Aromatic PMOs: Tolyl, xylyl and dimethoxyphenyl groups integrated within the channel walls of hexagonal mesoporous silicas

There exists a need to synthesize PMOs with bridging organic groups beyond the few that are accessible from commercially available bis(triethoxysilyl)organic precursors. To fulfill this need, three new periodic mesoporous arylsilicas, aromatic PMOs, having bridging aromatic organic groups as an integral part of the framework have been synthesized and structurally characterized. The surfactant-templated synthesis employed new precursors consisting of two triethoxysilyl groups connected via toluene, p-xylene or 1,4-dimethoxybenzene. Diffraction and microscopy together with ¹³C CP-MAS NMR, ²⁹Si MAS NMR and FT-Raman/IR measurements proved that the aryl-silica bonds in the new precursors and aromatic PMOs are stable under hydrolytic polycondensation self-assembly and surfactant acid extraction conditions. These PMOs have an ordered hexagonal channel mesostructure, some degree of ordering of aromatic groups likely through π-π stacking in the channel walls, a large pore volume and surface area, and relatively thick arylsilica walls whose dimensions seem to scale with the spatial demands of the aryl group.