transformation of Pd to metal-metalloid alloy PdB for alkyne semi-hydrogenation.

In this work, we report alumina-supported metal-metalloid alloy nanoparticles (PdB/AlO) as highly efficient alkyne semi-hydrogenation catalysts. The mentioned catalysts contain orthorhombically distorted PdB nanoparticles and were prepared by transformation of Pd/AlO with borane dimethylamine complex by a solvothermal method. The synthesized PdB/AlO demonstrated greatly enhanced semi-hydrogenation performance. Under reaction conditions of 30 °C, 0.1 MPa of H and a substrate/Pd molar ratio of 1000/1, the conversions of 3-hexyne-1-ol could reach 99.8% in 15 min with a yield of -3-hexen-1-ol of 93.3%. Importantly, the alkene and to -alkene selectivity only slightly decreases with an extended reaction time, showing the inhibition of deep hydrogenation. Experimental studies and density functional theory calculations indicate that the catalytic enhancement is originated from the formation of PdB alloy, which alters the electronic and geometric properties of surface species, thus suppressing the deep hydrogenation with the enhanced alkene selectivity.