Asymmetric Coordination Modulating Co Spin State for Peroxymonosulfate Activation to Accelerate 1 O 2 Generation

Abstract Singlet oxygen ( 1 O 2 ) has received extensive attention for the selective degradation of emerging contaminants. However, how to efficiently generate 1 O 2 by modulating the asymmetric structure and electron spin state of catalyst remains a challenge. Herein, an asymmetric Fe─S─Co structured catalyst (Co‐Fe 3 S 4 ) is designed by in situ substitution of Fe III Td strategy. The strong interaction in the asymmetric structure induces a low‐spin state ( e : ↑↓ , ↑↓ , t 2 : ↑↓ , _, _) at d‐orbital of Co sites, shifting the d‐band center closer to the Fermi level and elevating the antibonding states, which is beneficial for the adsorption of peroxymonosulfate (PMS). The catalyst accelerates 1 O 2 generation by PMS activation, achieving 100% removal of acetaminophen in pharmaceutical wastewater in 8 min with a high K‐value of 112 min⁻¹ M⁻¹. Experiments and DFT calculations reveal that the spin state of the generated *O 2 (from the S─O bond cleavage in HSO 5 − ) is reduced by electron reversal ( ↓ to ↑ ) or pairing ( ↑ , ↑ to ↑↓ , _) in the 2p (2p x and 2p y ) orbitals of the O─O anti‐π bond (π*), resulting in the 1 O 2 generation. This work presents an approach for regulating the spin state using an asymmetric structure and offers a broader perspective on the generation mechanism of 1 O 2 .