Synthesis and Crystal Structure of Ag4Br4 Nanoclusters in the Sodalite Cavities of Fully K+-Exchanged Zeolite A (LTA)

• Published in: Bulletin of the Korean Chemical Society 2005, 26(7), , pp.1090-1096
• Main Authors: 임우택, 최식영, 김복조, 김창민, In Su Lee, 김석한, 허남호
• Format: Article
• Language: English
• Subjects: 화학
• ISSN: 0253-2964; 1229-5949
• DOI: 10.5012/bkcs.2005.26.7.1090

Ag4Br4 nanoclusters have been synthesized in about 75% of the sodalite cavities of fully K+-exchanged zeolite A (LTA). An additional KBr molecule is retained in each large cavity as part of a near square-planar K4Br3+ cation. A single crystal of Ag12-A, prepared by the dynamic ion-exchange of Na12-A with aqueous 0.05 M AgNO3 and washed with CH3OH, was placed in a stream of flowing 0.05 M KBr in CH3OH for two days. The crystal structure of the product (K9(K4Br)Si12Al12O48•0.75Ag4Br4, a = 12.186(1) Å) was determined at 294 K by single-crystal X-ray diffraction in the space group Pm m. It was refined with all measured reflections to the final error index R1 = 0.080 for the 99 reflections for which Fo > 4(Fo). The thirteen K+ ions per unit cell are found at three crystallographically distinct positions: eight K+ ions in the large cavity fill the six-ring site, three K+ ions fill the eight-rings, and two K+ ions are opposite four-rings in the large cavity. One bromide ion per unit cell lies opposite a four-ring in the large cavity, held there by two eight-ring and two six-ring K+ ions (K4Br3+). Three Ag+ and three Br ions per unit cell are found on 3-fold axes in the sodalite unit, indicating the formation of nano-sized Ag4Br4 clusters (interpenetrating tetrahedra; symmetry Td; diameter ca. 7.9 Å) in 75% of the sodalite units. Each cluster (Ag-Br = 2.93(3) Å) is held in place by the coordination of its four Ag+ ions to the zeolite framework (each Ag+ cation is 2.52(3) A from three six-ring oxygens) and by the coordination of its four Br ions to K+ ions through six-rings (Br-K = 3.00(4) A). KCI Citation Count: 9