CO ₂ capture over molecular basket sorbent: Sorption mechanism study

Using solid sorbents to selectively capture CO ₂ from various gas streams, especially from flue gas, is of critical importance in mitigating the greenhouse gas emissions, and is a promising alternative because of its great potential in lowering energy requirements for regeneration and operation, and the cost for the CO ₂ separation process due to smaller process equipment, less expensive materials of construction, and inexpensive raw materials. In the past years, we have developed a novel sorbent material on the basis of molecular basket concept, so-called molecular basket sorbent (MBS). The sorbent has shown some potential advantages including high sorption capacity, high selectivity, fast CO ₂ sorption/desorption kinetics, easy regeneration and positive effect of moisture. However, the CO ₂ sorption mechanism over MBS is still not clear. As a continuous work, the present paper will report our current efforts and progress in the study of the fundamentals on CO ₂ sorption mechanism over MBS material by using in-situ FT-IR, CO ₂ temperature-programmed desorption method (CO ₂-TPD) and the computational simulation. Through the study, two sorption species, surface carbamate species and chemically sorbed CO ₂ molecules within the sorbent bulk have been recognized by in-situ FT-IR. And two desorption stages, i.e. for the desorption of carbamate species and chemically sorbed CO ₂ molecules, and two sorption regions, i.e. kinetically and thermodynamically controlled regions in CO ₂ sorption over PEI/SBA-15 have also been identified and clarified. The CO ₂ sorption mechanism over MBS has consequently been proposed.