Metal-organic frameworks with linear and branched polyol backbones for dye removal

In this study, novel metal-organic frameworks (MOFs) were synthesized using functionalized polyols as organic ligands. Polyvinyl alcohol (PVA) and hyperbranched polyglycerol (hPG) were first mesylated and subsequently modified with 5-aminoisophthalic acid, followed by coordination with iron (III) chloride hexahydrate to form PVA-MOF and hPG-MOF structures. Comprehensive characterization, including FTIR, NMR, XRD, SEM/EDX, BET, zeta potential, and UV–Vis DRS analyses, confirmed successful polymer functionalization, preserved MOF crystallinity, porous morphology, high surface area, elemental composition, optical properties, and surface charge relevant to dye adsorption. The resulting MOFs exhibited high adsorption capacities toward both cationic (Rhodamine B and Methylene Blue) and anionic (Fluorescein) dyes from aqueous solutions. Isotherm analysis using Langmuir and Freundlich models revealed that dye uptake was best described by the Langmuir isotherm, indicating monolayer adsorption on a homogeneous surface, with maximum adsorption capacities ranging from 128.17 to 135.34 mg g−1 depending on the dye and MOF type. Thermodynamic studies demonstrated that the adsorption process was endothermic, with increased entropy, and spontaneous for the anionic dye, while non-spontaneous for the cationic dyes. The materials also showed excellent structural stability and reusability potential over three adsorption-desorption cycles. The adsorption performance was further validated using real water samples, confirming that PVA-MOF and hPG-MOF are promising and reusable adsorbents for efficient dye removal in wastewater treatment.