Single-Atom Iron with Fe–S ₂ O ₂ Structure as an Amphiphilic Catalyst for Enhanced Selective Oxidation of C–H Bonds

Developing highly efficient Fe-based single-atom catalysts (SACs) for the selective oxidation of C–H bonds to produce value-added aromatic ketones under mild conditions is still challenging. Herein, the construction of amphiphilic Fe SACs with electron-deficient Fe–S 2 O 2 structure supported on porous S-doped lignin-derived carbon (Fe 1 /SLC) was achieved using a ball milling combined with an impregnation method. Due to the synergistic interaction between electron-deficient Fe–S 2 O 2 sites and ethylbenzene (EB)–water microinterfacial effects, Fe 1 /SLC markedly enhanced the catalytic activity and acetophenone (AP) selectivity for the selective oxidation of EB to AP under 60 °C for 12 h, obtaining an AP selectivity of 99.1% at 99.0% EB conversion and a high turnover frequency (TOF) of 2422.3 mmol EB g Fe –1 h –1, which were much higher than those of the control catalyts (Fe 1 /LC and Fe NPs /SLC), surpassing most reported catalysts in similar reaction system. The electron-deficient Fe–S 2 O 2 sites were conducive to the cleavage of TBHP to generate 1 O 2, • O 2 –, and • OH radicals, wherein • O 2 – was dominant, while 1 O 2 and • OH performed a secondary role. Meanwhile, the density functional theory calculations revealed that the amphiphilic property of Fe 1 /SLC induced by the C–SO x –C structure heightened the catalytic activity and AP selectivity, which originated from the unique interfacial hydrogen-bonding interactions and adsorption energy gradients. Furthermore, Fe 1 /SLC showed excellent recyclability, long-term storage stability, and satisfactory universality. This work provides a promising strategy to simultaneously improve the catalytic activity and aromatic ketones selectivity of the selective oxidation of C–H bonds.