Flexible ligands-dependent formation of a new column layered MOF possess 1D channel and effective separation performance for CO2

Abstract

A new column layered MOF with (3,6)-connected nets, namely [Co(pysa)(H2O)]n (YAU-7), was synthesized by using Co(NO3)2·6H2O and organic ligand 2-(pyrid-4′-yl)-benzimidazole-5-carboxylic acid (H2pysa) as flexible linkers. Single-crystal X-ray diffraction evidences the 3D YAU-7 MOF with (3,6)-connected nodes, a binuclear cluster [Co2(COO)2] structure and 1D tunnel feature. The weak interactions of π---π stacking enhances chemical stability of YAU-7 3D structure. Interestingly, the YAU-7 presents high chemical/thermodynamic stability, superior adsorption performance for CO2, CH4, C2H2 and C2H4, and high IAST selectivities for mixed gas systems of C2H2/CO2, C2H4/CO2, and CH4/CO2 (50/50). In contrast, YAU-7 exhibits higher uptake of CO2 (55.70 ​cm3 ​g−1) compared with CH4, C2H2, and C2H4 (27.39, 23.36, and 9.04 ​cm3 ​g−1) at 273 ​K. YAU-7 takes separation values for C2H2/CO2, C2H4/CO2, and CH4/CO2 mixture (37.6, 22.7, and 31.2) significantly higher than the C2H2/C2H4, C2H2/CH4, C2H2/CO2, C2H4/CH4 mixture gas (1.30, 1.83, 1.67). The YAU-7 MOF is a promising material for CO2 separation under ambient conditions.