Local environment of manganese incorporated in mesoporous MCM-41

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• 作者：Nataš ; a Novak Tuš ; ar ; Nataš ; a Zabukovec Logar ; Gilberto Vlaic ; Iztok Arč ; on ; Denis Arč ; on ; Nina Daneu and Venč ; eslav Kauč ; ič
• 关键词：MnMCM-41 ; XANES ; EXAFS ; ESR ; ESEEM
• 刊名：Microporous and Mesoporous Materials
• 出版年：2005
• 出版时间：2005
• 年：2005
• 卷：82
• 期：1-2
• 页码：129-136
• 全文大小：305 K

文摘

Manganese containing MCM-41 was synthesised by the direct hydrothermal method (DHT) in the presence of cetyltrimethylammonium chloride (CTACl) as a template. The local environment of manganese incorporated in mesoporous silicate MCM-41 was investigated by XAS (X-ray Absorption Spectroscopy). XANES (X-ray Absorption Near Edge Structure) studies showed the coexistence of Mn²⁺ and Mn³⁺ cations in both, as-synthesised and template-free MnMCM-41 samples. The major part of manganese cations in the as-synthesised MnMCM-41 was Mn²⁺, while in the template-free MnMCM-41 the amount of Mn³⁺ was increased. EXAFS (X-ray Absorption Fine Structure) analyses revealed that major part of manganese cations in the as-synthesised MnMCM-41 were extra-framework with the Mn–O distance of 2.19 . Manganese cations in the template-free MnMCM-41 were incorporated into the framework and coordinated to three oxygens in the first coordination shell, with two of them at a shorter distance of 1.92 and one at a longer distance of 2.21 . Pulsed ESR (Electron Spin Resonance) and ESEEM (Electron Spin-Echo Envelope Modulation) investigations were in agreement with the XANES and EXAFS results.