The realization of porous materials for highly selective separation of acetylene (C2H2) from various other gases (e.g., carbon dioxide and ethylene) by adsorption is of prime importance but ...challenging in the petrochemical industry. Herein, a chemically stable Hofmann‐type metal−organic framework (MOF), Co(pyz)Ni(CN)4 (termed as ZJU‐74a), that features sandwich‐like binding sites for benchmark C2H2 capture and separation is reported. Gas sorption isotherms reveal that ZJU‐74a exhibits by far the record C2H2 capture capacity (49 cm3 g−1 at 0.01 bar and 296 K) and thus ultrahigh selectivity for C2H2/CO2 (36.5), C2H2/C2H4 (24.2), and C2H2/CH4 (1312.9) separation at ambient conditions, respectively, of which the C2H2/CO2 selectivity is the highest among all the robust MOFs reported so far. Theoretical calculations indicate that the oppositely adjacent nickel(II) centers together with cyanide groups from different layers in ZJU‐74a can construct a sandwich‐type adsorption site to offer dually strong and cooperative interactions for the C2H2 molecule, thus leading to its ultrahigh C2H2 capture capacity and selectivities. The exceptional separation performance of ZJU‐74a is confirmed by both simulated and experimental breakthrough curves for 50/50 (v/v) C2H2/CO2, 1/99 C2H2/C2H4, and 50/50 C2H2/CH4 mixtures under ambient conditions.
A chemically stable Hofmann‐type metal−organic framework is realized for benchmark acetylene capture capacity and separation, mainly attributed to the unique sandwich‐like binding environments constructed by the oppositely adjacent open metal centers and cyanide groups from the two different Ni(CN)42− building units, thus affording a record‐high acetylene uptake at 0.01 bar and very high selectivities for acetylene‐related separation applications.
Wireless sensor networks (WSNs) are extensively adopted for remote monitoring and tracking scenarios, such as battlefield surveillance, target detection and tracking, traffic condition detection, ...power system monitoring and health monitoring, thanks to their promising benefits in terms of flexibility, reliability and cost-effectiveness. However, some critical WSN applications, such as intelligent transportation and smart grid monitoring, have stringent requirements in terms of resource budget and security. This paper provides a survey of the trending resource-efficient and secure techniques currently used with distributed estimation algorithms over WSNs. Recent progresses on these two major research trends are reviewed, respectively, for WSN-based monitoring systems. More specifically, the first part of the survey covers the state-of-the-art in resource-efficient distributed state estimation. The main results along this line of research are classified into protocol-based scheduling, static event-triggered scheduling, dynamic event-triggered scheduling and stochastic event-triggered scheduling. Then, in the second part, the latest results on secure distributed state estimation are reviewed, where secure distributed state estimation under data integrity attacks and data available attacks, and distributed attack detection are examined, respectively. Finally, several challenging issues in the context of distributed state estimation are discussed for potential future research.
Despite wide applications of bimetallic electrocatalysis in oxygen evolution reaction (OER) owing to their superior performance, the origin of the improved performance remains elusive. The underlying ...mechanism was explored by designing and synthesizing a series of stable metal–organic frameworks (MOFs: NNU‐21–24) based on trinuclear metal carboxylate clusters and tridentate carboxylate ligands. Among the examined stable MOFs, NNU‐23 exhibits the best OER performance; particularly, compared with monometallic MOFs, all the bimetallic MOFs display improved OER activity. DFT calculations and experimental results demonstrate that introduction of the second metal atom can improve the activity of the original atom. The proposed model of bimetallic electrocatalysts affecting their OER performance can facilitate design of efficient bimetallic catalysts for energy storage and conversion, and investigation of the related catalytic mechanisms.
An iron atom in an Fe3 cluster is replaced by a second metal to form Fe2M clusters, which can serve as nodes to bridge with organic ligands and construct stable bimetallic MOFs. The introduction of the second metal atom can improve the activity of the original atom and thus improve the oxygen evolution reaction performance of electrocatalysts.
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.
A rod‐packing microporous hydrogen‐bonding framework with functional surfaces and suitable cavity spaces for C2H6 uptake exhibited simultaneously high capacity and C2H6/C2H4 selectivity (see picture). The excellent C2H6/C2H4 separation occurred with record‐high C2H4 productivity of 0.98 mmol g−1 under high humidity and ambient conditions.
Intertwining quantum order and non-trivial topology is at the frontier of condensed matter physics1–4. A charge-density-wave-like order with orbital currents has been proposed for achieving the ...quantum anomalous Hall effect5,6 in topological materials and for the hidden phase in cuprate high-temperature superconductors7,8. However, the experimental realization of such an order is challenging. Here we use high-resolution scanning tunnelling microscopy to discover an unconventional chiral charge order in a kagome material, KV3Sb5, with both a topological band structure and a superconducting ground state. Through both topography and spectroscopic imaging, we observe a robust 2 × 2 superlattice. Spectroscopically, an energy gap opens at the Fermi level, across which the 2 × 2 charge modulation exhibits an intensity reversal in real space, signalling charge ordering. At the impurity-pinning-free region, the strength of intrinsic charge modulations further exhibits chiral anisotropy with unusual magnetic field response. Theoretical analysis of our experiments suggests a tantalizing unconventional chiral charge density wave in the frustrated kagome lattice, which can not only lead to a large anomalous Hall effect with orbital magnetism, but also be a precursor of unconventional superconductivity.An unconventional chiral charge order is observed in a kagome superconductor by scanning tunnelling microscopy. This charge order has unusual magnetic tunability and intertwines with electronic topology.
A kagome lattice naturally features Dirac fermions, flat bands and van Hove singularities in its electronic structure. The Dirac fermions encode topology, flat bands favour correlated phenomena such ...as magnetism, and van Hove singularities can lead to instabilities towards long-range many-body orders, altogether allowing for the realization and discovery of a series of topological kagome magnets and superconductors with exotic properties. Recent progress in exploring kagome materials has revealed rich emergent phenomena resulting from the quantum interactions between geometry, topology, spin and correlation. Here we review these key developments in this field, starting from the fundamental concepts of a kagome lattice, to the realizations of Chern and Weyl topological magnetism, to various flat-band many-body correlations, and then to the puzzles of unconventional charge-density waves and superconductivity. We highlight the connection between theoretical ideas and experimental observations, and the bond between quantum interactions within kagome magnets and kagome superconductors, as well as their relation to the concepts in topological insulators, topological superconductors, Weyl semimetals and high-temperature superconductors. These developments broadly bridge topological quantum physics and correlated many-body physics in a wide range of bulk materials and substantially advance the frontier of topological quantum matter.
Lattice geometry, topological electron behaviour and the competition between different possible ground states all play a role in determining the properties of materials with a kagome lattice ...structure. In particular, the compounds KV3Sb5, CsV3Sb5 and RbV3Sb5 all feature a kagome net of vanadium atoms. These materials have recently been shown to exhibit superconductivity at low temperature and an unusual charge order at high temperature, revealing a connection to the underlying topological nature of the band structure. We highlight these discoveries, place them in the context of wider research efforts in topological physics and superconductivity, and discuss the open problems for this field.Superconductivity and ordered states formed by interactions—both of which could be unconventional—have recently been observed in a family of kagome materials.
Layered kagome-lattice 3d transition metals are emerging as an exciting platform to explore the frustrated lattice geometry and quantum topology. However, the typical kagome electronic bands, ...characterized by sets of the Dirac-like band capped by a phase-destructive flat band, have not been clearly observed, and their orbital physics are even less well investigated. Here, we present close-to-textbook kagome bands with orbital differentiation physics in CoSn, which can be well described by a minimal tight-binding model with single-orbital hopping in Co kagome lattice. The capping flat bands with bandwidth less than 0.2 eV run through the whole Brillouin zone, especially the bandwidth of the flat band of out-of-plane orbitals is less than 0.02 eV along Γ-M. The energy gap induced by spin-orbit interaction at the Dirac cone of out-of-plane orbitals is much smaller than that of in-plane orbitals, suggesting orbital-selective character of the Dirac fermions.
Severe dendrite growth and high‐level activity of the lithium metal anode lead to a short life span and poor safety, seriously hindering the practical applications of lithium metal batteries. With a ...trisalt electrolyte design, an F‐/N‐containing inorganics–rich solid electrolyte interphase on a lithium anode is constructed, which is electrochemically and thermally stable over long‐term cycles and safety abuse conditions. As a result, its Coulombic efficiency can be maintained over 98.98% for 400 cycles. An 85.0% capacity can be retained for coin‐type full cells with a 3.14 mAh cm−2 LiNi0.5Co0.2Mn0.3O2 cathode after 200 cycles and 1.0 Ah pouch‐type full cells with a 4.0 mAh cm−2 cathode after 72 cycles. During the thermal runaway tests of a cycled 1.0 Ah pouch cell, the onset and triggering temperatures were increased from 70.8 °C and 117.4 °C to 100.6 °C and 153.1 °C, respectively, indicating a greatly enhanced safety performance. This work gives novel insights into electrolyte and interface design, potentially paving the way for high‐energy‐density, long‐life‐span, and thermally safe lithium metal batteries.
An F‐/N‐containing inorganics‐rich solid electrolyte interphase is constructed, which is electrochemically and thermally stable during the long‐term cycles and safety abuse conditions. More than 6 times longer cycles compared with routine cells are achieved in 1.0 Ah pouch‐type cells. The onset and triggering temperatures during the thermal runaway are increased from 70.8 and 117.4 to 100.6 and 153.1 °C, respectively.
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