Construction of hollow ZnO/Mn-ZIF-67 heterojunction photocatalysts: enhanced photocatalytic performance and mechanistic insight

Thanks to the unique structure and properties of MOFs, a well-designed novel hollow ZnO/Mn-ZIF-67 composite photocatalyst was synthesized by a facile sonocrystallization approach successfully. The hollow ZnO/Mn-ZIF-67 composites exhibited higher photocatalytic activity in degrading Bismarck brown R than pure hollow ZnO spheres and Mn-ZIF-67. The optimal ZnO/Mn0.5-ZIF-67 showed the highest catalytic activity with 89.5% Bismarck brown R removal within 100 min. The improved photocatalytic activity of the composites could be mainly attributed to effective photogenerated charge separation and transfer through the coupled Z-scheme heterojunction between hollow ZnO spheres and Mn-ZIF-67. The composite photocatalyst exhibited obviously good stability and recyclability after recycling 4 times. Finally, a possible Z-scheme electron transfer mechanism was proposed based on the active radical trapping experiments and ESR which could explain the improved photocatalytic performance of the photocatalytic system. This work provides a promising approach to construct a direct Z-scheme heterojunction for the degradation of environmental pollutants.