Enantioselective hydrogenation of hydroxyacetone on intrinsically chiral Pt(643) surfaces

Abstract

Abstract

Asymmetric catalysis underpins pharmaceutical synthesis, but is dominated by homogeneous molecular catalysts that complicate product separation and recycling. Heterogeneous alternatives, including hybrid systems in which molecular catalysts are immobilised on solid supports, often suffer from diminished activity, poor stability or a limited substrate scope. Here, we use density functional theory and microkinetic modelling to evaluate intrinsically chiral platinum surfaces as a heterogeneous alternative, taking the hydrogenation of hydroxyacetone to 1,2-propanediol (1,2-PD) as a model reaction. On the mirror-image Pt(643) S and Pt(643) R surfaces, hydroxyacetone chemisorbs at the undercoordinated chiral kink, and the effective transition-state barriers for the two reaction pathways differ by 0.21 eV, favouring S -1,2-PD on Pt(643) S and R -1,2-PD on Pt(643) R . By contrast, hydroxyacetone is only physisorbed on the achiral Pt(111) terrace and is hydrogenated to a racemic product with a lower effective barrier of 0.75 eV. Microkinetic modelling that accounts for the realistic coexistence of kink and terrace sites identifies an operational window near 500 K and 10⁻ 2 bar in which strong substrate binding at the chiral kink outcompetes the racemic terrace pathway, yielding enantiomeric excesses approaching 99 %. These results establish chiral Pt(643) surfaces as a viable platform for fully heterogeneous asymmetric hydrogenation and motivate experimental verification.