Search

Lithium‐ion batteries play an integral role in various aspects of daily life, yet there is a pressing need to enhance their safety and cycling stability. In this study, we have successfully developed a highly secure and flexible solid‐state polymer electrolyte (SPE) through the in situ polymerization of allyl acetoacetate (AAA) monomers. This SPE constructed an efficient Li+ transport channel inside and effectively improved the solid‐solid interface contact of solid‐state batteries to reduce interfacial impedance. Furthermore, it exhibited excellent thermal stability, an ionic conductivity of 3.82×10−4 S cm−1 at room temperature (RT), and a Li+ transport number (tLi+) of 0.66. The numerous oxygen vacancies on layered inorganic SiO2 created an excellent environment for TFSI− immobilization. Free Li+ migrated rapidly at the C=O equivalence site with the poly(allyl acetoacetate) (PAAA) matrix. Consequently, when cycled at 0.5C and RT, it displayed an initial discharge specific capacity of 140.6 mAh g−1 with a discharge specific capacity retention rate of 70 % even after 500 cycles. Similarly, when cycled at a higher rate of 5C, it demonstrated an initial discharge specific capacity of 132.3 mAh g−1 while maintaining excellent cycling stability. [ABSTRACT FROM AUTHOR]

Separation of propyne/propylene (C3H4/C3H6) is more difficult and challenging than that of acetylene/ethylene (C2H2/C2H4) because of their closer molecular sizes. A comprehensive screening of a series of metal–organic frameworks with broad types of structures, pore sizes, and functionalities was carried out. UTSA‐200 was identified as the best separating material for the removal of trace C3H4 from C3H4/C3H6 mixtures. Gas sorption isotherms reveal that UTSA‐200 exhibits by far the highest C3H4 adsorption capacity (95 cm3 cm−3 at 0.01 bar and 298 K) and record C3H4/C3H6 selectivity, which was mainly attributed to the suitable dynamic pore size to efficiently block the larger C3H6 molecule whilst the strong binding sites and pore flexibility capture smaller C3H4. This material thus provides record purification capacity for the removal of C3H4 from a 1:99 (or 0.1:99.9, v/v) C3H4/C3H6 mixture to produce 99.9999 % pure C3H6 with a productivity of 62.0 (or 142.8) mmol g−1. Record removal: A series of metal–organic frameworks with broad types of structures, pore sizes, and functionalities were used to identify UTSA‐200 as the best separating agent for removal of trace C3H4 from C3H4/C3H6 mixtures. The efficiency is mainly attributed to the optimally dynamic pore size to efficiently block the larger C3H6 whilst retaining strong binding sites to selectively take up C3H4, thus producing high‐purity C3H6 (99.9999 %). [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) graphitic carbon nitride (g-C3N4) nanosheets show brilliant application potential in numerous fields. Herein, a membrane with artificial nanopores and self-supporting spacers was fabricated by assembly of 2D g-C3N4 nanosheets in a stack with elaborate structures. In water purification the g-C3N4 membrane shows a better separation performance than commercial membranes. The g-C3N4 membrane has a water permeance of 29 L m−2 h−1 bar−1 and a rejection rate of 87 % for 3 nm molecules with a membrane thickness of 160 nm. The artificial nanopores in the g-C3N4 nanosheets and the spacers between the partially exfoliated g-C3N4 nanosheets provide nanochannels for water transport while bigger molecules are retained. The self-supported nanochannels in the g-C3N4 membrane are very stable and rigid enough to resist environmental challenges, such as changes to pH and pressure conditions. Permeation experiments and molecular dynamics simulations indicate that a novel nanofluidics phenomenon takes place, whereby water transport through the g-C3N4 nanosheet membrane occurs with ultralow friction. The findings provide new understanding of fluidics in nanochannels and illuminate a fabrication method by which rigid nanochannels may be obtained for applications in complex or harsh environments. [ABSTRACT FROM AUTHOR]

Although having shown great promise for efficient gas separation, relevant study of Ti‐MOF membranes remains very scarce, owing to limited Ti source types and uncertain factors which dominate the separation properties. In this work, we pioneered the use of the Ti8(μ2‐O)8(OOCC6H5)16 cluster as the Ti source of MIL‐125 membranes, which led to lower reaction temperature and higher missing‐linker number within the framework and therefore, enhanced CO2/N2 adsorption selectivity. The MIL‐125 membrane prepared by combining single‐mode microwave heating with tertiary growth displayed an ideal CO2/N2 selectivity of 38.7, which ranked the highest among all pristine pure MOF membranes measured under comparable conditions. In addition, the ideal H2/N2 and H2/CH4 selectivity was as high as 64.9 and 40.7, thus showing great promise for versatile utility in gas separation. [ABSTRACT FROM AUTHOR]

For the separation of ethane from ethylene, it remains challenging to target both high C2H6 adsorption and selectivity in a C2H6‐selective material. Herein, we report a reversible solid‐state transformation in a labile hydrogen‐bonded organic framework to generate a new rod‐packing desolvated framework (ZJU‐HOF‐1) with suitable cavity spaces and functional surfaces to optimally interact with C2H6. ZJU‐HOF‐1 thus exhibits simultaneously high C2H6 uptake (88 cm3 g−1 at 0.5 bar and 298 K) and C2H6/C2H4 selectivity (2.25), which are significantly higher than those of most top‐performing materials. Theoretical calculations revealed that the cage‐like cavities and functional sites synergistically "match" better with C2H6 to provide stronger multipoint interactions with C2H6 than C2H4. In combination with its high stability and ultralow water uptake, this material can efficiently capture C2H6 from 50/50 C2H6/C2H4 mixtures in ambient conditions under 60 % RH, providing a record polymer‐grade C2H4 productivity of 0.98 mmol g−1. [ABSTRACT FROM AUTHOR]

Porous materials with d3 electronic configuration open metal sites have been proved to be effective adsorbents for N2 capture and N2/O2 separation. However, the reported materials remain challenging to address the trade‐off between adsorption capacity and selectivity. Herein, we report a robust MOF, MIL‐102Cr, that features two binding sites, can synergistically afford strong interactions for N2 capture. The synergistic adsorption site exhibits a benchmark Qst of 45.0 kJ mol−1 for N2 among the Cr‐based MOFs, a record‐high volumetric N2 uptake (31.38 cm3 cm−3), and highest N2/O2 selectivity (13.11) at 298 K and 1.0 bar. Breakthrough experiments reveal that MIL‐102Cr can efficiently capture N2 from a 79/21 N2/O2 mixture, providing a record 99.99 % pure O2 productivity of 0.75 mmol g−1. In situ infrared spectroscopy and computational modelling studies revealed that a synergistic adsorption effect by open Cr(III) and fluorine sites was accountable for the strong interactions between the MOF and N2. [ABSTRACT FROM AUTHOR]

Protein channels on the biofilm conditionally manipulate ion transport via regulating the distribution of charge residues, making analogous processes on artificial membranes a hot spot and challenge. Here, we employ metal–organic frameworks (MOFs) membrane with charge‐adjustable subnano‐channel to selectively govern ion transport. Various valent ions are binded with crown ethers embedded in the MOF cavity, which act as charged guest to regulate the channels' charge state from the negativity to positivity. Compared with the negatively charged channel, the positive counterpart obviously enhances Li+/Mg2+ selectivity, which benefit from the reinforcement of the electrostatic repulsion between ions and the channel. Meanwhile, theoretical calculations reveal that Mg2+ transport through the more positively charged channel needed to overcome higher entrance energy barrier than that of Li+. This work provides a subtle strategy for ion‐selective transport upon regulating the charge state of insulating membrane, which paves the way for the application like seawater desalination and lithium extraction from salt lakes. [ABSTRACT FROM AUTHOR]

Polycrystalline metal–organic framework (MOF) layers hold great promise as molecular sieve membranes for efficient gas separation. Nevertheless, the high crystallinity tends to cause inter‐crystalline defects/cracks in the nearby crystals, which makes crystalline porous materials face a great challenge in the fabrication of defect‐free membranes. Herein, for the first time, we demonstrate the balance between crystallinity and film formation of MOF membrane through a facile in situ modulation strategy. Monocarboxylic acid was introduced as a modulator to regulate the crystallinity via competitive complexation and thus concomitantly control the film‐forming state during membrane growth. Through adjusting the ratio of modulator acid/linker acid, an appropriate balance between this structural "trade‐off" was achieved. The resulting MOF membrane with moderate crystallinity and coherent morphology exhibits molecular sieving for H2/CO2 separation with selectivity up to 82.5. [ABSTRACT FROM AUTHOR]

Developing hydrogen‐bonded organic frameworks (HOFs) that combine functional sites, size control, and storage capability for targeting gas molecule capture is a novel and challenging venture. However, there is a lack of effective strategies to tune the hydrogen‐bonded network to achieve high‐performance HOFs. Here, a series of HOFs termed as HOF‐ZSTU‐M (M=1, 2, and 3) with different pore structures are obtained by introducing structure‐directing agents (SDAs) into the hydrogen‐bonding network of tetrakis (4‐carboxyphenyl) porphyrin (TCPP). These HOFs have distinct space configurations with pore channels ranging from discrete to continuous multi‐dimensional. Single‐crystal X‐ray diffraction (SCXRD) analysis reveals a rare diversity of hydrogen‐bonding models dominated by SDAs. HOF‐ZSTU‐2, which forms a strong layered hydrogen‐bonding network with ammonium (NH4+) through multiple carboxyl groups, has a suitable 1D "pearl‐chain" channel for the selective capture of propylene (C3H6). At 298 K and 1 bar, the C3H6 storage density of HOF‐ZSTU‐2 reaches 0.6 kg L−1, representing one of the best C3H6 storage materials, while offering a propylene/propane (C3H6/C3H8) selectivity of 12.2. Theoretical calculations and in situ SCXRD provide a detailed analysis of the binding strength of C3H6 at different locations in the pearl‐chain channel. Dynamic breakthrough tests confirm that HOF‐ZSTU‐2 can effectively separate C3H6 from multi‐mixtures. [ABSTRACT FROM AUTHOR]

Ultralow Friction MembranesIn their Communication on page 8974 ff., J. Caro et al. report a water purification membrane composed of 2D g‐C3N4 nanosheets. Self‐supporting spacers and intrinsic and artificial nanopores promote water transport with ultralow friction. [ABSTRACT FROM AUTHOR]

Methane (CH4) enrichment and purification is of great significance for increasing the heating value of unconventional natural gas sources and curtailing its effect on global warming. For a long time, commercial adsorbents for CH4 separation have been hampered by low adsorption capacities, sub‐optimal adsorption selectivities, or slow diffusion rates, which have significantly restricted separation productivity. Herein, we report a facile and green seed‐passaging method to fabricate donut‐like macro–meso–micro hierarchical zeolite K‐Chabazite nanocrystal aggregates. This consecutive seed‐inducing method requires no organic template. By utilizing this unique nanocrystallization technique, the CH4 adsorption capacity, gas diffusion rate, and separation productivity of the resultant material are dramatically increased compared with those of commercially available adsorbents, thus setting a new benchmark in CH4/N2 separation. More importantly, production of this adsorbent can be easily scaled‐up to the order of 100 kg using readily available raw materials in this environmentally friendly synthetic route, enabling potential industrial implementation. [ABSTRACT FROM AUTHOR]

Adsorptive separation of propylene/propane (C3H6/C3H8) mixture is desired for its potential energy saving on replacing currently deployed and energy‐intensive cryogenic distillation. Realizing efficient C3H6/C3H8 separation in the emerging hydrogen‐bonded organic frameworks (HOFs) is very challenging owing to the lack of functional sites for preferential gas binding. By virtue of crystal engineering, we herein report a functionalized HOF (HOF‐16) with free ‐COOH sites for the efficient separation of C3H6/C3H8 mixtures. Under ambient conditions, HOF‐16 shows a significant C3H6/C3H8 uptake difference (by 76 %) and selectivity (5.4) in contrast to other carboxylic acid‐based HOFs. Modeling studies indicate that free ‐COOH groups together with the suitable pore confinement facilitate the recognition and high‐density packing of gas molecules. The separation performance of HOF‐16 was validated by breakthrough experiments. HOF‐16 is stable towards strong acidity and water. [ABSTRACT FROM AUTHOR]

Separation of acetylene from carbon dioxide remains a daunting challenge because of their very similar molecular sizes and physical properties. We herein report the first example of using copper(I)‐alkynyl chemistry within an ultra‐microporous MOF (CuI@UiO‐66‐(COOH)2) to achieve ultrahigh C2H2/CO2 separation selectivity. The anchored CuI ions on the pore surfaces can specifically and strongly interact with C2H2 molecule through copper(I)‐alkynyl π‐complexation and thus rapidly adsorb large amount of C2H2 at low‐pressure region, while effectively reduce CO2 uptake due to the small pore sizes. This material thus exhibits the record high C2H2/CO2 selectivity of 185 at ambient conditions, significantly higher than the previous benchmark ZJU‐74a (36.5) and ATC‐Cu (53.6). Theoretical calculations reveal that the unique π‐complexation between CuI and C2H2 mainly contributes to the ultra‐strong C2H2 binding affinity and record selectivity. The exceptional separation performance was evidenced by breakthrough experiments for C2H2/CO2 gas mixtures. This work suggests a new perspective to functionalizing MOFs with copper(I)‐alkynyl chemistry for highly selective separation of C2H2 over CO2. [ABSTRACT FROM AUTHOR]

Simultaneous removal of trace amounts of propyne and propadiene from propylene is an important but challenging industrial process. We report herein a class of microporous metal–organic frameworks (NKMOF‐1‐M) with exceptional water stability and remarkably high uptakes for both propyne and propadiene at low pressures. NKMOF‐1‐M separated a ternary propyne/propadiene/propylene (0.5 : 0.5 : 99.0) mixture with the highest reported selectivity for the production of polymer‐grade propylene (99.996 %) at ambient temperature, as attributed to its strong binding affinity for propyne and propadiene over propylene. Moreover, we were able to visualize propyne and propadiene molecules in the single‐crystal structure of NKMOF‐1‐M through a convenient approach under ambient conditions, which helped to precisely understand the binding sites and affinity for propyne and propadiene. These results provide important guidance on using ultramicroporous MOFs as physisorbent materials. [ABSTRACT FROM AUTHOR]