Metal-Organic Framework Derived Porous Hollow Co3O4/N-C Polyhedron Composite with Excellent Energy Storage Capability

Ultra-sensitive detection of 4-chloro-2-methylphenoxyacetic acid herbicide using a porous Co-1,4-benzenedicarboxylate /montmorillonite nanocomposite sensor

The detection of 4-chloro-2-methylphenoxyacetic acid (CMPA) herbicide is crucial due to the potential health risks linked to exposure through drinking water, air, and food, which may adversely affect liver and kidney functions. To address this environmental concern and promote sustainable agriculture, a sensitive carbon paste sensor incorporating a composite material was developed. The composite sensor is based on porous cobalt-1,4-benzenedicarboxylate metal-organic framework and exfoliated montmorillonite nanolayers (Co-OF/MMt). This sensor enables the voltammetric detection of CMPA in real soil samples using linear sweep adsorptive anodic stripping voltammetry (LS-AdASV), facilitating early and accurate monitoring of herbicide levels. The Co-OF/MMt nanocomposite was synthesized via a hydrothermal method involving the precipitation of Co-OF in the presence of MMt. Comprehensive characterization of the synthesized materials was carried out using Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), SEM-Energy dispersive X-ray spectroscopy (SEM-EDX) and surface area analysis (BET). The resulting modified carbon paste sensor, utilizing 1.0% Co-OF/MMt nanocomposite, exhibited superior electrochemical properties compared with the bare carbon paste sensor, possessing an electroactive surface area of 1004.1 m2/g with a minimal resistivity (Rct) of 330 Ω. Under standard operating conditions, the developed sensor demonstrated detection limits of 0.03 nM and 0.1 nM across two broad linear ranges (0.03 to 0.10 nM - 0.10 to 1.0 nM) and (0.1 to 1.0 nM - 1.0 to 7.0 nM), respectively, for CMPA determination in both bulk and soil samples. These results pointed out the promising electrochemical modified sensor for the direct and simple detection of certain herbicides in environmental matrices, without the need for sample pretreatment steps. This capability supports sustainable development goals by enhancing effective environmental monitoring.

Defective porous urchin-like ZnO/NiO microspheres-coated solid-phase microextraction fiber for analysis of trace polychlorinated biphenyls in milk

Owing to the high lipophilicity of polychlorinated biphenyls (PCB), they easily accumulate in dairy products. Although usually present at very low levels, they pose a serious threat to human health. Therefore, developing a sensitive and reliable method for detecting PCB in dairy products is crucial. Herein, Herein, a metal-organic framework (MOF) material named with bimetallic nodes and double ligands was prepared as a precursor using a one-pot hydrothermal method. Defective porous urchin-like ZnO/NiO, derived from these MOF-based precursors (ZnNi-MOF-NH2) as a sacrificial template, was synthesized via pyrolysis to remove heat-sensitive ligands. To the best of our knowledge, this urchin-like nanostructured ZnO/NiO hybrid was utilized as a solid-phase microextraction (SPME) coating for the first time. Headspace SPME (HS-SPME) was developed for non-contact extraction of PCB in milk prior to gas chromatography-tandem mass spectrometry (GC-MS/MS) analysis. Under optimal conditions, the HS-SPME-GC-MS/MS method exhibited a wide linear range (0.01-1000 ng·L-1), low limits of detection (0.003-0.025 ng·L-1), and high enrichment factors (5714-9906). Additionally, the performance of the ZnO/NiO SPME fiber coating showed no noticeable decrease after 175 uses. The method was applied to trace PCB analysis in milk samples, yielding recoveries of 70.3-114.1 %. The ZnO/NiO derived from MOF-based material provides a promising candidate for SPME coatings to extract PCB and other analogs.

MOF-Derived Bimetallic Selenide CoNiSe2 Nanododecahedrons Encapsulated in Porous Carbon Matrix as Advanced Anodes for Lithium-Ion Batteries

Transition metal selenides have received considerable attention as promising candidates for lithium-ion battery (LIB) anode materials due to their high theoretical capacity and safety characteristics. However, their commercial viability is hampered by insufficient conductivity and volumetric fluctuations during cycling. To address these issues, we have utilized bimetallic metal-organic frameworks to fabricate CoNiSe2/C nanodecahedral composites with a high specific surface area, abundant pore structures, and a surface-coated layer of the carbon-based matrix. The optimized material, CoNiSe2/C-700, exhibited impressive Li+ storage performance with an initial discharge specific capacity of 2125.5 mA h g-1 at 0.1 A g-1 and a Coulombic efficiency of 98% over cycles. Even after 1000 cycles at 1.0 A g-1, a reversible discharge specific capacity of 549.9 mA h g-1 was achieved. The research highlights the synergistic effect of bimetallic selenides, well-defined nanodecahedral structures, stable carbon networks, and the formation of smaller particles during initial cycling, all of which contribute to improved electronic performance, reduced volume change, increased Li+ storage active sites, and shorter Li+ diffusion paths. In addition, the pseudocapacitance behavior contributes significantly to the high energy storage of Li+. These features facilitate rapid charge transfer and help maintain a stable solid-electrolyte interphase layer, which ultimately leads to an excellent electrochemical performance. This work provides a viable approach for fabricating bimetallic selenides as anode materials for high-performance LIBs through architectural engineering and compositional tailoring.

Designing N-doped graphene-like supported highly dispersed bimetallic NiCoP NPs as an efficient electrocatalyst for water oxidation

Electrocatalysts with a high oxygen evolution reaction (OER) activity are very important for electrochemical water oxidation, but they are also challenging. In this study, N-doped graphene-like supported highly dispersed bimetallic NiCoP NPs as an efficient electrocatalyst for water oxidation were prepared by using cation exchange resin as a carbon source and by loading cobalt and nickel on D001 by a high-temperature calcination method. The designed electrocatalyst with bimetallic phosphide as the active center shows excellent OER catalytic performance, with an overpotential of 324 mV at 10 mA cm-2 and a corresponding Tafel slope of 97.28 mV dec-1. The increase in NiCoP-3@GL activity may be due to the increase in surface area (933.49 m2 g-1) caused by the irregular morphology, rich interface contact, and porous structure. In addition, the strong combination of NiCoP and GL improves the structural stability and durability of the electrocatalyst. After 5000 cyclic voltammetry tests, the performance of the catalyst decreased by 16.9 %. This work provides a new idea for designing efficient bimetallic phosphide electrocatalysts.

Principles of Design and Synthesis of Metal Derivatives from MOFs

Materials derived from metal-organic frameworks (MOFs) have demonstrated exceptional structural variety and complexity and can be synthesized using low-cost scalable methods. Although the inherent instability and low electrical conductivity of MOFs are largely responsible for their low uptake for catalysis and energy storage, a superior alternative is MOF-derived metal-based derivatives (MDs) as these can retain the complex nanostructures of MOFs while exhibiting stability and electrical conductivities of several orders of magnitude higher. The present work comprehensively reviews MDs in terms of synthesis and their nanostructural design, including oxides, sulfides, phosphides, nitrides, carbides, transition metals, and other minor species. The focal point of the approach is the identification and rationalization of the design parameters that lead to the generation of optimal compositions, structures, nanostructures, and resultant performance parameters. The aim of this approach is to provide an inclusive platform for the strategies to design and process these materials for specific applications. This work is complemented by detailed figures that both summarize the design and processing approaches that have been reported and indicate potential trajectories for development. The work is also supported by comprehensive and up-to-date tabular coverage of the reported studies.

In Situ Construction of Heterostructured Co3O4/CoP Nanoflake Arrays on Carbon Cloth as Binder-Free Anode for High-Performance Lithium-Ion Batteries

Cobalt oxide (Co₃O₄) is regarded as the anode material for lithium-ion batteries (LIBs) with great research value owing to its environmental friendliness and exceptional theoretical capacity. However, the low intrinsic conductivity, poor electrochemical kinetics, and unsatisfactory cycling performance severely limit its practical applications in LIBs. The construction of a self-standing electrode with heterostructure by introducing a highly conductive cobalt-based compound is an effective strategy to solve the above issues. Herein, Co₃O₄/CoP nanoflake arrays (NFAs) with heterostructure are constructed skillfully directly grown on carbon cloth (CC) by in situ phosphorization as an anode for LIBs. Density functional theory simulation results demonstrate that the construction of heterostructure greatly increases the electronic conductivity and Li ion adsorption energy. The Co₃O₄/CoP NFAs/CC exhibited an extraordinary capacity (1490.7 mA h g^-l at 0.1 A g^-l) and excellent performance at high current density (769.1 mA h g^-l at 2.0 A g^-l), as well as remarkable cyclic stability (451.3 mA h g^-l after 300 cycles with a 58.7% capacity retention rate). The reasonable construction of heterostructure can promote the interfacial ion transport, significantly enhance the adsorption energy of lithium ions, improve the conductivity of Co₃O₄ electrode material, promote the partial charge transfer throughout the charge and discharge cycles, and enhance the overall electrochemical performance of the material.

Design and Preparation of Avermectin Nanopesticide for Control and Prevention of Pine Wilt Disease

Pine wilt disease is a devastating forest disaster caused by Bursaphelenchus xylophilus, which has brought inestimable economic losses to the world's forestry due to lack of effective prevention and control measures. In this paper, a porous structure CuBTC was designed to deliver avermectin (AM) and a control vector insect Japanese pine sawyer (JPS) of B. xylophilus, which can improve the biocompatibility, anti-photolysis and delivery efficacy of AM. The results illustrated the cumulative release of pH-dependent AM@CuBTC was up to 12 days (91.9%), and also effectively avoided photodegradation (pH 9.0, 120 h, retention 69.4%). From the traceable monitoring experiment, the AM@CuBTC easily penetrated the body wall of the JPS larvae and was transmitted to tissue cells though contact and diffusion. Furthermore, AM@CuBTC can effectively enhance the cytotoxicity and utilization of AM, which provides valuable research value for the application of typical plant-derived nerve agents in the prevention and control of forestry pests. AM@CuBTC as an environmentally friendly nanopesticide can efficiently deliver AM to the larval intestines where it is absorbed by the larvae. AM@CuBTC can be transmitted to the epidemic wood and dead wood at a low concentration (10 mg/L).

A Flexible and Transparent Zinc-Nanofiber Network Electrode for Wearable Electrochromic, Rechargeable Zn-Ion Battery

The flexible electrochromic Zn-ion battery (FE-ZiB), a newly born energy-storage technology having both electrochromic characteristics and energy-storage capability in a single device, will be a promising technology for the future transparent wearable electronics. However, the current technology limits the fabrication of FE-ZIB because the zinc (Zn) anode material is opaque and rigid. The development of a flexible and transparent Zn anode is the key factor to overcoming the current limitation. Here, for the first time, a flexible, transparent zinc-nanofiber network anode electrode (Zn@Ni@AgNFs) is reported for an FE-ZiB device that yields a remarkable electrochemical performance of a high areal capacity of 174.82 mA h m² at 0.013 mA cm^-2 applied current density, high optical contrast (50%), and excellent mechanical flexibility. The fabricated FE-ZiB device also exhibits a high volumetric energy density of 378.8 W h m^-3 at a power density of 562.7 W m^-3 . Besides, the FE-ZiB demonstrates excellent electrochromic capability with a reversible color transition from a transparent in a discharged state (0.3 V) to a dark bluish-violet in a charged state (1.6 V). These results highlight a new pathway for the development of transparent batteries for smart wearable electronic devices.

Imine-Induced Metal-Organic and Covalent Organic Coexisting Framework with Superior Li-Storage Properties and Activation Mechanism

Due to the adjustable structure and the broad application prospects in energy and other fields, the exploration of porous organic materials [metal-organic polymers (MOPs), covalent organic frameworks (COFs), etc.] has attracted extensive attention. In this work, an imine-induced metal-organic and covalent organic coexisting framework (Co-MOP@COF) hybrid was designed based on the combination between the amino units from the organic ligands of Co-MOP and the aldehyde groups from COF. The obtained Co-MOP@COF hybrid with layer-decorated microsphere morphology exhibited good electrochemical cycling performance (a large reversible capacity of 1020 mAh g^-1 after 150 cycles at 100 mA g^-1 and a reversible capacity of 396 mAh g^-1 at 500 mA g^-1 ) as the anode for Li-ion batteries. The coexisting framework structure endowed the Co-MOP@COF hybrid with more surface area exposed in the exfoliated COF structure, which provided rapid Li-ion diffusion, better electrolyte infiltration, and effective activation of functional groups. Therefore, the Co-MOP@COF hybrid material achieved an enhanced Li storage mechanism involving multi-electron redox reactions, related to the Co^II center and organic groups (C=C groups of benzene rings and C=N groups), and furthermore improved electrochemical performance.

Regulating the Electronic Structure and Active Sites in Ni Nanoparticles by Coating N-Doped C Layer and Porous Structure for an Efficient Overall Water Splitting

Developing efficient and robust bifunctional electrocatalysts are in high demand for the production of hydrogen by water splitting. Engineering an electrocatalyst with a regulated electronic structure and abundant active sites is an effective way to enhance the electrocatalytic activity. Herein, N-doped C-encapsulated Ni nanoparticles (Ni@N-C) are synthesized through a traditional hydrothermal reaction, followed by pyrolyzing under an Ar/H₂ atmosphere. The electrochemical measurements and density functional theory (DFT) calculations reveal that the electron transfer between the Ni core and the N-C shell induces the electron density redistribution on Ni@N-C, which directly promotes the adsorption and desorption of H* on the N-doped carbon (N-C) layer and thus dramatically enhances hydrogen production. Taking advantage of the porous spherical structure and the synergistic effects between Ni and N-doped carbon (N-C) layer, we obtain a Ni@N-C electrocatalyst that exhibits remarkable hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activity with low overpotentials of 117 and 325 mV, respectively. Impressively, the assembled cell using Ni@N-C as both anode and cathode exhibits excellent activity as well as stable cyclability for over 12 h.

Hierarchically activated porous carbon derived from zinc-based fluorine containing metal-organic framework as extremely high specific capacitance and rate performance electrode material for advanced supercapacitors

In this work, a hierarchically activated porous carbon (APC) was synthesized using fluorine-containing metal-organic framework via facile combined carbonization and KOH activation treatments. The influences of activation conditions on the surface structures and electrochemical performance of APC were systematically studied. Afterwards, the electrochemical responses of APC electrode were further assessed from the cyclic voltammetry and galvanostatic charge-discharge examinations by 6 M KOH electrolyte. The as-obtained APC electrode delivered the high specific capacitances of 540.8 and 280 F g^-1 at 1 and 500 A g^-1, correspondingly with superior capacitance retention of 94% after 250,000 cycles even at 100 A g^-1, which is showing that its outstanding capacitance, remarkable rate capacity, and very-long cyclic life. Furthermore, the as-assembled APC-based symmetrical supercapacitor offers a superb energy density of 19 Wh kg^-1 at 182 W kg^-1, indicating its large-scale application. Thus, this work proposes a potential route to synthesize highly efficient porous carbon material for the future development of energy storage systems.

Boosting oxygen evolution reaction activity by tailoring MOF-derived hierarchical Co–Ni alloy nanoparticles encapsulated in nitrogen-doped carbon frameworks

The growing demand for sustainable energy has led to in-depth research on hydrogen production from electrolyzed water, where the development of electrocatalysts is a top priority. We here report a controllable strategy for preparing the cobalt–nickel alloy nanoparticles encapsulated in nitrogen-doped porous carbon by annealing a bimetal–organic framework. The delicately tailored hierarchical Co₂Ni@NC nanoparticles effectively realize abundant synergistic active sites and fast mass transfer for the oxygen evolution reaction (OER). Remarkably, the optimized Co₂Ni@NC exhibits a small overpotential of 310 mV to achieve a current density of 10 mA cm⁻² and an excellent long-term stability in alkaline electrolyte. Furthermore, the underlying synergistic effect mechanism of the Co–Ni model has been pioneeringly elucidated by density functional theory calculations.

The hierarchical Co₂Ni@NC nanoparticles realize fast mass transfer for the oxygen evolution reaction (OER). The synergistic effect between Co and Ni can effectively adjust the binding energy tending to an optimal value, further improving the energetics for the OER.

Highly efficient Co3O4/CeO2 heterostructure as anode for lithium-ion batteries

Co₃O₄ has been extensively studied as an anode material for lithium-ion batteries (LIBs) because of its high theoretical capacity. However, during the charging-discharging processes, the issues of large volume change and low electric conductivity arise, which significantly limit the practical applications of Co₃O₄. To solve these issues, a Co₃O₄/CeO₂ heterostructure derived from metal-organic frameworks (MOFs) was designed and synthesized through one-step microwave synthesis. Benefiting from the mesoporous structure and presence of hetero-components, Co₃O₄/CeO₂ having the molar ratio of Co/Ce = 5:1 (denoted as 5Co₃O₄/CeO₂) exhibits high reversible capacity and excellent cycling stability when used as an anode material for LIBs. Specifically, compared to a single-phase Co₃O₄ anode, which shows a capacity of 538.6 mAh/g after 100 cycles, 5Co₃O₄/CeO₂ exhibits a higher capacity (1131.2 mAh/g at 100 mA/g). This study provides a novel strategy for using rare earth components to modify electrode materials.

State-of-the-Art Electrode Materials for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) were investigated as recently as in the seventies. However, they have been overshadowed for decades, due to the success of lithium-ion batteries that demonstrated higher energy densities and longer cycle lives. Since then, the witness a re-emergence of the SIBs and renewed interest evidenced by an exponential increase of the publications devoted to them (about 9000 publications in 2019, more than 6000 in the first six months this year). This huge effort in research has led and is leading to an important and constant progress in the performance of the SIBs, which have conquered an industrial market and are now commercialized. This progress concerns all the elements of the batteries. We have already recently reviewed the salts and electrolytes, including solid electrolytes to build all-solid-state SIBs. The present review is then devoted to the electrode materials. For anodes, they include carbons, metal chalcogenide-based materials, intercalation-based and conversion reaction compounds (transition metal oxides and sulfides), intermetallic compounds serving as functional alloying elements. For cathodes, layered oxide materials, polyionic compounds, sulfates, pyrophosphates and Prussian blue analogs are reviewed. The electrode structuring is also discussed, as it impacts, importantly, the electrochemical performance. Attention is focused on the progress made in the last five years to report the state-of-the-art in the performance of the SIBs and justify the efforts of research.

Conversion of Co Nanoparticles to CoS in Metal-Organic Framework-Derived Porous Carbon during Cycling Facilitates Na2S Reactivity in a Na-S Battery

Room-temperature sodium-sulfur batteries have attracted wide interest due to their high energy density and high natural abundance. Polysulfide dissolution and irreversible Na₂S conversion are challenges to achieving high battery performance. Herein, we utilize a metal-organic framework-derived Co-containing nitrogen-doped porous carbon (CoNC) as a catalytic sulfur cathode host. A concentrated sodium electrolyte based on sodium bis(fluorosulfonyl)imide, dimethoxyethane, and bis(2,2,2-trifluoroethyl) ether is used to mitigate polysulfide dissolution. We tune the amount of Co present in the CoNC carbon host by acid washing. Significant improvement in reversible sulfur conversion and capacity retention is observed with a higher Co content in CoNC, with 600 mAh g^-1 and 77% capacity retention for CoNC and 261 mAh g^-1 and 56% capacity retention for acid-washed CoNC at cycle 50 at 80 mAh g^-1. Post-mortem X-ray photoelectron spectroscopy, transmission electron microscopy, and selected area electron diffraction suggest that CoS is formed during cycling in place of Co nanoparticles and CoN₄ sites. Raman spectroscopy suggests that CoS exhibits a catalytic effect on the oxidation of Na₂S. Our findings provide insights into understanding the role Co-based catalysts play in sulfur batteries.

Co3O4 nanoparticles embedded in nitrogen-doped graphitic carbon fibers as a free-standing electrode for promotion of lithium ion storage with capacitive contribution

Here, we wrap Co₃O₄ nanoparticles with nitrogen-doped graphitic carbon nanofibers (Co₃O₄@NGFs) as a self-standing electrode for lithium-ion batteries. In this structure, graphitic carbon acts as a composite framework that enhances conductivity, accommodates volume expansion and increases contact with the electrolyte. Meanwhile, the porosity of Co₃O₄@NGFs not only facilitates rapid electron transfer, but also exposes more active sites for lithium storage.

Aerobic Oxidation of 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid over Holey 2 D Mn2 O3 Nanoflakes from a Mn-based MOF

The aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA), a promising renewable monomer to produce bio-based polymers such as polyethylene furanoate (PEF), has recently emerged as the subject of increasing interest. Here, holey 2 D Mn₂ O₃ nanoflakes were obtained by a facile thermal treatment of a Mn-based metal-organic framework (MOF) precursor. The structural and morphological properties of the nanoflakes were characterized by powder XRD, FTIR, SEM and TEM to explore the formation process. It was inferred that the linker loss in the MOF precursor and the oxidation of the Mn cation induced by the heat-treatment in air were responsible for the formation of holey 2 D Mn₂ O₃ nanoflakes. The specific morphology and redox cycle of the Mn cation on the surface endowed the synthesized nanoflakes with promising performance on the selective oxidation. The obtained nanoflakes calcined at 400 °C (M400) afforded over 99.5 % yield of FDCA at complete conversion of HMF, which is superior to the catalytic activity of commercial Mn₂ O₃ and activated MnO₂ . To our knowledge, Mn₂ O₃ exhibiting such a high performance on the aerobic oxidation of HMF to FDCA has not yet been reported. Based on the investigation of the experimental parameters, a plausible reaction mechanism was proposed.

Amino-functionalized MOF derived porous Fe3O4/N-doped C encapsulated within a graphene network by self-assembling for enhanced Li-ion storage

A graphene-wrapped porous Fe₃O₄/N-doped C composite was synthesized by an electrostatic interaction induced self-assembly process, showing an excellent electrochemical performance.

Application of MOF-derived transition metal oxides and composites as anodes for lithium-ion batteries

Research progress of MOF-derived metal oxides and composites in lithium ion batteries has been presented based on different organic linkers.

Three-dimensional porous Co3O4-CoO@GO composite combined with N-doped carbon for superior lithium storage

Transition metal oxides (TMOs) as anode materials have potential for lithium-ion batteries (LIBs). However, the poor rate capacity and cycle stability restrict its application. Herein, we demonstrate a facile one-step hydrothermal method to construct a three-dimensional porous conductive network structure, which consists of thin-layered graphene, ultrafine Co₃O₄-CoO nanoparticles and nitrogen-doped carbon. This unique structure can effectively prevent particle agglomeration and cracking caused by volume expansion, provide fast passage for lithium ion/electron transport during cycling and improve the electrical conductivity of the electrode. Moreover, the electrochemical kinetic analysis proves that this is a process dominated by pseudocapacitive behavior. Consequently, the N-C@Co₃O₄-CoO@GO hybrid electrode delivers an ultrahigh capacity of 1 273.1 mA h g^-1 at 0.1 A g^-1 and superior rate performance (725.1 mA h g^-1 at 5 A g^-1). Additionally, it exhibits a high reversible cycling capacity of 787.4 mA h g^-1 at 1 A g^-1 over 600 cycles and even maintains excellent cycling stability for a ultra-long cycles at 5 A g^-1. This work provides a feasible strategy for fabricating the N-C@Co₃O₄-CoO@GO composite as a promising high-performance TMOs anode for LIBs.

A two-dimensional assembly of ultrafine cobalt oxide nanocrystallites anchored on single-layer Ti3C2Tx nanosheets with enhanced lithium storage for Li-ion batteries

Recently, Ti-based MXenes were expected to compete with graphene and other carbonaceous materials towards Li-ion batteries (LIBs) due to their two-dimensional (2D) open structure, cost efficiency, superior conductivity and low Li⁺ diffusion barrier. However, the relatively moderate capacity and aggregation tendency hamper their practical applications in next-generation LIBs. Herein, we explore for the first time a scalable bottom-up approach to fabricate a series of Co₃O₄@single-layer Ti₃C₂T_x (s-Ti₃C₂T_x) hybrids, where numerous homogeneous Co₃O₄ nanocrystallites (NCs), serving both as a spacer and electroactive phase, are anchored uniformly on the surface of s-Ti₃C₂T_x nanosheets (NSs) through the Co-O-Ti interfacial bonds. Furthermore, detailed experimental analyses clearly shed light upon the formation mechanism of the hybrid Co₃O₄@s-Ti₃C₂T_x NSs. Thanks to the structural and compositional merits, the 2D Co₃O₄@s-Ti₃C₂T_x NSs even exhibit a remarkable high-rate capacity of ∼223 mA h g^-1 at an ultra-high current density of 10 A g^-1, and a long-span cycle life with a high reversible capacity of 550 mA h g^-1 at 1 A g^-1 after 700 consecutive cycles. Corresponding density functional theory calculation further confirms that the Co-O-Ti interfacial function leads to an even higher pseudocapacitive contribution and faster lithium storage behavior due to the enhanced interfacial electron transfer.

Co3O4 hollow nanospheres/carbon-assembled mesoporous polyhedron with internal bubbles encapsulating TiO2 nanosphere for high-performance lithium ion batteries

Co₃O₄ hollow nanospheres 15 nm in the diameter were assembled to the mesoporous polyhedron together with carbon. Within the Co₃O₄ polyhedrons, the bubbles 300-500 nm in diameter were uniformly generated. Every bubble further encapsulated one TiO₂ nanosphere, forming a unique sphere-bubble structure. The specific surface area and the pore volume were calculated to be 97.85 and 0.31 cm³ g^-1. When evaluated as anode material for lithium ion batteries, the as-prepared material exhibited superior lithium storage properties with high specific capacity, excellent cycling stability and good rate capability. After 400 cycles, the discharge capacity of 609 mAh g^-1 was still delivered at current density of 335 mA g^-1. Even at a high current density of 2000 mA g^-1, the reversible capacity reached 296 mAh g^-1. The outstanding electrochemical performance was attributed to the unique hybrid structure, which avoids nanomaterial aggregation, promotes ion diffusion and electron transfer, accommodates volume change of Co₃O₄ during (de)lithiation process, enhances structure strength, cycling stability and space utilization ratio of the hollow material.

Mesoporous ZnCo2O4/rGO nanocomposites enhancing sodium storage

In this study, mesoporous ZnCo₂O₄/rGO nanocomposites were favorably synthesized via a simple solvothermal technique. As a prospective anode material for sodium-ion batteries, the resulting ZnCo₂O₄/rGO-II nanocomposite exhibited superior electrochemical sodium storage performance with predominant specific capacity, favorable cyclability and ascendant rate capability. For example, an outstanding discharge capacity of 210.5 mAh g^-1 was delivered at a current density of 200 mA g^-1. Notably, the nanocomposite could yield a discharge capacity of 101.7 mAh g^-1 at a current density of 1000 mA g^-1 after 500 loops, which certifies its superior capacity retention and predominant cycling stability. The boosted performance of the anode materials is due to the mutual synergistic effect resulting from a combination of the mesoporous ZnCo₂O₄ nanospheres and conducting reduced graphene oxide nanosheets.

ZIF-67-Derived N-Doped Co/C Nanocubes as High-Performance Anode Materials for Lithium-Ion Batteries

Co nanoparticles embedded in nitrogen-doped carbon nanocubes (Co/NCs) for applications as anode materials in rechargeable lithium-ion batteries were synthesized by calcining Co-based metal-organic framework. Sizes of Co nanoparticles were ∼15 nm according to X-ray diffraction (XRD) and transmission electron microscopy. Electrochemical performances of the as-prepared anode nanocube composite at 700 °C showed a high initial capacity of 1375.1 mAh g^-1 in the voltage range of 0.01-3.0 V at the current rate of 0.1 A g^-1. After 100 cycles, capacity remained at 688.6 mAh g^-1. Thereinto, the role of Co nanoparticles in electrochemical reaction was also elucidated by in situ XRD experiment. Capacity increase of Co/NCs at the high currents was observed, which are potentially caused by the activation of electrode and pseudocapacitance during cycling. High surface area and abundant mesopores contributed to the improved electrochemical performances of the anode, providing numerous pathways and sites for Li⁺ transfer and storage and accordingly contributing to pseudocapacitance capacity.

Hollow core–shell ZnO@ZIF-8 on carbon cloth for flexible supercapacitors with ultrahigh areal capacitance

A hollow core–shell hetero-structured electrode (PANI/ZnO@ZIF-8-CC) is designed and synthesized via a ‘root-etch-wrap’ process for flexible supercapacitors. The unique structure, in situ growth strategy and synergistic effects endow PANI/ZnO@ZIF-8-CC with ultrahigh areal capacitance and good cycling stability.

Construction of Bimetallic ZIF-Derived Co-Ni LDHs on the Surfaces of GO or CNTs with a Recyclable Method: Toward Reduced Toxicity of Gaseous Thermal Decomposition Products of Unsaturated Polyester Resin

This work proposed an idea of recycling in preparing Co-Ni layered double hydroxide (LDH)-derived flame retardants. A novel and feasible method was developed to synthesize CO-Ni LDH-decorated graphene oxide (GO) and carbon nanotubes (CNTs), by sacrificing bimetal zeolitic imidazolate frameworks (ZIFs). Organic ligands that departed from ZIFs were recyclable and can be reused to synthesize ZIFs. ZIFs, as transitional objects, in situ synthesized on the surfaces of GO or CNTs directly suppressed the re-stacking of the carbides and facilitated the preparation of GO@LDHs and CNTs@LDHs. As-prepared hybrids catalytically reduced toxic CO yield during the thermal decomposition of unsaturated polyester resin (UPR). What is more, the release behaviors of aromatic compounds were also suppressed during the pyrolysis process of UPR composites. The addition of GO@LDHs and CNTs@LDHs obviously inhibited the heat release and smoke emission behaviors of the UPR matrix during combustion. Mechanical properties of the UPR matrix also improved by inclusion of the carbides derivatives. This work paved a feasible method to prepare well-dispersed carbides@Co-Ni LDH nanocomposites with a more environmentally friendly method.

Transition-Metal-Triggered High-Efficiency Lithium Ion Storage via Coordination Interactions with Redox-Active Croconate in One-Dimensional Metal-Organic Anode Materials

Coordination polymers (CPs) have powerful competence as anode materials for lithium-ion batteries (LIBs) owing to their structural diversity, tunable functionality, and facile and mild synthetic conditions. Here, we show that two isostructural one-dimensional croconate-based CPs, namely, [M(C₅O₅)(H₂O)₃]_n (M = Mn for 1 and Co for 2; C₅O₅^2- = croconate dianion), can work as high-performance electrode materials for rechargeable LIBs. By means of the coordination between the redox-active transition metal ion and the ligand, the anode materials were stable in the electrolyte and showed high capacities, impressive rate capabilities, and excellent cycling performance during the discharging/charging processes. The chain-based supramolecular structures of the CPs also make them stand out from a crowd of porous three-dimensional molecular materials due to their free channels between the chains for lithium ion diffusion. When tested in a voltage window of 0.01-2.4 V at 100 mA g^-1, CPs 1 and 2 demonstrated high discharge specific capacities of 729 and 741 mA h g^-1, respectively. The synergistical redox reactions on both metal centers and the organic moieties play a crucial role in the high electrochemical performance of CPs 1 and 2. After undergoing elevated discharging/charging rates to 2 A g^-1, the electrodes could finally recover their capabilities as those in the initial stage when the current rate was back to 100 mA g^-1, indicating excellent rate performance and outstanding cycling stabilities of the materials.

Facile synthesis of Co3O4 nanosheets from MOF nanoplates for high performance anodes of lithium-ion batteries

Co₃O₄ nanosheets are readily synthesized from a nanoplate MOF precursor and showed a remarkable performance as an anode material for lithium-ion batteries.

A photochromic zinc-based coordination polymer for a Li-ion battery anode with high capacity and stable cycling stability

A zinc-based coordination polymer with photochromic 4,4′-bipyridinium derivatives as redox active building units is demonstrated as an anode material for Li-ion batteries.

Metal-Organic Framework-Derived Materials for Sodium Energy Storage

Recently, sodium-ion batteries (SIBs) are extensively explored and are regarded as one of the most promising alternatives to lithium-ion batteries for electrochemical energy conversion and storage, owing to the abundant raw material resources, low cost, and similar electrochemical behavior of elemental sodium compared to lithium. Metal-organic frameworks (MOFs) have attracted enormous attention due to their high surface areas, tunable structures, and diverse applications in drug delivery, gas storage, and catalysis. Recently, there has been an escalating interest in exploiting MOF-derived materials as anodes for sodium energy storage due to their fast mass transport resulting from their highly porous structures and relatively simple preparation methods originating from in situ thermal treatment processes. In this Review, the recent progress of the sodium-ion storage performances of MOF-derived materials, including MOF-derived porous carbons, metal oxides, metal oxide/carbon nanocomposites, and other materials (e.g., metal phosphides, metal sulfides, and metal selenides), as SIB anodes is systematically and completely presented and discussed. Moreover, the current challenges and perspectives of MOF-derived materials in electrochemical energy storage are discussed.

Rationally designed hierarchical porous CNFs/Co3O4 nanofiber-based anode for realizing high lithium ion storage

To achieve a high power density of lithium-ion batteries, it is essential to develop anode materials with high capacity and excellent stability. Cobalt oxide (Co₃O₄) is a prospective anode material on account of its high energy density. However, the poor electrical conductivity and volumetric changes of the active material induce a dramatic decrease in capacity during cycling. Herein, a hierarchical porous hybrid nanofiber of ZIF-derived Co₃O₄ and continuous carbon nanofibers (CNFs) is rationally constructed and utilized as an anode material for lithium-ion batteries. The PAN/ZIF-67 heterostructure composite nanofibers were first synthesized using electrospinning technology followed by the in situ growth method, and then the CNFs/Co₃O₄ nanofibers were obtained by subsequent multi-step thermal treatment. The continuous porous conductive carbon backbone not only effectively provides a channel to expedite lithium ion diffusion and electrode transfer, but also accommodates volume change of Co₃O₄ during the charge–discharge cycling process. The electrode exhibits a high discharge capacity of 1352 mA h g⁻¹ after 500 cycles at a constant current density of 0.2 A g⁻¹. Additionally, the composites deliver a discharge capacity of 661 mA h g⁻¹ with a small capacity decay of 0.078% per cycle at a high current density of 2 A g⁻¹ after 500 cycles. This hierarchical porous structural design presents an effective strategy to develop a hybrid nanofiber for improving lithium ion storage.

Hierarchical porous CNFs/Co₃O₄ nanofiber is rationally designed and constructed as an anode for achieving high capacity and stable lithium ion batteries.

Ultrasmall MnO Nanoparticles Supported on Nitrogen-Doped Carbon Nanotubes as Efficient Anode Materials for Sodium Ion Batteries

Sodium ion batteries (SIBs) have attracted increasing attentions as promising alternatives to lithium ion batteries (LIBs). Herein, we design and synthesize ultrasmall MnO nanoparticles (∼4 nm) supported on nitrogen-doped carbon nanotubes (NDCT@MnO) as promising anode materials of SIBs. It is revealed that the carbonization temperature can greatly influence the structural features and thus the Na-storage behavior of the NDCT@MnO nanocomposites. The synergetic interaction between MnO and NDCT in the NDCT@MnO nanocomposites provides high rate capability and long-term cycling life due to high surface area, electrical conductivity, enhanced diffusion rate of Na⁺ ions, and prevented agglomeration and high stability of MnO nanoparticles. The resulting SIBs provide a high reversible specific capacity of 709 mAh g^-1 at a current density of 0.1 A g^-1 and a high capacity of 536 mAh g^-1 almost without loss after 250 cycles at 0.2 A g^-1. Even at a high current density of 5 A g^-1, a capacity of 273 mAh g^-1 can be maintained after 3000 cycles.