Peroxymonosulfate activated M-MOF-74 (M = Co, Fe, Ni) visible light photocatalysts for methylene blue degradation enhancement

Persulphate-based advanced oxidation technology efficiently and cost-effectively removes organic dyes from water but designing stable photocatalytic systems and understanding their reaction mechanisms remain key challenges. Metal–organic frameworks (MOFs) have attracted considerable research attention for degrading organic pollutants owing to their high porosity, tunable structure, and ease of modification. In this study, a series of M-MOF-74 (M = Co, Fe, Ni) photocatalysts are synthesized by a hydrothermal method for methylene blue (MB) degradation. Among them, the Co-MOF-74 photocatalytic synergetic peroxymonosulfate system exhibits high catalytic activity after 30 min of visible light irradiation. MB degradation efficiency reaches 94.8%, and the reaction rate constant is 0.210 min−1, which is approximately 19.44 times higher than the reaction rate constant of the original Co-MOF-74. Compared with Fe-MOF-74 and Ni-MOF-74, Co-MOF-74 exhibits better photocatalytic performance due to the dynamic changes in the valence state of cobalt, which more effectively facilitate the activation of PMS. In addition, this study analyses the possible degradation pathways of MB in water and toxicological evaluations of intermediate products, providing new insights for the effective removal of dyes in water.