Extraordinarily selective adsorption of CO2 over N2 in a polyethyleneimine-impregnated NU-1000 material

Abstract Developing an efficient adsorbent for selective separation and capture of CO 2 from CO 2 /N 2 mixture is an important and challenging issue for mitigating global warming. In this study, we posited that high CO 2 /N 2 selectivity could be obtained by impregnating polyethyleneimine (PEI) within the pores of NU-1000, a zirconium-based metal-organic framework (MOF), since it has a high surface area (∼2320 m 2 /g) and free and exposed OH groups but does not have unsaturated metal sites possibly having strong interactions with N 2 molecules. A series of PEI-impregnated NU-1000 (PEI(x)@NU-1000) materials with varied PEI loadings have been successfully prepared. As reasoned, PEI(50)@NU-1000 showed the highest CO 2 /N 2 selectivity among the PEI-loaded adsorbents in the literature under similar conditions. Remarkably, it exhibited extremely high CO 2 /N 2 selectivities (∼8000) at low pressures and a very high CO 2 /N 2 selectivity (661) at a typical pressure of flue gas (1 bar). Furthermore, PEI(50)@NU-1000 could efficiently separate CO 2 /N 2 mixture under a dynamic flow condition and maintained its CO 2 uptakes during three consecutive adsorption and desorption.