Two pairs of isomorphism and two 3D metal–organic frameworks based on a star-like ligand tri(4-pyridylphenyl)amine

Six novel metal–organic frameworks (MOFs) have been synthesized in this paper, which are based on a N-centered ligand TPPA, namely, [Cd(TPPA)(fuma)]n (1), {[Zn(TPPA)(suc)]·5(H2O)·DMA}n (2), [Co(TPPA)(bhf)]n (3), [Zn(TPPA)(bhf)]n (4), [Co(TPPA)(oba)]n (5), and [Cd(TPPA)(oba)]n (6), [TPPA = tri(4-pyridylphenyl)amine, H2fuma = fumaric acid, H2suc = succinic acid, H2bhf = 2,2′-bis(4-carboxyphenyl)hexafluoropropane, H2oba = 4,4′-oxybis(benzoic acid)]. Compound 1 reveals a 4-fold interpenetrating 3D framework with AFUQOH topology. Compound 2 reveals a 2-fold interpenetrating 3D network with large void space (up to 37.6%). Compounds 3 and 4 are isomorphic 2D networks. Different from compounds 3 and 4, compounds 5 and 6 show 2D → 3D parallel polycatenation of undulated square layers. In addition, photochemical properties of compounds and the ligands in the solid state have been studied.