A Novel Co-Based Metal–Organic Cage for Efficient Peroxymonosulfate Activation toward Methylene Blue Degradation: Performance, Mechanism, and Pathway

Metal–organic cages (MOCs), with their unique cavity structures, abundant specific surface areas, and host–guest recognition capabilities, have been consistently demonstrated as catalysts that can significantly accelerate reaction rates and enhance substrate enrichment. Notably, although research has been devoted to the application of MOC in catalysis, studies focusing on the utilization of peroxymonosulfate (PMS) activation for pollutant degradation remain relatively limited. Herein, this study presented the synthesis of a novel cobalt-based metal–organic cage, {Co4(μ4-OCH3)(TBSC)}2L4·2DMF·CH3OH (L = 1,3-adamantanedicarboxylic acid), Ada-MOC, and evaluate its catalytic performance in PMS activation for methylene blue (MB) degradation. The results indicated that the Ada-MOC/PMS system showed a superior MB degradation efficiency of 99.9% within 30 min, with a kapp value 33 times higher than that of the PMS system. Furthermore, the Ada-MOC exhibited high stability and catalytic activity across a broad pH range and under diverse water quality conditions. Mechanistic studies revealed that nonradical pathways such as singlet oxygen (1O2) played a dominant role in the reaction process. Based on LC-TOF-MS analysis combined with DFT calculations, three potential degradation pathways for MB have been proposed. The Ada-MOC/PMS system developed in this research demonstrates considerable potential for practical application in organic wastewater remediation.