MOF-derived single-atom catalysts: The next frontier in advanced oxidation for water treatment

Over the last decade, single-atom catalysts (SACs) have emerged as a new frontier in the field of advanced oxidation processes (AOPs), since they allow combining the advantages of homogeneous and heterogeneous catalysts, eventually maximizing the atomic efficiency. Metal-organic frameworks (MOFs), periodic porous structures formed through self-assembly of transition metal cations and organic ligands, are regarded as an ideal precursor for the synthesis of SACs. In this review, the synthetic strategies and characterization methods for MOF-derived SACs are described, with special focus on experimental techniques and theoretical simulations employed to verify the existence of single atoms and metal-binding sites. In addition, applications of these catalysts in water treatment by AOPs and electrochemical AOPs based on the activation of persulfate and H2O2 are discussed, paying attention to reaction mechanisms investigated via DFT calculations. Finally, perspectives and research challenges for future development of MOF-derived SACs as catalysts in AOPs are commented.