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• VO x and CeO 2 surface speciation on Al 2 O 3 depends on the ALD growth sequence. • The presence of CeO 2 does not impact the electronic structure of the V O bond. • VO x and CeO 2 on Al 2 O 3 migrate at elevated temperatures under reducing conditions. • CeO 2 clusters on Al 2 O 3 and ceria surface sites in VO x /CeO 2 favor total oxidation. • Different active sites on CeO 2 show varying reactivity towards alkane and alkene. Alumina-supported VO x -CeO 2 materials are synthesized by atomic layer deposition (ALD) and evaluated in cyclohexane oxidative dehydrogenation (ODH). The order of deposition of the two metal oxides by ALD influences the size, geometry and oxidation state of the resulting surface species as indicated by Raman spectroscopy coupled with density functional theory (DFT) calculations and XPS. The individual contributions of VO x and CeO 2 surface sites to the cyclohexane ODH reaction mechanism are investigated through a comparison of the catalytic activity of the supported mixed metal oxide materials, VO x /Al 2 O 3 , VO x /CeO 2 and a bare CeO 2 support. The highest activity is observed for CeO 2 , and different surface active sites are distinguished by introducing cyclohexane and cyclohexene in the reactant feed mixture. The catalytic behavior is dependent on the nature of V O S (S, Support) bonds, and small clusters of CeO 2 on Al 2 O 3 favor total oxidation, similar to exposed CeO 2 sites in VO x /CeO 2. [ABSTRACT FROM AUTHOR]

Six first-row transition metal cations (Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ ) were evaluated as catalysts for ethene dimerization to 1-butene. This is an important reaction in the chemistry of C C bond formation and in the conversion of natural gas to higher hydrocarbons. Two related classes of transition metal cation catalysts were investigated: 1) single transition metal cations supported on zirconium oxide nodes of the metal–organic framework NU-1000 and 2) small metal hydroxide clusters with two metal atoms (M 2 ) that could be grown by atomic layer deposition on a support exhibiting isolated hydroxyl groups. Using scaling relations, the free energies of co-adsorbed hydrogen and ethene (i.e., (H/C 2 H 4 )*) and adsorbed ethyl (i.e., C 2 H 5 *) were identified as descriptors for ethene dimerization catalysis. Using degree of rate control analysis, it was determined that the rate controlling steps are either ethene insertion (C C bond forming) or β-hydride elimination (C H bond breaking), depending on the metal. Using degree of catalyst control analysis, it was determined that activity on all the catalysts studied could be improved by tuning the free energy of C 2 H 5 *. [ABSTRACT FROM AUTHOR]

The prospect of using copper oxide nanoclusters grown by atomic layer deposition on a porphyrin support for selective oxidation of methane to methanol was examined by means of density functional theory (DFT) calculations. Ab initio thermodynamic analysis indicates that an active site in the form of Cu(μ-O)Cu can be stabilized by activation in O 2 at 465 K. Furthermore, a moderate methane activation energy barrier (E a  = 54 kJ/mol) is predicted, and the hydrogen abstraction activity of the active site could be attributed to the radical character of the bridging oxygen. Methanol extraction in this system is limited by a thermodynamic barrier to desorption of ΔG = 57 kJ/mol at 473 K; however, desorption can be facilitated by the addition of water in a “stepped conversion” process. Overall, our results indicate similar activity between porphyrin-supported copper oxide nanoclusters and existing Cu-exchanged zeolites and provide a computational proof-of-concept for utilizing functionalized organic linkers in metal-organic frameworks (MOFs) for selective oxidation of methane to methanol. [ABSTRACT FROM AUTHOR]