Rational design of photocatalysts

Photo-redox catalysis has gained a lot of interest due to its potential of performing otherwise difficult chemical conversions and its ability to use visible or near UV light, that can be efficiently generated with LEDs. While it has been demonstrated in a range of applications, there is no clear concept for photocatalyst design and the exact catalyst used in an application appears to be by trial and error rather than guided by understanding and rational design criteria. This project aims at combining modelling and experimental work to design and optimize photocatalyst performance based on the following criteria (among others):

- Light absorption: the energy available for lifting electrons of a substrate into an excited orbital will depend on the energy transferred from the photocatalyst to the substrate and therefore ultimately on the energy absorbed by the photocatalyst.
- Sorption properties (heterogeneous catalysts): The adsorption of a substrate to a heterogeneous photocatalyst is a prerequisite to the energy transfer from the catalyst to the substrate. Assuming that the substrate is then ready to perform the reaction with a second reagent, the sorption properties of the latter to the catalyst surface will affect the reaction pathway and the required catalyst surface. And finally the desorption of the product (or the reagents) from the surface will affect the performance of the catalytic system, as it will free up the surface for the next set of reagent molecules to be converted into product
- Coordination properties (heterogeneous catalysts): The coordination of substrates to photocatalytically active coordination metals will determine, whether a reaction is catalyzed and how the catalytic cycle looks like.
- Electronic properties of the catalytic system: a typical redox photocatalytic system includes one catalyst for the reduction and another one for the oxidation reaction. This entails that electrons can move from the oxidizing catalyst to the site, where the corresponding reduction is to be performed (and to avoid electron-hole recombination). Identifying an appropriate pair of catalysts and combining them in an appropriate way, so the electrons can move as required will be crucial for the performance of the photo-redox-catalytic system. (Note that also mass transport of molecules/ions/moieties will be required to close the catalytic cycle.)
This Ph.D. programme will be looking at the critical aspects of one to three exemplars for redox-photocatalytic systems
- By modelling the above (and significant other) parameters
- By experimentally testing, verifying, refining the models. This will include analyzing the product stream with respect to products and side products and develop concepts for the underlying reaction network.

One goal will include the identification of the rate-/performance-limiting steps or features in a photocatalytic system and suggest measures to improve the effectiveness and efficiency (yield and selectivity, turn-over number, etc.) of the system and suggest appropriate catalyst combinations and formulations,
The programme will aim at leveraging synergies with two other students within React by focusing on one photocatalytic system. One of the students is working on the synthesis and analysis of an oxidizing photocatalyst (Melanie Nutter), the other one (Janusz Siwek) on reactor design and scale up.

Academic impact:
Recent advances in data science and digital technology have a disruptive effect on the way synthetic chemistry is practiced. Competence in computing and data analysis has become increasingly important in preparing chemistry students for careers in industry and academic research.

The CDT cohort will receive interdisciplinary training in an excellent research environment, supported by state-of-the-art bespoke facilities, in areas that are currently under-represented in UK Chemistry graduate programmes. The CDT assembles a team of 74 Academics across several disciplines (Chemistry, Chemical Engineering, Bioengineering, Maths and Computing, and pharmaceutical manufacturing sciences), further supported by 16 industrial stakeholders, to deliver the interdisciplinary training necessary to transform synthetic chemistry into a data-centric science, including: the latest developments in lab automation, the use of new reaction platforms, greater incorporation of in-situ analytics to build an understanding of the fundamental reaction pathways, as well as scaling-up for manufacturing.

All of the research data generated by the CDT will be captured (by the use of a common Electronic Lab Notebook) and made openly accessible after an embargo period. Over time, this will provide a valuable resource for the future development of synthetic chemistry.

Industrial and Economic Impact:
Synthetic chemistry is a critical scientific discipline that underpins the UK's manufacturing industry. The Chemicals and Pharmaceutical industries are projected to generate a demand for up to 77,000 graduate recruits between 2015-2025. As the manufacturing industry becomes more digitised (Industry 4.0), training needs to evolve to deliver a new generation of highly-skilled workers to protect the manufacturing sector in the UK. By expanding the traditional skill sets of a synthetic chemist, we will produce highly-qualified personnel who are more resilient to future challenges. This CDT will produce synthetic chemists with skills in automation and data-management skills that are highly prized by employers, which will maintain the UK's world-leading expertise and competitiveness and encourage inward investment.

This CDT will improve the job-readiness of our graduate students, by embedding industrial partners in our training programme, including the delivery of training material, lecture courses, case studies, and offers of industrial placements. Students will be able to exercise their broadened fundamental knowledge to a wide range of applied and industrial problems and enhance their job prospects.

Societal:
The World's population was estimated to be 7.4 billion in August 2016; the UN estimated that it will further increase to 11.2 billion in the year 2100. This population growth will inevitably place pressure on the world's finite natural resources. Novel molecules with improved effectiveness and safety will supersede current pharmaceuticals, agrochemicals, and fine chemicals used in the fabrication of new materials.

Recent news highlights the need for certain materials (such as plastics) to be manufactured and recycled in a sustainable manner, and yet their commercial viability of next-generation manufacturing processes will depend on their cost-effectiveness and the speed which they can be developed. The CDT graduates will act as ambassadors of the chemical science, engaging directly with the Learned Societies, local council, general public (including educational activities), as well as politicians and policymakers, to champion the importance of the chemical science in solving global challenges.