APTES grafted ordered mesoporous silica KIT-6 for CO2 adsorption

Abstract Pure KIT-6 was synthesized using pluronic P123 (PEO20PPO70PEO20, mw ∼ 5800 Da) surfactant in mild acidic condition. It was functionalized with (3-aminopropyl) triethoxysilane (APTES) by grafting in dry and aqueous solvent at 80 °C. Cubic (Ia3d) structure and uniformity of the adsorbents were analyzed by small angle powder X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Physical properties of the adsorbents were characterized by nitrogen adsorption/desorption behavior, infrared spectroscopy (IR) and thermo gravimetric (TG) analysis. CO2 adsorption/desorption behavior of the adsorbents was studied in a gravimetric analyzer. Optimum amine loading was substantially increased from 1.74 mmol N g−1 in dry grafting to 2.75 mmol N g−1 in aqueous grafting. The adsorption capacity was also remarkably increased from 0.90 mmol CO2 g−1 (An_K_9.0A) to 1.56 mmol CO2 g−1 (Aq_K_0.20W_9.0A) at 30 °C. The heat of adsorption of the process was in the range of 20–32 kJ mol−1. The adsorbent showed its stability with the adsorption capacity remaining constant over 10 adsorption/desorption cycles.