Induced Protic Behaviour in Aprotonic Ionic Liquids by Anion Basicity for Efficient Carbon Dioxide Capture

International audienc

Using Thermodynamics to Assess the Molecular Interactions of Tetrabutylphosphonium Carboxylate-Water Mixtures

International audienceDensities, ρ, viscosities, η, and enthalpies of mixing of binary [P4 4 4 4][CnCOO]–water mixtures (with n = 1, 2 or 7) were determined at atmospheric pressure as a function of temperature. The excess, apparent, and partial molar volumes were deduced from experimental data, as well as fragilities, m*, and excess Gibbs free energies of activation of viscous flow exhibited predominantly negative deviation from ideality, with a minimum at approximately xw ~0.8 for all three systems, indicating strong hydrogen-bonding interactions. All three binary systems were found to be fragile, with [P4 4 4 4][C7COO] showing the smallest deviations in fragility with the addition of water. Mixing enthalpy values of the systems were exothermic over the entire composition range, having the following trend: [P4 4 4 4][C2COO] > [P4 4 4 4][C7COO] > [P4 4 4 4][C1COO]

Spectroscopic Signatures of Hydrogen-Bonding Motifs in Protonic Ionic Liquid Systems: Insights from Diethylammonium Nitrate in the Solid State

Diethylammonium nitrate, [N0 0 2 2][NO3], and its perdeuterated analogue, [ND D 2 2] [NO3], were structurally characterized and studied by infrared, Raman, and inelastic neutron scattering (INS) spectroscopy. Using these experimental data along with state-of-the-art computational materials modeling, we report unambiguous spectroscopic signatures of hydrogen-bonding interactions between the two counterions. An exhaustive assignment of the spectral features observed with each technique has been provided, and a number of distinct modes related to NH···O dynamics have been identified. We put a particular emphasis on a detailed interpretation of the high-resolution, broadband INS experiments. In particular, the INS data highlight the importance of conformational degrees of freedom within the alkyl chains, a ubiquitous feature of ionic liquid (IL) systems. These findings also enable an in-depth physicochemical understanding of protonic IL systems, a first and necessary step to the tailoring of hydrogen-bonding networks in this important class of materials.Financial support from the Gipuzkoako Foru Aldundia and the Spanish Ministry of Science and Innovation under grant numbers 2020-CIEN-000009-01 and PID2020-114506GB-I00 is gratefully acknowledged. This work has been generously supported by PL-Grid Infrastructure and the PROMETHEUS supercomputing facility.Peer reviewe