| 초록 |
The use of conventional synthetic methods and ethoxide or chloride metal sources led to the successful substitution of Ga, Ti and B into zeolite frameworks. However, these methods are not generally applicable to the syntheses of most transition metal substituted frameworks because most of transition metals easily precipitate at high pH as insoluable hydroxides. In order to avoid a hydroxide precipitate, synthetic routes at lower pH are required. Recently, Pal-Borbely et al. have synthesized the MFI, MEL and FER type zeolites by recrystallization of Magadiite. Proton or transition metals can easily exchange for sodium ions that reside between the layers of layered silicate. The proton exchanged silicates are sufficiently acidic to allow proton transfer to an amine group which is contained transition metal. So, these "layered silicic acids" are expected to be good precusors for the synthesis of metallosilicates. Recrystallization of such precusor may not require transport process mediated in the conventional synthesis by the liquid phase. We report here the synthesis and characterization of Co and Mn isomorphously substituted silicalite-1 prepared from Co2+ or Mn2+ ion exchanged magadiite. By stabilizing Co2+ and Mn2+ species between the layers of silicates, it is possible to prepare a framework material which the cobalt and manganese ions are present in the tetrahedral framework sites.
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