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, [Co<sub>2</sub>O­(DPB)<sub>2</sub>(DMF)<sub>2</sub>]·<i>x</i>S (<b>1</b>), which represents a rare <i><b>reo</b></i>-type net with trigonal prismatic cobalt dimer, [Co<sub>2</sub>O­(CO<sub>2</sub>)<sub>2</sub>N<sub>4</sub>], as building blocks to construct a 3D framework containing three different types of nanoscale M<sub>12</sub>L<sub>12</sub> and M<sub>24</sub>L<sub>12</sub> 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, [Co<sub>2</sub>(MDPB)<sub>3</sub>(DMF)]­(NO<sub>3</sub>)·<i>x</i>S (<b>2</b>), with cobalt dimer, [Co<sub>2</sub>(CO<sub>2</sub>)<sub>3</sub>N<sub>4</sub>], as building blocks. Complex <b>2</b> 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 <b>1</b> exhibits permanent porosity and selective CO<sub>2</sub> uptake. Variable-temperature magnetic susceptibility measurements show that both <b>1</b> and <b>2</b> exhibit antiferromagnetic behavior.