Basicity of the framework oxygen atom of alkali and alkaline earth-exchanged zeolites: a hard–soft acid–base approach

The basicity of framework oxygen atoms of alkali and alkaline earth-exchanged zeolites has been studied using reactivity descriptors based on a local hard–soft acid–base (HSAB) concept. We have calculated the `local softnessʹ and the `relative nucleophilicityʹ values of the framework oxygen atoms of zeolite clusters as the measure of basicity. The local softness and relative nucleophilicity appear to be more reliable descriptors to predict the experimental basicity trend, compared to the negative charge on the oxygen atom.