Vol.11 no.3 2019
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Research paper : Challenge towards synthesis of non-silica-based hybrid mesoporous materials (T. KIMURA)−118−Synthesiology - English edition Vol.11 No.3 (2018) compounds such as xylene linkers. Moreover, I worked on increasing my skills to synthesize phosphonate esters in which the molecular structure was arbitrarily designed. Through such efforts, I achieved synthesis of mesoporous lms from organically bridged phosphonate compounds in which amino groups (-NH2) or sulfonic acid groups (-SO3H) were added to the bridged benzene ring. Figure 5 is a summary of compounds that were introduced as bridged organic groups. Not only simple organic groups, but also various aromatic compounds that could be functionally designed were introduced. This indicates that composition design technology has advanced to the level in which application research could be conducted as in silica. Therefore, the design of a “hydrophilic surface structure” and “survey of its specicity” for the “design of the pore environment” that are primary research strategies of this research have been mostly realized.3.4 Diversification of inorganic composition: From aluminum to transition metalsUp to this point, the synthesis research that centered on aluminum as metal species was described. As the next step, I worked on the synthesis with metal species other than aluminum and started preliminary experiment for “controlling the pore environment.” If diversification of inorganic species could be realized, it would be possible to use properties of inorganic unit surfaces that is traceable to the types of inorganic species. For example, in aluminum, since H2O molecules can be coordinated until tetracoordinate aluminum species (AlO4) become 6-coordinate species (AlO6) as a property of an aluminophosphonate-like inorganic unit, the surface behaves in a hydrophilic manner. Therefore, if synthesis could be done by other metal species, changes will be seen in the H2O adsorption behavior since those metal species would not become tetracoordinates.Here, as the simplest example, the result is shown for synthesizing a mesoporous film of metal phosphonates from phosphonate compounds in which methylene bridged phosphonate esters are partially acid treated. It was confirmed that a mesoporous film could be obtained when titanium chloride (TiCl4) was used as the inorganic material, as well as vanadium chloride (VCl3) that does not have high reactivity. However, since TiCl4 has extremely high reactivity, the precursor solution was prepared using non-aqueous solution (ethanol). It is thought difcult to form a framework (formation of M-O-P bond) from metal species (M) that is present as ion species in solution. If the metal species (M) is capable of covalent bonding through phosphorus (P) and oxygen (O) atoms, I believe a mesoporous material with a new composition can be designed by understanding and controlling the reactivity of those metal species in solution.4 Process design assuming practical application using mesoporous materialIn this paper, the major elemental technologies for synthesis research of mesoporous materials are categorized from (1) to (6). For example, as shown in Fig. 5, it was explained that I was able to synthesize a hybrid mesoporous material using non-silica as a result of integrating (1) to (5). I present my conclusion by providing a discussion of the final elemental technology “(6) Process design assuming application development.” Normally, materials development starts from fulfilling the demand for high performance against “social demand (application development)” as shown in Fig. 7 (top). If it is a replacement of an existing material (improvement research), the usage is already predetermined. Therefore, if high performance can be achieved through a similar synthesis system, the level of performance improvement that can be achieved is confirmed. If there are no issues about the cost of raw materials or manufacturing processes, it PPOOAlOHOOAlOHPPOHOC2H5OOH5C2OHOPPOHO─M─OO─M─OHO※Restriction to form high-molecular-weight precursor in solution※Combination with thetechnology to fabricate porous structure※Introduction of aromaticcompound in non-silica-based(metal phosphate-like) framework※Hydrophilic surface provided onlyby aluminophosphate frameworkamong mesoporous materialsExample of organically bridged phosphonate compound where acid and ester coexist in the molecular structureMetal source (e.g. chlorides)【Formation of metal (M)‒oxygen‒phosphorus bond】20 nmB acid siteL acid site※Molecular design considering the reactivity with metal source【High reactivity】Fig. 6 Reaction of benzene bridged phosphonate compound and metal source, which combined with the technology to fabricate mesoporous structure

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