Highly active ZIF-8 derived CuO@ZnO p-n heterojunction nanostructures for fast visible-light-driven photooxidation of antibiotic waste in water

Abstract

Nanostructured photocatalysts represent an eco-friendly material for photooxidation of toxins beneath light radiation. However, the surface structure and large bandgap energies are the main issues for realizing these photocatalysts under visible-light operation. Herein, we obtain high surface area ZnO by the calcination of solution-prepared zeolitic imidazolate framework (ZIF-8). Also, the ZIF-8 is loaded with Cu precursor to obtain 1.0 − 4.0 wt.% CuO@ZnO p-n heterojunctions by an additional calcination process. The CuO loaded on derived ZnO fashioned a mesoporous texture with an extreme surface area of 1485 m2 g‒1. The introduction of CuO to ZnO exposed a broader light absorption and bandgap reduction to 2.63 eV from 3.43 eV for ZnO and a significant increase of the surface area to 1665 m2 g‒1 for the 3.0 wt.% CuO-loaded ZnO. The fabricated CuO@ZnO employed for tetracycline's (TC) photooxidation, as an antibiotic target in water systems. The optimal 3.0 wt.% CuO@ZnO performed a complete TC photooxidation within 45 min with an oxidation rate of 113.5 × 10−3 min−1 at a dose of 1.5 gL−1. This heterojunction exhibited exceptional recyclability for five cycles. The high activity is regarded to the extreme surface area and the migrated photoinduced charges within the CuO@ZnO.