Synthesis and Properties of 1,3,5-Benzene Periodic Mesoporous Organosilica (PMO):  Novel Aromatic PMO with Three Point Attachments and Unique Thermal Transformations

Abstract

A new aromatic periodic mesoporous organosilica material containing benzene functional groups that are symmetrically integrated with three silicon atoms in an organosilica mesoporous framework is reported. The material has a high surface area, well-ordered mesoporous structure and thermally stable framework aromatic groups. The functional aromatic moieties were observed to undergo sequential thermal transformation from a three to two and then to a one point attachment within the framework upon continuous thermolysis under air before eventually being converted to periodic mesoporous silica devoid of aromatic groups at high temperatures and longer pyrolysis times. The mesoporosity of the material was characterized by powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), and nitrogen porosimetry, whereas the presence and transformation of the aromatic groups in the walls of the materials were characterized by solid-state NMR spectroscopy, mass spectrometry, and thermogravimetric analysis. The attachment of a benzene ring symmetrically onto three siloxanes of the framework was used advantageously as a cross-linker to enhance the thermal stability of the organic group. Some of these properties are investigated in comparison with other aromatic PMOs that have only two point attachments and an amorphous phenylsilica gel that has only one point attachment. The successful synthesis of the first aromatic PMO with its organic group attached within the framework through more than two points is an important step toward the synthesis of PMOs having organic groups with more complex and multiple attachments within the framework.

Highly Ordered Mesoporous Organosilica Hybrid Materials

“…44 Kuroki et al presented the successful synthesis of periodic mesoporous materials made of threepoint attachments for the 1,3,5-tris(triethoxysilyl)benzene precursor. 45 The materials showed relatively small pore diameters (%2:2 nm). Later, Landskron et al summarized PMO synthesis from the cyclic precursor [1,3,5-tris(diethoxysilyl)cyclohexene], which leads to interconnected [Si(CH 2 )] 3 rings.…”

Advances in Microporous and Mesoporous Solids—Highlights of Recent Progress

“…5a). [45,46] Ozin and co-workers connected benzene rings within the mesopore framework through three anchoring points, using 1,3,5-tris(triethoxysilyl)benzene precursors and cationic alkyl surfactants. [45] Well-ordered hexagonal mesophases with high surface areas were obtained.…”

“…[45,46] Ozin and co-workers connected benzene rings within the mesopore framework through three anchoring points, using 1,3,5-tris(triethoxysilyl)benzene precursors and cationic alkyl surfactants. [45] Well-ordered hexagonal mesophases with high surface areas were obtained. The crosslinked products exhibited relatively high thermal stability and interesting thermal transformations during calcination in air, involving conversions of 3-connected benzenes to 2-connected and then 1-connected benzenes.…”

Large Pore‐Sized Hollow Mesoporous Organosilica for Redox‐Responsive Gene Delivery and Synergistic Cancer Chemotherapy

“…For instance, one of the three Si-C bonds in the periodic mesoporous organosilicas (PMOs) derived from 1,3,5-tris(triethoxysilyl)benzene could be cleaved at 350 °C, while the second Si-C bond could be broken up when heated to 450 °C, leaving a terminal phenyl group. [ 7 ] Here, we have successfully developed a facile and general stability difference-based selective bond breakage (SD-SBB) strategy for the fabrication of HMONs, which are featured with large pore size and organic-inorganic hybrid framework. This strategy is based on the chemical-bond stability difference within the framework where Si-C bond is signifi cantly weaker than Si-O bond, thus the selective breakdown of weaker Si-C bonds would result in the enlargement of pore size in the shell of HMONs.…”