Abstract: The structure and Bronsted acidity of H-AlMOR and H-BMOR as well as their adsorption for pyridine probe molecule were investigated by using a 24T cluster containing a two-layered 12-membered ring and ONIOM2 (QM/QM and QM/MM) hybride methods. The Bronsted acidity of H-AlMOR is stronger than that of H-BMOR. Pyridine adsorption energy on H-AlMOR of 219.3 kJ/mol calculated by ONIOM2 (QM/QM) method compares well with the experimental result of 200 kJ/mol. In addition, the structure and IR stretching frequencies of the adsorption complexes shows that proton transfer occurrs during the pyridine adsorption, and the PyH+…ZeO- ion pairs are further stabilized by multiple hydrogen bonding between the hydrogen atoms of pyridine and the framework oxygen atoms of the zeolite.

Key words: mordenite, pyridine, adsorption, ONIOM method, quantum chemistry