Importance of the polarity on nanostructured silica materials to optimize the hydrolytic condensation with molecules related to CO2 adsorption.

The present work reports the changes for the mesoporous materials SBA-15 and KIT-6 associated with the structural, textural, and chemical properties when they are subjected to thermo-alkaline treatment. Despite the fact that the silica supports have not a strong affinity for CO₂ adsorption, the adsorption enthalpy profiles (ΔH_ads) reported that the substrates subjected to the thermo-alkaline treatment (S15H and K6H) have a greater energetic affinity towards CO₂ capture if compared to the precursory solids (S15 and K6). The ΔH_ads is − 26.7 kJ mol⁻¹ at 0.15 mmol g⁻¹ by supported S15H and K6H while the ΔH_ads is − 20. 7 kJ mol⁻¹ and − 18.7 kJ mol⁻¹ by K6 and S15, respectively, at the same CO₂ coverage. Furthermore, the CO₂ adsorption performances by the hydrolytic condensation between silica supports and the N´- (3-trimethoxysilylpropyl)diethylenetriamine (NAEPTES) or 3-aminopropiltriethoxysilane (APTES) are presented and it can be seen that the best performer for CO₂ adsorption is reported for the S15HN since it is able to absorb 0.93 mmol at 0.15 atm at 318 K. Thereby, the outcomes show that the effects of porous curvature and the magnitude of the amine species are parameters to be considered, as well as the thermo-alkaline treatment, in order to improve the subsequent surface reactions on silica supports. The materials were characterized by XRD, TEM, and N₂ adsorption at 77 K, NIR, and pyridine thermodesorption using Fourier Transform Infrared Spectroscopy (FTIR-Py), NMR for ²⁹Si and ¹³C, DSC, and CO₂ adsorption. [ABSTRACT FROM AUTHOR]