Breaking the Activity–Stability Trade-Off in Ammonia-Rich Catalysis for Scalable 5-Methyl-2-Pyrrolidinone Synthesis

Breaking the long-standing activity–stability trade-off in ammonia-rich reductive amination of biomass-derived levulinic acid esters (LAEs) has remained a fundamental challenge, primarily due to the strong chemisorption and poisoning effects of ammonia. Here, we report a nickel–boron (NiB-x) catalyst that overcomes this limitation by synergizing high hydrogenation efficiency with high stability under ammonia conditions. The optimized NiB-1 exhibited a turnover frequency as high as 1544.4 h–1, exceeding that of (504.0 h–1) the reported catalytic system with NH3 and NH3·H2O. Scaling the reaction to 100 mL with NH3 as the N-source at 120 °C and 1.5 MPa H2 delivered a 95.1% 5-methyl-2-pyrrolidinone (5-MP) yield at 60.0 wt % substrate concentration, demonstrating industrial viability. Mechanistic studies revealed that the upward shift of the d-band center in the Ni–B sites enhances hydrogen dissociation, stabilizes intermediates via tailored adsorption energetics, and reduces the reaction barrier more efficiently. Furthermore, the versatility of the NiB-1 catalyst was evidenced by the broad applicability to diverse biomass-derived pyrrolidones and nitro compounds hydrogenation under mild conditions. This work resolves the dual challenges of ammonia compatibility and nonprecious metal efficiency, offering a scalable, decarbonized route to heterocycle synthesis.