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 AlMCM-41 molecular sieve acting as supramolecular heterogeneous host. To confirm the encapsulation of [Re(I)(CO)(3)(bpy)(py)](+) into the pores of molecular sieve, Xe-NMR 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 using in-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.