Enhanced photocatalytic degradation of tetracycline over carbon quantum dot-decorated MIL-101(Fe) composite

Carbon quantum dots (CQDs) were deposited on the surface of MIL101(Fe) by using hydrother-mal method to obtain CQDs/MIL101(Fe) composite. The prepared composite was characterized by X-ray diffusion (XRD) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-Vis diffuse reflec-tion spectrum. The photocatalytic performance of CQDs/MIL101(Fe) composite was evaluated by photocatalytic degradation of tetracycline (TC) under visible-light irradiation. The mechanism of enhanced photocatalytic performance was discussed. The characterization results reveal that CQDs is anchored tightly on the surface of MIL101(Fe) to form the composite catalyst. The results of photocatalytic degradation experiment confirm that CQDs/MIL101(Fe) possess excellent photo -catalytic activity and stability for TC degradation. The CM100 with optimum CQDs-to-MIL101(Fe) rate shows the highest photocatalytic activity with TC degradation efficiency up to 81%. The reac-tion rate constant for CM100 is 0.01177 min-1, which is 5.8 times as high as that of pure MIL101(Fe). The results of transient photocurrent response and electrochemical impedance indicate that the improvement of photocatalytic performance of the CQDs/MIL101(Fe) composites is mainly due to the introduction of CQDs, which greatly promotes the separation of photo-generated elec-tron-hole pairs. The result of radical trapping experiment confirms that superoxide radical is the main active species in photocatalytic reaction, followed by photo-generated holes.