites exhibited 98.4% of 2,5-dimethylfuran yield under the conditions of 180 °C and self-vapor pressure.