No abstract

A correlation between ceria reducibility and the precious-metal d-band center is reported for ceria-supported precious-metal catalysts. The results could provide the missing link to fully explain the occurrence of strong metal-support interaction (SMSI) and hydrogen spillover in catalysts that consist of dispersed metals in contact with reducible metal oxides.

Adsorption of H 2 S on the Ni 2 (dhtp)(H 2 O) 2 ·8H 2 O metal-organic framework (known as CPO-27-Ni or MOF-74-Ni) is characterized by in-situ technique (PXRD, FTIR, Raman and Uvvisible spectroscopy) and by first principles periodic boundary conditions calculations.Powder X-ray diffraction results show very high stability of CPO-27-Ni framework in presence of H 2 S. Nevertheless, as evidenced by change in color of the sample from pale yellow to dark green, the adsorption of H 2 S strongly affects the coordination of Ni sites. FTIR results show the reversible molecular adsorption of H 2 S. Experimental and computed energies of interaction reveal good agreement. Quantitative data considering energetic aspects (calorimetric measurements) are also included. This work highlights the fundamentals of H 2 S adsorption onto the CPO-27-Ni framework.

The trivalent metal cations Al(3+) , Cr(3+) , and Fe(3+) were each introduced, together with Sc(3+) , into MIL-100(Sc,M) solid solutions (M=Al, Cr, Fe) by direct synthesis. The substitution has been confirmed by powder X-ray diffraction (PXRD) and solid-state NMR, UV/Vis, and X-ray absorption (XAS) spectroscopy. Mixed Sc/Fe MIL-100 samples were prepared in which part of the Fe is present as α-Fe2 O3 nanoparticles within the mesoporous cages of the MOF, as shown by XAS, TGA, and PXRD. The catalytic activity of the mixed-metal catalysts in Lewis acid catalysed Friedel-Crafts additions increases with the amount of Sc present, with the attenuating effect of the second metal decreasing in the order Al>Fe>Cr. Mixed-metal Sc,Fe materials give acceptable activity: 40 % Fe incorporation only results in a 20 % decrease in activity over the same reaction time and pure product can still be obtained and filtered off after extended reaction times. Supported α-Fe2 O3 nanoparticles were also active Lewis acid species, although less active than Sc(3+) in trimer sites. The incorporation of Fe(3+) into MIL-100(Sc) imparts activity for oxidation catalysis and tandem catalytic processes (Lewis acid+oxidation) that make use of both catalytically active framework Sc(3+) and Fe(3+) . A procedure for using these mixed-metal heterogeneous catalysts has been developed for making ketones from (hetero)aromatics and a hemiacetal.