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

Abstract

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 C2H2/CO2 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 C2H2 molecules, a new microporous metal-organic framework (MOF) formulated as {[Co3(OH)2(HCOO)2(CPT)2](NMF)2(MeOH)3(H2O)}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 C2H2 (113 cm3/g at 298 K and 1 bar) over CO2 (33 cm3/g) under the same conditions. The different sorption behavior of {[Co3(OH)2(HCOO)2(CPT)2]}n between C2H2 and CO2 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 C2H2/CO2 separation performance, leading to its more favorable C2H2 uptakes than CO2.