Microporous Metal Oxides-Octahedral Molecular Sieves

Inorganic molecular sieves in which all of the framework cations are coordinated octahedrally comprise a small but significant family of microporous solids. The octahedral molecular sieves, or OMS materials, related to manganese oxide minerals of the hollandite family, are the most important of these. Examples have been prepared by Suib and co-workers through the hydrothermal treatment of layered manganese oxides. Careful choice of additional metal ion content of such preparations controls the inorganic phase that forms. The 

Further to the synthesis of the OMS materials, researchers at Sandia National Laboratories reported the synthesis of a family of microporous niobates, general formula Na2Nb2 xM 06 x(0H)x.H20 (M = Ti, Zr x = 0.04-0.40), prepared from hydrothermal treatment of intimately mixed metal alkoxide precursors. The structure is made up of layers of edge-sharing octahedra interleaved with double ehains of edge-sharing niobate octahedra, in which additional, hydrated sodium eations reside. The niobate chains exhibit solid substitution. These SOMS (Sandia octahedral molecular sieves) demonstrate appreciable ion exchange eapacity and are selective for divalent cations. 

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The first ordered microporous transition metal oxides were microporous manganese oxides, known as octahedral molecular sieves (OMS). The manganese oxide OMS are classified into three families the pyrolusite-ramsdellite family with a (1 x n) channel structure the hollandite-romanechite family with a (2 x n) channel structure ... 

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