Metal organic frameworks (MOFs) are a class of porous organic-inorganic crystalline materials that have attracted much attention as H storage devices and catalytic supports. In this paper, the synthesis of highly-dispersed Ni nanoparticles (NPs) for the hydrogenation of olefins was achieved by employing Ni-MOF-74 as a precursor. Investigations of the structural transformation of Ni species derived from Ni-MOF-74 during heat treatment were conducted. The transformation was monitored in detail by a combination of XRD, in situ XAFS, and XPS measurements. Ni NPs prepared from Ni-MOF-74 were easily reduced by the generation of reducing gases accompanied by the decomposition of Ni-MOF-74 structures during heat treatment at over 300 °C under N flow. Ni-MOF-74-300 exhibited the highest activity for the hydrogenation of 1-octene due to efficient suppression of excess agglomerated Ni species during heat treatment. Moreover, Ni-MOF-74-300 showed not only high activity for the hydrogenation of olefins but also high size-selectivity because of the selective formation of Ni NPs covered by MOFs and the MOF-derived carbonaceous layer.

Realizing accurate control of catalytically active centers on solid surfaces is one of the most essential goals in the development of functionalized heterogeneous catalysts. Controlled synthesis of carbon-supported Co catalysts from single-site to nanoparticles can be successfully achieved by the structural transformation of the deposited Co(salen) complex precursor under heat treatment. The obtained structures were characterized using techniques such as XRD, in situ XAFS, and TEM. The first decomposition of the Co(salen) complex is initiated by the dissociation of Co-O-C bonds at around 250 °C, which produces isolated single-atom Co species while retaining the Co-N-C bonds even up to 400 °C. When the heat treatment temperature exceeds 450 °C, the second decomposition of the Co-N-C bonds occurs to form Co oxide nanoclusters followed by the growth of Co NPs upon further increase of the heat treatment temperature. The single-site catalyst is highly dispersed and electronically deficient owing to the interaction with the carbon support, and shows activity and selectivity for the oxidation of ethylbenzene, as compared to the inherent Co(salen) complex and nanoparticle catalysts.

To enhance the catalytic activity in a selective one-pot oxidation using in-situ generated H(2)O(2), a hydrophobically modified core-shell catalyst was synthesized by means of a simple silylation reaction using the fluorine-containing silylation agent triethoxyfluorosilane (TEFS, SiF(OEt)(3)). The catalyst consisted of a Pd-supported silica nanosphere and a mesoporous silica shell containing isolated Ti(IV) and F ions bonded with silicon (SiF bond). Structural analyses using XRD and N(2) adsorption-desorption suggested that the mesoporous structure and large surface area of the mesoporous shells were retained even after the modification. During the one-pot oxidation of sulfide, catalytic activity was enhanced significantly by increasing the amount of fluorine in the shell. A hydrophobic surface enhanced adsorption of the hydrophobic reactant into the mesopore, while the less hydrophobic oxygenated products efficiently diffused into the outside of the shell, which improved the catalytic activity and selectivity. In addition, the present methodology can be used to enhance the catalytic activity and selectivity in the one-pot oxidation of cyclohexane by using an Fe-based core-shell catalytic system.

Carbon-supported Pd–Co catalysts prepared by galvanic replacement were proven to be active for the selective hydrogenation of phenylacetylene.