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Ionic liquids (ILs) offer a wide range of promising applications because of their much enhanced properties. However, further development of such materials depends on the fundamental understanding of their hierarchical structures and behaviors, which requires multiscale strategies to provide coupling among various length scales. In this review, we first introduce the structures and properties of these typical ILs. Then, we introduce the multiscale modeling methods that have been applied to the ILs, covering from molecular scale (QM/MM), to mesoscale (CG, DPD), to macroscale (CFD for unit scale and thermodynamics COSMO-RS model and environmental assessment GD method for process scale). In the following section, we discuss in some detail their applications to the four scales of ILs, including molecular scale structures, mesoscale aggregates and dynamics, and unit scale reactor design and process design and optimization of typical IL applications. Finally, we address the concluding remarks of multiscale strategies in the understanding and predictive capabilities of ILs. The present review aims to summarize the recent advances in the fundamental and application understanding of ILs.

Developing effective catalysts based on earth abundant elements is critical for CO 2 electroreduction. However, simultaneously achieving a high Faradaic efficiency (FE) and high current density of CO (j CO) remains a challenge. Herein, we prepare a Mn single-atom catalyst (SAC) with a Mn-N 3 site embedded in graphitic carbon nitride. The prepared catalyst exhibits a 98.8% CO FE with a j CO of 14.0 mA cm −2 at a low overpotential of 0.44 V in aqueous electrolyte, outperforming all reported Mn SACs. Moreover, a higher j CO of 29.7 mA cm −2 is obtained in an ionic liquid electrolyte at 0.62 V overpotential. In situ X-ray absorption spectra and density functional theory calculations demonstrate that the remarkable performance of the catalyst is attributed to the Mn-N 3 site, which facilitates the formation of the key intermediate COOH * through a lowered free energy barrier.

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The capacity of NH3 in PIL [Bim][NTf2] was up to 2.69 mol NH3 per mol IL under ambient conditions.

To study the effect of water on the properties of choline chloride (ChCl)/urea mixtures (1:2 on a molar basis), the density and viscosity of ChCl/ urea (1:2) with water were measured at temperatures from 298.15 K to 333.15 K at atmospheric pressure, the CO 2 solubility in ChCl/urea (1:2) with water was determined at 308.2 K, 318.2 K, and 328.2 K and at pressures up to 4.5 MPa. The results show that the addition of water significantly decreases the viscosity of ChCl/urea (1:2), whereas the effects on their density and CO 2 solubility are much weaker. The CO 2 solubility in ChCl/urea (1:2) with water was represented with the Nonrandom-Two-Liquid Redlich−Kwong (NRTL-RK) model. The excess molar volume and excess molar activation energy were further determined. The CO 2 absorption enthalpy was calculated and dominated by the CO 2 dissolution enthalpy, and the magnitude of the CO 2 dissolution enthalpy decreases with the increase of water content.

Ionic liquid (IL)–amine hybrid solvents have been experimentally proved to be effective for CO2 capture. This Article provided rigorous thermodynamic models, process simulation, and cost estimation of a potential design of IL-based CO2 capture processes. Three ILs ([Bmim]­[BF4], [Bmim]­[DCA], and [Bpy]­[BF4]) were investigated to blend with MEA aqueous solution. The physicochemical properties of the ILs were predicted by several temperature-dependent correlations. Phase equilibria were modeled based on Henry’s law and NRTL equation, and the calculated values were in good agreement with the experimental data. The simulation results show that the [Bpy]­[BF4]–MEA process can save about 15% regeneration heat duty as compared to the conventional MEA process, which is attributed to the reduction of sensible and latent heat. Moreover, a modified [Bpy]­[BF4]–MEA process via adding intercooling and lean vapor recompression presents 12% and 13.5% reduction in overall equivalent energy penalty and capture cost as compared to the conventional MEA process, respectively.

A novel dual amino-functionalized ionic liquid, 1, 3-di (2′-aminoethyl)-2-methylimidazolium bromide (DAIL), was synthesized and investigated as a potential absorbent for CO2 capture. CO2 absorption behavior on pressure, temperature and concentrations of DAIL in aqueous solution were studied, and the absorption mechanism was investigated by spectroscopic methods and DFT calculations. The CO2 capture capacity of 18.5 wt % and good thermal stability (T d = 521.6 K) make DAIL a good candidate for industrial applications for CO2 capture.