In situ-generated Co embedded in N-doped carbon hybrids as robust catalysts for the upgrading of levulinic acid in aqueous phase†
The rational design of an efficient and robust catalyst based on non-noble metals for the upgrading of levulinic acid to γ-valerolactone in aqueous media still remains a significant challenge. Herein, a facile and effective approach is developed for synthesizing a Co embedded in nitrogen-doped carbon matrix by a coordination precipitation and pyrolysis combination strategy. The as-prepared Co@NC-800 (after 800 °C pyrolysis) exhibits excellent catalytic performance, namely, the yield of γ-valerolactone is not less than 99%, and the high activity could be maintained even after 10 cycles. The results of systematic characterization and control experiments confirmed that the catalytic performance of the catalyst benefited from the construction strategy in two ways: certain proportions of Co, Co–Nx and Co–Ox components are generated on the catalyst, and also a structure in which Co is confined into a N-doped carbon matrix is formed. The first aspect apparently enhances the activity of the catalyst due to the synergistic effect of Co, Co–Nx and Co–Ox, while the second aspect greatly inhibits the metal components from leaching and agglomeration in the reaction process, thus promising excellent stability of the catalyst. The strategy developed here may open up a new avenue toward the development of low-cost high-performance biomass conversion catalysts.