Hierarchical nanoporous structures were fabricated from mesoporous silica and organic monolith with the aim of fabricating a high-efficiency catalyst carrier. The hierarchical structures were modified with photocatalytic titanium clusters. The hierarchical structures showed higher photodecomposition rate of isopropyl alcohol than mesoporous silica structures or monolith structure did, even though the surface area of the hierarchical structure was the smallest. In addition, the CH 4 generation from CO 2 photoreduction on the hierarchical mesoporous structure was also confirmed. These results suggest the possibilities of highly efficient mass-transport property and the ease of chemical modification of our hierarchical structure.CO 2 reduction to hydrocarbons by harvesting solar energy is a promising approach since it may be the candidate to solve worldwide fuel crisis in the future, which is inevitable due to the long duration for formation of coal, natural gas, and oil. Recently, Toyota 1 and Panasonic 2 companies reported the success of artificial photosynthesis within a short time of one another, using the catalysis containing rare metals such as Re, Ga, and In. The TiO clusters were also reported as catalysts for the artificial photosynthesis. 36 As catalyst carriers, mesoporous siclica 711 such as MCM-41 (hexagonal phase), MCM-48 (cubic phase), and MCM-50 (lamellar structure) were employed by prominent researchers.We focused attention on the catalyst carrier. The pore size of the catalyst carrier consisting of the mesoporous silica is 210 nm. It was said that the catalyst with hierarchical structure would show high efficiency because of the efficient masstransport properties, 12 and this was proved by using a catalyst on zeolite.13 Here, we examined the preparation of such hierarchical structures using a mesoporous silica (MCM-48) and an organic monolith as a template. An organic monolith, that is a selforganized structure formed in polymer phase separation, itself has hierarchical network pores: The larger pores have 50 400 nm diameters, and the smaller pores have 2200 nm diameters. Moreover, an organic monolith powder of poly-(methyl methacrylate) is suitable for the templating process because of its decomposition behavior during calcination.14 The combination of such a monolith and MCM-48, that has threedimensional pores with 45 nm diameter, would lead us to fabricate an interesting hierarchical catalyst carrier.In this study, we fabricated two types of silica oxide monoliths and introduced TiO clusters in the prepared catalyst carriers; Ti-containing SiO 2 monoliths and Ti-modified mesoporous silica monolith, i.e., the former monolith was prepared without mesoporous silica, and the photocatalytic activities were examined.A silica monolith containing Ti atoms was prepared by a template method. 3.0 g of poly(methyl methacrylate) monolith particle (8¯m dia., MBP-8, Sekisui Plastics Co., Ltd.) was impregnated into the mixed solution of 5 mL of titanium tetraisopropoxide (TTIP) and 20 mL of tetraethyl orthosi...
