Ab initio study of single and double point adsorption of carbon monoxide on clusters representing zeolites

The interaction of carbon monoxide with clusters chosen to represent Bronst ed acid sites, and framework basic sites, in zeolites has been investigated using molecular orbital calculations. In agreement with our previous studi es, the interaction of a single protic hydrogen with the carbon atom of CO is energetically preferred over interaction via the oxygen, but the present work shows that a two-point interaction of carbon monoxide via both carbon and oxygen is energetically favoured when protic hydrogens are sufficientl y close. Investigation of a possible two-point interaction involving carbon monoxide linked to a protic hydrogen, by either the carbon or the oxygen, with further interaction between uncomplexed O or C and neighbouring framew ork atoms could not be established for the size of cluster and level of cal culation used. Similarly, there was no clear evidence for complexing of CO by a single point interaction with oxygens in the Si-O-Si bridge. The effec t of complexing on stretching frequencies, v(CO) and v(OH) is discussed.