In 1756, a mineralogist named A.F. Cronstedt discovered the first of a group of minerals that,
when heated, appeared to boil. Cronstedt soon realized that the boiling effect was due to very fast water
loss. The observation that the mineral had been able to hold so much water within it suggested that it was
very porous, and as Cronstedt and other scientists further explored the molecular structures of such
minerals they were determined to have very open molecular frameworks. Cronstedt named this group of
micro-porous minerals zeolites (from the Greek “zein” and “lithos”, meaning “stones that boil”) [1].
More specifically, a zeolite is a hydrated alumina-silicate mineral that has a very micro-porous structure.
The corners of the structures are composed of [AlO 4 ]- and [SiO 4 ]- tetrahedra. In order for a mineral to be
considered microporous, the channels or pore openings must be less than 20 Å. Most zeolites have pore
openings much smaller than this. In general, zeolites (also called “molecular sieves”) are defined to be
three dimensional frameworks of tetrahedrally coordinated atoms (T-atoms) with cavities or channels for
which the smallest opening is larger than six T-atoms [1].