Water enabled ambient-temperature biomass upgrading over a hydrophilic nano-cobalt superstructure

Liquid phase heterogeneous catalytic hydrogenation is of great significance for the green and sustainable upgrading of biomass and its derivatives. Here, we report the synthesis of a novel hydrophilic spherical hollow superstructure composed of interconnected metallic cobalt nanoparticles coated by oxygenated carbon (ss-CoNPs/OC) via the reductive pyrolysis of Co-malonic acid complex precursor. Using water as a green solvent, the resultant ss-CoNPs/OC catalyst exhibits exceptional catalytic activity and stability for the hydrogenation of biomass-derived 5-hydroxymethylfurfural (HMF) into 2,5-dihydroxymethylfuran at ambient temperature. Advanced nuclear magnetic resonance spectroscopy, mass spectrometry, and density functional theory calculations reveal that the remarkable hydrogenation performance in aqueous medium arises from hydrogen bonding-induced interactions among solvent, reactant and active Co sites. These interactions not only promote strong adsorption of HMF onto the Co surface but also enable a hydrogen desorption-mediated reaction pathway with a lower energy barrier. Importantly, water enables efficient and stable conversion of a diverse range of biomass-derived substrates, including aldehydes, carbonyl compounds, alkenes, N-heterocycles, and nitro compounds, into value-added chemicals and fuels over the ss-CoNPs/OC catalyst at ambient temperature, even on the gram-scale experiments (5 g feedstocks, >99 % yields).