Ultrafast degradation of organic dyes via PMS activation by CNT-loaded MOF-derived Co nanoparticles

Metal-organic frameworks (MOFs) are highly effective in activating peroxymonosulfate (PMS) for pollutant degradation, yet their practical application is limited by nanoparticle aggregation and poor recoverability. To address this, carbon nanotubes (CNTs) were employed as an ideal scaffold to host MOF-derived species. In this study, a Co-MOF@CNTs precursor was converted into a composite of Co nanoparticles embedded in defective porous carbon nanotubes (Co@CNTs-800). The resulting Co@CNTs-800/PMS system exhibited remarkable catalytic activity in the degradation of rhodamine B (RhB), achieving complete degradation within 4 min with a rate constant of 1.025 min⁻¹. The material demonstrated excellent stability across a broad pH range (pH = 4–10) and exhibited high performance in the presence of common inorganic anions (Cl⁻ and NO₃⁻) as well as natural organic matter, with maintained stability over 6 cycles. Quenching assays and electron paramagnetic resonance (EPR) spectroscopy revealed that both free radical (SO₄^•−, ·OH, and O₂^•−) and non-radical (¹O₂ and charge transfer) pathways contribute to the degradation process, with non-radical mechanisms dominated by ¹O₂. The degradation pathway of RhB was elucidated based on intermediates detected by liquid chromatography-mass spectrometry (LC-MS) and density functional theory (DFT) calculations. Additionally, the Co@CNTs-800/PMS system effectively removed other dyes, highlighting its potential for broader applications in advanced oxidation processes for water treatment.