Transition- and Lanthanide-Metal-Based Coordination Polymers Offer Efficient Methylene Blue Adsorption

This study presents a novel approach toward wastewater remediation via the synthesis of a series of coordination polymers that combine benzene-1,4-dicarboxylic acid, benzene-1,4-dihydroxamic acid, and 5-nitroisophthalic acid linkers with Cu, Cr, Ce, and La metal salts to target efficient methylene blue removal. Through a detailed characterization process using techniques like ¹H NMR, PXRD, FTIR, TGA, SEM-EDX, ICP-OES, and BET, the structural and surface properties of these CPs were optimized for stability and enhanced adsorption performance. Notably, the CPs exhibited rapid MB adsorption within 10 min and followed pseudo-second-order kinetics, indicating a chemisorption-driven process. This work advances the field by demonstrating that increased pH significantly improves adsorption capacity and that the Sips model best describes the heterogeneous adsorptive behavior, highlighting a mixed Langmuir–Freundlich mechanism. Furthermore, stability and reusability studies revealed minimal metal leaching in the best-performing CPs, addressing critical environmental concerns around long-term CP use. This integrated approach not only fills vital knowledge gaps in CP-based dye adsorption kinetics but also underscores the potential of these materials as sustainable, scalable, and effective solutions for real-world water treatment applications.