Porous Metal-Organic Frameworks Containing Reversible Disulfide Linkages as Cathode Materials for Lithium-Ion Batteries

Molecular Evolution of Target Organosulfur Enables High-Performance Aqueous Zinc Batteries

Organic cathode materials for aqueous zinc-ion batteries (AZIBs) have garnered significant attention due to their environmental friendliness and structurally customizable nature. However, the low voltage, sluggish redox kinetics, and high solubility of most n-type cathode materials hinder their wide deployment. To overcome these challenges, through molecular evolution, we rationally select a cheap industrial material, organodisulfide 2,2'-dithiobis (benzothiazole) (MBTS), as an n-type cathode material for AZIBs. Due to the presence of N-containing benzothiazole rings, the dissociation energy of the sulfur-sulfur (S-S) bond is reduced, substantially enhancing the discharge voltage and improving the reaction kinetics. They regulate the π-conjugated plane to achieve a low solubility and fast charge transfer. Moreover, density functional theory (DFT) calculations elucidate the synergistic effect between adjacent active sites and Zn2+ storage reactions, revealing that the formation of weak coordination bonds between N and Zn atoms (N-Zn-S bond) reduces the solubility of the discharge product. Molecular evolution has led to the fast reaction kinetics of zinc ion storage, thus achieving a high performance under high mass loading. At a current density of 0.05 A g-1, MBTS exhibits an average discharge voltage of 1.02 V, with a mere overpotential of 100 mV, and delivers a high specific capacity of 153.6 mAh g-1. The assembled pouch cell demonstrates an excellent rate capability of 124.4 mAh g-1 at 1 A g-1 and displays a stable cycle life after 200 cycles with 96.8% capacity retention. Remarkably, MBTS maintains high specific capacity and favorable cycle stability under various ultrahigh loadings, up to 18.2 mg cm-2. The findings provide substantial guidance for practical applications of organic electrode materials in AZIBs.

Single Crystal to Single Crystal Transformation of Porous Materials Based on Zinc Nodes and Mercaptobenzoic Acid

Porous coordination polymers (PCPs) are an excellent class of porous crystalline materials with tunable properties and intriguing potential applications spanning multiple disciplines. In this work, we report the synthesis and characterization of a PCP (HI-103) based on 4,4'-dithiodibenzoic acid ligand and zinc nitrate with two DMF molecules residing in the porous network. The stability of the porous network was analyzed by heating the compound at 60.0 °C for two days, and the structural analysis revealed a new PCP (HI-104) was formed with one of the DMF molecules, indicating a single-crystal to single-crystal (SCSC) transformation. The solvent molecules were completely removed by extensive drying (HI-103-dry), and the integrity of the porous network was verified by powder X-ray diffraction (PXRD) and thermogravimetric analysis. The reversibility of SCSC transformation was confirmed by treating HI-103-dry with DMF molecules, resulting in HI-103 after five days. The adsorption studies of HI-103-dry with other solvents revealed that SCSC transformation was not observed for DMA and DEA, but some structural changes were observed in the presence of DMSO. The adsorption studies performed in the presence of an equimolar mixture of DMF, DMA, and DMA indicated that HI-103-dry could selectively adsorb DMF molecules from the analogous mixture.

Disulfide Bonds as Functional Tethers in Metal-Organic Frameworks

The functionality of metal-organic frameworks (MOFs) is often encoded by specific chemical moieties found within these architectures. As such, new techniques to install increasingly more complex functionalities in MOFs are regularly being reported in the literature. One such functional group is the disulfide bond. The redox behavior of this covalent linkage renders MOFs responsive to stimuli, often under reducing conditions. Here, we review examples in which disulfide-containing MOFs are deployed in applications including drug delivery, therapeutic ferroptosis, exfoliation, energy storage, sensing, and others.

Metal-organic frameworks for high-performance cathodes in batteries

Metal-organic frameworks (MOFs) are functional materials that are proving to be indispensable for the development of next-generation batteries. The porosity, crystallinity, and abundance of active sites in MOFs, which can be tuned by selecting the appropriate transition metal/organic linker combination, enable MOFs to meet the performance requirements for cathode materials in batteries. Recent studies on the use of MOFs in cathodes have verified their high durability, cyclability, and capacity thus demonstrating the huge potential of MOFs as high-performance cathode materials. However, to keep pace with the rapid growth of the battery industry, several challenges hindering the development of MOF-based cathode materials need to be overcome. This review analyzes current applications of MOFs to commercially available lithium-ion batteries as well as advanced batteries still in the research stage. This review provides a comprehensive outlook on the progress and potential of MOF cathodes in meeting the performance requirements of the future battery industry.

Recent Advances in Pristine Iron Triad Metal-Organic Framework Cathodes for Alkali Metal-Ion Batteries

Pristine iron triad metal-organic frameworks (MOFs), i.e., Fe-MOFs, Co-MOFs, Ni-MOFs, and heterometallic iron triad MOFs, are utilized as versatile and promising cathodes for alkali metal-ion batteries, owing to their distinctive structure characteristics, including modifiable and designable composition, multi-electron redox-active sites, exceptional porosity, and stable construction facilitating rapid ion diffusion. Notably, pristine iron triad MOFs cathodes have recently achieved significant milestones in electrochemical energy storage due to their exceptional electrochemical properties. Here, the recent advances in pristine iron triad MOFs cathodes for alkali metal-ion batteries are summarized. The redox reaction mechanisms and essential strategies to boost the electrochemical behaviors in associated electrochemical energy storage devices are also explored. Furthermore, insights into the future prospects related to pristine iron triad MOFs cathodes for lithium-ion, sodium-ion, and potassium-ion batteries are also delivered.

Disulfide-Driven Pore Functionalization of Metal-Organic Frameworks

Post-synthetic modification (PSM) imparts additional functionality to metal-organic frameworks (MOFs) that is often difficult to access using solvothermal synthesis. As such, expanding the repertory of PSM reactions available to the practitioner is of increased importance for the generation of materials tailored for desired applications. Herein, a method is described for the protecting group-free installation of diverse functional groups within the pores of a MIL-53(Al) analogue via disulfide bond formation. The majority of the reactions proceed with thiol-to-disulfide conversions ranging from high to nearly quantitative. The disulfide bonds are stable in various solvents and can be cleaved in the presence of a reducing agent.

A one-dimensional cobalt-based coordination polymer as a cathode material of lithium-ion batteries

For obtaining high-performance lithium-ion batteries, it is important to develop new cathode materials with high capacity. Herein, a one-dimensional coordination polymer [Co(4-DTBPT) (DMF)₂(H₂O)₂] (4-DTBPT) (C₁₀H₄O₈) (Co-DTBPT) (4-DTBPT = 2,7-di(4H-1,2,4-triazol-4yl)benzo[lmn][3,8] phenanthroline-1,3,6,8-(2H,7H)-tetraone; DMF = dimethylformamide) was synthesized and its electrochemical performance as the cathode material of lithium-ion batteries was first investigated. The Co-DTBPT electrode showed better cycling stability and a specific capacity of 55 mA h g^-1 at 50 mA g^-1 after 50 cycles, and the coulombic efficiency was close to 100%. The capacity contribution of the Co-DTBPT electrode may be ascribed to the redox reaction of the Co(II) ion and the 4-DTBPT ligand in the process of charge and discharge. Our work proves once again that using one-dimensional coordination polymers as cathode materials for lithium-ion batteries is a feasible way.

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.

Metal-Organic Frameworks and Their Derivatives: Designing Principles and Advances toward Advanced Cathode Materials for Alkali Metal Ion Batteries

Metal-organic frameworks (MOFs) and their derivatives have attracted enormous attention in the field of energy storage, due to their high specific surface area, tunable structure, highly ordered pores, and uniform metal sites. Compared with the wide research of MOFs and their related materials on anode materials for alkali metal ion batteries, few works are on cathode materials. In this review, design principles for promoting the electrochemical performance of MOF-related materials in terms of component/structure design, composite fabrication, and morphology engineering are presented. By summarizing the advancement of MOFs and their derivatives, Prussian blue and its analogs, and MOF surface coating, challenges and opportunities for future outlooks of MOF-related cathode materials are discussed.

A novel crystalline nanoporous iron phosphonate based metal–organic framework as an efficient anode material for lithium ion batteries

A new Fe-MOF prepared by using a tetraphosphonic acid as a ligand is reported and it showed high specific capacity and excellent recycling efficiency in lithium-ion batteries.