Ethenylene-bridged periodic mesoporous organosilicas with ultra-large mesopores

Abstract

E-configured ethenylene-bridged periodic mesoporous organosilicas with ultra-large mesopores and unprecedented pore volumes have been developed for the first time.Periodic mesoporous organosilicas (PMOs) are a relatively novel group of organic-inorganic hybrid materials in which the organic groups are not located in the pores, but rather are an intrinsic part of the pore walls. 1 They are prepared via the direct condensation of bridged organosilanes, most commonly of the type (RO) 3 Si-R 0 -Si(OR) 3 , in the presence of a structure directing agent. This way nanocomposites with a high organic content can be obtained while preserving the pore ordering and uniformity. Ethenylene-bridged PMOs are especially interesting as they are easily modified by means of olefin chemistry. 2 Due to their structural rigidity and controllable hydrophobic character, PMOs are of great interest for applications in catalysis, 3 environmental technology 4,5 and chromatography. 6 However, the applicability of PMOs is often limited by their pore sizes, which typically range between 2 and 8 nm. In some applications, such as in biocatalysis or controlled drug release, larger mesopores are required to allow the diffusion, adsorption or immobilization of large biomolecules such as enzymes, proteins or drugs. To date, the synthesis of ethenylene-bridged PMOs with mesopores larger than 15 nm has not been reported, so with this goal in mind, we probed the possibility of adapting pluronic P123 as a template, in combination with 1,3,5-trimethylbenzene (TMB) as a sweller.Recently we reported a novel synthesis of diastereoisomeric, hexagonally ordered ethenylene-bridged PMOs. 7,8 Here we report on a new and easy method to develop ultra-large pore isomeric PMOs with unprecedented pore volumes consisting of various pore systems, including foam-like pore structures with uniformly sized mesopores, 3D stacked spherical pores and nodular strings, i.e. cylinders built from linearly connected spheres. In a typical synthesis, 1.0 g of P123 was diluted in a solution containing 48.7 ml of H 2 O, 1.2 ml of n-butanol and 2.1 ml of concentrated HCl. The mixture was stirred at room temperature until P123 was fully dissolved, after which a varying amount of TMB was added. This solution was stirred for 0.5 h, after which 1.86 ml of the homemade E-1,2-bis-(triethoxysilyl)ethene was added. 7 Finally, the mixture was stirred for 3 h at 35 1C and aged for 24 h in an autoclave at 100 1C. The PMO was filtrated and the template removed by means of extraction with acetone. Following this procedure a series of 4 PMOs were synthesized by varying the amount of TMB, while keeping all other parameters constant. The results are given in Table 1.By varying the amount of TMB, the pore size can be engineered from approximately 8.1 to 28.3 nm. Moreover, by increasing the amount of TMB, PMOs with extremely high pore volumes can be attained. When employing 7.76 mmol of TMB, a PMO with a pore diameter of 28.3 nm and a total pore volume of 2.25 cm 3 g À1 was acquired, which, to the best ...

Ethenylene-Bridged Periodic Mesoporous Organosilicas: From E to Z

“…Doing so, they open up a wide range of new opportunities in designing materials with novel organic functionalities and controlled morphological, structural, and surface properties. To date, PMOs with various rigid organic functionalities have been synthesized, ranging from short aliphatic and aromatic groups such as methane, 21 ethane, 22 ethene, 3,[23][24][25][26][27] benzene, [28][29][30] and xylene 31 to cyclic 32 *Corresponding author. E-mail: carl.vercaemst@ugent.be (C.V.); pascal.…”

Periodic Mesoporous Organosilicas from Polyion Complex Micelles – Effect of Organic Bridge on Nanostructure

“…● BTSEENE has a semi‐rigid organic bridging system, which still plays a nanostructuring role;, while…”

“…This approach offers the possibility of having the organic functions distributed uniformly within the walls of the pores and, in addition, facilitates the design of multifunctional hybrid materials such as PMO nanoparticles which can be used in catalysis, adsorption, drug delivery, sensing, etc . Although the development, characterization and uses of PMOs have been reviewed by several authors, many additional applications can be anticipated, based on the possibility of mixing and localizing the functionalities in the pores or in the walls, controlling the proximities of multiple organic functions,, improving the wall crystallinity, as well as controlling the pore size and the wall thickness of the resulting materials. However, a limitation of traditional surfactant‐based soft templates is the relatively small size of the pores that are typically obtained, which limits the potential applications of the resulting PMOs.…”

Periodic Mesoporous Organosilicas: from simple to complex bridges; a comprehensive overview of functions, morphologies and applications

“…110 Also the pore diameters of ethene-, methane-and benzenePMOs have been enlarged. 110 Van Der Voort et al 111 were able to engineer the pore size of ethenylene-bridged PMO materials in the range of 8.1 to 28.3 nm. A methylene-PMO with face-centered cubic structure (Fm % 3m) was synthesized by using F127 as template 112 under conditions similar to those reported for ethylene-bridged PMOs 107 but using a different precursor (BTEM)/surfactant ratio.…”