Removal of anionic and cationic dyes using porous copolymer networks made from a Sonogashira cross-coupling reaction of diethynyl iron (II) clathrochelate with various arylamines

Four copolymers containing alternating units of iron(II) clathrochelate with various arylamine CLA1-4 were synthesized via a palladium-catalyzed Sonogashira cross-coupling reaction using an iron(II) clathrochelate synthon end-capped with ethynyl groups with various brominated arylamine derivatives. Target copolymers CLA1-4 were characterized by various instrumental analysis techniques, such as, solid-state ¹³C-nuclear magnetic resonance (SSNMR), Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS). Thermogravimetric analysis (TGA) disclosed the superior thermal stability of the target copolymers with 10% weight loss temperature values up to ~340°C. Nitrogen adsorption measurements of CLA1-4 using Brunauer–Emmet–Teller (BET) model revealed their porous nature with a surface area and porosity up to ~411 m² g⁻¹ and 0.411 cm³ g⁻¹, respectively. Interestingly, CLA1-4 disclose efficient adsorption of both cationic and anionic organic dyes, such as, Methylene Blue (MEB), Rhodamine B (RB), Congo Red (CR), Methyl orange (MO), and Acid orange 7 (AO7) from aqueous solutions. Furthermore, the isothermal adsorption study divulges the CLA4 uptake from aqueous solution of MEB and CR following the Langmuir model with a maximum adsorption capacity (q_m) of 146.63 mg g⁻¹ and 787.40 mg g⁻¹, respectively.