Arabian Journal for Science and Engineering https://doi.org/10.1007/s13369-024-09239-4 RESEARCH ARTICLE-CHEMISTRY Synthesis, Characterization and Photocatalytic Activity of Iron(II) and Iron(III) Coordination Polymers Derived from Terephthalic Acid Safa Faris Kayed 1 · Hessah Saleh Alowais 1 Received: 2 February 2024 / Accepted: 26 May 2024 © King Fahd University of Petroleum & Minerals 2024 Abstract The growing demand for disinfection of polluted waters from different sources has led to the development of new and more effective water purification technologies. Photocatalysis holds great promise as an efficient and sustainable oxidation tech- nology for application in wastewater treatment. Coordination polymers CPs have attracted ever growing research interest as a new kind of potential photocatalyst because of their unique properties of designable structure. New coordination polymers have been prepared by condensation of terephthalic acid with iron(II) and iron(III) ions. The corresponding structures have been described by infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy, X-ray powder diffraction and thermogravi- metric analysis. The obtained data revealed that the Iron(II) polymer exhibits an infinite one-dimensional chain structure; while, Iron(III) polymer exhibits a three-dimensional metal–organic framework structure. The FTIR results suggested that the terephthalic acid was coordinated to the metal center as a dibasic tetradentate manner. The behavior of thermal decom- position for the prepared polymers was discussed. The kinetic and thermodynamic parameters have been evaluated using the Coats–Redfern method. The photocatalytic performances of the polymers for decomposition of methyl orange under UV irradiation were studied. The effect of parameters such as addition of H 2 O 2 and pH of the dye solutions on the removal effi- ciency of methyl orange was also investigated. The prepared polymers promising photocatalytic activities for the degradation of methylene orange in water at room temperature. Keywords Terephthalic acid · CPs · MOFs · Photocatalyst · TGA 1 Introduction Photocatalysis is a promising technique for biodegradation and pollution control. Over the years, research has been con- ducted using a whole series of materials as photocatalysts for the purpose of organic decomposition and degradation of other wastes. Photocatalysis involves oxidation and reduc- tion reactions with the help of photo-emitted charge pairs under light. Photocatalysis creates strong oxidation agent to breakdown any organic matter to carbon dioxide and water in the presence of photocatalyst, light and water. The optimiza- tion principles for highly efficient photocatalysts include high B Safa Faris Kayed safaafaris@yahoo.com; s.kayed@psau.edu.sa 1 Department of Chemistry, College of Science and Humanities in Al-Kharj, Prince Sattam Bin Abdulaziz University, 11942 Al-Kharj, Saudi Arabia light response and utilization ability, excellent chemical— physical stability, low cost, and environment friendliness [1–4]. Coordination polymers have recently received much atten- tion because of their potential applications in the fields of photochemistry, molecular magnetism, gas storage, hetero- geneous catalysis and nonlinear optics [5–10]. Coordination polymers are infinite systems build up with metal ions and organic ligands (called as linkers) as main elementary units linked via coordination bonds and other weak chemical bonds. Such metal–ligand compounds can extend “infinite- ly” into one, two or three dimensions (1D, 2D or 3D, respectively) via more or less covalent metal–ligand bond- ing. The ligand must be a bridging organic group. At least in one extended dimension the metal atoms must solely be bridged by this organic ligand [10]. Formation of coor- dination polymers form building blocks occur mainly via coordination bond. Coordination bonds are formed by the donation of a lone electron pair of the ligand (Lewis base) to the metal cation (Lewis acid) and electrostatic attractions 123