Impregnating deep eutectic solvent choline chloride:urea:polyethyleneimine onto mesoporous silica gel for carbon dioxide capture

Development of green sorbents to capture carbon dioxide (CO2) whilst minimising their environmental impacts has gained interest among scientists. Deep eutectic solvent has been proposed as a promising green solvent for CO2 separation. In this study, a solid composite adsorbent based on mesoporous silica-gel (SG200) and deep eutectic solvent (DES) mixture of choline chloride:urea:polyethyleneimine (ChCl:U:PEI) was prepared by wet impregnation technique. The surface chemistry, thermal stability, surface porosity, CO2 adsorption capacity, and the effect of temperature on CO2 uptake by the adsorbents were studied. The highest CO2 adsorption of 51 mg/g at 25 °C and 1 bar was achieved by adsorbent with 25%ChCl:U:PEI loading, followed by 22%PEI (48 mg/g) and 24%ChCl:PEI (43 mg/g) loadings. Increased temperature was found to reduce the CO2 adsorption capacity. In addition, results from X-ray photoelectron spectroscopy (XPS) revealed the presence of cabamate ion after CO2 adsorption. This study revealed that the ternary DES, ChCl:U:PEI impregnated onto mesoporous silica sorbent has a promising potential to capture CO2.