Morphology-control of metal-organic framework crystal for effective removal of dyes from water

Highlights: • MIL-101(Cr) with different morphologies was synthesized. • Changing reaction temperature and cooling rate can control MOF morphology. • The maximum adsorption capacity of 150@MIL-101 reach 420.2 mg g⁻¹. • The adsorption equilibrium of meso-MIL-101 was achieved in 30 min. -- Abstract: Metal-organic frameworks (MOFs) MIL-101(Cr) crystal with different morphologies was prepared by solvothermal method through changing the reaction temperature and cooling rate. Spherical MIL-101(Cr) (150@MIL-101) was prepared at 150 °C, and Octahedral MIL-101(Cr) (180@MIL-101 and 220@MIL-101) were obtained at 180 and 220 °C, respectively. Mesoporous MIL-101(Cr) (meso-MIL-101) was synthesized through controlling the cooling rate. Among the four MIL-101(Cr), the 150@MIL-101 possessed the largest specific surface area (3020 m² g⁻¹), pore volume (1.41 cm³ g⁻¹) and adsorption capacity for organic dyes, while the meso-MIL-101 had the fastest adsorption rate. The maximum adsorption capacity of methyl orange (MO) on the 150@MIL-101 can reach 420.2 mg g⁻¹, superior to many adsorbents reported in the literatures. The results demonstrate that the methods of changing the reaction temperature and cooling rate can transform MOFs morphology, which improve the adsorption performances of MOFs.