Tuning the redox activity of polyoxometalate by central atom for high-efficient desulfurization

The efficient removal of hydrogen sulfide (H₂S) is of great importance for various industrial processes such as the sewage stream depollution and syngas upgrade. Oxidative desulfurization with polyoxometalates (POMs) has been proved one of the most attractive ways to remove H₂S from the systems, while the role of the central atom in POMs has not been well evaluated. Herein, we demonstrate the desulfurization activity of POMs could be well internally switched by the central atoms. In particular, the S^VI-centered POM of [Himi]SMo, exhibited greatly enhanced desulfurization performance compared to its structural analogs with Ge^IV or P^V as central atoms, with a breakthrough H₂S capacity of 627.0 mg g^-1 compared to 39.5 and 54.9 mg g^-1 respectively, well surpassing state-of-the-art H₂S desulfurizes. In addition, its activity was well maintained at a wide range of temperature (0-50 °C) and pH (4-9). More interestingly, electrochemical re-oxidation of the H₂S laden [Himi]SMo was found much more active than the fresh one, achieving H₂S capacity up to 2174 mg g^-1. Air involved in-situ re-oxidation and S-O metathesis mechanisms were proposed and experimentally evidenced to explain the high capacity. This work opens a new concept for the rational design of POMs in terms of H₂S removal.