Mixed‐Metal MIL‐100(Sc,M) (M=Al,Cr, Fe) for Lewis Acid Catalysis and Tandem CC Bond Formation and Alcohol Oxidation |
| |
| Authors: | Laura Mitchell Patrick Williamson Barbora Ehrlichová Amanda E. Anderson Valerie R. Seymour Sharon E. Ashbrook Nadia Acerbi Luke M. Daniels Richard I. Walton Matthew L. Clarke Paul A. Wright |
| |
| Affiliation: | 1. EaStCHEM School of Chemistry, University of St Andrews, Purdie Building, North Haugh, St.?Andrews, Fife, KY16 9ST (UK), Fax: (+44)?1334‐463808;2. Johnson Matthey Technology Centre, Blount's Court Road, Sonning Common, Reading, RG4 9NH (UK);3. Department of Chemistry, University of Warwick, Coventry, CV4 7AL (UK) |
| |
| Abstract: | The trivalent metal cations Al3+, Cr3+, and Fe3+ were each introduced, together with Sc3+, 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‐Fe2O3 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‐Fe2O3 nanoparticles were also active Lewis acid species, although less active than Sc3+ in trimer sites. The incorporation of Fe3+ into MIL‐100(Sc) imparts activity for oxidation catalysis and tandem catalytic processes (Lewis acid+oxidation) that make use of both catalytically active framework Sc3+ and Fe3+. A procedure for using these mixed‐metal heterogeneous catalysts has been developed for making ketones from (hetero)aromatics and a hemiacetal. |
| |
| Keywords: | bifunctional catalysts heterogeneous catalysis iron scandium tandem catalysis |
|
|
