Octa(aminophenyl)silsesquioxane fabrication on chlorofunctionalized mesoporous SBA-15 for CO2 adsorption

Chlorofunctionalized mesoporous SBA-15 was synthesized by a direct method, through one-step condensation of sodium silicate solution obtained from rice husk ash (RHA) and chloropropyltrimethoxysilane in presence of Pluronic 123 (surface directing agent). Octa(3-aminophenyl)octasilsesquioxane (OAPS) was grafted on chlorofunctionalized mesoporous silica SBA-15 and characterized by XRD, FTIR, BET and 29Si MAS-NMR. CO2 adsorption/desorption profiles of OAPS grafted chlorofunctionalized SBA-15 (Cl-SBA-15/ OAPS) at 25, 50 and 75 °C were obtained by TGA under atmospheric pressure. A maximum of 8 wt.% CO2 adsorption capacity (80 mg/g of adsorbent) was achieved over Cl-SBA-15/50% OAPS and it was also shown that the absorbent was recyclable, selective and thermally stable. Neat OAPS adsorbs almost no CO2 due to internally hydrogen-bonded amine. Cl-SBA-15/OAPS withstands high temperature (180 °C) significantly higher than the sorbent polyethyleneimine (PEI), which decomposes beyond 115 °C. Therefore, the use of rice husk ash (RHA) as silica source and high thermal stability of Cl-SBA-15/OAPS are advantageous for CO2 adsorption. Thus, grafting of octa(3-aminophenyl)silsesquioxanes on mesoporous SBA-15 broadens the applications of polyhedral oligomeric silsesquioxanes (POSS) compounds and verified to be a new candidate for CO2 capture.