Selective Singlet Oxygen Generation over a Silver-Porphyrin Single-Atom-Site Catalyst for Ultrafast Sulfide...

The selective oxidation of sulfides to sulfoxides represents a fundamental transformation in synthetic and pharmaceutical chemistry, yet most catalytic systems require harsh conditions or long reaction times. Herein, we report a silver-porphyrin single-atom-site catalyst (Ag-TMPP; TMPPH₂ = tetrakis(4-methylphenyl)porphyrin) that enables ultrafast photooxidation of sulfides under mild conditions. Ag-TMPP is readily obtained by a simple solution-phase self-assembly of AgNO₃ and TMPPH₂, affording a well-ordered three-dimensional framework stabilized by C─H···π interactions. The catalyst achieves nearly quantitative conversion of methyl phenyl sulfide to sulfoxide within 15 min, delivering a turnover frequency of 3112 h^-1-among the highest reported for heterogeneous metal-based systems. It exhibits excellent recyclability and broad substrate tolerance, efficiently oxidizing both aryl and alkyl sulfides. Mechanistic investigations supported by electron paramagnetic resonance (EPR) spectroscopy and density functional theory (DFT) calculations reveal that the exceptional performance originates from the highly selective generation of singlet oxygen (¹O₂), whereas other metalloporphyrins (M = Cu, Co, Zn etc.) favor competing reactive oxygen species. This study provides an accessible and efficient strategy for harnessing ¹O₂ in photooxidation catalysis.