Date of Thesis

Spring 2019

Thesis Type

Honors Thesis (Bucknell Access Only)

Degree Type

Bachelor of Science

Major

Cell Biology/Biochemistry

First Advisor

Brian J. Smith

Keywords

Polymer, Covalent, Organic, Framework, COF, Synthesis

Abstract

Covalent organic frameworks (COFs) are porous, crystalline polymers that are designed based on rigid monomer geometry. They can either be two-dimensional or three-dimensional networks depending on monomer shape and number of possible connections. Although 2D systems have received more focus in the literature, 3D systems have many benefits. Applications for COFs rely on their high surface areas and predictable pore sizes, and therefore it is important to understand the mechanism of COF growth in order to optimize the final product for target uses including water treatment, electronic devices, and chemical storage.

Our model system of 3D imine-linked framework COF-300 crystallizes in two possible forms, the expected porous system and a collapsed water-bound structure. Through use of both heat and vacuum, it is extremely difficult to evacuate the bound water from the collapsed form. Therefore, it is highly important to preferentially synthesize the porous form of COF-300 during the initial preparation. While both crystal forms have been reported, it is not currently known what factors drive the selectivity towards the porous form.

Here we establish that 3D imine COFs grow through an amorphous transition state, similar to 2D imine-linked systems. The final structure is highly sensitive to the initial solvent conditions, as water is both the cause of the collapsed form and a requirement for imine bond exchange leading to a crystalline structure. We report a mechanistic study into 3D imine framework growth, where we identify ideal synthesis conditions to selectively form the high surface area material, and demonstrate its generality to other 3D imine COFs.

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