Catalysis plays an essential role in physiology, nature, and the production of chemicals and fuels. Research in my group is situated at the interface of chemistry and chemical engineering, and focuses on the development and application of new heterogeneous catalysts for the production of energy and chemicals. Typically, a combination of crosscutting techniques is utilised in order to prepare novel (improved) and highly selective materials for new (established) catalytic processes. In depth kinetic and mechanistic analysis of the synthesised catalysts is combined with in situ spectroscopic analysis and theoretical models of the catalytic active sites, with the aim of developing i) molecular-level structure-activity relationships, and subsequently ii) tailor-made heterogeneous catalysts that are more active and selective on a macroscopic scale. In general, our research is focused on the fields of selective oxidations – particularly with more sustainable oxidants such as H2O2 and O2 – and acid catalysis, with C1-building blocks, alkanes, and bio-renewable substrates representing the starting molecules of interest.
1. Development of heterogeneous catalysts
A major focal point of our research is the synthesis and development of highly active, heterogeneous catalysts, such as metal (oxide) nanoparticles, and in particular structured solid catalysts such as zeolites, zeotypes, HPAs, POMs, MOFs, and ZIFs, principally containing Lewis acidic or redox active heteroatoms. These materials offer an exciting opportunity to tune and tailor a number of catalytic functionalities, such as redox activity, acid-base properties, Lewis and/or Brønsted acid ratio, and pore architecture, each of which can have a profound impact on the catalytic process of interest. Principally, we are interested in:
a) The application of these materials as liquid phase acid and/or oxidation catalysts (see 2)
b) Investigating the influence of composition and architecture on the speciation and reactivity;
c) Utilising these materials as functionalised supports/matrices for metal (oxide) nanoparticles and biological catalysts;
d) The utilisation of inorganic nanoparticles for anti-cancer and MRI nanotherapeutics;
e) The scale-up of inorganic materials.
2. Advanced catalytic processes
a) The activation and functionalisation of inert C-H bonds remains one of the most elusive targets in catalysis, particularly with the discovery of new natural/shale gas reserves. Our research in this area focuses on the functionalisation of lower-to-mid alkanes with heterogeneous catalysts for fine- and bulk-chemical applications.
b) The selective oxidation of organic molecules is one of the most fundamentally important chemical processes across all levels of the value chain, and is one of the key methods of functionalising molecules for further application. Research in our group focuses on the development and optimisation of sustainable oxidation processes.
c) Naturally occurring metalloenzymes typically possess a transition metal centre, and are able to perform selected catalytic reactions with ease, under mild reaction conditions, and with exquisite chemo- and stereo-selectivity. Understanding the chemistry of these metalloenzymes, and subsequently tailoring inorganic materials that are able to mimic them is a key challenge of fundamental and practical relevance. In addition, our group focuses on the immobilisation and/or encapsulation of naturally occurring metalloenzymes, to produce hybrid biological-inorganic heterogeneous catalysts for catalytic processes.
d) The dwindling supply of crude oil, coupled with the increasing awareness of its polluting nature and environmental impact, necessitates an optimisation of existing technologies, and the development of alternative and more sustainable routes to the major building blocks of the chemical industry. Our research in this area focuses on the valorisation of alternative feedstock (methane/shale gas, bio-renewable substrates, CO2, water) for the production of chemicals and fuel.
3. In situ spectroscopic characterisation of solid materials
The heterogeneous catalysts produced within our group are concurrently thoroughly characterised by a number of (in situ) spectroscopic techniques, in order to obtain a (semi)quantitative overview of the number and types of active species present within the material. Typical laboratory techniques such as FT-IR, UV-Vis, Raman, XRD, XPS, BET, MAS-NMR, TPDRO and chemisorption studies, are coupled with higher-end synchrotron based techniques at the Harwell campus, such as XAS, inelastic neutron scattering and neutron diffraction, in order to gain a complete picture over the molecular-level speciation of the active sites in the catalyst. The purpose of this research is to gain an understanding of the structure of the catalyst at various stages of its lifetime (fresh, pre-treated, in operation, deactivated), and thereby allow correlation of various kinetic phenomena to structural facets of the catalyst i.e. to allow the development of structure-activity relationships. Recent work has specifically focused on the utilisation of Resonance Enhanced Raman spectroscopy to study i) heteroatom-substituted zeolites, and ii) the activity of heterogeneous materials for aqueous phase catalytic processes.