Enhanced performance of hierarchical porous HKUST-1/g-C3N4 heterostructure in the degradation of antibiotics with and without light

Currently, the advanced oxidation processes (AOPs) for water treatment are limited by the demand on externally supplied oxidants or illumination. To overcome these constraints, a series of micro-nano-composites composed of a copper-based metal–organic framework 'HKUST-1' and graphitic carbon nitride (g-C₃N₄) nanosheets, were designed and synthesized via electrostatic self-assembly, hydrothermal treatment and decarboxylation. These hierarchical porous catalysts (HP-HKUST-1/g-C₃N₄) exhibit outstanding characteristics, particularly, in the degradation of Tetracycline Hydrochloride (TCH) under either total darkness or visible illumination. Experimental results demonstrate that TCH can be effectively degraded without externally supplied oxidant. Under dark conditions, 30 mg of the catalyst removed 99.92% of 50 mL 50 mg·L⁻¹ TCH in 30 min; under visible light, 99.95% degradation was achieved in just 20 min. The exceptional performance is attributed to high Cu(I) content which offer strong reducing power to activate O₂ to generate H₂O₂. Additionally, photoexcited electrons in g-C₃N₄ transfer to HKUST-1 via heterojunctions, which suppresses the recombination of electron-hole pairs in g-C₃N₄ and supplies extra electrons for the O₂ reduction in HKUST-1. This study not only presents ideas for designing highly efficient catalysts with self-produced H₂O₂ by activating O₂, but also proposes a practical pathway towards the development of AOPs for wastewater treatment.