Notched-Polyoxometalate Strategy to Fabricate Atomically Dispersed Ru Catalysts for Biomass Conversion

The development of the synthesis methods of single-atom catalysts (SACs) is of great significance for the study of the specificity of SACs. Herein, we report a strategy to immobilize Ru atom using notched-polyoxometalate (N-POM) to prevent Ru from aggregation during pyrolysis and obtain a Ru catalyst with atomically dispersed Ru anchored on uniform subsupporter WOx clusters on carbon-nitrogen (Ru1@WOx/CN). Interestingly, the as-synthesized Ru1@WOx/CN catalyst exhibits an outstanding catalytic activity for the hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) in solvent-free condition (conversion of over 99% and selectivity of ∼100%). According to experimental analysis and density functional theory (DFT) calculations, both the regulation of the electronic structure of Ru active center through the subsupporter WOx clusters as well as the CN substrate and the catalysis of the acidifying WOx in the reaction for the dehydrogenation of 4-hydroxypentanoic acid intermediate are correlated with the enhancement of the enhanced catalytic activity. This N-POM strategy is also demonstrated to be impressive in preparing a series of atomically dispersed noble-metal atoms, which provides an opportunity of discovering SACs.