Survey of Carbon Dioxide Capture in Phosphonium-Based Ionic Liquids and End-Capped Polyethylene Glycol Using DETA (DETA = Diethylenetriamine) as a Model Absorbent

We have performed a survey of carbon dioxide capture in phosphonium-based ionic liquids and end-capped polyethylene glycol using DETA (DETA = diethylenetriamine) as a model absorbent. The carbon dioxide adduct of DETA is zwitterionic and forms readily in both ionic and polymeric media. Crystals of the adduct have been isolated, and its X-ray crystal structure is reported. The adduct is hygroscopic and decomposes with heating, with the onset of decomposition occurring at ∼85 °C. Computational studies were performed examining possible structures for the adducts formed between DETA and CO2 in the gas phase. Also described is a study of the thermal stability of phosphonium ionic liquids and selected polymeric solvents under neutral and oxidizing conditions. Heat capacity measurements were also performed on a number of ionic liquids.