Synthesis of S-type heterostructure π-COF for photocatalytic tetracycline degradation

Photocatalytic oxidation is a promising technology for wastewater treatment. It is a more desirable method than other conventional wastewater treatment approaches due to its low cost, environmental friendly, and capability to completely degrade pollutants into environmentally safe products under appropriate conditions. Among some photocatalysts, covalent organic frameworks with high photoactivity are recognized as stable and feasible materials for this purpose. In this work, highly-effective photocatalyst of S-type heterostructure π-COF was successfully synthesized by using ultrasonic delamination treatment sp2c-COF nanosheets (sp2c-NS) and py-NH2-COF nanosheets (Py-NH2-NS) via a secondary solvent heating method. The preparation was initiated by synthesizing sp2c-COF and py-NH2-COF successfully adopting pyrene templates by solvothermal method. The study focused on physicochemical characterization and photocatalytic activity of π-COF. The photocatalytic ability of π-COF was carried out to degrade tetracycline under visible light. The results indicate that π-COF not only shows excellent photocatalytic activity for tetracycline degradation of 94.8 % at 90 min under visible light illumination, but also has good photocatalytic degradation performance at wide initial pH values, coexisting ions, and actual water sources. Surprisingly, it has excellent stability and recyclability, it can afford high oxidative degradation (87.3 %) even after 5 successive recycles. The degradation mechanism was discussed by various methods such as active species trapping experiment, electron paramagnetic resonance determination and related electrochemical analysis. In addition, the main degradation intermediate products and the possible pathways of TC degradation were detected and proposed according to LC − MS technology. This work provided a new strategy for the preparation of hetero-structured COF which could be served as an advantageous photocatalyst for the treatment of pharmaceutical industry wastewater.