Ligand-effect regulated selective catalytic oxidation of 2-chloroethyl ethyl sulfide in aqueous phase by Keplerate-type molybdenum-oxygen cluster {Mo132}

Abstract

Keplerate-type nano-polyoxometalates {Mo₁₃₂-Ac⁻} and {Mo₁₃₂-SO₄²⁻} were respectively used as catalysts, and H₂O₂ as the oxidant, for the catalytic oxidation of 2-chloroethyl ethyl sulfide (CEES), a simulant of mustard gas, in an aqueous solution. The decontamination conditions were optimized via the single-factor method. Under the optimized conditions, the CEES conversion rates catalyzed by {Mo₁₃₂-Ac⁻} and {Mo₁₃₂-SO₄²⁻} were 98.59% and 99.69%, respectively. After 5 cycles of reuse, both catalysts maintained a CEES conversion rate of over 90% and a selectivity of over 99%. The catalytic decontamination processes of CEES by {Mo₁₃₂-Ac⁻} and {Mo₁₃₂-SO₄²⁻} both followed first-order reaction kinetics, with kinetic constants of 0.39 min⁻¹ and 0.60 min⁻¹, respectively. Compared with {Mo₁₃₂-Ac⁻}, {Mo₁₃₂-SO₄²⁻} with more negative charges exhibited higher catalytic activity, showing a significant ligand effect. By adjusting the amount of the catalyst and H₂O₂, CEES can be selectively catalytically oxidized to low-toxicity 2-chloroethyl ethyl sulfoxide (CEESO).