A<unk>  is a material containing tiny pores of a precise and uniform size that is used as an adsorbent for gases and liquids.
Molecules small enough to pass through the pores are adsorbed while larger molecules are not.  It is different from a common filter in that it operates on a<unk>  level.  For instance, a water molecule may be small enough to pass through while larger molecules are not.  Because of this, they often function as a desiccant. A<unk>  can adsorb water up to 22% of its own weight.
Often they consist of aluminosilicate minerals, clays, porous glasses, microporous charcoals, zeolites, active carbons, or synthetic compounds that have open structures through which small molecules, such as nitrogen and water can diffuse.<unk> s are often utilized in the petroleum industry, especially for the purification of gas streams and in the chemistry laboratory for separating compounds and drying reaction starting materials. The mercury content of natural gas is extremely harmful to the aluminum piping and other parts of the liquefaction apparatus - silica gel is used in this case.
Methods for regeneration of<unk> s include pressure change (as in oxygen concentrators), heating and purging with a carrier gas (as when used in ethanol dehydration), or heating under high vacuum.
Molecular sieve
Cantilever mechanics 
Fluency
Molecular mass
Bifunctional catalyst
Filter 
Electrostatics
Electrode