Ionic liquids (ILs) have been widely investigated as novel solvents, electrolytes, and soft functional materials. Nevertheless, the widespread applications of ILs in most cases have been hampered by their liquid state. The confinement of ILs into nanoporous hosts is a simple but versatile strategy to overcome this problem. Nanoconfined ILs constitute a new class of composites with the intrinsic chemistries of ILs and the original functions of solid matrices. The interplay between these two components, particularly the confinement effect and the interactions between ILs and pore walls, further endows ILs with significantly distinct physicochemical properties in the restricted space compared to the corresponding bulk systems. The aim of this article is to provide a comprehensive review of nanoconfined ILs. After a brief introduction of bulk ILs, the synthetic strategies and investigation methods for nanoconfined ILs are documented. The local structure and physicochemical properties of ILs in diverse porous hosts are summarized in the next sections. The final section highlights the potential applications of nanoconfined ILs in diverse fields, including catalysis, gas capture and separation, ionogels, supercapacitors, carbonization, and lubrication. Further research directions and perspectives on this topic are also provided in the conclusion.

Among energetic materials, there are two significant challenges facing researchers: 1) to develop ionic CHNO explosives with higher densities than their parent nonionic molecules and (2) to achieve a fine balance between high detonation performance and low sensitivity. We report a surprising energetic salt, hydroxylammonium 3-dinitromethanide-1,2,4-triazolone, that exhibits exceptional properties, viz., higher density, superior detonation performance, and improved thermal, impact, and friction stabilities, then those of its precursor, 3-dinitromethyl-1,2,4-triazolone. The solid-state structure features of the new energetic salt were investigated with X-ray diffraction which showed π-stacking and hydrogen-bonding interactions that contribute to closer packing and higher density. According to the experimental results and theoretical analysis, the newly designed energetic salt also gives rise to a workable compromise in high detonation properties and desirable stabilities. These findings will enhance the future prospects for rational energetic materials design and commence a new chapter in this field.

High-energy density materials represent a significant class of advanced materials and have been the focus of energetic materials community. The main challenge in this field is to design and synthesize energetic compounds with a highest possible density and a maximum possible chemical stability. Here we show an energetic compound, [2,2′-bi(1,3,4-oxadiazole)]-5,5′-dinitramide, is synthesized through a two-step reaction from commercially available reagents. It exhibits a surprisingly high density (1.99 g cm−3 at 298 K), poor solubility in water and most organic solvents, decent thermal stability, a positive heat of formation and excellent detonation properties. The solid-state structural features of the synthesized compound are also investigated via X-ray diffraction and several theoretical techniques. The energetic and sensitivity properties of the explosive compound are similar to those of 2, 4, 6, 8, 10, 12-(hexanitrohexaaza)cyclododecane (CL-20), and the developed compound shows a great promise for potential applications as a high-energy density material.

Development of modern high-performance insensitive energetic materials is significant because of the increasing demands for both military and civilian applications. Here we propose a rapid and facile strategy called the "layer hydrogen bonding pairing approach" to organize energetic molecules via layer-by-layer stacking, which grants access to tunable energetic materials with targeted properties. Using this strategy, an unusual energetic salt, hydroxylammonium 4-amino-furazan-3-yl-tetrazol-1-olate, with good detonation performances and excellent sensitivities, was designed, synthesized, and fully characterized. In addition, the expected unique layer-by-layer structure with a high crystal packing coefficient was confirmed by single-crystal X-ray crystallography. Calculations indicate that the layer-stacking structure of this material can absorb the mechanical stimuli-induced kinetic energy by converting it to layer sliding, which results in low sensitivity.

Ultrathin, molecular sieving membranes composed of microporous materials offer great potential to realize high permeances and selectivities in separation applications, but strategies for their production have remained a challenge. Here we show a route for the scalable production of nanometre-thick metal–organic framework (MOF) molecular sieving membranes, specifically via gel–vapour deposition, which combines sol–gel coating with vapour deposition for solvent-/modification-free and precursor-/time-saving synthesis. The uniform MOF membranes thus prepared have controllable thicknesses, down to ~17 nm, and show one to three orders of magnitude higher gas permeances than those of conventional membranes, up to 215.4 × 10−7 mol m−2 s−1 Pa−1 for H2, and H2/C3H8, CO2/C3H8 and C3H6/C3H8 selectivities of as high as 3,400, 1,030 and 70, respectively. We further demonstrate the in situ scale-up processing of a MOF membrane module (30 polymeric hollow fibres with membrane area of 340 cm2) without deterioration in selectivity.