Silylation Efficiency of Chorosilanes, Alkoxysilanes, and Monosilazanes on Periodic Mesoporous Silica
Silylation Efficiency of Chorosilanes, Alkoxysilanes, and Monosilazanes on Periodic Mesoporous Silica
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DOI：
10.1021/jp107749g
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发表时间：
2010-12-30
影响因子：
3.7
通讯作者：
Anwander, Reiner
中科院分区：
文献类型：
--
作者：
Deschner, Thomas;Liang, Yucang;Anwander, Reiner
周期性介孔氧化硅（PMS）由于其大的比表面积和独特的孔结构，易于研究表面硅醇基团的反应性。涉及形成化学稳定的O-SiR 3部分的表面甲硅烷基化是氧化载体材料的强大且可能是最突出的合成后官能化方法。本研究将评估类似大小的二甲基辛基硅氮烷的反应性/硅烷化行为（Me 2NSiMe 2（C8 H17））、二甲基辛基氯硅烷（ClSiMe 2（C8 H17））和辛基三乙氧基硅烷（（EtO）（3）Si（C8 H17）），朝向周期性介孔二氧化硅MCM-41（BET表面积a（s）= 1060 m（2）/g，孔体积V-p = 1.14 cm（3）/g，孔径d（p）= 4.0 nm，硅烷醇数= 3.47 mmol/g）和SBA-1（a（s）= 1260 m（2）/g，V-p = 0.73 cm（3）/g，D-me = 4.5nm，硅烷醇群= 4.45mmol/g）。选择中等长度的脂肪族尾部（C-8）以确保可靠的元素（碳）分析并研究笼状SBA-1的任何尺寸选择性行为。对于通道状MCM-41，所获得的杂化材料显示出与氯硅烷和乙氧基硅烷相比单硅氮烷试剂的上级甲硅烷基化效率（SE）（SE = 81%对67%对22%，使用过量的甲硅烷基化试剂），后两种试剂需要升高的温度（125 ℃）或化学计量量的碱（NEt 3）。对于笼状SBA-1，观察到单硅氮烷试剂在外表面和孔开口处的位点特异性反应性，最终导致孔堵塞。即使在更苛刻的反应条件下，氯硅烷和乙氧基硅烷也产生更无规的表面甲硅烷基化，然而具有更低的SE值（SE = 76%对62%对32%;使用过量的甲硅烷基化试剂）。
Because of their large surface area and distinct pore architecture, periodic mesoporous silica (PMS) are predisposed to study the reactivity of surface silanol groups. Surface silylation involving the formation of thermodynamically stable O-SiR3 moieties is a powerful and probably the most prominent postsynthesis functionalization method of oxidic support materials. This study will assess the reactivity/silylation behavior of similarly sized dimethyloctylsilazane (Me2NSiMe2(C8H17)), dimethyloctylchlorosilane (ClSiMe2(C8H17)), and octyltriethoxysilane ((EtO)(3)Si(C8H17)), toward periodic mesoporous silica MCM-41 (BET surface a(s) = 1060 m(2)/g, pore volume V-p = 1.14 cm(3)/g, pore diameter d(p) = 4.0 nm, silanol population = 3.47 mmol/g) and SBA-1 (a(s) = 1260 m(2)/g, V-p = 0.73 cm(3)/g, D-me = 4.5 nm, silanol population = 4.45 mmol/g). A medium-long aliphatic tail (C-8) was chosen to ensure a reliable elemental (carbon) analysis and to study any size-selective behavior of cagelike SBA-1. For channel-like MCM-41, the obtained hybrid materials reveal a superior silylation efficiency (SE) of the monosilazane reagent compared to the chloro- and ethoxysilanes (SE = 81% versus 67% versus 22%, use of excess of silylating reagent), the latter two reagents requiring either elevated temperature (125 degrees C) or stoichiometric amounts of a base (NEt3). For cagelike SBA-1, site-specific reactivity of the monosilazane reagent at the outer surface and pore openings was observed, finally resulting in pore blockage. Even under harsher reaction conditions, the chloro- and ethoxysilanes gave a more random surface silylation, however with lower SE values (SE = 76% versus 62% versus 32%; use of excess of silylating reagent).