Exploring the Fluorination and Hydroxylation of Pore‐space‐partitioned Metal‒Organic Frameworks for C2H2/CH4 Separation

We report three novel pore‐space‐partitioned metal‒organic frameworks (MOFs) functionalized with fluorine and hydroxyl groups using 2,3,5,6‐tetrafluorobenzene‐1,4‐dicarboxylic acid (F4‐BDC) and a new ligand 3,6‐difluoro‐2,5‐dihydroxybenzene‐1,4‐dicarboxylic acid (F2(OH)2‐BDC) as organic building blocks, with 1,3,5‐tris(4‐pyridyl)‐2,4,6‐triazine (TPT) as pore partition agent. With the polar fluorine and hydroxyl groups and the open metal sites being blocked by TPT, moderate molecule‐framework interactions can be engineered. These three isoreticular microporous frameworks Mn‐TPT‐BDC‐F4 (NCKU‐21), Mn‐TPT‐BDC‐F2(OH)2 (NCKU‐22), and Mg‐TPT‐BDC‐F2(OH)2 (NCKU‐23) (NCKU = National Cheng Kung University) exhibit distinct single‐component gas adsorption behaviors. Although NCKU‐22 uptakes a much lower amount of C2H2 compared to NCKU‐21 and ‐23, dynamic breakthrough experiments show that these three materials are all capable of efficient C2H2/CH4 separations. These MOFs possess moderate isosteric heat of adsorption for C2H2 (25.7‒32.1 kJ mol‒1), allowing easy regeneration and energy‐efficient C2H2/CH4 separations.