Exploring New Catalysts for Photocatalytic Carbon Dioxide Reduction Using Homogeneous Transition Metal Complexes

Abstract

The increase of the carbon dioxide concentration in the atmosphere provides a strong impetus to discover new catalysts that are able to reduce CO2. The reduction processes of this greenhouse gas CO2 have recently received enormous efforts in the research area. The objective of this thesis was the photocatalytic reduction of CO2 that is known as an artificial photosynthesis using visible light, and the objective of the thesis was to study the ability and efficiency of different new molecular catalysts towards CO2 reduction. The goals of the thesis are to design and characterize new catalysts that have high efficiency for the catalytic reduction of CO2. After a brief introduction in Chapter 1 about the photocatalytic reduction of CO2, a different catalyst is presented in each chapter with their characterization and examination for the photocatalytic reduction of CO2. In addition, these presented catalysts were also examined for the electrocatalytic reduction of CO2, but they show a good catalytic behavior in the photocatalytic reduction of CO2. The catalytic mechanisms were also suggested for each catalyst and tried to be confirmed by many different experiments. observed to be highly influenced by CO2 concentration. These newly discovered catalysts are based on transition metal complexes that are able to be good catalysts for the photocatalytic CO2 reduction. These new transition metal complexes have been synthesized, characterized and examined for their catalytic reactivity for CO2 reduction. As presented in Chapter 2, new manganese and rhenium ccomplexes bearing a phosphino-amino-pyridine ligand were synthesized, characterized and showed their photocatalytic ability for CO2 reduction. In addition, Chapter 3 presents new Ru catalysts supported by an unprecedented ligand array and documented their photocatalytic ability towards CO2 reduction. Moreover, Chapter 4 focuses on new Zn(II) complexes that are novel catalysts in the photocatalytic CO2 reduction area. Furthermore, Chapter 5 presents a new environment for Re photocatalyst that has the switch in product to formic acid compare to all other reported Re photocatalysts. On the other hand, Chapter 6 shows new dimers and monomers for a series of earth-abundant transition metal dibromide complexes supported by a neutral SNS ligand framework and reveals their applications in the catalysis. Finally, Chapter 7 presents a brief conclusion and a number of future directions. The attempts to explore and discover the new catalysts for CO2 reduction were exciting, successfully and resulted in the discovery of new catalysts. These catalysts show their good ability to reduce carbon dioxide (CO2) to more valuable products such as carbon monoxide (CO) and formic acid (HCOOH).