Facile synthesis of magnetic hybrid metal–organic frameworks with high adsorption capacity for methylene blue

A magnetic hybrid material (Fe 3 O 4 -COOH/HKUST-1) was easily synthesized via a two-step simple solvothermal method. Through adding sodium acrylate directly into the synthesis of Fe 3 O 4 spheres, the surface has more carboxyl groups. It is notable that the reactions proceed without use of organic surfactants. The magnetic hybrid material was characterized using various techniques. The magnetic hybrid material has a high specific surface area (430.15 m 2 g −1 ) and excellent magnetism (23.65 emu g −1 ). It is an efficient adsorbent for removing organic dyes like methylene blue (MB) from aqueous solution. It also can be easily recovered from liquid media using an external magnetic field. Adsorption experiment shows the magnetic hybrid material possesses a high adsorption capacity (118.6 mg g −1 ), and has high adsorption efficiency (94.3%) after five adsorption cycles with ethanol (0.2% HCl) as eluent. The sorption kinetics and isotherm analysis indicate these sorption processes are better fitted to the pseudo-second-order and Langmuir equations. Thermodynamic study shows the sorption processes are spontaneous and endothermic.