Octahedral molecular sieves OMS

Li, W., Yuan, J., Gomez-Mower, S., Sithambaram, S. and Suib, S.L. (2006) Synthesis of single crystal manganese oxide octahedral molecular sieve (OMS) nanostructures with tunable tunnels and shapes. Journal of Physical Chemistry B, 110, 3066-3070. 

A number of metal oxides can be described as porous materials. For instance, porous manganese oxides define octahedral molecular sieves (OMS) that have been introduced in recent years as possible materials for batteries, separations, and chemical... 

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 ... 

Figure 3.1 Structure and pore of manganese oxide octahedral molecular sieves (OMS) (a) todorokite (3x3) channel (b) romanechite (2x3) channel and (c) hollandite (2 x 2) channel...

R.N. DeGuzman, YP. Shen, E.J. Neth, S.L. Stub, C.L. OToung, S. Levine, J.M. Newsam, Synthesis and characterization of octahedral molecular sieves (OMS-2) having the hoUandite structure, Chem. Mater. 6 (1994) 815-821. 

Yamaguchi K, Kobayashi H, Wang Y, Oishi T, Ogasawara Y, Mizuno N (2013) Green oxidative synthesis of pimary amides from primary alcohols or aldehydes catalyzed by a cryptomelane-type manganese oxide-based octahedral molecular sieve, OMS-2. Catal Sci Technol 3(2) 318-327... 

Abbreviations AD, asymmetric dihydroxylation BPY, 2,2 -bipyridine DMTACN, 1,4-dimethyl-l,4,7-triazacyclonane EBHP, ethylbenzene hydroperoxide ee, enantiomeric excess HAP, hydroxyapatite LDH, layered double hydroxide or hydrotalcite-type structure mCPBA, meta-chloroperbenzoic acid MTO, methyltrioxorhenium NMO, A-methylmorpholine-A-oxide OMS, octahedral molecular sieve Pc, phthalocyanine phen, 1,10-phenantroline PILC, pillared clay PBI, polybenzimidazole PI, polyimide Por, porphyrin PPNO, 4-phenylpyridine-A-oxide PS, polystyrene PVP, polyvinylpyridine SLPC, supported liquid-phase catalysis f-BuOOH, tertiary butylhydroperoxide TEMPO, 2,2,6,6-tetramethyl-l-piperdinyloxy TEOS, tetraethoxysilane TS-1, titanium silicalite 1 XPS, X-ray photoelectron spectroscopy. 

This review concerns the synthesis, characterization, and catalytic activity of microporous ferrierite zeolites and octahedral molecular sieves (QMS) and octahedral layer (OL) complexes of mixed valent manganese oxides. The ferrierite zeolite materials along with borosilicate materials have been studied as catalysts for the isomerization of n-butenes to isobutylene, which is an important intermediate in the production of methyltertiarybutylether (MTBE). The CMS materials have tunnels on the order of 4.6 to 6.9 A. These materials have been used in the total oxidation of CO to C02, decomposition of H2O2. dehydrogenation of CeHi4, C0H14 oxidation, 1-C4H3 isomerization, and CH4 oxidation. The manuscript will be divided into two major areas that describes zeolites and OMS/OL materials. Each of these two sections will include a discussion of synthesis, characterization, and catalytic activity. 

An efficient oxidation catalyst OMS-1 (octahedral molecular sieve) has been prepared by microwave irradiation of a family of layered and tunnel-structured manganese oxide materials. These materials are known to interact strongly with micro-wave radiation, and thus pronounced effects on the microstructure were expected. Their catalytic activity was tested in the oxidative dehydrogenation of ethylbenzene to styrene [27]. 

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. 

OMS octahedral molecular sieve manganese oxide catalysts... 

In the same year, Shi and co-workers reported the iV-alkylation of anilines, aliphatic amines and indoles with alcohols catalyzed by Pd/Fe203 under base- and ligand-free conditions with a low catalyst loading (0.43 mol%) (Eq. 40) [144]. In 2013, Pera-Titus and co-workers reported the //-alkylation of anilines catalyzed by another heterogeneous Pd catalyst Pd/K-OMS-2 (Pd-substituted octahedral molecular sieve) [145]. 

The abihty of the aluminiun to attain six coordination when associated with phosphate ligands results in the aluminophosphate molecular sieves exhibiting some unusual thermal properties. As discussed previously, D Yvoire s (n = 1 -6) materials were hydrated species with some of the aliunimun in octahedral coordination, four points attached to the phosphate in the framework, and the two remaining coordination sites occupied by molecules of water. The labihty of these water molecules is dependent on the structure. AIPO4S prepared fi-om organic-containing systems can also exhibit expanded coordination around the aluminum. 

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