Breathable Iron-Based MIL-88 Framework as Dye Adsorbent in Aqueous Solution

Metal–organic frameworks (MOFs) have been observed to exclusively eliminate dyes confined within their respective pores. In this investigation, the synthesis of a breathable MOF structure, MIL-88B(Fe), was pursued with the objective of circumventing restrictions on pore size to enhance its adsorption capabilities. The synthesis of MIL-88B(Fe) was carried out via the assisted solvothermal method at 373 K using inexpensive yet environmentally benign FeCl₃·6H₂O, 1,4-benzenedicarboxylic acid, and DMF as a metal precursor, linker, and solvent, respectively. Furthermore, the MOF was subjected to extensive analytical characterisation using XRD, FT-IR spectroscopy, N₂ gas sorption, TGA, and SEM. The experimental data showed that the utilisation of MIL-88B(Fe) with a dose level of 5 mg for 180 min at a pH of 9 led to the highest levels of adsorption for both dyes, with 162.82 mg g⁻¹ for methylene blue (MB) and 144.65 mg g⁻¹ for rhodamine B (RhB), as a result of the contrast in the molecular size between each dye. The Langmuir and Freundlich models demonstrated a correlation with isotherms, while the thermodynamic analysis demonstrated that MIL-88B(Fe) exhibits distinct endothermic and breathable properties. The efficacy of MIL-88B(Fe) adsorbent for MB and RhB in aqueous solutions indicated exceptional performance, stability, and noteworthy reusability performance.