Organic Functionalization and Morphology Control of Mesoporous Silicas via a Co-Condensation Synthesis Method

A series of new mesoporous silica materials with MCM-41 type of structure containing a homogeneous layer of organic functional groups inside the pores was prepared using a co-condensation method under low surfactant concentration condition. This reproducible synthetic approach resulted in high surface coverage with several functional groups such as a primary amine, secondary amine, urea, isocyanate, vinyl, and nitrile. In addition, the presence of organoalkoxysilane precursors during the base catalyzed condensation greatly influenced the final particle shape. By changing the precursor or its concentration, the particle morphology was tuned to various shapes, including spheres, tubes, and rods of various dimensions. The synthetic procedures that gave rise to the specific particle morphologies were investigated and the mechanism responsible for shape control was postulated. The structure and functionality of these materials were characterized by field-emission scanning electron microscopy, transmission electron microscopy, solid-state NMR spectroscopy, thermogravimetric analysis, and nitrogen adsorption and desorption studies (BET isotherms and BJH pore size distribution measurements).