MOF-derived Metal Research Articles

Metal-organic framework materials for supercapacitors

Supercapacitor (SCs), known as outstanding electrical storage capacity, which times more than the batteries and fuel cells, recharges with a large amount of released power, fast overpassing the gap between capacitors and batteries, and widely be employed in the field of energy storage. Metal-organic frameworks (MOFs) attract intensive attention as electrode materials in supercapacitor application, owing to their ultrahigh porosity, adjustable distribution of pore size, convenient synthesis, great structural adaptability, etc. Composited with different materials, such as carbons family, metal oxide, can improve pristine MOFs’ conductivity and chemical stability, which are all-important as electrode materials in SCs. This review comprehensively summarizes the common synthesis methods of four kinds of MOFs materials: the pristine MOFs, MOFs composites, MOFs-derived nanoporous carbons, and MOFs-derived metal oxides. Also, the applications of these four kinds of materials in SCs electrode materials are systematically introduced. Furthermore, a perspective on MOFs materials in the field of SCs is discussed.

Developing metal‐organic framework‐based composite for innovative fuel cell application: An overview

In this work, metal-organic frameworks (MOFs), known as porous carbon, organic ligands, and crystalline materials have been reviewed as it consists of excellent properties, including high surface area, porosity, functional consistency, and uniform structure. The structural of MOFs, including secondary building units, open metal sites, pore sizes, functional materials, and development of MOF have been extensively studied as it helps to conduct electricity and promising good efficiency. To improve the performance in fuel cell applications, especially in catalytic activity such as oxygen reduction reaction and proton exchange membrane, the combination of MOF and other materials such as MOF/carbon material composites, MOF/metal nanoparticles (NPs), and MOF/biocomposites has been discussed in details, which can increase the potential and efficiency of catalysts. MOF-derivatives, including MOF-derived porous carbon, MOF-derived NPs, MOF-derived metal oxides, and MOF-derived metal phosphide, has been provided in this review as it has its advantages; (a) increase the mass density of active sites, (b) increase intrinsic activity of active sites, (c) increase electrocatalyst conductivity (d), and accelerate electron transfer. Hence, it can produce materials with high thermal and chemical stability, embracing metal sites, and efficiency in active sites. These advantages have made the MOF a promising material to increase efficiency in fuel cell application and attract interest to further expand in other fields in the future.

Metal-organic framework derived zirconium oxide/carbon composite as an improved supercapacitor electrode

The pyrolysis of metal-organic frameworks (MOFs) is an effective strategy for the synthesis of novel nanoporous structures for energy storage applications. In this work, the preparation of a zirconium oxide/carbon (ZrO2/C) nanocomposite via the pyrolysis of UiO-66 (a zirconium-based MOF) is reported for the first time. These MOF-derived metal oxide/carbon (ZrO2/C) materials have a great advantage in the case of supercapacitor applications over other MOFs or their derivatives as they do not need any external conductive agent. The ZrO2/C electrode exhibits an excellent electrochemical performance, delivering a specific capacitance of 241.5 F/g at 1 A/g current density. A 2 V symmetrical supercapacitor device is also prepared by employing a solid-state polymer gel electrolyte. The assembled device of ZrO2/C electrode has delivered a high energy density of around 29 Wh/kg (at a high power density of 1.5 kW/kg) while retaining almost 97% of the specific capacitance even after 2000 continuous charge/discharge cycles.

Photocatalytic conversion of sodium lignosulfonate into vanillin using mesoporous TiO2 derived from MIL-125

Mesoporous TiO2 with regular pancake-like morphology was synthesized by facile calcination of MIL-125 (MIL = Materials of Institut Lavoisier) at different temperatures. The optimal sample MT400 (calcination at 400 °C) is composed of nanoparticles with a size of about 10 nm and mesopores of about 4–12 nm. Its specific surface area can reach up to 174 m2 g−1. In the photocatalytic conversion of sodium lignosulfonate, the yield of vanillin over MT400 is 2.1 mg/g, obviously superior to that over P25 TiO2 (0.27 mg/g). MT400 with a large specific surface area offers sufficient active sites, and its mesoporous structure provides pathways for the transport of charge carriers and products, giving a satisfactory photocatalytic performance for vanillin generation. It is proved that h+ and ·O2− play the key role for vanillin generation from sodium lignosulfonate. This work indicates that MOF-derived metal oxides hold great promise in the application of biomass (photo)catalytic valorization.

Ce-MOF derived ceria: Insights into the Na-ion storage mechanism as a high-rate performance anode material

Cerium-based metal–organic framework (Ce-MOF-808) derived CeOx/C (1≤x≤2) nanocomposite material is applied as an anode material for sodium-ion batteries. Cubic phase structure ceria within 5 nm of grain consisted nanocubes are predicted from physical and morphological studies. MOF template is converted into the carbon during the calcination process and promotes the metal oxide conductivity. The electrochemical performance of Ce-MOF-808-derived CeOx/C nanocomposites exhibit a sodium ion reversible discharge capacity of 446 mAh g−1 at a current density of 100 mA g−1 and sustains 256 mAh g−1 over 600 cycles. The capacity contribution behavior, kinetics performance and Na-ion storage electrochemical reaction mechanism are investigated through cyclic voltammetry, electrochemical impedance and ex-situ X-ray diffraction/X-ray photoelectron spectroscopy analyses. The contribution of highly stable pseudocapacitive nature and oxygen vacancies-based conversion of Ce reveal a remarkable cyclic and rate performance. Thus, this work provides in-depth analysis and utilization of MOF-derived metal oxide nanocomposite for high-performance energy storage applications.

Phosphorization Engineering on Metal-Organic Frameworks for Quasi-Solid-State Asymmetry Supercapacitors.

Porous carbon and metal oxides/sulfides prepared by using metal-organic frameworks (MOFs) as the precursors have been widely applied to the realm of supercapacitors. However, employing MOF-derived metal phosphides as positive and negative electrode materials for supercapacitors has scarcely been reported thus far. Herein, two types of MOFs are used as the precursors to prepare CoP and FeP4 nanocubes through a two-step controllable heat treatment process. Due to the advantages of composition and structure, the specific capacitances of FeP4 and CoP nanocubes reach 345 and 600 F g-1 at the current density of 1 A g-1 , respectively. Moreover, a quasi-solid-state asymmetric supercapacitor is assembled based on charge matching principle by employing CoP and FeP4 nanocubes as the positive and negative electrodes, respectively, which exhibits a high energy density of 46.38Wh kg-1 at the power density of 695 W kg-1 . Furthermore, a solar-charging power system is assembled by combining the quasi-solid-state asymmetric supercapacitor and monocrystalline silicon plates, substantiating that the device can power the toy electric fan. This work paves a practical way toward the rational design of quasi-solid-state asymmetry supercapacitors systems affording favorable energy density and long lifespan.

Prussian blue analogue derived low-crystalline Mn2O3/Co3O4 as high-performance supercapacitor electrode

Metal oxide-based supercapacitors have been widely studied due to their high theoretical specific capacitance. Among many preparation methods of metal oxides, the annealing treatment of metal-organic frameworks (MOFs) has unique advantages in designable and well-controlled structure, and this approach is regarded to be suitable for preparing the metal oxides with high crystallinity. At present, it is still a great challenge to obtain low-crystalline MOFs-derived metal oxides. In this study, we have skillfully taken advantage of polyvinyl pyrrolidone (PVP) in Mn-based Prussian blue analogue (PBA) and formed the low-crystalline Mn2O3/Co3O4 composite by an annealing process. The presence of PVP can weaken the crystallization of metal oxides during the annealing process and create structural disorder. The as-prepared low-crystalline Mn2O3/Co3O4 has an excellent specific capacitance of 478.7 F g−1 at a current density of 1 A g−1, which is 131.7% higher than the high-crystalline counterpart. Moreover, this material exhibits outstanding cycling stability (116.4% capacitance retention after 2500 cycles). The asymmetric supercapacitor consisting of low-crystalline Mn2O3/Co3O4 as the positive electrode and nitrogen-doped graphene hydrogel as the negative electrode delivers an energy density of 32.8 Wh kg−1 at a power density of 1190.1 W kg−1. The superior electrochemical performances are mainly ascribed to the formation of low-crystalline Mn2O3/Co3O4 that provides more reversible active sites and accelerates ion diffusion. It is expected to open up a new avenue to the preparation of low-crystalline metal oxides for electrochemical energy storage.

Highly sensitive H2S sensors based on metal-organic framework driven γ-Fe2O3 on reduced graphene oxide composites at room temperature

γ-Fe2O3 as an excellent materials has been extensively used in gas-sensing. However, the γ-Fe2O3 gas-sensors demands for high working temperatures and shows poor selectivity. In this work, we developed a high-sensitive γ-Fe2O3/rGO gas-sensor for H2S at room temperature. γ-Fe2O3/rGO composite was formed by highly dispersed γ-Fe2O3 octahedrons derived from MIL-88 on reduced graphene oxide (rGO). Compared with the bare γ-Fe2O3 sensor, the arranged γ-Fe2O3/rGO composites sensors had enhanced gas-sensing performance evidently for H2S. It was noted that the optimized γ-Fe2O3/rGO composite embraces unparalleled sensitivity for H2S (Rair/Rgas = 520.73, 97 ppm) but few responses to NH3, CHCl3, NO, SO2 and HCHO. γ-Fe2O3 realizes gas detection based on the bulk resistance effect, while the gas-sensitive detection mechanism of the rGO composites was dominated by the surface-controlled type. The outstanding H2S sensing performance of γ-Fe2O3/rGO composites sensors was attributed to the excellent conductivity and abundant active sites of two-dimensional rGO. These results provide a method that can effectively enhance the gas sensor performance of MOF-derived metal oxide semiconductors.

MOFs-derived metal oxides inlayed in carbon nanofibers as anode materials for high-performance lithium-ion batteries

The lithium storage performance of metal oxides often suffer rapid capacity fading and poor rate performance due to their huge volume expansion during repeated charge and discharge processes. Herein, a facile strategy was adopted for constructing a three-dimensional (3D) interconnected conductive network. Metal-organic frameworks (MOFs)-derived metal oxides (Fe2O3, ZnO) were inlayed in carbon nanofibers through electrospinning and subsequent carbonization processes. As lithium-ion storage materials, the MOFs-derived metal oxide composite nanofibers exhibited a high specific capacity and an excellent rate capability due to the unique structural characteristics of high electrical conductivity, additional Li-storage sites, and defined frameworks. The Fe2O3@polyacrylonitrile (PAN) and ZnO@PAN composite nanofibers deliver high initial specific capacities of 1571.4 and 1053.8 mAh g−1 at 50 mA g−1, respectively. Moreover, Fe2O3@ PAN and ZnO@PAN composite nanofibers retained reversible specific capacities of 506.6 and 455.4 mAh g−1 at 1000 mA g−1 after 500 cycles, respectively. Additionally, the diffusion kinetics analysis indicated a relatively fast Li-ion diffusivity for the composite nanofibers.

MOFs-derived Co3O4 loaded hollow In2O3 nanofibers with greatly enhanced acetone sensing performance

In this paper, metal-organic frameworks (MOFs)-derived Co3O4 were easily functionalized on In2O3 nanofibers (NFs) by electrospinning followed a calcination at 600 °C in air. The influences of doping content, morphology, and operating temperature on the acetone sensing performances of In2O3 based NFs were comprehensively studied. Our results showed that the 20 wt% Co3O4-In2O3 NFs exhibited outstanding acetone sensing properties at 300 °C. Exactly, it showed a high response to acetone (S∼43.67 @ 100 ppm acetone), which was ∼22 times larger than that of pristine In2O3 NFs. On the same time, it exhibited a short response time (∼13 s). The excellent acetone sensing properties of MOFs-derived Co3O4-In2O3 NFs can be explained by the formation of p-n junction between Co3O4 and In2O3. Our work offers a facile and cost-effective approach to load MOFs-derived Co3O4 on other metal oxides based NFs as a promising gas sensing material and shows the prospects of MOFs-derived metal oxides loaded in metal oxide NFs used for gas sensors.

MOF-Templated Metal Oxides Sensitized with Quantum Dots Heterojunction for Efficient Solar Fuels Generation

The separation and transport of photogenerated charges carriers are two of the most crucial factors that determine the overall efficiency of photoelectrochemical (PEC) systems. Various strategies have been exploited for achieving efficient charge separation and transfer. Among them, the design of semiconductor heterojunction has been shown to be one of the most effective approaches. Metal oxides, such as TiO2, are the among the most common materials for water splitting. However, the control of phase alignment and the interface structure remains a challenge. A promising solution is to use a template approach by employing metal-organic frameworks (MOF) which are of broad interest as a new class of organic-inorganic hybrid materials and have been intensely exploited in various fields due to their unique physical and chemical properties. Furthermore, common metal oxides, such TiO2 or NiO have limited absorption of sunlight due to their large intrinsic band gap (i.e. TiO2 anatase: 3.2 eV) which hinders effective use in solar water splitting. To extend the absorption range of the MOF-templated metal oxides in the visible and near-infrared range, we employed metal chalcogenide QDs as sensitizers.In this presentation, for example, we explore a simple metal organic framework (MOF)-derived synthesis to obtain a controlled mixed-phase (anatase and rutile) of TiO2 nanoparticles, which retain the MOF crystal morphology. After sensitization with core@shell CdSe@CdS QDs, the mixed-phase TiO2 film exhibited a remarkable photocurrent of 10.72 mA/cm2 and long-term stability, with a retained value of more than 78.1% after two hours. Compared with commercial TiO2 films, the MOF-derived TiO2 film sensitized by core-shell CdSe@CdS QDs, showed an enhanced PEC device stability of +42.1% and PEC performance of +47.6%. The enhanced performance is due to the presence of mixed rutile/anatase phases, that creates a favorable band energy alignment for the separation of the photogenerated charges. The proposed photoanode based on MOF-derived metal oxide is an efficient strategy to improve the efficiency of the heterojunction-based PEC system for hydrogen generation. Furthermore, the combined use of QDs can extend the absorption range exploiting a larger part of the sun spectrum. Figure 1

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.

Metal-organic frameworks derived porous carbon, metal oxides and metal sulfides-based compounds for supercapacitors application

The energy storage field has witnessed a dramatic expansion in terms of short charging time of supercapacitors, especially in the highly active electrode materials. Metal-organic frameworks (MOFs) materials have been extensively applied as precursors or templates for the synthesis of carbon, metal oxides/sulfides-based compounds as high-performance electrodes in supercapacitors. The MOFs-derived materials can be broadly divided into two groups: MOFs-derived porous carbon and MOFs-derived metal oxide/sulfide compounds. These MOFs-derived materials are characterized by unique porous structures, controllable structures, high surface area, good conductivity (MOFs-derived carbon) and outstanding electrochemical stability, meeting the requirements of the desirable specific capacitance and long-term cyclic performance of both electrochemical double layer capacitors and pseudocapacitors. However, MOFs-derived materials still suffer from the complex synthesis process and high production cost of MOFs precursors, difficulties in mass production, and unstable structure in highly corrosive electrolyte. In addition, the electrical conductivity of MOFs-derived metal oxides/sulfides needs to be further improved. In this review, we summarize the recent progresses in the development of MOFs-derived porous carbons and metal oxide/sulfide compounds and their applications in supercapacitors. The prospects and challenges of MOFs-derived carbon and metal oxide/sulfide compounds as highly effective and durable electrodes in supercapacitors are discussed.

Controlled thermolysis of MIL-101(Fe, Cr) for synthesis of FexOy/porous carbon as negative electrode and Cr2O3/porous carbon as positive electrode of supercapacitor

In the present study, two kinds of metal oxide/carbon nanocomposite were prepared through calcination of MIL-101(Fe, Cr). The morphological and structural properties of the specimens were investigated using X-ray diffraction, Fourier-transform infrared spectroscopy, Brunauer, Emmett, and Teller analysis, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy. The electrode materials were also electrochemically investigated using cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy techniques in 6 M KOH electrolyte. Because of synergistic effect of metal oxides and carbon, the obtained samples showed excellent performance; in a way that Cr2O3/C and FexOy/C showed high specific capacitance of 420 F g−1 and 114 F g−1 at current density of 2 A g−1, respectively. The Cr2O3/C electrode also displayed high rate capability even at scan rate of 1500 mV s−1. Moreover, we successfully developed an asymmetric supercapacitor in which Cr2O3/C served as positive electrode and FexOy/C served as negative electrode. The asymmetric device can deliver an energy density of 9.6 W h kg−1 and power density of 8000 W kg−1, with 93% capacitance retention after 3000 charge–discharge cycles. These outcomes show that the MOF-derived metal oxide/carbon composite can be regarded as a promising development for advanced electrode materials for applying in supercapacitors.

A review of performance optimization of MOF-derived metal oxide as electrode materials for supercapacitors

Metal-organic frameworks (MOFs), as new class of porous materials, are constructed by inorganic metal centers and bridging organic links. Recently, MOFs have been proved to be effective templates for preparing metal oxides with large surface areas and controlled shape by directly annealing in air. There are lots of reports about metal-organic framework-derived metal oxides as electrode materials for supercapacitors. Metal-organic framework-derived metal oxides can offer higher capacitances compared with that prepared by other synthetic methods, likely attribute to high surface areas and optimal pore sizes. However, at present, the specific capacitances of MOF-derived metal oxides received are far lower than theoretical values, and the cycle numbers could not meet practical demands. Accordingly, much effort has been made to improve the performance by further modifying MOFs. Thus, this paper focused on the advances in performance optimization of MOF-derived metal oxide as electrode materials for supercapacitors as follows: Dual metal MOF-derived binary metal oxides. Metal oxides with 2 metal cations possess better electrical conductivity and richer redox active sites than single metal oxides. Metal-organic framework-derived carbon/metal oxide composites (MO@C) or graphene/MOF-derived graphene/metal oxide composites. Doping carbon not only facilitate transportation of electrodes but also contribution to extra double-layer capacitance. Hybrid MOF-derived metal oxide composites (MO@MO). Metal oxide composites can produce some synergistic effects that the individuals cannot provide. Metal-organic framework-derived metal oxides with a hollow structure. The Hollow structure could shorten ion diffusion distance and adapt to volume expansion generated during the ion intercalated/extracted process.

Facile synthesis of metal-organic framework-derived Co3O4 with different morphologies coated graphene foam as integrated anodes for lithium-ion batteries

A facile strategy to fabricate the composites including metal-organic framework (MOF)-derived Co3O4 with different morphologies and graphene foam (GF) is proposed in this work. The resulting Co3O4/GF materials can be directly employed as integrated anodes of lithium-ion batteries, and their electrochemical performances are significantly superior to pure Co3O4 in specific capacities, long-cycle stabilities and rate performances. The enhanced properties originate from the synergistic interaction between GF and MOF-derived metal oxides, where GF provides high conductivity, large specific surface area and excellent mechanical property, whereas metal oxides contribute to high electrochemical activities. The effect of Co3O4 morphologies in the composites on the electrochemical properties is also discussed. Benefitting from the unique structure feature, the leaf-Co3O4/GF integrated electrode delivers a high capacity of 986 mA h g−1 after 250 cycles at a current density of 100 mA g−1, which is better than those observed in the block- and rod-Co3O4/GF samples. Even measured at 2 A g−1, the leaf-Co3O4/GF electrode still shows a capacity of around 340 mA h g−1. The relatively high electrochemical behaviors are attributed to the unique leaf-like structure of Co3O4 in the composite.

Co/Fe-bimetallic organic framework-derived carbon-incorporated cobalt–ferric mixed metal phosphide as a highly efficient photocatalyst under visible light

A new bimetallic Co/Fe-MOF was synthesized and phosphatized to produce a visible-light-active Co/Fe binary metal phosphide embedded in a mesoporous carbon matrix (denoted by CoP/Fe2P@mC). The results of X-ray diffraction and photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy reveal the formation of CoP and Fe2P nanoparticles together with the Co and Fe metallic state. Combining the high electron–hole separation rate of Fe2P@mC, fast electron transfer of CoP@mC, and the strong adsorption of mesoporous carbon, the as-prepared CoP/Fe2P@mC catalyst exhibits substantially enhanced photocatalytic activity toward rhodamine B (RhB) degradation under visible light irradiation. Visible light harvesting efficiency is enhanced by the suitable bandgap structure of the CoP/Fe2P@mC photocatalyst. Moreover, the possible photocatalytic mechanism of CoP/Fe2P@mC toward RhB degradation was proposed on the basis of radical trapping and electron spin resonance results. This finding illustrates a potential utilization of bimetallic MOF-derived metal phosphide as a photocatalyst to remove dye pollutants in the environment.

MOF-Derived Metal Oxide Composites for Advanced Electrochemical Energy Storage.

Over the past two decades, metal-organic frameworks (MOFs), a type of porous material, have aroused great interest as precursors or templates for the derivation of metal oxides and composites for the next generation of electrochemical energy storage applications owing to their high specific surface areas, controllable structures, and adjustable pore sizes. The electrode materials, which affect the performance in practical applications, are pivotal components of batteries and supercapacitors. Metal oxide composites derived from metal-organic frameworks possessing high reversible capacity and superior rate and cycle performance are excellent electrode materials. In this Review, potential applications for MOF-derived metal oxide composites for lithium-ion batteries, sodium-ion batteries, lithium-oxygen batteries, and supercapacitors are studied and summarized. Finally, the challenges and opportunities for future research on MOF-derived metal oxide composites are proposed on the basis of academic knowledge from the reported literature as well as from experimental experience.

Metal-Organic Framework-Derived Metal Oxide Embedded in Nitrogen-Doped Graphene Network for High-Performance Lithium-Ion Batteries.

Metal-organic frameworks (MOFs) are hybrid inorganic-organic materials that can be used as effective precursors to prepare various functional nanomaterials for energy-related applications. Nevertheless, most MOF-derived metal oxides exhibit low electrical conductivity and mechanical strain. These characteristics limit their electrochemical performance and hamper their practical application. Herein, we report a rational strategy for enhancing the lithium storage performance of MOF-derived metal oxide. The hierarchically porous Co3O4@NGN is successfully prepared by embedding ZIF-67-derived Co3O4 particles in a nitrogen-doped graphene network (NGN). The high electrical conductivity and porous structure of the NGN accelerates the diffusion of electrolyte ions and buffers stress resulting from the volume changes of Co3O4. As an anode material, the Co3O4@NGN shows high capacity (1030 mA h g-1 at 100 mA g-1), outstanding rate performance (681 mA h g-1 at 1000 mA g-1), and good cycling stability (676 mA h g-1 at 1000 mA g-1 after 400 cycles).

Fabrication of In2O3/Co3O4-palygorskite composites by the pyrolysis of In/Co-MOFs for efficient degradation of methylene blue and tetracycline

A facile method for fabrication of In2O3/Co3O4@palygorskite composites from a Co/In-based metal-organic framework (MOF) was reported. First, Co/In-MOFs hybridized with palygorskite (PAL) was prepared via a one-pot solvothermal method. Second, In2O3/Co3O4@PAL composites were obtained by pyrolysis of In2O3/Co3O4@PAL in air. It was found that the In2O3/Co3O4@PAL composite exhibited higher photocatalytic activities than In2O3/Co3O4 to the degradation of MB and TC under visible-light irradiation. About 99% of MB (within 40min) and 80% of TC (within 120min) were degraded using In2O3/Co3O4@5.0%PAL as catalyst. It was supposed that the efficient adsorption of MB and TC, and electrostatic interactions between electron–hole and PAL were responsible for such improvement. The photocatalytic degradation mechanisms of MB and TC on the In2O3/Co3O4@PAL were investigated. This work shows that hybridization MOFs with PAL could enhance the photocatalytic properties of MOFs-derived metal oxides for water treatment.