CO2 capture by 1,2,3-triazole-based deep eutectic solvents: the unexpected role of hydrogen bonds

Zonghua Wang; Congyi Wu; Ze Wang; Shaoze Zhang; Dezhong Yang

doi:10.1039/d2cc02503e

CO₂ capture by 1,2,3-triazole-based deep eutectic solvents: the unexpected role of hydrogen bonds

Chem Commun (Camb). 2022 Jun 30;58(53):7376-7379. doi: 10.1039/d2cc02503e.

Authors

Zonghua Wang¹, Congyi Wu¹, Ze Wang¹, Shaoze Zhang^{2

3}, Dezhong Yang¹

Affiliations

¹ School of Science, China University of Geosciences, Beijing, China. yangdz@cugb.edu.cn.
² National Engineering Laboratory for Vacuum Metallurgy, Kunming University of Science and Technology, Kunming, Yunnan province, China.
³ Engineering Laboratory for Advanced Battery and Materials of Yunnan Province, Kunming University of Science and Technology, Kunming, Yunnan province, China. szzhang@kust.edu.cn.

PMID: 35699117
DOI: 10.1039/d2cc02503e

Abstract

Herein, tetraethylammonium 1,2,3-triazolide ([Et₄N][Tz]), 1,2,3-triazole (Tz), and ethylene glycol (EG) are used to form DESs for CO₂ capture. Surprisingly, [Et₄N][Tz]-EG DESs can react with CO₂, but [Et₄N][Tz]-Tz cannot react with CO₂, although both of the two systems contain the same anion [Tz]^-. Unexpectedly, with the addition of EG to [Et₄N][Tz]-Tz, the formed ternary DESs [Et₄N][Tz]-Tz-EG can react with CO₂, although neither EG nor [Et₄N][Tz]-Tz can react with CO₂ before the combination of them. NMR, FTIR and theoretical calculation results disclose that the surprise CO₂ absorption behavior mainly depends on the strength of hydrogen bonds (H-bonds) between the anion [Tz]^- and H-bond donors (EG or Tz). The strength of the H-bond between [Tz]^- and Tz is much stronger than that between [Tz]^- and EG. The strong H-bond between [Tz]^- and Tz in [Et₄N][Tz]-Tz greatly reduces the basicity of [Tz]^-, rendering the anion [Tz]^- unreactive to CO₂. In [Et₄N][Tz]-Tz-EG ternary DESs, EG competes with Tz to form a H-bond with [Tz]^-, which weakens the strength of the H-bond between [Tz]^- and Tz. Moreover, H-bonds also impact the desorption behavior. [Et₄N][Tz] : EG (1 : 2) is regenerated at 60 °C, whereas the chemisorbed CO₂ by [Et₄N][Tz] : Tz : EG (1 : 2 : 2) can be released even down to 30 °C.