Prestipino C, Solari P L, Lamberti C
Department of Inorganic, Physical and Materials Chemistry and NIS Centre of Excellence, Via P. Giuria 7, I-10125 Torino, Italy.
J Phys Chem B. 2005 Jul 14;109(27):13132-7. doi: 10.1021/jp050183h.
In this work, we report state-of-the-art analysis of both Ti K-edge high-resolution XANES and EXAFS data collected on the ETS-10 molecular sieve at the GILDA BM8 beamline of the ESRF facility. The interatomic distances and the angles obtained in our EXAFS study are in fair agreement with the single-crystal XRD data of Wang and Jacobson (Chem. Commun. 1999, 973) and with the recent ab initio periodic study of Damin et al. (J. Phys. Chem. B 2004, 108, 1328) Differently from previous EXAFS work (J. Phys. Chem. 1996, 100, 449), our study supports a model of ETS-10 where the Ti atoms are bonded with two equivalent axial oxygen atoms. This model is also able to reproduce the edge and the post-edge region of the XANES spectrum. Conversely, the weak but well-defined pre-edge peak at 4971.3 eV can be explained only by assuming that a fraction of Ti atoms are in a local geometry similar to that of the pentacoordinated Ti sites in the ETS-4 structure. These Ti atoms in ETS-10 should be the terminal of the -Ti-O-Ti-O-Ti- chains, of which the actual number is strongly increased by the high crystal defectivity (Ti vacancies).
在本工作中，我们报告了在欧洲同步辐射装置（ESRF）的GILDA BM8光束线上收集的ETS - 10分子筛的Ti K边高分辨率X射线吸收近边结构（XANES）和扩展X射线吸收精细结构（EXAFS）数据的前沿分析。我们EXAFS研究中获得的原子间距离和角度与Wang和Jacobson（《化学通讯》，1999年，973页）的单晶X射线衍射（XRD）数据以及Damin等人最近的从头算周期性研究（《物理化学杂志B》，2004年，108卷，1328页）相当吻合。与之前的EXAFS工作（《物理化学杂志》，1996年，100卷，449页）不同，我们的研究支持ETS - 10的一种模型，其中Ti原子与两个等效的轴向氧原子键合。该模型也能够重现XANES光谱的边缘和后边缘区域。相反，4971.3 eV处微弱但明确的预边缘峰只能通过假设一部分Ti原子处于与ETS - 4结构中五配位Ti位点类似的局部几何结构来解释。ETS - 10中的这些Ti原子应该是 -Ti - O - Ti - O - Ti - 链的末端，由于高晶体缺陷率（Ti空位），其实际数量大幅增加。
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