Facile synthesis of size-controlled MIL-100(Fe) with excellent adsorption capacity for methylene blue

In this work, the average particle size of metal organic framework (MOF) MIL-100(Fe) was modulated notably from 100 nm to 20 μm by changing the valence state of iron in iron sources and the amount of HF during hydrothermal reactions. The sorption capacity of MIL-100(Fe) for methylene blue (MB) increases with the particle size, and the maximum sorption capacity of the largest particles reached 1105 mg/g, much higher than previous reports on MOFs. The high sorption capacity could be attributed to high surface area and suitable pore structure. Additionally, the particle size determined the adsorption rate. The smaller the particle size, the higher the adsorption rate. The adsorption isotherms were adequately fitted with the Langmuir model and the kinetic data were followed by the pseudo-second-order model. Besides, MIL-100(Fe) possessed good recyclability which can be regenerated by washing with ethanol. These results identified that MIL-100(Fe) exhibited great potential for purification of MB wastewater.