Experimental observations of water-framework interactions in a hydrated microporous aluminum phosphate.
Experimental observations of water-framework interactions in a hydrated microporous aluminum phosphate.
复制标题
水合微孔磷酸铝中水-骨架相互作用的实验观察。
DOI：
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发表时间：
2005
影响因子：
3.3
通讯作者：
A. Kolesnikov
中科院分区：
文献类型：
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作者：
Huaixin Yang;R. Walton;Silke Biedasek;S. Antonijevic;S. Wimperis;A. Ramirez‐Cuesta;Jichen Li;A. Kolesnikov
水合微孔磷酸铝AlPO-14的差示扫描量热法显示在室温和120 ℃之间有两种不同的水分损失，表明固体中存在两种类型的水。多量子魔角自旋（MQMAS）（27）Al NMR显示，虽然在脱水的AlPO-14中发现所有铝都在四面体位点中，但在水合时，显著比例的铝将其配位数增加到6。这解释了紧密结合水的存在。第一个详细的非相干非弹性中子散射（IINS）的研究，这样一个系统给出了一个光谱与不同的和尖锐的束缚水，显着不同，比在冰Ih。使用这些数据，并通过考虑脱水的AlPO-14的晶体结构，我们提出了一个模型的水合材料，其中紧密结合的水桥对刘易斯酸性框架铝在结构的致密区域，而松散结合的水驻留在固体的孔隙。使用高入射中子能量的进一步IINS测量提供的数据与我们的模型一致。我们可以检测到水合AlPO-14中结合水的两种O-H伸缩模式，与材料中存在的两种类型的水的模型一致，松散结合的水通过分子间氢键与相邻的水分子连接。
Differential scanning calorimetry of the hydrated, microporous aluminum phosphate AlPO-14 shows two distinct water losses between room temperature and 120 degrees C, indicating the presence of two types of water in the solid. Multiple-quantum magic angle spinning (MQMAS) (27)Al NMR shows that, while in dehydrated AlPO-14 all aluminum is found in tetrahedral sites, on hydration a significant proportion of the aluminum increases its coordination number to 6. This accounts for the presence of tightly bound water. The first detailed incoherent inelastic neutron scattering (IINS) studies of such a system give a spectrum with distinct and sharp librational bands for bound water, significantly different than seen in ice Ih. Using these data, and by consideration of the crystal structure of dehydrated AlPO-14, we propose a model for the hydrated material in which the tightly bound water bridges pairs of Lewis acidic framework aluminums in a dense region of the structure, while loosely bound water resides in the pores of the solid. Further IINS measurements using a high-incident neutron energy provide data that are in agreement with our model. We can detect two O-H stretching modes for bound water in hydrated AlPO-14, consistent with the model of two types of water present in the material, with the loosely bound water connected to neighboring water molecules by intermolecular hydrogen bonds.