MOF-derived cobalt@hollow carbon spheres: scalable synthesis and efficient peroxymonosulfate activation for p-chlorophenol degradation

BACKGROUND The design of catalysts, particularly those with industrially practical dimensions, is critical for advancing wastewater treatment. RESULTS We report a scalable strategy that integrates MOF-derived Co active sites into millimeter-sized hollow carbon spheres (HCS) prepared via phase separation of polyacrylonitrile. The resulting Co@HCS combines hierarchical porosity and graphitized shells with confined Co nanoparticles and Co–N–C sites, enabling efficient peroxymonosulfate (PMS) activation. Compared with HCS and Co@ZIF, Co@HCS achieved >80% p -chlorophenol (4-CP; 50 mg L −1 ) removal within 10 min, with activity enhanced by increased Co loading and optimal PMS dosage (0.50 g L −1 ). The catalyst exhibited broad pH adaptability (50.1–90.2% removal at pH 3–9), strong temperature responsiveness and low apparent activation energy (16.3 kJ mol −1 ). Radical quenching and electron paramagnetic resonance confirmed SO 4 •− as the dominant species, while X-ray photoelectron spectroscopy revealed dynamic Co 0 /Co 2+ /Co 3+ cycling sustaining PMS activation. Notably, the millimeter-sized morphology of Co@HCS enabled stable >70% 4-CP removal over 48 h in continuous flow (addressing nanocatalyst drawbacks). CONCLUSION Co@HCS is an efficient, durable and recyclable catalyst. This catalyst combines nanoscale catalytic precision with macroscopic practicality, facilitating the practical application of persulfate-driven advanced oxidation processes and providing a durable and recyclable solution for such processes in continuous-flow water treatment. © 2025 Society of Chemical Industry (SCI).