The two-layered ONIOM method (B3LYP/6-31G(d,p):HF/3-21G) has been used to investigate the structure and energy of Li- and Na-exchanged MOR with amines (NH3, NH2Me, NHMe2 and NMe3). It is shown that the coordination of amine nitrogen to the zeolite alkali cation dominates the overall interaction. In addition, the adsorption complexes are further stabilized by weak hydrogen bonding between the negatively charged zeolite framework oxygen atoms and the hydrogen atoms of amines. The Lewis basicity based on the calculated adsorption energies in the order of NMe3 < NH3 < NHMe2 < NH2Me is different from their relative Bronsted basicity derived from the adsorption oil H-MOR. The adsorption energy of amines on Li- and Na-MOR only amounts to about 63-72 and 71-87% of the binding energy of the naked Li+ and Na+ with amines, respectively. (c) 2005 Elsevier B.V. All rights reserved.