A microporous chromium-organic framework fabricated via solvent-assisted metal metathesis for C2H2/CO2 separation.

ABSTRACT

Removal of CO2 or C2H4 from C2H2 is still a challenging task due to their similar physical-chemical properties. Here, a bifunctional ligand decorated with amino and sulfoxide groups, 5',5''''-sulfonylbis (2'-amino-[1,1'3',1''-terphenyl]-4,4''-dicarboxylic acid) (H4L), was employed to construct a new microporous iron-organic framework (Fe-MOF) with the formula [(Fe3O)(L)1.5(H2O)3]n. This MOF can serve as a parent structure to obtain the isostructural Cr-MOF by solvent-assisted metal metathesis. Furthermore, the gas adsorption and separation performance of these two MOFs were systematically investigated. Compared to Fe-MOF, Cr-MOF shows a moderately higher CO2, C2H2 and C2H4 uptake capacity. Additionally, Cr-MOF can selectively adsorb C2H2 over CO2 and C2H4. The separation potential towards C2H2/C2H4 and C2H2/CO2 was further established via IAST calculations of mixture adsorption equilibrium. IAST selectivity values of Cr-MOF are 3.4 for C2H2/C2H4 and 6.9 for C2H2/CO2 at 298 K and initial pressure, indicating its potential C2H2 separation ability.