A moisture stable metal-organic framework for highly efficient CO2/N2, CO2/CH4 and CO2/CO separation

Utilizing porous adsorbents to capture CO2 from flue gas or removal of CO2 impurity from other high-value chemicals is an effective way for alleviating the greenhouse effect, but selective and reversible capture of CO2 is still a challenge. In this study, we report a moisture stable metal-organic framework (Zn-dmtrz-mip) that combines high CO2 uptake with a low affinity for other gases for highly efficient CO2 capture and separation performance. Zn-dmtrz-mip displays a high CO2 uptake of 65.4 cm3 g-1 as well as ultrahigh CO2/N2 (11974 and 681 for 50/50 and 15/85 mixtures, respectively), CO2/CO (110.0 and 50.8 for 50/50 and 10/90 mixtures, respectively), which superior to many reported MOFs. Breakthrough experiments visualized that Zn-dmtrz-mip is not only capable of directly obtaining high-purity (99.9 %) N2, CH4 and CO, but also achieving high-purity (99.5 %) CO2 recovery. The stability experiments showed that Zn-dmtrz-mip maintained its structure and CO2 adsorption uptake after exposure in air and moisture environments (RH = 65 %) as well as in acidic (pH = 3) and basic (pH = 11) solutions and water. Importantly, low CO2 adsorption heat (26.5 kJ mol- 1) makes Zn-dmtrz-mip can be easily regenerated by inert gas purging and maintain its separation performance over five repeat process cycles. Molecule simulation revealed the crucial role of methyl groups through multiple C-H center dot center dot center dot O interactions for such high CO2 uptake capacity and separation selectivity.