Mg/Al ordering in layered double hydroxides revealed by multinuclear NMR spectroscopy
Mg/Al ordering in layered double hydroxides revealed by multinuclear NMR spectroscopy
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DOI：
10.1126/science.1157581
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发表时间：
2008-07-04
期刊：
影响因子：
56.9
通讯作者：
Grey, Clare P.
中科院分区：
文献类型：
--
作者：
Sideris, Paul J.;Nielsen, Ulla Gro;Grey, Clare P.
层状双氢氧化物（LDHs）的阴离子交换能力已被开发用于制造用于催化、药物递送和环境修复的材料。然而，在通式为Mg（1-x）（2+）Al（x）（3+）OH（2）（阴离子（x/n）（n-））·yH（2）O的类水滑石LDH的氢氧化物层中的特定阳离子排列仍然是难以捉摸的，它们的阐明可以增强这些材料的功能优化.我们应用快速（60千赫）魔角旋转（MAS）获得高分辨率氢-1核磁共振（（1H NMR）谱并表征镁和铝的分布。结合（1）H-（27）Al双共振和（25）Mg三量子MASNMR数据，这些数据表明镁：铝比为2：1时，阳离子是完全有序的，在较低铝含量时，阳离子的非随机分布持续存在，没有Al（3+）-Al（3+）紧密接触.应用快速MAS NMR方法研究质子在各种材料中的分布是很容易设想的。
The anion- exchange ability of layered double hydroxides ( LDHs) has been exploited to create materials for use in catalysis, drug delivery, and environmental remediation. The specific cation arrangements in the hydroxide layers of hydrotalcite- like LDHs, of general formula Mg(1-x)(2+)Al(x)(3+)OH(2)(Anion(x/n)(n-)).yH(2)O, have, however, remained elusive, and their elucidation could enhance the functional optimization of these materials. We applied rapid ( 60 kilohertz) magic angle spinning ( MAS) to obtain high- resolution hydrogen- 1 nuclear magnetic resonance ( (1)H NMR) spectra and characterize the magnesium and aluminum distribution. These data, in combination with (1)H-(27)Al double- resonance and (25)Mg triple- quantum MAS NMR data, show that the cations are fully ordered for magnesium: aluminum ratios of 2:1 and that at lower aluminum content, a nonrandom distribution of cations persists, with no Al(3+)-Al(3+) close contacts. The application of rapid MAS NMR methods to investigate proton distributions in a wide range of materials is readily envisaged.