Four Co(<scp>ii</scp>) coordination polymers based on 4,4′-(1H-1,2,4-triazol-1-yl)methylenebis(benzoic acid): syntheses, structural diversity, magnetic properties, dye adsorption and photocatalytic properties

Four functional metal–organic frameworks constructed from 4,4′-(1H-1,2,4-triazol-1-yl)methylenebis(benzoic acid) (H2tmlb), namely: {[Co4(tmlb)4(H2O)]&#183;2CH3CN&#183;4H2O}n (1), {[Co(tmlb)(bbibp)]&#183;1.5CH3OH&#183;2H2O}n (2), {[Co2(tmlb)2(bimmb)]&#183;6CH3CH2OH&#183;4H2O}n (3), and {[Co(tmlb)(bibp)(H2O)]&#183;DMA}n (4) (bbibp = 4,4′-bis(benzoimidazo-1-yl)biphenyl, bimmb = 1,4-bis(imidazol-1-ylmethyl)benzene, bibp = 4,4′-bis(imidazolyl)biphenyl), have been synthesized under solvothermal conditions. Four Co complexes have been characterized by elemental analysis, IR spectroscopy, single-crystal X-ray diffraction, thermogravimetric (TG) analysis and powder X-ray diffraction (PXRD). The single-crystal X-ray diffraction analysis reveals that complex 1 shows a two-fold interpenetrating (3,6,6)-connected framework with a Schlafli symbol of (4&#183;62)2(42&#183;610&#183;83) topology; complex 2 shows a two-fold interpenetrating uninodal 4-connected cds topology with a point symbol of (65&#183;8); complex 3 shows a 2D → 3D supramolecular structure through weak interactions; complex 4 shows a (3,4,6)-connected network with a point symbol of (4&#183;62)2(42&#183;64&#183;93&#183;106)(64&#183;9&#183;10) topology. Furthermore, the variable temperature magnetic susceptibilities of complexes 1–4 have been discussed. Complex 4 can selectively adsorb sulfate-containing dyes by Lewis acid–base interactions. And the four complexes all exhibit excellent photocatalytic capability in degradation of MB/MV.