Molecular Design of Bisphosphonates To Adjust Their Reactivity toward Metal Sources for the Surfactant‐Assisted Synthesis of Mesoporous Films

Abstract

The precise control of primary reactions in solutions is one of the most significant steps for the nanoscale design of inorganic solids in multidisciplinary fields.H owever,f urther growth of the inorganic species to give bulkier species disturbs such designs.T he surfactant-assisted synthesis of mesoporous materials is ag ood strategy for addressing such concerns because pores formed by supramolecularly mediated processes are surrounded by nanometer-sized continuous frameworks. Many experiments are generally conducted to optimizet he reaction conditions for the synthesis of highly ordered mesostructures.H erein, to minimize such trial-and-error efforts,anew and practical concept is proposed for the precise design of porous materials.Byadjusting the reactivity between bisphosphonates and metal sources through molecular design of the starting bisphosphonate compound, it was possible to synthesize mesoporous films with unique compositions by asurfactant-assisted approach.Ingeneral, MO x frameworks are continuously grown from metal sources (e.g.,salt and alkoxide) in aqueous solutions on the basis of sol-gel chemistry; [1,2] theformation rate of MÀOÀ Mbonds strongly depends on the kind of metal source as well as the reaction conditions (e.g., pH value of the solution). Actually,the reactivity (hydrolysis and subsequent condensation) of metal alkoxides in the presence of water can be decreased by changing the organic group in their alkoxy moiety (ÀOR) to ab ulkier group (R:m ethyl > ethyl > n-propyl > isopropyl > …). Additional control of the reactivity has been possible by utilizing the strong interaction with organic groups such as acetic acid, acetylacetone,a nd catechol [3][4][5] as well as by the use of non-aqueous systems. [6][7][8] Besides,i np rocesses for the synthesis of metal-phosphatebased materials,t he formation of M À O À Mb onds is remarkably suppressed by the presence of phosphate anions in the range of appropriate M/P molar ratios, [9,10] thus affording MÀ OÀPb onds homogeneously throughout the entire resultant solids without the formation of M À O À Mb onds.I nf act, we reported the delayed formation of M À O À Mb onds in the presence of anonreactive phosphite,P(OH) 3 ,asconfirmed in the titania system. [11] Avariety of mesoporous metal phosphonates have been reported so far; [12][13][14][15] however, many experiments were required for each composition of metal-phosphate-like inorganic units and organic groups for the fabrication of ordered mesostructures.T hus,t heir facile design in terms of their inorganic composition and the molecular functionality of organic groups attached to the Patom has not been achieved adequately to enable investigation of the extraordinary nature of this new family of mesoporous metal phosphonates containing organic spacers in the hybrid framework. In this study,t he molecular structure of bisphosphonates was designed to adjust their reactivity to metal sources,t hus enabling the successful fabrication of several mesoporous metal bisphosphonate films decorated with arom...

Challenge towards synthesis of non-silica-based hybrid mesoporous materials

“…As a result I succeeded in obtaining a mesoporous film with extremely high structural order. [22] The result of TEM observation is shown in Fig. 6.…”

“…[15]- [19] On the other hand, formation of films was the main theme of research for phosphonate compounds bridged with various aromatic compounds that were recently successfully developed. [22] Fortunately, powder Fig. 7 Basic guideline for the materials design to develop applications synthesis of mesoporous aluminum phosphonates was researched using a spray-drying process that is known as a synthesis method including a solvent evaporation process similar to film synthesis, [23] [24] and the understanding of this process was advanced.…”