Solvothermal Synthesis, Structure, and Properties of Metal Organic Framework Isomers Derived from a Partially Fluorinated Link

Solvothermal reactions of Cu(NO 3 ) 2 ·3H 2 O with 4,4′-(hexafluoroisopropylidene) bis(benzoic acid) (C 17 H 10 F 6 O 4, H 2 hfbba) and terminal monodentate ligand 3-methyl pyridine (3-picoline/3-mepy) in the presence of N, N -dimethyl formamide (DMF) and N, N -diethyl formamide (DEF) solvents gave rise to two structurally different two-dimensional (2D) fluorinated metal organic frameworks ( F -MOFs). The effect of the choice of solvent has been clearly reflected in the structures obtained. The F -MOFs reported in this paper are formulated as [Cu 2 (hfbba) 2 (3-mepy) 2 ]·(DMF) 2 (3-mepy) ( F- MOF-4 ), [Cu 2 (hfbba) 2 (3-mepy) 2 ] ( Cu- F -MOF-4B ), and [Zn 2 (hfbba) 2 (3-mepy) 2 ]·(3-mepy) ( Zn- F- MOF-4B ) which displays interesting 2D structures with and without interdigitation depending on the solvent used. The structures of these F -MOFs have been determined by X-ray crystallography and further identified by IR spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric analysis (TGA). The effect of interdigitation has been reflected in the gas adsorption and magnetic properties of these F- MOFs. These F -MOFs also show comparable H 2 and CO 2 uptake depending on their structural variation. Temperature-dependent magnetic susceptibility measurements over a wide range of temperatures exhibit dominantly short-range antiferromagnetic behavior, with weak ferromagnetic behavior showing up at very low temperatures, which is evident from opening of the hysteresis loop with a finite value of coercivity in both F- MOF-4 and Cu- F -MOF-4B. We observed a smaller value of μ eff per Cu atom and coercivity in Cu- F -MOF-4B than the F -MOF-4 due to relatively larger distances between the neighboring dicopper paddlewheel secondary building unit.