An Isomeric Copper‐Diisophthalate Framework Platform for Storage and Purification of C2H2and Exploration of the Positional Effect of the Methyl Group

Abstract

AbstractThree isostructural metal‐organic frameworks (MOFs) based on dicopper paddlewheels and dimethyl‐functionalized linear diisophthalate ligands were solvothermally constructed, with the aim to investigate their performance regarding acetylene (C2H2) storage as well as separation and purification and to further understand the positional effect of the weakly polarized methyl functionality. Isotherm measurements and IAST selectivity analyses revealed that the three compounds exhibited the promising potential for storing C2H2and recovering C2H2from carbon dioxide (CO2) and methane (CH4) at ambient conditions. Furthermore, their C2H2adsorption properties can be tailored and optimized by altering the relative position of the methyl substituents immobilized in the organic linkers. At 298 K and 1 atm, the C2H2uptake capacities vary from 173.0 to 183.6 cm3 (STP) g−1, while the C2H2/CH4and C2H2/CO2adsorption selectivities are in the range of 24.5–26.6 and 4.34–4.70 for the equimolar gas mixtures. Theortho‐dimethyl‐modified MOF outperformed better than the other two MOF isomers. The results indicate that rational arrangement of functional groups can to some extent improve gas adsorption properties. Although the property discrepancy caused by the less‐polar methyl group is not as large as that by Lewis‐basic nitrogen atoms, this is the first experimental demonstration of the positional effect of methyl group on C2H2adsorption.