Electron-Deficient Nickel Sites Provoked by the Adjacent Praseodymium Oxide Enable High-Performance Biomass Derivative Hydrogenation

Upgrading the renewable bioplatform molecules to high-value compounds has garnered significant attention. The synergistic effect among various metal components often enhances the catalytic performance of a composite catalyst. However, the ingenious integration of multifunctional sites into a single catalyst remains a critical challenge. Herein, this work developed a simply prepared nickel-inserted praseodymium oxide (Pr6O11) magnetic catalyst that realized the selective conversion of levulinic acid (LA) to γ-valerolactone (GVL) using low temperature and H2 pressure. By tailoring the electron-deficient Ni species within the Nix–PrOy (0.5 ≤ x ≤ 2) catalysts, more highly dispersed active Ni0 sites became exposed on the surface, accompanied by a substantial enrichment of oxygen vacancies (Vö) and Lewis acidic sites. The optimal Ni1–PrOy catalyst with multifunctional site integration achieved a 100% yield of GVL at 110 °C under 1 MPa of H2 after 4 h. Notably, it also delivered an intrinsic turnover frequency of 241.1 h–1 under milder conditions, remarkably outperforming typical Ni-based catalysts reported to date. The enhanced intrinsic activity of Ni1–PrOy stemmed from the synergistic catalysis among the active Ni0 sites, defective Vö sites, and Lewis acidic sites, provoked by the adjacent Pr6O11. Specifically, Vö defects and Ni0 sites promoted the adsorption and activation of LA and H2 molecules, while Lewis acidic sites facilitated the conversion of 4-hydroxypentanoic acid (i.e., the reaction intermediate) to the desired GVL. In addition, the Ni1–PrOy catalyst enabled a facile regeneration via magnetic separation and showed satisfactory reusability.