title: Identification of Active and Spectator Sn Sites in Sn-β Following Solid-State Stannation, and Consequences for Lewis Acid Catalysis.
abstract: Lewis acidic zeolites are rapidly emerging liquid-phase Lewis acid catalysts. Nevertheless, their inefficient synthesis procedure currently prohibits greater utilization and exploitation of these promising materials. Herein, we demonstrate that SnIV-containing zeolite beta can readily be prepared both selectively and extremely rapidly by solid-state incorporation (SSI) method. Through a combination of spectroscopic (XRD, UV/Vis, X-ray absorption, magic-angle spinning NMR, and diffuse reflectance infrared Fourier transform spectroscopy) studies, we unambiguously demonstrate that site-isolated, isomorphously substituted SnIVsites dominate the Sn population up to a loading of 5 wt % Sn. These sites are identical to those found in conventionally prepared Sn-beta, and result in our SSI material exhibiting identical levels of intrinsic activity (that is, turnover frequency) despite the threefold increase in Sn loading, and the extremely rapid and benign nature of our preparation methodology. We also identify the presence of spectator sites, in the form of SnIVoligomers, at higher levels of Sn loading. The consequences of this mixed population with regards to catalysis (Meerwein-Pondorf-Verley reaction and glucose isomerization) are also identified.
authors.affiliation: Cardiff Catalysis Institute, Cardiff University School of Chemistry Main Building, Park Place, Cardiff, CF10 3AT (UK) E-mail: hammondc4@cardiff.ac.uk.
authors.forename: Ceri
authors.initials: C
authors.lastname: Hammond
authors.affiliation: Cardiff Catalysis Institute, Cardiff University School of Chemistry Main Building, Park Place, Cardiff, CF10 3AT (UK) E-mail: hammondc4@cardiff.ac.uk.
authors.forename: Daniele
authors.initials: D
authors.lastname: Padovan
authors.affiliation: Cardiff Catalysis Institute, Cardiff University School of Chemistry Main Building, Park Place, Cardiff, CF10 3AT (UK) E-mail: hammondc4@cardiff.ac.uk.
authors.forename: Abbas
authors.initials: A
authors.lastname: Al-Nayili
authors.affiliation: UK Catalysis Hub, Research Complex at Harwell Oxon, OX11 0FA (UK) ; Department of Chemistry, University College London Gordon Street, London, WC1H 0AJ (UK).
authors.forename: Peter P
authors.initials: PP
authors.lastname: Wells
authors.affiliation: UK Catalysis Hub, Research Complex at Harwell Oxon, OX11 0FA (UK) ; Department of Chemistry, University College London Gordon Street, London, WC1H 0AJ (UK).
authors.forename: Emma K
authors.initials: EK
authors.lastname: Gibson
authors.affiliation: Cardiff Catalysis Institute, Cardiff University School of Chemistry Main Building, Park Place, Cardiff, CF10 3AT (UK) E-mail: hammondc4@cardiff.ac.uk.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Dimitratos
keywords: Lewis acids; biomass; heterogeneous catalysis; tin; zeolites