Abstract
Development of efficient carbon capture-and-release technologies with minimal energy input is a long-term challenge in mitigating CO2 emissions, especially via CO2 chemisorption driven by engineered chemical bond construction. Herein, taking advantage of the structural diversity of ionic liquids (ILs) in tuning their physical and chemical properties, precise reaction energy regulation of CO2 chemisorption was demonstrated deploying metal-ion-amino-based ionic liquids (MAILs) as absorbents. The coordination ability of different metal sites (Cu, Zn, Co, Ni, and Mg) to amines was harnessed to achieve fine-tuning on stability constants of the metal ion-amine complexes, acting as the corresponding cations in the construction of diverse ILs coupled with CO2-philic anions. The as-afforded MAILs exhibited efficient and controllable CO2 release behavior with great reduction in energy input and minimal sacrifice on CO2 uptake capacity. This coordination-regulated approach offers new prospects for the development of ILs-based systems and beyond towards energy-efficient carbon capture technologies.
| Original language | English |
|---|---|
| Article number | e202102136 |
| Journal | ChemSusChem |
| Volume | 15 |
| Issue number | 2 |
| DOIs | |
| State | Published - Jan 21 2022 |
Funding
The research was supported financially by the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences, US Department of Energy. In a typical procedure, CO2 capture was carried out in a 3 mL glass vial, and needles were used for CO2 bubbling. With a suitable CO2 bubbling rate at 5 mL min?1, the absorption reaction was conducted with about one mole MAILs under stirring conditions at 25 ?C for 40 min. The amount of CO2 capture was determined by an electronic balance within an accuracy of ?0.1 mg at regular intervals. Furthermore, [Ni(DecNH2)4][NTf2]2 was chosen to study recycling performance. Desorption was performed under 70 ?C for 60 min using N2 bubbling with flow rate at 5 mL min?1. After absorption equilibrium, a CO2 release experiment was performed in an oven under 40, 60, and 80 ?C for 30 min in sequence to explore different desorption behavior for amines and MAILs as well as the energy consumption. The research was supported financially by the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences, US Department of Energy. [Zn(OctNH2)4][NTf2]2 and [Cu(OctNH2)4][NTf2]2 were synthesized following similar procedures.[18] For the synthesis of [Zn(OctNH2)4][NTf2]2, LiNTf2 (5.74 g, 20 mmol) was added into OctNH2 (5.17 g, 40 mmol), and the mixture was thoroughly stirred at room temperature until LiNTf2 was completely dissolved. Zn(NO3)2?6 H2O (2.97 g, 10 mmol) was dissolved in deionized water (20 mL), and then added dropwise to the homogeneous mixture of LiNTf2 and OctNH2 under vigorous stirring conditions. After stirring for 24 h, dichloromethane (CH2Cl2, 20 mL) was added to form a biphasic solution system where the obtained hydrophobic IL [Zn(OctNH2)4][NTf2]2 was dissolved in the organic phase. The IL phase was repeatedly washed with deionized water to ensure that all LiNO3 residues were removed. The removal of water in the organic phase was achieved using anhydrous Na2SO4, CH2Cl2 was evaporated, and the remaining product was dried at 60 ?C under high vacuum overnight to produce the clear IL (yield?5.19 g, 83 %). Similarly, the dark blue IL [Cu(OctNH2)4][NTf2]2 was prepared using Cu(NO3)2?3 H2O. [Ni(OctNH2)4][NTf2]2 was also directly synthesized via a similar facile route. Ni(NTf2)2 (0.62 g, 1 mmol) and OctNH2 (0.52 g, 4 mmol) were mixed at 40 ?C under vigorous stirring conditions overnight to obtain a homogeneous IL. [Ni(DecNH2)4][NTf2]2 was obtained using DecNH2 with the molar ratio of 1 : 4 for Ni(NTf2)2 to DecNH2. Additionally, [Ni(DecNH2)8][NTf2]2 (1 : 8) and [Ni(DecNH2)12][NTf2]2 (1 : 12) were synthesized with different molar ratios of Ni(NTf2)2 and DecNH2. [Mg(OctNH2)4][NTf2]2 was prepared following the similar procedure of [Ni(OctNH2)4][NTf2]2, using Mg(NTf2)2 (0.58 g, 1 mmol) and OctNH2 (0.52 g, 4 mmol). Mg(NTf2)2 (0.58 g, 1 mmol) and DecNH2 (0.52 g, 4 mmol) were used for the synthesis of [Mg(DecNH2)4][NTf2]2. For the synthesis of [Co(OctNH2)4][NTf2]2, Co(NTf2)2 (0.62 g, 1 mmol) was added into OctNH2 (0.52 g, 4 mmol), the mixture was thoroughly stirred at 40 ?C overnight to obtain a homogeneous IL. [Li(OctNH2)4][NTf2] was synthesized using OctNH2 (0.52 g, 4 mmol) with the molar ratio of 1 : 4 for LiNTf2 (0.29 g, 1 mmol) to OctNH2, and the chemicals were mixed at room temperature under vigorous stirring conditions overnight. The MAILs with binary or multiple metal sites, including [CuZn(DecNH2)4][NTf2]2, [CuMg(DecNH2)4][NTf2]2, and [CuZnNiMg(DecNH2)4][NTf2]2, were obtained using the simple mixture of the corresponding MAILs with single metal sites. For example, for the synthesis of [CuZn(DecNH2)4][NTf2]2, [Cu(DecNH2)4][NTf2]2 (0.63 g, 0.5 mmol), and [Zn(DecNH2)4][NTf2]2 (0.63 g, 0.5 mmol) were added into a vial and thoroughly stirred at 40 ?C overnight to obtain a homogeneous IL. [CuZnNiMg(DecNH2)4][NTf2]2 was also prepared using the simple mixture of the corresponding MAILs with single metal sites. [Cu(DecNH2)4][NTf2]2 (0.25 g, 0.2 mmol), [Zn(DecNH2)4][NTf2]2 (0.25 g, 0.2 mmol), [Ni(DecNH2)4][NTf2]2 (0.25 g, 0.2 mmol), and [Mg(DecNH2)4][NTf2]2 (0.24 g, 0.2 mmol) were added into a vial and thoroughly stirred at 40 ?C overnight for further study. For the synthesis of DBU/PEG200, equimolar DBU (0.61 g, 4 mmol) and PEG200 (0.80 g, 4 mmol) were mixed at 40 ?C under vigorous stirring conditions overnight for further study.[19] For DBU/PEG200-Ni[NTf2]2, Ni(NTf2)2 (0.62 g, 1 mmol) was added into the DBU/PEG200 system (1.41 g, 4 mmol), and the mixture was stirred at 40 ?C overnight to obtain a homogeneous liquid. Mg(NTf2)2 (0.62 g, 1 mmol) and DBU/PEG200 system (1.41 g, 4 mmol) were used for the synthesis of DBU/PEG200-Mg[NTf2]2. In a typical procedure, CO2 capture was carried out in a 3 mL glass vial, and needles were used for CO2 bubbling. With a suitable CO2 bubbling rate at 5 mL min?1, the absorption reaction was conducted with about one mole MAILs under stirring conditions at 25 ?C for 40 min. The amount of CO2 capture was determined by an electronic balance within an accuracy of ?0.1 mg at regular intervals. Furthermore, [Ni(DecNH2)4][NTf2]2 was chosen to study recycling performance. Desorption was performed under 70 ?C for 60 min using N2 bubbling with flow rate at 5 mL min?1. After absorption equilibrium, a CO2 release experiment was performed in an oven under 40, 60, and 80 ?C for 30 min in sequence to explore different desorption behavior for amines and MAILs as well as the energy consumption. The research was supported financially by the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences, US Department of Energy.