Preparation of cobalt based metal organic framework ZIF-67 catalyst for activating peroxymonosulfate and its catalytic system for rapid degradation of Rhodamine B and other dyes at high concentrations

Abstract

Persistent organic pollutants pose significant long-term risks to environmental and human health due to their carcinogenic, mutagenic, and teratogenic properties. This study focuses on the efficient activation of peroxymonosulfate (PMS) through the rational design of a cobalt-based metal–organic framework (ZIF-67) catalyst, enabling rapid degradation of high-concentration dye pollutants. By optimizing the molar ratio of 2-methylimidazole (2-MeIM) to Co(NO₃)₂·6H₂O and employing a hydrothermal synthesis method, we fabricated ZIF-67 (4 : 1) with high crystallinity, large specific surface area (1656.68 m² g⁻¹), and stable degradation performance. The ZIF-67 (4 : 1)/PMS system achieved complete degradation of 20 mg L⁻¹ and 100 mg per L Rhodamine B (RhB) within 60 seconds and 6 minutes, respectively, surpassing recent reported efficiencies. The system also maintained high activity over a broad pH range (3–9). Radical quenching experiments and electron paramagnetic resonance (EPR) analysis identified sulfate radicals (˙SO₄⁻₄) and singlet oxygen (¹O₂) as the dominant reactive species. Furthermore, the catalyst exhibited excellent recyclability with no significant loss in activity after five consecutive cycles. This work provides a facile and scalable strategy for preparing highly active cobalt-based catalysts, demonstrating great potential for practical applications in industrial wastewater treatment and environmental remediation.