Atomically Dispersed Electron-Rich Ru Species in CoOx for the Efficient Catalytic Hydrogenolysis of 5-Hydroxymethylfurfural

Abstract

Modulating the electronic environment of single-atom metal catalysts is a promising yet challenging strategy to optimize their catalytic performance. Herein, electron-rich Ru single atoms were successfully confined within a CoO_x matrix (Ru_0.6CoO_x) through a simple manual grinding-reduction strategy. The resulting Ru_0.6CoO_x catalyst demonstrated exceptional catalytic activity for the hydrogenolysis of 5-hydroxymethylfurfural (HMF) to 2,5-dimethylfuran (DMF), affording a nearly quantitative DMF yield with an impressive DMF productivity of 210.2 mol_DMF·mol^–1_Ru·h^–1 at 160 °C. This productivity outperforms most of the noble metal-based catalysts for DMF production. Notably, Ru_0.6CoO_x also enabled the efficient conversion of HMF to DMF at a low reaction temperature of 120 °C or using a concentrated HMF solution (up to 20 wt %). Experimental studies combined with density functional theory calculations (DFT) revealed that the electronic interaction between the Ru species and CoO_x generates electron-rich Ru single atoms, which serve as active sites to boost the H₂ activation. Furthermore, the introduction of single Ru atoms was shown to increase the acidity of Ru_0.6CoO_x, thereby facilitating the cleavage of the C–OH bond during HMF hydrogenolysis. The boosted H₂ activation ability and improved acidity of Ru_0.6CoO_x contribute significantly to its outstanding catalytic performance. This work provides valuable insights into the preparation of electron-rich single-atom metal catalysts for the catalytic hydrodeoxygenation of biomass-derived chemicals.