Field-Induced alignment controls of one-dimensional mesochannels in mesoporous materials

Abstract

Mesoporous materials prepared through the self-assembly of surfactants have attracted wide attention because of their many potential applications. The mesostructural, compositional, and morphological controls of mesoporous materials have been extensively studied thus far. In particular, the macroscopic alignments of one-dimensional (1D) mesochannels and their controls are quite important for the creation of advanced functional materials. In most cases, the direction of mesochannels in mesoporous films lies parallel to the substrate. Vertical orientation of the mesochannels can realize high diffusion and accessibility of guest species from the outside. Here, I review the recent progress on this emerging research field. Various methods have been proposed for the preparation of vertically oriented mesoporous thin films using high magnetic field, shear flow, modification of the substrate, and other methods. I also briefly introduce their applications and a perspective for the future.©2013 The Ceramic Society of Japan. All rights reserved.Key-words : Mesoporous material, Surfactant, Thin film, High magnetic processing [Received April 25, 2013; Accepted June 23, 2013] 1. Mesoporous materials by self-assembly of surfactants Ordered mesoporous materials prepared through 'self-assembly of surfactants' have attracted growing interest due to their special properties, including uniform mesopores (250 nm) and high specific surface areas. 1),2) According to the International Union of Pure and Applied Chemistry (IUPAC), porous materials are classified according to their pore sizes: microporous materials with pore sizes below 2 nm, mesoporous materials with pore sizes between 2 and 50 nm, and macroporous materials with pore sizes exceeding 50 nm.3),4) Zeolites are traditional microporous materials that have been utilized for practical applications in catalysts and adsorbents. Although the microporous materials have high surface areas, due to their small-sized pores, their applications are limited to reactions only for relatively small molecules. Recently, metalorganic frameworks (MOFs) or porous coordination polymers (PCPs) consisting of metal ions coordinated with organic molecules have been extensively studied and used for the storage of gases such as hydrogen and carbon dioxide. 5),6) However, their pore size is still small. In contrast, several types of macroporous materials, such as inverse opal films, track-etched polycarbonate membranes, and porous anodic alumina membranes, have been reported thus far. However, such pore expansion seriously decreases surface area.Unlike other porous materials, mesoporous materials can be easily prepared under a wide range of synthetic conditions. Mesoporous materials exhibit several defined mesostructures, such as lamellar, two-dimensional (2D) hexagonal, three-dimensional (3D) hexagonal, and bicontinuous cubic mesostructures. Furthermore, many framework compositions (e.g., silica, organosilica, metal, and non-siliceous oxides) and various morphologies (e.g., nanoparticle, monolith, a...

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