Interacting electrons in porous framework photocatalysts

Interacting electrons are inherently present in any system with more than one electron, and are crucial to every step of photocatalysis. The large voids in porous frameworks together with their atomic composition may lead to weak dielectric screening of electron interaction, thus modulating optoelectronic properties. In a broader sense, interaction between electrons and lattice vibrations (phonons) may cause further modulation, particularly due to the soft organic motifs in porous frameworks. Both weak screening and lattice vibration effects would have direct implications for light absorption, charge separation, and charge carrier utilization - all crucial aspects of a photocatalytic reaction. In this thesis, interacting electrons are explored at different levels of theory to enable exploration and understanding of porous framework photocatalysts. By combining theory with experiments, we study the metal- organic framework MAE-1 for seawater splitting, which exemplifies the intrinsic complexity of porous framework photocatalysts. Motivated by this complexity, we developed a cost-efficient computational workflow to explore the chemical design space of these materials in order to identify promising candidates, design rules, and potential bottlenecks. This workflow is based on density functional theory (DFT), thus treating electron interaction approximately with an effective static potential. Going further, we evaluate interacting electrons beyond ground-state static DFT, encompassing dynamically screened electron-electron and electron-hole (excitons) interactions, as well as electron -phonon coupling. This approach allows us to establish the importance of electronic screening, excitons, and phonons in porous framework photocatalysts. Lastly, we bridge the gap between cost-efficient and accurate approaches by benchmarking, for MOFs, non-empirical screened range-separated hybrid functionals within DFT. Altogether, considering different approximations to the problem of interacting electrons enabled both a cost-effective wide search for promising candidates, and their in-depth analysis. Ultimately, a comprehensive understanding of porous frameworks as photocatalysts is closely tied to how we treat interacting electrons in these systems.