Insoluble methylene-bridged glycoluril dimers as sequestrants for dyes

Contamination of water bodies by micropollutants including industrial dyes is a worldwide health and environmental concern. We report the design, synthesis, and characterization of a series of methylene-bridged glycoluril dimers <b>G2W1</b>-<b>G2W4</b> that are insoluble in water and that differ in the nature of their aromatic sidewalls (<b>G2W4</b>: benzene, <b>G2W3</b>: naphthalene, <b>G2W1</b> and <b>G2W2</b>: triphenylene). We tested <b>G2W1</b>-<b>G2W4</b> along with comparator <b>H2</b> as solid-state sequestrants for a panel of five dyes (methylene blue, methylene violet, acridine orange, rhodamine 6G, and methyl violet 6B). We find that catechol-walled <b>H2</b> (OH substituents) is a superior sequestrant compared to <b>G2W1</b>-<b>G2W4</b> (OMe substituents). X-ray crystal structures for <b>G2W1</b> and <b>G2W3</b> suggest that the OMe groups fill their own cavity and thereby decrease their abilities as sequestrants. <b>H2</b> achieved a removal efficiency of 94% for methylene blue whereas <b>G2W1</b> demonstrated a 64% removal efficiency for methylene violet; both sequestration processes were largely complete within 10 minutes.