Selective adsorption of C2H2 and CO2 from CH4 in an isoreticular series of MOFs constructed from unsymmetrical diisophthalate linkers and the effect of alkoxy group functionalization on gas adsorption?

Journal of Materials Chemistry A Pub Date: 2018-01-24 DOI: 10.1039/C7TA10123F

Abstract

For acetylene production and natural gas purification, the development of porous materials exhibiting highly selective C2H2/CH4 and CO2/CH4 separations is very important but remains a major challenge. In this work, we employed three unsymmetrical diisophthalate ligands to construct an isoreticular series of copper-based MOFs exhibiting highly selective adsorption of C2H2 and CO2 from CH4 under ambient conditions. The gravimetric uptake capacities at 298 K and 1 atm vary from 171.7 to 200.4 cm3 (STP) per g for C2H2, and from 104.1 to 115.6 cm3 (STP) per g for CO2. The IAST adsorption selectivity is in the range of 27.6–34.5 for an equimolar C2H2/CH4 mixture, and 5.73–7.14 for an equimolar CO2/CH4 mixture at 298 K and 1 atm. These values are among the highest reported for MOFs constructed from bent diisophthalate ligands under the same conditions. The effect of alkoxy group functionalization on gas adsorption was also explored, revealing that compared to the parent compound, the alkoxy group functionalized MOFs exhibit a reduced uptake capacity but an improved adsorption selectivity. This work demonstrates that the three MOFs are promising materials for C2H2/CH4 and CO2/CH4 separations, and provides a fundamental understanding of alkoxy group functionalization on gas adsorption properties.

Graphical abstract: Selective adsorption of C2H2 and CO2 from CH4 in an isoreticular series of MOFs constructed from unsymmetrical diisophthalate linkers and the effect of alkoxy group functionalization on gas adsorption
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