Preparation and photocatalytic performance of AgI/NH 2 -UiO-66(Zr) heterojunction

The development of visible-light-responsive metal organic framework materials (MOFs) heterojunctions is expected to make efficient use of solar energy for catalytic degradation/detoxification of environmental pollutants. Using zircomiun tetrachloride (ZrCl4) and 2-aminoterephthalic acid (2-ATA) as raw materials, NH2-UiO-66(Zr) was prepared as MOFs substrate by solvothermal method. A series of AgI/NH2-UiO-66(Zr) heterojunction composites were prepared by counter ion deposition method. The materials were characterized by XRD, BET, TEM, UV-Vis DRS, FT-IR, TGA and photoelectrochemical tests. Taking Cr(VI) as a model pollutant, the photocatalytic performance of the composite was studied under visible light and various factors were also investigated, including pH, initial Cr(VI) concentration, catalyst loading amount, type and concentration of trapping agent. It is found that 20% AgI/NH2-UiO-66(Zr) displays optimal photocatalytic performance. After 120 min of visible light irradiation, the Cr(VI) reduction efficiency is 97.8%, which is much higher than that of naked AgI and NH2-UiO-66(Zr). The fitted first-order kinetic constant k is 7.9 and 7.4 times that in the AgI and NH2-UiO-66(Zr) systems, respectively. In addition, the catalyst has good cyclic stability. After 5 cycles, the reduction rate of Cr(VI) still remained at about 90%.