Flower-like N-Doped Carbon-Encapsulated Nano Co-CoO x for the Hydrogenation of 5-Hydroxymethylfurfural

The nano Co-CoO x encapsulated within three-dimensional flower-like N-doped biobased carbon was synthesized through a facile hydrothermal method with urea as the nitrogen source, cobalt acetate as the catalyst precursor, and glucose as both the carbon source and structure-directing agent. The results demonstrated that the catalyst featured a three-dimensional flower-like morphology by self-assembly of two-dimensional carbon nanosheets and thus facilitated mass transfer and exposed more accessible active sites. Besides, the nano Co-CoO x species coated by an ultrathin carbon layer were uniformly embedded within the two-dimensional N-doped carbon nanosheets. In this case, the unique structure significantly protected the nano Co-CoO x species against aggregation and more importantly decorated their electronic properties through strong interaction with the coated carbon layer. The Co 0 and CoO x species were identified to synergistically boost the selective hydrogenation of HMF to DMF with a conversion of 100% and a selectivity of 92.2% under the optimum reaction conditions even using low-cost and nontoxic ethanol as the reaction medium. After five recycles, the HMF conversion still remained at 100%, and the DMF selectivity slightly decreased by merely 1.3%, indicating robust reusability and structure stability.