KR102375865B1 - Metal organic frameworks comprising nikel, and Preparation method thereof, Electrode and Energy storage device comprising the same - Google Patents

Abstract

The present invention is a metal-organic framework grown on a support, containing nickel, prepared using a surfactant, containing nickel sulfide, and characterized in that a carbon shell is formed on the surface, a metal-organic framework It relates to a framework and a method for manufacturing the same, to a metal-organic framework electrode and an energy storage device including the same. The metal-organic framework according to the present invention can exhibit the effect of not only improving electrical conductivity and specific electric capacity, but also maintaining stability even after long-time charge-discharge.

Description

A metal-organic framework comprising nickel, a method for manufacturing the same, and an electrode and an energy storage device including the same

The present invention relates to a metal-organic framework containing nickel, a method for manufacturing the same, an electrode including the same, and an energy storage device having high capacity and high output.

Due to accelerating global warming and depletion of energy resources, the need for energy storage devices is increasing. Among various energy storage devices, supercapacitors are being actively studied for various reasons such as fast charge-discharge characteristics, higher energy density than conventional capacitors and higher power density than batteries, lower maintenance cost, and wide operating temperature range.

Supercapacitors are largely divided into electric double-layer capacitors and pseudo-capacitors. The pseudo-capacitor has the advantage of having relatively higher specific capacitance and energy density than the electric double-layer capacitor. Transition metal oxides, conductive polymers, etc. have been frequently reported as materials constituting these materials, but recently, studies using metal-organic frameworks are attracting attention.

A metal-organic framework (MOF) is a framework structure in which a metal and an organic linkage (or organic ligand) are organically and regularly connected, and has a large specific surface area, porosity, and easy control of pore size.

On the other hand, nickel, one of the transition metals, has a high theoretical capacitance (capacitance, or electric capacity) of 3000 F/g or more, and has excellent electrochemical properties enough to be used as secondary batteries such as nickel-cadmium batteries. . Accordingly, many researchers are actively conducting research on metal-organic frameworks based on this.

However, the currently developed nickel-based metal-organic framework does not provide sufficient electrical conductivity and is unstable during charging and discharging for a long time, so there is still a limit to its use as an electrode material for similar capacitors.

Therefore, in order to solve the above problem, there is a need for research on a nickel-based metal-organic framework that is stable even after charging and discharging for a long time while improving electrical conductivity.

It is an object of the present invention to provide a metal-organic framework capable of improving electrical conductivity and specific electric capacity of a metal-organic framework and maintaining stability even during long-time charge-discharge, and a method for manufacturing the same, and a metal-organic framework comprising the same To provide a sieve electrode and an energy storage device.

The present invention is

A metal-organic framework comprising nickel, grown on a support, comprising:

It is prepared using a surfactant,

Provided is a metal-organic framework comprising nickel sulfide, characterized in that a carbon shell is formed on the surface.

In addition, the present invention provides a first step of preparing a metal-organic framework by hydrothermal reaction of an aqueous solution containing a nickel precursor, an organic ligand precursor, and a surfactant and a support; and a second step of sulfiding calcining the prepared metal-organic framework in an inert gas atmosphere at a temperature of 250° C. to 500° C. for 0.5 to 3 hours.

The metal-organic framework according to the present invention includes nickel sulfide and carbon shell through a manufacturing method that uses a surfactant and undergoes a high-temperature sulfide firing process, thereby improving electrical conductivity and specific electric capacity as well as long-term charge-discharge Even so, stability can be maintained.

In addition, the metal-organic framework according to the present invention can be grown in-situ on a support, avoiding the use of conductive materials or binders to reduce costs, simplify the process, and reduce the resistance of the binder. performance degradation can be prevented.

1 is a schematic view showing a process for preparing a metal-organic framework according to the present invention (FIG. 1 (a) and (c)) and a metal-organic framework prepared according to Comparative Examples 1 and 1 and 2 It is an electrode photograph (FIG. 1 (b)) including.
2 and 3 are images taken by FE-SEM of the metal-organic frameworks prepared according to Comparative Example 1 and Examples 1 and 2;
4 is an image taken by HR-TEM of the metal-organic frameworks prepared according to Comparative Example 1 and Examples 1 and 2;
5 is a result of FT-IR analysis of the metal-organic frameworks prepared according to Comparative Example 1 and Examples 1 and 2;
6 is a result of X-ray photoelectron spectroscopy (XPS) analysis of the metal-organic frameworks prepared according to Comparative Example 1 and Examples 1 and 2;
7 is a result of measuring the electrochemical properties of the metal-organic frameworks prepared according to Comparative Example 1 and Examples 1 and 2;

Since the present invention can have various changes and can have various embodiments, specific embodiments are illustrated in the drawings and will be described in detail in the detailed description.

However, this is not intended to limit the present invention to specific embodiments, and it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention.

In a first aspect of the present invention, the present invention is a metal-organic framework including nickel grown on a support, prepared using a surfactant, containing nickel sulfide, and having a carbon shell formed on the surface characterized, to a metal-organic framework.

The "metal-organic framework" referred to in the present invention refers to a structure in which an organic ligand is covalently and coordinately bonded to a metal, and pores of a predetermined size are formed.

The nickel sulfide may be formed by substituting sulfur for carbon of an organic ligand included in the metal-organic framework through a sulfide calcination reaction when manufacturing the metal-organic framework of the present invention.

The organic ligand may be used without limitation as long as it is an organic ligand commonly used in this field, and specifically, terephthalic acid, trimesic acid (1,3,5-Benzenetricarboxylic acid), 2-methylimidazole, Dabco (1 ,4-diazabicyclo[2.2.2]-octane, DABCO) or hexamethylenetetraamine (HMT).

The support may be nickel foam, cobalt foam, copper foam, carbon cloth, or carbon fiber paper, and specifically may be nickel foam, but is not limited thereto.

The metal-organic framework according to the present invention can be directly grown on a support through an in-situ method.

The carbon shell may be amorphous, and may be generated by an organic ligand included in the metal-organic framework. As an example, in the preparation of the metal-organic framework according to the present invention, in the process of forming nickel sulfide through the sulfide calcination process, carbon in the organic ligand of the metal-organic framework forms a shell of the metal-organic framework. It may be formed on the surface.

This carbon shell not only overcomes the disadvantages of the metal-organic framework with low electrical conductivity, but also suppresses the swelling effect that occurs during long-time charge-discharge, thereby improving electrode stability.

The metal-organic framework of the present invention can be prepared using a surfactant. For example, in the process of preparing the metal-organic framework, a surfactant may be mixed with the precursors of the metal-organic framework and then dissolved in a solvent, or the precursors may be first dissolved in the solvent and then added continuously. .The surfactant may be at least one selected from the group consisting of urea, polyvinyl alcohol, polyvinylpyrrolidone, and pluronic P123.

The surfactant may lead to a morphological change by influencing the nucleation and growth process during the formation of the metal-organic framework, without changing the reaction mechanism of the metal-organic framework, thus improving capacitance, long-term It can exhibit effects such as maintaining stability even during charge-discharge.

As an example of the present invention, the thickness of the metal-organic framework of the present invention may be 600 nm to 700 nm. In that the metal-organic framework without using a surfactant has a thickness of 200 to 400 nm, the thickness is increased by the surfactant added during the manufacturing process.

As an example of the present invention, the metal-organic framework may have a structure in which nanosheets are formed in multiple layers, and specifically, may have a lamellar structure in which nanosheets are formed in multiple layers. By having the above structure, the metal-organic framework may have a large surface area.

In a second aspect of the present invention, the present invention provides a first step of preparing a metal-organic framework by hydrothermal reaction of an aqueous solution containing a nickel precursor, an organic ligand precursor, and a surfactant with a support; and a second step of sulfiding calcining the prepared metal-organic framework at a temperature of 250° C. to 500° C. for 0.5 to 3 hours in an inert gas atmosphere.

The nickel precursor may be nickel nitrate hydrate, nickel chloride hydrate, or nickel acetic acid, for example, nickel nitrate hydrate, but is not limited thereto.

The organic ligand precursor is terephthalic acid, trimesic acid (1,3,5-Benzenetricarboxylic acid), 2-methylimidazole, Dabco (1,4-diazabicyclo[2.2.2]-octane, DABCO) or hexamethylenetetra It may be an amine (HMT), specifically terephthalic acid, but is not limited thereto.

The surfactant may be urea, polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), or pluronic P123, specifically urea or polyvinyl alcohol, but is limited thereto. it is not going to be

A solvent may be used to dissolve the nickel precursor, the organic ligand precursor and the surfactant in the first step, the solvent being dimethylformamide (DMF), isopropyl alcohol, methanol, ethanol, butanol, acetonitrile, methylene chloride, chloro It may be any one selected from the group consisting of foam, toluene, benzene, acetone, tetrahydrofuran (THF), distilled water, and combinations thereof, but is not limited thereto.

As an example of the first step, after dissolving the metal precursor and the organic ligand precursor in a solvent, a surfactant may be further added, dissolved and stirred, and then the prepared solution and the support may be hydrothermally reacted.

In the first step, by additionally adding a surfactant in addition to the nickel precursor and organic ligand, the metal-organic framework nucleation and the rate of growth process are controlled, or through effects such as inducing or inhibiting growth in a specific crystal plane direction, metal- The organic framework may exhibit various forms. That is, a change in the size of the metal-organic framework, a change in the surface area, or a change in the pore size may occur, which may promote charge transfer, which is very important for supercapacitor operation, improve the penetration and accessibility of electrolyte ions, It can have a positive effect, such as reducing internal resistance.

The hydrothermal reaction of the first step may be performed by heating at a temperature of 100° C. to 180° C. for 18 hours or more. Specifically, the hydrothermal reaction may be performed by heating at a temperature of 100°C to 180°C, 100°C to 150°C, or 110°C to 140°C for 18 hours to 30 hours, 20 hours to 28 hours, or 20 hours to 26 hours. can

The metal-organic framework prepared through the hydrothermal reaction of the first step may exhibit a layered structure in which nanosheets are stacked.

The method for producing a metal-organic framework according to the present invention further comprises a second step of sulfidation firing for 0.5 to 3 hours at a temperature of 250°C to 500°C in an inert gas atmosphere after preparing the metal-organic framework. .

Specifically, the sulfiding calcination step is performed in a nitrogen or argon atmosphere at a temperature of 250°C to 450°C, 250°C to 400°C, 300°C to 380°C for 0.5 hours to 3 hours, 0.5 hours to 2 hours, or 0.5 hours to 1.5 hours. It can be carried out by calcining for a period of time, for example, it can be carried out by calcining at a temperature of 350 ℃ in nitrogen or argon atmosphere for 1 hour.

The second step of calcining sulfide may be calcined by adding phosphorus or selenium to sulfur in an inert gas atmosphere, but is not limited thereto.

As the second step of sulfidation calcination, the present invention is that carbon of an organic ligand included in the metal-organic framework may be substituted with sulfur to form nickel sulfide, and a carbon shell may be formed on the surface of the metal-organic framework. there is.

The present invention can reduce costs by simplifying the electrode manufacturing process by an in-situ method of directly growing a metal-organic framework on a support through the first step and the second step, and the conductive material and By avoiding the use of a binder, performance degradation due to the resistance of the binder can be prevented, and electrical conductivity can be improved by inducing smoother electron transfer due to the close contact between the electrode material and the support.

In addition, the present invention provides a metal-organic framework electrode including the above-described metal-organic framework and a support, and provides an energy storage device including such an electrode.

Specifically, the energy storage device may be a hydrogen production and storage fuel cell, a lithium ion cell, a solar cell, or a supercapacitor. More specifically, the energy storage device may be a supercapacitor.

As an example, the energy storage device according to the present invention may include the above-described metal-organic framework electrode and a counter electrode. For example, the counter electrode may be Pt/C or activated carbon. In this case, the counter electrode may be formed on the same support as the support used for the metal-organic framework electrode, or may be compressed under a certain pressure.

Specifically, an electrolyte may be included between the metal-organic framework electrode and the counter electrode. More specifically, the electrolyte may include a potassium hydroxide-based electrolyte. For example, it may serve to bond the metal-organic framework electrode and the counter electrode.

Hereinafter, the present invention will be described in more detail by way of Examples and the like according to the present invention, but the scope of the present invention is not limited by the Examples presented below.

Example

Example 1

Preparation Example 1 - Synthesis of nickel-based metal-organic framework (Ni-MOF)

To synthesize a nickel-based metal-organic framework (Ni-MOF), 0.72 g of nickel nitrate hexahydrate (Nickel(II) nitrate hexahydrate) and 0.42 g of terephthalic acid were mixed with distilled water and dimethylformamide. It was uniformly dissolved in 60 ml of a solvent (distilled water: dimethylformamide (volume ratio) = 1: 2). At this time, (c) 0.132 g of urea as a surfactant was added, and stirred so as to be uniformly dissolved together with the solution.

The well-dissolved solution and (d) nickel foam as an electrode material support were transferred to a Teflon autoclave and hydrothermal reaction was performed at 130° C. for 24 hours. In order to remove the residue from the Ni-MOF grown on the nickel foam, it was washed several times with ethanol and dried in a vacuum oven at 50° C. to prepare a metal-organic framework.

Preparation Example 2 - High-temperature sulfurization (calcination)

The metal-organic framework prepared in Preparation Example 1 was calcined at 350° C. for 1 hour together with (a) sulfur powder in a tube furnace in an inert gas atmosphere (nitrogen or argon). At this time, the rate of temperature increase was 5 °C. After the reaction was completed, it was naturally cooled to room temperature.

Example 2

In Preparation Example 1 (c), a metal-organic framework was prepared in the same manner as in Example 1 except that 0.132 g of polyvinyl alcohol (PVA) was used as a surfactant.

Comparative Example 1

A metal-organic framework was prepared in the same manner as in Example 1 except for the step of (c) adding a surfactant in Preparation Example 1.

Experimental Example 1 - Confirmation of the shape of the prepared electrode

2 is a Field Emission Scanning Electron Microscope (FE-SEM) image of the metal-organic framework before high-temperature sulfur calcination treatment. Specifically, FIGS. 2 (a) and (b) are FE-SEM images of Comparative Example 1 before high temperature sulfur calcination treatment, (c) and (d) are FE-SEM images of Example 1 before high temperature sulfur calcination treatment, (e) and (f) are FE-SEM images of Example 2 before high temperature sulfur calcination treatment.

As can be seen in FIG. 2, through the hydrothermal reaction of high temperature and high pressure, Comparative Example 1 showed a layered structure in which nanosheets were stacked ((a) and (b) of FIG. 2), and Example 1 was a comparative example The thickness was increased than 1 ((c) and (d) of Fig. 2), and Example 2 formed a lamellar structure ((e) and (f) of Fig. 2).

This is because, according to Preparation Example 1, the surfactant added during the formation of the metal-organic framework interacts with the nucleation and growth process to form different shapes depending on the type of the added surfactant.

Specifically, the element of Example 1 increased the thickness of the metal-organic framework due to the self-recognition behavior of the functional group interacting with other surfactants to tightly bind the organic ligand. The polyvinyl alcohol of Example 2 can form a PVA-Ni ²⁺ complex through chelation with Ni ²⁺ ions, which acts as a structure-directing agent to form a gap between the nanosheets to form a lamellar structure can be derived.

3 shows FE-SEM images of the metal-organic frameworks of Comparative Examples 1, 1 and 2 after high-temperature sulfur calcination treatment. Specifically, FIGS. 3 (a) and (b) are FE-SEM images of Comparative Example 1, FIGS. 3 (c) and (d) are FE-SEM images of Example 1, and FIG. 3 (e) and (f) are FE-SEM images of Example 2.

As can be seen in FIG. 3 , each metal-organic framework maintained its original shape without significant structural deformation even after the high-temperature sintering process at 350°C.

4 is a high-resolution transmission electron microscope (HR-TEM) image of the metal-organic frameworks of Comparative Examples 1, 1 and 2 after high-temperature sulfur calcination according to Preparation Example 2; Specifically, FIGS. 4(a) and (b) are HR-TEM images of Comparative Example 1, FIGS. 4(c) and (d) are HR-TEM images of Example 1, FIG. 4(e) and (f) are HR-TEM images of Example 2.

As can be seen in FIG. 4 , in Comparative Examples 1 and 1 and 2, the surface of the metal-organic framework was maintained while maintaining a clearly crystalline form inside the metal-organic framework (red arrow portion in FIG. 4). An amorphous carbon shell was formed.

5 is a Fourier-transform infrared spectroscopy (FT-IR) spectra of Comparative Examples 1, 1, and 2; As shown in FIG. 5 , the same results were obtained at the same positions as in Comparative Example 1, Examples 1 and 2 without any shift between peaks. From this, in Examples 1 and 2, the metal-organic framework was well synthesized through the hydrothermal reaction, and Urea and PVA added as surfactants in Examples 1 and 2 did not change the self-forming mechanism of the metal-organic framework. , it can be seen that only the morphology of the metal-organic framework was changed.

Experimental Example 2 -Measurement of chemical state and electrochemical performance of metal-organic framework

The chemical states of the metal-organic frameworks of Comparative Examples 1, 1 and 2 were investigated by measuring X-ray photoelectron spectroscopy (XPS) of Comparative Examples 1, 1 and 2, The results are shown in FIG. 6 and Table 1.

As can be seen from the XPS of FIG. 6(a), in all of the metal-organic frameworks of Comparative Examples 1, 1 and 2, nickel (Ni), oxygen (O), carbon (C), sulfur (S) elements were found.

Figure 6(b) is an oxidation-reduction reaction (redox reaction) as XPS for Ni 2p, a main element, peaks corresponding to Ni 2p _1/2 and Ni 2p _3/2 were found at 873.4 eV and 855.9 eV, respectively. . In addition, as a result of deconvolution, Ni 2p is composed of Ni ³⁺ (855.9 eV) and Ni ²⁺ (853.1 eV), and in both the metal-organic frameworks of Comparative Examples 1, 1 and 2, All of the area ratios were the same at 1:1. Through this, it could be confirmed once again that no additional oxidation-reduction reaction occurred due to the surfactants of Examples 1 and 2, and only the form of the metal-organic framework was changed.

Figure 6(c) is XPS for O 1s, typical metal-oxygen bond (529.7 eV), metal carbonate state (531.2 eV), organic carbon-oxygen (CO) bond (532.6 eV), etc. This was discovered.

Figure 6(d) is XPS for S 2p, S 2p _3/2 and S 2p _1/2 peaks at 161.5 eV and 162.6 eV, respectively, are deconvolutionally divided and divided, and sulfur is Ni through high-temperature sulfur treatment. It was confirmed that -MOF was well maintained in a divalent cation state.

Figure 6(e) is XPS for N 1s, the general chemical state of nitrogen, metal nitride of 397 eV, C-NH ₂ bond of 400 eV, and a value within resolution without peaks such as nitride of 405 eV This was measured. Through this, it can be seen that nitrogen is not present in the metal-organic frameworks of Comparative Examples 1, 1 and 2, and it is noteworthy that nitrogen was not found in the MOF of Example 1, in which nitrogen-containing urea was added. be worth.

6(f) is XPS for C 1s. Peaks corresponding to OC = O (288.5 eV), COC (286 eV), and CC (284.8 eV) bonds were found, so that the organic ligands of Ni-MOF are well connected to each other. It has been confirmed that

In addition, XPS element ratio % (atomic ratio%) is summarized in Table 1 below. Considering that the oxidation-reduction reaction of the pseudo-capacitor mostly occurs on the electrode surface, it can be expected that the electrochemical reaction of Example 1, in which the element ratio of Ni is the highest, is the fastest.

element percentage element Comparative Example 1 Example 1 Example 2 S 2p 7.49 6.31 6.02 C 1s 46.54 40.92 53.38 N 1s 0.86 0.84 0.21 O 1s 30.51 34.64 29.11 Ni 2p 14.6 17.29 11.27 100 100 99.99

In Experimental Example 2, following the material analysis, electrochemical measurements were performed for device analysis as a supercapacitor.

Figure 7 (a) is a CV graph of Comparative Examples 1, 1 and 2 at 50 mV / s, Figure 7 (b) is the CV of Example 1 at 5-100 mV / s, Figure 7 (c) is a GCD graph of Comparative Example 1, Examples 1 and 2 at 5 A/g, (d) of FIG. 7 is a GCD graph of Example 1 at 1-10 A/g, FIG. 7(e) ) is a graph of the cycle stability test result of Example 2.

7(a) shows that when cyclic voltammetry (CV) was measured at the same scan rate of 50 mV/s, clear oxidation-reduction peaks were observed in Comparative Examples 1, 1, and 2, indicating characteristics of similar capacitors. , and it can be seen that Example 2 has the largest area and thus the highest specific capacitance.

In Equation 1, ∫I dv is the area of the CV graph, v is the scan rate, m is the weight of the active material, and V is the voltage range (potential window).

As a result of calculating the specific capacitance through Equation 1, Comparative Examples 1, 1, and 2 showed 188.8, 206.2, and 394.2 F/g at 50 mV/s, respectively.

7(b) shows the results of measuring CV in Example 2 at various scan rates of 5-100 mV/s. Through this, it was confirmed that oxidation-reduction of the electrode material of the present invention was well maintained even at a high scan rate.

When calculated through Equation 1, Example 2 is 3193.3, 1730.0, 940.4, 394.0, respectively at scan rates of 5 mV/s, 10 mV/s, 20 mV/s, 50 mV/s, and 100 mV/s It showed a specific capacitance of 211.9 F/g.

7( c ) shows the results of galvanostatic charge-discharge (GCD) in which charge-discharge is repeated at the same current density of 5 A/g. As in Fig. 7(a) , it can be expected that the discharge time of Example 2 is the longest at the same current density, so it has the highest specific electric capacity.

In Equation (2), I is a current density, t is a discharging time, m is an active material weight, and V is a voltage range (potential window). As a result of calculating the specific capacitance through Equation (2), Comparative Examples 1, 1, and 2 yielded 806.0, 872.0, and 1926.0 F/g at 5 A/g, respectively. 7(d) is a result of GCD measurement of Example 2 at various current densities of 2-10 A/g. Through this, it was confirmed that oxidation-reduction was well maintained even at high current density in the electrode material of the present invention. When calculated through Equation 2, Example 2 is 2780.0, 2184.0, 2036.0, 1926.0 at current densities of 2 A/g, 3 A/g, 4 A/g, 5 A/g, and 10 A/g, respectively, It showed excellent specific electric capacity of 987.0 F/g.

On the other hand, in evaluating the performance of the electrode, not only the specific capacitance but also the long-term operation is an important factor.

In order to evaluate the long-term repeated stability test of the electrode in which Example 2, which showed the best performance among Comparative Examples 1, 1 and 2, was grown, the GCD cycle was repeated at a constant current density of 50 A/g, The results are shown in FIG. 7(e). The electrode grown in Example 2 maintained 88% performance compared to the first cycle even when 15,000 cycles were repeated.

As such, it can be confirmed that the electrode using Example 2 not only has a high specific capacitance, but can also be operated for a long time.

Claims (13)

A metal-organic framework comprising nickel, grown on a support, comprising:
It is prepared using a surfactant,
A metal-organic framework comprising nickel sulfide, characterized in that a carbon shell is formed on the surface through a sulfide calcination process. The method of claim 1,
wherein the support is nickel foam, cobalt foam, copper foam, carbon cloth or carbon fiber paper. The method of claim 1,
The surfactant is at least one metal-organic framework selected from the group consisting of urea, polyvinyl alcohol, polyvinylpyrrolidone, and pluronic P123. The method of claim 1,
The metal-organic framework is a metal-organic framework having a lamellar structure in which sheets are formed in multiple layers. The method of claim 1,
wherein the carbon shell is generated by an organic ligand included in the metal-organic framework. A first step of preparing a metal-organic framework grown on the support by hydrothermal reaction of an aqueous solution containing a nickel precursor, an organic ligand precursor, and a surfactant and a support; and
A method for producing a metal-organic framework, comprising a second step of sulfiding calcining the prepared metal-organic framework in an inert gas atmosphere at a temperature of 250°C to 500°C for 0.5 to 3 hours. 7. The method of claim 6,
The first step of preparing the metal-organic framework is a method for producing a metal-organic framework, characterized in that the hydrothermal reaction is performed at a temperature of 100°C to 180°C for 18 to 30 hours. 7. The method of claim 6,
In the first step of preparing the metal-organic framework, the organic ligand precursor is terephthalic acid, trimesic acid, 2-methylimidazole, dabco (1,4-diazabicyclo[2.2.2]-octane, DABCO) and hexa A method for producing at least one metal-organic framework selected from the group consisting of methylenetetraamine. 7. The method of claim 6,
In the first step of preparing the metal-organic framework, the surfactant is at least one selected from the group consisting of urea, polyvinyl alcohol, polyvinylpyrrolidone, and pluronic P123. Method for producing a metal-organic framework. 7. The method of claim 6,
A method for producing a metal-organic framework, comprising forming a carbon shell and nickel sulfide on the metal-organic framework as a second step of sulfidation firing. 7. The method of claim 6,
The second step of sulfide calcination is a method for producing a metal-organic framework, characterized in that the calcination is carried out by additionally adding phosphorus or selenium. A metal-organic framework electrode comprising the metal-organic framework according to claim 1 and a support. An energy storage device comprising the metal-organic framework electrode according to claim 12 .

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