Oka Yuya, Kuroda Yoshiyuki, Matsuno Takamichi, Kamata Keigo, Wada Hiroaki, Shimojima Atsushi, Kuroda Kazuyuki
Department of Applied Chemistry, Faculty of Science and Engineering, Waseda University, Okubo 3-4-1, Shinjuku-ku, Tokyo, 169-8555, Japan.
Waseda Institute for Advanced Study, Waseda University, 1-6-1 Nishiwaseda, Shinjuku-ku, Tokyo, 169-8050, Japan.
Chemistry. 2017 Jul 12;23(39):9362-9368. doi: 10.1002/chem.201701282. Epub 2017 Jun 22.
Mesoporous basic Mg-Al mixed metal oxides (MMOs) with a high surface area and large pore size have been prepared through the assembly of monodispersed layered double hydroxide nanoparticles (LDHNPs) with block copolymer templates. The particle sizes of the LDHNPs were mainly controlled by varying the concentration of tris(hydroxymethyl)aminomethane (THAM), which was used as a surface stabilizing agent. LDHNPs and micelles of a block copolymer (Pluronic F127) were assembled to form a composite. The composites were calcined to transform them into mesoporous MMOs and to remove the templates. The Brunauer-Emmett-Teller surface areas, mesopore sizes, and pore volumes increased as a result of using the templates. Moreover, the pore sizes of the mesoporous MMOs could be controlled by using LDHNPs of different sizes. The mesoporous MMOs prepared from the LDHNPs showed much higher catalytic activity than a conventional MMO catalyst for the Knövenagel condensation of ethyl cyanoacetate with benzaldehyde. The mesoporous MMO catalyst prepared using the smallest LDHNPs, about 12 nm in size, showed the highest activity. Therefore, the use of monodispersed LDHNPs and templates is effective for preparing highly active mesoporous solid base catalysts.
通过将单分散层状双氢氧化物纳米颗粒（LDHNPs）与嵌段共聚物模板组装，制备出了具有高比表面积和大孔径的介孔碱性镁铝混合金属氧化物（MMOs）。LDHNPs的粒径主要通过改变用作表面稳定剂的三（羟甲基）氨基甲烷（THAM）的浓度来控制。将LDHNPs与嵌段共聚物（Pluronic F127）的胶束组装形成复合材料。对复合材料进行煅烧，将其转化为介孔MMOs并去除模板。由于使用了模板，布鲁诺尔-埃米特-泰勒比表面积、介孔尺寸和孔体积都增加了。此外，介孔MMOs的孔径可以通过使用不同尺寸的LDHNPs来控制。由LDHNPs制备的介孔MMOs在氰基乙酸乙酯与苯甲醛的克诺文纳格尔缩合反应中表现出比传统MMO催化剂高得多的催化活性。使用尺寸约为12 nm的最小LDHNPs制备的介孔MMO催化剂表现出最高的活性。因此，使用单分散的LDHNPs和模板对于制备高活性介孔固体碱催化剂是有效的。
