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

Abstract

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|[Si13.4Al10.6O48]-LTA, was refined in the space group Pm3m (a = 12.099(1) A) with all unique data to the final error index R1 = 0.044 for the 639 reflections for which Fo > 4σ(Fo). 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, ...