Bulk-Phase Reconstruction Enables Robust Zinc Metal Anodes for Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries are inherently safe, but the severe dendrite growth and corrosion reaction on zinc anodes greatly hinder their practical applications. Most of the strategies for zinc anode modification refer to the research of lithium metal anodes on surface regulation without considering the intrinsic mechanisms of zinc anode. Herein, we first point out that surface modification cannot permanently protect zinc anodes due to the unavoidable surface damage during the stripping process by solid–liquid conversion. A bulk-phase reconstruction strategy is proposed to introduce abundant zincophilic sites both on the surface and inside the commercial zinc foils. The bulk-phase reconstructed zinc foil anodes exhibit uniform surfaces with high zincophilicity even after deep stripping, significantly improving the resistance to dendrite growth and side reactions. Our proposed strategy suggests a promising direction for the development of dendrite-free metal anodes for practical rechargeable batteries with high sustainability.     

Co-Intercalation of Dual Charge Carriers in Metal-Ion-Confining Layered Vanadium Oxide Nanobelts for Aqueous Zinc-Ion Batteries

Vanadium-based oxides with high theoretical specific capacities and open crystal structures are promising cathodes for aqueous zinc-ion batteries (AZIBs). In this work, the confined synthesis can insert metal ions into the interlayer spacing of layered vanadium oxide nanobelts without changing the original morphology. Furthermore, we obtain a series of nanomaterials based on metal-confined nanobelts, and describe the effect of interlayer spacing on the electrochemical performance. The electrochemical properties of the obtained Al_2.65V₆O₁₃ ⋅ 2.07H₂O as cathodes for AZIBs are remarkably improved with a high initial capacity of 571.7 mAh ⋅ g⁻¹ at 1.0 A g⁻¹. Even at a high current density of 5.0 A g⁻¹, the initial capacity can still reach 205.7 mAh g⁻¹, with a high capacity retention of 89.2 % after 2000 cycles. This study demonstrates that nanobelts confined with metal ions can significantly improve energy storage applications, revealing new avenues for enhancing the electrochemical performance of AZIBs.     

Rapidly Synthesized Single-Ion Conductive Hydrogel Electrolyte for High-Performance Quasi-Solid-State Zinc-ion Batteries

Single-ion conductive electrolytes can largely eliminate electrode polarization, reduce the proportion of anion migration and inhibit side reactions in batteries. However, they usually suffer from insufficient ion conductivity due to the strong interaction between cations and cationic receptors. Here we report an ultrafast light-responsive covalent organic frameworks (COF) with sulfonic acid groups modification as the acrylamide polymerization initiator. Benefiting from the reduced electrostatic interaction between Zn²⁺ and sulfonic acid groups through solvation effects, the as-prepared COF-based hydrogel electrolyte (TCOF-S-Gel) receives an ion conductivity of up to 27.2 mS/cm and Zn²⁺ transference number of up to 0.89. In addition, sufficient hydrogen bonds endow the single-ion conductive TCOF-S-Gel electrolyte to have good water retention and superb mechanical properties. The assembled Zn||TCOF-S-Gel||MnO₂ full zinc-ion battery exhibits high discharge capacity (248 mAh/g at 1C), excellent rate capability (90 mAh/g at 10C) and superior cycling performance. These enviable results enlist the instantaneously photocured TCOF-S-Gel electrolyte to be qualified to large-scaled flexible high-performance quasi-solid-state zinc-ion batteries.     

Redox-Bipolar Polyimide Two-Dimensional Covalent Organic Framework Cathodes for Durable Aluminium Batteries

Emerging rechargeable aluminium batteries (RABs) offer a sustainable option for next-generation energy storage technologies with low cost and exemplary safety. However, the development of RABs is restricted by the limited availability of high-performance cathode materials. Herein, we report two polyimide two-dimensional covalent organic frameworks (2D-COFs) cathodes with redox-bipolar capability in RAB. The optimal 2D-COF electrode achieves a high specific capacity of 132 mAh g⁻¹. Notably, the electrode presents long-term cycling stability (with a negligible ≈0.0007 % capacity decay per cycle), outperforming early reported organic RAB cathodes. 2D-COFs integrate n-type imide and p-type triazine active centres into the periodic porous polymer skeleton. With multiple characterizations, we elucidate the unique Faradaic reaction of the 2D-COF electrode, which involves AlCl²⁺ and AlCl₄⁻ dual-ions as charge carriers. This work paves the avenue toward novel organic cathodes in RABs.     

Identifying the Role of Lewis-base Sites for the Chemistry in Lithium-Oxygen Batteries

Lewis-base sites have been widely applied to regulate the properties of Lewis-acid sites in electrocatalysts for achieving a drastic technological leap of lithium-oxygen batteries (LOBs). Whereas, the direct role and underlying mechanism of Lewis-base in the chemistry for LOBs are still rarely elucidated. Herein, we comprehensively shed light on the pivotal mechanism of Lewis-base sites in promoting the electrocatalytic reaction processes of LOBs by constructing the metal–organic framework containing Lewis-base sites (named as UIO-66-NH₂). The density functional theory (DFT) calculations demonstrate the Lewis-base sites can act as electron donors that boost the activation of O₂/Li₂O₂ during the discharged-charged process, resulting in the accelerated reaction kinetics of LOBs. More importantly, the in situ Fourier transform infrared spectra and DFT calculations firstly demonstrate the Lewis-base sites can convert Li₂O₂ growth mechanism from surface-adsorption growth to solvation-mediated growth due to the capture of Li⁺ by Lewis-base sites upon discharged process, which weakens the adsorption energy of UIO-66-NH₂ towards LiO₂. As a proof of concept, LOB based on UIO-66-NH₂ can achieve a high discharge specific capacity (12 661 mAh g⁻¹), low discharged-charged overpotential (0.87 V) and long cycling life (169 cycles). This work reveals the direct role of Lewis-base sites, which can guide the design of electrocatalysts featuring Lewis-acid/base dual centers for LOBs.     

A Covalent Organic Framework as a Long-life and High-Rate Anode Suitable for Both Aqueous Acidic and Alkaline Batteries

Aqueous rechargeable batteries are prospective candidates for large-scale grid energy storage. However, traditional anode materials applied lack acid-alkali co-tolerance. Herein, we report a covalent organic framework containing pyrazine (C=N) and phenylimino (−NH−) groups (HPP-COF) as a long-cycle and high-rate anode for both acidic and alkaline batteries. The HPP-COF′s robust covalent linkage and the hydrogen bond network between −NH− and water molecules collectively improve the acid-alkaline co-tolerance. More importantly, the hydrogen bond network promotes the rapid transport of H⁺/OH⁻ by the Grotthuss mechanism. As a result, the HPP-COF delivers a superior capacity and cycle stability (66.6 mAh g⁻¹@ 30 A g⁻¹, over 40000 cycles in 1 M H₂SO₄ electrolyte; 91.7 mAh g⁻¹@ 100 A g⁻¹, over 30000 cycles @ 30 A g⁻¹ in 1 M NaOH electrolyte). The work opens a new direction for the structural design and application of COF materials in acidic and alkaline batteries.     

Supramolecular Engineering of Cathode Materials for Aqueous Zinc-ion Energy Storage Devices: Novel Benzothiadiazole Functionalized Two-Dimensional Olefin-Linked COFs

Two-dimensional covalent organic frameworks (COFs) have emerged as promising materials for energy storage applications exhibiting enhanced electrochemical performance. While most of the reported organic cathode materials for zinc-ion batteries use carbonyl groups as electrochemically-active sites, their high hydrophilicity in aqueous electrolytes represents a critical drawback. Herein, we report a novel and structurally robust olefin-linked COF-TMT-BT synthesized via the aldol condensation between 2,4,6-trimethyl-1,3,5-triazine (TMT) and 4,4′-(benzothiadiazole-4,7-diyl)dibenzaldehyde (BT), where benzothiadiazole units are explored as novel electrochemically-active groups. Our COF-TMT-BT exhibits an outstanding Zn²⁺ storage capability, delivering a state-of-the-art capacity of 283.5 mAh g⁻¹ at 0.1 A g⁻¹. Computational and experimental analyses reveal that the charge-storage mechanism in COF-TMT-BT electrodes is based on the supramolecularly engineered and reversible Zn²⁺ coordination by the benzothiadiazole units.     

ZnF2-Riched Inorganic/Organic Hybrid SEI: in situ-Chemical Construction and Performance-Improving Mechanism for Aqueous Zinc-ion Batteries

Uncontrolled dendrites growth and serious parasitic reactions in aqueous electrolytes, greatly hinder the practical application of aqueous zinc-ion battery. On the basis of in situ-chemical construction and performance-improving mechanism, multifunctional fluoroethylene carbonate (FEC) is introduced into aqueous electrolyte to construct a high-quality and ZnF₂-riched inorganic/organic hybrid SEI (ZHS) layer on Zn metal anode (ZMA) surface. Notably, FEC additive can regulate the solvated structure of Zn²⁺ to reduce H₂O molecules reactivity. Additionally, the ZHS layer with strong Zn²⁺ affinity can avoid dendrites formation and hinder the direct contact between the electrolyte and anode. Therefore, the dendrites growth, Zn corrosion, and H₂ evolution reaction on ZMA in FEC-included ZnSO₄ electrolyte are highly suppressed. Thus, ZMA in such electrolyte realize a long cycle life over 1000 h and deliver a stable coulombic efficiency of 99.1 % after 500 cycles.     

Coordination-Modulated Metal Tetrathiafulvalene Octacarboxylate Frameworks for High-Performance Lithium-Ion Battery Anodes

Modulation of the ligands and coordination environment of metal–organic frameworks (MOFs) has been an effective and relatively unexplored avenue for improving the anode performance of lithium-ion batteries (LIBs). In this study, three MOFs are synthesized, namely, M₄(o-TTFOB)(bpm)₂(H₂O)₂ (where M is Mn, Zn, and Cd; o-H₈TTFOB is ortho-tetrathiafulvalene octabenzoate; and bpm is 2,2′-bipyrimidine), based on a new ligand o-H₈TTFOB with two adjacent carboxylates on one phenyl, which allows us to establish the impact of metal coordination on the performance of these MOFs as anode materials in LIBs. Mn-o-TTFOB and Zn-o-TTFOB, with two more uncoordinated oxygen atoms from o-TTFOB⁸⁻, show higher reversible specific capacities of 1249 mAh g⁻¹ and 1288 mAh g⁻¹ under 200 mA g⁻¹ after full activation. In contrast, Cd-o-TTFOB shows a reversible capacity of 448 mAh g⁻¹ under the same condition due to the lack of uncoordinated oxygen atoms. Crystal structure analysis, cyclic voltammetry measurements of the half-cell configurations, and density functional theory calculations have been performed to explain the lithium storage mechanism, diffusion kinetics, and structure-function relationship. This study demonstrates the advantages of MOFs with high designability in the fabrication of LIBs.     

A GPT-4 Reticular Chemist for Guiding MOF Discovery**

We present a new framework integrating the AI model GPT-4 into the iterative process of reticular chemistry experimentation, leveraging a cooperative workflow of interaction between AI and a human researcher. This GPT-4 Reticular Chemist is an integrated system composed of three phases. Each of these utilizes GPT-4 in various capacities, wherein GPT-4 provides detailed instructions for chemical experimentation and the human provides feedback on the experimental outcomes, including both success and failures, for the in-context learning of AI in the next iteration. This iterative human-AI interaction enabled GPT-4 to learn from the outcomes, much like an experienced chemist, by a prompt-learning strategy. Importantly, the system is based on natural language for both development and operation, eliminating the need for coding skills, and thus, make it accessible to all chemists. Our collaboration with GPT-4 Reticular Chemist guided the discovery of an isoreticular series of MOFs, with each synthesis fine-tuned through iterative feedback and expert suggestions. This workflow presents a potential for broader applications in scientific research by harnessing the capability of large language models like GPT-4 to enhance the feasibility and efficiency of research activities.     

Isolated Tin(IV) Active Sites for Highly Efficient Electroreduction of CO2 to CH4 in Neutral Aqueous Solution

The development of efficient electrocatalysts with non-copper metal sites for electrochemical CO₂ reduction reactions (eCO₂RR) to hydrocarbons and oxygenates is highly desirable, but still a great challenge. Herein, a stable metal–organic framework (DMA)₄[Sn₂(THO)₂] (Sn-THO, THO⁶⁻ = triphenylene-2,3,6,7,10,11-hexakis(olate), DMA = dimethylammonium) with isolated and distorted octahedral SnO₆²⁻ active sites is reported as an electrocatalyst for eCO₂RR, showing an exceptional performance for eCO₂RR to the CH₄ product rather than the common products formate and CO for reported Sn-based catalysts. The partial current density of CH₄ reaches a high value of 34.5 mA cm⁻², surpassing most reported copper-based and all non-Cu metal-based catalysts. Our experimental and theoretical results revealed that the isolated SnO₆²⁻ active site favors the formation of key *OCOH species to produce CH₄ and can greatly inhibit the formation of *OCHO and *COOH species to produce *HCOOH and *CO, respectively.     

Cooperative Proton and Li-ion Conduction in a 2D-Layered MOF via Mechanical Insertion of Lithium Halides

Ionic conduction in highly designable and porous metal–organic frameworks has been explored through the introduction of various ionic species (H⁺, OH⁻, Li⁺, etc.) using post-synthetic modification such as acid, salt, or ionic liquid incorporation. Here, we report on high ionic conductivity (σ>10⁻² S cm⁻¹) in a two-dimensionally (2D)-layered Ti-dobdc (Ti₂(Hdobdc)₂(H₂dobdc), H₄dobdc: 2,5-dihydroxyterephthalic acid) via LiX (X=Cl, Br, I) intercalation using mechanical mixing. The anionic species in lithium halide strongly affect the ionic conductivity and durability of conductivity. Solid-state pulsed-field gradient nuclear magnetic resonance (PFG NMR ) verified the high mobility of H⁺ and Li⁺ ions in the temperature range of 300–400 K. In particular, the insertion of Li salts improved the H⁺ mobility above 373 K owing to strong binding with H₂O. Furthermore, the continuous increase in Li⁺ mobility with temperature contributed to the retention of the overall high ionic conductivity at high temperatures.     

Bifunctional Interphase with Target-Distributed Desolvation Sites and Directionally Depositional Ion Flux for Sustainable Zinc Anode

Aqueous zinc batteries (AZBs) feature high safety and low cost, but intricate anodic side reactions and dendrite growth severely restrict their commercialization. Herein, ethylenediaminetetraacetic acid (EDTA) grafted metal organic framework (MOF-E) is proposed as a dually-functional anodic interphase for sustainable Zn anode. Specifically, the target-distributed EDTA serves as an ion-trapped tentacle to accelerate the desolvation and ionic transport by powerful chemical coordination, while the MOFs offer suitable ionic channels to induce oriented deposition. As a result, MOF-E interphase fundamentally suppresses side reactions and guides horizontally arranged Zn deposition with (002) preferred orientations. The Zn|MOF-E@Cu cell exhibits a markedly improved Coulombic efficiency of 99.7 % over 2500 cycles, and the MOF-E@Zn|KVOH (KV₁₂O_30-y ⋅ nH₂O) cell yields a steady circulation of 5000 cycles@90.47 % at 8 A g⁻¹.     

Organic pH Buffer for Dendrite-Free and Shuttle-Free Zn-I2 Batteries

Aqueous Zn-Iodine (I₂) batteries are attractive for large-scale energy storage. However, drawbacks include, Zn dendrites, hydrogen evolution reaction (HER), corrosion and, cathode “shuttle” of polyiodines. Here we report a class of N-containing heterocyclic compounds as organic pH buffers to obviate these. We evidence that addition of pyridine /imidazole regulates electrolyte pH, and inhibits HER and anode corrosion. In addition, pyridine and imidazole preferentially absorb on Zn metal, regulating non-dendritic Zn plating /stripping, and achieving a high Coulombic efficiency of 99.6 % and long-term cycling stability of 3200 h at 2 mA cm⁻², 2 mAh cm⁻². It is also confirmed that pyridine inhibits polyiodines shuttling and boosts conversion kinetics for I⁻/I₂. As a result, the Zn-I₂ full battery exhibits long cycle stability of >25 000 cycles and high specific capacity of 105.5 mAh g⁻¹ at 10 A g⁻¹. We conclude organic pH buffer engineering is practical for dendrite-free and shuttle-free Zn-I₂ batteries.     

Structure Regulation of MOF Nanosheet Membrane for Accurate H2/CO2 Separation

High-purity H₂ production accompanied with a precise decarbonization opens an avenue to approach a carbon-neutral society. Metal–organic framework nanosheet membranes provide great opportunities for an accurate and fast H₂/CO₂ separation, CO₂ leakage through the membrane interlayer galleries decided the ultimate separation accuracy. Here we introduce low dose amino side groups into the Zn₂(benzimidazolate)₄ conformation. Physisorbed CO₂ served as interlayer linkers, gently regulated and stabilized the interlayer spacing. These evoked a synergistic effect of CO₂ adsorption-assisted molecular sieving and steric hinderance, whilst exquisitely preserving apertures for high-speed H₂ transport. The optimized amino membranes set a new record for ultrathin nanosheet membranes in H₂/CO₂ separation (mixture separation factor: 1158, H₂ permeance: 1417 gas permeation unit). This strategy provides an effective way to customize ultrathin nanosheet membranes with desirable molecular sieving ability.     

Stepwise Engineering the Pore Aperture of a Cage-like MOF for the Efficient Separation of Isomeric C4 Paraffins under Humid Conditions

The separation of isomeric C4 paraffins is an important task in the petrochemical industry, while current adsorbents undergo a trade-off relationship between selectivity and adsorption capacity. In this work, the pore aperture of a cage-like Zn-bzc (bzc=pyrazole-4-carboxylic acid) is tuned by the stepwise installation methyl groups on its narrow aperture to achieve both molecular-sieving separation and high n-C₄H₁₀ uptake. Notably, the resulting Zn-bzc-2CH₃ (bzc-2CH₃=3,5-dimethylpyrazole-4-carboxylic acid) can sensitively capture n-C₄H₁₀ and exclude iso-C₄H₁₀, affording molecular-sieving for n-C₄H₁₀/iso-C₄H₁₀ separation and high n-C₄H₁₀ adsorption capacity (54.3 cm³ g⁻¹). Breakthrough tests prove n-C₄H₁₀/iso-C₄H₁₀ can be efficiently separated and high-purity iso-C₄H₁₀ (99.99 %) can be collected. Importantly, the hydrophobic microenvironment created by the introduced methyl groups greatly improves the stability of Zn-bzc and significantly eliminates the negative effect of water vapor on gas separation under humid conditions, indicating Zn-bzc-2CH₃ is a new benchmark adsorbent for n-C₄H₁₀/iso-C₄H₁₀ separation.     

MoS2‐on‐MXene Heterostructures as Highly Reversible Anode Materials for Lithium‐Ion Batteries

Two‐dimensional (2D) heterostructured materials, combining the collective advantages of individual building blocks and synergistic properties, have spurred great interest as a new paradigm in materials science. The family of 2D transition‐metal carbides and nitrides, MXenes, has emerged as an attractive platform to construct functional materials with enhanced performance for diverse applications. Here, we synthesized 2D MoS₂‐on‐MXene heterostructures through in situ sulfidation of Mo₂TiC₂T_x MXene. The computational results show that MoS₂‐on‐MXene heterostructures have metallic properties. Moreover, the presence of MXene leads to enhanced Li and Li₂S adsorption during the intercalation and conversion reactions. These characteristics render the as‐prepared MoS₂‐on‐MXene heterostructures stable Li‐ion storage performance. This work paves the way to use MXene to construct 2D heterostructures for energy storage applications.     

Molecular Engineering of a Metal-Organic Polymer for Enhanced Electrochemical Nitrate-to-Ammonia Conversion and Zinc Nitrate Batteries

Metal–organic framework-based materials are promising single-site catalysts for electrocatalytic nitrate (NO₃⁻) reduction to value-added ammonia (NH₃) on account of well-defined structures and functional tunability but still lack a molecular-level understanding for designing the high-efficient catalysts. Here, we proposed a molecular engineering strategy to enhance electrochemical NO₃⁻-to-NH₃ conversion by introducing the carbonyl groups into 1,2,4,5-tetraaminobenzene (BTA) based metal-organic polymer to precisely modulate the electronic state of metal centers. Due to the electron-withdrawing properties of the carbonyl group, metal centers can be converted to an electron-deficient state, fascinating the NO₃⁻ adsorption and promoting continuous hydrogenation reactions to produce NH₃. Compared to CuBTA with a low NO₃⁻-to-NH₃ conversion efficiency of 85.1 %, quinone group functionalization endows the resulting copper tetraminobenzoquinone (CuTABQ) distinguished performance with a much higher NH₃ FE of 97.7 %. This molecular engineering strategy is also universal, as verified by the improved NO₃⁻-to-NH₃ conversion performance on different metal centers, including Co and Ni. Furthermore, the assembled rechargeable Zn−NO₃⁻ battery based on CuTABQ cathode can deliver a high power density of 12.3 mW cm⁻². This work provides advanced insights into the rational design of metal complex catalysts through the molecular-level regulation for NO₃⁻ electroreduction to value-added NH₃.     

Postsynthetic Photochemical Modification and 2D Structuring of Zr-MOF Thin Films Containing Benzophenone Linker Molecules

For the fabrication of next-generation MOF-based devices the availability of highly adaptable materials in suitable shapes is crucial. Here, we present thin films of a metal–organic framework (MOF) containing photoreactive benzophenone units. Crystalline, oriented and porous films of the zirconium-based bzpdc-MOF (bzpdc=benzophenone-4-4′-dicarboxylate) are prepared by direct growth on silicon or glass substrates. Via a subsequent photochemical modification of the Zr-bzpdc-MOF films, various properties can be tuned postsynthetically by covalent attachment of modifying agents. Apart from the modification with small molecules, also grafting-from polymerization reactions are possible. In a further extension, 2D structuring and photo-writing of defined structures is also possible, for example by using a photolithographic approach, paving the way towards micro-patterned MOF surfaces.     

Controlled Partial Linker Thermolysis in Metal-Organic Framework UiO-66-NH2 to Give a Single-Site Copper Photocatalyst for the Functionalization of Terminal Alkynes

Metal–organic frameworks (MOFs) with expanding porosity and tailored pore environments are intriguing for catalytic applications. We report herein a straightforward method of controlled partial linker thermolysis to introduce desirable mesopores into mono-ligand MOFs, which is different from the classical thermolyzing method that starts from mixed-linker MOFs. UiO-66-NH₂, after partial ligand thermolysis, exhibits significant mesoporosity, retained crystal structure, improved charge photogeneration and abundant anchoring sites, which is ideal to explore single-site photocatalysis. Atomically dispersed Cu is then accommodated in the tailored pore. The resulting single-site Cu catalyst exhibits excellent performance for photocatalytic alkylation and oxidation coupling for the functionalization of terminal alkynes. The study highlights the advantage of controlled partial linker thermolysis to synthesize hierarchical MOFs to achieve the advanced single-site photocatalysis.