Palladium-Supported Surface-Oxidized Mo2C MXenes for the Tandem Hydrogenation–Hydrogenolysis of Furfurals via Hydrogen Spillover

Developing an efficient catalyst for the tandem hydrogenation–hydrogenolysis of furfurals to methyl furans (MFs) is crucial for synthesizing biofuels and high-value chemicals but is challenging by virtue of easy C=C hydrogenation and difficult CH2–OH hydrogenolysis. Herein, a palladium (Pd) nanoparticle-supported surface-oxidized molybdenum carbide (Mo2C) MXene was prepared, which exhibited a uniquely high MF yield of 92.5% from furfural at an unprecedented low temperature of 50 °C. Catalytic mechanism analysis confirmed that the hydrogen spillover from Pd nanoparticles to Mo–O sites on the MXene support generated frustrated Hδ+···Hδ− pairs that acted as atypical hydrogenation sites for the C=O hydrogenation step of furfural and as Bro̷nsted acid sites for the CH2–OH hydrogenolysis step of furan alcohol, thereby promoting the efficient preparation of MF. Furthermore, the prepared MXene exhibited catalytic universality and extensibility for converting various furfurals, benzaldehydes, and picolinaldehydes to methyl aromatics (i.e., MFs, methylbenzenes, and methylpyridines). This study demonstrated interesting metal–acid bifunctional catalysis over a surface-oxidized MXene by triggering hydrogen spillover to form transient Hδ+···Hδ− pairs, offering a straightforward pathway for converting aromatic aldehydes to methyl aromatics.