Synthesis of amino-functionalized MCM-41 via direct co-condensation and post-synthesis grafting methods using mono-, di- and tri-amino-organoalkoxysilanes
Synthesis of amino-functionalized MCM-41 via direct co-condensation and post-synthesis grafting methods using mono-, di- and tri-amino-organoalkoxysilanes
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DOI：
10.1039/b310576h
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发表时间：
2004-01-01
影响因子：
--
通讯作者：
Tatsumi, T
中科院分区：
文献类型：
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作者：
Yokoi, T;Yoshitake, H;Tatsumi, T
以3-氨基丙基三甲氧基硅烷（N硅烷）、[1-（2-氨基乙基）-3-氨基丙基]三甲氧基硅烷（NN硅烷）或1-[3-（三甲氧基硅基）丙基]二乙烯三胺（NNN硅烷）与正硅酸四乙酯共缩合制备了氨基功能化介孔材料MCM-41。N、NN和NNN硅烷在硅源中的最大比例分别为0.5、0.4和0.4。所得材料的Si-29 MAS NMR测量结果表明，含Si- c键的Si原子分别占总硅的26.0%、17.0%和7.8 Si摩尔%。通过对表面活性剂提取样品的元素分析和银量滴定结果的比较，发现所有被掺入的氨基酸片段都不存在于表面，但其中一些氨基酸片段存在于六边形通道的壁上。通过在脱水的MCM-41上接枝，合成了氨基功能化的MCM-41样品。在N、NN和NNN硅烷的最大硅化水平下，含有Si- c键的Si原子分别约为20.6、19.2和17.9 Si mol%，这表明在MCM-41表面上，锚定在硅醇基上的氨基有机烷氧基硅烷的表面覆盖率几乎是相同的，与氨基有机烷氧基硅烷的大小无关。为了比较研究两种方法引入的Co2+和Fe3+的活性和氨基有机基团的位置，我们进行了吸附实验，发现N、NN和NNN硅烷衍生的氨基基团的活性存在一些差异。无论氨基有机烷氧基硅烷是否存在，通过共缩合方法吸附在氨基功能化样品上的阳离子随着氨基表面密度的增加而增加。当N和NN硅烷接枝到MCM-41表面时，吸附量随着表面氨基密度的增加而增加。然而，当NNN硅烷固定在表面时，吸附容量随着氨基表面密度的增加而降低。这些结果表明，通过直接共缩合和合成后接枝方法引入到二氧化硅上的氨基的位置明显不同。
Amino-functionalized mesoporous MCM-41 materials were synthesized directly by co-condensation of 3-aminopropyltrimethoxysilane (N silane), [1-(2-aminoethyl)-3-aminopropyl] trimethoxysilane (NN silane) or 1-[3-(trimethoxysilyl) propyl] diethylenetriamine (NNN silane) with tetraethyl orthosilicate. The maximum proportions of N, NN and NNN silanes in the Si sources for obtaining the hexagonally structured functionalized silica were 0.5, 0.4 and 0.4, respectively. The Si-29 MAS NMR measurements of the materials thus obtained indicate that the Si atoms containing Si-C bonds accounted for 26.0, 17.0 and 7.8 Si mol% of the total silicons, respectively. By comparing with the results from the elemental analyses and the argentometric titrations of the surfactant-extracted samples, it was revealed that all the amino moieties incorporated were not present on the surface, but some of them were in the wall of the hexagonal channels. Amino-functionalized MCM-41 samples were also synthesized via a post-synthesis grafting on dehydrated MCM-41. At the maximum level of silylation with N, NN and NNN silanes, Si atoms containing Si-C bonds of about 20.6, 19.2 and 17.9 Si mol%, respectively, were obtained, indicating that the surface coverage of amino-organoalkoxysilanes anchored to silanol groups on the surface of MCM-41 were almost the same, irrespective of the size of the amino-organoalkoxysilanes. The adsorption experiments of Co2+ and Fe3+ were conducted in order to comparatively investigate the activity and the location of the amino-organic moieties introduced via the two methods, and some differences in the activity of amino groups derived from N, NN and NNN silanes were found. The cations adsorbed on the amino-functionalized samples via the co-condensation method were increased with an increase in the surface density of amino groups regardless of the amino-organoalkoxysilanes. When N and NN silanes were grafted onto the surface of MCM-41, the adsorption capacity was increased with an increase in the surface density of amino groups. However, when NNN silane was anchored to the surface, the adsorption capacity was decreased with an increase in the surface density of the amino groups. These results imply that the locations of the amino groups introduced to the silica via the direct co-condensation and the post-synthesis grafting methods are clearly different.