title: Tunable gold catalysts for selective hydrocarbon oxidation under mild conditions.
abstract: Oxidation is an important method for the synthesis of chemical intermediates in the manufacture of high-tonnage commodities, high-value fine chemicals, agrochemicals and pharmaceuticals: but oxidations are often inefficient. The introduction of catalytic systems using oxygen from air is preferred for 'green' processing. Gold catalysis is now showing potential in selective redox processes, particularly for alcohol oxidation and the direct synthesis of hydrogen peroxide. However, a major challenge that persists is the synthesis of an epoxide by the direct electrophilic addition of oxygen to an alkene. Although ethene is epoxidized efficiently using molecular oxygen with silver catalysts in a large-scale industrial process, this is unique because higher alkenes can only be effectively epoxidized using hydrogen peroxide, hydroperoxides or stoichiometric oxygen donors. Here we show that nanocrystalline gold catalysts can provide tunable active catalysts for the oxidation of alkenes using air, with exceptionally high selectivity to partial oxidation products ( approximately 98%) and significant conversions. Our finding significantly extends the discovery by Haruta that nanocrystalline gold can epoxidize alkenes when hydrogen is used to activate the molecular oxygen; in our case, no sacrificial reductant is needed. We anticipate that our finding will initiate attempts to understand more fully the mechanism of oxygen activation at gold surfaces, which might lead to commercial exploitation of the high redox activity of gold nanocrystals.
authors.affiliation: School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, UK.
authors.forename: Mathew D
authors.initials: MD
authors.lastname: Hughes
authors.forename: Yi-Jun
authors.initials: YJ
authors.lastname: Xu
authors.forename: Patrick
authors.initials: P
authors.lastname: Jenkins
authors.forename: Paul
authors.initials: P
authors.lastname: McMorn
authors.forename: Philip
authors.initials: P
authors.lastname: Landon
authors.forename: Dan I
authors.initials: DI
authors.lastname: Enache
authors.forename: Albert F
authors.initials: AF
authors.lastname: Carley
authors.forename: Gary A
authors.initials: GA
authors.lastname: Attard
authors.forename: Graham J
authors.initials: GJ
authors.lastname: Hutchings
authors.forename: Frank
authors.initials: F
authors.lastname: King
authors.forename: E Hugh
authors.initials: EH
authors.lastname: Stitt
authors.forename: Peter
authors.initials: P
authors.lastname: Johnston
authors.forename: Ken
authors.initials: K
authors.lastname: Griffin
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Kiely