Ru single atoms in Mn₂O₃ efficiently promote the catalytic oxidation of 5-hydroxymethylfurfural through dual activation of lattice and molecular oxygen

Concurrent activation of lattice oxygen (O_L) and molecular oxygen (O₂) is crucial for the efficient catalytic oxidation of biomass-derived molecules over metal oxides. Herein, we report that the introduction of ultralow-loading of Ru single atoms (0.42 wt%) into Mn₂O₃ matrix (0.4%Ru–Mn₂O₃) greatly boosts its catalytic activity for the aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA). The FDCA productivity over the 0.4%Ru–Mn₂O₃ (5.4 mmol_FDCA·g_cat^-1·h^-1) is 4.9 times higher than the Mn₂O₃. Especially, this FDCA productivity is also significantly higher than that of existing Ru and Mn-based catalysts. Experimental and theoretical investigations discovered that the Ru single atom facilitated the formation of oxygen vacancy (O_v) in the catalyst, which synergistically weakened the Mn–O bond and promoted the activation of O_L. The co-presence of Ru single atoms and O_v also promote the adsorption and activation of both O₂ and HMF. Consequently, the dehydrogenation reaction energy barrier of the rate-determining step was reduced via both the O_L and chemisorbed O₂ dehydrogenation pathways, thus boosting the catalytic oxidation reactions.