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 Tl₁₂-LTA was treated with 3.0 × 10⁴ Pa of TaCl₅(g) at 473 K. The crystal structure of the product, |Ta²⁺_0.123(TaCl₆Tl₃)²⁺_0.246Tl⁺_9.84|[Si_13.4Al_10.6O₄₈]-LTA, was refined in the space group Pm3̅m (a = 12.099(1) Å) with all unique data to the final error index R₁ = 0.044 for the 639 reflections for which F_o > 4σ(F_o). TIE did not occur. Instead some TaCl₅ molecules decomposed to TaCl₂ and Cl₂(g), and TaCl₂ reacted with additional TaCl₅ molecules to form Ta²⁺ and TaCl₆^–. Octahedral TaCl₆^– ions center about 24.6% of the large cavities. Each Cl^– ion bonds to a Tl⁺ ion in the plane of an 8-ring to form a TaCl₆Tl₃²⁺ continuum in the near-surface volume of the crystal. The Ta²⁺ ions, 0.123(3) per unit cell, lie opposite 6-rings in the large cavities. All Tl⁺ 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.