Long Lived Charge Separated States Induced by trans-Stilbene Incorporation in the Pores of Brønsted Acidic HZSM-5 Zeolites: Effect of Gallium on the Spontaneous Ionization Process

In situ CW-EPR, diffuse reflectance UV−visible spectroscopy and Raman scattering were used to monitor the spontaneous incorporation of trans-stilbene (t-St, C14H12) in the medium pore H2.2-GaZSM-5 zeolites [H2.2(GaO2)2.2(SiO2)93.8] by direct exposure under dry and inert atmosphere of solid t-St to dehydrated porous material without any solvent. The sorption of t-St with relatively low ionization potential (7.65 eV) occurs in Bronsted acidic H2.2-GaZSM-5 zeolites according to a complex and slow reaction sequence. First, charge separation occurs and t-St•+@H2.2-GaZSM-5•− radical pair is created, while long-lived t-St@H2.2GaZSM-5•−•+ electron−hole pair is formed through hole transfer. The analysis of the DRUVv spectra set recorded during the t-St sorption course shows the respective concentrations of all transient species as a function of time. In particular, note that system reorganization is observed through a second type of electron−hole pair. The broad and strong bands observed in the near-IR regions ove...