A layered tungstic acid H2W2O7 x nH2O with a double-octahedral sheet structure: conversion process from an aurivillius phase Bi2W2O9 and structural characterization.
A layered tungstic acid H2W2O7 x nH2O with a double-octahedral sheet structure: conversion process from an aurivillius phase Bi2W2O9 and structural characterization.
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DOI：
10.1021/ic0206746
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发表时间：
2003-06
影响因子：
4.6
通讯作者：
M. Kudo;H. Ohkawa;W. Sugimoto;N. Kumada;Zheng Liu;O. Terasaki;Y. Sugahara
中科院分区：
文献类型：
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作者：
M. Kudo;H. Ohkawa;W. Sugimoto;N. Kumada;Zheng Liu;O. Terasaki;Y. Sugahara
研究了 Aurivilius 相 Bi(2)W(2)O(9) 通过盐酸处理转化为层状钨酸的过程，并充分表征了生成的 H(2)W(2)O(7) x nH(2)O。在环境温度干燥的酸处理产品中，Bi(2)W(2)O(9)的c参数[2.37063(5) nm]降低至2.21(1) nm。在环境温度下干燥的酸处理产物中，Bi(2)W(2)O(9)的a和b参数[a = 0.54377(1) nm和b = 0.54166(1) nm]也略有下降至a = 0.524(1) nm和b = 0.513(1) nm，这表明Bi(2)W(2)O(9)中ReO(3)样板的结构变化酸处理。在 120 摄氏度下干燥导致 c 参数 [1.86(1) nm] 进一步下降，而 a 和 b 参数 [a = 0.5249(2) nm 和 b = 0.513(2) nm] 没有显着变化。正辛胺[层间距离2.597(9) nm]和正十二胺[层间距离3.56(2) nm]的成功嵌入证明了可膨胀层状结构的形成。酸处理产品的组成确定为 H(2)W(2)O(7) x nH(2)O，其中风干产品的 n = 0.58，120℃干燥的产品 n = 0。因此，该层的组成为 H(2)W(2)O(7)，干燥时 c 参数的降低归因于层间水的损失。扫描电子显微镜显示酸处理过程中没有形态变化，这强烈表明氧化铋片的选择性浸出是一种反应机制。酸处理产品的高分辨率透射电子显微镜 (HREM) 观察显示与 H(2)W(2)O(7) 的结构模型一致，H(2)W(2)O(7) 是通过去除氧化铋片并沿 c 轴收缩而衍生自 Bi(2)W(2)O(9)。 HREM 观察还表明，酸处理后 WO(6) 八面体排列略有变化。在 120 摄氏度下干燥的产品 H(2)W(2)O(7) 投影在 c 轴上的一维电子密度图与结构模型计算结果显示出良好的一致性。
The conversion process of an Aurivillius phase, Bi(2)W(2)O(9), into a layered tungstic acid by hydrochloric acid treatment has been investigated, and resultant H(2)W(2)O(7) x nH(2)O has been fully characterized. The c parameter of Bi(2)W(2)O(9) [2.37063(5) nm] decreases to 2.21(1) nm in an acid-treated product dried at ambient temperature. The a and b parameters of Bi(2)W(2)O(9) [a = 0.54377(1) nm and b = 0.54166(1) nm] also decrease slightly to a = 0.524(1) nm and b = 0.513(1) nm in the acid-treated product dried at ambient temperature, indicating structural changes in the ReO(3)-like slabs in Bi(2)W(2)O(9) upon acid treatment. Drying at 120 degrees C leads to a further decrease in the c parameter [1.86(1) nm] with no notable change in the a and b parameters [a = 0.5249(2) nm and b = 0.513(2) nm]. The formation of an expandable layered structure is demonstrated by the successful intercalation of n-octylamine [interlayer distance 2.597(9) nm] and n-dodecylamine [interlayer distance 3.56(2) nm]. The compositions of the acid-treated products are determined to be H(2)W(2)O(7) x nH(2)O typically with n = 0.58 for the air-dried product and n = 0 for the product dried at 120 degrees C. As a consequence, the composition of the layer is H(2)W(2)O(7), and the decrease in the c parameter upon drying is ascribable to the loss of interlayer water. Scanning electron microscopy reveals no morphological change during acid treatment, which strongly suggests a selective leaching of the bismuth oxide sheets as a reaction mechanism. High-resolution transmission electron microscopy (HREM) observation of the acid-treated product shows consistency with a structural model for H(2)W(2)O(7), derived from Bi(2)W(2)O(9) through removal of the bismuth oxide sheets and contraction along the c axis. HREM observation also reveals that the WO(6) octahedra arrangement changes slightly with acid treatment. A one-dimensional electron density map projected on the c axis for the product dried at 120 degrees C, H(2)W(2)O(7), shows good consistency with that calculated for the structural model.