CO2-induced dissolution of ZnO into ionic liquids and its catalytic application for the hydration of propargylic alcohols.

An unexpected CO 2 -induced dissolution of ZnO into ionic liquids was discovered. This process exhibited high dissolution speed and the dissociated mixture was applied as an efficient Zn-based catalytic system for the CO 2 -promoted hydration of propargylic alcohols under atmospheric pressure with broad substrate scope. Moreover, this system could be recycled and reused for at least 16 times with excellent yields continuously obtained, which is an unprecedented record for this reaction. Significantly, this system could employ waste pigments as the ZnO source and work even under flue gas atmosphere. In the mechanistic investigations, the interaction between ZnO, CO 2 and ionic liquids to give N-heterocyclic carbene/CO 2 adducts proved to be the key factor for this specific dissolution. These adducts were further identified to exhibit better reactivity than the normal CO 2 by experimental data and density functional theory (DFT) calculations, which might be responsible for the excellent performance of the abovementioned catalytic system. [Display omitted] • An unexpected CO 2 -induced dissolution of ZnO into ionic liquids is reported. • The dissolution constructs a Zn-catalytic system for hydration of propargyl alcohols. • ZnO pigments and flue gas can be applied as ZnO and CO 2 sources for the hydration. • This catalyst works under ambient pressure and reaches a new record of recyclability. • N-heterocyclic carbene/CO 2 adducts are the key factor for dissolution and catalysis. [ABSTRACT FROM AUTHOR]