Two copper-based MOFs constructed from a linear diisophthalate linker: supramolecular isomerism and gas adsorption properties

Abstract

Combining a linear diisophthalate ligand, 5,5′-(2,3-dimethylbenzene-1,4-diyl)diisophthalic acid, with CuCl₂·2H₂O under different solvothermal conditions afforded two distinct copper-based metal–organic frameworks (ZJNU-96 and ZJNU-97), which were structurally characterized by various techniques. Single-crystal X-ray diffraction analyses reveal that they contain the same inorganic and organic building units but exhibit different topological structures, thus belonging to supramolecular isomers. Furthermore, gas adsorption studies show that ZJNU-96 not only exhibits better stability against desolvation than ZJNU-97 but also displays promising potential for selective adsorptive separation of C₂H₂ and CO₂ from CH₄, with C₂H₂ (CO₂) uptake of 183.6 (88.7) cm³ (STP) g⁻¹ and C₂H₂ (CO₂)/CH₄ (v/v, 50/50) IAST adsorption selectivity of 26.6 (5.2) at 298 K and 1 atm.