Degradation of organic contaminants by peroxymonosulfate activated with zeolitic imidazolate framework-based catalysts: performances, mechanisms and stability

For the past few years, sulfate radical-based advanced oxidation processes (SR-AOPs) have been developed rapidly due to their unique advantages for the degradation of organic contaminants. Zeolitic imidazolate framework (ZIF)-based materials have been considered to be potential catalysts to activate peroxymonosulfate (PMS) for the generation of SO4-. ZIFs are constructed from tetrahedrally coordinated transition metal (M) ions (Zn, Co cation) linked by organic imidazole (Im) units and possess similar structures to conventional aluminosilicate zeolites, where M occupies the position of silicon and the role of oxygen is substituted by Im. ZIFs have high thermal stability and chemical robustness and can be used in many common solvents. Besides, ZIFs have tailorable pore sizes and structures for modification into ideal composite catalysts. Therefore, it is necessary to systematically examine the recent advances of PMS activation on ZIF-based catalysts for the removal of organic contaminants. This review discussed the recent progress on ZIF-based catalysts for PMS activation. Firstly, the applications of ZIF-based catalysts for the removal of contaminants are reviewed. Secondly, the different mechanisms (including radical pathways and non-radical pathways) of PMS activation by pristine ZIFs, ZIF composites and ZIF derivatives are elucidated respectively. Particular emphasis is given to the influence of structure on catalytic activity. Finally, some challenges existing in ZIF/PMS systems are pointed out and the possible research directions are proposed. This review aims to provide novel insight for the application of ZIF-based materials in PMS activation and propose a deeper understanding of ZIF-based materials.