UC San Diego

The urgent global challenges of clean energy production and sustainable resource extraction have driven the search for advanced materials capable of addressing these needs. This dissertation focuses on two classes of nanoporous crystalline materials, covalent organic frameworks (COFs) and metal--organic frameworks (MOFs), to uncover the subtle composition--structure--property relationships that govern their electronic and photophysical properties in COFs, and the thermodynamics of ion uptake behavior in MOFs. By applying various appropriate levels of theory and methods for the systems of interest, including density functional theory (DFT), molecular dynamics, and enhanced sampling techniques, this work sheds lights on the electronic properties of COFs and the thermodynamics of ion transport in MOFs.

In the first part of the study, we investigate how interlayer stacking modulates charge transport in donor--acceptor 2D COFs. The results reveal that structural changes in stacking can result in dramatic tuning in electronic behavior, from delocalized, metallic-like transport to highly localized states with flat bands. These findings highlight the critical role of interlayer interactions in mitigating defect-induced trap states and enhancing charge mobility.

The second part expands this understanding by exploring how chemical composition, functionalization, and lattice symmetry influence stacking preferences and the resulting optoelectronic properties. We find that while van der Waals forces generally favor slipped stackings, functional group-specific electrostatics dominate the degree of slipping and symmetry breaking. Breaking lattice symmetry via backbone functionalization emerges as an effective strategy for tuning transport and photophysical properties, providing novel design principles for photocatalytic COFs.

Finally, we perform molecular dynamics simulations with enhanced sampling techniques and free energy calculations to investigate alkali metal ion uptake in MOF-808 from dilute aqueous solutions. We find that the small pore confinement leads to strong ion-specific thermodynamic and kinetic preferences, governed by a balance between dehydration penalties and confinement-driven stabilization. These insights lay the groundwork for designing MOFs with improved selectivity for critical metal recovery.

Together, this work provides a detailed electronic- and molecular-level framework for understanding and engineering the composition–structure–property relationships in COFs and MOFs, advancing their potential applications in electronics, photocatalysis, and sustainable ion capture from seawater.