In its element: Zn(2+) at the M7 site of MFI-type zeolites activates H(2), via ZnH and OH species, and leads to Zn(0) species. The Zn(0) species returns to its original state, a Zn(2+) ion, upon evacuation of the zeolite at 873 K (see picture). The formation of the Zn(0) species is supported by DFT calculations.

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The catalytic activity of nickel ion-loaded mesoporous silica MCM-41 (Ni-M41) for ethene dimerization was investigated as a function of the pore size and the amount of nickel. In addition, the silica wall and the loading of the nickel species were characterized. The Ni-M41 samples with smaller pore size and higher Si/Ni ratio exhibited greater reaction rate constants. The Fourier transform infrared (FT-IR) spectra indicated the formation of 2:1 nickel phyllosilicate-like species along the pore wall. Furthermore, the IR band at approximately 570 cm −1 and the X-ray absorption fine structure (XAFS) spectra indicated the existence of five-membered rings consisting of Si−O on the M41 pore wall in addition to the typical six-membered ones. On the basis of the UV−vis−NIR diffuse reflectance (UV−vis−NIR DR), FT-IR, and XAFS data, we propose that the three-and four-coordinated Ni 2+ ions lie on the five-and six-membered Si−O rings of silica, respectively. Nitrogen monoxide was employed as a probe molecule in the FT-IR and UV−vis−NIR DR experiments and revealed that NO adsorbed as di-and mononitrosyl species on the three-and fourcoordinated Ni 2+ ions. The intensity of the dinitrosyl species on the three-coordinated Ni 2+ ions correlated with the catalytic activity for ethene dimerization. Therefore, the three-coordinated Ni 2+ ions are proposed to act as the active site for the reaction.

In this work, we used both experimental and density functional theory (DFT) calculation methods to examine the mechanism of CH 4 activation taking place on the Zn 2+ ion exchanged MFI-type zeolite (ZnMFI). The heterolytic dissociation of CH 4 on ZnMFI around 300 K was observed experimentally, causing the appearance of IR bands at 3615, 2930, and 2892 cm −1 . The first band can be assigned to the OH stretching vibration associated with the formation of the Brønsted acid site and the latter to the C−H stretching modes ascribable to the −[ZnCH 3 ] + species. Combining the IR spectroscopy with a DFT calculation, it is apparent that the heterolytic C−H bond dissociation of CH 4 has an activation energy of 15 kJ mol −1 and takes place on a monomeric Zn 2+ at the M7S2 site. The M7S2 site has a specific Al arrangement in MFI and exhibits a pronounced reactivity for the H−H bond cleavage of H 2 , even at room temperature. In addition, to our knowledge, we are the first to succeed in explaining the dissociation process of CH 4 by applying natural bond orbital (NBO) and interaction localized orbital (ILO) analyses to the present system; the donation interaction from the CH 4 −σ(C−H) orbital to the Zn−4s orbital triggers the cleavage of the C−H bond of CH 4 under mild conditions.

We produced carbon hybrid materials of graphene sheets decorated with metal or metal oxide nanoparticles of gold, silver, copper, cobalt, or nickel from cation exchanged graphite oxide. Measurements using powder X-ray diffraction, transmission electron microscopy, and X-ray absorption spectra revealed that the Au and Ag in the materials (Au-Gr and Ag-Gr) existed on graphene sheets as metal nanoparticles, whereas Cu and Co in the materials (Cu-Gr and Co-Gr) existed as a metal oxide. Most Ni particles in Ni-Gr were metal, but the surfaces of large particles were partly oxidized, producing a *Corresponding author. Tel/Fax: +81 86 251 7776 E-mail address: kgotoh@cc.okayama-u.ac.jp (K. Gotoh) 2 core-shell structure. The Ag-Gr sample showed a catalytic activity for the oxygen reduction reaction in 1.0 M KOH aq. under an oxygen atmosphere. Ag-Gr is superior as a cathode in alkaline fuel cells, which should not be disturbed by the methanol crossover problem from the anode. We established an effective approach to prepare a series of graphene-nanoparticle composite materials using heat treatment.