Abstract
Abstract An overview of the synthesis and structure characterization of manganese-modified microporous and mesoporous silicates for catalytic applications is presented with the emphasis on newly manganese-modified sponge-like mesoporous silicate. The porosity of the products was determined by X-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and nitrogen physisorption. The evidence for the presence of catalytically active Mn sites in the framework was obtained by Mn K-edge XANES and EXAFS analysis, which provided direct information on valence state and local environment of Mn in these products. The analysis revealed the presence of predominantly Mn 3+ cations located at a 3-fold coordination in the silicate framework indicating Lewis acid sites in microporous and mesoporous silicate structures (case studies of MnS-1, MnMCM-41, MnMCM-48). Newly prepared sponge-like mesoporous silicate structure MnKIL-2 with large pore openings of about 30 nm possess also predominantly Mn 3+ cations, that are attached to the framework, forming octahedral simmetry with the framework and water oxygen atoms.
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