Surface functionalization of handleable silica-based mesoporous materials for CO2 sequestration: Synthesis, characterization and performance

Two different types of silica monolith based on commercial hydrophobic Aerosil200 and hydrophilic Sipernat320 (Evonik) were successfully covalently functionalized with different amines as CO2 sequestrants. 3-aminopropyltriethoxysilane (AMPS) was used for a first functionalization and applied as it is or as linker to extend the chain length with diglycine (diGly) and triglycine (triGly). The physico-chemical characterization of the samples comprehends nitrogen adsorption at -196 °C to determine surface area and porosity and thermogravimetric analysis (TGA) to evaluate the thermal stability of the materials and quantify the extent of functionalization. CO2 and N2 adsorption microcalorimetry, coupled with FTIR spectroscopy, was used to evaluate the ability of the materials to selectively sequestrate CO2 against N2 in post-combustion procedures and the reversibility of the process. The comparison with a powdery commercial activated carbon, taken as reference, evidences the good adsorption capacity (comparable to that of the carbon reference) of monoliths from Sipernat 320 bringing a short aliphatic chain and terminal -NH2 groups (more than 700 μmol/g of CO2 sequestrated at 30 °C), and the advantages in term of easy storage and recoverability, with respect to powdery adsorbents.