Tailoring Surface and Structural Properties of MCM-41 Silicas by Bonding Organosilanes

Abstract

Large pore MCM-41 silica with the pore diameter of 5.0 nm was chemically modified by bonding monomeric-type ligands, such as trimethylsilyl, butyldimethylsilyl, and octyldimethylsilyl, as well as polymeric-type 3-aminopropylsilyl, (hexanoyl-3-aminopropyl)silyl, and octylsilyl ligands. The obtained materials were characterized using elemental analysis, high-resolution thermogravimetry (TGA), and nitrogen adsorption at 77 K in a wide range of pressures. Surface coverages of bonded ligands were between 2.5 and 3.0 μmol/m2. It was shown that pore diameters of the samples studied decreased systematically with the increase in size of ligands. The modified materials exhibited narrow and monodisperse pore size distributions, indicating that the chemical bonding procedure did not diminish the structural ordering of the MCM-41 support. TGA data showed that the surface affinity to water was strongly dependent on the structure and functionality of the bonded species. Nitrogen adsorption data provided additional information about surface properties of the materials. A significant decrease in the amount of nitrogen adsorbed at low pressures was observed for the modified samples, especially those with long-chain alkyl groups. Low-pressure adsorption data were used to calculate adsorption energy distributions (AEDs), and peaks on these distributions were assigned to certain groups present on the silica surface or in the structure of bonded phases. It was thus demonstrated that the pore size and surface functionality of ordered mesoporous silicas can be engineered by a proper choice of the pore diameter of the support and the size and structure of bonded ligands. Nitrogen adsorption measurements including low-pressure data were shown to be a powerful tool to characterize structural and surface properties of unmodified and surface-modified novel porous materials.

Influence of Basic Red 1 dye adsorption on thermal stability of Na-clinoptilolite and Na-bentonite

“…1, 2; Table 1). Similar changes were observed in the case of the modification of silica gels by coal deposits [28,29], proteins [30], and organosilanes [31,32].…”

FTIR thermal analysis on organofunctionalized silica gel

“…TGA (Thermal Gravimetric Analysis) is a useful procedure for the characterization of the organic grafting process 7,[11][12][13][14][15] . This technique allows the study of interaction strength between the attached organic groups and the surface with increasing temperature.…”

Multifunctional Amine Mesoporous Silica Spheres Modified with Multiple Amine as Carriers for Drug Release

“…Figure 6 shows the TG curves of the materials. All samples show an obvious weight loss up to 100 ∘ C due to the desorption of physically adsorbed water [38]. In addition, there is no obvious weight loss attributed to the disintegration of MSN-40 suggesting that the MSN-40 is thermally stable.…”

“…The MSN-40/CTAB has significant weight loss due to surfactant CTAB loss of MSN-40/CTAB at 100-500 ∘ C. For amine functionalized samples, the TG curves have a rapid weight loss at 200-800 ∘ C, which is due to the removal of multiamine groups [21]. This is significant evidence of the existence of amine groups on the surface and inner pore of MSN-40 [21,38,39]. The MSN-DQ-40 can be further confirmed due to fairly obvious weight loss compared to MSN-NH 2 -40.…”