Synthesis, Characterization, and Multistep Postsynthetic Modification of Covalent Organic Frameworks

Chapter 1: Introduction to the current state of the field of Covalent Organic Frameworks (COFs), covering methods of synthetic control over the structure, chemistry, and reactivity of these framework materials. Emphasis is given on the nature of the field as an extension of organic synthesis into two- and three-dimensional solids./nChapter 2: In this chapter, I describe the first postsynthetic modification of a COF’s linkage, the functional groups generated upon reticulation of its building units into an extended network. Specifically, a two-dimensional imine-linked COF of kgm topology was converted to an amide-linked material of the same structure and connectivity by Pinnick-type oxidation of its imine linkages. The resulting amide-linked material possesses enhanced stability in aqueous acid and base relative to its imine-progenitor. This postsynthetic approach allows access to novel COF linkages without the need to determine conditions for which an ordered network of that linkage can be formed directly, decoupling the relationship between crystallinity and linkage reversibility previously inherent in COF chemistry./nChapter 3: In this chapter, I describe the synthesis of cyclic carbamate and thiocarbamate-linked COFs, made from the multistep postsynthetic modification of an isostructural imine-linked framework. Unlike linkages previously accessed through postsynthetic modification, these are the first linkages accessible only through multiple synthetic steps in the solid. Furthermore, each step along the synthetic route was analyzed by 15N multiCP-MAS NMR spectroscopy, for the first time allowing quantitative analysis of postsynthetic modifications in COFs. This work sets a new standard for the execution and evaluation of multistep chemical transformations of solids, and in doing so lays the groundwork for further exploration of solid-state organic synthesis./nChapter 4: A new three-dimensional COF, COF-432 was synthesized, whose structure violates commonly accepted heuristics for the prediction of COF structures from their building units. COF-432 possesses a topology previously reported in COFs or metal-organic frameworks (MOFs). Additionally, in testament to the value of expanding the structural diversity of COFs, COF-432 has a type-IV water adsorption isotherm with a sharp uptake at 35% relative humidity, suggesting it may be applicable in water capture technologies./nChapter 5: The interdisciplinary nature of COF chemistry, and reticular chemistry in general, makes these fields effective teaching tools in training undergraduate students for research in graduate school and beyond. In this chapter, a teaching program is described in which thirty students from around the world participated in a lab and lecture course covering concepts, synthetic techniques, and characterization techniques used in reticular chemistry. Students also participated in a poster session and simulated paper submission exercise, giving them experience not just in carrying out research, but also communicating the results of that work to the greater scientific community.

Advisor: Yaghi, Omar M