Copper-based metal-organic framework material as well as preparation method and application thereof

Abstract

The invention discloses a copper-based metal-organic framework material as well as a preparation method and application thereof, and relates to the field of copper-based metal-organic framework materials, 4 '-(2, 4-disulfophenyl)-4, 2': 6 ', 4' '-terpyridyl is taken as a ligand, a novel metal-organic framework material Cu-MOF with a three-dimensional structure is successfully synthesized, the material is crystallized in a tetragonal crystal system, and the crystal form of the material is shown in the description. And the space group is P43212. From the point of topology, the overall structure of the Cu-MOF material can be simplified into a Cu2S type topological structure with a point symbol {611. 84} {63} 2, the Cu-MOF material shows excellent electro-catalytic activity in a 0.1 M KOH electrolyte, the hydrogen evolution overpotential of the Cu-MOF material is only 158 mV, the Tafel slope of the Cu-MOF material is 102 mV dec-1, and meanwhile the Cu-MOF material shows good long-term stability. Therefore, the Cu-MOF has a wide application prospect in the field of electrocatalysis, and a new thought is provided for designing and developing an efficient and low-cost electrocatalyst.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of metal-organic framework materials, in particular to a copper-based metal-organic framework material and a preparation method and application thereof. BACKGROUND

[0002] With the continuous acceleration of the world industrialization process, fossil energy such as oil, coal and natural gas needed for human development is increasingly scarce. Energy crisis and environmental pollution problems are attracting more and more attention, and it is particularly urgent to develop renewable and green energy to replace fossil energy. Hydrogen is considered as an excellent energy carrier and one of the renewable alternative energy sources to meet future global energy demand due to its high energy density and non-polluting characteristics of combustion products. Among the many methods of hydrogen production, hydrogen production by electrochemical hydrogen evolution reaction (HER) is a frontier research field, which is a cleaner and more sustainable method compared with traditional steam methane reforming (SMR) and coal gasification (CG) hydrogen production strategies. At present, Pt is an excellent electrocatalyst for HER. However, the high cost of Pt catalyst limits its wide application. Therefore, researchers have been exploring alternative HER electrocatalysts with high energy efficiency, low overpotential and strong stability. In recent decades, some cheap non-noble metal-based electrocatalysts with high catalytic activity and strong stability have been reported, such as NiO x , CoS2, MoP, MoC and GO / Cu-MOF.

[0003] Metal-organic frameworks (MOFs) are crystalline materials or amorphous coordination compounds formed by coordination of organic ligands (usually multidentate or multilinker bridging ligands) with inorganic nodes (usually metal ions or metal clusters). These materials usually have high structural diversity and functional tunability, and usually have high specific surface area and porosity. This makes MOFs have great potential in the fields of fluorescent sensing, gas adsorption and separation, biological imaging, electrocatalysis, etc. In particular, a large number of metal atoms in MOF materials are exposed on the surface, which are very beneficial to electrocatalysis as unsaturated active catalytic sites. At the same time, the high synthesis tunability of MOFs provides great opportunities for the design and optimization of efficient electrocatalysts. So far, MOF-based electrocatalysts have shown good performance in many reactions such as hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR) and carbon dioxide reduction reaction (CO2RR). For HER, the application of original MOF materials formed by single metal nodes and ligand connection is the most easily understood in this field. However, factors such as relatively low electrical conductivity and poor stability hinder the application of original MOF materials in the field of HER. In order to improve this problem, a large number of studies have promoted the construction of MOF composite materials, such as Au / CoFe-MOFNs, Pd@MOF-74 and Ni-MOF@Pt. Although the HER activity of MOF composite materials has been significantly improved through great efforts, it is still a great challenge to improve the HER performance of pure MOF materials. SUMMARY

[0004] The present application aims to at least solve one of the technical problems existing in the prior art, and provide a copper-based metal-organic framework material and a preparation method and application thereof.

[0005] The technical solution of the present application is as follows:

[0006] A preparation method of a copper-based metal-organic framework material, the organic ligand 4'-(2,4-disulfophenyl)-4,2':6',4"-terpyridine, Cu(NO3)2·3H2O and N,N-dimethylformamide are mixed and heated in a stainless steel reactor with a polytetrafluoroethylene liner; then cooled to room temperature to obtain blue-purple block crystals.

[0007] Preferably, the molar ratio of the organic ligand 4'-(2,4-disulfophenyl)-4,2':6',4"-terpyridine, Cu(NO3)2·3H2O and N,N-dimethylformamide is 1:2:50.

[0008] Preferably, the cooling rate is 1.45-5℃ / h.

[0009] Preferably, the heating temperature is 80-100℃, and the heating time is 40-50h.

[0010] The application further discloses a copper-based metal-organic framework material prepared by the preparation method.

[0011] Preferably, the molecular formula is {Cu(HDSPTP)2·5H2O·0.8DMF}n, the crystal is in a tetragonal system, a space group is P43212, and an asymmetric unit is composed of one Cu(II) center and two HDSPTP - anions, and further comprises five uncoordinated water molecules and 0.8 free DMF molecules.

[0012] The application further discloses application of the copper-based metal-organic framework material in an electrocatalytic hydrogen evolution reaction.

[0013] Preferably, in a 0.1M KOH electrolyte, the Cu-MOF exhibits excellent electrocatalytic activity, a hydrogen evolution overpotential is 158mV, and a Tafel slope is 102mV dec -1 .

[0014] The application has the beneficial effects that the application provides a method for efficiently synthesizing compound 3 (Cu-MOF), successfully synthesizes a Cu-MOF (3) single crystal with a three-dimensional structure by selecting 4'(2,4-disulfophenyl)-4,2':6',4"-terpyridine (H2DSPTP) containing a high electron mobility pyridine unit as a ligand, and the molecular formula of the Cu-MOF (3) is {Cu(HDSPTP)2·5H2O·0.8DMF}n. 63 H 75 CuN 13 O 19 S4). The structure of the compound 3 is characterized by physical measurement methods such as single crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD), element analysis, Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). In addition, the application also studies the electrocatalytic hydrogen evolution performance of the Cu-MOF in different concentrations of KOH solution. The current density curve changing with time shows that the Cu-MOF has better long-term stability and electrocatalytic hydrogen production performance in a 0.1M KOH solution. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 are structure analysis of the compound 3, wherein (a) is a coordination environment of a copper atom in the compound 3, (b) is a three-dimensional framework structure diagram of the compound 3, and (c) is a simplified topological structure diagram of the compound 3;

[0016] Figure 2 are SEM and EDS analysis of the compound 3, wherein (a) and (b) are SEM images of the compound 3, and (c) is an energy spectrum mapping diagram of the compound 3;

[0017] Figure 3 EDS spectrum of compound 3;

[0018] Figure 4 Thermogravimetric analysis of Cu-MOF;

[0019] Figure 5 Infrared spectrum of Cu-MOF;

[0020] Figure 6 PXRD pattern of compound 3 simulation and experimental pattern of synthesis;

[0021] Figure 7 Energy spectrum analysis of compound 3, wherein (a): XPS full spectrum of compound 3; (b): C 1s spectrum; (c) O 1s spectrum; (d) Cu 2p spectrum;

[0022] Figure 8 Electrochemical performance analysis of compound 3 in the same concentration of alkaline solution, wherein (a): LSV curves of Cu-MOF / NF electrode and pure carbon / NF electrode in 0.1M KOH electrolyte; (b): Tafel curves of Cu-MOF / NF electrode and pure carbon / NF electrode in 0.1M KOH electrolyte; (c): By drawing the current density vs. scanning rate graph, the Cdl value of Cu-MOF / NF electrode and pure carbon / NF electrode was estimated; (d) EIS of Cu-MOF / NF electrode and pure carbon / NF electrode in 0.1M KOH electrolyte;

[0023] Figure 9 Cyclic voltammetry (CV) curves of Cu-MOF / NF electrode and pure carbon / NF electrode obtained at different scanning rates, wherein (a): CV curves of Cu-MOF / NF electrode in the potential range of-0.14~-0.05V vs. RHE; (b): CV curves of pure carbon / NF electrode in the potential range of-0.14~-0.05V vs. RHE;

[0024] Figure 10 Electrochemical performance of Cu-MOF in different concentrations of alkaline solution; wherein (a): LSV curves of Cu-MOF in different concentrations of KOH solution; (b): Tafel curves of Cu-MOF in different concentrations of KOH solution; (c): By drawing the current density vs. scanning rate graph, the Cdl value of Cu-MOF in different concentrations of KOH solution was estimated; (d): EIS of Cu-MOF in different concentrations of KOH solution;

[0025] Figure 11The CV curves of Cu-MOF in KOH solutions of different concentrations are shown below; (a): CV curve of Cu-MOF in 0.1M KOH solution; (b): CV curve of Cu-MOF in 0.2M KOH solution; (c): CV curve of Cu-MOF in 0.5M KOH solution; (d): CV curve of Cu-MOF in 1M KOH solution. Detailed Implementation

[0026] The embodiments of the present invention are described in detail below. These embodiments are exemplary and are only used to explain the present invention, and should not be construed as limiting the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0027] The technical solution of the present invention will be further illustrated by specific experiments below.

[0028] 1. Experimental reagents

[0029] The main experimental reagents used in this experiment are shown in Table 1.

[0030] Table 1. Reagents used in the experiment

[0031]

[0032]

[0033] 2. Experimental equipment

[0034] The main instruments and equipment used in the experiment are shown in Table 2 below.

[0035] Table 2 Equipment used in the experiment

[0036]

[0037] 3. Compound 3 (C 63 H 75 CuN 13 O 19 Synthesis of S4)

[0038] Organic ligand 4′-(2,4-disulfophenyl)-4,2′:6′,4″-terpyridine (H2DSPTP, 0.1 mmol, 46.9 mg), Cu(NO3)2·3H2O (0.1 mmol, 24.16 mg), and N,N-dimethylformamide (DMF, 3 mL) were mixed and sealed in a 20 mL PTFE-lined stainless steel reactor and heated in an oven at 100 °C for 48 hours. The mixture was then slowly cooled to room temperature at a rate of 1.45 °C / h to obtain blue-purple blocky crystals. The crystals were filtered and washed repeatedly with ethanol. The yield based on H2DSPTP was 69%. Elemental analysis showed that the calculated values ​​were: C 46.33%; N 8.27%; H 3.99%, and the measured values ​​were: C 46.15%; N 8.43%; H 3.68%.

[0039] 4. Preparation of the working electrode

[0040] Before conducting electrochemical tests, Cu-MOF catalyst ink needs to be prepared first. The specific steps are as follows: Weigh 4 mg of Cu-MOF sample and 4 mg of activated carbon, disperse them in 1 mL of DMF solution, and add 0.1 mL of 5 wt% Nafion solution as a binder. Place the mixture in an ultrasonic cleaner and sonicate for 30 minutes to ensure that the sample is fully dispersed and forms a uniform and stable suspension. Simultaneously, for comparative experiments, catalyst ink containing only activated carbon also needs to be prepared: Weigh 4 mg of activated carbon, disperse it in 1 mL of DMF solution, add 0.1 mL of 5 wt% Nafion solution, and sonicate for 30 minutes to form a uniform suspension.

[0041] Next, the two suspensions were uniformly dropped onto pre-cut nickel foam (NF, 4×5 mm) substrates using a drop-coating method. The drop volume was carefully controlled during the drop-coating process to ensure uniform coverage of the nickel foam surface. The substrates were then allowed to dry naturally at room temperature, ultimately producing Cu-MOF / NF and pure carbon / NF electrodes. These two electrodes will be used for subsequent electrochemical performance testing to evaluate the catalytic activity of the Cu-MOF material and its performance differences compared to pure carbon materials.

[0042] 5. Material Characterization

[0043] Powder X-ray diffraction measurements were performed using a D / Max-2500 X-ray diffractometer (XRD). Single-crystal diffraction intensity data for compound 3 were obtained using a graphite monochromatic Cu-Kα irradiator. Data were collected on an Oxford Supernova diffractometer, with the temperature cooled by a controller connected to the diffractometer. The structure was solved using a direct method, and an initial model for structural improvement was found using Olex2. All non-hydrogen atoms were identified from different Fourier plots and obtained using the SHELXL-2014 program via F... 2 The full-matrix least squares technique was improved. All non-hydrogen atoms were anisotropically refined, and hydrogen atoms were placed in ideal positions and located in the Fourier transform infrared spectrum. CCDC(2324778) contains supplemental crystallographic data for compound 3, which are freely available from the Cambridge Data Centre for Crystallography at www.ccdc.cam.ac.uk / datarequest / cif.

[0044] The morphological characteristics of the compounds were recorded using a scanning electron microscope (SEM, Zeiss Sigma 300) operating at 10.0 kV. The elemental composition and chemical states of the compound surface were determined using X-ray photoelectron spectroscopy (XPS) with a monochromatic X-ray source (Al Kα, 15 kV, 200 W). Measurements were recorded on a KBr disk from 400 to 4000 cm⁻¹ using a Bruker Tensor 27 spectrometer. -1 FT-IR spectra within the range. Thermogravimetric analysis (TGA) was performed using a Hitachi STA200 simultaneous thermal analyzer under nitrogen atmosphere, with heating from room temperature to 800°C at a heating rate of 20°C / min.

[0045] 6. Electrochemical Measurement

[0046] Electrochemical tests were performed using a Shanghai Chenhua CHI660C electrochemical workstation. All tests were conducted at room temperature using a standard three-electrode system. In this system, the working electrode was a catalyst-supported nickel foam (NF, 4×5 mm), the counter electrode was a platinum sheet electrode, and the reference electrode was a saturated Ag / AgCl electrode. To comprehensively evaluate the catalyst performance, electrocatalytic tests were performed on two working electrodes: when using a pure carbon / NF electrode as the working electrode, the tests were conducted in 0.1 M KOH solution to examine the electrocatalytic behavior of the pure carbon material; when using a Cu-MOF / NF electrode as the working electrode, to study the effect of different electrolyte concentrations on catalytic performance, the tests were conducted in 0.1 M KOH solution, 0.2 M KOH solution, 0.5 M KOH solution, and 1 M KOH solution, respectively. This multi-concentration test design helps to more comprehensively analyze the electrocatalytic activity and stability of Cu-MOF materials in different environments. The measured potential was converted to a potential relative to the reversible hydrogen electrode (RHE) using the Nernst equation, and the conversion formula is:

[0047] E RHE =E Ag / AgCl +0.197 +0.059 pH#(3-1) 7. Conclusion

[0048] (1) Structural analysis of compound 3

[0049] A solvothermal reaction of Cu(NO3)2·3H2O and H2DSPTP in DMF solution at 100 °C was carried out. After 48 hours of heating and slow cooling, compound 3 crystals were successfully generated. The crystal structure of compound 3 was determined by single-crystal X-ray diffraction analysis. The results showed that compound 3 crystallizes in a tetragonal crystal system with space group P43212 (specific data are shown in Table 3). The asymmetric unit consists of one Cu(II) center and two HDSPTPs. - The anionic composition was further confirmed by elemental analysis to include five uncoordinated water molecules and 0.8 free DMF molecules, which may fill the voids in the crystal structure. In the structure of compound 3, all Cu(II) centers are in a distorted octahedral coordination environment. Each Cu(II) ion is surrounded by two molecules from different HDSPTPs. - The O atom of the anion and four from different HDSPTP - N atom coordination of the anion-terminal pyridine unit ( Figure 1 (a)). The Cu-N bond length is The Cu-O bond length is These bond length data indicate that stable coordinate bonds are formed between the Cu(II) ion and the ligand. Notably, the two N atoms on the terminal pyridine group are coordinated to two different Cu(II) ions, while SO3... 2- The group is coordinated with a Cu(II) ion via an O atom, a coordination mode that provides the basis for structural expansion. Within the three-dimensional framework, each Cu(II) ion is connected via six HDSPTPs. - Ligand linkage, and each HDSPTP - The ligands are then linked to three Cu(II) ions. This highly interconnected coordination mode enables all HDSPTPs to... - The ligands and Cu(II) ions are interconnected through Cu-O and Cu-N bonds, and extend and expand along the a direction based on the bc plane, ultimately forming a complex three-dimensional framework structure. Figure 1 (b)). To more clearly describe this complex three-dimensional framework, a topological analysis approach was employed, and calculations were performed using the free computer program TOPOS. In the topological analysis, each Cu(II) ion was treated as a six-connection node, and each HDSPTP -Anions are considered as three-connected nodes. Through simplified analysis, the entire structure can be classified as a Cu₂S-type topology, with dot notation {6}. 11 ·8 4}{6 3}2( Figure 1 (c)).

[0050] Table 3 Crystallographic data of the compounds

[0051]

[0052]

[0053] Note: a R1=Σ||F o |-|F c || / |F o |, b wR2=[Σw(F o 2 -F c 2 ) 2 / Σw(F o 2 ) 2 ] 1 / 2 ,where w=1 / [σ 2 (F o 2 )+(aP)2+bP].P=(F o 2 +2F c 2 ) / 3.CCDC number for compound 3:2324778.

[0054] (2) SEM and EDS analysis

[0055] Scanning electron microscopy (SEM) images clearly demonstrate the morphological and structural features of compound 3. From Figure 2As shown in (ab), compound 3 exhibits a highly regular octahedral blocky crystal structure. This regular geometric shape reflects the high degree of orderliness in the molecular arrangement during crystal growth. Generally, the chemical structure of a substance directly or indirectly determines its physical properties, such as crystal morphology, surface characteristics, and mechanical properties. In crystallography, the surface morphology of a substance is often influenced by a combination of various intermolecular interactions, including covalent bonds, coordinate bonds, and hydrogen bonds. These interactions not only determine the internal structure of the crystal but also significantly affect its external morphology. Furthermore, there is a close relationship between the length of chemical bonds and bond energy: in most cases, the longer the bond length between atoms, the weaker the bond energy, and the lower the energy required to break the bond. The surface of compound 3 exhibits a unique microscopic drought-crack-like structure, a phenomenon similar to that of SO3. 2- The long Cu-O bonds between the functional groups and Cu(II) ions are closely related. These long Cu-O bonds lead to reduced stability of the local structure, resulting in this crack-like feature on the surface.

[0056] To further characterize the chemical composition of compound 3, an energy dispersive spectroscopy mapping diagram was used in the study. Figure 2 (c) and energy-dispersive X-ray spectroscopy (EDS) Figure 3 Analysis was performed. EDS and energy-dispersive X-ray spectroscopy (EDS) mapping results confirmed the presence of C, O, S, Cu, and N elements in compound 3, with signals from SEM analysis. Furthermore, EDS quantitatively analyzed the weight and atomic percentages of the major elements in the Cu-MOF, and the obtained data showed high agreement with theoretical calculations (Table 4). These experimental results not only verified the chemical composition of compound 3 but also further supported the rationality of its crystal structure. Combining the results of SEM morphology analysis, EDS elemental analysis, and elemental distribution maps, the microstructural characteristics and formation mechanism of compound 3 were comprehensively revealed.

[0057] Table 4 shows the weight percentage and atomic percentage of each element in Cu-MOF obtained by EDS analysis.

[0058]

[0059] (3) Thermogravimetric analysis (TGA)

[0060] Thermogravimetric analysis (TGA) was performed on Cu-MOF under a nitrogen atmosphere, heating it from room temperature to 800℃ at a heating rate of 20℃ / min. The analytical curves are shown below. Figure 4As shown, when the temperature rises to 100°C, the first weight loss is approximately 7.4% (theoretical calculation value is 7.7%), attributed to the removal of 5 free water molecules. When the temperature rises to 200°C, this stage represents a second weight loss of 4.8% (theoretical calculation value is 5%), attributed to the removal of 0.8 free DMF molecules. Upon further heating, the framework begins to decompose.

[0061] (4) Infrared analysis (IR)

[0062] The infrared spectrum of Cu-MOF was measured at room temperature, such as... Figure 5 As shown. For Cu-MOF, at 3434 cm⁻¹ -1 The characteristic peak at 3071 cm⁻¹ can be attributed to the absorption peak of water molecules and hydrogen bond association, while the peak at 3071 cm⁻¹ is... -1 and 1189cm -1 The strong absorption peaks near 548 cm⁻¹ are the result of the stretching vibrations of the OH and S=O bonds in the sulfonic acid group. -1 The distinct peak at 612 cm⁻¹ corresponds to the stretching vibration of the N-Cu bond, while the peak at 612 cm⁻¹ corresponds to the stretching vibration of the N-Cu bond. -1 The peak at that point corresponds to the stretching vibration of the O-Cu bond.

[0063] (5) Powder X-ray diffraction (PXRD) analysis

[0064] The powder X-ray diffraction (PXRD) pattern of compound 3 obtained by comparison experiment was compared with the theoretical simulation pattern. Figure 6 The researchers found a high degree of agreement between the two diffraction peak positions. This result indicates that the synthesized material is consistent with the computational model in terms of long-range order, and the target compound was successfully obtained. The theoretical simulation spectrum is based on single-crystal structure analysis, assuming that the crystal has ideal periodicity and a defect-free structure. Therefore, the comparison between experimental and simulation data can effectively verify the crystallinity, structural stability, and potential defects or impurities of the product. Experimental XRD data show that the diffraction peaks of compound 3 are basically consistent with the simulation peaks, further confirming that its spatial configuration is consistent with the theoretical model and that the crystal has good order.

[0065] (6) X-ray photoelectron spectroscopy (XPS) analysis

[0066] The elemental composition and surface valence states of the composite material were analyzed by X-ray photoelectron spectroscopy (XPS), with charge correction performed using the electron binding energy of C1s at 284.8 eV. XPS results for compound 3 ( Figure 7 (a) shows that characteristic peaks of C1s, O1s, and Cu 2p are present in the sample. The C1s spectral fitting results ( Figure 7 (b) indicates that the peaks at 284.5 eV and 285.9 eV correspond to C-C and CN bonds, respectively. In the O 1s spectrum ( Figure 7(c) The peak at 531.3 eV is attributed to SO bonds, while the peak at 533.7 eV is related to surface-adsorbed oxygen. In the Cu 2p spectrum ( Figure 7 (d) The peaks at 933.1 eV and 953.1 eV are attributed to Cu 2p, respectively. 3 / 2 and Cu 2p 1 / 2 This indicates that Cu mainly exists as Cu 2+ It exists in form.

[0067] (7) Electrochemical performance analysis of Cu-MOF in alkaline solutions of the same concentration

[0068] This study employed a standard three-electrode electrochemical testing system to systematically evaluate the hydrogen evolution reaction (HER) catalytic performance of Cu-MOF catalyst and activated carbon control sample at room temperature. During the experiment, an Ag / AgCl electrode was used as the reference electrode, a platinum sheet as the counter electrode, and a nickel foam electrode loaded with catalytic material as the working electrode. Linear sweep voltammetry (LSV) was used in 0.1 M KOH electrolyte, with a scan rate set at 10 mV / s. -1 By comparing the current density responses of the two catalysts at different overpotentials, the intrinsic catalytic activity of Cu-MOF materials can be accurately evaluated. Figure 8 As shown in (a), by comparing the HER polarization curves of Cu-MOF / NF electrodes and pure carbon / NF electrodes in 0.1 M KOH electrolyte, it can be clearly observed that Cu-MOF materials significantly improve catalytic performance. Specifically, the Cu-MOF / NF electrode achieves a higher HER polarization performance at 10 mA cm⁻¹. -2 The overpotential required at the specified current density is only 158 mV, significantly lower than that of the pure carbon / NF electrode under the same conditions (450 mV), indicating that the Cu-MOF material possesses superior catalytic activity. Furthermore, comparing the onset potentials, the positive onset potential of the Cu-MOF / NF electrode is 171 mV, nearly 50% lower than the 340 mV of the pure carbon / NF electrode, further confirming the advantage of Cu-MOF materials in lowering the reaction energy barrier. This superior catalytic performance may be attributed to the unique porous structure of Cu-MOF materials, which provides abundant active sites, and its good conductivity, which promotes rapid electron transfer. Figure 8 The LSV curve data shown in (a) was further used to plot the corresponding Tafel curve. Figure 8 (b) to further analyze the HER reaction kinetics mechanism. Generally, the electrochemical HER mechanism in alkaline media can be considered as a combination of the following basic steps: (I) Volmer reaction: H₂O + e⁻ - →H ads +OH - (120mV dec -1(II) Heyrovsky reaction: H ads +H2O+e - →H2+OH - (40mV dec -1 ), representing the electrochemical desorption of hydrogen; (III) Tafel reaction: 2H ads →H2(30mV dec -1 ), representing the chemical desorption of hydrogen. Wherein, H... ads This represents hydrogen atoms adsorbed at the active sites of the electrocatalyst. The Tafel slope of the Cu-MOF / NF electrode in 0.1M KOH solution was calculated to be 102 mV dec. -1 This value is significantly lower than the Tafel slope (231 mV dec) of the pure carbon / NF electrode under the same conditions. -1 This result indicates that the Cu-MOF electrocatalyst HER reaction mainly follows the Volmer-Heyrovsky mechanism. The relatively low overpotential and small Tafel slope of the Cu-MOF / NF electrode suggest that it has excellent electrocatalytic activity and more favorable kinetic characteristics in the HER process.

[0069] Figure 9 (ab) shows Cu-MOF / NF electrodes and pure carbon / NF electrodes at different scan rates (10-50 mV s). -1 Cyclic voltammetry (CV) curves were obtained. To quantitatively assess the number of active sites on the catalyst, we calculated the electrochemical surface area (ECSA) using cyclic voltammetry, a key parameter for evaluating the intrinsic activity of electrocatalysts. ECSA is determined based on the direct proportionality between the electric double-layer capacitance (Cdl) and the electrochemical surface area. Figure 8 As shown in (c), the CV curves of the non-Radida potential range were measured at different scan rates, and the charging current (Δj=j) was plotted. a -j c The linear relationship between the Cdl value and the scan rate allows for accurate calculation of the Cdl value. Experimental results show that the Cdl value of the Cu-MOF electrocatalyst is significantly higher than that of the pure carbon control sample, indicating that the Cu-MOF material has a larger electrochemical surface area, thus exposing more active sites. This structural feature is beneficial to the adsorption and transformation of reactant molecules and is one of the important reasons why Cu-MOF exhibits excellent HER performance. In addition, electrochemical impedance spectroscopy (EIS) was introduced to study the interfacial reactions and electrode kinetics of Cu-MOF in HER. Figure 8(d) The charge transfer resistance (Rct) of the Cu-MOF electrocatalyst in 0.1M KOH solution is much smaller than that of the pure carbon electrocatalyst, indicating that Cu-MOF exhibits efficient electron transfer and better HER kinetics at the electrocatalyst / electrolyte interface.

[0070] (8) Comparison of electrochemical performance of Cu-MOF in alkaline solutions of different concentrations

[0071] The HER catalytic performance of Cu-MOF was investigated in KOH solutions of different concentrations. Experiments were conducted using a three-electrode electrochemical cell, and linear sweep voltammetry was used in 0.1 M, 0.2 M, 0.5 M, and 1 M KOH solutions at a scan rate of 10 mV / s. -1 ( Figure 10 (a)). The results show that the HER overpotential of Cu-MOF increases with increasing KOH concentration. Specifically, in 0.1M KOH solution, the HER overpotential of Cu-MOF is 158 mV (10 mA cm⁻¹). -2 The overpotential of Cu-MOF in 0.2 M KOH solution was significantly higher than that in 0.5 M and 1 M KOH solutions, where it was 250 mV. In 0.5 M and 1 M KOH solutions, the overpotential increased to 284 mV and 334 mV, respectively. Furthermore, the positive onset potential of Cu-MOF in 0.1 M KOH solution was 171 mV, while the onset potential increased significantly in higher concentrations of KOH solution. The smaller overpotential and onset potential indicate that Cu-MOF exhibits superior HER catalytic activity in 0.1 M KOH solution. To further analyze the HER reaction kinetics of Cu-MOF in different concentrations of KOH solution, the corresponding Tafel curves were plotted. Figure 10 (b)). The results show that the Cu-MOF electrocatalyst exhibits the smallest Tafel slope (102 mV dec) in 0.1 M KOH solution. -1 In higher concentrations of KOH solution, the Tafel slope gradually increases. The smaller Tafel slope indicates that Cu-MOF has superior electrocatalytic activity and more favorable reaction kinetics in 0.1M KOH solution, further verifying its high-efficiency HER performance in low-concentration KOH solution.

[0072] Table 5. HER electrochemical parameters of Cu-MOF / NF electrode and pure carbon / NF electrode in KOH solution.

[0073]

[0074] By performing scans at different rates (10-50 mV s) within the non-Radida potential range -1 CV scans were performed to obtain the CV curves of Cu-MOF in KOH solutions of different concentrations. Figure 11(ad)), and plot the charging current (Δj=j a -j c A linear relationship graph between the scan rate and the Cdl value was used to accurately calculate the Cdl value. Figure 10 (c) Experimental results show that Cu-MOF obtained the highest Cdl value in 0.1M KOH solution, indicating that Cu-MOF has higher intrinsic activity in lower concentration alkaline solutions. Table 5 lists the electrochemical parameters of HER of Cu-MOF / NF electrode and pure carbon / NF electrode in KOH solution. EIS was introduced to study the interfacial reaction and electrode kinetics of Cu-MOF HER in KOH solutions of different concentrations. Figure 10 (d) The Rct values ​​of Cu-MOF in several KOH solutions of different concentrations were compared. It exhibited the lowest charge transfer resistance in 0.1 M KOH solution, indicating the fastest charge transfer kinetics at this concentration. Furthermore, to investigate the electrocatalytic stability of Cu-MOF, its it curve analysis showed only slight disturbances and very limited degradation after 24 hours in alkaline medium. Figure 10 (e)). Table 6 compares the electrocatalytic performance of pure MOF-based HER electrocatalysts in this invention and other literature. The results show that compound 3 reported in this work exhibits excellent electrocatalytic hydrogen production activity and good stability without any modification, similar to the results of classical inorganic electrocatalysts.

[0075] Table 6 compares the results of this work with those of other pure MOF-based HER electrocatalysts reported in the literature.

[0076]

[0077]

[0078] In summary, this invention successfully synthesized a novel metal-organic framework material Cu-MOF(3) with a three-dimensional structure using 4′-(2,4-disulfophenyl)-4,2′:6′,4″-terpyridine as a ligand, and systematically studied its crystal structure, topological characteristics, and electrocatalytic performance. Single-crystal X-ray diffraction analysis showed that the material crystallizes in a tetragonal crystal system with space group P43212. From a topological perspective, its overall structure can be simplified to a structure with the dot symbol {6}. 11 ·8 4}{6 3The Cu₂S-type topology of Cu₂O₅ provides an important theoretical basis for the functional design of materials. Furthermore, this invention focuses on the performance of Cu-MOF in the electrocatalytic hydrogen evolution reaction. Experimental results show that in 0.1 M KOH electrolyte, Cu-MOF exhibits excellent electrocatalytic activity, with a hydrogen evolution overpotential of only 158 mV and a Tafel slope of 102 mV. -1 Furthermore, it exhibits excellent long-term stability. These superior properties demonstrate that Cu-MOFs have broad application prospects in the field of electrocatalysis, providing new ideas for the design and development of efficient and low-cost electrocatalysts. This invention not only expands the application scope of coordination polymer materials in electrocatalysis but also provides important experimental evidence and theoretical guidance for the design and construction of novel crystalline MOF materials with high electrocatalytic activity, which is of great significance for promoting the development of clean energy technologies.

[0079] The embodiments described above are merely preferred embodiments of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various other corresponding changes and modifications based on the technical solutions and concepts described above, and all such changes and modifications should fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a copper-based metal-organic framework material, characterized in that, The organic ligand 4′-(2,4-disulfophenyl)-4,2′:6′,4″-terpyridine, Cu(NO3)2·3H2O and N,N-dimethylformamide were mixed and sealed in a stainless steel reactor lined with polytetrafluoroethylene and heated; then cooled to room temperature to obtain blue-purple blocky crystals.

2. The method for preparing a copper-based metal-organic framework material according to claim 1, characterized in that, The molar ratio of the organic ligand 4′-(2,4-disulfophenyl)-4,2′:6′,4″-terpyridine, Cu(NO3)2·3H2O and N,N-dimethylformamide is 1:

2.

3. The preparation method and application of a copper-based metal-organic framework material according to claim 1, characterized in that, The cooling rate is 1.45-5℃ / h.

4. The method for preparing a copper-based metal-organic framework material according to claim 1, characterized in that, The heating temperature is 80-100℃, and the holding time is 40-50h.

5. A copper-based metal-organic framework material, characterized in that, It is prepared by any one of the preparation methods described in claims 1-4.

6. A copper-based metal-organic framework material according to claim 5, characterized in that, The molecular formula is {Cu(HDSPTP)2·5H2O·0.8DMF}n. It crystallizes in the tetragonal crystal system with space group P43212. The asymmetric unit consists of one Cu(II) center and two HDSPTPs. - It is composed of anions and also contains five uncoordinated water molecules and 0.8 free DMF molecules.

7. The application of a copper-based metal-organic framework material according to claim 5 or 6 in the electrocatalytic hydrogen evolution reaction.

8. The application according to claim 7, characterized in that, In 0.1 M KOH electrolyte, Cu-MOF exhibited excellent electrocatalytic activity, with a hydrogen evolution overpotential of 158 mV and a Tafel slope of 102 mV dec. -1 .

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