Guanidinium-Based Ionic Liquids for High-Performance SO₂ Capture and Efficient Conversion for Cyclic Sulfite Esters

Abstract

Functionalized ionic liquids (ILs) show great potential in the application of fuel gas desulfurization. Herein, we report the synthesis and function of two new 1,1,3,3-tetramethylguanidine-based ILs (TMG-based ILs), 1,1,3,3-tetramethylguanidine methoxyacetate ([TMG]­[MOAc]) and 1,1,3,3-tetramethylguanidine ethoxyacetate ([TMG]­[EOAc]). As contrast, two traditional TMG-based ILs, 1,1,3,3-tetramethylguanidine tetrafluoroborate ([TMG]­[BF4]) and 1,1,3,3-tetramethylguanidine acetate ([TMG]­[Ac]) were synthesized. [TMG]­[EOAc] exhibited the highest SO2 capacity (10.33 mol·kg–1 ILs), during which the solubility of SO2 in the ILs was investigated with a reaction equilibrium thermodynamic model (RETM). Remarkably, the absorbed SO2 transformed into cyclic sulfite esters with high yields (up to 99%) in [TMG]­[MOAc] without a traditional desorption process. Thanks to its good stability, the cycloaddition reaction is fully revisable in [TMG]­[MOAc] in five cycling measurements. These coupled applications and molecular insights demonstrate a new type of functional material for SO2 capture and its value-added conversion and also provide a new strategy to deal with harmful gas in the most convenient way.

Cation functional group effect on SO2 absorption in amino acid ionic liquids

“…The non-covalent interaction (NCI) analysis can be used to determine the interactions based on electron density and the sign of the second derivative in the perpendicular direction of the bond (λ 2 ) ( Geng et al, 2022 ). This analysis provides a clear description of the attractive and repulsive interactions between AAILs and SO 2 .…”

“…Attributable to the properties of thermal stability, low vapor pressure, physical and chemical stability, adjustability, non-volatility, tuneability, and great tendency to capture SO 2 , ionic liquids (ILs) are a hot research topic in the field of gas absorption as green and clean solvents ( Mondal and Balasubramanian, 2016 ; Yang et al, 2017 ; Cui et al, 2021b ; Rashid, 2021 ; Liu et al, 2022a ). In addition, functional ILs have shown efficient SO 2 absorption ( Ren et al, 2018 ; Wang et al, 2020 ; Geng et al, 2022 ). Doblinger et al (2021) have experimentally measured polar gas SO 2 solubility in non-functionalized IL, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and the functionalized alkyl side-chain of cation by hydroxyl, cyanide, and methyl benzyl.…”

“…To answer why functionalized ILs are applied for absorption one should state that typical ILs have physical absorption and therefore limited absorption capacity; adding functional groups such as hydroxyl, amine, and ether leads to more absorption of SO 2 based on physical and chemical absorption ( Liu et al, 2022b ). ILs based on imidazolium ( Li et al, 2021a ; Doblinger et al, 2021 ), guanidinium ( Wang et al, 2007 ; Geng et al, 2022 ), and pyridinium ( Zeng et al, 2014 ; Yan et al, 2019 ) can physically dissolve the gas. In addition to experimental efforts ( Huang et al, 2014 ; Cui et al, 2020 ; Wang et al, 2021a ; Cui et al, 2021b ; Geng et al, 2021 ; Liu et al, 2022b ; Hou et al, 2022 ) and theoretical and computational studies ( Wang et al, 2007 ; Wang et al, 2022a ; Mohammadi et al, 2022 ) to investigate the solubility of gases in ILs, ab initio and first principle investigations have also been conducted to inspect the structure and mechanism of the complex of IL and SO 2 gas ( Gu et al, 2013 ; Herrera et al, 2017 ; Cui et al, 2020 ; Wang et al, 2020 ; Li et al, 2021a ; Li et al, 2021b ; Yin et al, 2021 ; Zhu et al, 2021 ; Liu et al, 2022b ).…”

Broadband THz graphene absorber with graphene and sensing of trimethylglycine concentration

“…In cosmetics, its functions cover multiple aspects, including cell protection, anti-allergic properties, and pH neutralization. In industrial applications, TMG is commonly used as an intermediate or part of a catalyst [46]. In pharmaceutical formulations, the concentration of TMG used varies depending on the specific drug formula and therapeutic purpose, and excessive use may pose potential risks [47].…”

Green Aqueous Two-Phase Systems Constructed by Guanidinium Ionic Liquid for Efficient Recovery of Gold(I) from Thiosulfate Solution

“…Recently, ILs based on guanidinium salt [guanidinium ionic liquids (GILs)] have gained widespread attention as they are considered a new generation of environmentally friendly ILs with excellent physicochemical properties comparable to those of the widely used imidazolium ILs. , The conjugation that exists between the central carbon atom and the surrounding three nitrogen atoms of the guanidine group in GIL molecules results in enhanced stability and coordination capabilities . Meanwhile, the physicochemical properties of the GILs through adjustments to the carbon chain attached to the nitrogen atoms, giving it the potential for good extraction properties.…”