Development of a heterogeneous MOF-on-MOF photo-Fenton catalyst for highly efficient tetracycline degradation across a broad pH spectrum

The utilization of MOF-on-MOF heterojunction materials has demonstrated exceptional functional scalability; however, their application in the realm of photocatalytic degradation remains relatively limited. This study focuses on the synthesis of a MOF-on-MOF heterojunction involving the growth of Prussian blue (PB) onto the surface of ZIF-8, with ZIF-8 serving as a seed. The optimized MOF-on-MOF heterostructure catalyst, denoted as PB@ZIF-8, exhibited a degradation efficiency exceeding 98 % across the pH range of 4.0–10 in the Fenton system under sunlight irradiation. Notably, the reaction rate constant in the PB@ZIF-8/H 2 O 2 /Sun system was 0.029 min −1 , which is 2.43 and 2.36 times higher than that of pure PB and ZIF-8. The superior performance of PB@ZIF-8 was attributed to the synergistic effect of PB and ZIF-8 in the MOF-on-MOF composite, which played a pivotal role in the tetracycline degradation process by enhancing light absorption and facilitating the separation of carriers. Furthermore, the PB@ZIF-8 catalyst exhibited exceptional stability, allowing for 5 cycles of recycling while consistently maintaining a degradation efficiency exceeding 97 %. This research not only expands the possibilities for architecting MOF-on-MOF structures but also contributes to the development of heterojunction materials for the removal of emerging pollutants from wastewater.