In the case of M41S, the surface properties of mesoporous molecular sieves could be changed
by covalently bonding organic groups to the inorganic siliceous framework. The two strategies most commonly
used to incorporate organic groups are post-synthetic silylation of the surface silanols or co-condensation of organosiloxanes with the framework silica source during hydrothermal synthesis. The chief benefits of post-synthetic silylation are simplicity and versatility, given the wide variety of commercially available silylation agents. RSi(OEt)3 and RSiCl3 are the most commonly used as silylating agents. Silylated materials possess lower BET surface areas and pore volume [7].