Mesoporous manganese oxides

Manganese oxide mesoporous solids (MOMS) of both hexagonal and cubic phases have been recently prepared via incorporation of surfactant micelles and partial oxidation of... 

Tian[240] prepared hexagonal and cubic phases of manganese oxide mesoporous structures by means of the oxidation of Mn(OH)2. The hexagonal materials form thick walls (1.7 nm) and exhibit exceptional thermal stability (1000 °C). The walls of the mesopores are composed of microcrystallites of dense phases of Mn203 and Mn304, with Mn06 octahedra as the primary building blocks. 

Z.R. Tian, W. Tong, J.Y. Wang, N.G. Duan, V.V. Krishnan, and S.L. Suib, Manganese Oxide Mesoporous Structures Mixed-valent Semiconducting Catalysts. Science, 1997, 276, 926-930. 

In contrast to Cr203 materials, manganese oxide mesopores are constructed by assembly of nanocrystallites, and crystallite sizes are smaller than or equal to the wall thickness. 

Tian, Z.-R. Tong, W. Wang, J.-Y. Duan. N.-G. Krishnan. V.V. Suib. S.L. Manganese oxide mesoporous structures Mixed-valent semiconducting catalysts. Science 1997, 276. 926. 

Tian ZR, Tong W, Wang JY, Duan NG, Krishnan W, Suib SL (1997) Manganese oxide mesoporous stmctures Mixed-valent semiconducting catalysts. Science 276 926-930 Tossell JA (1977) SCF-Xa scattered wave MO studies of the electronic stmcture of ferrous iron in octahedral coordination with sulfur. J Chem Phys 66 5712-19 Tossell JA, Vaughan DJ (1987) Electronic stmcture and the chemical reactivity of the surface of galena. Can Min 25 381-392... 

E. Applications of Manganese Oxide Mesoporous Solids and Manganese Based Porous Mixed Oxides... 

Manganese oxide mesoporous structures mixed-valent semiconducting catalysts. Science, 276, 926-930. 

Manganese oxide mesoporous materials were prepared by using template assisted method followed by an acidic treatment. The cerium addition to manganese oxide mesoporous stmcture was also studied. All the solids were characterized by XRD and specific surface area and pore size distributions were calculated from nitrogen sorption studies. XRD results suggested the formation of the Mn0x-Ce02 solid solution widi the fluorite-type stmcture. The BET surface area values and the pore size distributions allowed to conclude the important role of the surfactant by the creation of narrow mesopores in the material. 

Keywords Mesopores Hexagonal nanoplates Manganese oxides TEM. 

Isoelectronic mesoporous Ti02 has been prepared by the same method but it is also not stable to template removal (224, 227). Hexagonal and cubic manganese oxide mesostructures (MOMS) have been prepared (228). Layered Mn(OH)2 is combined with CTAB and stirred at 75°C for 12 h. Depending on the CTAB concentration, either hexagonal MOMS-1 or cubic MOMS-2 is formed. The MOMS phases are apparently stable to calcination and exhibit semiconducting properties. 

Seredych M, Bandosz TJ. Manganese oxide and graphite oxide/Mn02 composites as reactive adsorbents of ammonia at ambient conditions, Microporous and Mesoporous Materials 2012, 150, 55-63. 

Other kinds of mesoporous manganese based materials have been also reported by transformation of layered bimessite (18). Finally amorphous microporous manganese oxidic materials prepared by the reaction between KMn04 and oxalic acid and incorporation of hetero-cations like Cu, Cr and Zn in them have been recently prepared and tested as catalysts (19, 20). 

Rhodes, C,P, J,W, Long, M,S, Doescher, B,M, Dening, and D,R, Rolison, Charge insertion into hybrid nanoarchitectures mesoporous manganese oxide coated with ultrathin polylphenylene oxide). Journal of Non-Crystalline Solids, 2004, 350 pp, 73-79 Kuznetsov, A,M, and J, Ulstrup, ElectrochemicaActa, 2000, 45 p, 2339 Fawcett, W,R, J, Lipkowski and P,N, Ross, Editors, Electrocatalysis 1998, Wiley New York, p, 323... 

The first mesoporous crystalline manganese oxide was prepared by oxidation of a Mn(OH) nanosheet in the presence of an ionic organic surfactant (CTAB). ... 

Jiao F, Frei H (2010) Nanostractured manganese oxide clusters supported on mesoporous silica as efficient oxygen-evolving catalysts. Chem Commun 46 2920-2922... 

Suib and coworkers demonstrated that a mesoporous mixed-valent manganese oxide can be successfully synthesized by the direct precipitation of manganese hydroxide precursors in basic conditions.The ordered mesoporous structure with crystalline pore walls was retained after calcination as confirmed by powder x-ray diffraction (XRD) and transmission electron microscope (TEM). Such mixed-valent mesoporous oxides are semiconducting and possess catalytic activity in the oxidation of alkanes. The mixed oxidation states of manganese (III/IV) in these materials were introduced by the direct oxidation of the metal precursor [Mn(II)j. Both hexagonal and cubic phases of such mesoporous materials can be synthesized. 

Li, S. H., L. Qi, L. H. Lu, and H. Y. Wang. 2012. Facile preparation and performance of mesoporous manganese oxide for supercapacitors utilizing neutral aqueous electrolytes. RSCAdvances 2 3298-3308. 

Supported manganese-oxide catalysts were prepared in three alumina-based supports mesoporous synthetic and commercial 7-AI2O3 (surface areas of 287 and 184 m g , respectively) and nonporous a-Al203 (surface area = 35 m The hybrid materials were tested in the catalytic ozo-... 

Ordered mesoporous manganese oxide (MnOj consisting of a mixture of tetragonal manganese dioxide and cubic MnaOg phases (surface area of... 

Luo et al. first reported the transformation of a typical layered manganese oxide to a mesoporous structure [55]. The precursor for the transformation of layered birnessite to a mesoporous manganese oxide is synthesized K-birnessite, which is ion exchanged in HNO3 to obtain H-birnessite. Details of this preparation... 

LayCTed manganese oxide mataials have porous structures ranging from ultramicropore to mesopore dimensions and cation exchange and molecular adsorptive properties. Tha-efore, they can be used as ion sieves, molecular sieves, and catalysts, similar to zeolites [61]. Spinel-type ion sieves have shown good adsorptive properties for lithium from seawate and other dilute solutions. Repeated adsorp-... 

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