Ce-NH2-BDC/HKUST-1-based binary metal–organic frameworks enabling efficient adsorption of methylene blue

Cerium–copper-based binary metal–organic frameworks (MOFs), referred to as Ce-NH₂-BDC/HKUST-1, abbreviated as CCB-MOFs, were synthesized using 1,3,5-benzenetricarboxylic acid and 2-aminoterephthalic acid ligands for the removal of methylene blue (MB) from aqueous solutions. The sharp and intense diffraction peaks confirm the crystalline nature of the CCB-MOF. The chemical structure and functional groups of CCB-MOF were examined through FT-IR analysis. The scanning electron microscope image of CCB-MOF shows a spherical morphology and indicates that Ce-MOF forms a layer on top of Cu-MOF. X-ray photoelectron spectroscopy analysis confirms the presence of metal nodes and organic linkers in the synthesized binary MOF. Brunauer–Emmett–Teller analysis reveals that CCB-MOF possesses a surface area of 52.36 m² g⁻¹. The study on the adsorption properties of MB dye on CCB-MOF demonstrated that the optimum dye removal efficiency of approximately 98 % was achieved at pH 7, a minimal contact time of 60 min, and ambient temperature. The adsorption isotherm fitted the linear Langmuir isotherm model, and the kinetics of the adsorption was described by the pseudo-second-order kinetic model. The maximum MB dye adsorption capacity of CCB-MOF estimated by the Langmuir isotherm model was up to 172.41 mg g⁻¹. The experimental results demonstrate that the adsorption of MB dye on CCB-MOF is primarily driven by electrostatic attraction between CCB-MOF and the MB dye. This study provides new insights into developing CCB-MOF-based adsorbents for recovering MB dye from aqueous solutions.