Synthesis of Molecular Capsule for ClO4- Removal from Aqueous Solution.

Perchlorate (ClO4-) ion is known to interfere with the thyroid's uptake of iodide which is an essential component of growth hormones made in the thyroid gland. Therefore, consumption of excess ClO4- causes serious effects on human health, particularly on growth of newborns and children. The anion has been detected not only in river and ground water, but also in tap water and foods such as milk, lettuce, spinach, and tomatoes around the world. In 2005, the U.S. Environmental Protection Agency (EPA) has announced that an acceptable exposure level of this anion was 0.7 mg per kg of body weight per day, which was translated to 24.5 parts per billion (ppb) in drinking water.

Perchlorate ion has not only been produced as strong oxidant useful for gunpowder, rocket propulsion system, and road flares, but also been naturally formed in atmosphere. This anion is quite difficult to remove from aqueous solutions because of the high solubility in water. We have developed a new ClO4- removal method from water by encapsulation of the anion in the molecular capsule constructed by Cu2+ ions and bis-imidazole type ligands.