Multinuclear solid-state NMR study of cadmium- and lead-exchanged LTA zeolites

This paper describes Si-29, Al-27, Pb-207 and Cd-113 NMR studies of Pb- and Cd-exchanged LTA zeolites. The Cd-113 NMR spectra identify for the first time two different coordination states for Cd2+ in hydrated CdLTA, consistent with x-ray single crystal diffraction data for this zeolite. The effects of Cd2+ exchange on the Si-29 NMR spectra of LTA are also consistent with the structural data. Cd2+ exchange perturbs the Al-27 NMR spectrum of the zeolite, as does Pb2+ exchange. Changes in the Si-29 NMR spectra on Pb2+ exchange are explained in terms of structural distortion of the framework. Pb-207 NMR spectra of Pb2+ exchanged LTA show a single broad signal indicating that Pb2+ cations are rigidly located in the zeolite at relatively long Pb-O distances in the hydrated zeolites. Copyright (C) 1999 John Wiley & Sons, Ltd.