Ionic liquid-assisted formation of lanthanide metal-organic framework nano/microrods for superefficient removal of Congo red

New lanthanide metal-organic framework(MOF) nano/microrods, [C 4 mim]Cl-Eu-MOF, [C 8 mim]Cl-Eu- MOF and [C 12 mim]Cl-Eu-MOF, were conveniently synthesized via an ionic liquid-assisted hydrothermal method and characterized by means of powder X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FTIR), thermogravimetric analysis(TG) and transmission electron microscopy(TEM). The obtained nano/microrods with low surface areas were efficient for the removal of Congo red(CR) from aqueous solutions. Under the optimum conditions, [C 4 mim]Cl-Eu-MOF with a specific surface area of 5.1 m 2 /g exhibited an ultrahigh adsorption capacity of 2606 mg/g toward CR. Notably, the adsorption efficiency of [C 4 mim]Cl-Eu-MOF for CR via nano/microscale stacking can be directly demonstrated by TEM. In-depth understanding of CR removal by [C 4 mim]Cl-Eu-MOF nano/microrods was also supported by FTIR, Raman spectroscopy and zeta potential analyses.