Unveiling the fundamental understanding of two dimensional π-conjugated FeN4+4 sites for boosting peroxymonosulfate activation

Abstract

The absence of periodic structures and uncertainty concerning active sites in traditional single-atom catalysts (SACs) consistently impede the understanding of the coordination environment and its impact on the peroxymonosulfate (PMS) activation mechanism. In this study, we develop well-defined FeN₄₊₄ active-site configurations featuring robust and ordered N-coordinated Fe single-atomic centers within fully π-conjugated polyphthalocyanine frameworks (CPFs). CPF–FeN₄₊₄ functions as an outstanding PMS activator, exhibiting remarkable efficiency in the degradation of bisphenol A (BPA) with a rate constant of 1.87 min⁻¹, surpassing the majority of state-of-the-art SAC-based PMS systems. Mechanistic scrutiny unveils heightened chemisorption and electron transfer dynamics between PMS and CPF–FeN₄₊₄, facilitating a ¹O₂-dominated selective oxidation pathway. The distinctive FeN₄₊₄ active sites, integrated into π-conjugated frameworks, expedite S–O bond cleavage in PMS, thereby reducing the energy barrier for the formation of *HSO₃ and *O₂ (¹O₂ precursors). The charge redistribution in CPF–FeN₄₊₄ engenders a dual-pump-driven, electron-fast shuttle path, involving electron-rich Fe centers and electron-poor C surrounding adjacent benzene rings, ensuring the continuous production of ¹O₂. This study not only delineates precise active sites at the atomic level for PMS activation but also advances the evolution of a highly promising catalytic oxidation system tailored for practical environmental purification.