Improving the hydrodeoxygenation activity of vanillin and its homologous compounds by employing MoO-incorporated Co-BTC MOF-derived MoCoO@C.

Lignin-derived aryl ethers and vanillin are essential platform chemicals that fulfil the demands for renewable aromatic compounds. Herein, an efficient heterogeneous catalyst is reported for reforming vanillin a selective hydrodeoxygenation route to 2-methoxy-4-methyl phenol (MMP), a precursor to medicinal, food, and petrochemical industries. A series of MoCoO@C catalysts were synthesized by decorating the Co-BTC MOF with different contents of MoO rods, followed by carbonization. Among these catalysts, MoCoO@C-2 afforded ∼99% vanillin conversion and ∼99% MMP selectivity at 150 °C in 1.5 h in an aqueous medium. In contrast, CoO@C afforded ∼75% vanillin conversion and ∼85% MMP selectivity. Detailed catalyst characterization revealed that CoO and CoMoO were the active species contributing to the higher activity of MoCoO@C-2. The excellent H-adsorption characteristics and acidity of MoCoO@C-2 were beneficial to the hydrodeoxygenation of vanillin and other homologous compounds. The DFT adsorption energy calculations suggested the favourable interactions of vanillin and vanillyl alcohol with the CoMoO sites in MoCoO@C-2. The catalyst could be efficiently recycled 5 times, with a negligible loss in activity after the 5th cycle. These findings provide a systematic explication of the active sites of the mixed metal oxide-based MoCoO@C-2 catalyst for the selective hydrodeoxygenation of vanillin to MMP, which is important for the academic and industrial catalysis community.