Nitrile-functionalized tertiary amines as highly efficient and reversible SO2 absorbents

Guanidinium‐based dicarboxylic acid ionic liquids for SO2 capture

“…Different functionalized group in the anion which provided different active sites with SO 2 lead to different equilibrium absorption capacities. For [TMG][SUB], owing to the fact that the hydrogen atoms in methylene groups which are located beside electron‐withdrawing carbonyl carbon groups was acidic, absorption of SO 2 in the anion of [TMG][SUB] is mostly governed by the interaction via hydrogen bonding between SO 2 and methylene groups . Consequently, [TMG][SUB] has an equilibrium absorption capacity of 5.96 mol mol −1 of IL.…”

“…In addition, the peak associated with the methylene groups bonded to the carbonyl carbon was shifted downfield by 0.205. Therefore, it is considered that the absorption of SO 2 in anions of [TMG][SUB] is mostly governed by the interaction via hydrogen bonding between SO 2 and methylene groups . Such hydrogen bonding interactions could be attributed to the acidic character of hydrogen atoms in methylene groups located beside electron‐withdrawing carbonyl carbon groups .…”

“…On the basis of FTIR, UV, NMR spectra of SO 2 ‐free and SO 2 ‐absorbed ILs as well as the correlative absorption mechanisms proposed, the mechanism for [TMG][PBE] was proposed for the absorption of SO 2 by task‐specific ILs, as shown in Fig. .…”

“…7), the spectra of the SO 2 -absorbed [TMG][SUB] showed a new strong hydroxyl at 3173 cm −1 that was assigned to a hydrogen bond. 22,24,25 The spectrum of the SO 2 -treated IL also manifests two new absorption bands at 1284 cm −1 and 958 cm −1 , which could be assigned to S = O and S-O-H stretch. 5,6 Noticeable and similar changes were also observed for the peaks of [TMG][PBE] associated with SO 2 -free and SO 2 -absorbed samples in Fig.…”

“…Therefore, it is considered that the absorption of SO 2 in anions of [TMG][SUB] is mostly governed by the interaction via hydrogen bonding between SO 2 and methylene groups. 22 Such hydrogen bonding interactions could be attributed to the acidic character of hydrogen atoms in methylene groups located beside electron-withdrawing carbonyl carbon groups. 30 In addition, considering the tiny peak shifts for the methyl groups bonded to the nitrogen atoms, it is evident that SO 2 interacts chemically with [TMG][SUB] through the amino group, forming an ionic species with covalently bound -NH-SO.…”