Controlling structural topology of metal-organic frameworks with a desymmetric 4-connected ligand through the design of metal-containing nodes

Two new metal-organic frameworks (MOFs), [Cu2(H2O)2(BCPIA)] (BUT-20) and (Me2NH2)[In(BCPIA)] (BUT-21) were designed and synthesized through the solvothermal reaction between a newly created desymmetric 4-connected ligand, 5-(2,6-bis(4-carboxyphenyl)pyridin-4-yl)isophthalic acid (H4BCPIA) and Cu(NO3)2·2.5H2O or In(NO3)3·5H2O, respectively, and characterized by single-crystal and powder X-ray diffraction, thermogravimetric analysis, infrared spectroscopy, and elemental analysis. The two MOFs have three-dimensional structures, in which both the BCPIA4– ligand and metal-containing entities, Cu2(COO)4(H2O)2 and In(COO)4 act as 4-connected nodes. However, different linkage configurations of the two metal-containing nodes, quadrilateral Cu2(COO)4(H2O)2 and tetrahedral In(COO)4, lead to distinct structural networks of BUT-20 and -21, with Nbo and Unc topologies, respectively.