title: How strain affects the reactivity of surface metal oxide catalysts.
abstract: Highly dispersed molybdenum oxide supported on mesoporous silica SBA-15 has been prepared by anion exchange resulting in a series of catalysts with changing Mo densities (0.2-2.5 Mo atoms nm(-2) ). X-ray absorption, UV/Vis, Raman, and IR spectroscopy indicate that doubly anchored tetrahedral dioxo MoO4 units are the major surface species at all loadings. Higher reducibility at loadings close to the monolayer measured by temperature-programmed reduction and a steep increase in the catalytic activity observed in metathesis of propene and oxidative dehydrogenation of propane at 8 % of Mo loading are attributed to frustration of Mo oxide surface species and lateral interactions. Based on DFT calculations, NEXAFS spectra at the O-K-edge at high Mo loadings are explained by distorted MoO4 complexes. Limited availability of anchor silanol groups at high loadings forces the MoO4 groups to form more strained configurations. The occurrence of strain is linked to the increase in reactivity.
authors.affiliation: Department of Inorganic Chemistry, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin (Deutschland) http://www.fhi-berlin.mpg.de/
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Amakawa
authors.forename: Lili
authors.initials: L
authors.lastname: Sun
authors.forename: Chunsheng
authors.initials: C
authors.lastname: Guo
authors.forename: Michael
authors.initials: M
authors.lastname: Hävecker
authors.forename: Pierre
authors.initials: P
authors.lastname: Kube
authors.forename: Israel E
authors.initials: IE
authors.lastname: Wachs
authors.forename: Soe
authors.initials: S
authors.lastname: Lwin
authors.forename: Anatoly I
authors.initials: AI
authors.lastname: Frenkel
authors.forename: Anitha
authors.initials: A
authors.lastname: Patlolla
authors.forename: Klaus
authors.initials: K
authors.lastname: Hermann
authors.forename: Robert
authors.initials: R
authors.lastname: Schlögl
authors.forename: Annette
authors.initials: A
authors.lastname: Trunschke
keywords: heterogeneous catalysis; molybdenum; olefin metathesis; oxidation; supported catalysts