Arrayed PbI2 clusters in the spaces of zeolite LTA

Zeolite LTA has cubic symmetry with different-sized alpha- and beta -cages arranged in a CsCl type structure. PbI2 clusters were incorporated into the cages of LTA through a vapor phase after dehydration. The structure of thi s complex system was studied as a function of cluster loading by X-ray diff raction (both single crystal and powder) and by electron microscopy. The cl usters were formed inside the cc-cages without destroying the framework and with a maximum loading density of ca. 3.8 PbI2 clusters per cc-cage. No sy mmetry changes were observed except for the specimens with the maximum load ing. 3.8 PbI2 /LTA showed a domain structure, and more than two different t ypes of superlattice reflections were observed. The major phase has tetrago nal symmetry, P4/ncc, and the structures and the arrangements of the cluste rs are discussed. (C) 2001 Elsevier Science B.V. All rights reserved.