Kruk Michal, Celer Ewa B, Matos Jivaldo R, Pikus Stanisław, Jaroniec Mietek
Department of Chemistry, Kent State University, Kent, Ohio 44242, USA.
J Phys Chem B. 2005 Mar 10;109(9):3838-43. doi: 10.1021/jp0462308.
Ordered silicas with large (9-15 nm), uniform, cagelike mesopores were synthesized under acidic aqueous conditions from tetraethyl orthosilicate in the presence of sodium chloride using poly(ethylene oxide)-poly(butylene oxide)-poly(ethylene oxide) triblock copolymer B50-6600 (EO39BO47EO39, Dow Chemicals) as a supramolecular template. Except for the use of NaCl in our case, the synthesis mixture composition was the same as that originally reported by Zhao et al. for the synthesis of FDU-1 silica, which was later shown to exhibit a cubic close-packed (Fm3m) structure with stacking faults related to the occurrence of hexagonal close-packed stacking sequences. The copolymer-templated silicas were formed at room temperature and in most cases were subjected to the hydrothermal treatment at 373 or 393 K. The calcined materials were characterized using small-angle X-ray scattering (SAXS) and nitrogen and argon adsorption at 77 K. SAXS patterns were generally similar to those reported for FDU-1 silica, indicating the cubic close-packed (Fm3m) structure, but the presence of stacking faults characteristic of a hexagonal close-packed structure cannot be precluded. The addition of the salt was found to significantly narrow the pore size distributions and to improve the uniformity of entrances to the cagelike mesopores, whereas the pore diameter, specific surface area, and pore volume were similar (in most cases slightly lower) to those for FDU-1 silicas obtained in the absence of NaCl. The materials synthesized in the presence of NaCl also appeared to have better resolved SAXS patterns. The feasibility of tailoring the pore cage diameter (from approximately 9.5 to 14.5 nm) and pore entrance diameter (from below 4 to approximately 8 nm) simply by adjusting the hydrothermal treatment temperature and time was demonstrated, indicating that these simple and convenient ways of structural design of cagelike mesopores are operative in the case of syntheses in the presence of inorganic salts.
在酸性水条件下，以正硅酸四乙酯为原料，在氯化钠存在下，使用聚（环氧乙烷）-聚（丁烯氧化合物）-聚（环氧乙烷）三嵌段共聚物B50 - 6600（EO39BO47EO39，陶氏化学）作为超分子模板，合成了具有大尺寸（9 - 15纳米）、均匀、笼状介孔的有序二氧化硅。除了在我们的实验中使用氯化钠外，合成混合物的组成与赵等人最初报道的用于合成FDU - 1二氧化硅的组成相同，后来发现该二氧化硅呈现立方密堆积（Fm3m）结构，且存在与六方密堆积堆叠序列出现相关的堆垛层错。共聚物模板化的二氧化硅在室温下形成，并且在大多数情况下在373或393 K下进行水热处理。煅烧后的材料使用小角X射线散射（SAXS）以及在77 K下的氮气和氩气吸附进行表征。SAXS图谱通常与报道的FDU - 1二氧化硅的图谱相似，表明其具有立方密堆积（Fm3m）结构，但不能排除存在六方密堆积结构特有的堆垛层错。发现添加盐会显著缩小孔径分布并改善笼状介孔入口的均匀性，而孔径、比表面积和孔体积与在不存在氯化钠的情况下获得的FDU - 1二氧化硅的相似（大多数情况下略低）。在氯化钠存在下合成的材料似乎也具有分辨率更高的SAXS图谱。通过简单地调节水热处理温度和时间来定制笼状孔径（从约9.5到14.5纳米）和孔入口直径（从低于4到约8纳米）的可行性得到了证明，这表明这些简单方便的笼状介孔结构设计方法在无机盐存在的合成情况下是可行的。
