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Access Type
WSU Access
Date of Award
January 2025
Degree Type
Dissertation
Degree Name
Ph.D.
Department
Chemistry
First Advisor
James R. Bour
Abstract
Porous aromatic frameworks (PAFs) are a class of rigid, exceptionally stable polymers that exhibit some of the highest surface areas observed for a fully organic material. The exhibit a high-degree of reaction dependent surface area measurements, with the same reaction, the Yamamoto-type Ullmann coupling, being used to synthesize all the highest surface area examples. We investigated the reaction features responsible for differences observed in polymers with the same formal structure synthesized through different reaction routes. Our hypothesis being that differences were due to defects, or departures from the anticipated structure, in the lower surface area examples. These defects would decrease the overall rigidity of the PAF, allowing it to collapse to a denser, less porous phase. Chapter 2 reports the first measurement of native defectivity in PAFs and explores how increasingly defective structures in PAFs lead to lower surface area materials. Notably, we now understand the relationship between coupling efficiency and surface area, imparting us with an important design principle for the creation of new reaction routes towards high surface area PAFs. With the importance of coupling efficiency now known, we then explored opportunities to modify the Yamamoto-type Ullmann coupling reaction to be more economical and accessible, due to its utilization of an expensive and sensitive nickel mediator. Chapter 3 describes the Ni(COD)2-free synthesis of high-surface area PAFs via the in-situ reduction of a more cost-effective Ni(II) source. Anhydrous nickel dibromide is reduced with activated zinc in the presence of COD and bipy to reach Ni(bipy)(COD), the reactive intermediate in the conventional Ni(COD)2-mediated synthesis. The PAF produced through this route was comparable to PAF produced through the conventional synthesis. This route was generalizable to seven different monomers yielding polymers that were comparable in all but one case to those synthesized through Ni(COD)2-mediated approaches. Additionally, the use of less sensitive reagents allowed for gram-plus scale syntheses on the Schlenk line, further increasing accessibility by eliminating the need for an inert atmosphere glovebox. Mesoporous PAFs have been a system of interest for many years. The inability to synthesize them through an isoreticular-expansion style approach has historically been attributed to interpenetration growing polymer network with other polymer strands, newly enabled by the larger pores. Chapter 4 presents an alternative hypothesis, that longer-strut POPs are more defective. The effects of defects in these systems were larger unknown until recently, it is conceivable that there may be more defects present in longer strut systems. Defectivity in long-strut materials is initially investigated using an extended PPN-4 system, PPN-4-XL. The lack of solubility of digested fragments led to the exploration of alternative alkyl substituted systems. Additionally, three other extended strut systems were synthesized and their properties are compared to the shorter-strut conventional examples. The inability to differentiate between interpenetrated and collapsed defective structures illustrates the need for the development of new imaging techniques that can resolve spatial differences in amorphous systems.
Recommended Citation
Porath, Anthony, "Engineering Porosity In Porous Organic Polymers" (2025). Wayne State University Dissertations. 4266.
https://digitalcommons.wayne.edu/oa_dissertations/4266