A plasmonic Au@Au₃Pd catalyst that integrates visible-light-driven hot electron generation with bimetallic electronic tuning to steer the selective hydrogenation of cinnamaldehyde toward propylbenzene is reported. Localized surface plasmon resonance excitation modulates reaction pathways on tailored Au–Pd interfaces, enabling product selectivity under mild conditions.

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.