Porous rod-shaped Co3O4 derived from Co-MOF-74 as high-performance anode materials for lithium ion batteries

Recent Progress of Low-Dimensional Metal-Organic Frameworks for Aqueous Zinc-Based Batteries

Aqueous zinc-based batteries (AZBs) are promising energy storage solutions with remarkable safety, abundant Zn reserve, cost-effectiveness, and relatively high energy density. However, AZBs still face challenges such as anode dendrite formation that reduces cycling stability and limited cathode capacity. Recently, low-dimensional metal-organic frameworks (LD MOFs) and their derivatives have emerged as promising candidates for improving the electrochemical performance of AZBs owing to their unique morphologies, high structure tunability, high surface areas, and high porosity. However, clear guidelines for developing LD MOF-based materials for high-performance AZBs are scarce. In this review, the recent progress of LD MOF-based materials for AZBs is critically examined. The typical synthesis methods and structural design strategies for improving the electrochemical performance of LD MOF-based materials for AZBs are first introduced. The recent noteworthy research achievements are systematically discussed and categorized based on their applications in different AZB components, including cathodes, anodes, separators, and electrolytes. Finally, the limitations are addressed and the future perspectives are outlined for LD MOFs and their derivatives in AZB applications. This review provides clear guidance for designing high-performance LD MOF-based materials for advanced AZBs.

One-Dimensional Croconate-Based Fe-CP as a High-Performance Anode Material for Lithium-Ion Batteries

Coordination polymers (CPs) have attracted greater scientific attention as promising electrode materials for lithium-ion batteries (LIBs) due to their diverse and versatile structural chemistry. This study introduces a croconate-based one-dimensional CP, namely [Fe(C5O5)(H2O)3]n) (referred to as Fe-CP), as an efficient anode material with high-performance characteristics for rechargeable LIBs. The ligand with abundant redox sites coordinating to the transition metal ion endowed the anode material with a remarkable stability in the electrolyte, in addition to high capacity, high-rate capability, and high cycling performance during charging/discharging process. The Fe-CP has a unique chain-based supramolecular structure, setting it apart from other porous three-dimensional molecular materials. The presence of unrestricted channels between the chains facilitates the diffusion of lithium ions in this unique structure. When tested at 100 mA g-1 over a range of voltages between 0.01 and 2.4 V, the Fe-CP anode demonstrated a noteworthy specific capacity of 521 mA h g-1 over 140 cycles. Moreover, the Fe-CP anode material exhibited excellent rate performance and demonstrated favorable cyclability. Following exposure to high charging and discharging rates of 2 A g-1, the anode ultimately regained its initial capability when the current rate was back at 100 mA g-1.

High-Performance Visible-Light Photocatalysts for H2 Production: Rod-Shaped Co3O4/CoO/Co2P Heterojunction Derived from Co-MOF-74

Photocatalyst systems generally consist of catalysts and cocatalysts to realize light capture, charge carrier migration, and surface redox reactions. Developing a single photocatalyst that performs all functions while minimizing efficiency loss is extremely challenging. Herein, rod-shaped photocatalysts Co₃O₄/CoO/Co₂P are designed and prepared using Co-MOF-74 as a template, which displays an outstanding H₂ generation rate of 6.00 mmol·g^-1·h^-1 when exposed to visible light irradiation. It is 12.8 times higher than pure Co₃O₄. Under light excitation, the photoinduced electrons migrate from the catalysts of Co₃O₄ and CoO to the cocatalyst Co₂P. The trapped electrons can subsequently undergo a reduction reaction to produce H₂ on the surface. Density functional theory calculations and spectroscopic measurements reveal that enhanced performance results from the extended lifetime of photogenerated carriers and higher charge transfer efficiency. The ingenious structure and interface design presented in this study may guide the general synthesis of metal oxide/metal phosphide homometallic composites for photocatalysis.

Enhanced Fenton-like catalysis for pollutants removal via MOF-derived CoxFe3-xO4 membrane: Oxygen vacancy-mediated mechanism

Traditional batch configuration is not sustainable due to catalyst leaching and ineffective recovery. Herein, a novel membrane-based catalyst with oxygen vacancies is developed, which assembled metal-organic-framework cobalt ferrite nanocrystals (MOF-d Co_xFe_3-xO₄) on polyvinylidene fluoride membrane to activate peroxymonosulfate (PMS) for catalytic degradation of emerging pollutants. MOF-d Co_xFe_3-xO₄ are synthesized by one-step pyrolysis using Co/Fe bimetallic organic frameworks (Co_xFe_3-x bi-MOF) with tunable cobalt content as a template (x/3-x represented the molar ratio of Co and Fe in MOF). Intriguingly, MOF-d Co_1.75Fe_1.25O₄ membrane exhibits excellent PMS activation efficiency as indicated by 95.12% removal of the probe chemical (bisphenol A) at 0.5 mM PMS (∼100 L m^-2 h^-1 at the loading of 10 mg), which is significantly higher than the traditional Co_1.75Fe_1.25O₄ suspension system (34.16%). Experimental results show that the membrane has excellent anti-interference ability to anions and dissolved organic matter, and can effectively degrade a variety of emerging pollutants, and its performance is not inhibited by the change of solution pH (3-9) or the long-term (20 h) continuous flow operation. EPR and quenching experiments show that catalytic degradation is the result of the synergistic effect of radicals and non-radicals. The oxygen vacancy-mediated mechanism can explain the formation of active substances, and the formation of ¹O₂ plays an important role in the degradation of bisphenol A. This study provides a membrane-based strategy for effective and sustainable removal of emerging pollutants.

Co3ZnC@NC Material Derived from ZIF-8 for Lithium-Ion Capacitors

Metal-organic framework (MOF)-derived carbon materials were widely reported as the anodes of lithium-ion capacitors (LICs). However, tunning the structure and electrochemical performance of the MOF-derived carbon materials is still challenging. Herein, metal carbide materials of Co3ZnC@NC-8:2 were obtained by the pyrolysis of the MOF materials of Co0.2Zn0.8ZIF-8 (Zn/Co ratio of 8:2). A half-cell assembled with the Co3ZnC@NC-8:2 electrode exhibits a discharge capacity of the electrode material of 598 mAh g-1 at a current density of 0.1 A g-1. After 100 cycles, the retention rate of discharge specific capacity is about 90%. The high performance of Co3ZnC@NC-8:2 is ascribed to its high crystalline degree and well-defined structure, which facilitates the intercalation/deintercalation of lithium ions and buffers the volume change during the charge/discharge process. The high capacitance contribution ratio calculated by cyclic voltammetry (CV) curves at different scanning rates indicates the pseudocapacitance storage mechanism. LICs constructed from the Co3ZnC@NC-8:2 material have a rectangular CV curve, while the charge-discharge curve has a symmetrical triangular shape. This study indicates that MOF-derived carbon is one of the promising materials for high-performance LICs.

Metal-organic framework based electrode materials for lithium-ion batteries: a review

Metal-organic frameworks (MOFs) with efficient surface and structural properties have risen as a distinctive class of porous materials through the last few decades, which has enabled MOFs to gain attention in a wide range of applications like drug delivery, gas separation and storage, catalysis and sensors. Likewise, they have also emerged as efficient active materials in energy storage devices owing to their remarkable conducting properties. Metal-organic frameworks (MOFs) have garnered great interest in high-energy-density rechargeable batteries and super-capacitors. Herein the study presents their expanding diversity, structures and chemical compositions which can be tuned at the molecular level. It also aims to evaluate their inherently porous framework and how it facilitates electronic and ionic transportation through the charging and discharging cycles of lithium-ion batteries. In this review we have summarized the various synthesis paths to achieve a particular metal-organic framework. This study focuses mainly on the implementation of metal-organic frameworks as efficient anode and cathode materials for lithium-ion batteries (LIBs) with an evaluation of their influence on cyclic stability and discharge capacity. For this purpose, a brief assessment is made of recent developments in metal-organic frameworks as anode or cathode materials for lithium-ion batteries which would provide enlightenment in optimizing the reaction conditions for designing a MOF structure for the battery community and electrochemical energy storage applications.

Magnetic CoFe2O4 nanocrystals derived from MIL-101 (Fe/Co) for peroxymonosulfate activation toward degradation of chloramphenicol

In this study, porous magnetic CoFe₂O₄ nanocrystals (NCs) were successfully synthesized by using bimetal-organic framework (MOF) as a precursor, and used as catalysts to activate peroxymonosulfate (PMS) for the removal of chloramphenicol (CAP) in the solution. The structure and physicochemical properties of CoFe₂O₄ NCs were thoroughly examined by a series of characterization techniques. The results revealed as-synthesized CoFe₂O₄ had a nanorod-shaped structure with high specific surface area (83.00 m² g^-1) and pore volume (0.31 cm³ g^-1). Furthermore, the degradation efficiency (100%) and the removal of total organic carbon (68.09%) were achieved after 120 min with 0.1 g/L CoFe₂O₄ NCs, 2 mM PMS and 10 mg/L CAP at pH of 8.20. In addition, effects of catalyst dosage, PMS dosage, initial pH values, CAP concentration and co-existing anions as well as natural organic matters in the solution on the degradation efficiencies were studied and all the removal can be well fitted with pseudo-first-order kinetic model (R² > 0.96). Sulfate radicals (SO₄^•-) and hydroxyl radicals (HO•) were proved to be two main reactive species for CAP removal in CoFe₂O₄/PMS system based on quenching experiments. CAP was degraded by the main pathways of dichlorination, denitration, decarboxylation, hydroxylation, ring cleavage and chain cleavage on CoFe₂O₄/PMS system through high performance liquid chromatograph-mass spectrometry analysis. We believe that this study would be very meaningful to promote the applications of MOFs-derived catalysts on the SO₄^•- based advanced oxidation processes (SR-AOPs) for the environmental remediation.

Buffered Coordination Modulation as a Means of Controlling Crystal Morphology and Molecular Diffusion in an Anisotropic Metal-Organic Framework

Significant advances have been made in the synthesis of chemically selective environments within metal-organic frameworks, yet materials development and industrial implementation have been hindered by the inability to predictively control crystallite size and shape. One common strategy to control crystal growth is the inclusion of coordination modulators, which are molecular species designed to compete with the linker for metal coordination during synthesis. However, these modulators can simultaneously alter the pH of the reaction solution, an effect that can also significantly influence crystal morphology. Herein, noncoordinating buffers are used to independently control reaction pH during metal-organic framework synthesis, enabling direct interrogation of the role of the coordinating species on crystal growth. We demonstrate the efficacy of this strategy in the synthesis of low-dispersity single-crystals of the framework Co₂(dobdc) (dobdc^4-= 2,5-dioxido-1,4-benzenedicarboxylate) in a pH 7-buffered solution using cobalt(II) acetate as the metal source. Density functional theory calculations reveal that acetate competitively binds to Co during crystallization, and by using a series of cobalt(II) salts with carboxylate anions of varying coordination strength, it is possible to control crystal growth along the c-direction. Finally, we use zero length column chromatography to show that crystal morphology has a direct impact on guest diffusional path length for the industrially important hydrocarbon m-xylene. Together, these results provide molecular-level insight into the use of modulators in governing crystallite morphology and a powerful strategy for the control of molecular diffusion rates within metal-organic frameworks.

A Trinuclear Cobalt-Organic Framework: Solvatochromic Sensor towards CH2 Cl2 , and its Derivative as an Anode of Lithium-Ion Batteries with High Performance

Here, a porous cobalt-organic framework with pillared layer structures, namely [Co₃ OBA₃ PTD(H₂ O)₂ ⋅ 2 DMA⋅H₂ O]_n (1, H₂ OBA=4,4'-oxybis(benzoic acid); PTD=6-(pyridin-4-yl)-1,3,5-triazine-2,4-diamine), was fabricated by using cobalt trinuclear nodes, low-cost carboxylic linker, and accessible nitrogen heterocyclic ligands. This compound exhibited a highly efficient solvatochromism towards CH₂ Cl₂ within one minute and can be used 200 times at least. The corresponding dropper detector was assembled as a practical sensor. Meanwhile, the porous Co₃ O₄ was obtained by a simple but effective annealing treatment. Electrochemical measurements confirm that this Co₃ O₄ material derived from compound 1 shows high and stable lithium storage capabilities (1081.75 mA h g^-1 at 200 mA g^-1 after 115 cycles) and excellent rate properties.

Co/Ni-MOF-74-derived CoNi2S4 nanoparticles embedded in porous carbon as a high performance anode material for sodium ion batteries

In this study, Co/Ni-MOF-74-derived CoNi₂S₄ nanoparticles embedded in porous carbon (CoNi₂S₄@C) were successfully prepared using Co/Ni-MOF-74 as precursor. And, CoNi₂S₄@C exhibits excellent electrochemical performance as an anode material for sodium ion batteries.

Structural Engineering of Low-Dimensional Metal-Organic Frameworks: Synthesis, Properties, and Applications

Low-dimensional metal-organic frameworks (LD MOFs) have attracted increasing attention in recent years, which successfully combine the unique properties of MOFs, e.g., large surface area, tailorable structure, and uniform cavity, with the distinctive physical and chemical properties of LD nanomaterials, e.g., high aspect ratio, abundant accessible active sites, and flexibility. Significant progress has been made in the morphological and structural regulation of LD MOFs in recent years. It is still of great significance to further explore the synthetic principles and dimensional-dependent properties of LD MOFs. In this review, recent progress in the synthesis of LD MOF-based materials and their applications are summarized, with an emphasis on the distinctive advantages of LD MOFs over their bulk counterparties. First, the unique physical and chemical properties of LD MOF-based materials are briefly introduced. Synthetic strategies of various LD MOFs, including 1D MOFs, 2D MOFs, and LD MOF-based composites, as well as their derivatives, are then summarized. Furthermore, the potential applications of LD MOF-based materials in catalysis, energy storage, gas adsorption and separation, and sensing are introduced. Finally, challenges and opportunities of this fascinating research field are proposed.

Porous Mn-doped cobalt oxide@C nanocomposite: a stable anode material for Li-ion rechargeable batteries

Cobalt oxide is a transition metal oxide, well studied as an electrode material for energy storage applications, especially in supercapacitors and rechargeable batteries, due to its high charge storage ability. However, it suffers from low conductivity, which effectively hampers its long-term stability. In the present work, a simple strategy to enhance the conductivity of cobalt oxide is adopted to achieve stable electrochemical performance by means of carbon coating and Mn doping, via a simple and controlled, urea-assisted glycine-nitrate combustion process. Structural analysis of carbon coated Mn-doped Co₃O₄ (Mn-Co₃O₄@C) confirms the formation of nanoparticles (∼50 nm) with connected morphology, exhibiting spinel structure. The Mn-Co₃O₄@C electrode displays superior electrochemical performance as a Li-ion battery anode, delivering a specific capacity of 1250 mAh g^-1. Mn-Co₃O₄@C demonstrates excellent performance in terms of long-term stability, keeping charge storage ability intact even at high current rates due to the synergistic effects of fast kinetics-provided by enriched electronic conductivity, which allows ions to move freely to active sites and electrons from reaction sites to substrate during redox reactions-and high surface area combined with mesoporous architecture. The fully assembled battery device using Mn-Co₃O₄@C and standard LiCoO₂ electrode shows 90% capacity retention over 100 cycles.