Porous carbon nitride/mixed-valent MIL-53(Fe) heterojunctions for the efficient photo-Fenton degradation of highly concentrated tetracycline hydrochloride

The application of Fe-based metal-organic frameworks in photo-Fenton antibiotic degradation is limited by the low charge separation efficiency and slow Fe 3+ /Fe 2+ transition. In this study, a novel Z -scheme porous carbon nitride/mixed-valent MIL-53(Fe) (KCM-20) heterojunction photocatalyst was successfully constructed for degradation of high concentration tetracycline. On the one hand, the Z -scheme heterojunctions system is conducive to the rapid separation of photogenerated electron-hole pairs. On the other hand, the cyclic conversion of Fe 3+ /Fe 2+ in the MIL-53(Fe) photo-Fenton system can be accelerated. The KCM-20 showed the highest degradation efficiency for tetracycline. The KCM-20/light/H 2 O 2 system degraded more than 93 % of tetracycline (150 mg·L −1 ) within 75 min and exhibited the highest degradation kinetic constant, which is 8.0 and 2.4 times higher than those of carbon nitride and MIL-53(Fe), respectively. Its excellent catalytic performance can be attributed to the efficient synergy between photocatalytic reaction and Fenton reaction, producing more active species for tetracycline degradation. EPR and activity capture experiments indicate that ·O− 2, ·OH and h + are the main active species for tetracycline degradation. By analyzing the intermediate products, three degradation pathways for tetracycline were proposed. This work provides a new pathway for the preparation of efficient and cost-effective photocatalysts for the degradation of organic pollutants.