Construction of Novel Co(II) Coordination Polymers-Hydrogel Composites for Dye Adsorption

Abstract

Two new coordination polymers containing Co(II), thiophene-2,5-dicarboxylate and flexible bis(pyridyl) ligands were synthesized and formulated as [Co2(mu-tdc)(mu 4-tdc)(mu-bpe)2]n (CP1) and [Co2(mu 3-tdc)2(mu-H2O)(H2O)2(mu-bpp)]n (CP2), where; H2tdc: thiophene-2,5-dicarboxylic acid, bpe: 1,2-bis(4-pyridyl)ethane, bpp: 1,3-bis(4-pyridyl)propane. The CPs were characterized by elemental analysis, ATR-IR spectroscopy and single-crystal X-ray diffraction techniques. Powder X-ray diffraction experiments were performed to confirm the phase purity of the CPs. According to the results of single-crystal X-ray diffraction analysis and topological analysis, CP1 and CP2 exhibit 3D+3D -> 3D interpenetrated framework with pcu topology. Furthermore, the optical and thermal properties of the CPs were also investigated. Also, in this study, hydrogel composites were synthesized by using synthesized new type Co(II)-thiophene-2,5-dicarboxylate based coordination polymers and acrylic acid (AA) monomer. The swelling behavior of the synthesized new type hydrogel composite systems was investigated at three different solution pH (3, 7 and 11) and adsorption studies were carried out with methylene blue dye. In addition, it has been shown that the systems can be reused by using hydrogel composite systems in three consecutive adsorption/desorption cycles.