Enhanced degradation of emerging pollutants in real wastewater via ZIF-derived co-NC modified CN: Mechanism and performance evaluation

In this study, a composite photocatalyst comprising a thin carbon layer and highly dispersed cobalt active sites derived from ZIF-L and modified g-C₃N₄ (CN), was synthesized using a vacuum calcination method. The composite of Co-NC@CN, demonstrated impressive tetracycline (TC) degradation activity (nearly 80%), both in controlled experiments and in real river water conditions. Experimental visualization and characterization results indicated that the carbon layer and the unique cobalt species, with their Co³⁺/Co²⁺ redox capability, enhanced the migration and transfer efficiency of photogenerated carriers, as well as the NC improved TC adsorption. Additionally, free radical capture experiments and electron spin resonance (ESR) confirmed that superoxide radicals (^.O₂⁻), hydroxyl radical (^.OH) and holes (h⁺) are the primary active species involved in the TC degradation process. Further analysis using liquid chromatography mass spectrometry (LC-MS) and diffuse reflectance in situ Fourier-transform infrared spectroscopy (Drifts-FTIR) provided detailed insights into the degradation process and the intermediate products formed. This research offers a promising approach to synthesizing sunlight-driven composite photocatalysts for the treatment of real wastewater.