WO_x boosted hollow Ni nanoreactors for the hydrodeoxygenation of lignin derivatives

Reasonable design of non-noble metal catalysts with hollow open structure for hydrodeoxygenation (HDO) of lignin derivatives to value-added chemicals is of great significance but challenging. Herein, a novel MOF-derived multilayer hollow sphere coated nickel‑tungsten bimetallic catalyst (Ni₂-WO_x@CN-700) was fabricated via by confined pyrolysis strategy using bimetallic MOFs as a self-sacrificial template, which exhibits robust activity for the typical model HDO of vanillin to 2-methoxy-4-methylphenol (Yield of 100 % at 140 °C for no less than 10 cycles). The characterizations revealed that WO_x facilitated the dispersion of Ni nanoparticles and adjusted the acidic capacity of the catalyst through the formed Ni-WO_x heterojunction. Density functional theory (DFT) calculations confirms that WO_x species enhanced the electron-rich nature of the active sites, while the adsorption energies of H₂ and vanillin on Ni-WO_x decreased from -0.572 eV and - 0.622 eV on Ni to -3.969 eV and - 4.922 eV, respectively. These results further indicated that the high activity of Ni₂-WO_x@CN-700 was attributed to the Ni-WO_x heterojunction. Based on the characterizations and the thermodynamic calculations, the reaction mechanism was proposed. In addition, the catalyst shows good substrate universality, which enables its good commercial application prospect.