Catalytic reactions are indispensable tools in modern organic synthesis with unmatched selectivity and functional group compatibility compared to traditional organic chemistry However, many catalytic reactions in academia are not suitable for industrial application in High Value Chemical Manufacture (HVCM). Research in our group focuses on utilising mechanistic understanding and reaction engineering to address these challenges. There are several major undertakings in the group:
1. Development of improved catalysts which can readily be produced and applied on scale.
2. Suppressing catalyst deactivation in synthetically important reactions to decrease catalyst loading and increase catalytic efficiency.
3. Effective immobilisation of homogeneous catalysts to ‘smart polymers’ for sustainable processes.
4. Development of sustainable processes for CO2 utilisation using biomass-based chemicals.
Our common research tools include spectroscopic techniques, physical organic structure-reactivity relationships, kinetic tools and models, electrochemical techniques, catalysis development.
Examples of some specific projects are described below.
XAFS as a mechanistic tool in catalysis
X-ray Absorption Fine Structure Spectroscopy (XAFS) is a synchrotron-based spectroscopic technique which has recently found more and more applications in homogeneous systems. It offers unparalleled insights into the nature of transition metal intermediates under realistic catalytic conditions.
We recently reported (doi: 10.1021/om300030e) a mechanistic investigation into the deactivation of a robust immobilised catalyst for transfer hydrogenation from Yorkshire Process Technology. Immobilisation is an important strategy in converting synthetic catalysts in academia, which are often expensive, into recyclable catalysts for industrial applications. Common deactivation pathways such as metal leaching and ligand exchange, however, often cause immobilised catalysts to lose their catalytic activity much more quickly than desired. In this study, a highly novel combination of XAFS at Ir L-edge, Cl K-edge and K K-edge led to a complete characterisation of the deactivated catalyst, which was caused by ligand exchange between chlorides and alkoxides over time. Strategy to reactivate the catalyst and suppress catalyst deactivation was subsequently developed based on these insights.
Electrochemical flow-cell for production of catalysts on-demand
Through collaborations with other research groups in fluid dynamics and inorganic chemistry, we developed an extremely efficient and scalable electrochemical flow-cell which can effect the conversion of imidazoliums and a copper electrode to Cu-NHC catalysts (NHC = N-heterocyclic carbene) in very high yields. The purity of the Cu-NHC catalysts is sufficient to allow direct ‘dispensing’ of the catalyst solution to catalytic reactions, when required, with no detectable change in catalytic activity and selectivity compared to using the purified catalysts. This will enable rapid catalytic screening, as well as catalyst top-up (coupled with computer controlled reactors) in the near future.
The technology can be applied to a wide range of ligands beyond NHCs.
Carbon dioxide activation and utilisation
Research in the group investigated the ‘activation’ of CO2 using guanidine/amidines catalysts and the subsequent catalytic reactions between CO2 and propargylamines. Factors controlling the complexation between amines and CO2 and catalytic activity have been carefully examined using a range of physical organic chemical techniques. This had led to a 10 times increase in the performance of the catalytic system at low loading using a much cheaper catalyst (doi: 10.1039/C4CY00480A).