Combined spectroscopic and modeling study of trans-stilbene molecule in cation-exchanged ZSM-5 zeolites

Matthieu Hureau (1) , Alain Moissette (1) , Konstantin Smirnov (1) , Hervé Jobic (2)

1 LASIRE - Laboratoire Avancé de Spectroscopie pour les Intéractions la Réactivité et l'Environnement - UMR 8516
2 IRCELYON - Institut de recherches sur la catalyse et l'environnement de Lyon

A variety of spectroscopic methods and molecular modeling were used to characterize trans-stilbene (t-St) molecules sorbed in aluminum rich M-ZSM-5 zeolites (M⁺ = Na⁺, K⁺, Rb⁺, Cs⁺). The Monte Carlo simulations followed by the energy minimization predict the t-St sorption in the straight channels in close proximity of the extra-framework M⁺ ions. The effects of the interactions between the guest molecules and host zeolite lattice on the electronic states are examined experimentally by the diffuse reflectance UV-visible absorption and fluorescence emission, whereas the vibrational states are studied by means of Raman scattering, infrared absorption, and inelastic neutron scattering techniques. The changes observed in the spectra are found to depend on type of charge-balancing cation and to intensify with the increase in cation size. Comparison of experimental data and results of quantum-chemical calculations allows explaining the features observed in the Raman spectra of the systems. Results of the study lead to the conclusion that the properties of occluded t-St molecules are mainly governed by molecule-cation interactions, whereas the confinement by zeolite lattice imposes sterical hindrances on the possible conformations of t-St/cation complexes.

Domaines: Chimie théorique et/ou physique

Matthieu Hureau, Alain Moissette, Konstantin Smirnov, Hervé Jobic. Combined spectroscopic and modeling study of trans-stilbene molecule in cation-exchanged ZSM-5 zeolites. Journal of Physical Chemistry C, 2012, 116, pp.15510-15518. ⟨10.1021/jp305631q⟩. ⟨hal-00779696⟩