| Ti-MWW分子筛正弦孔道内骨架钛物种的结构和红外振动光谱的理论计算 |
| Theoretical Calculation on the Structure and Vibratioanl Spectra of Framework Titanium Located in Sinusoidal Channel of Ti-MWW |
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| 摘要: 应用密度泛函理论计算,研究了Ti-MWW分子筛10元环正弦孔道内骨架钛物种的结构和振动光谱。计算采用基于36T簇模型的B3LYP/6-31G(d,p)方法,确定了[Ti(OSi)4]物种优先落位于T3位,在924~987cm-1区域内存在3个振动峰,都属于以Ti为正四面体中心分布的4个Ti-O-Si键的协同伸缩振动,其中958cm-1的振动强度较大,属于[Ti(OSi)4]的特征频率。T2和T8位上钛物种不出现该特征峰。Ti(Ⅳ)中心上吸附一个水分子形成五配位配合物,其特征振动频率没有变化。[Ti(OSi)4]物种进一步水解形成[Ti(OSi)3OH]物种,其Ti-O-Si的特征振动蓝移到969cm-1。此外,还考察了Ti-MWW分子筛中可能存在的骨架硼以及羟基巢的结构和振动光谱,计算频率与已有文献数据相符。 |
| 关键词: 密度泛函理论 振动光谱 Ti-MWW B-MWW 骨架Ti结构 |
| 基金项目: 国家自然科学基金(No.21343010)资助项目。 |
| Abstract: Density functional theory was applied to study the structure and vibratioanl spectra of framework titanium located in the 10-membered ring channel of Ti-MWW. The calculations were carried out at B3LYP/6-31G(d,p) level of theory based on the 36Tcluster models, leading to the results that the [Ti(OSi)4] species prefer to locate at the T3 site. The stretching vibrations correlated to [Ti(OSi)4] occur between 924~987 cm-1, including three vibrational modes as the collection of asymmetric stretching motions of four Ti-O-Si centred on tetrahedral Ti(Ⅳ) center, in which the strongest band at 958 cm-1 is attributed to the Ti-specific vibrational frequency. The 960 cm-1 band is absent from the Ti-species at the T2 and T8 sites. Adsorption of H2O on Ti(OSi)4 has no influence on the 960 cm-1 band. The hydrolysis of [Ti(OSi)4] resulted in [Ti(OSi)3OH], showing the Ti-specific vibrational frequency shifted to 969 cm-1. In addition, we also explored the structures and vibrational spetra of framework boron and hydroxyl nest. The calculated frequencies are in good agreement with the reported experimental values. |
| Keywords: density functional theory vibrational spectroscopy Ti-MWW B-MWW structure of framework Ti |
| 投稿时间：2014-11-10 修订日期：2015-03-05 |
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| 李娜,蒋艳娇,乔溢铭,周丹红.Ti-MWW分子筛正弦孔道内骨架钛物种的结构和红外振动光谱的理论计算[J].无机化学学报,2015,31(5):901-907. |
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