Abstract
A Cu metal-organic framework (MOF), [Cu-4(PMTD)(2)(H2O)(3)]center dot 20H(2)O, 1, (where PMTD is 1,4-phenylenebis(5-methyl-4H-1,2,4-triazole-3,4-diyl)bis(5-carboxylato-3,1-phenylene)bis(hydroperoxymethanide)), with a rare chiral O-h-type cage, and dual functionalities of open metal sites and Lewis basic sites, based on a designed U-shaped ligand, was synthesized by hydrothermal methods. It exhibits high CO2, C-2, and C-3 hydrocarbon storage capacity under atmospheric pressure, as well as high H-2 (1.96 wt.%) adsorption capacity at 77 K. Methane purification capacity was tested and verified step by step. Isosteric heats (Q(st)) studies reveal that CH4 has the weakest van der Waals host-guest interactions among the seven gases at 298 K. Ideal adsorbed solution theory (IAST) calculation reveals that compound 1 is more selective toward CO2, C2H6, and C3H8 over CH4 in further calculating its separation capacity, as exemplified for CO2/CH4 (50:50, 5:95), C2H6/CH4 (50:50, 5:95), or C3H8/CH4 (50:50, 5:95) binary gas mixtures. Breakthrough experiments show that 1 has a significantly higher adsorption capacity for CO2, C2H6, and C3H8 than CH4. The selective adsorption properties of 1 make it a promising candidate for methane purification.