Photocatalytic activation of CO₂ under visible light by Rhenium complex encapsulated in molecular sieves

The photocatalytic activation of CO₂ over molecular sieve-encapsulated cationic rhenium complex has been investigated under visible light (λ>350 nm). The cationic rhenium complex, [Re(I)(CO)₃(bpy)(py)]⁺(bpy=2,2′bipyridine, py=pyridine), has been encapsulated by ion-exchange method using the aqueous solution of [Re(I)(CO)₃ (bpy)(py)]⁺PF₆^- into the microporous NaY and the mesoporous A1MCM-41 molecular sieve acting as supramolecular heterogeneous host. To confirm the encapsulation of [Re(IXCO)₃(bpy)(py)]⁺ into the pores of molecular sieve, XeNMR and FT-IR spectroscopies have been applied before and after the [Re(I)(CO)₃(bpy)(py)]⁺ encapsulation. To investigate the photophysical and photochemical properties, molecular sieve-encapsulated cationic rhenium complex has been studied by UV-Visible diffuse reflectance spectroscopy (UV-DRS) with photoirradiation (λ>350 nm) at room temperature. By monitoring the photoreaction of CO₂ over the photocatalysts, the conversion of CO₂ into CO and carbonate species has been observed by usingin-situ FT-IR and time-resolved mass spectroscopy. From the experimental results, the photocatalytic activation mechanism of CO₂ on the catalyst under visible light (λ>350 nm) could be proposed via the photo-induced reaction of two electrons and two protons, resulting from water decomposition.