MOF-derived Fe based catalysts for efficiently Advanced Oxidation Processes: From single atoms to diatomic and nanoparticles

Sub-nanometer catalysts have drawn great attention based on their superior catalytic activity and extensive application in advanced oxidation processes (AOPs). Nonetheless, the precise regulation of the coordination environment and exploration of the peroxymonosulfate (PMS) activation mechanism remain the focus of research. Herein, we report the preparation of Fe catalysts with diverse sizes, including single atoms (SAs), double atoms (DAs), and nanoparticles (NPs) via adjusting the precursor. Sub-nanometric Fe catalysts exhibit a higher catalytic activity for Bisphenol A (BPA) degradation. It is confirmed that the catalytic activity of the Fe diatomic catalysts (Fe2-N/C) is 2.5 times that of the Fe single-atom catalysts (Fe1-N/C) and 8.3 times that of the Fe-nanoparticle-loaded catalysts (FeNP-N/C). Broad pH adaptation ranges and reusability have also been proved. Based on experimental verification and density functional theory, non-free radical pathways dominate the degradation process of BPA, while free radical pathways are in an auxiliary position, accompanied by electron transfer process. It is found that the synergistic effect of Fe2-N6 sites and pyridinic N adsorption centers contribute to the ultra-high catalytic activity of Fe2-N/C. This work opens up an efficient way for single atom catalysts-based advanced oxidation processes for the efficient removal of refractory organic pollutants.