Comparative studies of grafting and direct syntheses of inorganic-organic hybrid mesoporous materials
Comparative studies of grafting and direct syntheses of inorganic-organic hybrid mesoporous materials
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DOI：
10.1021/cm990369r
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发表时间：
1999-11-01
影响因子：
8.6
通讯作者：
Stein, A
中科院分区：
文献类型：
--
作者：
Lim, MH;Stein, A
乙烯基官能化的MCM-41样品是通过合成后接枝(PSG)工艺或直接共缩合合成方法制备的。比较了两种方法合成的产物的结构、稳定性和反应活性。乙烯基接枝MCM-41(v-GR-MCM-41)的六方孔结构的介观有序与MCM-41的介观有序相似。粉末X-射线衍射仪、X-射线光电子能谱和溴化动力学数据表明，采用本工艺制备的v-GR-MCM-41中，乙烯基团呈不均匀分布，大部分乙烯基团分布在微晶外表面或孔道内，但靠近孔道开口处。直接合成产物(v-MCM-41)的介观顺序取决于所使用的烷氧基硅烷前体的类型以及反应混合物中乙烯基硅氧烷与烷氧基硅烷的比例。在v-MCM-41中，乙烯基团似乎分布更均匀。与未经改性的MCM-41相比，乙烯基接枝的MCM-41表现出更好的水热稳定性，并且能够从水混合物或乳液中吸收非极性溶剂。
Vinyl-functionalized MCM-41 samples were prepared by either a postsynthesis grafting (PSG) process or a direct, co-condensation synthesis. The structures, stabilities, and reactivities of products from both methods were compared. The mesoscopic order of the hexagonal pore structure of vinyl-grafted MCM-41 (v-gr-MCM-41) resembled that of the MCM-41 host. On the basis of powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), and bromination kinetics data, the vinyl groups appeared to be nonuniformly distributed in v-gr-MCM-41 prepared by the present PSG process, with a large proportion of vinyl groups on the external surface of the crystallites or inside channels but near the channel openings. The mesoscopic order of products from the direct synthesis (v-MCM-41) depended on the type of alkoxysilane precursor used and on the ratio of vinylsiloxane to alkoxysilane in the reaction mixture. The vinyl groups appeared to be more uniformly distributed in v-MCM-41. Vinyl-grafted MCM-41 exhibited greater hydrothermal stability than unmodified MCM-41 and was capable of absorbing nonpolar solvents from aqueous mixtures or emulsions.