双模板法制备介孔/大孔复合孔结构硅胶独石

Double-Templating Synthesis of Hierarchical Meso-macroporous Silica Monolith

采用双模板法，向正硅酸甲酯的水解体系中同时引入聚乙二醇和三嵌段共聚物，成功制备出具有双连续大孔、同时孔壁中分布着有序介孔的复合孔结构硅胶独石材料。产物的比表面积高达880m^2／g，大孔孔径为0．2～5μm，介孔高度集中地分布在5nm。结合物理吸附、扫描电镜、粉末X射线衍射和透射电镜等表征手段，发现合成条件如原料组成、反应温度和pH值等对反应体系中凝胶化转变和相分离发生的相对速度有重要影响，进而影响产物复合孔结构的生成。此外，通过对合成条件的优化，一方面增强了无机骨架的强度，另一方面降低了湿凝胶干燥过程中的毛细管压力降，有效缓和了凝胶结构在干燥过程中的开裂和变形，使复合孔结构硅胶独石在厘米尺度内具有良好的整体性能。

Hierarchical meso-macroporous materials have attracted much attention due to their potential applications in catalysis, sorption, and separation. The incorporation of interconnected macropores in mesoporous materials is very useful because macropores can favor mass transfer and reduce transport limitations. However, it still remains a challenge to fabricate ordered rnesoporous channels in the bicontinuous macroporous framework walls. This paper reports a double-templating route based on a sol-gel method to prepare hierarchical meso-macroporous silica monoliths. The obtained material shows a bicontinuous macroporous structure with highly ordered mesochannels distributing inside the macroporous skeleton walls. The bimodal pore structure was formed under the action of the two templates. The organic polymer was added to induce a phase separation taking place at the solgel transition and thus form the bicontinuous macroporous structure. Meanwhile, a nonionic surfactant was in-troduced to template the formation of ordered mesostrueture inside the macroporous skeleton walls. As characterization by scanning electron microscopy, transmittance electron microscopy, N2 physisorption, and X-ray diffraction, the resulting silica monolith exhibits specific surface area as high as 880 m^2/g and pore volume as large as 1.2 cm^3/g. The hexagonally ordered mesopores are highly centered at 5.8 nm. Besides, through optimizing the synthesis procedure, the monolith morphology of the resulting materials can be perfectly preserved during the wet gel drying process, and thus a crack-free hierarchical silica monolith with centimeter scale can be obtained.