Nature and Location of Copper Nanospecies in Mesoporous Molecular Sieves
Nature and Location of Copper Nanospecies in Mesoporous Molecular Sieves
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DOI：
10.1021/jp9094529
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发表时间：
2010-01-28
影响因子：
3.7
通讯作者：
Eimer, Griselda A.
中科院分区：
文献类型：
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作者：
Chanquia, Corina M.;Sapag, Karim;Eimer, Griselda A.
通过在初始合成凝胶中不同的金属直接掺入方法，成功制备了 MCM-41 型铜介孔分子筛。材料表征采用了各种技术，包括 XRD、AAS、N-2 吸附/解吸、UV-vis-DR、TPR 和 XPS。除了高比表面积和孔体积外，所有材料都表现出良好的结构规律性，即使铜含量接近 10 wt%。对铜氧化态的性质以及硅质纳米结构上铜物质的分布进行了广泛而详细的研究。研究发现，铜以多种形式存在于介孔二氧化硅上：孤立的单核 Cu δ+ 阳离子，可能与晶格氧配位；线性寡核 [Cu δ+中心点 中心点 中心点 O δ-中心点 中心点 中心点 Cu δ+](n) 簇可能插入介孔通道中；和大体积的 CuO 氧化物在结构中分离。最终固体中铜物质的分布取决于所用的制备方法以及初始凝胶中的铜含量。此外，我们推断铜氧化态+1和+2（+δ）在这些材料的主要物质中共存：孤立的和寡核铜物质。
Copper-mesoporous molecular sieves type MCM-41 have been successfully prepared by different direct incorporation methods of the metal in the initial synthesis gel. Various techniques including XRD, AAS, adsorption/desorption of N-2, UV-vis-DR, TPR, and XPS were employed for the materials characterization. All of the materials exhibited a good structural regularity, even for loadings of copper of similar to 10 wt %, besides high specific surface areas and pore volumes. An extended and detailed study about the nature of copper oxidation state as well as of the copper species distribution on the siliceous nanostructure has been made. It was found that copper is present on the mesoporous silica in the form of various species: isolated mononuclear Cu delta+ cations possibly in coordination with the lattice oxygen; linear oligonuclear [Cu delta+center dot center dot center dot O delta-center dot center dot center dot Cu delta+](n) clusters probably inserted into mesoporous channels; and bulky CuO oxide segregated of the structure. The distribution of copper species in the final solid depends on the preparation method used as well as of the copper content in the initial gel. Moreover, we infer the coexistence of the both copper oxidation states +1 and +2 (+delta) in the major species of these materials: isolated and oligonuclear copper species.