Biochar-mediated carbon nitride and covalent organic framework photocatalyst for enhanced tetracycline degradation†

The accumulation of tetracycline (TC) poses a significant challenge to human health and ecological systems. Photocatalytic degradation of TC has been a focus of research, heterojunctions receiving particular attention due to their superior charge separation and transfer properties. This study explores the structural characteristics of heterojunctions and their efficacy in degrading TC in aqueous solutions. We synthesized various combinations of biochar (BC), carbon nitride (CN), and covalent organic frameworks (COF) to form heterojunctions and characterized their morphological, structural, and optical properties using SEM, XRD, XPS, and UV-Vis DRS. These analyses helped elucidate the mechanisms underlying TC degradation. The CN₁₀/COF₂-12, synthesized in situ, showed significantly improved degradation efficiency, outperforming CN-10 and COF-2 by factors of 2.02 and 1.96, respectively. Furthermore, the all-solid-state Z-scheme heterojunction photocatalyst BC₁₀–CN₁₀/COF₂-22, in which BC serves as the electron mediator, achieved a 3.13-fold increase in TC degradation compared to BC₁₀–CN₁₀-20. The BC-mediated all-solid-state Z-scheme heterojunction effectively facilitated the separation and transfer of photogenerated electron–hole pairs. This study combines the advantages of CN, COF, and BC, thereby providing a novel approach to the development of high-performance photocatalysts.