Concise and eco-friendly: Stable anchoring of cobalt nanoparticles embedded in MXene via CaCl2 for boosting degradation of 5-fluorouracil

The development of efficient and stable catalysts for peroxymonosulfate (PMS) activation is essential for the removal of persistent pharmaceutical pollutants such as 5-fluorouracil (5-FU). In this work, a novel, economical, and facile one-step molten salt synthesis strategy is developed to simultaneously etch the MAX phase (Mo 2 TiAlC 2 ) and in-situ anchor multiple cobalt-active species, leading to the direct formation of multi-interfacial Co/Mo-carbide/oxide hybrids. By employing a CaCl 2 /CoCl 2 molten salt system at 800 °C—which acts as both etchant and reaction medium—selective delamination of Al layers is achieved to produce Mo 2 TiC 2 MXene nanosheets, while catalytically active phases (Mo 3 Co 3 C, Co, and Mo 2 C) are generated in situ. Comprehensive characterization confirms the successful construction of abundant heterogeneous interfaces among these phases. The unique multi-interfacial architecture synergistically enhances electron transfer and exposes numerous active sites, thereby enabling highly efficient PMS activation. As a result, the hybrid catalyst exhibits exceptional performance in degrading 5-FU, with high degradation efficiency and rapid reaction kinetics. Radical quenching tests and electron paramagnetic resonance (EPR) analyses reveal that both radical (SO 4 • − , •OH, O 2 • − ) and non-radical ( 1 O 2 ) pathways act synergistically in the degradation process. This study offers a green and efficient “forging” strategy for designing MXene-derived composites with tunable compositions and interfaces. It not only avoids the use of fluorides but also introduces CaCl 2 as a novel molten salt etchant, demonstrating great potential for advanced oxidation processes and other applications.