Design, synthesis, and applications of porous crystals from self-assembled bis-urea macrocycles

There is a great interest in developing porous materials due to their applications in chemistry, biology and materials science. These applications include gas storage, separations, catalysis, ion exchange, small molecule sensing and use as confined nano-reactors. Supramolecular chemistry provides a variety of strategies to readily construct porous materials from small building blocks. One such strategy is to design macrocycles that can self-assemble into hollow cylindrical frameworks. This thesis investigates the self-assembly of bis-urea macrocycles which form tubular structures through hydrogen bonding and pi-pi stacking interactions. The porous crystals formed from a phenylether bis-urea macrocycle had a channel of ∼6A in diameter and displayed type I isotherms in CO2 gas adsorption, which confirmed their microporous nature. This phenylether host tubular structures selectively bound guest molecules and displayed shape selectivity for p-xylene among a mixture of xylenes. We also demonstrated the use of this host as a confined reaction environment for highly selective [2+2] photocycloaddition reaction of &agr;,beta-unsaturated ketones. A second bis-urea macrocycle with a benzophenone framework also assembled similar to give a porous host. This host also reversibliy bound guest molecules and facilitated a cis-trans isomerization of trans-beta-methylstyrene. A larger phenylethynylene bis-urea macrocycle was also synthesized.