Iodide-to-cation charge-transfer bands as a novel probe for evaluation of actual acceptor strengths of cations in zeolites and cation-dependent pore volume change

Iodide-to-cation charge-transfer (ITC-CT) bands have been measured for the first time in zeolites X and Y exchanged with a series of alkali metal ions and the results show that the ITC-CT band progressively red shifts with in creasing the size and the number of site III cations in the supercage, whic h indicates that the actual acceptor strength of the cation toward iodide i ncreases with increasing the degree of protrusion of the cation into superc ages and the number of cations, and overall, with decrease in supercage vol ume.