title: Mixed-metal MIL-100(Sc,M) (M=Al, Cr, Fe) for Lewis acid catalysis and tandem C-C bond formation and alcohol oxidation.
abstract: 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.
authors.affiliation: EaStCHEM School of Chemistry, University of St Andrews, Purdie Building, North Haugh, St. Andrews, Fife, KY16 9ST (UK), Fax: (+44) 1334-463808.
authors.forename: Laura
authors.initials: L
authors.lastname: Mitchell
authors.forename: Patrick
authors.initials: P
authors.lastname: Williamson
authors.forename: Barbora
authors.initials: B
authors.lastname: Ehrlichová
authors.forename: Amanda E
authors.initials: AE
authors.lastname: Anderson
authors.forename: Valerie R
authors.initials: VR
authors.lastname: Seymour
authors.forename: Sharon E
authors.initials: SE
authors.lastname: Ashbrook
authors.forename: Nadia
authors.initials: N
authors.lastname: Acerbi
authors.forename: Luke M
authors.initials: LM
authors.lastname: Daniels
authors.forename: Richard I
authors.initials: RI
authors.lastname: Walton
authors.forename: Matthew L
authors.initials: ML
authors.lastname: Clarke
authors.forename: Paul A
authors.initials: PA
authors.lastname: Wright
keywords: bifunctional catalysts; heterogeneous catalysis; iron; scandium; tandem catalysis