Adsorption, Thermogravimetric, and NMR Studies of FSM-16 Material Functionalized with Alkylmonochlorosilanes

Two series of alkyl-modified molecular sieves were prepared using the FSM-16 mesoporous silica. The attachment of alkyl groups to the surface, the structure of the bonded layer, and changes in the mesoporous structure of the FSM-16 material upon functionalization were studied by means of high-resolution thermogravimetry, elemental analysis, nitrogen adsorption, and 13C and 29Si NMR. Surface coverages of attached ligands were in the range of 0.85−2.60 mmol/g. All modified samples showed a decrease in the pore size, which was in relation to the size of attached ligands. The uniformity of pores upon modification proves that the mesoporous structure of FSM-16 is retained after modification. The attachment of ligands takes place in a solvent either with a small amount of water or anhydrous indicating a direct reaction between the chlorosilane molecule and silanol groups and/or a reaction autocatalyzed by the small amount of water present on the FSM-16 surface. Nitrogen adsorption isotherms and the adsorption e...