Ruthenium-Based Nanoparticles-Loaded Layered Silica Nanosheets-Assembled Stacked-Structure Nanoreactors for Efficient Production of Biomass-Based Pyrrolidinones

Pyrrolidones are a kind of versatile high-end chemicals used as drug intermediates, bioactive molecules, and organic solvents. Reductive amination of biomass-derived levulinic acid and esters to pyrrolidones is one of the most important routes for the production of biomass-based N-containing chemicals. In this paper, Ru-based nanoparticle-loaded layered silica nanosheets (LSNs) were developed as new-type stacked-structure nanoreactors for the efficient reductive amination of biomass-derived levulinates (EL) into 5-methyl-2-pyrrolidones (5-MPs). Using ammonium formate as both a hydrogen and amine source, a complete EL conversion, near-quantitative yield of 5-MPs, and a high productivity of 997 h^–1 could be achieved over Ru₁Co₁@LSNs nanoreactors under optimized conditions. Mechanistic studies from liquid ¹H NMR, in situ difference Fourier transform infrared (FTIR), and density functional theory (DFT) calculations suggest that the synergistic Lewis acid sites and metal sites favor the rapid formation of imine intermediates and subsequent imine hydrogenation. Molecular dynamics simulations show that EL molecules tended to diffuse in an orderly manner and increase in concentration in the near-surface region due to the space-confinement effects of the stacked structure, thus improving the catalytic efficiency. The nanoreactors developed herein may contribute to the development of multifunctional nanoreactors for valorization of renewable carbon-based resources for production of N-containing chemicals.