A New Type of Supramolecular Fluid Based on H2O–Alkylammonium/Phosphonium Solutions

• Published in: Angewandte Chemie International Edition 2021-03, Vol.60 (14), p.7540-7546
• Main Authors: López‐Bueno, Carlos, Herreros‐Lucas, Carlos, Suárez‐Rodríguez, Manuel, Bittermann, Marius R., Amigo, Alfredo, Woutersen, Sander, Giménez‐López, María, Rivadulla, Francisco
• Format: Article
• Language: English
• Subjects: Ammonium; Atmospheric conditions; Clathrates; Communication; Communications; Compressibility; electrochemistry; Energy storage; Fluid flow; hydrophobic solvation; Hydrophobicity; Incompressible flow; liquid clathrate; Salts; Solvation; supramolecular fluids; Thermal diffusivity; Water chemistry
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202015800

Here we show that by adjusting the concentration of tetrabutyl ammonium and phosphonium salts in water (≈1.5–2.0 m), hydrophobic solvation triggers the formation of a unique, highly incompressible supramolecular liquid, with a dynamic structure similar to clathrates, involving essentially all H2O molecules of the solvent. Despite the increasing local order, the thermal diffusivity, and compressibility of these supramolecular liquids is strongly decreased with respect to bulk water due to slower relaxation dynamics. The results presented in this paper open an avenue to design a new family of supramolecular fluids, stable under atmospheric conditions, which can find important technological applications in energy storage and conversion. A unique, highly incompressible fluid formed by a tight association of water molecules around ammonium and phosphonium salts is described in this paper. Applications of this new family of supramolecular fluids in different electrochemical processes are demonstrated in this work.