Photoreduction of carbondioxide on surface functionalized nanoporous catalysts

Nanoporous photocatalysts have been designed to exhibit unique photocatalytic activities through framework substitution of titanium species or surface immobilization of rhenium complex onto mesoporous silica. This article summarizes recent work on the synthesis, characterization and photocatalytic activities of the designed porous photocatalysts performed by the present authors. Various spectroscopic investigations revealed that the photo-excited states of these catalysts play a vital role in the photocatalytic reactions and their photocatalytic reactivities are strongly dependent on structures of active sites, which are confined and immobilized in the restricted framework structure of the mesoporous silica. Highly dispersed titanium oxide species incorporated in the framework of mesoporous silica exhibited high and unique photocatalytic reactivity for the reduction of CO(2) with H(2)O to produce CH(4) and CH(3)OH under UV irradiation, its reactivity being much higher than bulk TiO(2). The cationic rhenium(I) complex was encapsulated into a mesoporous AlMCM-41 material by ion-exchange method, yielding a visible light photocatalyst to be active for photocatalytic reduction of CO(2).