Surface Supported Frustrated Lewis Pairs (FLPs) for Small Molecule Activation and Catalysis

Lead Research Organisation: University of Oxford
Department Name: OxICFM CDT

Abstract

Catalysts are substances which speed up reactions by lowering the amount of energy required for them to occur. Whilst we don't necessarily think about them often in everyday life, they are all around us; from catalytic converters in car exhaust pipes reducing toxic emissions, to enzymes facilitating life essential metabolic processes in our bodies. A catalytic converter is an example of a heterogeneous catalyst i.e. one where the products are in a different physical state to the catalyst, whilst enzymes are considered homogeneous catalysts - the products and the catalyst are in the same state (usually both liquids). Many of the industrial systems we rely upon in the modern world employ a group of elements known as the transition metals as homogeneous catalysts. In much the same way as it would be difficult to separate the milk from your tea once mixed, removing homogeneous catalysts from the product mixture is a considerable challenge. This is further complicated by the fact that even a small amount of residual metal is a highly undesirable contaminant in applications, especially medicine.
In the past 14 years, a family of compounds known as FLPs (Frustrated Lewis Pairs) have been developed as transition metal free alternatives to traditional catalysts. FLPs initially caught attention due to their ability to reversibly split the strong bond between hydrogen atoms (referred to as activating hydrogen). Breaking this bond is a prerequisite for catalysis using hydrogen so investigation of these activation processes is vital for catalyst design. To put hydrogen activation in different terms, imagine that in your body's resting state the palms of your hands are superglued together. Only if the glue seal is washed away with some substance are you able to pick up many different objects rather than be constrained to the other palm. Now, imagine that after picking up objects and modifying them to your desires, you are able to recreate and break the seal at will over and over again using the washing substance. This is essentially the process of hydrogen activation where your hands are the hydrogen atoms and the wash an FLP. Think about how many different vital tasks you are able to complete with your hands - suddenly an analogous chemical process seems important.
Whilst the main body of work on hydrogen splitting has focussed on homogenous systems, attempts to create heterogeneous FLPs are becoming more common as this would solve both issues with obtaining pure product: separation from catalyst and presence of metal impurities. In this project, we will first focus on broadening our understanding of an FLP which has potential catalytic capability. We will then aim to attach it to a surface support called an LDH (Layered Double Hydroxide) to make the system heterogeneous. LDHs have been chosen as the surface as they have been well studied and are easily made. This project falls within the EPSRC 'manufacturing the future' research area.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/S023828/1 01/04/2019 30/09/2027
2329455 Studentship EP/S023828/1 01/10/2019 30/09/2023 Aisling Roper