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

Abstract

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.