Highly Selective Separation of C2H2/CO2 and C2H2/C2H4 in an N-Rich Cage-Based Microporous Metal-Organic Framework

The separation of acetylene (C 2 H 2 ) from carbon dioxide (CO 2 ) and the purification of ethylene (C 2 H 4 ) from C 2 H 2 are quite essential processes for the chemical industry. However, these processes are challenging due to their similar physical properties, including molecule sizes and boiling points. Herein, we report an N-rich cage-based microporous metal-organic framework (MOF), [Cd 5 (Tz) 9 ](NO 3 ) (termed as Cd-TZ, TZ stands for tetrazole), and its highly efficient separation of C 2 H 2 /CO 2 and C 2 H 2 /C 2 H 4 . Single-component gas adsorption isotherms reveal that Cd-TZ exhibits high C 2 H 2 adsorption capacity (3.10 mmol g -1 at 298 K and 1 bar). The N-rich cages in Cd-TZ can trap C 2 H 2 with a higher isosteric heat of adsorption (40.8 kJ mol -1 ) than CO 2 and C 2 H 4 owing to the robust host-guest interactions between the noncoordinated N atoms and C 2 H 2 , which has been verified by molecular modeling studies. Cd-TZ shows a high IAST selectivity for C 2 H 2 /CO 2 (8.3) and C 2 H 2 /C 2 H 4 (13.3). The breakthrough simulations confirm the potential for separating C 2 H 2 /CO 2 and the purification of C 2 H 4 from C 2 H 2 .