Modulating the catalytic properties of decavanadate hybrids using a mixed counterion strategy for selective oxidation of thiophene-based sulfides and detoxification of mustard gas simulant

Abstract

Selective oxidation of sulfides to sulfoxides, especially thiophene-based sulfides, is a challenging task. Herein, we report a mixed counterion strategy in polyoxometalate (POM) chemistry to tune the selectivity of sulfoxidation reaction catalyzed by decavanadate cluster-based hybrids using H₂O₂ as the oxidant under ambient conditions. By employing two different aryl sulfonium counterions (ASCIs) bearing different organic functional groups (phenol/aldehyde/salicylaldehyde/2,6-diformyl phenol) in a 1 : 1 synthetic feed ratio, we have generated a series of decavanadate-based hybrids HY1–HY6. Different functional groups on the periphery of hybrids HY1–HY6 helped control the efficiency and selectivity of the sulfoxidation reaction by fine-tuning the electronic and supramolecular effects of these hybrids as catalysts. Further, these hybrids were also applied as catalysts for detoxifying 2-chloroethyl ethyl sulfide (CEES), a mustard gas simulant. The hybrid HY5, with a structural formula (DFHPDS)₂(FPDS)₂[H₂V₁₀O₂₈](H₂O)₃ (DFHPDS = (3,5-diformyl-4-hydroxyphenyl)dimethylsulfonium, and FPDS = (4-formylphenyl)dimethylsulfonium) showed the best catalytic properties in the series, with up to 99% conversion and 85% and 99% selectivity towards sulfoxide in the case of dibenzothiophene (DBT) and CEES, respectively. This study's findings open new avenues for tuning the catalytic properties of POM-based hybrids toward selective organic transformation reactions by using a mixed counterion strategy.