TY - JOUR
T1 - Induced Protic Behaviour in Aprotonic Ionic Liquids by Anion Basicity for Efficient Carbon Dioxide Capture
AU - Yeadon, Darius J.
AU - Jacquemin, Johan
AU - Plechkova, Natalia V.
AU - Maréchal, Manuel
AU - Seddon, Kenneth R.
PY - 2020/7/2
Y1 - 2020/7/2
N2 - The interactions between aprotonic tetrabutylphosphonium carboxylate ionic liquids (ILs), [P4 4 4 4][CnCOO] (n=1, 2 and 7), and water were investigated. The cation-anion interactions occur via the α-1H on [P4 4 4 4]+ and the carboxylate headgroup of the anion. Upon addition, H2O localises around the carboxylate headgroups, inducing an electron inductive effect towards the oxygens, leading to ion-pair separation. Studies with D2O and [P4 4 4 4][CnCOO] revealed protic behaviour of the systems, with proton/deuterium exchange occurring at the α-1H of the cation, promoted by the basicity of the anion, forming an intermediate ylide. The greater influence of van der Waals forces of the [P4 4 4 4][C7COO] system allows for re-orientation of the ions through larger interdigitation. The protic behaviour of the neat ILs allows for CO2 to be chemically absorbed on the ylide intermediate, forming a phosphonium-carboxylate zwitterion, signifying proton exchange occurs even in the absence of H2O. The absorption of CO2 in equimolar IL-H2O mixtures forms a hydrogen carbonate, through a proposed reaction of the CO2 with an intermediate hydroxide, and carboxylic acid.
AB - The interactions between aprotonic tetrabutylphosphonium carboxylate ionic liquids (ILs), [P4 4 4 4][CnCOO] (n=1, 2 and 7), and water were investigated. The cation-anion interactions occur via the α-1H on [P4 4 4 4]+ and the carboxylate headgroup of the anion. Upon addition, H2O localises around the carboxylate headgroups, inducing an electron inductive effect towards the oxygens, leading to ion-pair separation. Studies with D2O and [P4 4 4 4][CnCOO] revealed protic behaviour of the systems, with proton/deuterium exchange occurring at the α-1H of the cation, promoted by the basicity of the anion, forming an intermediate ylide. The greater influence of van der Waals forces of the [P4 4 4 4][C7COO] system allows for re-orientation of the ions through larger interdigitation. The protic behaviour of the neat ILs allows for CO2 to be chemically absorbed on the ylide intermediate, forming a phosphonium-carboxylate zwitterion, signifying proton exchange occurs even in the absence of H2O. The absorption of CO2 in equimolar IL-H2O mixtures forms a hydrogen carbonate, through a proposed reaction of the CO2 with an intermediate hydroxide, and carboxylic acid.
KW - Physical and Theoretical Chemistry
KW - Atomic and Molecular Physics, and Optics
U2 - 10.1002/cphc.202000320
DO - 10.1002/cphc.202000320
M3 - Article
VL - 21
SP - 1369
EP - 1374
JO - Chemphyschem : a European journal of chemical physics and physical chemistry
JF - Chemphyschem : a European journal of chemical physics and physical chemistry
SN - 1439-4235
IS - 13
ER -