Boron nitride quantum dots supported hollow NH2-MIL-125 drive photo-Fenton-PMS system for photocatalytic tetracycline degradation: Contribution of tannic acid etching.

NH2-MIL-125(Ti) materials had great potential for photocatalytic applications but had low activity due to exciton effect and narrow absorption range of visible light. The surface oxygen-containing negative functional groups of boron nitride quantum dots (BNQDs) could overcome these defects, but due to the low load capacity, a higher specific surface area of the substrate was usually required. In this paper, a hollow Ti-MOF material was developed by etching technology. The hollow structure formed by tannic acid etching broadened the absorption range of visable light and provided more alternative surfaces for loading BNQDs. The 85.2% of high tetracycline (TC) removal efficiency for the best sample (BNQDs-5@20-Ti-MOF + PMS) was obtained, which was about 56.8 and 1.9 times of the 20-Ti-MOF and BNQDs-5@20-Ti-MOF, respectively. BNQDs-5@20-Ti-MOF + PMS system showed a great TC degradation efficiency in a wide pH range (pH = 5-9). In addition, reaction temperature and the inorganic ions did not show significant inhibition effect for TC removal. Both free radical and non-free radical pathways were involved in the TC degration by BNQDs-5@20-Ti-MOF + PMS system, among which O2•- and 1O2 played the key roles. Interestingly, multiple 1O2 production paths contributed to the high efficiency and stability of BNQDs-5@20-Ti-MOF + PMS system. This study revealed a reasonable combination of Ti-MOF and BNQDs, which provided a new efficient photocatalyst for environmental remediation.