Multi‐Molar Absorption of CO₂ by the Activation of Carboxylate Groups in Amino Acid Ionic Liquids

Abstract

A new strategy for multi-molar absorption of CO2 is reported based on activating a carboxylate group in amino acid ionic liquids. It was illustrated that introducing an electron-withdrawing site to amino acid anions could reduce the negative inductive effect of the amino group while simultaneously activating the carboxylate group to interact with CO2 very efficiently. An extremely high absorption capacity of CO2 (up to 1.69 mol mol(-1) ) in aminopolycarboxylate-based amino acid ionic liquids was thus achieved. The evidence of spectroscopic investigations and quantum-chemical calculations confirmed the interactions between two kinds of sites in the anion and CO2 that resulted in superior CO2 capacities.

Carbon Dioxide Capture by Aqueous Ionic Liquid Solutions

“…The 13 C-{ 1 H} NMR spectrum of BMMIm·OAc [33] (Figure 2) clearly shows as ignal at 160.2 ppm along with the expecteds ignals of the IL suggesting again the formation of bicarbonate. Indeed, bicarbonate formation increases from 0.33 to 1.96 mol mol À1 with the augmentation of the water content (entries2 to 5, Ta ble 1) and in the case of the physisorbed CO 2 up to 8.15 mol mol À1 .A ta ratio of 1:1000 (IL/H 2 O), more than 10.1 moles of CO 2 sorption (physicala nd chemical) can be estimated from the 13 C-{ 1 H} NMR spectra ( Figure S6);h igher than recently reported multimolar absorption of CO 2 by the activation of carboxylate groups in amino acidILs (1.69 mol mol À1 ) [32] or aqueous ethanol amine solutions[ 0.63 mol mol À1 for N-methylethanolamine (MDEA) aqueous solutions( 30 wt %) at 28 bar and 40 8C]. [27,28] Note that previously reported 13 CH R-MAS (high-resolutionm agic-angle spinning) NMR spectra and ab initio calculations indicate that the preferential interaction of the CO 2 with BMIm·OAc resultsf rom an acid/base interaction between the carboxylate and the acid carbon in the CO 2 molecule.…”

“…[17,[19][20][21]32] However,i no ur case, the carbamate pathway can be discardeda so nly two 13 C signals wereo bserved for the anion with chemical shifts very close to that displayed by the starting material. [17,[19][20][21]32] However,i no ur case, the carbamate pathway can be discardeda so nly two 13 C signals wereo bserved for the anion with chemical shifts very close to that displayed by the starting material.…”

“…These sorption values are highert han the classical alkanol amines or even alkaline aqueous solutionsunder similarexperimental conditions. [8,12,15,18,19,[30][31][32] Althought he solubility of CO 2 in water [33] is well known, its contributiont ot he CO 2 solubility in wet ILs is usually not taken into account (see Ta ble S1). [24][25][26][27][28] Therefore, it can be envisaged that CO 2 could also be trapped into the IL by reactionw ith water to produce bicarbonate species.…”

Azole‐Anion‐Based Aprotic Ionic Liquids: Functional Solvents for Atmospheric CO2 Transformation into Various Heterocyclic Compounds

“…A new signal appeared at δ =162.2 ppm, which was assigned to the carbonyl carbon atom, thus indicating that the IL had reacted with CO 2 to form a carbamate at atmospheric pressure. IR analysis was also performed on the as‐formed products following the exposure of [Bu 4 P][2‐MIm] to CO 2 ; the band at 1640 cm −1 became more intense, thus suggesting the formation of a carbamate from the IL and CO 2 . 13 C NMR analysis of the other azole‐based ILs with the [Bu 4 P] cation (i.e., [Bu 4 P][4‐MIm], [Bu 4 P][2,4‐DMIm], and [Bu 4 P][MIm]) following exposure to atmospheric CO 2 also indicated the formation of the corresponding carbamates (see the Supporting Information, Figure S2–S4), thus suggesting that these ILs could capture atmospheric CO 2 through the formation of carbamates.…”

Bifunctional Ionic Liquids Derived from Biorenewable Sources as Sustainable Catalysts for Fixation of Carbon Dioxide

“…Recently, Dai et al. reported that amino‐acid‐based ILs act as multimolar absorbing materials of carbon dioxide through the carboxylate group and the amine group …”