School of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240, P.R. China.
School of Chemical Science and Engineering, Tongji University, 1239 Siping Road, Shanghai, 200092, P.R. China.
Chemistry. 2019 Jan 14;25(3):738-742. doi: 10.1002/chem.201804841. Epub 2018 Dec 11.
Designing a templating strategy for directing mesopore growth along different crystallographic directions is essential for fabricating two- or three-dimensional single-crystalline mesoporous zeolites. However, so far, mesopores formed in MFI zeolites by soft templates have mostly been generated by disrupting growth along the b axis; generating mesopores by disrupting growth along the a axis is rare. Herein, a single-crystalline mesoporous MFI zeolite (SCMMZ) with sheet-like mesopores layered along the a and b axes was synthesized using a triply branched surfactant with diquaternary ammonium groups connected to 1,3,5-triphenylbenzene by a six- and eight-carbon alkyl chain (TPB-6 and 8). The sheet-like mesopores were embedded in the MFI framework and were retained even after calcination. Molecular mechanics calculations provided evidence of low binding energy configurations of the surfactant that directed the growth of straight and zigzag channels along the b and a axes, respectively. The formation of nanosheets was attributed to the geometric matching of the arrangement of the aromatic groups to the zeolite framework.
设计沿不同晶向引导介孔生长的模板策略对于制备二维或三维单晶介孔沸石至关重要。然而，迄今为止，由软模板在 MFI 沸石中形成的介孔主要是通过破坏沿 b 轴的生长来产生的；通过破坏沿 a 轴的生长来产生介孔的情况很少见。在此，使用具有连接到 1,3,5-三苯基苯的二季铵基团的三分支表面活性剂（通过六和八碳烷基链连接的 TPB-6 和 8）合成了具有沿 a 和 b 轴层叠的片状介孔的单晶介孔 MFI 沸石（SCMMZ）。片状介孔嵌入在 MFI 骨架中，甚至在煅烧后仍保留。分子力学计算提供了证据，证明表面活性剂的低结合能构型分别指导了沿 b 和 a 轴的直通道和锯齿形通道的生长。纳米片的形成归因于芳族基团的排列与沸石骨架的几何匹配。
