Pyrazine functionalized large-pore metal-organic framework for efficient separation of acetylene/carbon dioxide and ethane/ethylene.

Efficient separation of acetylene (C2H2)/carbon dioxide (CO2) and ethane (C2H6) /ethylene (C2H4) represents a pivotal challenge in chemical production. Metal-organic frameworks (MOFs) have demonstrated significant potential for these separations owing to their designable pore structures. However, achieving a balance among adsorption capacity, guest affinity, and energy-efficient regeneration remains a significant challenge. In this study, we propose a strategy of introducing high electronegative N atoms into large-pore MOFs to gently regulate the host-guest interaction without losing adsorption capacity, hoping to solve the above problems. Based on this design, Al-TCPP (H4TCPP = 2,3,5,6-Tetrakis(4-carboxyphenyl)pyrazine) is constructed by replacing the benzene ring of Al-TCPB (Al-TCPB, H4TCPB = 1,2,4,5-Tetrakis(4-carboxyphenyl)benzene) with a pyrazine ring. While retaining high surface area and micropore volume, Al-TCPP shows higher gas uptake capacity and Ideal Adsorbed Solution Theory (IAST) selectivity. Theoretical calculations reveal that the pyrazine ring, as a weakly polar adsorption site, can improve the adsorption and separation ability of Al-TCPP compared with Al-TCPB. Finally, breakthrough experiments confirm that Al-TCPP exhibited more efficient separation and low energy regeneration. These results collectively demonstrate the feasibility of introducing mild adsorption sites into large-pore MOFs to balance adsorption capacity, guest affinity, and separation performance. This work provides design insights and reference templates for developing novel physical adsorbents.