Visible-light-driven photocatalytic degradation of pollutants over Cu-doped NH2-MIL-125(Ti)

In our study, we carried out the first synthesis of new copper-doped titanium-based amine-functionalized metal-organic frameworks (Cu-NH2-MIL-125(Ti)) via an in situ doping method. The as-acquired materials were well distinguished by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma (ICP) emission spectroscopy, N2 adsorption-desorption measurements, UV–vis diffuse reflectance spectroscopy, photoluminescence (PL) spectroscopy, and photoelectrochemical experiments. The Cu-doped NH2-MIL-125(Ti) exhibited a significant improvement in photocatalytic activity compared to undoped NH2-MIL-125(Ti). When Cu was 1.5 wt%, the Cu-doped NH2-MIL-125(Ti) exhibited the greatest photocatalytic activity. The rate constants of the 1.5 wt% Cu-NH2-MIL-125(Ti) to degrade methyl orange (MO) and phenol were determined as 10.4 and 3.4 times as great as those of undoped NH2-MIL-125(Ti), respectively. The improved photocatalytic activity of Cu-NH2-MIL-125(Ti) could be ascribed to the elevated light absorption ability and additional effective charge transportations and separations. Further, the Cu-NH2-MIL-125(Ti) photocatalysts stayed steady following four consecutive cycles. Additional research proved that the holes and hydroxyl radicals were the primary active species in the degradation procedure.