Photocatalytic activation of CO 2 under visible light by Rhenium complex encapsulated in molecular sieves
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Photocatalytic Activation of CO2 under Visible Light by Rhenium Complex Encapsulated in Molecular Sieves Jin-Soo Hwang, Dae Sung Kim, Chul Wee Lee and Sang-Eon Park+ Catalysis Center for Molecular Engineering (CCME), Korea Research Institute of Chemical Technology (KRICT), Daeieon 305-606, Korea (Recen,ed 7 September 2001 9 accepted 15 October 2001)
Abstract-The photocatalytic activation of CO, over molecular sieve-encapsulated catkmic rhenium complex has been investigated under visible light 1)v>350 nm). The cationic rhenium complex, [Re(l}lCOL(bpy}{py)] (bpy 2,2'bipyridine, p? pyridine), has been encapsulated by ion-exchange method t~sing the aqueous solution of [Re(I t(COL (bpyI(py J] PF,7 into the microporous NaY and the men,porous AIMCM-41 molecular sieve acting as supramolecular heterogenc, ous host. To conlinn the encapsulation of ]Re(lj(CO}_,(bpy)lp? )1' into the pores of molecular sieve, XeNMR and Vf-IR spectmscopies have been applied betbre m~d aRer the [Re{l)(CO)~(bpy)(py)]- encapsulation. To investigate the photophs, sical and photochemical properties, molecular sieve-encapsulated cationic rhenium complex has been studied by UV-Visiblc diflhse reflectance spectroscopy (UVq)RS) with phomirradiation (s nm) at room temperature. By monitoring the photoreaction of COe over the phot(~>atalysts, the conversion of CO, into CO and carbunate species has been observed by using/n-sire I:T-IR and time-resoDed mass spectroscopy, From the experimental results, the photocatalytic activation mechanism of CO_, on the catalyst under visible light 1s nml could be proposed via the photo-induced reaction of two dectmns and two protons, resu|th~g ti'om water decomposition. K W words: Catkmic Rhenium Complex. FI-IR, Mass Spectroscopy, Molecular Sieve. Photocatalytic Activation of COx. UV-DRS. Visible Light
the homogeneous soMion systems. Some effom have been reported in connection with encapsulation of rhmium complexes into zeolite and their photochemical application to CO_,activation [SungSuh et aL, 2000: Park et al,, 2000]. Based on host-guest interaction, molecular sieves have been used as heterogeneous host for the encapsulation of guest molecules such as oganic molecules, metal complexes and organometallic fragments [Bdn et al., 19%; Kim et aL 2001]. Such inorganic solid-state supramolecular systems generate the microheterogenization of the encapsulated molecular assemblies which show the photocatalytic activity. For zeolite-entrapped complexes, the steric and electrostatic constraint imlmsed on the complexes within the channels or cages of zeolites can alter the photochemical and photophysical properties of the guest complexes and diminish the p~todegradation and undesirable electron transfer reactions [Kim et at., 20011. In this study, [Re(CO~(bpyXpy)l ~ encapsulated in NaY and AIMCM41 molecular sieves was applied to photocatalytic activation of CO> The encapsulated cationic rhenium complex was character[zed by using F H R and Xe-NMR spectroscopies. The photoactiration of CO: on the catalyst was studied by UV-DRS, iJt
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