Syntheses, structural diversity, and photocatalytic-degradation properties for methylene blue of Co(ii) and Ni(ii) MOFs based on terephthalic acid and different imidazole bridging ligands

Abstract

Six coordination polymers named [Co(TPA)(bimb)(H₂O)₂]_n (1), [Co(TPA)(4,4′-bidpe)]_n (2), [Co(TPA)(4,4′-bibp)]_n (3), [Co₄(TPA)₃(tib)₂(μ₃-OH)₂]_n (4), [Ni(TPA)(4,4′-bidpe)(H₂O)₂]_n (5), and [Ni₂(TPA)₂(4,4′-bibp)₃(H₂O)₂]_n (6) (TPA = terephthalic acid, bimb = 1,4-bis(imidazol)butane, 4,4′-bidpe = 4,4′-bis(imidazolyl)diphenyl ether 4,4′-bibp = 4,4′-bis(imidazolyl)biphenyl, and tib = 1,3,5-tris(1-imidazolyl)benzene) were constructed using a solvothermal method and characterized by X-ray diffraction, elemental analyses, infrared spectroscopy and thermogravimetric analysis. Complex 1 had a 3D supermolecular framework that crystallized in the monoclinic space group P2₁/c. Complex 2 crystallized in the tetragonal system I4₁/acd space group featuring a 2-fold interpenetrated framework. Complex 3 crystallized in the orthorhombic space group Pnna. Complex 4 exhibited a 3D Co(II) metal–organic framework with tetranuclear metal–oxygen clusters, and it crystallized in the monoclinic space group C2/c. Complex 5 crystallized in the monoclinic space group P2₁/n featuring a 3D supermolecular framework. Complex 6 had a 3D 3-fold interpenetrated fsc topological framework that crystallized in the triclinic space group P. The photocatalytic-degradation capacity of complex 1–6 for methylene blue (MB) was investigated: complex 1–4 had a better photocatalytic-degradation effect for MB.