With support from the Solid State and Materials Chemistry program in the Division of Materials research, this project will study metal-organic frameworks (MOFs) as a model material system to hierarchically integrate functional molecular and nanoparticle components for solar energy harvesting and storage. Solar energy harvesting provides a long-term solution to meet our future energy needs. Converting solar energy to chemical energy requires a material system to simultaneously perform three fundamental steps: sunlight absorption by antennae to create charge-separated excited states, creation of redox equivalents and their vectorial migration to reactive centers, and catalytic reactions to store chemical energy in the products using vectorially delivered electrons and holes. The research team will develop synthetic methods to hierarchically integrate all of the key functional components into the same system in order to uncover new strategies for solar energy harvesting and storage. They will accomplish these objectives by synthesizing stable and porous photosensitizing MOFs using phosphorescent bridging ligands, incorporating water oxidation catalysts (WOCs) into MOFs to drive photocatalytic water oxidation to generate dioxygen; incorporating proton reduction catalysts (PRCs) into MOFs to drive photocatalytic water reduction to produce H2, and integrating the photosensitizer (PS), WOC, and PRC into the same MOF system to achieve total water splitting with sunlight. Their research efforts have the potential to provide fundamental understanding of photosensitization, charge injection, and water oxidation/proton reduction reactions. The proposed research activities will also be integrated into the training of postdoctoral, graduate, undergraduates, and high school students.
NON-TECHNICAL SUMMARY The sustainable production of energy is one of humanity's greatest scientific challenges. As the fossil fuel supply dwindles, new energy technologies must be developed to meet the increasing global energy needs and to sustain the global society. Solar energy is one of the few alternative energy sources that could be scaled up to meet our future needs. Solar energy can be converted into heat, electricity, or fuels. Among them, solar fuels are the most desirable because of the ease of their storage and transportation. However, practical and cost-effective technologies for ultralarge-scale solar fuel production do not currently exist and require breakthroughs in basic sciences. The research team will use metal-organic frameworks (MOFs) as a model material system to hierarchically integrate functional molecular and nanoparticle components for solar energy harvesting and storage. The proposed research activities will not only provide better understanding of the three fundamental processes involved in solar energy conversion, including photosensitization, charge injection, and water oxidation/proton reduction reactions, but also promise to lead to new and better material systems for solar energy harvesting and storage. The project will involve students from all demographics and will teach skills and techniques that are relevant to real-world needs, thus helping prepare a highly skilled workforce for future clean technology.