Ethylene‐bridged Periodic Mesoporous Organosilicas with Large Spherical Pores Templated by PEO‐PPO‐PEO Surfactant Micelles Swollen by Ethylbenzene

Abstract

AbstractThe applicability of a recently identified potent micelle swelling agent, ethylbenzene, was verified for periodic mesoporous organosilicas (PMOs) and its performance was found to be comparable to that of xylene, which was previously shown to be an excellent swelling agent for surfactant‐templated ordered mesoporous silica and organosilica synthesis. Large‐pore ethylene‐bridged PMOs with face‐centered cubic structures of spherical mesopores were synthesized using Pluronic F127 (EO106PO70EO106) surfactant and ethylbenzene or xylene swelling agents at temperatures from 15 down to 7 °C. In the case of ethylbenzene, PMOs were synthesized at 15 °C using two different amounts of the inorganic salt (KCl) and under salt‐free conditions. It was found that ethylbenzene and xylene perform comparably well, allowing one to synthesize highly ordered face‐centered cubic ethylene‐bridged PMOs with unit‐cell parameters ca. 40 nm and nominal pore diameters ca. 14 nm. It was also possible to convert PMO prepared in the presence of ethylbenzene to silica with nearly closed mesopores via calcinations at 400 °C under air. The dependence of the PMO structure on the initial synthesis temperature and the salt concentration was found to be highly similar for ethylbenzene and xylene. Because of the fact that xylene (dimethylbenzene) was found earlier to work differently from toluene (methylbenzene) and trimethylbenzene, the observed similarity between the performance of xylene and ethylbenzene confirms an expectation that the suitability of alkylbenzenes for PEO‐PPO‐PEO block‐copolymer‐templated synthesis of well‐defined porous materials depends primarily on the total number of carbon atoms in their alkyl substituents. This finding is expected to streamline the process of identifying effective swelling agents for PMOs and other mesoporous materials.