Vol.11 no.3 2019

Research paper : Challenge towards synthesis of non-silica-based hybrid mesoporous materials (T. KIMURA)−123−Synthesiology - English edition Vol.11 No.3 (2018) structure”? Also, I understood that you set such a goal because, with silica-based materials, you can only do certain application development because they are hydrophobic, but you expect that the usage will expand if they can be made hydrophilic. Can you explain to which elds the usage can expand if you can make it hydrophilic compared to the silica usage shown in Fig. 1?Answer (Tatsuo Kimura)As you indicate, I started efforts on “designing the hydrophilic surface structure” for which there were hardly any reports, as my specic goal of “designing the pore environment.” Silica-based and all other mesoporous materials have hydrophobic pore environment, and the pore environment becomes even more hydrophobic in application development using organic groups. Therefore, as the first goal, I attempted to create hydrophilic nanospace directly opposite. Therefore, I assumed usages as catalyst carriers and adsorbents that are major uses of silica-based mesoporous materials as shown in Fig. 1. If I can achieve hydrophilic surfaces, I expect, for example, application development as a chemical reaction field to greatly increase reaction efciency of chemical substances including hydrophilic regions.5 Reactivity control of inorganic speciesQuestion (Toshimi Shimizu)Among elemental technologies, if you change from silica-based to non-silica-based, I think it would be very important what strategies and tactics are employed for (1) reactivity control of inorganic species. To control the reactivity of inorganic species, “a Si-O-Si bond is formed by inserting an organic cross-link region between the silica species, or a P-O-M bond is formed using the interaction of phosphonic acid and metal species by inserting the organic cross-link region between phosphonic acids. If the precursor of porous materials can be formed by self-assembly, the key will be how to extract the core parts (by solvent extraction, low temperature firing, dissolution extraction, etc.).” Is my understanding correct?Answer (Tatsuo Kimura)For the understanding of reactivity control of inorganic species, I shall add some explanation particularly to the part you indicated. In the final product, a starting material to which an organically bridged part has been inserted to create an inorganic-organic composite framework is used. However, this changes the reactivity of the raw material but does not directly lead to control.For example, in the case of silica, the initial reactivity of the material changes by whether chlorosilane (Si-Cl) is used or alkoxylsilane (Si-OR) is used. The formation speed of the Si-O-Si bond changes, not only by hydrolysis of initial reaction, but also by the pH at which the precursor solution is prepared. As the reaction progresses, the hydrophilic regions of the amphiphilic organic molecules and dissolved silicate species interact, a silicate framework is formed as further bond formation takes place as self-assembly progresses, and the precursor of mesoporous silica is obtained. If the reaction of silicate species goes too far, the charge density of the silicate framework decreases, the interacting amphiphilic organic molecules fall off, and only mesoporous silica precursors with lowered integrity of periodic structure are obtained.In non-silica-based oxides with higher reactivity, a precipitate consisting of only inorganic species is formed. Thus obtaining even the precursor of mesoporous materials becomes impossible. However, in the case of achieving mesoporosity of metal phosphates, phosphates are used as the phosphorus source in almost all cases, and the initial reactivity changes by whether chloride (M-Cl) or alkoxides (M-OR) are used as metal sources. In this case, when phosphates are coexisting at a certain ratio, the metal sources and phosphates react rst (P-O-M bond forms), and if the reaction is relatively slow, the following reaction will be relatively mild. In a case in which formation of a P-O-M bond is fast, as in the non-silica-base, it is necessary to inhibit the reactivity in solution, and measures must be taken to prepare an appropriate non-aqueous precursor solution.Considering the above, even in synthesis using phosphonate compounds instead of phosphates, as explained in the paper, the insertion of organically bridged regions must be done at the same time as the functional design (to realize inorganic-organic composites). Since electron density of phosphorus atoms changes according to the type of organic groups, the initial reactivity of the raw material changes. For the control, this research proposes a new method of controlling reactivity using a starting material in which the ester region (P-OR) and hydroxyl groups (P-OH) coexist in the same molecular structure.6 Final goalComment & Question (Motoyuki Akamatsu)In the rst paragraph of Chapter 3, you write “I set the nal goal or ‘point of achievement in synthesis research’ as opening the way to advanced material design,” but does this mean you set as your goal the development of universal synthesis technology? In the latter half of this paragraph, you write about the starting material, but is this the starting material that leads to universal synthesis technology? Also, is this the organically bridged phosphonates that you introduce in Subchapter 3.1? In Discussion 2, in relation to my question, the logical progression of this part is unclear, so please clarify.Answer (Tatsuo Kimura)As I wrote immediately after the part you indicated. in the research field of mesoporous materials, the significance of synthesis research of non-silica-based hybrid mesoporous material is opening the way to advanced materials design. As a result, if it is proven that the pore environment can be controlled arbitrarily, advanced application development can be started as the next research phase. There isn’t much meaning in doing usage tests to match the developed material. Therefore, I focus on synthesis research, and aim to provide a series of mesoporous materials with various pore environments. For logical progression, I added corrections in the indicated areas.

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