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[Display omitted] • Hydrogenation of conjugated C = O is thermodynamically unfavored. • Highly dispersed Pt nanoparticles are well-embedded within S-1 microchannel. • Confinement effect of S-1 is employed to improve unsaturated alcohol selectivity. • C = O group is preferentially adsorbed on Pt@S-1 via on-top η 1 mode. • The on-top η 1 adsorption mode is more favored to C = O hydrogenation than d i -σ CO η 2. The issue for thermodynamically favored C = C hydrogenation needs to be overcome in the hydrogenation of ɑ, β-unsaturated aldehydes to unsaturated alcohols. Herein, we employ confinement effect in the catalyst-designing engineering to orient the C = O adsorption by the zeolitic microchannel, where highly dispersed Pt nanoparticles are homogeneously well-embedded within the silicalite-1 framework (Pt@S-1). Comprehensive characterizations, such as HAADF-STEM, H 2 -TPR, FT-IR of CO adsorption and XPS are carried out to demonstrate the geometric, confinement and electronic properties of metal species. In the hydrogenation of ɑ, β-unsaturated aldehydes with suitable molecular size, Pt@S-1 displays preferential C = O hydrogenation. For example, Pt@S-1 gives conversion of 99.8% and meanwhile the aiming cinnamal alcohol selectivity of 98.7% in the hydrogenation of cinnamaldehyde, outperforming larger Pt nanoparticles ill-suitedly embedded within silicalite-1 (Pt@S-1- is) and highly dispersed Pt nanoparticles supported on the silicalite-1 surface (Pt/S-1). For the hydrogenation of smaller 3-methyl-2-butenal, though the confinement effect boosts the C = O hydrogenation to some extent, the synergetic electronic effect via introducing Fe species effectively increases the unsaturated alcohol selectivity. Investigations on the adsorption configuration by in-situ FT-IR spectroscopy clearly indicate that the unsaturated aldehyde with suitable molecular size is preferentially adsorbed on Pt sites of Pt@S-1 via the oxygen atom of C = O with on-top η 1 mode, thus favoring high unsaturated alcohol selectivities, while the d i -σ CO η 2 and η 4 adsorption modes on Pt@S-1- is and Pt/S-1 are relatively adverse for prioritized C = O hydrogenation. [ABSTRACT FROM AUTHOR]