In situ fluorine migration in ZIF-67/F-TiO2 Z-type heterojunction and its photocatalytic degradation mechanism of tetracycline hydrochloride

Abstract

The advancement of photocatalytic technology depends on the creation of effective photocatalysts. In this research, a series of ZIF-67/F-TiO2 composite catalysts with various ZIF-67 content were made using a straightforward hydrothermal approach, and their photocatalytic performance was examined. The analysis of element content and crystal structure of the composites showed that F element in TiOF2/TiO2 migrated during the hydrothermal process, resulting in F-TiO2 with special surface fluorine. The existence of special surface fluorine can act as electron trapping sites to promote oxygen adsorption and accelerate the hole migration to the surface of TiO2, to achieve better electron hole separation efficiency and enhance photocatalytic activity. Density functional theory (DFT) calculations verified the formation of heterojunction. Tetracycline hydrochloride (TCH) was broken down by ZIF-67/F-TiO2 composites with different mass ratios under simulated sunlight to determine their photocatalytic effectiveness. The results indicated that ZIF-67/F-TiO2 composite photocatalyst with 10 % ZIF-67 content had the highest removal efficiency (87 %) of tetracycline hydrochloride (20 mg/L) within 1 h. The following are the causes of the increased photocatalytic activity of ZIF-67/F-TiO2 composites: More electron capture sites are made available by the surface F produced by in situ F migration, which also encourages photogenerated electron-hole separation. A Z-type heterojunction, on the other hand, lengthens the lifetime of photogenerated carriers. This study introduces a fresh idea: F-TiO2 with special surface fluorine was prepared by in situ F migration, and the photocatalytic degradation of wastewater containing tetracycline hydrochloride by F-TiO2 composites was investigated.