Chemoselective Hydrogenation of Cinnamaldehyde over a Pt-Lewis Acid Collaborative Catalyst under Ambient Conditions

A novel Pt-Lewis acid collaborative catalyst system for selective hydrogenation of cinnamaldehyde is developed. The Pt/MIL-101 catalyst is able to efficiently catalyze the selective hydrogenation of the C═C group in cinnamaldehyde to hydrocinnamaldehyde at atmospheric pressure and room temperature with >99.9% selectivity at conversions >99.9%. The remarkably enhanced catalytic activity and selectivity of Pt/MIL-101 can be attributed to the synergism effect between highly dispersed Pt and Lewis acid sites. In situ ATR-IR spectroscopic studies and reaction results demonstrated that the Lewis acid sites on MIL-101 suppressed the reactivity of the C═O bond in cinnamaldehyde while enhancing the hydrogenation activity of the conjugated C═C bond through a strong interaction with the C═O bond, which subsequently inhibited the consecutive hydrogenation of the produced hydrocinnamaldehyde. The kinetic parameters of cinnamaldehyde hydrogenation over the Pt/MIL-101 catalyst were investigated, and a kinetic model was established based on the reaction mechanism and compared with experimental observations.