Design of Core-Pd/Shell-Ag Nanocomposite Catalyst for Selective Semihydrogenation of Alkynes

We designed core-Pd/shell-Ag nanocomposite catalyst (Pd@Ag) for highly selective semihydrogenation of alkynes. The construction of the core-shell nanocomposite enables a significant improvement in the low activity of Ag NPs for the selective semihydrogenation of alkynes because hydrogen is supplied from the core-Pd NPs to the shell-Ag NPs in a synergistic manner. Simultaneously, coating the core-Pd NPs with shell-Ag NPs results in efficient suppression of overhydrogenation of alkenes by the Pd NPs. This complementary action of core-Pd and shell-Ag provides high chemoselectivity toward a wide range of alkenes with high Z-selectivity under mild reaction conditions (room temperature and 1 atm H-2). Moreover, Pd@Ag can be easily separated from the reaction mixture and is reusable without loss of catalytic activity or selectivity.