Manganese-based mesoporous materials

C. Pillared Layered Manganese-Based Materials and Manganese-Based Mesoporous Materials... 

Manganese-Based Mesoporous Materials and Manganese-Based Porous Mixed Oxides... 

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). 

A new family of hybrid organic-inorganic catalysts with dispersed active sites inside ordered mesoporous materials has been prepared by anchorage of transition-metal ligands of Schiff base-type and chiral amino alcohols like (li ,2S)-ephedrine on micelle-templated silicas [180]. Metalation of the grafted ligands with manganese was followed by UV-VIS spectroscopy. 

The existence of these stable, open-frameworks in the specific case of manganese is presumably related to the high ligand field stabilization energy associated with the t2g electronic configuration of Mn +. This should render the materials kinetically stable with respect to their collapse into more condensed phases. It is also, no doubt, the reason why it has been possible to make stable mesoporous phases based upon Mn02, and indeed to remove the surfactant templates in order to access their microporosity [110]. 

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-... 

Mesoporous oxides from elements other than sihca have been reported as early as 1994. Cieslaetal. [169] found that metals such as Sb, Fe, Zn, Pb,W, and Mo also form mesoporous oxides. However, many of the mesophases obtained were lamellar and were not porous after template removal (calcination). Antonelli and Ying reported the transformation of titanium, niobium, and tantalum alkoxides into stable mesophases [170]. Subsequently, mesoporous oxides based on zirconium, hafnium, and manganese have been synthesized (for a recent review on these materials see [171]). Bagshaw and Pinnavaia [172] prepared mesoporous alumina with worm-like pores and a specific surface area of more than 400 m g . Mesoporous alumina with surface areas above 700 m g have been reported by Vaudry et al. [173]. 

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