Isolated Ni–Cu atoms anchored to covalent heptazine frameworks propel continuous Fenton-like catalysis

Abstract

Fabricating highly efficient and recycling-free catalysts for Fenton-like peroxymonosulfate (PMS) activation is crucial for continuous water purification. Herein, active Ni–Cu dual atoms have been successfully isolated in a covalent heptazine framework (CHF), identified by HAADF-STEM and XAS. The optimal Bpy-CHF-NiCu_2/1 catalyst not only showed excellent performance in activating PMS for the degradation of sulfamethoxazole (SMX) but also effectively prevented the leaching of metal ions after the strong coordination bonding. Through comprehensive experimental analysis conducted under diverse anions, water bodies, and pollutant conditions, Bpy-CHF-NiCu_2/1 exhibited noteworthy environmental adaptability. To address the challenge of recovering powdered catalysts, Bpy-CHF-NiCu_2/1 was loaded onto PVDF membranes and implemented in a continuous flow reaction unit. Following 60 h of continuous operation, 95% of SMX could be purified. Additionally, the production of active species such as O₂˙⁻, ¹O₂, electrons, and HVMO in this activation system was well verified. Finally, combining LC-MS with DFT calculations, we proposed a plausible mechanism for the Bpy-CHF-NiCu_2/1/PMS system in degrading SMX and evaluated the toxicity of its degradation products. This research introduces a novel approach for developing catalysts with enhanced environmental resilience and stability.