The Significance of Methodology in the Synthesis of Framework Materials

Robertson, Jennifer H. ORCID: 0000-0002-6650-4645 (2023). The Significance of Methodology in the Synthesis of Framework Materials. University of Birmingham. Ph.D.

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Abstract

In order to harness the diverse potential applications of framework materials it is necessary to understand how to efficiently and precisely control their structures and properties, and to develop robust, reproducible methods for their preparation. This thesis examines the synthesis and analysis of metal-organic frameworks and hydrogen bonded materials, investigating how small variations in synthetic conditions and the use of different synthetic techniques influence the resulting structures. This work complements studies into the challenges of reproducibility in framework material synthesis, emphasising the importance of methodological consistency and highlighting the capability to leverage system sensitivity to control product outcomes.
Given the group’s interest in studying reactivity within framework materials, Chapters 2 and 3 employ imidazolium-containing linkers, which offer exciting possibilities to study a wide range of chemistry within the framework environment if control over the identity of the resulting structures can be achieved.
Chapter 2 reports five new single crystal copper metal-organic framework (MOF) structures synthesised using 1,3-bis(4- carboxyphenyl)imidazolium compounds. Minor changes to the organic linker and adaptations to the crystallisation conditions were found to directly impact the structures formed. The new frameworks are described in detail and results analysed in context with existing structures in the literature.
Chapter 3 focuses on the synthesis of hydrogen-bonded organic frameworks, with five new structures produced using imidazolium-centred ligands. Strong carboxylate-amidinium hydrogen bonding interactions are leveraged in this work to produce highly crystalline frameworks. Influence over the resulting products was realised via methyl substitution at the imidazolium and controlled deprotonation of carboxylic acid
groups. A potentially porous framework was synthesised through these adaptations and some preliminary explorations into the potential for metal complex incorporation were performed.
In Chapters 4 and 5 the capability of mechanochemistry to provide alternative routes for synthesis is explored in the context of hydrogen-bonded co-crystals and frameworks. Chapter 4 reports the development of a reliable methodology for the synthesis of a family of cyanuric acid and trithiocyanuric acid containing co-crystals using ball milling. Comparisons are drawn between the mechanochemical products and related co-crystals synthesised from solution.
Finally, Chapter 5 reports the use of mechanochemistry to synthesise a bulk-phase perylene diimide and melamine hydrogen-bonded organic framework. This result is particularly notable as this framework had until now been accessible only by surface deposition, as a thin layer. X-ray diffraction analysis in conjunction with computational modelling of predicted structures allowed the identification of the mechanochemical product as a layered honeycomb HOF. This work highlights the relevance of unconventional techniques for material discovery.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):