Metal-organic frameworks based on octafluorobiphenyl-4,4′-dicarboxylate: Synthesis, crystal structure, and surface functionality

In contrast to aromatic carboxylates, the coordination polymers based on their perfluorinated analogues are not numerous. Here we present a series of six Zn(ii) coordination polymers of different dimensionalities (1D, 2D, and 3D) and porosities based on octafluorobiphenyl-4,4′-dicarboxylate (oFBPDC^2-) and N-containing co-ligands (ur, dabco, and bpy). These complexes are characterized by single-crystal X-ray diffraction, PXRD, FT-IR, elemental analysis, and TGA. The metal-organic frameworks [Zn₂(CH₃CONH₂)₂(oFBPDC)₂] (1) and [Zn₂(oFBPDC)₂(dabco)] (4) are shown to be porous with BET surface areas of 470 m² g^-1 and 441 m² g^-1, respectively. In addition, compound 4 shows selectivity factors of 11.3, 4.9 and more than 6 for the binary gas mixtures CO₂/N₂, CO₂/CH₄ and benzene/cyclohexane, respectively. The measurements for pressed powders and water droplet give water contact angles of 136° for 4 and 133° for (H₂bpy)[Zn₂(bpy)(oFBPDC)₃] (5). Low water uptake indicates that both 4 and 5 belong to highly hydrophobic solids.