Authors:	Huber, Niklas
Title:	Novel design concepts for visible-light-active semiconductor photocatalysis
Online publication date:	24-Feb-2022
Year of first publication:	2022
Language:	english
Abstract:	The photocatalytic use of visible light represents a sustainable and promising approach for transforming organic synthesis in the 21st century. Inspired by natural systems, various materials have recently been investigated to perform chemical reactions with light. However, the step into the widespread and large-scale application of these materials has not been achieved so far due to versatile reasons. The relevance and value of the reactions performed, the nanostructuring of the materials, the precise control of catalyst properties, the catalyst price, and green solvent compatibility are critical challenges. This work aims to develop new semiconducting materials for efficient heterogeneous photocatalysis of organic redox reactions with visible light. Novel catalyst concepts have been developed that address critical challenges for large-scale and future practical applications. First, the realization of high-value reactions is addressed. Three thiophene-based CTFs with variable-length phenyl linkers could be used for the photocatalytic oxidation of toluene to benzaldehyde with atmospheric oxygen. The performance of selective sp3 -C-H activations is a step towards atom-economical and technically useful photocatalytic reactions. Second, the effects of nanoscaling and molecular fine-tuning through copolymerization on photocatalysts are investigated. CTF nanoparticles are obtained for the first time using a size-controllable confinement synthesis. Together with the admixture of electron-accepting comonomers, significant efficiency gains can be achieved in the investigated [3+2] cycloaddition benchmark reaction. The project highlights the importance of morphological synthesis control and points a way towards dispersible and highly active applied photocatalysts. Third, the significance of controlling electro-optical properties in photocatalytic systems is highlighted. Controlling the thickness of CdSe nanoplatelets at the atomic level allows tuning of the bandgap and photocatalytic efficiency to reduce nitrobenzene to azoxybenzene. In a further project, porous aromatic frameworks are established as a versatile and highly porous platform for photocatalysis. Precise control of the conjugation length within the polymers allows the selective adjustment of frontier orbital potentials. The role of HOMO and LUMO redox potentials in oxidation and reduction strength in C-6 H activations is emphasized. Precise control of electro-optical and structural properties is critical to tailor photocatalytic materials to target applications. Fourth, the reduction of catalyst complexity, as well as synthetic effort and cost, is focused. Copolymerization of a photoactive monomer with MMA provides an efficient heterogeneous photocatalyst for [4+2] visible-light cycloadditions. The system combines the photoactive small molecule's photocatalytic properties with the robustness and chemical constitution of PMMA. The project highlights the importance of creating low-cost and straightforward catalyst platforms that can be easily applied. Fifth, the high relevance of compatibility with green solvents is emphasized. Based on the PMMA platform and variable proportions of a sulfonic acid comonomer, water-compatible photocatalytic polymers to remove pollutants from an aqueous medium could be obtained. Thus, the project represents a step towards biological & environmental applications and promotes sustainable solvents in synthetic practice. Overall, this work is intended to facilitate the broader application of heterogeneous photocatalytic materials and visible-light photocatalysis through its findings.
DDC:	540 Chemie 540 Chemistry and allied sciences
Institution:	Johannes Gutenberg-Universität Mainz
Department:	FB 09 Chemie, Pharmazie u. Geowissensch.
Place:	Mainz
ROR:	https://ror.org/023b0x485
DOI:	http://doi.org/10.25358/openscience-6191
URN:	urn:nbn:de:hebis:77-openscience-bd3be420-c139-4545-8d89-530b5becc1c20
Version:	Original work
Publication type:	Dissertation
License:	In Copyright
Information on rights of use:	http://rightsstatements.org/vocab/InC/1.0/
Extent:	316 Seiten, Illustrationen, Diagramme
Appears in collections:	JGU-Publikationen