Surface engineering of γ-Al2O3 nanosheets with highly dispersed poly(ionic liquids) for selective CO2 adsorption

Abstract

An efficient CO2 adsorbent (γ-Al2O3 @PAVIMBr) was constructed by means of graft copolymerization with mesoporous γ-Al2O3 nanosheets served as the host material and amino-functionalized imidazolium based poly(ionic liquids) (PAVIMBr) as the guest material. Thereinto, mesoporous γ-Al2O3 could provided abundant hydroxyl groups for loading PAVIMBr uniformly via chemical bonding interaction, while PAVIMBr was able to tailor suitable pore size and expose amino-groups adsorption active sites that was contributed to chemisorb with CO2. It was observed that the general topography of γ-Al2O3 @PAVIMBr composite was almost unchanged after PAVIMBr loaded, and its mesoporous structure and crystalline form was still maintained. Moreover, the content of PAVIMBr in our composite could be calculated from the TGA results before and after its grafting. The obtained γ-Al2O3 @PAVIMBr presented a good CO2 adsorption performance, its CO2 adsorption capacity increased obviously. Meanwhile, the CO2/N2 selectivity of γ-Al2O3 @PAVIMBr was 15.3 times higher than that of γ-Al2O3 at room temperature and the pressure of 100 kPa, while the CO2 uptake of γ-Al2O3 @PAVIMBr was almost 13 and 3 times higher than that of PAVIMBr and γ-Al2O3 at 10 kPa and 25 °C, respectively. It was mainly attributed to that the maintaining mesoporous channels in γ-Al2O3 @PAVIMBr could accelerate the CO2 diffusion, while chemisorption of those exposed adsorption active sites from loaded PAVIMBr could improve the adsorption performance at lower CO2 partial pressure and CO2/N2 selectivity of our composite. Furthermore, the excellent CO2/N2 selectivity, renewability and physicochemical stability of γ-Al2O3 @PAVIMBr might employ it as one of the potential CO2 adsorbents.