A unifying concept across many fields, ranging from chemistry to architecture, is the bottom-up construction of sophisticated structures from simple building blocks. Materials with long-range order allow for consistent, predictable performance throughout the resulting structure. My research focuses on building highly ordered porous materials from atomic level building blocks based on metal oxo clusters. I have synthesized and modulated the structure of atomically precise clusters as discrete entities and within multi-dimensional materials known as metal–organic frameworks (MOFs). In these studies, local techniques such as single crystal X-ray diffraction are utilized in tandem with powder X-ray diffraction, physisorption, and spectroscopic investigations of the bulk materials to fully describe the resulting structure and confidently derive property relationships. I first demonstrated a crystal design strategy to synthesize discrete cerium oxo clusters featuring permanent porosity. Aromatic capping agents facilitated noncovalent interactions between neighboring clusters to stabilize the overall assembly. The high surface exposure of these assemblies resulted in accessible oxygen vacancy defects that facilitated a proof-of-concept photocatalytic oxidation reaction. To further capitalize on high surface area Ce oxo assemblies, I next investigated the role of the interfacial unit connecting porous Ce70 toroids for CO oxidation. I demonstrated the catalytic performance, surface reducibility, and oxygen vacancy formation energetics can be varied based on the interfacial unit, highlighting the significant role of a defined atom at a specific location. I shift in subsequent chapters to developing synthetic strategies that isolate metal oxo clusters within MOFs and probe their structural evolution. I identified the kinetic and thermodynamic MOF architectures that result during the competitive nucleation of a Zr6 oxo cluster through two different organic linkers. In a following study, I utilized competitive nucleation as a strategy to stabilize a redox active CeIV oxo hexanuclear cluster within a MOF over a CeIII oxo mononuclear cluster. In my last chapter, I demonstrate a reversible phase transition between a hexanuclear Th oxo cluster MOF building unit to a mononuclear Th-based MOF. Within these studied conditions, we observed similar transitions with an isostructural Ce6-based MOF, yet the Zr and Hf analogues remained unchanged, highlighting differing metal oxo cluster stability.

Creator

• Wasson, Megan C

DOI

• https://doi.org/10.21985/n2-v1s6-tt83

Subject

• Inorganic chemistry

Language

• en

Alternate Identifier

• http://dissertations.umi.com/northwestern:16105
• etdadmin_upload_903742

Date created

• 2022-01-01

Resource type

• Dissertation

Rights statement

• In Copyright