Optical spectra of Co-zeolites

The coordination changes of CoII in A, X, Y zeolites, dried at high temperature, have been investigated by diffuse reflectance spectroscopy. Fully hydrated zeolites show an octahedral coordination of CoII. During dehydration at high temperature, CoII in X and Y zeolite changes its coordination, first from symmetric to a distorted tetrahedral and, successively, to an octahedral coordination.CoII in A zeolite, changes its coordination from slightly distorted tetrahedral to threefold.The formation of Co oxide species has been observed during calcination at high temperature of CoX and CoY.The rate sequence of re-hydration of species dehydrated at high temperature, is CoA CoY > CoX.