Ionic Lignin Polymers for Controlled CO Capture, Release, and Conversion into High-Value Chemicals.

In this study, an innovative and cost-effective ionic polymer for CO capture and utilization for the first time, using abundant and nonfood-based biomass lignin is reported. The modified ionic polymer synthesizes through the reaction of glycidyltrimethylammonium chloride with lignin under alkaline conditions to yield quaternary ammonium ionic functionality. Subsequently, the hydroxide-based pure ionic lignin polymer is employed for CO capture from both direct air and concentrated CO sources at room temperature and atmospheric pressure. Structural characterization of the polymers is accomplished through H, C, and 2D-heteronuclear single quantum coherence (HSQC) NMR, and FT-IR spectroscopy. The CO capture process is established through the formation of bicarbonate ions alongside the presence of CO. The captured CO is precisely quantified by using inverse-gated proton decoupled C NMR with an internal standard (trioxane). Remarkably, the captured-CO amounts of ionic lignin polymer are 1.06 mmol g (47 mg g) from concentrated-CO source and 0.60 mmol g (26 mg g) from direct-air. The captured-CO in ionic lignin polymer is released in controlled manner and utilized in the synthesis of cyclic carbonate, showcasing the productive application of the captured carbon. Moreover, the fully controlled recovering of ionic lignin polymer achieves via repeated CO release ↔ CO capture.