The zeolites are noted for their ability towards ion-exchange and reversible dehydration. They have a framework structure that encloses interconnected cavities occupied by large metal cations (positively charged ions) and water molecules. Related Theory Zeolite are hydrated aluminosilicate minerals that contain alkali and alkaline-earth metals. They have a honeycomb-like structure, which makes them shape-selective catalysts. They have an extended 3D-network of silicates in which some silicon atoms are replaced by aluminium atoms giving Al-O-Si framework.