Carbon dots as sustainable photocatalysts for organic synthesis

As easily scalable, cost-effective and environmentally benign materials, carbon dots (CDs) have the potential to replace costly or harmful photocatalysts for a range of synthetically relevant transformations. This dissertation aims to establish CDs as versatile, sustainable photocatalysts for organic synthesis. Chapter 2 explores CDs as photocatalysts for net-oxidative and redox-neutral C-C bond formation. A variety of aromatic substrates and biological motifs were successfully trifluoromethylated under aerobic conditions. To utilise the full potential of this reaction, the net-oxidative trifluoromethylation was coupled to H₂-evolution, thereby generating two products simultaneously: a trifluoromethylated aryl and feedstock for hydrogenation. Chapter 3 subsequently introduces CDs as photocatalysts for net-reductive reactions by example of dehalogenation of aryl-iodides, -bromides and -chlorides. The C-halogen bond was successfully cleaved for all three substrate groups despite the strong reduction potential required particularly for the bromides and chlorides. As the CD reduction potential, while appreciable, is not sufficient to drive some of these reactions, mechanistic studies were undertaken to illuminate possible reaction pathways. Chapter 4 expands the application of CDs to C-C bond formation reactions that are currently difficult to access without transition metal catalysts or under visible light irradiation. The examples in this chapter include cross-coupling of 1,4-Dicyanobenzene with aldehydes and ketones as well as pinacol coupling of aldehydes and ketones. Chapter 5 branches out to dual catalytic systems by using CDs in combination with a Ni-catalyst to perform cross-couplings to achieve C-O and C-N bond formation. Additionally, photoluminescence quenching and transient absorption studies were undertaken to further examine the interaction between the CDs and Ni-catalyst, as well as gain insight into the CD states involved in the reaction. The data suggests the possible involvement of an energy transfer pathway, which would be the first example of CDs as an energy transfer catalyst in organic photocatalysis.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2023

Author dc:creator

• Lage, Ava

Advisor dc:contributor.advisor

• Reisner, Erwin

• Carbon dots
• Photocatalysis
• Sustainability
• Synthesis

Licence

• https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/6c5cc226-2bdf-41b1-aff0-9dbd7f3131b1/download
• https://www.rioxx.net/licenses/all-rights-reserved/

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.106482

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/365046