Res. Chem. Intermed. , Vol. 30, No. 2, pp. 207– 233 (2004) Ó VSP 2004. Also available online - www.vsppub.com Characteristics of excited-state intermediates of TiO 2 –Y-Zeolite and MCM41 encapsulating photosensitive molecules: design of new photocatalysts MINJOONG YOON ¤ and SU YOUNG RYU Molecular Photophysics and Photofunctional Nanomaterials Laboratory, Department of Chemistry, Chungnam National University, Daejeon 305-764, South Korea Received 30 July 2003; accepted 19 September 2003 Abstract —Some photosensitive molecules, such as p-N,N 0 -dimethylaminobenzoic acid (DMABA), Nile Red, heteropolytungsticacid (H 3 PW 12 O 40 , HPA) and metalloporphyrins, have been entrapped onto nano-scale pores or channels of TiO 2 -modied Y-Zeolite (TiO 2 –Y-Zeolite) and MCM41 (TiO 2 – MCM41) and their excited-state intermediates have been characterized in terms of the excited-state dynamics by using laser spectroscopic techniques. Through these studies, it has been found that the photo-induced electrons are generated from the intramolecular charge transfer (ICT) state of DMABA, Nile Red or metalloporphyrin(MnTPP(Cl)), followed by transferringto the TiO 2 –Y-Zeolite or TiO 2 –MCM41 more efciently as compared to the bulk TiO 2 , NaY-Zeolite or MCM41. The efcient photoinduced interfacial electron transfer causes the rapid formation of radicals of those photosensitive molecules (a few tens ps). It has been also found that these photophysical properties can be applied to develop the new photocatalyst as observed by the efcient photocatalytic activities of the DMABA or Nile Red-entrapped TiO 2 –Y-Zeolites for the photoreduction of an azo-dye such as Methyl Orange in water. On the other hand, in case of HPA-entrapped TiO 2 –Y-zeolite, the electron generated from the excited-state TiO 2 is transferred to HPA, followed by formation of the reduction product, heteropoly blue (HPB) which is also generated by UV irradiation of HPA. This electron transfer is analogous to the Z-scheme mechanism of plant photosyntheticsystems showing two photon reactions. Because of this photoelectron transfer mechanism, the HPA-entrapped TiO 2 –Y-zeolite has demonstrated the synergisticenhancement of the photocatalyticdecomposition of Methyl Orange and hydrogen generation from photolysis of water. Keywords: TiO 2 ; MCM41; zeolite; excited-state intermediate; Z-scheme; photo-induced electron transfer; laser spectroscopic techniques. ¤ To whom correspondence should be addressed. Tel.: (82-42) 821-6546. Fax: (82-42) 823-7008. E-mail: mjyoon @cnu.ac.kr