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Articles
Publication Date: 2025
Physical Chemistry Chemical Physics (14639084)
This study presents a comprehensive multiscale computational investigation into the effect of alkyl chain length on the CO2 capture performance of ammonium-based deep eutectic solvents (DESs). Density functional theory (DFT), COSMO-RS calculations, and molecular dynamics (MD) simulations were employed to probe the molecular interactions as well as the structural and dynamical characteristics between CO2 and three DESs containing lactic acid (LA) as the hydrogen bond donor. Interaction energy analysis and vibrational spectra revealed that, in all studied DESs, CO2 preferentially interacts with the LA rather than with the anion or cation. COSMO-RS predictions confirmed that longer chains improve CO2 solubility by increasing hydrophobicity and free volume. Furthermore, MD analysis showed that CO2–LA interactions dominate, and longer chains reduce cation–CO2 proximity due to steric effects. Structural and dynamic analyses, including RDF, SDF, Voronoi, and van Hove correlation functions, confirmed stronger CO2 interactions, reduced ion mobility, and more extensive hydrogen bonding networks in longer-chain DESs. Spectral shifts further indicated physical absorption and increased cation involvement in CO2 capture for longer chains. Finally, the findings demonstrate that extending the cation alkyl chain enhances overall CO2 uptake through stronger dispersion forces, increased free volume, and more diverse hydrogen bonding. Increasing the alkyl chain length of the cation appears to reduce its interaction with CO2, likely due to enhanced steric hindrance. However, as the alkyl chain length increases from DES(1) to DES(3), the overall CO2 uptake improves. This enhancement is attributed to reduced cation–anion and cation–LA interactions caused by steric effects, which in turn increases the availability of the anion and LA to interact more effectively with CO2. This journal is © the Owner Societies, 2026
Publication Date: 2025
Journal of Physical Chemistry B (15205207)129(36)pp. 9190-9205
In this work, the effect of adding a monocationic ionic liquid (MIL) on the properties of a dicationic ionic liquid (DIL) was investigated using molecular dynamics (MD) simulations and quantum mechanical (QM) calculations. The binary mixture of [C6(mim)2][NTf2]2(DIL) and [P1EOE][NTf2] (MIL) was analyzed in terms of thermophysical, structural, and dynamical properties, along with density functional theory (DFT) and atoms-in-molecules (AIM) analyses. These properties were compared to those of the pure DIL system. Structural properties were examined using radial distribution functions (RDFs) and hydrogen-bonding networks, providing insights into ion arrangement, spatial heterogeneity, and interaction strength. RDF analysis revealed that increasing the MIL mole fraction enhances the local density of anions near the ring hydrogen atoms more significantly than the bulk density. Furthermore, the orientation of imidazolium rings suggests that MIL promotes π–π stacking interactions among [C6(mim)2]2+cations. Notably, the system with xMIL= 0.50 exhibited the lowest structural heterogeneity among the investigated mixtures. Dynamical properties, including mean square displacement (MSD), ionic conductivity, and van Hove correlation functions, were also analyzed. The results indicate that adding MIL enhances microheterogeneity and reduces ion cage strength, thereby facilitating ion mobility and increasing ionic conductivity. QM calculations further demonstrate that adding MIL lowers ion interaction energies due to the formation of stronger hydrogen bonds in the mixture. Additionally, AIM analysis reveals that the presence of MIL increases electron density between the dication and anions. © 2025 American Chemical Society
Publication Date: 2025
Journal of Molecular Liquids (18733166)438
This study leverages MD simulations and COSMO-RS analysis to thoroughly examine a nonlinear tricationic ionic liquid (NLTCIL) containing amine and hydroxyl functional groups, elucidating its intricate interactions with water and CO2. MD simulations reliably predicted physical properties, showing water decreases density while CO2 increases it. Microscopic structural analysis, through RDF, SDF, and CDF, revealed that while the strongest interactions in pure NLTCIL involve chloride anions and imidazolium ring hydrogens, water significantly disrupts these, forming extensive hydrogen bond networks and drastically reducing hydrogen bond lifetimes. CO2, in contrast, exhibited a minor structural impact, primarily occupying voids. 3D RDG distributions highlighted dominant van der Waals interactions around CO2, with water increasing weaker, non-specific interactions and reducing strong hydrogen bonds. TFI visualizations depicted stable CO2 interactions in pure NLTCIL (green/blue regions) but less stable, fluctuating ones (red regions) in water-containing systems, lowering CO2 absorption capacity. Sigma profiles and chemical potential overlaps revealed water's high polarity and strong hydrogen bonding with NLTCIL, outcompeting weaker CO2 interactions, explaining CO2's low solubility in water and humidity's negative impact on absorption. COSMO-RS analysis highlighted NLTCIL's potential for industrial gas separation due to significant CO2 solubility enhancement (up to tenfold at 10 bar) and high selectivity. However, humidity emerged as a critical challenge. The absorption mechanism was primarily linked to interactions at the N, O, and C sites of the cation, with the C-site potentially playing a more significant role. These findings provide crucial groundwork for designing humidity-resistant ionic liquids and optimizing CO2 absorption processes. © 2025 Elsevier B.V.
Publication Date: 2024
Physical Chemistry Chemical Physics (14639084)26(40)pp. 26109-26128
In this study, we investigated the effect of DFT density functionals and dispersion correction on an imidazolium-based dicationic ionic liquid (DIL) using ab initio molecular dynamics simulations. To achieve this purpose, the electronic structures, as well as the structural and dynamical properties of [C3(mim)2][NTF2]2 DIL, were obtained using the BLYP and PBE functionals, both with and without D3-correction, and the results were compared with experimental values. Radial distribution functions and structure factors revealed that applying D3-correction increases the interaction between the anion and hydrogen atoms of the rings and side chains. The simulation of the studied DIL with the BLYP-D3 functional depicted lower structural heterogeneity compared to the other functionals. Analysis of Voronoi tessellation and linkage chain conformations showed a reduction in the aggregation of the linkage alkyl chains in the presence of D3-correction, which is more pronounced in the BLYP functional than in PBE. Additionally, it was observed that the probability of forming a hydrogen-bond network depends on both the type of used density functionals and applying dispersion correction. The results of dynamical properties, such as the self-diffusion coefficients, velocity autocorrelation function, and van Hove correlation function, as well as ion pair, ion cage, and hydrogen bond dynamics, indicated that applying D3-correction in both density functionals leads to an increase in the dynamics of the studied DIL. Additionally, the ratio of self-diffusion coefficients of the anion to the cation in the BLYP functional is closer to experimental values compared to the PBE functional. Furthermore, the electronic structure, including dipole moment distribution, and also infrared (IR) and power spectra were studied. Applying D3-correction and the type of density functionals have a significant effect on the dipole moment distribution of ions. Moreover, the results of IR and power spectra demonstrated that only in the BLYP functional, by applying D3-correction, the hydrogen bonding between the anion and the hydrogen atoms of the cation is strengthened at high wavenumbers. Thus, we conclude that applying D3 correction to both the BLYP and PBE density functionals improves the accuracy in describing the various properties of the studied system. Overall, the evaluation of different structural, dynamical, and vibrational properties of [C3(mim)2][NTF2]2 DIL suggests that the BLYP-D3 density functional may be the best choice among the studied density functionals. © 2024 The Royal Society of Chemistry.
