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

Abstract

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.