A strategy to achieve the efficient synthesis of alkylidene carbonates from CO2 at atmospheric pressure by tuning the basicity of ionic liquids was developed. Excellent yields were obtained due to basic ionic liquids' dual roles both as absorbents and as activators. The reaction mechanism was investigated through a combination of NMR spectroscopy, controlled experiments and quantum calculations, indicating the importance of a moderate basicity.
A strategy for improving CO 2 capture by imidazolium ionic liquids (ILs) through a reduction in the formation of carbene−CO 2 complex was reported. The carbene−CO 2 complex content in CO 2 capture by imidazolium ILs was determined by a quantitative NMR method, and the carbene−CO 2 complex formation was decreased through a reduction in the basicity of the anion and an enlargement in the steric hindrance of the cation. Thus, both enhanced absorption capacity and improved desorption were achieved, where an ideal IL, [Ipmim][Triz], exhibited a very high capacity of 0.21 g of CO 2 /g of IL and excellent reversibility.
A synchronous strategy for improving the absorption/desorption to achieve highly efficient nitric oxide (NO) capture is proposed by the use of tetrakis(azolyl)borate ionic liquid (IL) [P 66614 ][B(Im) 4 ] with multiple nonconjugated interaction sites. This IL exhibited an ultrahigh absorption capacity up to 8.13 mol of NO per mol of IL, good desorption, and excellent reversibility. Through a combination of absorption experiments, DFT calculations, and FT-IR and NMR characterizations, the results indicate that the ultrahigh NO capacity by [P 66614 ][B(Im) 4 ] originated from multiple-sites chemisorption through the formation of diazeniumdiolates (NONOates), while uniform interaction of multiple nonconjugated sites was responsible for the unusual S-shaped absorption isobar, leading to good desorption and excellent reversibility, which was different from traditional ILs. We believe this work provides a new method for designing highly efficient gas absorbents.
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