Biologically inspired Co-MOF as catalase mimics with an unexpected ROS production ability for the efficient removal of organic dyes

Developing an efficient advanced oxidation technology is of great significance for water treatment and environmental protection. Here, inspired by the structure and feature of coenzyme B12 in natural enzymes (cleavage of Co-C bond triggers the generation of radical), a Co based metal-organic framework (Co-MOF) with catalase-mimicking activity was synthesized and applied in the degradation of organic dyes. Firstly, Co-MOF nanozyme was fabricated via the coordination self-assembly strategy at room temperature. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive scanning (EDS), powder X-ray diffraction (PXRD), and Fourier transform infrared spectroscopy (FTIR) were used to characterize the morphology and structure. The results showed that the obtained Co-MOF nanozyme was rhombic dodecahedral morphology with a size of ~ 500nm and excellent crystallinity. The enzymatic experiments proved that such nanozyme possessed a single catalase-like activity. Further research results demonstrated that Co-MOF-based degradation process of acid fuchsin (AF) or crystal violet (CV) had excellent pH adaptability (pH > 5.0). Unexpectedly, an ultra-high catalytic degradation rate (211.35min-1 g-1 L) was successfully achieved in the catalytic degradation of AF, and it was approximately 5∼200 times of the previous optimal nanozyme or catalysts. In complex matrices and real wastewater, this catalytic process could still maintain degradation efficiency above 90% or even higher within 5minutes, proving its excellent stability and adaptability. The results of radical and electron quenching experiments, electron paramagnetic resonance (EPR), and electrochemical analysis demonstrated that the excellent catalytic degradation performance was attributed to the generation of reactive oxygen species (ROS) (∙O2 was the main contributor) and the existence of electron transfer. In summary, this new catalytic property endows Co-MOF nanozyme with considerable potential for dye degradation, extending the application scope of catalase mimics.