Plasmonic Catalysis for Controlling Selectivity in the Hydrogenation of Cinnamaldehyde to Propylbenzene Under Visible‐Light Irradiation

The selective hydrogenation of α,β-unsaturated aldehydes, such as cinnamaldehyde (CAL), into value-added aromatic hydrocarbons like propylbenzene (PPR) remains a formidable challenge due to competing CC and CO hydrogenation pathways. Here, a plasmon-enhanced catalytic strategy employing Au@Au₃Pd core-shell nanoparticles supported on silica is reported. The catalyst features a plasmonic Au core and a 1 nm Au₃Pd alloyed shell (25 at% Pd), enabling light-driven modulation of reaction selectivity. Under visible-light irradiation, the catalyst achieves complete CAL conversion with a ≈34% yield of PPR, corresponding to a 7.7-fold enhancement in turnover frequency relative to dark conditions. Density functional theory calculations reveal that interfacial electronic coupling between the Au core and Pd-rich shell upshifts the Pd d-band center and enhances charge transfer, promoting both CC and CO hydrogenation steps followed by hydrogenolysis to PPR. This study demonstrates a robust approach to overcome selectivity limitations in multifunctional molecule hydrogenation by harnessing localized surface plasmon resonance effects. The insights gained offer a foundation for the rational design of light-responsive bimetallic catalysts for selective and sustainable transformations.