Hollow Cu-Co/N-doped carbon spheres derived from ZIFs as an efficient catalyst for peroxymonosulfate activation

Zeolitic imidazolate framework (ZIF)-derived carbons have been considered promising catalysts for the degradation of organics in water through peroxymonosulfate (PMS)-based oxidation processes. The construction of hierarchical hollow, porous structures while retaining the properties of ZIF-derived carbons is highly desirable for a catalyst but remains an arduous challenge. Herein, ZIF-67 (Co(mim)2, mim = 2-methylimidazolate) derived carbon with hollow, porous structures is achieved by pyrolysis of architectures consisting of polystyrene cores and ZIFs shells. The properties of the resulting sample are characterized, and its superior performance for 4-nitrophenol (4-NP) degradation via PMS activation is investigated. Factors that affect 4-NP degradation are examined, including the catalyst and PMS dose, solution pH, temperature and 4-NP concentration. Moreover, the catalyst can be easily separated from the solution with a magnet and has good stability and reusability. Electron paramagnetic resonance spectroscopy (EPR) and radical scavenger tests indicate that SO4− is the main reactive species participating in 4-NP degradation. This work provides a new prospect for the design of high-performance ZIF-derived carbon catalysts for PMS-based oxidation processes.