The ever-growing demand for advanced energy storage devices in portable electronics, electric vehicles and large scale power grids has triggered intensive research efforts over the past decade on lithium and sodium batteries. The key to improve their electrochemical performance and enhance the service safety lies in the development of advanced electrode, electrolyte, and auxiliary materials. Ionic liquids (ILs) are liquids consisting entirely of ions near room temperature, and are characterized by many unique properties such as ultralow volatility, high ionic conductivity, good thermal stability, low flammability, a wide electrochemical window, and tunable polarity and basicity/acidity. These properties create the possibilities of designing batteries with excellent safety, high energy/power density and long-term stability, and also provide better ways to synthesize known materials. IL-derived materials, such as poly(ionic liquids), ionogels and IL-tethered nanoparticles, retain most of the characteristics of ILs while being endowed with other favourable features, and thus they have received a great deal of attention as well. This review provides a comprehensive review of the various applications of ILs and derived materials in lithium and sodium batteries including Li/Na-ion, dual-ion, Li/Na-S and Li/Na-air (O) batteries, with a particular emphasis on recent advances in the literature. Their unique characteristics enable them to serve as advanced resources, medium, or ingredient for almost all the components of batteries, including electrodes, liquid electrolytes, solid electrolytes, artificial solid-electrolyte interphases, and current collectors. Some thoughts on the emerging challenges and opportunities are also presented in this review for further development.

Layer-stacking structures are very common in two-dimensional covalent organic frameworks (2D COFs). While their structures are normally determined under solvent-free conditions, the structures of solvated 2D COFs are largely unexplored. We report herein the in situ determination of solvated 2D COF structures, which exhibit an obvious difference as compared to that of the same COF under dried state. Powder X-ray diffraction (PXRD) data analyses, computational modeling, and Pawley refinement indicate that the solvated 2D COFs experience considerable interlayer shifting, resulting in new structures similar to the staggered AB stacking, namely, quasi-AB-stacking structures, instead of the AA-stacking structures that are usually observed in the dried COFs. We attribute this interlayer shifting to the interactions between COFs and solvent molecules, which may weaken the attraction strength between adjacent COF layers. Density functional theory (DFT) calculations confirm that the quasi-AB stacking is energetically preferred over the AA stacking in solvated COFs. All four highly crystalline 2D COFs examined in the present study exhibit considerable interlayer shifting upon solvation, implying the universality of the solvent-induced interlayer stacking rearrangement in 2D COFs. These findings prompt re-examination of the 2D COF structures in solvated state and suggest new opportunities for the applications of COF materials under wet conditions.

C olefin separations present one of the great challenges in hydrocarbon purifications owing to their similar structures, thus a single separation mechanism often met with limited success. Herein we report a series of anion-pillared interpenetrated copper coordination for which the cavity and functional site disposition can be varied in 0.2 Å scale increments by altering the anion pillars and organic linkers (GeFSIX-2-Cu-i (ZU-32), NbFSIX-2-Cu-i (ZU-52), GeFSIX-14-Cu-i (ZU-33)), which enable selective recognition of different C olefins. In these materials the rotation of the organic linkers is controlled to create a contracted flexible pore window that enables the size-exclusion of specific C olefins, while still adsorbing significant amounts of 1,3-butadiene (C H ) or 1-butene (n-C H ). Combining the molecular recognition and size-sieving effect, these materials unexpectedly realized the sieving of C H /n-C H , C H /iso-C H , and n-C H /iso-C H with high capacity.

Resolving single-crystal structures of two-dimensional covalent organic frameworks (2D COFs) is a great challenge, hindered in part by limited strategies for growing high-quality crystals. A better understanding of the growth mechanism facilitates development of methods to grow high-quality 2D COF single crystals. Here, we take a different perspective to explore the 2D COF growth process by tracing growth intermediates. We discover two different growth mechanisms, nucleation and self-healing, in which self-assembly and pre-arrangement of monomers and oligomers are important factors for obtaining highly crystalline 2D COFs. These findings enable us to grow micron-sized 2D single crystalline COF Py-1P. The crystal structure of Py-1P is successfully characterized by three-dimensional electron diffraction (3DED), which confirms that Py-1P does, in part, adopt the widely predicted AA stacking structure. In addition, we find the majority of Py-1P crystals (>90%) have a previously unknown structure, containing 6 stacking layers within one unit cell.

Acetylene (C 2 H 2) removal from ethylene (C 2 H 4) is a crucial step in the production of polymer-grade C 2 H 4 but remains a daunting challenge because of the similar physicochemical properties of C 2 H 2 and C 2 H 4. Currently energyintensive cryogenic distillation processes are used to separate the two gases industrially. A robust ultramicroporous metalorganic framework (MOF), Ni 3 (pzdc) 2 (7 Hade) 2 , is reported for efficient C 2 H 2 /C 2 H 4 separation. The MOF comprises hydrogen-bonded linked one-dimensional (1D) chains, and features high-density open metal sites (2.7 nm À3) and electronegative oxygen and nitrogen sites arranged on the pore surface as cooperative binding sites. Theoretical calculations, in situ powder X-ray diffraction and Fourier-transform infrared spectroscopy revealed a synergistic adsorption mechanism. The MOF possesses S-shaped 1D pore channels that efficiently trap trace C 2 H 2 at 0.01 bar with a high C 2 H 2 uptake of 60.6 cm 3 cm À3 and C 2 H 2 /C 2 H 4 selectivity.