ABINITIO STUDY OF CO ADSORPTION ON ZEOLITES

Ab initio self-consistent field Hartree-Fock (SCF-HF) calculations have been performed, using the 6-31G* basis set, to investigate the nature of the complexes formed between carbon monoxide and three cluster models, chosen to represent the acid sites in zeolites: AI(OH)3 for a Lewis site, H3Si(OH)AlH3 for a Bronsted site, and H3SiOH for a terminal hydroxyl. Three types of interaction with CO are considered for each model: through the carbon lone pair, through the oxygen lone pair, and through the pi-electron cloud. The geometries of the complexes are fully described. HF interaction energies are calculated, and corrections are made for BSSE and electron correlation (MP2 method). Stretching frequencies for CO and the model hydroxyls are determined. The theoretical data are compared to the experimental data available in the literature.