Preparation of CuCo2O4@NFs nanoflower material with abundant VO/VCo: An excellent catalyst for oxidative breakage of the β-O-4 bond of lignin

A hollow nanoflower material CuCo₂O₄@NFs with abundant oxygen vacancies (V_O) and cobalt vacancies (V_Co) was prepared by a simple method. The novel material CuCo₂O₄@NFs showed excellent oxidation activity, cleaving the β-O-4 bond in lignin model compounds. Conversion of the substrate was as high as 99.02 %, and the yield of the main product, phenol, reached 49.50 %. Structural analysis showed that the petal and cavity form of the material increased its specific surface area, which facilitated its full contact with O₂ molecules. Moreover, the V_O generated by lattice oxygen detachment during annealing favor the adsorption of O₂, and the V_Co generated through lattice distortion induced by Cu-metal doping promoted the detachment of oxygen intermediates. The synergy of these two defects improved the rate of the rate-limiting step. Density functional theory calculations revealed that the synergistic effect of V_O and V_Co narrowed the gap between the Fermi energy levels and the d-band center, thereby enhancing electron mobility. Finally, excellent recyclability of CuCo₂O₄@NFs was confirmed through cycling experiments. The application of this material provided technical support for the efficient cracking of lignin into high-value-added chemicals and realized the effective utilization of woody biomass resources.