Ethanol-assisted mechanochemical synthesis of MOF-199-derived CuOx/carbon composites with tunable copper species for photo-enhanced Fenton-like dye degradation

Abstract

Metal–organic frameworks (MOFs) are attractive precursors for constructing porous metal–carbon composites, yet their conventional solvothermal synthesis relies heavily on toxic solvents and energy-intensive conditions. Herein, we develop an ethanol-assisted mechanochemical strategy for the rapid and solvent-minimal synthesis of MOF-199, followed by controlled pyrolysis to obtain MOF-199-derived CuO_x/carbon composites with tunable copper species. Electron microscopy reveals that copper-based nanoparticles are uniformly embedded and confined within the porous carbon matrix. X-ray diffraction and X-ray photoelectron spectroscopy confirm the coexistence of Cu, Cu₂O, and CuO in the as-prepared materials, revealing distinct bulk and surface copper speciation that depends on pyrolysis temperature. Among the obtained catalysts, the sample CuO_x/C-700, which was pyrolysed at 700 °C, shows a significant Cu₂O/CuO phase and demonstrates outstanding performance as a visible-light-enhanced Fenton-like catalyst for rhodamine B degradation in the presence of H₂O₂. It achieves 98.6% removal within 180 min at near-neutral pH, significantly outperforming the reaction in the dark. Radical scavenging experiments identify ˙OH as the dominant reactive species, while LC-HRMS analysis reveals progressive deethylation and ring-opening degradation pathways. Furthermore, the catalyst demonstrates good recyclability, is applicable to various dyes, and has low copper leaching, highlighting its structural robustness. This work establishes a green and scalable mechanochemical route to engineer MOF-derived Cu-based photo-Fenton-like catalysts, where controlled copper speciation and nanoscale confinement enhance the efficiency of wastewater remediation.