Cucurbit[7]uril as Nanoreactor for the Fixation of CO2 with Oxirane: A Density Functional Theory Investigation

To sustain the environment, enormous efforts have been devoted to control the atmospheric CO2 levels. Various catalysts and catalytic systems have been developed so far but the state of art development is far from satisfactory and further enhancement is needed. Considering all the catalytic systems, in the present work a relatively novel nanoreactor (i. e. cucurbit[7]uril) is introduced and investigated for the reaction of CO2 with oxirane. To the best of our knowledge this is the very first report on the fixation reaction of CO2 with oxirane in cucurbit[7]uril (CB[7]) confinement. Density functional theory (DFT) based calculation were carried out to probe the reaction mechanism and the role of the confinement offered by the CB[7] macromolecule. Results show that the fixation reaction of CO2 with epoxide is efficiently catalyzed in the CB[7] confinement. The activation energy for the initiation of the reaction was found to be 32.61 kcal/mol. A reactive intermediate (IM) was observed in the reaction pathway. The relative energy of the IM was 4.26 kcal/mol more than the transition state (TS). The IM undergo further transformation with the energy requirement of similar to 1 kcal/mol to give the final product of the reaction.

Automated summary

Efforts to control atmospheric CO2 levels have been made, but the current state of catalytic systems is unsatisfactory. In this study, a novel nanoreactor, cucurbit[7]uril, was introduced and investigated for the fixation reaction of CO2 with oxirane. DFT calculations were carried out to probe the reaction mechanism and the role of CB[7] confinement. Results show efficient catalysis in the CB[7] confinement, with an activation energy of 32.61 kcal/mol.