Periodic mesoporous organosilicas (PMOs) are obtained by the hydrolysis-condensation of organobridged triethoxysilane precursors in the presence of surfactants as structure-directing agents (SDAs). After removal of the SDAs, the resulting materials usually exhibit monomodal, well-organized mesoporosity, with the size of the pores being controlled by the SDA. However, despite the potential technological applications of such materials with well-organized bimodal porosity, to the best of our knowledge, PMOs exhibiting two distinct types of ordered mesoporosity have barely been described.

Herein, we describe a simple approach for modulating the dimensions of ordered monomodal 2D hexagonal and bimodal porosity in PMOs synthesized from 1,4-bis(triethoxysilyl)benzene (BTEB) and Pluronic P123 under acidic conditions, by varying the addition sequence of reactants. The approach employs a single SDA without degradation of the BTEB precursor. Reaction conditions leading to the formation of monomodal and bimodal porosity within the templated PMOs are identified. Our approach exploits the competition between the rates of (a) BTEB hydrolysis/condensation; and (b) diffusion, solubilization and partitioning of the unhydrolyzed and hydrolyzed precursor within the micelles. A mechanism describing the evolution of porosity within this system is proposed.

周期性的介孔有机二氧化硅（PMO）是在表面活性剂作为结构导向剂（SDA）的存在下，通过有机桥联的三乙氧基硅烷前体的水解缩合而获得的。除去SDA后，所得材料通常表现出单峰的，组织良好的介孔性，孔的大小由SDA控制。然而，尽管这种材料具有组织良好的双峰孔隙度的潜在技术应用，据我们所知，几乎没有描述具有两种不同类型的有序介孔率的PMO。

在这里，我们描述了一种简单的方法，通过改变反应物的添加顺序，可以调节由1,4-双（三乙氧基甲硅烷基）苯（BTEB）和Pluronic P123合成的PMO中有序单峰2D六角形和双峰孔隙度的大小。该方法采用单个SDA，而不会降解BTEB前体。确定了导致在模板化PMO中形成单峰和双峰孔隙的反应条件。我们的方法利用了（a）BTEB水解/冷凝速率之间的竞争；（b）未水解的和水解的前体在胶束内的扩散，增溶和分配。提出了描述该系统内孔隙度演化的机制。