Integration of Open Metal Sites and Lewis Basic Sites for Construction of a Cu MOF with a Rare Chiral O h ‐type cage for high performance in methane purification

A Cu metal‐organic framework (MOF), [Cu 4 (PMTD) 2 (H 2 O) 3 ] ⋅ 20 H 2 O, 1 , (where PMTD is 1,4‐phenylenebis(5‐methyl‐4 H ‐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 CO 2 , 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 CH 4 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 CO 2 , C 2 H 6 , and C 3 H 8 over CH 4 in further calculating its separation capacity, as exemplified for CO 2 /CH 4 (50:50, 5:95), C 2 H 6 /CH 4 (50:50, 5:95), or C 3 H 8 /CH 4 (50:50, 5:95) binary gas mixtures. Breakthrough experiments show that 1 has a significantly higher adsorption capacity for CO 2 , C 2 H 6 , and C 3 H 8 than CH 4 . The selective adsorption properties of 1 make it a promising candidate for methane purification.