Study of silica-based ordered mesoporous sorbents for gas sweetening through concatenated computer simulation techniques

This thesis is focused on MCM-41 and SBA-15 as sorbents to fight the role of CO2 as a greenhouse gas. The sorption efficacy of these silica-based mesostructured materials is related to their ordered pore structure and versatile functionalization. The use of amine moieties is reported to enhance CO2 adsorption and, besides the experimental characterization, computational techniques play a crucial role in understanding the adsorption process at a microscopic level and designing optimized materials. Accurate atomistic models of MCM-41 and SBA-15 were obtained by employing the information from complementary experimental techniques. However, the determination of the specific surface area and pore size distribution can be obtained with different approaches to experimental data analysis, which have been compared by reconstructing in-silico the experimental N2 physisorption isotherms. The adsorption capacity and selectivity of bare mesostructured silica for CO2/CH4 mixtures was investigated, providing insights into the physisorption process, and rationalizing macroscopic performance based on surface density and pore curvature. Different types of silanolic sites contribute to material heterogeneity, affecting selectivity. After functionalization, the local density of amine groups mostly influences CH4 adsorption and selectivity. The importance of silanol groups on the silica surface is highlighted, as they influence the physisorption process and material performance, even after functionalization. A novel SBA-15 model was introduced, with a complex and realistic microporous network, showing significant impacts on CO2 adsorption capacity and selectivity. Preliminary results suggest the relevant role of micropores that cannot be overlooked. Overall, the text highlights the importance of understanding CO2 adsorption behavior in mesostructured materials through computational techniques, aiding the development of efficient sorbents for carbon capture and utilization strategies.