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Design of hybrid nanomaterials as sustainable heterogeneous oxidation catalysts

Design of hybrid nanomaterials as sustainable heterogeneous oxidation catalysts
Design of hybrid nanomaterials as sustainable heterogeneous oxidation catalysts
Anion exchange properties of a microporous copper chlorophosphate have been exploited to demonstrate, for the first time, a method for generating monodisperse and uncapped noble metal nanoparticles by thermal extrusion. Confirmed initially by structural characterisation with PXRD, SEM and TEM studies, the microporous framework supported Au, Pt and Pd nanoparticles were shown to activate molecular oxygen for the environmentally benign oxidation of benzyl alcohol to benzaldehyde. Probing of the kinetic properties demonstrated contrasting catalytic features for each of the NP catalysts, with the Pt NP catalyst showing heightened activity and a propensity for selectivity toward benzaldehyde.
In-depth physico-chemical analysis of the metal NP catalysts revealed a dependence of the activation/extrusion parameters to the activity and catalytic properties of the resulting materials. Utilising X-ray techniques such as XAS (EXAFS and XANES) and XPS, coupled with the investigation of catalytic properties toward aerobic oxidation of vanillyl alcohol to vanillin, it was established that reduction in the presence of H2 at moderate temperatures is a much more efficient process to calcination in air at much higher temperatures, to afford the complete extrusion of complex anions for active NP formation. Structure-property correlations were harnessed to rationalise the superior catalytic properties of the Pt catalyst compared with the Au and Pd
counterparts, exposing the extent of extrusion and revealing a contrast in the nature of complex anion-support interactions.
To further exemplify the scope of hybrid metal nanoparticle/microporous nanomaterials in the pursuit of new, efficient, green and industrially applicable catalysts, the highly robust UiO-66 type MOFs have been utilised as NP hosts for tandem catalytic applications. A facile method of NP deposition on UiO-66 has been demonstrated using established colloidal synthesis methods with PVP, to generate active Au NP materials for the selective oxidation of cinnamyl alcohol to cinnamaldehyde using simple peroxides. By introducing amine functionality to the MOF with 2-aminoterephthalic acid to form the isoreticular NH2-UiO-66 as a host for Au NPs, an effective catalyst for the two step process involving the aforementioned oxidation with subsequent Knoevenagel condensation reaction (coupling the aldehyde with an activated methylene compound at the –NH2 sites on the MOF) has been achieved in good yield.
Hinde, Christopher
08da9ba4-06f6-433c-a6f9-269441ffa557
Hinde, Christopher
08da9ba4-06f6-433c-a6f9-269441ffa557
Raja, Robert
74faf442-38a6-4ac1-84f9-b3c039cb392b

Hinde, Christopher (2015) Design of hybrid nanomaterials as sustainable heterogeneous oxidation catalysts. University of Southampton, Chemistry, Doctoral Thesis, 290pp.

Record type: Thesis (Doctoral)

Abstract

Anion exchange properties of a microporous copper chlorophosphate have been exploited to demonstrate, for the first time, a method for generating monodisperse and uncapped noble metal nanoparticles by thermal extrusion. Confirmed initially by structural characterisation with PXRD, SEM and TEM studies, the microporous framework supported Au, Pt and Pd nanoparticles were shown to activate molecular oxygen for the environmentally benign oxidation of benzyl alcohol to benzaldehyde. Probing of the kinetic properties demonstrated contrasting catalytic features for each of the NP catalysts, with the Pt NP catalyst showing heightened activity and a propensity for selectivity toward benzaldehyde.
In-depth physico-chemical analysis of the metal NP catalysts revealed a dependence of the activation/extrusion parameters to the activity and catalytic properties of the resulting materials. Utilising X-ray techniques such as XAS (EXAFS and XANES) and XPS, coupled with the investigation of catalytic properties toward aerobic oxidation of vanillyl alcohol to vanillin, it was established that reduction in the presence of H2 at moderate temperatures is a much more efficient process to calcination in air at much higher temperatures, to afford the complete extrusion of complex anions for active NP formation. Structure-property correlations were harnessed to rationalise the superior catalytic properties of the Pt catalyst compared with the Au and Pd
counterparts, exposing the extent of extrusion and revealing a contrast in the nature of complex anion-support interactions.
To further exemplify the scope of hybrid metal nanoparticle/microporous nanomaterials in the pursuit of new, efficient, green and industrially applicable catalysts, the highly robust UiO-66 type MOFs have been utilised as NP hosts for tandem catalytic applications. A facile method of NP deposition on UiO-66 has been demonstrated using established colloidal synthesis methods with PVP, to generate active Au NP materials for the selective oxidation of cinnamyl alcohol to cinnamaldehyde using simple peroxides. By introducing amine functionality to the MOF with 2-aminoterephthalic acid to form the isoreticular NH2-UiO-66 as a host for Au NPs, an effective catalyst for the two step process involving the aforementioned oxidation with subsequent Knoevenagel condensation reaction (coupling the aldehyde with an activated methylene compound at the –NH2 sites on the MOF) has been achieved in good yield.

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Published date: 25 June 2015
Organisations: University of Southampton, Chemistry

Identifiers

Local EPrints ID: 380904
URI: http://eprints.soton.ac.uk/id/eprint/380904
PURE UUID: 9fea347f-4988-4ad5-8164-429ed5889396
ORCID for Robert Raja: ORCID iD orcid.org/0000-0002-4161-7053

Catalogue record

Date deposited: 22 Sep 2015 12:46
Last modified: 30 Jun 2020 04:01

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Contributors

Author: Christopher Hinde
Thesis advisor: Robert Raja ORCID iD

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