New Insights into the Molecular Structures, Compositions, and Cation Distributions in Synthetic and Natural Montmorillonite Clays

作者：Cadars Sylvian^*; Guegan Regis; Garaga Mounesha N; Bourrat Xavier; Le Forestier Lydie; Fayon Franck; Tan Vu Huynh; Allier Teddy; Nour Zalfa; Massiot Dominique

来源：Chemistry of Materials, 2012, 24(22): 4376-4389.

DOI：10.1021/cm302549k

• NMR
• ab initio calculations
• first-principles calculations
• smectite
• layered alumino-silicates
• 2:1 clays

We present a detailed investigation of the molecular structure of montmorillonite, an aluminosilicate clay with important applications in materials sciences, such as for catalysis, drug delivery, or as a waste barrier. Solid-state Si-29, Al-27, Mg-25, and H-1 nuclear magnetic resonance (NMR) measurements combined with density functional theory (DFT) calculations provide a comprehensive picture of the local structure and composition of a synthetic clay and its naturally occurring analogue. A revised composition is proposed based on NMR results that allow the identification and quantification of the signatures of otherwise undetectable noncrystalline impurities, thus largely complementing the traditional elemental analyses. Solid-state H-1 NMR at fast magic-angle spinning (MAS) and high magnetic field provide quantitative information on intra- and interlayer local environments that are crucial for the determination of the amount of Mg/Al substitution within the octahedral layer. In combination with DFT calculations of energies, it suggests that pairs of adjacent Mg atoms are unfavorable, leading to a nonrandom cationic distribution within the layers.

• 出版日期2012-11-27