Function-oriented ionic polymers having high-density active sites for sustainable carbon dioxide conversion

Abstract

On the basis of the development of function-oriented synthesis (FOS), we presented for the first time an efficient and one-pot construction of functional ionic polymers (FIPs) through the phenol–formaldehyde condensation process (pre-synthetic approach); FIPs had high density of Brönsted acidic and ionic sites. Considering the electrophilic–nucleophilic dual activation of phenolic hydroxyl groups and bromide anions, the imidazolium-based FIP-Im exhibited high activity for metal-, solvent- and additive-free synthesis of cyclic carbonates from CO₂ and epoxides under mild conditions. Then, to obtain higher ionic density and a more flexible skeleton, FIP-Im@QA was also prepared by implanting quaternary ammonium (QA) in the framework of FIP-IMvia the Williamson ether synthesis (post-synthetic modification), which demonstrated high efficiency in the N-formylation reaction of multitudinous secondary amines with CO₂ and PhSiH₃ at ambient temperature. More interestingly, these function-oriented catalysts were compatible with the target transformation under low CO₂ concentration (15% in 85% N₂, v/v) and were also reused for more than six times without a significant loss of activity and selectivity. Therefore, this study could not only facilitate the design and construction of FIPs, but also provide sustainable protocols for efficient production of value-added chemicals from CO₂ under mild conditions.