Immobilization of open O-donor sites within a double-walled metal-organic framework for efficient C2H2/CO2 separation

Acetylene is an important industrial material for the production of acetaldehyde, acetic acid, benzene, synthetic rubber, synthetic fiber, etc., and its separation from the gas mixtures of C 2 H 2 /CO 2 is of great importance but a challenging task due to their similar physical properties and molecular sizes. In this study, taking the advantage of open-donor sites on the pore surface as the nano-traps for C 2 H 2 molecules, a new microporous metal-organic framework (MOF) formulated as {[C o 3 (OH) 2 (HCOO) 2 (CPT) 2 ](NMF) 2 (MeOH) 3 (H 2 O)} n ( 1 , NMF = N - methylformamide) has been prepared by virtue of a bifunctional organic ligand 4-(4H-1,2,4-triazol-4-yl)benzoic acid (HCPT), which showed discriminating sorption performance toward C 2 H 2 (113 cm 3 /g at 298 K and 1 bar) over CO 2 (33 cm 3 /g) under the same conditions. The different sorption behavior of {[C o 3 (OH) 2 (HCOO) 2 (CPT) 2 ]} n between C 2 H 2 and CO 2 results in a high uptake ration (3.4:1) and IAST selectivity (13) at 298 K and 1 bar. Furthermore, the force-field based grand canonical Monte Carlo (GCMC) simulation results demonstrate that the large electronegativity and polarizability of open O donor sites on the pore surface contribute to its high C 2 H 2 /CO 2 separation performance, leading to its more favorable C 2 H 2 uptakes than CO 2 .