(174ax) Investigating the 3-D Assembly of Chemically Specific Building Blocks for Covalent Organic Frameworks

Authors: 
Maula, T., Lehigh University
Rangarajan, S., Lehigh University
Mittal, J., Lehigh University
Covalent organic frameworks (COFs) are a network of porous polymers assembled from organic molecule building blocks with lightweight elements. COFs have high porosity and can assemble into a diverse array of 2-D or 3-D porous networks, giving them tremendous potential for industrial applications like molecular sieving, energy storage, catalysis, and optoelectronics. However, widespread industrial adoption of COFs have been hampered by the current lack of ability to assemble large domains of crystalline COFs. Our previous work on this topic suggested that endowing building blocks with orthogonally-reacting functional sites can hinder these building blocks from forming polymorphous or disordered structures, thus enhancing their ability to assemble into large crystalline domains. This work, however, used a patchy molecule model which coarse-grained out a lot of the chemistry and additionally confined the building blocks to a 2-D surface. We now expand upon this work by investigating the 3-D assembly of COFs using an implementation based on Nguyen and Grünwald’s more detailed united atom model for COF-5. We focus on assessing whether the use of orthogonally-reacting functional sites is as effective in preventing polymorphism in 3-D as in 2-D. In 3-D, the molecules have more degrees of freedom and stacking interactions can play a large role in the ability of COFs to assemble into defect-free sheets. We additionally examine the effect of competing reactions on the dynamics of assembly.