Complete redox exchange of indium for Tl+ in zeolite A. Synthesis and crystal structure of fully indium-exchanged zeolite A

Abstract

Indium has replaced all of the TIC ions in fully dehydrated fully Tl+-exchanged zeolite A by a solvent-free redox ion-exchange reaction with In metal at 623 K. The crystal structures of the zeolite before (Tl-12-A) and after the reaction, followed by washing with water and redehydration at 350 degrees C for 2 days (In-10-A . In), have been determined by single-crystal X-ray crystallography at 21 degrees C. In-10-A . In, eleven In atoms or ions per unit cell are distributed over seven crystallographically distinct positions. Seven In occupy three threefold-axis equipoints: four In+ ions lie opposite B-rings in large cavity, and two In2+ and one In+ lie opposite B-rings in the sodalite unit. Three In+ ions per unit cell are found at two different 8-ring positions, 1.5 on the 8-ring plane and 1.5 off. Finally, one In-0 atom per unit cell is found at two quite unusual positions: half an In-0 at the center of sodalite unit and the other half In-0 opposite a 4-ring relatively deep in the large cavity. These In atoms associate with In ions, likely forming (In-5)(8+) clusters in half of the sodalite units and (In-3)(2+) clusters in half of the large cavities.