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

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 center dot 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 pi-electron surface.