Synthesis of three-dimensional porous ZIF-67/Bi2S3 heterojunctions with improved photocatalytic activity under visible-light irradiation

Firstly, Bi2S3 material was prepared by hydrothermal synthesis method, and the ZIF-67/Bi2S3 composite photocatalyst material was obtained by adding different contents of Bi2S3 in the synthesis process of ZIF-67. Three-dimensional porous ZIF-67/Bi2S3 heterojunction has a high specific surface area and provides a large number of reaction sites, which can be fully in contact with organic molecules, thereby improving light capture and photocatalytic reaction activity. The Bi2S3 semiconductor has a bandgap of about 1.3 eV and has strong light absorption in the visible region. ZIF-67 has a band gap of about 1.98 eV, which is not only porous but also has a good band structure. The combination of Bi2S3 and ZIF-67 can not only expand the spectral absorption range, but also ZIF-67 can be used as Bi2S3 carrier, which is conducive to photogenic carrier separation, solving the problem of Bi2S3 easy aggregation, and improving the processing efficiency. The morphology and elemental composition of ZIF-67/Bi2S3 were studied by XRD, SEM and XPS, and the synthesis of ZIF-67/Bi2S3 was successful. The absorption capacity of visible light was studied by UV–Vis DRS, and it was confirmed that ZIF-67/Bi2S3 composite photocatalytic material has extensive absorption of light. The results show that the prepared ZIF-67/Bi2S3-40 % heterojunction has good photocatalytic performance. Under visible light irradiation, the degradation rate of tetracycline hydrochloride (TCH) by ZIF-67/ Bi2S3-40 % was 91.1 % within 90 min, which was 1.25 times and 4.6 times of the absorption efficiency of naked ZIF-67 and Bi2S3, respectively (72.4 % for ZIF-67 and 19.8 % for Bi2S3). Then the valence band and conduction band values of semiconductor materials were calculated by M−S curve, and finally the degradation mechanism of ZIF-67/Bi2S3 composite photocatalyst was deduced.