Jiangshui Luo

The synergy between ionic liquids (ILs) and metal–organic frameworks (MOFs) has attracted considerable attention because of future applications as a tailor‐made hybrid ionic conductor. The incorporation of ILs into MOFs cages has led to the development of a novel type of solid electrolytes (ILs@MOF), characterized by exceptional thermal stability and high conductivity for large ionic species. In this study, an efficient capillary method was employed to introduce a classical protic IL, [Dema][TfO], into ZIF‐8 pores, consisting of sodalite‐type cages (Zn(MeIm) ₂ ). Our investigation focuses on the influence of varying ILs content on the free (pore) volume, thermal stability, microstructure, and ionic conductivity. The uptake of [Dema][TfO] results in a ZIF‐8 cage expansion, accompanied by a decrease of the decomposition temperature. Upon infiltration of [Dema][TfO] into the ZIF‐8 pores, the preexisting hydrogen bonds within the IL are broken due to confinement effects. Notably, when ZIF‐8 pores are entirely saturated with [Dema][TfO], the composite material exhibits an ionic conductivity of 1.09(6) mS·cm ⁻¹ (at 160°C under anhydrous conditions) with an activation energy of 0.45(3) eV, which is better than other ILs@MOF conductive composites. These findings reveal ILs@MOF hybrid composites are versatile systems to compose protic conductors, attributable to their elevated ionic conductivity.

Metal–organic frameworks (MOFs) are three-dimensional crystalline materials composed of metal nodes and organic ligands, forming porous coordination networks with high surface areas and tunable internal cavities. These structural features enable MOFs to act as hosts for small guest molecules, such as ionic liquids (ILs), facilitating host–guest interactions that can modify physical properties and enhance performance in applications such as fuel cells and batteries. In this study, two imidazolium-based aprotic ILs with different anions, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([Emim][TfO]) and 1-ethyl-3-methylimidazolium bis-(trifluoromethylsulfonyl)imide ([Emim][TFSI]), were successfully encapsulated within the pores of the MOF ZIF-8. The structural and vibrational impacts of these ILs on the ZIF-8 framework were systematically investigated using powder X-ray diffraction (PXRD) and Fourier-transform infrared spectroscopy (FT-IR). The results revealed two distinct mechanisms for the uptake of an IL, leading to an expansion of the MOF cage structure: [Emim][TfO]@ZIF-8 exhibited a phase transition characterized by the coexistence of two lattice constants, while [Emim][TFSI]@ZIF-8 maintained a single-phase structure with continuous lattice expansion upon increased loading. These behaviors are attributed to the swing motion of 2-methylimidazole linkers and the elongation of Zn–N bonds induced by internal pressure from the confined ILs. Additionally, confinement within the ZIF-8 cages led to the strengthening of –SO₃ and S–N–S bonds in the ILs, as evidenced by the blue-shifted and intensified IR vibrational modes. This study provides fundamental insights into the structural evolution and host–guest interactions in IL@MOF systems, offering guidance for tailoring MOF properties through ILs encapsulation.

To explore the impact of the aspect ratio of the channels in the flow fields of solid oxide electrolysis cells on the performance of the cell, we developed three-dimensional models for cells with varying aspect ratios. Our findings revealed that channels with low and high aspect ratios exhibit higher maximum pressure drops, whereas those with medium aspect ratios have the lowest pressure drops. Additionally, the mole fraction of the hydrogen decreases as the channel’s aspect ratio increases. We also computed the polarization curves for SOEC operating under three distinct aspect ratio channels. Our results suggest that structures with low aspect ratios exhibit the poorest electrochemical performance, suitable only for brief operations at low current densities; medium aspect ratio structures exhibit a balanced performance, making them suitable for various operating conditions; and high aspect ratio structures are best suited for operations at high current densities. This study on selecting different aspect ratios aids in determining the optimal channel parameters for different operating conditions, ultimately enhancing the performance of solid oxide electrolysis cells.

In this work, we present a study on the thermal/transport properties of a novel deep eutectic solvent (DES) obtained by using N-methyltrifluoroacetamide (FNMA) as the hydrogen bond donor (HBD) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as the hydrogen bond acceptor (HBA). The binary phase diagram, thermal stability, flammability, viscosity and ionic conductivity of the as-prepared DESs were investigated at atmospheric pressure. The binary phase diagram shows a range of eutectic molar ratios (x_LiTFSI = 0.2~0.33), with the lowest deep eutectic temperature of −84 °C. At x_LiTFSI = 0.2 (i.e., FNMA:LiTFSI = 4:1 and denoted as DES-4:1). The as-prepared DES composition exhibits high thermal stability (onset temperature of weight loss = 78 °C), a low viscosity (η = 48.9 mPa s at 25 °C), relatively high ionic conductivity (σ = 0.86 mS cm⁻¹ at 25 °C) and non-flammability. The transport properties, including ionic conductivity and viscosity, as a function of temperature are in accordance with the Vogel–Fulcher–Tammann (VFT) equations. With increasing molar ratio of HBD vs. HBA, the viscosity decreases, and the ionic conductivity increases at a given temperature between 25 °C and 80 °C. The roughly equal pseudo-activation energies for ion transport and viscous flow in each composition imply a strong coupling of ion transport and viscous flow. Walden plots indicate vehicular transport as the main ion transport mechanism for the DES-4:1 and DES-3:1 compositions; meanwhile, it was confirmed that the ionic conductivity and viscous flow are strictly coupled. The present work is expected to provide strategies for the development of wide-temperature-range and safer electrolytes with low salt concentrations.

This paper reports the vapor pressure and enthalpy of vaporization for a promising phase change material (PCM) guanidinium methanesulfonate ([Gdm][OMs]), which is a typical guanidinium organomonosulfonate that displays a lamellar crystalline architecture. [Gdm][OMs] was purified by recrystallization. The elemental analysis and infrared spectrum of [Gdm][OMs] confirmed the purity and composition. Differential scanning calorimetry (DSC) also confirmed its high purity and showed a sharp and symmetrical endothermic melting peak with a melting point (T_m) of 207.6 °C and a specific latent heat of fusion of 183.0 J g⁻¹. Thermogravimetric analysis (TGA) reveals its thermal stability over a wide temperature range, and yet three thermal events at higher temperatures of 351 °C, 447 °C, and 649 °C were associated with vaporization or decomposition. The vapor pressure was measured using the isothermogravimetric method from 220 °C to 300 °C. The Antoine equation was used to describe the temperature dependence of its vapor pressure, and the substance-dependent Antoine constants were obtained by non-linear regression. The enthalpy of vaporization (Δ_vapH) was derived from the linear regression of the slopes associated with the linear temperature dependence of the rate of weight loss per unit area of vaporization. Hence, the temperature dependence of vapor pressures ln P_vap (Pa) = 10.99 − 344.58/(T (K) − 493.64) over the temperature range from 493.15 K to 573.15 K and the enthalpy of vaporization Δ_vapH = 157.10 ± 20.10 kJ mol⁻¹ at the arithmetic mean temperature of 240 °C were obtained from isothermogravimetric measurements using the Antoine equation and the Clausius–Clapeyron equation, respectively. The flammability test indicates that [Gdm][OMs] is non-flammable. Hence, [Gdm][OMs] enjoys very low volatility, high enthalpy of vaporization, and non-flammability in addition to its known advantages. This work thus offers data support, methodologies, and insights for the application of [Gdm][OMs] and other organic salts as PCMs in thermal energy storage and beyond.

Lithium–sulfur (Li–S) batteries have received widespread attention, and lean electrolyte Li–S batteries have attracted additional interest because of their higher energy densities. This review systematically analyzes the effect of the electrolyte-to-sulfur (E/S) ratios on battery energy density and the challenges for sulfur reduction reactions (SRR) under lean electrolyte conditions. Accordingly, we review the use of various polar transition metal sulfur hosts as corresponding solutions to facilitate SRR kinetics at low E/S ratios (< 10 µL mg⁻¹), and the strengths and limitations of different transition metal compounds are presented and discussed from a fundamental perspective. Subsequently, three promising strategies for sulfur hosts that act as anchors and catalysts are proposed to boost lean electrolyte Li–S battery performance. Finally, an outlook is provided to guide future research on high energy density Li–S batteries. Graphical