Oxygen-containing functional groups coupled Fe sites of FeOx/OAC overcome the trade-off between desulfurization activity and regeneration performance.

The introduction of metal oxides is a general strategy to enhance the SO2 removal activity of carbon materials. However, the formation of stable metal sulfates poses challenges to low-temperature thermal regeneration of metal active sites. To overcome the trade-off between activity and regenerability, we developed oxygen-containing functional groups (OCFGs) coupled Fe sites on oxygen-functionalized activated carbon supported iron oxides (FeOx/OAC). Specifically, -COOH and C=O/C-OH groups coupled Fe sites were constructed to enhance SO2 oxidation and Fe2(SO4)3 decomposition, respectively. Comprehensive characterization and DFT calculations revealed that -COOH groups mediated Fe3+ anchoring via Fe-O-C coordination, enhancing electron transfer efficiency to generate oxygen vacancies for SO2 oxidation. C=O/C-OH groups coupled with Fe sites reduced the Fe2(SO4)3 decomposition energy from 153.67 to 128.26 kJ mol-1via Fe-S bond elongation, enabling efficient regeneration. The optimized FeOx/OAC exhibited a 75 % increase in SO2 capacity (from 40.88 to 71.62 mg/g) and a reduced regeneration temperature (from 500 to 400 °C). Over five desulfurization-regeneration (S-R) cycles, FeOx/OAC maintained high SO2 capacity and recovered over 90 % of sulfur resources. This study presents a synergistic experimental-theoretical framework, which delves into the intricate mechanisms underpinning the enhanced desulfurization and regeneration performances via the interaction effect between OCFGs and Fe sites.