Synthesis and catalytic application of Pd nanoparticles in graphite oxide

Pd nanoparticles of 1-6 nm were synthesized in graphite oxide (GO) via cation exchange. The synthesis procedure involved immobilization of the precursor Pd(NH3)(4)(NO3)(2) in GO, followed by reduction in flowing H-2. The resulting low-loaded Pd-GO material was characterized by X-ray diffraction (XRD), infrared (IR) spectroscopy and transmission electron microscopy (TEM). Structural characterization revealed that intercalation of the precursor took place in GO and the reduced Pd nanoparticles were situated both on the external surface and in the interlamellar space of the GO lamellae. The catalytic behaviour of Pd-GO was investigated in the liquid-phase hydrogenations of 3-hexyne and 4-octyne under standard conditions. For both reactants, marked turnover frequencies (18-36 s(-1)) and pronounced (Z)-alkene stereoselectivities (93-98.4%) were obtained, indicating that Pd-GO was a highly active and stereoselective catalyst. For the stereoselective hydrogenation of 3-hexyne, Pd-GO exhibited an outstanding catalytic performance: at reactant:Pd (S:Pd) ratios <= 5000, complete conversions were achieved in 8-15 min and the (Z)-alkene stereoselectivities exceeded 98%. (C) 2008 Elsevier Ltd. All rights reserved.