Abstract
CO~2~ is locked up: Dual aminoβfunctionalised phosphonium ionic liquids (ILs; see figure) have been prepared. The ILs have excellent thermal properties, such as low glass transition temperatures and high thermal decomposition temperatures. The supported CO~2~ absorption of four of the ILs on porous SiO~2~ was found to approach one mol CO~2~ per mol IL, a factor of two greater than that reported before.magnified image
A series of 20 dual aminoβfunctionalised phosphonium ionic liquids, (3βaminopropyl)tributylphosphonium amino acid salts ([aP~4443~][AA], in which [AA]^β^=[Ala]^β^, [Arg]^β^, [Asn]^β^, [Asp]^β^, [Cys]^β^, [Gln]^β^, [Glu]^β^, [Gly]^β^, [His]^β^, [Ile]^β^, [Leu]^β^, [Lys]^β^, [Met]^β^, [Phe]^β^, [Pro]^β^, [Ser]^β^, [Thr]^β^, [Trp]^β^, [Tyr]^β^ and [Val]^β^), has been prepared. Their physicochemical properties, such as density, viscosity, glass transition and thermal decomposition temperatures and conductivity, have been determined. In particular, the [aP~4443~][AA] ionic liquids (ILs) have low glass transition temperatures ranging from β69.7 to β29.6βΒ°C and high decomposition temperatures (all above 200βΒ°C). The effects of the variation of the structure of [AA]^β^ on the above physicochemical properties are discussed. Furthermore, the CO~2~ absorption of [aP~4443~][Gly], [aP~4443~][Ala], [aP~4443~][Val] and [aP~4443~][Leu], taken as examples, was investigated. It was found that the supported absorption of CO~2~ by the [aP~4443~][AA] ILs almost reaches equilibrium within 80β
min, the chemical absorption of CO~2~ by the [aP~4443~][AA] ILs approaches 1β
molβ
CO~2~ per mol ionic liquid (twice that reported before) and the [aP~4443~][AA] ILs can be repeatedly recycled for CO~2~ uptake.