Date of Award

8-22-2025

Date Published

September 2025

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Advisor(s)

Karin Ruhlandt

Keywords

Crystallography;HKUST-1;Mechanism;MOF;SAXS

Subject Categories

Chemistry | Inorganic Chemistry | Physical Sciences and Mathematics

Abstract

Metal-organic frameworks (MOFs) are a class of inorganic porous coordination compounds of interest for technically relevant applications including gas storage & sequestration, catalysis, and drug delivery (Chapter 2). The last decade has seen significant development in this field of coordination chemistry, and an extensive array of MOFs have been reported despite the lack of a comprehensive scheme for how these materials form. The development of novel MOFs is not a trivial task, as the synthesis of target MOFs is notably unpredictable, and experiments require extensive trial-and-error reactions with systematic manipulation of the synthetic variables. Ideally, a toolbox method based on a mechanism of formation for these materials, such as those available to organic chemists, could simplify this process and present a more accessible pathway to novel MOFs. Efforts towards understanding the mechanism of formation of MOFs have provided insights into specific MOF systems (such as MOF-5) that follow the reticular chemistry model (Chapter 3): whereby a specific set of reaction conditions will produce a target MOF while only varying ligand substituents which vary the resulting MOF’s pore size. While this model has produced a significant number of complexes from a relatively minor number of base MOFs, this scheme does not explain how the synthetic variables influence MOF formation, nor does it experimentally identify reaction intermediates. This thesis seeks to contribute to the greater understanding of how synthetic variables influence MOF formation and to determine a mechanism of formation of MOFs. This work focuses on the copper-based MOF, HKUST-1 which was studied by time-resolved small-/wide-angle X-ray scattering techniques (S/WAXS) at the Elettra Synchrotron in Trieste, Italy (Chapter 4). SAXS analyses provide structural insights into the solid aggregation and nucleation growth processes while WAXS studies the growth of the larger crystalline MOF framework. Different series of reactions were performed to analyze the effect of a different synthetic variable (Chapter 5). The results have indicated that water has an inhibitive effect on MOF growth while solvent systems containing alcohol rapidly accelerate MOF growth. While water is desirable for greener MOF syntheses, our work also shows that when using high amounts of water (low reagent concentrations) MOF formation will not occur. Reagent addition is also an important factor related to the influence of water on MOF formation. Slow combination of the reagents is required to prevent significant amounts of water being introduced at any point in the reaction. When the reagents are rapidly combined, MOF growth is poor although it may still occur after a significant period. This thesis also identifies that solvent plays a structure-determining role in HKUST-1. This work has also identified the presence and formation of a reaction intermediate. Once the synthesis of HKUST-1 starts, the intermediate begins forming within seconds and grows for a brief period. This species then begins to convert to a di-copper paddlewheel crystalline complex identified as the secondary building unit (SBU) of HKUST-1. The SBU is considered in the reticular model to be the base unit of MOF which oligomerizes to form the greater MOF network. This work also attempted to elucidate a pattern regarding the effect of the anion of the different copper salts used to form HKUST-1.

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