Synthesis and application of mesoporous silica

Mesoporous materials with well-defined pore size and structure have applications in a wide range of topics from catalysis, environment and medicine to electronics. This work presents the methods and procedures for preparing functional mesoporous materials for applications in the environment from removal of toxic metals to clean synthesis of fine chemicals. Magnetic mesoporous silica (magMCM-41) of large surface area (800 m2 g-1) and high magnetization (8.30 emu g-1) was prepared by grafting 10 nm magnetic iron oxide nanoparticles in the silica matrix, and this highly dispersible material can be easily separated from aqueous solution by a magnetic field. Functionalization of the surface with selected ligands and metal complexes creates powerful capabilities for chemical separation and catalysis. Fe3+-magMCM-41 prepared by grafting aminopropyls and then adsorbing Fe3+ was found to be a highly selective adsorbent which adsorbed only As(V) and Cr(VI) oxyanions (70 and 100 mg g-1, respectively) without any Cu(II). A series of salt-tolerant sorbents with designed functionalized groups were capable of removing 97~99% toxic heavy metals with a Kd (distribution coefficient) value as high as 106 from seawater. Meanwhile, the catalytic performances of modified materials were tested for Knoevenagel condensation reactions. The result showed the conversion excessed 97% (30 min) at 393 K on the catalyst “Mag-NH2-MCM-41” which was easily recovered with external magnetic field. Thus, the chemically-modified materials based on MCM-41 were proven to be excellent selective sorbents and good catalysts. A more efficient, continuous, cleaner and reliable manufacturing method for mesoporous materials was developed using a microfluidic reactor. MCM-41 was successfully prepared in the microreactor and the physical properties were examined by different characterization techniques to ensure the quality. The continuous synthesis of mesoporous silica has a great potential industrial application