UC Berkeley

Industrialization and urbanization have encouraged rapid population increases, improved standards of living, access to education, and advanced technological development in large economies across the globe. Simultaneously, these events have strained our natural resources, which over time has drawn attention to their scarcity as well as the secondary environmental consequences of their exploitation. In particular, the combustion of fossil fuels, a non-renewable source of energy, is directly correlated to increased concentrations of atmospheric greenhouse gases such as carbon dioxide (CO2). Since the beginning of industrialization, we have monitored rising anthropogenic carbon dioxide and the resulting effects of increased global surface temperatures, including stronger and more frequent heat waves, droughts, wildfires, and hurricanes. Changes to the Earth’s climate disproportionately affect marginalized communities such as people of color, non-European immigrants, people with disabilities, and low-income groups— as well as populations outside of the Western purview, such as the Philippines, Madagascar, and India. In light of this, scientists are propelled to develop alternatives to petroleum-based energy sources, especially those with carbon-neutral footprints. The capture of atmospheric CO2 and its conversion to chemicals currently derived from petroleum is under investigation as an approach to remove CO2 pollution while providing a net-zero carbon source. The goal of this thesis is to study the use of artificial photosynthesis, specifically, molecular photocatalysis and electrocatalysis, to study the CO2 reduction reaction (CO2RR) as a method of transforming CO2 into useful chemical feedstocks using sustainable energy inputs such as electricity, which can be derived from wind or solar power. To understand and optimize molecular systems with atomic-level tunability in their activity towards CO2RR, our work involves the investigation of primary and secondary coordination sphere modifications to molecular catalysts based on transition metal complexes of polypyridine and supramolecular porphyrin ligands. The ability to modulate both the primary and secondary coordination sphere of molecular species provides insight into the fundamental properties that are important in optimizing selectivity and rates in electro- and photocatalysts for CO2RR. We hope this work highlights the value of molecular chemistry in the future development of large-scale CO2 capture and conversion for sustainable and renewable energy.