Copper Clusters Encapsulated in Carbonaceous Mesoporous Silica Nanospheres for the Valorization of Biomass-Derived Molecules

Cu-based catalysts possess prominent properties in the selective hydrogenation of carbon-oxygen bonds but suffer from low stability due to high-temperature sintering. Dandelion-like nanosized mesoporous silica spheres (NMSSs) with short mesochannels can afford a nanoconfined space restraining the metal from aggregating. Herein, we report an air-assisted low-temperature carbonization of the surfactant template strategy for fabricating N-doped carbon-coated NMSSs (NC@NMSSs) encapsulated ultra-dispersed Cu cluster catalysts (Cu/NC@NMSSs). The as-obtained catalysts have demonstrated excellent performances in the hydrogenation of biomass-derived levulinic acid (LA) into γ-valerolactone (GVL), achieving a GVL yield as high as 96% and commendable stability in 100 h. The functional N species and C═O groups on the NC coating layer play a critical role in stabilizing and dispersing Cu clusters. Theoretical calculations reveal that the pyrrolic and pyridinic N sites can enrich LA reactants. Accordingly, the apparent activation energy (Ea) is reduced by half and the turnover frequency doubled compared to Cu/NMSS catalysts. Additionally, the catalysts displayed high hydrogenation activities for a variety of aldehydes, ketones, and nitroarenes. This work offers a convenient strategy for constructing promising Cu-based catalysts in upgrading biomass-derived compounds.