Terephthalic acid-based coordination polymers: synthesis, thermal stability, and photocatalytic activity

Two coordination polymers were prepared by the reaction of terephthalic acid (H₂TPA) with zinc(II) and copper(II) metal ions. The structures of the prepared polymers were determined by elemental analysis, infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), and UV‒visible spectroscopy and thermogravimetric analysis (TGA). The obtained data revealed that the polymers exhibit an infinite 1D chain. The FTIR results indicated that the geometries surrounding the zinc(II) and copper(II) centers were close to tetrahedral, and that terephthalic acid (H₂TPA) was coordinated to the centers in a dibasic tetradentate manner through deprotonated hydroxyl and carbonyl oxygen atoms from both sides of H₂TPA, forming five-membered chelate rings. The polymers' thermal degradation behavior was examined. The Coats–Redfern method was used to determine the thermodynamic and kinetic characteristics of the thermal deterioration. Under UV light, the polymers' photocatalytic properties for methyl orange degradation were investigated. Investigations were also conducted on the influence of variables on the rate of methyl orange degradation, including the amount of catalyst and pH of the dye solution. However, the polymers that were produced had exceptional photocatalytic activity. When H₂O₂ was added, the efficiency of degradation increased. The breakdown of MO after 150 min irradiation is 91.79 and 94.98% for Zn(II) and Cu(II) polymers, respectively.