An Overview of Structure and Dynamics Associated with Hydrophobic Deep Eutectic Solvents and Their Applications in Extraction Processes

Abstract

Recent development of novel water-immiscible green solvents known as hydrophobic deep eutectic solvents (HDESs) has opened the gates for applications requiring media where the presence of water is undesirable. Ever since they were prepared, researchers have used HDESs in diverse fields such as extraction processes, CO 2 sequestration, membrane formation, and catalysis. The structure and dynamics associated with the species comprising HDESs guide their suitability for specific applications. For example, varying the alkyl tail length of the HDES components significantly affects the dynamics of the compo-nents and thus helps in tuning the efficiency of extraction processes. However, the development of HDESs is still in infancy, and very few theoretical studies are available in the literature that help in understanding the structure and dynamics of HDESs. This review highlights the recent studies focused on the microscopic structure and dynamics of HDESs and their potential applications, particularly in extraction processes. We have also provided a glimpse of how the integration of experiments and computational techniques can help delineate the mechanism of extraction processes.

Solvation Shell Structures of Ammonia in Reline and Ethaline Deep Eutectic Solvents

“…This motivated scientists to search for novel solvents like ionic liquids (ILs) and their analogs. ILs have emerged as potential solvents to mitigate and recycle NH 3 owing to their better gas absorption capacity. , ILs have been found to be superior to traditional solvents because of their extraordinary properties such as low vapor pressure, adjustable structure, and excellent stability. − However, most ILs have high production costs because of costly starting materials and complex synthesis procedures, which severely restricts their use on a large industrial scale. , Deep eutectic solvents (DESs) have recently been used as a substitute media for ILs in gas sequestration applications because of their cheap cost and unique properties such as simple synthesis, biodegradability, adjustable character, good thermal stability, low toxicity, and low volatility. − Typically, DESs are prepared by mixing a hydrogen bond acceptor (HBA) and a hydrogen bond donor (HBD) in a particular ratio, forming eutectic mixtures near ambient temperatures. − DESs exhibit lower melting temperatures than the precursors because of their complex structural landscape. − Researchers have employed DESs in diverse fields, such as electrochemistry, material synthesis, gas capture, extraction processes, and catalysis. − DESs have also shown prominent results in the sequestration of CO 2 , SO 2 , CH 4 , and H 2 S as well as NH 3 . − …”

Dissolution mechanism of cellulose in a benzyltriethylammonium/urea deep eutectic solvent (DES): DFT-quantum modeling, molecular dynamics and experimental investigation

“…In this regard, the development of new deep eutectic solvents as an eco-friendly medium constitutes the key stage of this project. However, even with the great efforts published recently, 48 the formation mechanism of DESs and their behavior in a reaction medium remain poorly known. 49 To our knowledge, the benzyltriethylammonium/urea DES system was never discussed before in the literature as an ecofriendly solvent for cellulose dissolution and functionalization.…”

Origin of structural and dynamic heterogeneity in thymol and coumarin-based hydrophobic deep eutectic solvents as revealed by molecular dynamics

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] The structure and dynamics of DESs are mainly guided by the intermolecular hydrogen bonding interaction between the HBA and HBD species along with electrostatic and van der Waals interactions. [15][16][17][18][19][20][21][22][23][24][25][26] DESs exhibit exceptional qualities such as low volatility, biodegradability, mild toxicity, and low flammability, in addition to inexpensive production costs. 2,[27][28][29] Because of these properties, DESs have found applications in the fields of electrochemistry, [30][31][32][33][34] gas sequestration, [35][36][37][38][39] material synthesis, 40,41 extraction processes, 42,43 biotransformation, 44,45 and catalysis.…”

“…Knowing the microscopic structure and dynamics of thymol-coumarin-based HDESs is essential for understanding the extraction mechanism of a specific compound. 26 The structure of HDESs plays a crucial role in choosing the appropriate HDES having higher extraction efficiency. 72,73 Experimentally, thymol : coumarin (1 : 1) HDES exhibits higher extraction efficiency than thymol : coumarin (2 : 1) HDES when utilized for Sudan dye extraction from a sample of spices.…”