Novel AgI/MIL-125(Ti) heterojunction for efficient photocatalytic degradation of organic pollutants under visible light: Interfacial electron transfer pathway and degradation mechanism

Photocatalytic degradation of organic pollutants in wastewater driven by solar energy is considered one of the effective means for environmental remediation. MIL-125(Ti) is a three-dimensional porous ordered metal-organic framework with Ti nodes, which has the advantages of porous structure, adjustable pore size, high chemical and thermal stability. However, the application of MIL-125(Ti) for photocatalysis is limited due to its limited light absorption and low carrier separation efficiency. Here, a novel AgI/MIL-125(Ti) composite was prepared by an ion precipitation exchange method to enhance the overcome of the above deficiencies. Characterization analysis reveals that AgI was uniformly loaded on the surface of MIL-125(Ti), forming a dense AgI/MIL-125(Ti) heterojunction. The light response range of AgI/MIL-125(Ti) composites was significantly improved, which promoted the generation of free radicals. In addition, the photogenerated electrons in the conduction band of AgI were transferred to MIL-125(Ti) by ligand-to-metal charge transfer (LMCT) mechanism under visible light, which avoids the recombination of e-h(+) and prolongs the service life of the photocatalyst. Furthermore, as the main active substances, center dot OH and center dot O2- were generated in large quantities on the AgI surface, the presence of Ti3+-Ti4+ valence electron transfer band in the composite, significantly improved the photocatalytic performance. Therefore, the photocatalytic performance of AgI/MIL-125(Ti) composite for gentian violet degradation reached 95.7% in 120 minutes which was higher than that of the single component under visible light.