Preparation, Crystal Structure, and Luminescence Properties of Zeolite LTA Containing Extraframework Tantalum(V), Tantalum(II), Thallium(I), and Chloride

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• 作者：Hyeon Seung Lim ; Joon Young Kim ; Nam Ho Heo ; Karl Seff
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：June 9, 2016
• 年：2016
• 卷：120
• 期：22
• 页码：12139-12148
• 全文大小：580K
• 年卷期：0
• ISSN：1932-7455

文摘

For the first time pentapositive cations have been introduced into a zeolite at extraframework positions. Their presence was confirmed by single-crystal crystallography using synchrotron X-radiation and energy-dispersive X-ray analysis. It was prepared by the thallous ion exchange (TIE) method: fully dehydrated Tl<sub>12sub>-LTA was treated with 3.0 × 10<sup>4sup> Pa of TaCl<sub>5sub>(g) at 473 K. The crystal structure of the product, |Ta<sup>2+sup><sub>0.123sub>(TaCl<sub>6sub>Tl<sub>3sub>)<sup>2+sup><sub>0.246sub>Tl<sup>+sup><sub>9.84sub>|[Si<sub>13.4sub>Al<sub>10.6sub>O<sub>48sub>]-LTA, was refined in the space group Pm3̅m (a = 12.099(1) Å) with all unique data to the final error index R<sub>1sub> = 0.044 for the 639 reflections for which F<sub>osub> > 4σ(F<sub>osub>). TIE did not occur. Instead some TaCl<sub>5sub> molecules decomposed to TaCl<sub>2sub> and Cl<sub>2sub>(g), and TaCl<sub>2sub> reacted with additional TaCl<sub>5sub> molecules to form Ta<sup>2+sup> and TaCl<sub>6sub><sup>–sup>. Octahedral TaCl<sub>6sub><sup>–sup> ions center about 24.6% of the large cavities. Each Cl<sup>–sup> ion bonds to a Tl<sup>+sup> ion in the plane of an 8-ring to form a TaCl<sub>6sub>Tl<sub>3sub><sup>2+sup> continuum in the near-surface volume of the crystal. The Ta<sup>2+sup> ions, 0.123(3) per unit cell, lie opposite 6-rings in the large cavities. All Tl<sup>+sup> ions occupy well-established cation positions near 6- and 8-rings. The photoluminescence spectrum of this material is a broad emission band between 350 and 500 nm, peaking at 410 nm.