Interface Confinement in Metal Nanosheet for High-Efficiency Semi-Hydrogenation of Alkynes

Designing high-performance catalysts with high activity and selectivity toward semihydrogenation of alkynes is one of the major goals of fine chemical industry, yet full of challenges due to the difficulties in semihydrogenation of carbon–carbon triple bond (C≡C) to carbon–carbon double bond (C═C) without further hydrogenation. Herein, we demonstrate a two-dimensionality (2D) enhanced interface-confined effect that leads to the strong interaction between lead (Pb) species and the ultrathin 2D palladium nanosheets (Pd NSs). As a result, the catalytic performance of the optimized Pd–Pb NSs in semihydrogenation of phenylacetylene can reach high conversion of 100%, high selectivity of 95.8%, and high activity of 2256 h–1. It can also endure at least six cycles with limited conversion and selectivity decays. Detailed analyses reveal that the interface-confined effect in the 2D system is much stronger than that in the 3D system, making the Pd active sites more electron-deficient with greater positive shift of the binding energy and the weaker adsorption and binding capability of styrene. Such phenomenon disappears readily after destroying the interface structure. Density functional theory calculations further reveal that the confined interfaces cause the higher kinetic energy barriers of overhydrogenation processes of styrene into phenylethane as well as the weaker adsorption of styrene, resulting in the easier removal of styrene without further hydrogenation. More importantly, such 2D enhanced “interface-confined” strategy provides a general platform that achieves high-efficiency semihydrogenation of a board range of alkynes.