Porosity of SBA-15 after functionalization of the surface with aminosilanes

Abstract

Functionalization of the mesoporous silica walls by organic species results in formation of porous hybrid materials. Combination of organic and inorganic components leads to the materials whose properties differ considerably from those of their individual, isolated components, especially with respect to their surface chemistry, hydrophilicity/hydrophobicity and/or pore connectivity and size distribution. In this paper a detailed porosity characterization of SBA-15 silica before and after its surface functionalization with (R2O)3-Si-R1-NH2 molecules is reported. The results obtained from nitrogen sorption were compared to those derived from quasi-equilibrated thermodesorption of n-nonane and from water and n-heptane thermoporosimetry. A small decrease of the pores size and pore volume upon the modification was detected for all amine functionalities, the largest in the case of N-(2-aminoethyl)-3-(trimethoxysilyl) propylamine. Water thermoporosimetry was found to be the most sensitive method, allowing to quantify these differences.