Positions of cations and molecules in zeolites with the chabazite framework. IV Hydrated and dehydrated Cu 2+-exchanged chabazite

Abstract

Chabazite from Bozen, Tyrol was ion-exchanged with KCl and further exchanged with CuCl 2 solution to Cu 1.8K 0.2Al 3.9Si 8.1O 24.nH 2O. Both the hydrated and dehydrated structures were determined at room temperature. Cell dimensions in R3m are: hydrated a 9.411(2)Å α 95.31(1)°; vacuum-dehydrated at 350°C a 9.310(2)Å α 92.01(2)°. All Cu 2+ ions of d-Cu-chabazite were located near the center of the 6-ring, 1.97Å from three 0(4) and 2.83Å from three 0(3). Displacement of Cu 2+ by 0.15Å into the large cage from a position for triangular coordination to three 0(4) may result from either an attempt to reach a Jahn-Teller distorted tetrahedral coordination, or electrostatic repulsion from another Cu 2+ across the ditrigonal prism, or both. The T-O distances increase as the T-O-T angles decrease. Interpretation of the electron density of h-Cu-chabazite is uncertain, but all Cu 2+ ions and water molecules are in the large cage, perhaps as hydration complexes with Jahn-Teller distortion.