Non-noble metal Co@hollow carbon spheres for highly efficient one-hour phenol conversion to cyclohexanol via temperature-controlled structural engineering

Cyclohexanol is an important intermediate in the chemical industry and the synthesis of cyclohexanol from phenol by hydrogenation is a green and efficient process. In this paper, hollow carbon sphere nanoreactors ([email protected], T: temperature) with tunable microenvironment were synthesized by adjusting the pyrolysis temperature using soft template method. The characterization analysis demonstrated that the pyrolysis temperature could adjust the defect density and pore structure of the catalyst. When combined with experimental results and mechanistic studies, hydrogen and phenol were found to diffuse through multistage orifices into the cavities of the catalysts with enhanced mass transfer efficiency, and high defect density and highly dispersed cobalt nanoparticles were found to promote the activation and reaction of hydrogen and phenol. The [email protected]–600 catalyst shows significant catalytic activity at 140 °C for 1 h with 88.9 % phenol conversion and 99.9 % cyclohexanol selectivity. The good reaction activity of [email protected]–600 can be attributed to the catalyst's high defect density (I_D/I_G=2.77), substantial metal dispersion (45.67 %), a specific surface area of 588 m²/g, and an average pore size of 3.53 nm. Concurrently, [email protected]–600 demonstrated remarkable universality in catalyzing the hydrogenation of a diverse array of lignin-derived monomers and dimers.