Large porephenylene-bridged mesoporous organosilica with bicontinuous cubic Iad (KIT-6) mesostructure

Abstract

Assembly of mesostructured silica using Pluronic P123 triblock copolymer (EO₂₀-PO₇₀-EO₂₀) and n-butanol is a facile synthesis route to the MCM-48-like ordered large mesoporous silicas with the cubic Iad mesostructure, which are designated KIT-6. This synthesis route has been successfully extended to phenylene-bridged organosilicas from the limit so far for silica, using 1,4-bis(triethoxysilyl)benzene as an organosilica source and re-optimizing the synthesis conditions. In particular, optimal acid concentration and reagent ratios were determined to allow facile synthesis of the bicontinuous cubic mesophase in high yield and high phase purity. The products were characterized by powder X-ray diffraction (XRD), transmission electron microscopy, solid state NMR spectroscopy and analysis of nitrogen sorption at −196 °C using modern non-local density functional theory methods. This synthesis procedure enabled easy fine tuning of pore volume, specific surface area and mesopore size by variation of the hydrothermal aging temperature between 80 and 130 °C. Furthermore, wide angle XRD data suggest short range molecular-scale periodicity in the framework walls originating from regular arrangement of the bridging aromatic groups. These KIT-6 organosilica materials with fully interconnected nanoporous structure would be readily available for applications in heterogeneous catalysis, selective adsorption, and nanostructure design via solid templating approaches.