Alkylsilane-Functionalized Microporous and Mesoporous Materials: Molecular Simulation and Experimental Analysis of Gas Adsorption

Solid sorbents are considered as a potentially less-energy-intensive alternative to the use of liquids for the removal and separation of liquid and gaseous fluids. The control of the surface characteristics of porous inorganic materials via the deposition of an organic layer is of great interest for tailoring the properties of the sorbent. For instance, organic functionalization of traditional solid sorbents (micro- and mesoporous silica and silicates) allows tuning their surface properties, such as hydrophilicity or hydrophobicity and surface reactivity. However, the underlying mechanism of the sorption process in highly complex organic functionalized materials is not yet fully understood. This incomplete understanding limits the possibilities of designing optimal adsorbents for different applications increasing the interest in performing complementary experimental-simulation studies. In this work, the adsorption of N-2 in alkylsilane-modified disordered mesoporous silica (silica gel 40) and crystalline aluminosilicate (zeolite Y) is analyzed by a combination of experiments and simulations. The goal of the adsorption simulation study was twofold: first, to assess the ability of using grand canonical Monte Carlo to obtain quantitative predictions of the adsorption characteristics of gases on alkylsilane postfunctionalized products and, second, to provide new insights into the adsorption mechanism. A supercritical silanization experimental method was used for the postmodification of the internal surface of the studied porous substrates. This work demonstrates that even though the models of amorphous hybrid materials require simplifications related to the cell size and silane polymerization modes, it is possible to use these models to obtain an adequate insight of what happens in the macroscopic systems. These models allow us to acquire information on the mechanisms of silane functionalization and the interactions of the support and silane chains with the adsorbed gases.