DFT based engineering of N-heterocyclic carbenes to exacerbate its activity for SO₂ fixation and storage

Carbene compounds are very reactive to SO₂ which assert their candidature to seize this greenhouse gas. Unfortunately, most of the carbenes which produce S,S-dioxide with SO₂, undergo dissociation to yield ketone derivative and SO through an intermediate formation of oxathiirane S-oxide derivative. Thus, carbenes are excluded from the list of catalyst for SO₂ fixation and storage technology. To eradicate this retardation, the stability of different oxathiirane S-oxide derivatives obtained from SO₂ and 56 carbenes of various structures are studied using Density Functional Theory (DFT). Through our study, we are able to find out three oxathiirane S-oxide derivatives which have positive ΔG values for their decomposition to the respective ketone derivatives. This study corroborates that proper engineering of carbene leads to produce a stable oxathiirane S-oxide derivative as a stable product. We observed that carbenes are highly efficient to nab SO₂ at room temperature. This finding should necessitate the recommencement of the use of carbene for SO₂ fixation technology. We also found three carbenes which are able to produce sulfene derivative (C - S bond length is less than 1.7 Å) on reaction with SO₂.