Effects of the zeolite particle size on the charge separated states

•MFI-type zeolites with crystallite size ranging from nm to μm were synthesized.•Influence of the zeolite crystal size on the electron transfers occurring in their pores.•ZSM-5 zeolite can act as strong electron acceptor or electron donor.•Unexpected stabilization of the radical cation in ZSM-5 nanosheets.

Electron transfers occurring after sorption and photoexcitation of p-terphenyl molecules in the porous void of two MFI type zeolites were investigated. The influence of the morphology and particle size, i.e.; nanosheets and conventional coffin-shaped micron sized crystals (big crystals) on these phenomena were emphasized. The irradiation of PTP occluded in big crystals induces the formation of a radical cation which evolves to an electron-hole pair through the capture of another electron of zeolite. In contrast, if photoexcitation of PTP incorporated in nanosheets induces also radical cation, it is interesting to note that the electron-hole pair formation is not favored in such environment. The absence of charge compartmentalization within nanosheets is put forward to explain the inhibition of electron transfer to create the charge transfer complex. Indeed, the small thickness of nanosheets prevents electron hopping over long distance after ionization and consequently, as the electron is trapped nearby the radical cation, direct recombination is favored.

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