In Situ Active Site-Engineered Z-Scheme CMCN/Co3O4-ZIF-8 Heterostructure for Efficient Tetracycline Degradation

Antibiotic contamination poses environmental risks and requires efficient degradation technologies. Herein, a Z-scheme heterostructured photocatalyst (CMCN/Co3O4-ZIF-8) was constructed by thermally coupling precursor-modified graphitic carbon nitride (CMCN) with metal-organic framework (MOF) derivative (Co3O4-ZIF-8) for tetracycline degradation. Temperature-regulated pyrolysis of ZnCo-MOF afforded Co3O4-ZIF-8 with in situ-formed Co3O4 active sites and a porous framework. CMCN/Co3O4-ZIF-8 heterointerface promoted charge separation and migration via interfacial electric field and energy gradient, enabling Z-scheme charge-transfer pathway that retained highly reductive electrons on Co3O4-ZIF-8 and strongly oxidative holes on CMCN. The Co2+/Co3+ redox cycle in Co3O4-ZIF-8 further facilitated interfacial electron transfer and O2 activation. Superoxide radicals and oxidative holes participated in tetracycline degradation, achieving a degradation efficiency of 86.88%. LC-MS analysis revealed major tetracycline degradation pathways, and toxicity evaluation indicated reduced toxicity of most intermediates. This study guided catalyst design by integrating in situ active site formation and Z-scheme charge-transfer pathway for antibiotic removal.