Bifunctional Role of Hydrogen in Aqueous Hydrogenative Ring Rearrangement of Furfurals over Co@Co-NC

Bifunctional hydrogenation and acid catalysis in aqueous solvents over reduced metal-supported solid acids is a common method for tandem reactions of biomass derivates. Traditionally, hydrogen (H2) was used as the reductant for the hydrogenation steps and rarely reported as a promoter in the acid-catalyzed steps. Herein, Co-embedded N-doped carbon (Co@Co-NCs) is used for the bifunctional catalytic conversion of furfurals into cyclopentanols. In addition to being a reductant for the hydrogenation step over the Co nanoparticle core, H2 can act as a catalyst to induce the acid–base transformation of the Co-NC shell from Lewis acid–base pairs into Brønsted acid–base pairs via heterolysis and a subsequent water-mediated mechanism, which largely promotes the acid-catalyzed step. Compared with Co/C, Co@Co-NCs show a better bifunctional catalytic performance with cyclopentanol yields above 90%. This study redefines the role of H2, which has important implications for many reduction reactions with water as a solvent.