Highly selective CO2 separation from a CO2/C2H2 mixture using a diamine-appended metal–organic framework

The effective separation of carbon dioxide (CO2) from acetylene (C2H2) in a gas mixture (CO2/C2H2) during the purification process is an important industrial demand since C2H2 is widely used in chemical products but is challenging due to the similar physicochemical properties of both gases. Herein, we report highly selective chemisorptive CO2/C2H2 separation using diamine-appended metal–organic frameworks (MOFs) with strong acid–base interactions between CO2 and amine groups, enabling specific recognition of CO2 over C2H2. These functionalized MOFs exhibited preferential uptake of CO2 over C2H2 at 298 K and 1 bar. They showed the highest CO2 adsorption capacities (3.58–3.82 mmol g−1) at 30 mbar, which is the partial pressure of CO2 during the C2H2 purification process. Furthermore, the adsorption selectivity and recyclability of these MOFs for CO2 over C2H2 in the gas mixture were verified by dynamic breakthrough experiments. This work demonstrates that diamine-appended MOFs are promising adsorbents to produce high-purity C2H2 by means of selective capture of CO2 from a CO2/C2H2 mixture.