Ionic Polyureas-A Novel Subclass of Poly(Ionic Liquid)s for CO₂ Capture

The growing concern for climate change and global warming has given rise to investigations in various research fields, including one particular area dedicated to the creation of solid sorbents for efficient CO₂ capture. In this work, a new family of poly(ionic liquid)s (PILs) comprising cationic polyureas (PURs) with tetrafluoroborate (BF₄) anions has been synthesized. Condensation of various diisocyanates with novel ionic diamines and subsequent ion metathesis reaction resulted in high molar mass ionic PURs (M_w = 12 ÷ 173 × 10³ g/mol) with high thermal stability (up to 260 °C), glass transition temperatures in the range of 153-286 °C and remarkable CO₂ capture (10.5-24.8 mg/g at 0 °C and 1 bar). The CO₂ sorption was found to be dependent on the nature of the cation and structure of the diisocyanate. The highest sorption was demonstrated by tetrafluoroborate PUR based on 4,4'-methylene-bis(cyclohexyl isocyanate) diisocyanate and aromatic diamine bearing quinuclidinium cation (24.8 mg/g at 0 °C and 1 bar). It is hoped that the present study will inspire novel design strategies for improving the sorption properties of PILs and the creation of novel effective CO₂ sorbents.