Abstract: An ONIOM study at B3LYP and M05-2X level was carried out to investigate thiophene cracking in a Brönsted acidic zeolite and the effect of the zeolite framework on the geometry, electronic structure, and energy of the intermediates. The zeolite framework stabilized positively charged transition states and lowered the reaction barriers. The newly developed M05-2X functional performed much better than the popular B3LYP functional for describing non-bonded interactions between the reactants and the zeolite framework, which gave more accurate electronic structures and energy barriers. The rate determining barrier was that for electrophilic aromatic substitution (122.4 kJ/mol), while the subsequent C–S bond dissociation has a lower barrier (75.5 kJ/mol).

Key words: ONIOM, M05-2X, zeolite framework, thiophene cracking, density functional theory