{"title":"Simple Molecular Synthetic Approach to Dinuclear Titanium Sites in Ti-Containing Silica-Based Catalysts","authors":"Takuya Hikino, Yuka Kawakubo, Takamichi Matsuno, Seiji Yamazoe, Kazuyuki Kuroda, Atsushi Shimojima","doi":"10.1021/acs.chemmater.4c01454","DOIUrl":null,"url":null,"abstract":"Ti-containing silica-based catalysts are widely used for various organic oxidation reactions. Recently, increasing attention has been paid to the catalytic role of dinuclear (SiO)<sub>3</sub>Ti–O–Ti(OSi)<sub>3</sub> sites in titanosilicate zeolite TS-1. A promising experimental approach for elucidating the active sites is to use model compounds with dinuclear Ti sites. In this study, we report the synthesis and catalytic properties of a μ-oxo-bridged dinuclear titanosiloxane compound with a (SiO)<sub>3</sub>Ti–O–Ti(OSi)<sub>3</sub> site. A Ti-containing cage siloxane compound (<sup><i>i</i></sup>Bu<sub>7</sub>Si<sub>7</sub>O<sub>12</sub>)TiO<sup><i>i</i></sup>Pr (mononuclear Ti-polyhedral oligomeric silsesquioxane (POSS)) is prepared by the reaction of incompletely condensed POSS with titanium tetraisopropoxide. Then, it is converted to the dinuclear species (<sup><i>i</i></sup>Bu<sub>7</sub>Si<sub>7</sub>O<sub>12</sub>)<sub>2</sub>Ti<sub>2</sub>(μ-O) (dinuclear Ti-POSS) by the simple hydrolytic condensation of the TiO<sup><i>i</i></sup>Pr groups. The addition of H<sub>2</sub>O<sub>2</sub> to dinuclear Ti-POSS leads to the formation of a bishydroperoxo complex, as revealed by Ti K-edge X-ray absorption fine structure analysis. Dinuclear Ti-POSS possesses high catalytic activity in the cyclohexene epoxidation reaction, indicating that the (SiO)<sub>3</sub>Ti–O–Ti(OSi)<sub>3</sub> sites can function as efficient catalytically active sites. These findings contribute to the comprehension of the catalytic properties exhibited by dinuclear titanium sites within titanosilicate zeolite catalysts.","PeriodicalId":33,"journal":{"name":"Chemistry of Materials","volume":null,"pages":null},"PeriodicalIF":7.2000,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Chemistry of Materials","FirstCategoryId":"88","ListUrlMain":"https://doi.org/10.1021/acs.chemmater.4c01454","RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"CHEMISTRY, PHYSICAL","Score":null,"Total":0}
引用次数: 0
Abstract
Ti-containing silica-based catalysts are widely used for various organic oxidation reactions. Recently, increasing attention has been paid to the catalytic role of dinuclear (SiO)3Ti–O–Ti(OSi)3 sites in titanosilicate zeolite TS-1. A promising experimental approach for elucidating the active sites is to use model compounds with dinuclear Ti sites. In this study, we report the synthesis and catalytic properties of a μ-oxo-bridged dinuclear titanosiloxane compound with a (SiO)3Ti–O–Ti(OSi)3 site. A Ti-containing cage siloxane compound (iBu7Si7O12)TiOiPr (mononuclear Ti-polyhedral oligomeric silsesquioxane (POSS)) is prepared by the reaction of incompletely condensed POSS with titanium tetraisopropoxide. Then, it is converted to the dinuclear species (iBu7Si7O12)2Ti2(μ-O) (dinuclear Ti-POSS) by the simple hydrolytic condensation of the TiOiPr groups. The addition of H2O2 to dinuclear Ti-POSS leads to the formation of a bishydroperoxo complex, as revealed by Ti K-edge X-ray absorption fine structure analysis. Dinuclear Ti-POSS possesses high catalytic activity in the cyclohexene epoxidation reaction, indicating that the (SiO)3Ti–O–Ti(OSi)3 sites can function as efficient catalytically active sites. These findings contribute to the comprehension of the catalytic properties exhibited by dinuclear titanium sites within titanosilicate zeolite catalysts.
期刊介绍:
The journal Chemistry of Materials focuses on publishing original research at the intersection of materials science and chemistry. The studies published in the journal involve chemistry as a prominent component and explore topics such as the design, synthesis, characterization, processing, understanding, and application of functional or potentially functional materials. The journal covers various areas of interest, including inorganic and organic solid-state chemistry, nanomaterials, biomaterials, thin films and polymers, and composite/hybrid materials. The journal particularly seeks papers that highlight the creation or development of innovative materials with novel optical, electrical, magnetic, catalytic, or mechanical properties. It is essential that manuscripts on these topics have a primary focus on the chemistry of materials and represent a significant advancement compared to prior research. Before external reviews are sought, submitted manuscripts undergo a review process by a minimum of two editors to ensure their appropriateness for the journal and the presence of sufficient evidence of a significant advance that will be of broad interest to the materials chemistry community.