La-doped MIL-88B(Fe)-NH: a mixed-metal-organic framework photocatalyst for highly efficient reduction of Cr(vi) in an aqueous solution.

With the aim to resolve the problem of water pollution, we herein propose a new photocatalyst based on metal-organic frameworks (MOFs), called La-doped MIL-88B(Fe)-NH (MIL-88B((1 - )Fe/La)-NH), which was designed and employed for the photocatalytic reduction of Cr(vi) in aqueous solutions. MIL-88B((1-)Fe/La)-NH materials with different values were synthesized a one-pot solvothermal method. Their characteristics were investigated using various techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), Brunauer-Emmett-Teller (BET) analysis, Fourier-transform infrared (FT-IR) spectroscopy and ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS). We found that compared to pristine MIL-88B(Fe)-NH with a photocatalytic efficiency of 67.08, MIL-88B((1 - )Fe/La)-NH materials with = 0.010, 0.025 and 0.050 exhibit excellent photocatalytic efficiencies reaching 88.21, 81.19 and 80.26%, respectively, after only 30 minutes of irradiation at a small catalyst dosage of 0.2 g L. These La-doped MIL-88B(Fe)-NH photocatalysts can work well under mild conditions (pH = 6). Furthermore, they are robust-can be recycled for at least four consecutive runs without any activity loss. This novel material is promising for the photocatalytic degradation of pollutants.