Synthetic Approaches Towards 3rd Generation, Light-Harvesting Metal-Organic Frameworks for Photo-Electrocatalytic Energy Conversions

Abstract

Society?s increasing energy requirements as well as evident climate change problems present humanity with significant scientific challenges. Switching to more renewable energies sources such as the high density, carbon-free energy carrier H2 offers society with a viable alternative and a way to address the issues associated by the usage of fossil fuels. However, existing H2 manufacturing technologies are unfortunately both costly and unviable. Solar H2O splitting is a promising method for producing abundant H2 in a sustainable manner. Nevertheless, the absence of effective, low-cost catalysts for the endergonic, proton-coupled 4 electron oxygen evolution half-reaction (OER) is impeding progress in the field of solar H2O splitting. Therefore, to fulfil society?s energy demands in an environmentally responsible way, it is critical to develop efficient H2O oxidation catalysts (WOCs). Current WOCs generally demonstrate low activity or instability. While many advanced catalysts depend on expensive rare-earth elements. Metal-organic frameworks (MOFs) are metallo-supramolecular materials that are composed of metal-containing units linked by organic ligands. This emerging class of materials features well-defined cavities and remarkable surface areas. Additionally, they possess the ability to incorporate photoactive and redox-active components within their frameworks. As a result, MOFs provide promising platforms for the development of advanced materials that may be used in a wide range of applications. Thus, MOFs are regarded as potentially efficient WOCs. Similarly, MOFs for light-driven transformations and energy technologies such as photocatalytic converters and fuel cells, have particularly received a lot of research attention. This thesis aims to prepare and synthesise a variety of novel photoactive metallo-ligands and subsequently novel MOFs with photoactive capabilities that can be exploited in light driven chemical transformations and related applications. The results presented in this thesis include the synthesis and structural, photophysical and photochemical characterisations of several novel photoactive materials. Additionally, an alternative synthetic strategy was developed, in which electrochemical techniques were utilised to produce thin films of photoactive MOFs on conductive surfaces. Furthermore, the investigation of these hybrid organic-inorganic systems as photoactive catalysts for artificial photosynthetic applications is outlined.