High-Efficiency Lithium-Ion Transport in a Porous Coordination Chain-Based Hydrogen-Bonded Framework

Hydrogen-bonded organic frameworks for environmental remediation and energy applications: A bibliometric analysis of research progress and prospects

Hydrogen-bonded organic frameworks (HOFs) are widely used in environmental and energy fields because of their high crystallinity, solution processability, and easy regeneration. Although there have been some reviews focusing on the specific environmental or energy applications of HOFs, a comprehensive research summary and analysis of research trends across the entire field is still lacking. To facilitate the advancement of HOFs, a bibliometric analysis method was used to examine all relevant literature on the subject. Initially, the general bibliometric distribution of the dataset by year, country, institute, reference source, and research focus are determined. Subsequently, the research hotspots covering adsorption, separation, sensing, catalysis, and energy storage are thoroughly explored. To conclude, an analysis of the potential opportunities and obstacles that lie ahead for HOFs is presented, offering a novel perspective to propel their advancement in the fields of environmental remediation and energy utilization.

Engineering 3D Lattice Oxygen Metal-Organic Frameworks for Fast-Charging Quasi-Solid-State Lithium Metal Batteries

Metal-organic frameworks (MOFs) show great promise in composite solid polymer electrolytes by simultaneously immobilizing anions and facilitating cation transport, yet the synergy between these mechanisms remains unclear. To elucidate this interplay, a series of isoreticular indium-based MOFs (InOF-1, MIL-60, and MIL-68(In)) are designed, all featuring identical In-O6 coordination centers while exhibiting systematically varies pore architectures. Among them, MIL-60 stands out by achieving an optimal balance between physical size exclusion and chemical mediation of ion transport. It's precisely engineered 6.5 Å pores effectively block bulky TFSI- anions while allowing the diffusion of lithium ion (Li+)-solvent complexes. Concurrently, its exceptionally high lattice oxygen density (19.97 nm-3, confirmed by density functional theory calculations) forms a 3D fast Li+ conduction network, enabling barrier-free ion hopping. This dual mechanism results in superior electrochemical performance, including an ultrahigh room-temperature Li+ conductivity of 1.11 × 10-3 S cm-1 at 30 °C, an unprecedented Li+ transference number of 0.54, and outstanding cycling stability with 95.2% capacity retention after 1800 cycles at 10 C in LiFePO4||Li cells. This study proposes a new design strategy aligning pore size with Li+ transport sites to optimize ion conduction. MIL-60 exemplifies a promising model for single-ion conductors and guides next-generation solid-state batteries.

Anthraquinone Substituents Regulate the Ion-Transport Sites in iHOFs for Efficient Transport of Alkali-Metal Ions

The designability of crystalline framework materials holds promise for the development of stable solid-state electrolytes with high ionic conductivity. In this study, we present three anthraquinone-based ionic hydrogen-bonded organic frameworks (iHOF-21-23), which possess 2D sandwich-shaped hydrogen-bonding networks. By modulating the anthraquinone substituents, the three iHOFs exhibit distinct ion-transport sites. Specifically, both carbonyls in the structure of iHOF-22 are ion-transport sites, whereas only one carbonyl in each of iHOF-21 and iHOF-23 is, and thus iHOF-22 exhibits higher ionic conductivities. The ionic conductivities of Li+, Na+, and K+ of iHOF-22 at 30 °C are 1.37 × 10-4, 1.14 × 10-4, and 9.76 × 10-5 S cm-1, respectively, which are 16-47% higher than those of iHOF-21 and iHOF-23. The design of the iHOFs for multidimensional ion transport provides valuable insights for the development of solid-state electrolytes for various ion batteries.

Defect-Tailoring Metal-Organic Frameworks for Highly Fast-Charging Quasi-Solid-State Electrolytes Lithium Metal Batteries

Metal-organic frameworks (MOFs) show revolutionary potential in quasi-solid-state electrolytes (QSSEs) designed for high-energy-density batteries, owing to their tunable nanoporous structures and open metal sites (OMSs). However, their application is hindered by insufficient Li+ dissociation and low ionic conductivity, attributed to limited metal active sites. This study employed defect engineering to modulate hafnium-based MOFs, increasing OMS density while optimizing the pore microenvironment. The engineered defects improve the Lewis acid strength of OMSs, driving lithium salt dissociation and establishing strong chemisorption of TFSI- anions. By synergistically optimizing defect density, Lewis acidity, and structural stability, the defect-engineered Hf-MOF-QSSE achieved an ionic conductivity of 1.0 mS cm-1 at 30 °C and delivered a critical current density of 2 mA cm-2, surpassing previously reported MOF-QSSEs, underscoring the pivotal role of defect engineering in electrolyte optimization. Furthermore, Li||LiFePO4 cells exhibited excellent cycling stability and ultrahigh rate capability, retaining 93% of their capacity after 1500 cycles at 10C, while Li||NCM811 cells maintained a specific capacity of 85 mAh g-1 after 600 cycles at 5C.

Anthraquinone substituents modulate ionic hydrogen-bonded organic frameworks to achieve high ionic conductivity for alkali metal ions

Herein, we report two charge-assisted hydrogen-bonded organic frameworks (iHOF-24 and iHOF-25) with 3D/2D hydrogen-bonding networks, which exhibit high ionic conductivity for alkali metal ions. Among them, the conductivity of Li+ is higher than that of Na+ and K+, and the ionic conductivities of Li@iHOF-24 and Li@iHOF-25 at 30 °C were 9.44 × 10-5 and 9.85 × 10-5 S cm-1. This change is attributed to the distance between neighboring carbonyl groups in iHOF-24 and iHOF-25, as well as the radius of the loaded alkali metal ions.

Defect-Modulated MOF Nanochannels for the Quasi-Solid-State Electrolyte of a Dendrite-Free Lithium Metal Battery

Efficient and selective Li+ transport within the nanochannel is essential for high-performance solid-state electrolytes (SSEs) in lithium metal batteries. Introducing Li+ hopping sites into SSEs shows great potential for promoting Li+ transport; however, it typically reduces the Li+ transport nanochannel size, consequently increasing the energy barrier for Li+ transport. Herein, we present a molecular defect strategy for MOFs to introduce Li+ hopping sites and increase the nanochannel size simultaneously as quasi-solid-state electrolytes (QSSEs). Compared with the defect-free Li@UiO-66-based QSSE, the optimized Li@UiO-66-D2-based QSSE exhibits a remarkable 343% enhancement in Li+ conductivity and improved Li+ selectivity. Furthermore, the 9 cm × 6 cm Li|Li@UiO-66-D2|LFP pouch cell exhibits excellent cycling performance with high capacity retention. An in-depth mechanism study has unveiled the significant impact of both hopping sites and nanochannel size on Li+ transport, emphasizing the importance of a molecular defect strategy in enhancing the overall Li+ transport performance of MOF-based QSSEs.

Indirect Construction of Chiral Metal-Organic Frameworks for Enantioselective Luminescence Sensing

ConspectusChiral metal-organic frameworks (MOFs) are promising candidates as luminescent sensing materials for chiral species, which are essential components in modern industries, pharmaceuticals, and biological processes. The discrimination of enantiomers with highly similar physical and chemical properties is crucial because they are often present concurrently in the same system but may feature distinct effects on living matters. While the rapid and precise sensing capabilities of chiral MOFs outshine traditional detection methods for chiral species in daily life, chemical production, and the natural environment, it requires well-matched chemical and electronic structures between MOFs and chiral species. Yet, conventional strategies to construct chiral luminescent MOFs are immensely challenging due to the crystallization difficulties based on low-symmetric building blocks.Recent advancements in MOF chemistry have led to novel pathways for synthesizing chiral MOFs for enantioselective sensing. Compared with direct synthesis using optically pure luminescent ligands, which are usually complex and costly, indirect synthesis has garnered significant attention for reduced costs, simplified synthesis, enhanced material stability, and broad application scope. In the past few years, our group has developed chiral guest ion exchange, chiral coordination modification, and chiral defect engineering for indirectly synthesizing chiral MOFs. The chiral guest ion exchange is cost-effective for introducing chiral ions into MOF pores but can be applied only in charged frameworks. In addition, it also faces limitations in chiral ion availability and the tendency toward chirality loss during the sensing process. Besides, compared with ion exchange, the chiral coordination modification can maintain the chemical stability of chiral MOFs due to the stronger coordination bonds. Still, it requires MOFs with accessible open metal sites that may bind disordered dangling molecules, complicating structural determination. Therefore, specific pathways such as chiral linker installation with dual-end coordination have been developed to afford well-defined crystal structures. While all aforementioned methods may decrease the MOFs' pore sizes to a certain degree, we further developed a chiral defect engineering approach to enlarge pore size and introduce chiral center simultaneously. Such a highly competitive strategy is facile and low-cost and can be expanded to many well-known stable MOFs.In this Account, we delve into the intricate evolution of indirect strategies for constructing chiral MOFs tailored for enantioselective sensing applications. We provide a detailed analysis of the progression and innovation within the field, tracing the development of MOF-based enantioselective luminescence sensors. By systematically reviewing the various synthetic approaches, this work highlights their respective strengths and limitations. Beyond reviewing the state of the art, this Account offers forward-looking insights aiming to inspire the design and development of next-generation chiral luminescent MOFs. These advanced materials hold promise for versatile and impactful applications across enantioselective sensing and beyond.

Hypercrosslinked Metal-Organic Polyhedra Electrolyte with High Transference Number and Fast Conduction of Li Ions

Solid-state electrolytes (SSEs) with high Li-ion transference numbers and fast ionic conductivity are urgently needed for technological innovations in lithium-metal batteries. To promote the dissociation of ion pairs and overcome the mechanical brittleness and interface defects caused by traditional fillers in polymeric electrolytes, we designed and fabricated a cationic hypercrosslinking metal-organic polyhedra (HCMOPs) polymer as SSE. Benefiting a three-component synergistic effect: cationic MOPs, branched polyethyleneimine macromonomer and polyelectrolyte units, the Li-HCMOP electrolyte possesses a high Li-ion conductivity, a high Li-ion transference number and a low activation energy. The LiFePO4/Li battery exhibits high capacity with superior rate performance and cycling stability. Moreover, soluble MOPs serve as high crosslinking nodes to provide excellent mechanical strength for electrolytes and good compatibility with polymers. This work highlights an effective idea of high-performance MOP-based solid-state electrolytes applied in LMBs.

Development of the design and synthesis of metal-organic frameworks (MOFs) - from large scale attempts, functional oriented modifications, to artificial intelligence (AI) predictions

Owing to the exceptional porous properties of metal-organic frameworks (MOFs), there has recently been a surge of interest, evidenced by a plethora of research into their design, synthesis, properties, and applications. This expanding research landscape has driven significant advancements in the precise regulation of MOF design and synthesis. Initially dominated by large-scale synthesis approaches, this field has evolved towards more targeted functional modifications. Recently, the integration of computational science, particularly through artificial intelligence predictions, has ushered in a new era of innovation, enabling more precise and efficient MOF design and synthesis methodologies. The objective of this review is to provide readers with an extensive overview of the development process of MOF design and synthesis, and to present visions for future developments.

Designing Cooperative Ion Transport Pathway in Ultra-Thin Solid-State Electrolytes toward Practical Lithium Metal Batteries

Solid polymer electrolytes (SPEs) are promising for high-energy-density solid-state Li metal batteries due to their decent flexibility, safety, and interfacial stability. However, their development was seriously hindered by the interfacial instability and limited conductivity, leading to inferior electrochemical performance. Herein, we proposed to design ultra-thin solid-state electrolyte with long-range cooperative ion transport pathway to effectively increase the ionic conductivity and stability. The impregnation of PVDF-HFP inside pores of fluorinated covalent organic framework (CF3-COF) can disrupt its symmetry, rendering rapid ion transportation and inhibited anion immigration. The functional groups of CF3-COF can interact with PVDF-HFP to form fast Li+ transport channels, which enables the uniform and confined Li+ conduction within the electrolyte. The introduction of CF3-COF also enhances the mechanical strength and flexibility of SPEs, as well as ensures homogeneous Li deposition and inhibited dendrite growth. Hence, a remarkably high conductivity of 1.21×10-3 S cm-1 can be achieved. Finally, the ultra-thin SPEs with an extremely long cycle life exceed 9000 h can be obtained while the NCM523/Li pouch cell demonstrates a high capacity of 760 mAh and 96 % capacity retention after cycling, holding great promises to be utilized for practical solid-state Li metal batteries.

Enhancing the performance of ionic conductivity for solid-state electrolytes: an effective strategy of injecting lithium ions within anionic metal-organic frameworks

Metal-organic frameworks (MOFs) are considered as potential solid-state electrolyte (SSE) materials due to their structural diversity and porosity. Adding lithium ions into the anionic frameworks of MOFs and then realizing single-ion transport is an efficient way to enhance the performance of ionic conductivity of SSE materials. Herein, an ionotropic MOF (Li+[Cu-BTC]-) with lithium ions in the pores of the lattice was synthesized through an ion exchange strategy, which exhibits outstanding lithium ionic conducting properties over a wide temperature range (ionic conductivity: 0.11-2.96 × 10-3 S cm-1 in the temperature range of -40 to 100 °C). The strategy of injecting Li+ within anionic metal-organic frameworks provides a new opportunity for exploring advanced SSEs.

Hydrogen-Bonded Organic Frameworks-based Electrolytes with Controllable Hydrogen Bonding Networks for Solid-State Lithium Batteries

The lack of stable solid-state electrolytes (SSEs) with high-ionic conductivity and the rational design of electrode/electrolyte interfaces remains challenging for solid-state lithium batteries. Here, for the first time, a high-performance solid-state lithium-oxygen (Li-O2) battery is developed based on the Li-ion-conducted hydrogen-bonded organic framework (LHOF) electrolyte and the HOF-DAT@CNT composite cathode. Benefiting from the abundant dynamic hydrogen bonding network in the backbone of LHOF-DAT SSEs, fast Li+ ion transport (2.2×10-4 S cm-1), a high Li+ transference number (0.88), and a wide electrochemical window of 5.05 V are achieved. Symmetric batteries constructed with LHOF-DAT SSEs exhibit a stably cycled duration of over 1400 h with uniform deposition, which mainly stems from the jumping sites that promote a uniformly high rate of Li+ flux and the hydrogen-bonding network structure that can relieve the structural changes during Li+ transport. LHOF-DAT SSEs-based Li-O2 batteries exhibit high specific capacity (10335 mAh g-1), and stable cycling life up to 150 cycles. Moreover, the solid-state lithium metal battery with LHOF-DAT SSEs endow good rate capability (129.6 mAh g-1 at 0.5 C), long-term discharge/charge stability (210 cycles). The design of LHOF-DAT SSEs opens an avenue for the development of novel SSEs-based solid-state lithium batteries.

Constructing Donor-Acceptor-Linked COFs Electrolytes to Regulate Electron Density and Accelerate the Li+ Migration in Quasi-Solid-State Battery

Regulation the electronic density of solid-state electrolyte by donor-acceptor (D-A) system can achieve highly-selective Li+ transportation and conduction in solid-state Li metal batteries. This study reports a high-performance solid-state electrolyte thorough D-A-linked covalent organic frameworks (COFs) based on intramolecular charge transfer interactions. Unlike other reported COF-based solid-state electrolyte, the developed concept with D-A-linked COFs not only achieves electronic modulation to promote highly-selective Li+ migration and inhibit Li dendrite, but also offers a crucial opportunity to understand the role of electronic density in solid-state Li metal batteries. The introduced strong electronegativity F-based ligand in COF electrolyte results in highly-selective Li+ (transference number 0.83), high ionic conductivity (6.7 × 10-4 S cm-1), excellent cyclic ability (1000 h) in Li metal symmetric cell and high-capacity retention in Li/LiFePO4 cell (90.8% for 300 cycles at 5C) than substituted C- and N-based ligands. This is ascribed to outstanding D-A interaction between donor porphyrin and acceptor F atoms, which effectively expedites electron transferring from porphyrin to F-based ligand and enhances Li+ kinetics. Consequently, we anticipate that this work creates insight into the strategy for accelerating Li+ conduction in high-performance solid-state Li metal batteries through D-A system.

Porous Organic Framework Materials (MOF, COF, and HOF) as the Multifunctional Separator for Rechargeable Lithium Metal Batteries

The separator is an important component in batteries, with the primary function of separating the positive and negative electrodes and allowing the free passage of ions. Porous organic framework materials have a stable connection structure, large specific surface area, and ordered pores, which are natural places to store electrolytes. And these materials with specific functions can be designed according to the needs of researchers. The performance of porous organic framework-based separators used in rechargeable lithium metal batteries is much better than that of polyethylene/propylene separators. In this paper, the three most classic organic framework materials (MOF, COF, and HOF) are analyzed and summarized. The applications of MOF, COF, and HOF separators in lithium-sulfur batteries, lithium metal anode, and solid electrolytes are reviewed. Meanwhile, the research progress of these three materials in different fields is discussed based on time. Finally, in the conclusion, the problems encountered by MOF, COF, and HOF in different fields as well as their future research priorities are presented. This review will provide theoretical guidance for the design of porous framework materials with specific functions and further stimulate researchers to conduct research on porous framework materials.

In Situ Constructing Metal-Organic Complex Interface Layer Using Biomolecule Enabling Stabilize Zn Anode

Aqueous zinc-ion batteries (ZIBs) are considered as a promising candidate for next-generation large-scale energy storage due to their high safety, low cost, and eco-friendliness. Unfortunately, commercialization of ZIBs is severely hindered owing to rampant dendrite growth and detrimental side reactions on the Zn anode. Herein, inspired by the metal-organic complex interphase strategy, the authors apply adenosine triphosphate (ATP) to in situ construct a multifunctional film on the metal Zn surface (marked as ATP@Zn) by a facile etching method. The ATP-induced interfacial layer enhances lipophilicity, promoting uniform Zn2+ flux and further homogenizing Zn deposition. Meanwhile, the functional interlayer improves the anticorrosion ability of the Zn anode, effectively suppressing corrosion and hydrogen evolution. Consequently, the as-prepared ATP@Zn anode in the symmetric cell exhibits eminent plating/stripping reversibility for over 2800 h at 5.0 mA cm-2 and 1 mAh cm-2. Furthermore, the assembled ATP@Zn||MnO2 full cells are investigated to evaluate practical feasibilities. This work provides an efficient and simple strategy to prepare stabilized Zn anode toward high-performance ZIBs.

Postsynthetic Modification of Hydrogen-Bonded Frameworks

Hydrogen-bonded frameworks have garnered significant attention due to their flexible structures with tailored porosity, making them a promising class of porous framework materials. However, the direct synthesis of hydrogen-bonded frameworks with specific functions is highly challenging due to the unpredictable formation of hydrogen-bonded frameworks. In response, postsynthetic modification has emerged as a potent strategy to imbue desired functions into hydrogen-bonded frameworks. Recent advances have demonstrated the effectiveness of postsynthetic modification in hydrogen-bonded frameworks for studying their mechanical, luminescent, electrochemical, and chiral properties. In this concept, we comprehensively summarize the methodologies and outcomes of postsynthetic modification to hydrogen-bonded frameworks, providing a highlight of this exciting research area.

Ultralong Cycling and Interfacial Regulation of Bilayer Heterogeneous Composite Solid-State Electrolytes in Lithium Metal Batteries

Under the background of "carbon neutral", lithium-ion batteries (LIB) have been widely used in portable electronic devices and large-scale energy storage systems, but the current commercial electrolyte is mainly liquid organic compounds, which have serious safety risks. In this paper, a bilayer heterogeneous composite solid-state electrolyte (PLPE) was constructed with the 3D LiX zeolite nanofiber (LiX-NF) layer and in-situ interfacial layer, which greatly extends the life span of lithium metal batteries (LMB). LiX-NF not only offers a continuous fast path for Li+, but also zeolite's Lewis acid-base interaction can immobilize large anions, which significantly improves the electrochemical performance of the electrolyte. In addition, the in-situ interfacial layer at the electrode-electrolyte interface can effectively facilitate the uniform deposition of Li+ and inhibit the growth of lithium dendrites. As a result, the Li/Li battery assembled with PLPE can be stably cycled for more than 2500 h at 0.1 mA cm-2. Meanwhile, the initial discharge capacity of the LiFePO4/PLPE/Li battery can be 162.43 mAh g-1 at 0.5 C, and the capacity retention rate is 82.74% after 500 cycles. These results emphasize that this bilayer heterogeneous composite solid-state electrolyte has distinct properties and shows excellent potential for application in LMB.

Organizing Photosensitive and Photothermal Single-Sites Uniformly in a Trimetallic Metal-Organic Framework for Efficient Photocatalytic Hydrogen Evolution

Effective combination of the photosensitivity and photothermal property in photocatalyst is vital to achieve the maximum light utilization for superior photocatalytic efficiency. Herein, this work successfully organizes photosensitive Cd-NS single-sites and photothermal Ni-NS single-sites uniformly at a molecular level within a tailored trimetallic metal-organic framework. The optimized Ho6-Cd0.76Ni0.24-NS exhibits a superior photocatalytic hydrogen evolution rate of 40.06 mmol g-1 h-1 under visible-light irradiation and an apparent quantum efficiency of 29.37% at 420 nm without using cocatalysts or photosensitizers. A systematical mechanism study reveals that the uniformly organized photosensitive and photothermal single-sites have synergistic effect, which form ultrashort pathways for efficient transport of photoinduced electrons, suppress the recombination of photogenerated charge carriers, hence promote the hydrogen evolution activity. This work provides a promising approach for organizing dual-functional single-sites uniformly in photocatalyst for high-performance photocatalytic activity.

Facile synthesis of a three-dimensional Ln-MOF@FCNT composite for the fabrication of a symmetric supercapacitor device with ultra-high energy density: overcoming the energy storage barrier

In order to quench the thirst for efficient energy storage devices, a novel praseodymium-based state-of-the-art three-dimensional metal-organic framework (MOF), {[Pr(pdc)2]Me2NH2}n (YK-1), has been synthesized by using a simple solvothermal method employing a readily available ligand. YK-1 was characterised by single-crystal XRD and crystallographic analysis. The electrochemical measurements of YK-1 show that it exhibits a specific capacitance of 363.5 F g-1 at a current density of 1.5 A g-1 with 83.8% retention after 5000 cycles. In order to enhance its electrochemical performance for practical application, two composites of YK-1 with graphene oxide (GO) and functionalised multi-walled carbon nanotubes (FCNTs), namely YK-1@GO and YK-1@FCNT, were fabricated by employing a facile ultrasonication technique. The as-synthesized MOF and the composites were characterized by PXRD, FTIR, SEM, and TEM techniques. YK-1@GO and YK-1@FCNT offer enhanced specific capacitances of 488.2 F g-1 and 730.2 F g-1 at the same current density with 93.8% and 97.7% capacity retention after 5000 cycles, respectively (at 16 A g-1). Fascinated by the outstanding results shown by YK-1@FCNT, a symmetric supercapacitor device (SSC) based on it was fabricated. The assembled SSC achieved a remarkable energy density (87.6 W h kg-1) and power density (750.2 W kg-1) at a current density of 1 A g-1, along with very good cycling stability of 91.4% even after 5000 GCD cycles. The SSC device was able to power up several LED lights and even operated a DC brushless fan for a significant amount of time. To the best of our knowledge, the assembled SSC device exhibits the highest energy density among the MOF composite-based SSCs reported so far.

Supramolecular polynuclear clusters sustained cubic hydrogen bonded frameworks with octahedral cages for reversible photochromism

Developing supramolecular porous crystalline frameworks with tailor-made architectures from advanced secondary building units (SBUs) remains a pivotal challenge in reticular chemistry. Particularly for hydrogen-bonded organic frameworks (HOFs), construction of geometrical cavities through secondary units has been rarely achieved. Herein, a body-centered cubic HOF (TCA_NH4) with octahedral cages was constructed by a C3-symmetric building block and NH4+ node-assembled cluster (NH4)4(COOH)8(H2O)2 that served as supramolecular secondary building units (SSBUs), akin to the polynuclear SBUs in reticular chemistry. Specifically, the octahedral cages could encapsulate four homogenous haloforms including CHCl3, CHBr3, and CHI3 with truncated octahedron configuration. Crystallographic evidence revealed the cages served as spatially-confined nanoreactors, enabling fast, broadband photochromic effect associated with the reversible photo/thermal transformation between encapsulated CHI3 and I2. Overall, this work provides a strategy by shaping SSBUs to expand the framework topology of HOFs and a prototype of hydrogen-bonded nanoreactors to accommodate reversible photochromic reactions.

Confinement of p-Xylene in the Pores of a Bilanthanide Metal-Organic Framework for Highly Selective Recognition

The rapid and accurate sensing of p-xylene, an essential raw material with a multi-billion-dollar market, in xylene mixture is of great significance in industry; however, the highly similar molecular structures, energy levels, and spectral characteristics of xylene isomers make the selective recognition extremely challenging. Metal-organic frameworks (MOFs) exhibiting tailorable pores and potential binding sites provide prospects for xylene sensing but a comprehensive understanding of the pore effect is still elusive, primarily due to the intricacies involved in the sensing process. Herein, we reported a robust bilanthanide MOF NKU-999-EuTb with precisely engineered pores to accommodate p-xylene, of which the binding sites were confirmed by single crystal X-ray diffraction and dynamic magnetic susceptibilities. NKU-999-EuTb exhibits high-performance in selective recognition for p-xylene towards its isomers. Through a systematical study, it was revealed that absorbing p-xylene into the pores governs the sensing performance. This work provides insights for developing advanced sensing materials for complex isomers.

A Review on Covalent Organic Frameworks as Artificial Interface Layers for Li and Zn Metal Anodes in Rechargeable Batteries

Li and Zn metals are considered promising negative electrode materials for the next generation of rechargeable metal batteries because of their non-toxicity and high theoretical capacity. However, the uneven deposition of metal ions (Li+ , Zn2+ ) and the uncontrolled growth of dendrites result in poor electrochemical stability, unsatisfactory cycle life, and rapid capacity decay of batteries assembled with Li and Zn electrodes. Owing to the unique internal directional channels and abundant redox active sites of covalent organic frameworks (COFs), they can be used to promote uniform deposition of metal ions during stripping/electroplating through interface modification strategies, thereby inhibiting dendrite growth. COFs provide a new perspective in addressing the challenges faced by the anodes of Li metal batteries and Zn ion batteries. This article discusses the stability and types of COFs, and summarizes some novel COF synthesis methods. Additionally, it reviews the latest progress and optimization methods of using COFs for metal anodes to improve battery performance. Finally, the main challenges faced in these areas are discussed. This review will inspire future research on metal anodes in rechargeable batteries.

Polydopamine-Induced Metal-Organic Framework Network-Enhanced High-Performance Composite Solid-State Electrolytes for Dendrite-Free Lithium Metal Batteries

Due to the high safety, flexibility, and excellent compatibility with lithium metals, composite solid-state electrolytes (CSEs) are the best candidates for next-generation lithium metal batteries, and the construction of fast and uniform Li+ transport is a critical part of the development of CSEs. In this paper, a stable three-dimensional metal-organic framework (MOF) network was obtained using polydopamine as a medium, and a high-performance CSE reinforced by the three-dimensional MOF network was constructed, which not only provides a continuous channel for Li+ transport but also restricts large anions and releases more mobile Li+ through a Lewis acid-base interaction. This strategy endows our CSEs with an ionic conductivity (7.1 × 10-4 S cm-1 at 60 °C), a wide electrochemical window (5.0 V), and a higher Li+ transfer number (0.54). At the same time, the lithium symmetric batteries can be stably cycled for 2000 h at 0.1 mA cm-2, exhibiting excellent electrochemical stability. The LiFePO4/Li cells have a high initial discharge specific capacity of 153.9 mAh g-1 at 1C, with a capacity retention of 80% after 915 cycles. This paper proposes an approach for constructing three-dimensional MOF network-enhanced CSEs, which provides insights into the design and development of MOFs for the positive effects of high-performance CSEs.

Palygorskite-Derived Ternary Fluoride with 2D Ion Transport Channels for Ampere Hour-Scale Li-S Pouch Cell with High Energy Density

Although various excellent electrocatalysts/adsorbents have made notable progress as sulfur cathode hosts on the lithium-sulfur (Li-S) coin-cell level, high energy density (WG ) of the practical Li-S pouch cells is still limited by inefficient Li-ion transport in the thick sulfur cathode under low electrolyte/sulfur (E/S) and negative/positive (N/P) ratios, which aggravates the shuttle effect and sluggish redox kinetics. Here a new ternary fluoride MgAlF5 ·2H2 O with ultrafast ion conduction-strong polysulfides capture integration is developed. MgAlF5 ·2H2 O has an inverse Weberite-type crystal framework, in which the corner-sharing [AlF6 ]-[MgF4 (H2 O)2 ] octahedra units extend to form two-dimensional Li-ion transport channels along the [100] and [010] directions, respectively. Applied as the cathode sulfur host, the MgAlF5 ·2H2 O lithiated by LiTFSI (lithium salt in Li-S electrolyte) acts as a fast ionic conductor to ensure efficient Li-ion transport to accelerate the redox kinetics under high S loadings and low E/S and N/P. Meanwhile, the strong polar MgAlF5 ·2H2 O captures polysulfides by chemisorption to suppress the shuttle effect. Therefore, a 1.97 A h-level Li-S pouch cell achieves a high WG of 386 Wh kg-1 . This work develops a new-type ionic conductor, and provides unique insights and new hosts for designing practical Li-S pouch cells.

Hydrogen-Bonding Assembly Meets Anion Coordination Chemistry: Framework Shaping and Polarity Tuning for Xenon/Krypton Separation

Hybrid hydrogen-bonded (H-bonded) frameworks built from charged components or metallotectons offer diverse guest-framework interactions for target-specific separations. We present here a study to systematically explore the coordination chemistry of monovalent halide anions, i.e., F- , Cl- , Br- , and I- , with the aim to develop hybrid H-bond synthons that enable the controllable construction of microporous H-bonded frameworks exhibiting fine-tunable surface polarity within the adaptive cavities for realistic xenon/krypton (Xe/Kr) separation. The spherical halide anions, especially Cl- , Br- , and I- , are found to readily participate in the charge-assisted H-bonding assembly with well-defined coordination behaviors, resulting in robust frameworks bearing open halide anions within the distinctive 1D pore channels. The activated frameworks show preferential binding towards Xe (IAST Xe/Kr selectivity ca. 10.5) because of the enhanced polarizability and the pore confinement effect. Specifically, dynamic column Xe/Kr separation with a record-high separation factor (SF=7.0) among H-bonded frameworks was achieved, facilitating an efficient Xe/Kr separation in dilute, CO2 -containing gas streams exactly mimicking the off-gas of spent nuclear fuel (SNF) reprocessing.

Promoted Photocatalytic Hydrogen Evolution by Tuning the Electronic State of Copper Sites in Metal-Organic Supramolecular Assemblies

The electronic state in terms of charge and spin of metal sites is fundamental to govern the catalytic activity of a photocatalyst. Herein, we show that modulation of the electronic states of Cu sites, without changing the coordination environments, of two metal-organic supramolecular assemblies based on π⋅⋅⋅π stacking can significantly improve photocatalytic activity. The use of these heterogeneous photocatalysts, without using noble metal cocatalysts, resulted in an increase of the hydrogen production rate from 522 to 3620 μmol h-1  g-1 . A systematical analysis revealed that the charge density and spin density of the metal centers are efficiently modulated via the modulation of the coordination fields around active copper (II) centers by the variation of the non-coordination groups of terminal ligands, leading to the significant enhancement of photocatalytic activity. This work provides an insight into the electronic state of active metal centers for designing high-performance photocatalysts.

A Bifunctional Coordination-Chain-Based Hydrogen-Bonded Framework for Quantitative Enantioselective Sensing

Enantioselective sensing is highly crucial and challenging due to the highly similar physical/chemical properties of enantiomers which may have different chemical impact on organism. Luminescent coordination compounds have attracted great attention as sensing materials based on their controllable chemical and electric structures that can be highly matched with the targeted species. To achieve high-performance enantioselective sensing, the direct synthesis of chiral and luminescent bifunctional coordination compounds is a rational way but highly challenging due to the price and synthesis difficulty. Herein, an anionic coordination-chain-based hydrogen-bonded framework was applied as a host to accommodate chiral and luminescent centers via a facile cation exchange reaction, affording a bifunctional framework that possesses enantioselective sensing properties for the mixture of enantiomers. This study paves a pathway for constructing multifunctional coordination chain-based hydrogen-bonded frameworks for rapidly enantioselective sensing function.

Boosting the Lithium-Ion Transport Kinetics of Sn-Based Coordination Polymers through Ligand Aromaticity Manipulation

Tin-based compounds are promising anode materials for lithium-ion batteries owing to their low charge/discharge voltage and high theoretical capacity but are plagued by both huge volume expansion during cycling and complex synthetic procedures. Constructing a coordination network between Sn and the lithium-active organic matrix can effectively relieve the volume expansion and increase the lithium storage active site utilization. Herein, we report a facile method to prepare two one-dimensional Sn-based coordination polymers [Sn(Hcta)]n (1) and [Sn(Hbtc)]n (2) (H3cta = 1,3,5-cyclohexanetricarboxylic acid, H3btc = 1,3,5-benzenetricarboxylic acid) for lithium storage, which differ only in the aromaticity of the ligand. 2 with an aromatic ligand provided a reversible capacity of 833 mAh g-1 at 200 mA g-1 over 160 cycles, higher than that of 1 without an aromatic ligand due to the quick charge transfer. The reversible lithium storage reactions of metal centers and organic ligands and the volume expansion rate of Sn-based coordination polymers during cycling were studied by detailed characterization and density functional theory (DFT) calculations. This research revealed that the structural factor of ligand aromaticity in these Sn-based coordination polymers boosted the utilization of active sites and rapid charge transfer, offering a coordination chemistry strategy for the design and synthesis of advanced anode materials.