Surface molecular design of organic–inorganic mesoporous hybrid materials for CO2 capture

Abstract

In the present work, a series of organic–inorganic hybrids was designed by using different solvents on 3-aminopropyltriethoxysilane (APTS) grafting on SBA-15. Different characterization techniques were used to evaluate how distinct solvents drive the surface architecture, amine loading, APTS-SBA-15 linkage configuration, surface area and pore volume. FT-IR and 29Si MAS NMR confirmed APTS grafting on SBA-15 surface. Elemental analysis showed that N loading varied from 2.09% up to 5.21%, while the range of C/N ratios (2.69–4.34) indicated that the number of bonds formed between APTS and SBA-15 (linkage configuration) remained between 2 (C/N = 4.3) and 3 (C/N = 2.6). N2 physisorption and TGA data showed that textural properties and APTS content on the synthesized materials were simultaneously dependent on N loading and linkage configuration. The presented data showed that the hybrids properties can be correlated with the solvent polarity, more specifically with the interaction between the inorganic matrix surface and the solvent during grafting. A new approach was presented using the solvent eluent strength to rationalize such correlation. Among all tested solvents, cyclohexane rendered the adsorbent with the highest N loading (5.21%) and more stable linkage configuration (C/N = 4.34). CO2 capture tests showed that the increase of amine loading and surface density improves not only the hybrid capacity to chemisorb CO2, but also its adsorption efficiency. CO2 capture capacities varied from 25 up to 516 µmol CO2 g−1. The correlation between adsorption capacity and N content for the synthesized APTS-SBA-15 hybrids was best fitted by a power function.