Cowlesite: the first natural 2D zeolite
Researchers of the Electron Crystallography research line coordinated by Mauro Gemmi have determined the crystal structure of Cowlesite a natural zeolite known since the 70’s but whose structure remained a mystery for years. The crystal structure determination is based on 3D electron diffraction a novel method of structure characterization developed at CNI. The researchers have prepared the sample of Cowlesite in a new way, by fast freezing a dispersion of crystals in water. In this way the crystals have been covered by vitrified ice, which prevented them to lose the interstitial water in the vacuum of the microscope, maintaining their crystal structure intact. Cowlesite structure is really unconventional. It is formed by 2D zeolitic blocks weakly bounded by Ca and water layers, which are responsible for its highly defective structure. Interestingly, if Cowlesite is not covered with vitrified ice, in the microscope vacuum it loses water and the 2D blocks attached forming a novel 3D zeolitic framework. Cowlesite is the first 2D natural zeolite ever discovered.