Theoretical investigations on the interaction of benzene with faujasite

The interaction of benzene with Faujasite (FAU) type structures with varying Si ∶ Al ratio and cation content has been analysed. Using the electronegativity equalization method (EEM), the charge perturbation of a benzene molecule located in the supercage (on the three-fold axis) and the interaction energies with the framework have been evaluated. On this basis two distinct adsorption sites have been identified in agreement with experiments. The relative strength of the benzene–framework interaction at either of these sites depends strongly on the aluminium content of the framework and, most importantly, on the nature of the charge-compensating cation. This dependence correlates with the electrostatic field gradient in the supercage.