3D Metal-Organic Frameworks Based on Co(II) and Bithiophendicarboxylate: Synthesis, Crystal Structures, Gas Adsorption, and Magnetic Properties.

Three new 3D metal-organic porous frameworks based on Co(II) and 2,2'-bithiophen-5,5'-dicarboxylate (btdc) [Co(btdc)(bpy)]·4DMF, ; [Co(btdc)(pz)(dmf)]·4DMF·1.5HO, ; [Co(btdc)(dmf)]∙2DMF∙2HO, (bpy = 2,2'-bipyridyl, pz = pyrazine, dmf = ,-dimethylformamide) were synthesized and structurally characterized. All compounds share the same trinuclear carboxylate building units {Co(RCOO)}, connected either by btdc ligands (, ) or by both btdc and pz bridging ligands (). The permanent porosity of was confirmed by N, O, CO, CO, CH adsorption measurements at various temperatures (77 K, 273 K, 298 K), resulted in BET surface area 667 m⋅g and promising gas separation performance with selectivity factors up to 35.7 for CO/N, 45.4 for CO/O, 20.8 for CO/CO, and 4.8 for CO/CH. The molar magnetic susceptibilities χ() were measured for and in the temperature range 1.77-330 K at magnetic fields up to 10 kOe. The room-temperature values of the effective magnetic moments for compounds and are μ (300 K) ≈ 4.93 μ. The obtained results confirm the mainly paramagnetic nature of both compounds with some antiferromagnetic interactions at low-temperatures < 20 K in between the Co(II) cations separated by short pz linkers. Similar conclusions were also derived from the field-depending magnetization data of and .