Role of water in dual-ionic pyrazolium salt promoted conversion of CO2 at atmospheric pressure and room temperature

Dual-ionic pyrazolium salts have in this work been synthesized and shown to catalyze the coupling reaction of carbon dioxide (CO2) with epichlorohydrin achieving a 90% yield under 30 °C and 0.1 MPa CO2 pressure. With the aid of a small amount of water, the product yield is greatly improved up to 99.5% under the same reaction conditions, which corresponds to a rate enhancement of up to 1.4 times for the formation of the carbonate. We propose and explore a dual origin of the role of water, first by affecting the gas to liquid mass transfer of CO2, and second a mechanism where water triggers a proton transfer that in turn underlies efficient conversion of CO2. This theoretically derived mechanism is also confirmed by 13C NMR and FT-IR spectroscopy results. The catalyst was found to be reusable eight times without obvious reduction of catalytic activity. The finding presented that an already efficient reaction to attract CO2 is further greatly promoted only by the addition of water which can have important ramifications for green technology.
QC 20230707