Molecular sieve

Molecular sieves are materials that can separate molecules based on size. This capability is based on the presence in the material of tiny pores of exact and uniform size, with a diameter between 3 and 10 Å depending on the material. Molecular sieves have a very high surface area within the pores (600-700 m2/g). Molecules larger than the pores cannot enter the material. Molecules small enough to penetrate through the pores can enter the material; generally polar molecules are adsorbed on the internal surface of the pores and remain trapped, while apolar molecules are not retained. The most commonly used materials as molecular sieves are aluminosilicates and in particular zeolites, both natural and synthetic. Other materials such as aluminophosphates or polymeric cyanocomplexes have a porous structure in principle suitable as molecular sieves, but so far have not been used in technical applications.

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