Synergistic Effect of Ni Exsolution and Oxygen Vacancies in NiAl₂O₄ for Catalytic Transfer Hydrodeoxygenation of Furfural to 2-Methylfuran

The exsolution of metal nanoparticles from solid lattices provides a strategy for designing efficient catalysts in catalytic transfer hydrodeoxygenation (CTHDO). This approach allows precise control over key catalytic properties, including nanoparticle density, surface acidity, and oxygen vacancies, which are crucial for the optimization of CTHDO reactions. We report a NiAl2O4-550 catalyst for the selective CTHDO of furfural (FUR) to 2-methylfuran (2-MF) with high selectivity. Using isopropyl alcohol (IPA) as a hydrogen donor, NiAl2O4-550 exhibited a high performance under favorable reaction conditions. Characterization (PXRD, Raman, TEM, XPS, NH3-TPD, Pyridine-FTIR, and H2-TPR/TPD) highlights the role of surface oxygen vacancies and exsolved Ni-metal in enhancing catalytic activity. XPS, O2-TPD, and EPR confirm their contributions to FUR conversion. DFT calculations reveal that oxygen-deficient sites improve substrate–catalyst interactions, lowering the energy barrier for FUR to 2-MF conversion. Under mild conditions (180 °C, 2 MPa of N2), NiAl2O4-550 afforded ∼99% FUR conversion with a 98.1% 2-MF selectivity, surpassing that of reported catalysts. The combination of oxygen vacancies and metal exsolution enables controlled transfer hydrodeoxygenation, offering an effective strategy for biofuel production. This study establishes a versatile platform for next-generation catalysts in environmentally conscious catalysis, contributing to advancements in catalyst design.