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<p>Precise modulation of spin states of single-atom catalysts (SACs) offers a promising route to fine-tune peroxide activation behaviors and selectivity toward different oxidation pathways. Here, we report a spin-tunable Fe SAC composed of iron phthalocyanine (FePc) axially coordinated via oxygen bridges (-O-) onto annealed nanodiamond (AND), denoted as FePc-O-AND. The axial oxygen coordination induces a spin transition from high-spin (<i>t</i><sub>2g</sub><sup>5</sup><i>e</i><sub>g</sub><sup>3</sup>) to an intermediate-spin (<i>t</i><sub>2g</sub><sup>4</sup><i>e</i><sub>g</sub><sup>2</sup>) state. This transition generates an unoccupied Fe 3<i>d</i>z<sup>2</sup> orbital that enables oriented electron transfer to peracetic acid (PAA) via hydroxyl oxygen coordination. In situ synchrotron-based Fourier-transform infrared spectroscopy (SR-FTIR) reveals a distinct PAA activation pathway involving inner-sphere complexation and a non-radical electron-transfer mechanism. As a result, the FePc-O-AND/PAA system drives a non-radical electron-transfer pathway with a high reaction rate (2.11 min<sup>−1</sup>), selectively converting phenolic pollutants into high-molecular-weight polyphenolic products (<i>n</i> ≥ 5). Density functional theory (DFT) calculations reveal that axial oxygen coordination in FePc-O-AND enhances PAA adsorption energy (−0.89 eV) and induces a favorable inner-sphere interaction with the hydroxyl oxygen, thereby facilitating effective PAA activation. The FePc-O-AND/PAA system exhibits strong resistance to water matrix interferences and maintains high performance over 130 h of continuous-flow operation. These findings establish axial coordination-mediated spin-state regulation as a powerful strategy for engineering SACs for sustainable water purification and recycling of micropollutants.</p>

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Axial oxygen coordination drives spin-regulated electron transfer in single-atom Fe catalysts for selective pollutant transformation

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年3月30日

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  • Fei Miao,
  • Yantao Wang,
  • Hongyu Zhou,
  • Shuang Zhong,
  • Jingkai Lin,
  • Wen Xu,
  • Xiting Yue,
  • Wei Ren,
  • Hui Zhang,
  • Shaobin Wang,
  • Jitraporn Pimm Vongsvivut,
  • Xiaoguang Duan

摘要

Precise modulation of spin states of single-atom catalysts (SACs) offers a promising route to fine-tune peroxide activation behaviors and selectivity toward different oxidation pathways. Here, we report a spin-tunable Fe SAC composed of iron phthalocyanine (FePc) axially coordinated via oxygen bridges (-O-) onto annealed nanodiamond (AND), denoted as FePc-O-AND. The axial oxygen coordination induces a spin transition from high-spin (t2g5eg3) to an intermediate-spin (t2g4eg2) state. This transition generates an unoccupied Fe 3dz2 orbital that enables oriented electron transfer to peracetic acid (PAA) via hydroxyl oxygen coordination. In situ synchrotron-based Fourier-transform infrared spectroscopy (SR-FTIR) reveals a distinct PAA activation pathway involving inner-sphere complexation and a non-radical electron-transfer mechanism. As a result, the FePc-O-AND/PAA system drives a non-radical electron-transfer pathway with a high reaction rate (2.11 min−1), selectively converting phenolic pollutants into high-molecular-weight polyphenolic products (n ≥ 5). Density functional theory (DFT) calculations reveal that axial oxygen coordination in FePc-O-AND enhances PAA adsorption energy (−0.89 eV) and induces a favorable inner-sphere interaction with the hydroxyl oxygen, thereby facilitating effective PAA activation. The FePc-O-AND/PAA system exhibits strong resistance to water matrix interferences and maintains high performance over 130 h of continuous-flow operation. These findings establish axial coordination-mediated spin-state regulation as a powerful strategy for engineering SACs for sustainable water purification and recycling of micropollutants.