Assembly of Two Metal–Organic Frameworks Based on Distinct Cobalt Dimeric Building Blocks Induced by Ligand Modification: Gas Adsorption and Magnetic Properties

Solvothermal reaction of 3,5-di­(pyridin-4-yl) benzoic acid (HDPB) with Co­(II) leads to a novel metal–organic framework, [Co₂O­(DPB)₂(DMF)₂]·xS (1), which represents a rare reo-type net with trigonal prismatic cobalt dimer, [Co₂O­(CO₂)₂N₄], as building blocks to construct a 3D framework containing three different types of nanoscale M₁₂L₁₂ and M₂₄L₁₂ polyhedron cages. More interestingly, under the same condition, the assembly of 4-methyl-3,5-di­(pyridin-4-yl) benzoic acid (HMDPB) with Co­(II) facilitates the formation of a cationic framework, [Co₂(MDPB)₃(DMF)]­(NO₃)·xS (2), with cobalt dimer, [Co₂(CO₂)₃N₄], as building blocks. Complex 2 represents the first example of a zeolite-like network with 48-nuclear SOD cage. The significant effect of subtle modification of ligand on the overall MOFs is discussed. Moreover, the gas adsorption studies reveal that 1 exhibits permanent porosity and selective CO₂ uptake. Variable-temperature magnetic susceptibility measurements show that both 1 and 2 exhibit antiferromagnetic behavior.