Rapid synthesis of mesoporous silica by an accelerated microwave radiation method

Microwave-hydrothermal processes for the synthesis of mesoporous silica were investigated with different pathways and mixture conditions at 373 K, and the corresponding structures to the hydrothermal method were synthesized within a very short crystallization time. 2-D hexagonally ordered arrays of MCM-41 materials via the direct electrostatic assembly pathway of S+I- and mediated templating pathways of S+X-I+ with CTAB were synthesized, and cubic mesophase of MCM-48 was also prepared within 2 hrs of microwave heating without adding alcohol. Nonionic surfactants with ethylene oxide (EO) moiety as structure-directing agents were used for the preparation of ordered array of hexagonal or cubic mesostructured silica via the charge matching principle of ((SH+)-H-0)(X-I+). Although the detailed roles of microwaves may differ for each process, microwaves accelerate the formation of multiply charged silicate oligomers, initiating mesophase assembly. Therefore, the use of microwave radiation can transfer energy uniformly and quickly, and complete the syntheses of mesostructured materials within a short time.