The structural change of intercalated iodine determined by the inner surface properties of ion-exchanged zeolite A

The inner-surface properties of zeolite A (LTA) were modified by the exchange of the charge-balancing non-framework cations (Li+, Na+, K+, Rb+, and Cs+). Molecular iodine, sorbed from the vapor phase, was used to probe these properties. The structure of molecular iodine, introduced via the vapour phase, is changed by these surface properties. Our results, based on techniques allowing access to the geometric (X-ray absorption fine structure), electronic (UV–Vis spectroscopy) and vibrational structure (Raman spectroscopy) of the iodine molecule show that the intercalated molecules located at the inner surface of the zeolite are strongly influenced by the electric fields determined by the cations (Li+, Na+, K+, Rb+, and Cs+). EXAFS and UV–Vis spectroscopy reveal changes in the average bond distances and the electronic structure. Interestingly, in Rb- and Cs-exchanged zeolites, triiodide anions are apparently formed. Since all of the observed changes can be related to the cations present in the cages, we can thus demonstrate that iodine is influenced by the inner surface properties of zeolites.