Determination of Electronic Recombination Free Energy in Zeolites: Effects of the Charge Balancing Cation and Confinement.

The adsorption of DPH in M6.6 ZSM-5 (M=Na+ , K+ , Rb+ , Cs+ ), RbFER and RbMOR channel zeolites takes place without chemical or structural modification. After photoexcitation of these systems, a radical cation-electron pair is observed and has a sufficiently long lifetime to be studied by diffuse reflectance UV-visible spectroscopy. The study of the recombination of this radical cation-electron pair was carried out at different temperatures and allowed the determination of the activation energy as a function of the nature of the charge-balancing cation but also of the confinement effect. It appears that the activation energy decreases progressively from Na+ to Cs+ but also when the confinement decreases. To go further, the free enthalpies have been calculated from the Marcus theory demonstrating experimentally that these systems are located in the inverted Marcus region.