Encapsulation of Pt species into MFI zeolite with tunable acid sites boosts reductive amination towards tertiary amines

Noble metal-catalyzed reductive amination of carbonyl compounds using molecular hydrogen is a promising green route for amine synthesis, but a challenge remains to boost the atomic efficiency of noble metal species. Herein, MFI zeolite encapsulated Pt species with tunable Si/Al ratios were synthesized to allow the formation of Pt nanoparticles (NPs) with almost the same loading amount, particle size, and electronic state. Confining Pt NPs allows the spatial satisfaction for the synergy of metal centers and acid sites, and Pt@ZSM-5(100) with a moderate Si/Al ratio performed high efficiency in the conversion of carbonyl compounds and boosted high TOF of 23,409 h⁻¹ in reductive amination of benzaldehyde. Combined with structure refinement, x-ray absorption fine structure (XAFS), in situ Fourier transforms infrared (FTIR) spectroscopy, and theoretical calculation, the study indicated that modulating the Si/Al ratio enables the fine rationalization of the microenvironment. The moderate Si/Al ratio causes suitable acid intensity that significantly contributes to the carbonyl compound activation and product desorption.