An aromatic-rich cage-based MOF with inorganic chloride ions decorating the pore surface displaying the preferential adsorption of C2H2 and C2H6 over C2H4

Abstract

Separation and purification of C₂H₄ produced by thermal decomposition of C₂H₆ involve the elimination of C₂H₂ impurities and unconverted C₂H₆ from C₂H₄, which is of great practical importance but a great challenge in the petrochemical industry. Herein, a new MOF [Cu₄L₃Cl]Cl·2.7DMF (H₂L = 5-(pyrimidine-5-yl)isophthalic acid, DMF = N,N-dimethylformamide) based on a heterotopic N,O-donor ligand was solvothermally constructed, featuring saturated metal centers as well as inorganic chloride ions immobilized in the aromatic cage surface that offers a favourable pore environment for binding C₂H₂ and C₂H₆ in preference to C₂H₄. Pure component isotherm measurements and IAST selectivity calculations revealed that the resultant MOF solid displayed the potential for the separation and purification of C₂H₄ by simultaneously trapping C₂H₂ and C₂H₆ from C₂H₄ under ambient conditions. Furthermore, the mechanism on preferential adsorption of C₂H₂ and C₂H₆ over C₂H₄ was comprehensively investigated by DFT theoretical calculations, revealing the crucial role of the electronegative chloride ion and aromatic π-electron surface.