Lorenzo Guazzelli
Isabel Maria Marrucho
Tiancheng Mu
Tamal Banerjee- 1University of Pisa, Pisa, Italy
- 2Higher Technical Institute, University of Lisbon, Lisbon, Portugal
- 3Renmin University of China, Beijing, China
- 4IIT Guwahati, Guwahati, India
Editorial on the Research Topic
Ionic liquids and deep eutectic solvents: Two contrasting options or opposite sides of the same coin?
Ionic liquids (ILs) and deep eutectic solvents (DESs) are reported as the alternatives to traditional volatile organic compounds (VOCs). Both ILs and DESs are thought to be tunable and designable although there are still some disagreements and disputes on the nature, greenness, stability of ILs and DESs and even on the relationship between them (Chen and Mu, 2021; Zhang et al., 2022; Afonso et al., 2023). In this Research Topic “Ionic liquids and deep eutectic solvents: Two contrasting options or opposite sides of the same coin?”, we have collected four articles (including two original researches and two reviews) in total, representing the recent intermolecular, interactions, physical properties and relevant applications for ILs and DESs. Below, we would like to provide the summary and research highlight for theses four articles.
Low melting temperature and high ionic conductivity are the key physical properties for ILs. Low melting temperature could make ILs show liquid state at low temperature, while high ionic conductivity is very helpful for ILs to show favorable performance for electrochemical catalysis and batteries. Unfortunately, ionic conductivity of ILs tends to be low when the temperature is low. One of the strategies to solve this contradiction is to design ILs with much lower melting temperature to keep ILs liquid for the purpose of achieving high ionic conductivity. Abdurrokhman and Martinelli (Abdurrokhman I and Martinelli) found that high ionic conductivity and low melting point (and thus wide temperature range of liquid state) could be achieved simultaneously by the strategy of mixing two kinds of ILs with the same imidazolium cation and two different kinds of anions. Binary ILs could also keep the low volatility and high stability of ILs in addition to high ionic conductivity and low melting point, which would be more favorable than the mixtures of VOCs + ILs reported in many reports. This strategy would be very helpful for the application of ILs in electrochemical catalysis and batteries.
Traditional electrochemical deposition of aluminium is commonly performed at very high temperature thus it is energy-intensive and releases carbon dioxide (CO2) and corrosive hydrogen fluoride. Wu et al. make a summary on the electrochemical deposition of aluminium by ILs-based electrolytes. Furthermore, ILs are regarded as tunable, green and safe solvents for the electrochemical deposition of aluminium at mild temperature. These specific fields of aluminium deposition include nano-aluminium, high-purity aluminium and rechargeable aluminium ion batteries. Finally, the authors suggested that in-depth investigation should be conducted to establish the technical criterial.
CO2 capture and separation is very important for CO2 mitigation, fuel purification and CO2 conversion. Available technologies (e.g., absorption, adsorption, membrane and cryogenic separation) for CO2 capture and separation are expensive, energy-consuming, corrosive or non-sustainable. Foorginezhad et al. give a review on the CO2 capture by ILs and DESs due to their unique properties. ILs and DESs could interact with CO2 via physical or chemical interaction, while the unavailable properties of ILs and DESs could be estimated by COSMO-RS for the further improvement of CO2 capture. Criteria are established for evaluating the CO2 absorption via physical interaction (i.e., capacity, viscosity and selectivity) and chemical interaction (capacity, viscosity and absorption enthalpy). According to these criteria, top 10 ILs and DESs are suggested as the most promising green solvents for CO2 absorption.
Immobilization technology by developing immobilized-ILs sorbents could improve the capacity and selectivity for CO2 capture and separation while avoiding the usage of VOCs; however, huge amount of ILs (∼1018) synthesized by trial and error would be time-consuming and low-efficient. Therefore, it is necessary to develop theoretical methods to predict the efficiency of CO2 capture by ILs before the experiment. Dai et al. for the first time propose that compressibility of ILs could be used as the new index for electrolyte perturbed-chain statistical associating fluid theory to predict CO2 capture by immobilized-ILs. Furthermore, desorption enthalpy of CO2 from ILs could also be identified. This theoretic model is reliable, efficient and consistent with the experiments results.
We hope this Research Topic could help better understanding the intermolecular interaction, physical property and application of ILs and DESs on the goal of replacing VOCs. It should be noted that not all ILs and DESs are green and cheap, which mainly depends on the selection of appropriate raw materials and interaction via reasonable design. Finally, we thank all the authors, reviewers, and editors for their contribution in the Research Topic of “Ionic liquids and deep eutectic solvents: Two contrasting options or opposite sides of the same coin?”.
Author contributions
LG and IM conceived the Research Topic. TM and LG wrote the draft of the Editorial. All authors agreed on the final version of the Editorial.
Conflict of interest
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Publisher’s note
All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.
References
Afonso, J., Mezzetta, A., Marrucho, I. M., and Guazzelli, L. (2023). History repeats itself again: Will the mistakes of the past for ILs be repeated for DESs? From being considered ionic liquids to becoming their alternative: The unbalanced turn of deep eutectic solvents. Green Chem. 25, 59–105. doi:10.1039/d2gc03198a
Chen, Y., and Mu, T. (2021). Revisiting greenness of ionic liquids and deep eutectic solvents. GreenChE 2, 174–186. doi:10.1016/j.gce.2021.01.004
Keywords: ionic liquids, deep eutectic solvents, green chemistry, carbon dioxide, batteries, electrochemical deposition
Citation: Guazzelli L, Marrucho IM, Mu T and Banerjee T (2023) Editorial: Ionic liquids and deep eutectic solvents: Two contrasting options or opposite sides of the same coin?. Front. Chem. 11:1169688. doi: 10.3389/fchem.2023.1169688
Received: 19 February 2023; Accepted: 21 February 2023;
Published: 27 February 2023.
Edited and reviewed by:
James Clark, University of York, United KingdomCopyright © 2023 Guazzelli, Marrucho, Mu and Banerjee. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Lorenzo Guazzelli, lorenzo.guazzelli@unipi.it; Tiancheng Mu, tcmu@ruc.edu.cn