MOF-5-derived ZnO–C nanoparticles combined with α-MnO2 for the efficient degradation of tetracycline under visible light

A multifunctional α-MnO2/ZnO–C (MZ) Z-scheme photocatalyst was synthesized by the suit-growth of α-MnO2 on the surface of MOF-5 and pyrolysis of the organic components under certain conditions. The obtained photocatalysts were characterized and the photocatalytic activity was investigated by degrading tetracycline (TC). Especially, the composite with a 15% mass ratio of α-MnO2 (15-MZ) exhibited the best photocatalytic activity for tetracycline under visible light irradiation and the degradation efficiency for TC reached 96.69% within 60 min. The doping of the C element in the ZnO crystal structure formed an intermediate energy level to narrow the band gap of ZnO, which was beneficial for visible light absorption. Also, the construction of a binary synergistic system between ZnO and α-MnO2 resulted in the extension of the light response range and accelerated the transfer of photogenerated carriers. The tests showed that h+, 1O2, •O2−, and •OH were the main active species and played leading roles in the degradation process. Additionally, the residual C species as an electron-transfer medium were conducive to constructing the Z-scheme heterojunction between ZnO–C and α-MnO2, which provides an interesting approach for designing visible light responsive photocatalysts.