Expanded Aromatic Monomers for Functional Porous Polymers
Karunathilake, Arosha Aruni Kumari
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Porous materials have attracted immense attention in the scientific community due to their excellent performance in a variety of applications such as gas adsorption, separation and catalysis. In the last few years utilizing expanded aromatic monomers for porous polymers has emerged as a method of designing and synthesizing functional porous polymers. As described in Chapter 1, expanded aromatic scaffolds such as hexaphenylbenzene (HEX), hexabenzocoronene (HBC) and corannulene have unique chemical structures and electronic properties that could be used to improve the performance of porous materials for applications in energy storage. Their unique symmetry and shape can be used to introduce novel topologies and conjugated π systems to porous polymers which provides improved gas binding ability. Chapter 2 describes a series of novel corannulene based porous organic polymers (BB-POPs) that retain the inherit redox activity of corannulene when incorporated into the porous system. These materials are the first reported POPs based on corannulene. Chapter 3 describes the synthesis and characterization of novel HEX and HBC based POPs (HEX-POP-93 and HBC-POP-98) for volatile organic compounds (VOCs) adsorption. Interestingly, while both POPs have moderate BET surface areas (687 and 548 m2 g-1 respectively), they both show an excellent selectivity for organic vapors over water, with a high benzene adsorption capacity of 99.9 wt.% for HEX-POP-93. Presented in Chapter 4 is the bottom-up synthesis of nanographene based porous organic polymers. Nanographenes (NGs) such as HBC are observed to readily adopt π-stacked arrangements. As such, stable π-stacked conformations between the HBC units are likely a major directing force for the POP structure. Since these interactions cause the π-surfaces within the polymer to be blocked, they limit the gas and VOCs adsorption capability. Thus, pre-synthesized HEX based POPs were post-synthetically cyclodehydrogenated to obtained NG based POPs with good surface areas and high CO2 binding ability (22 wt. %). The overall findings presented in this dissertation suggest that the expanded aromatic structures introduce novel properties to porous materials while the careful design will enhance the ultimate properties.