日本ゼオライト学会　刊行物 Publication of Japan Zeolite Association

Synthesis of non-siliceous mesoporous metal oxides has attracted tremendous attention in materials community. Among various morphologies of mesoporous materials, ordered mesoporous films are very attractive for applications in electronics, optics, sensing, etc. Control of the pore architectures in the films, such as vertical mesoporosity and large-sized mesopores, has a significant effect on performance in these applications. Compared to closed pores and cage-type pores, connected mesoporosity allows more effective pore utilization. In particular, vertically connected mesoporosity is much more desirable than horizontally connected mesoporosity, because the vertical orientation exhibits better diffusion of the guest species into the inner mesospace. Unfortunately, 2D hexagonal mesostructures generally tend to lie on the substrate surface. Although some special techniques, such as use of a patterned substrate and magnetic field, have been applied to the creation of vertical mesoporosity in mesoporous silica films, the preparation of non-siliceous mesoporous metal oxide films with vertical mesoporosity is still very challenging and requires further studies. In addition to the pore orientation, it is also very important to fabricate large mesopores since they facilitate the diffusion of guest molecules and can be utilized in emerging applications such as biotechnology involving large target species. In principle, the pore size is determined by the templating micelle. Using long chain surfactants of high molecular weight enables fabrication of ordered large-sized mesoporous materials. It has been recently proven that block copolymers with high molecular weights and big differences in hydrophobicity between the blocks can be directly utilized for the formation of large mesopores. A more facile and straightforward process for synthesizing mesoporous films with desired pore architectures is still needed. In this review, we summary recent progress in the synthesis and applications of non-siliceous mesoporous metal oxide films.