2-x-terephthalic acid copper-based MOFs (Metal-Organic Frameworks) micro-nano sheet as well as preparation method and application thereof

Abstract

The invention discloses a 2-x-terephthalic acid copper-based MOFs (Metal-Organic Frameworks) micro-nano sheet and a preparation method and application thereof, and the method comprises the following steps: dropwise adding a copper chloride dihydrate solution into a pre-deprotonated 2-x-terephthalic acid solution, stirring to react, and centrifugally washing and drying the product to obtain the 2-x-terephthalic acid copper-based MOFs micro-nano sheet, x is one of methyl, amino or hydroxyl. The 2-x-terephthalic acid copper-based MOFs micro-nano sheet can be used for electrocatalytic reduction of carbon dioxide. The 2-x-terephthalic acid copper-based MOFs micro-nano sheet prepared by the invention has a unique folded sheet structure, the specific surface area and the exposure degree of active sites of the material are remarkably increased, and mass transfer and charge transfer paths are shortened, so that the kinetics and energy efficiency of a catalytic reaction are integrally optimized.

Description

Technical Field

[0001] This invention relates to the field of CO2 reduction catalyst synthesis technology, specifically to a 2-x-terephthalic acid copper-based MOF micro / nanosheet, its preparation method, and its application. Background Technology

[0002] Developing efficient copper-based metal-organic framework (MOF) electrocatalysts for carbon dioxide reduction requires not only green synthesis methods with mild reaction conditions and controllable morphology, but also precise control over the electronic structure of the materials to guide product selectivity. However, the synthesis of most existing copper-based MOFs relies on high-temperature, high-pressure solvothermal methods. This method is not only energy-intensive and complex, but also makes it difficult to precisely control the microstructure and surface structure of the materials. As a result, the prepared materials are mostly three-dimensional bulk materials with low specific surface area, poor accessibility of active sites, and high mass transfer resistance, which seriously restricts their practical application in electrocatalytic reactions.

[0003] Currently, achieving the controllable construction of two-dimensional or open structures of copper-based MOFs under mild and environmentally friendly conditions still faces significant challenges. Conventional methods often require the introduction of organic solvents, structure-directing agents, or harsh reaction conditions, resulting in complex processes with low environmental compatibility, making it difficult to achieve a balance between structural controllability and synthetic sustainability. Furthermore, effectively suppressing the stacking, aggregation, or transformation to a stable bulk phase of high surface energy nanosheets during synthesis and post-processing, while maintaining their open and highly active surface properties, is also a major challenge in current preparation. Existing strategies often rely on surfactants or complex post-processing, which can easily introduce impurities or disrupt structural integrity, making it difficult to simultaneously achieve activity and stability.

[0004] On the other hand, having achieved controllable morphology, how to further systematically regulate the electronic structure of materials to precisely influence their interaction with CO2 and its intermediates, thereby guiding specific reaction pathways and product distribution, remains a challenge, lacking clear and scalable material design strategies. Most current research focuses on single-ligand or mixed-ligand systems, lacking precise electronic control of ligand substituents to accurately influence key intermediates (such as CO2 and its intermediates). * The adsorption behavior of CO can effectively guide the CO2 reduction pathway. Therefore, developing a synthetic strategy for a series of copper-based MOF materials with well-defined structures, stable morphologies, and tunable electronic structures under mild and green conditions is not only of significant methodological importance, but also provides a key material basis for a deeper understanding of the catalytic mechanism and selective regulation of CO2RR (carbon dioxide reduction reaction). Summary of the Invention

[0005] The purpose of this invention is to provide 2-x-terephthalic acid copper-based MOFs micro / nanosheets, their preparation method, and applications, which can be used for the electrocatalytic reduction of CO2 to prepare alkanes (C64- ...x H y ) or C2 + The product and material are simple to prepare, inexpensive, and have broad application prospects.

[0006] In one aspect of the present invention, a method for preparing 2-x-tetraphthalate copper-based MOFs micro / nanosheets is provided. According to an embodiment of the present invention, the method includes the following steps: adding a copper chloride dihydrate solution dropwise to a pre-deprotonated 2-x-tetraphthalic acid solution, stirring the reaction, centrifuging, washing, and drying the product to obtain 2-x-tetraphthalate copper-based MOFs micro / nanosheets, wherein x is one of methyl, amino, or hydroxyl groups.

[0007] This invention achieves synergistic regulation of the electronic structure and reaction microenvironment of the copper active center by precisely introducing different functional groups onto the benzene ring ligand, thereby directionally guiding the product selectivity of CO2 reduction. The amino group, as a strong electron donor, can increase the electron density of the copper active center and adjust its d-band center position, thus effectively regulating... * The adsorption behavior and subsequent transformation pathways of key intermediates such as CO can influence their choice of different pathways, such as CC coupling or further hydrogenation. Methyl groups possess both induced electronic effects and hydrophobic steric effects; their electron-donating ability can mildly modulate the charge distribution at copper sites, while their hydrophobic microenvironment can regulate the local concentration and mass transfer process of reactants at the active interface. Hydroxyl groups, through their electronic effects and hydrogen bonding interactions, can further fine-tune the electronic state of the copper center and stabilize specific reaction intermediates, providing a multi-dimensional structure-electronic synergistic mechanism for the precise control of product selectivity.

[0008] In addition, the method for preparing 2-x-terephthalic acid copper-based MOFs micro / nanosheets according to the above embodiments of the present invention may also have the following additional technical features:

[0009] In some embodiments of the present invention, the concentration of the copper chloride dihydrate solution is 0.02~0.2 mol / L; the concentration of the pre-deprotonated 2-x-terephthalic acid solution is 0.01~0.06 mol / L; the volume ratio of the copper chloride dihydrate solution to the pre-deprotonated 2-x-terephthalic acid solution is 1:(2~3); the stirring reaction is carried out at room temperature for 1~6 h; the centrifugation washing is performed using deionized water, and the number of centrifugation washings is 2~3; the drying temperature is 60~80 ℃, and the drying time is 6~12 h.

[0010] In some embodiments of the present invention, the pre-deprotonated 2-x-terephthalic acid solution is obtained by dissolving the 2-x-terephthalic acid ligand in a deionized aqueous solution of sodium hydroxide, wherein the concentration ratio of the sodium hydroxide solution to the concentration of the 2-x-terephthalic acid ligand is 2:1.

[0011] This invention uses copper chloride dihydrate as the metal source and 2-x-terephthalic acid as the organic linker, and dissociates the ligand carboxyl group (-COOH) into a carboxylate group (-COO) by pre-deprotonation. - This can significantly enhance its solubility in aqueous solutions and improve its coordination activity with copper ions.

[0012] In another aspect of the present invention, the present invention provides a method for preparing 2-x-tetraphthalate copper-based MOFs micro / nanosheets.

[0013] In addition, the 2-x-terephthalic acid copper-based MOFs micro / nanosheets according to the above embodiments of the present invention may also have the following additional technical features:

[0014] In some embodiments of the present invention, when x is methyl, the size of the 2-x-terephthalic acid copper-based MOFs micro / nanosheets is 0.3~3 µm, exhibiting a distinct macroporous and wrinkled sheet-like structure. The ligand carboxyl group is pre-deprotonated to a carboxylate group, significantly enhancing its coordination ability with copper ions and driving rapid and uniform two-dimensional nucleation and in-plane spreading. Simultaneously, the methyl group, as a hydrophobic group, can regulate the local microenvironment at the growth interface through its steric hindrance and hydrophobic effect. On the one hand, it moderately delays the stacking along the c-axis, inducing sheet separation and wrinkling; on the other hand, it promotes the orderly arrangement of ligands at the interface through hydrophobic interactions, thereby facilitating the formation of an open porous structure. Thus, the material can self-assemble under mild aqueous conditions, ultimately forming a nanosheet structure with abundant wrinkles and porous morphology.

[0015] In some embodiments of the present invention, when x is an amino group, the size of the 2-x-terephthalic acid copper-based MOFs micro / nanosheets is 0.3~3 µm, exhibiting a continuous, wrinkled sheet-like structure. Amino groups possess strong hydrophilicity and coordination directing properties, allowing them to adsorb water molecules and regulate the local growth microenvironment through hydrogen bonding or weak coordination during growth, guiding the sheets to undergo controllable undulations and folds during extension. Thus, the material self-assembles under mild aqueous conditions to form a thin nanosheet morphology with an open surface and continuous wrinkles.

[0016] In some embodiments of the present invention, when x is a hydroxyl group, the 2-x-terephthalic acid copper-based MOFs micro / nanosheets have a size of 0.5–5 µm and exhibit a wrinkled, continuous sheet-like structure. Pre-deprotonation treatment converts the ligand carboxyl groups into carboxylate groups, significantly enhancing their coordination reactivity with copper ions and promoting rapid and uniform two-dimensional nucleation and in-plane growth. Simultaneously, the inherent hydroxyl groups on the ligands form hydrogen bonds with a large number of water molecules in an aqueous environment, inducing local bending and folding of the sheets during crystal growth. To further reduce surface energy, the sheets continuously undergo gentle bending and wrinkling during expansion, ultimately forming a thin nanosheet structure with open, continuous wrinkles.

[0017] In another aspect of the invention, an application of 2-x-copper terephthalate-based MOFs micro / nanosheets is proposed. According to an embodiment of the invention, the 2-x-copper terephthalate-based MOFs micro / nanosheets are used in the electrocatalytic reduction of carbon dioxide.

[0018] Catalyzed by 2-x-copper terephthalate-based MOFs micro / nanosheets, carbon dioxide molecules can undergo carbon-oxygen bond activation under the drive of external energy, binding protons (H+). + ) and electrons (e - It is gradually reduced and eventually converted into alkanes or C2 hydrocarbons. + Carbon-based products that have fuel or chemical value.

[0019] In another aspect of the present invention, a method for preparing a flow cell cathode is proposed. According to an embodiment of the present invention, the method includes the following steps: dispersing the 2-x-copper terephthalate-based MOFs micro / nanosheets in a mixed solution of ethanol and water, ultrasonically dispersing them to form a suspension, then adding a binder to prepare a catalyst slurry, spraying the catalyst slurry onto carbon paper, and drying the catalyst-loaded carbon paper, which is the flow cell cathode.

[0020] In addition, the method for preparing a flow cell cathode according to the above embodiments of the present invention may also have the following additional technical features:

[0021] In some embodiments of the present invention, the volume ratio of ethanol to water is (4~9):1; the mass ratio of the 2-x-terephthalic acid copper-based MOFs micro / nanosheets to the mixed solution of ethanol and water is 1:(1000~3000); the ultrasonic dispersion time is 10~30 min; the binder is a naphthol binder; and the loading of the catalyst slurry on the carbon paper is 0.25~0.75 mg cm⁻¹. -2 The drying temperature is 60~80 ℃, and the drying time is 0.5~2 h.

[0022] In another aspect of the invention, a flow cell is proposed. According to an embodiment of the invention, the cathode of the flow cell is used as the cathode. Specifically, a 0.5~1.5 mol / L potassium hydroxide solution is used as the electrolyte, a fumasep membrane (formaldehyde anion exchange membrane) is used as the ion exchange membrane, a platinum sheet electrode is used as the anode, and an Ag / AgCl electrode is used as the reference electrode.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] 1) This invention successfully achieved the controllable preparation of a series of copper-based MOF micro / nanosheets under pure aqueous conditions by pre-deprotonating 2-x-terephthalic acid (x = methyl, amino, hydroxyl) ligands. This method is mild, simple, requires no organic solvents, and exhibits good reproducibility and scalability potential.

[0025] 2) The series of 2-x-terephthalic acid copper-based MOFs micro / nanosheets prepared in this invention possess continuous, open, and high-specific-surface-area wrinkled morphologies, which not only significantly improve the exposure and accessibility of active sites but also optimize mass transfer and electron transport pathways, thereby enhancing the overall electrocatalytic reaction kinetics of the material. In the electrocatalytic CO2 reduction, the highest partial current densities for ethylene (C2H4) and methane (CH4) reached -239.2 mA cm⁻¹, respectively. -2 and -276 mA cm -2 .

[0026] 3) This invention achieves synergistic regulation of the electronic structure of the copper active center and the reaction microenvironment by precisely introducing different functional groups (amino group with strong electron donation, methyl group with mild electron donation, and hydroxyl group with synergistic hydrogen bonding) onto the benzene ring ligand, thereby directionally guiding the product selectivity of CO2 reduction.

[0027] 4) The 2-x-copper terephthalate-based MOFs micro / nanosheets prepared in this invention exhibit excellent performance and tunable product selectivity. Specifically, 2-methyl-copper terephthalate-based MOFs and 2-amino-copper terephthalate-based MOFs show good performance against C2... + The highest selectivity of the products exceeds 61%; the selectivity of 2-hydroxy-terephthalic acid copper-based MOFs for alkane products reaches 60.8%, of which the CH4 efficiency is 42.5%.

[0028] 5) By pre-deprotonating ligands with different substituents (methyl, amino, hydroxyl), this invention can effectively drive rapid two-dimensional nucleation and in-plane growth. At the same time, different substituents can regulate the local microenvironment at the growth interface through their inherent electronic and spatial effects, inducing controllable wrinkles in the sheets, which can effectively suppress the stacking and aggregation of nanosheets and form a continuous open wrinkled micro / nanosheet structure. Attached Figure Description

[0029] Figure 1 FESEM (Field Emission Scanning Electron Microscope) images of 2-methyl-terephthalic acid copper-based MOFs micro / nanosheets prepared in Example 1 of this invention, wherein Figure a is a low-magnification FESEM image and Figure b is a high-magnification FESEM image;

[0030] Figure 2 These are TEM (transmission electron microscope) images of the 2-methyl-terephthalic acid copper-based MOFs micro / nanosheets prepared in Example 1 of this invention, wherein Figure a is a low-magnification TEM image and Figure b is a high-magnification TEM image.

[0031] Figure 3 Figure 1 shows FESEM images of the 2-amino-terephthalic acid copper-based MOFs micro / nanosheets prepared in Example 2 of this invention. Figure 2a is a low-magnification FESEM image, and Figure 2b is a high-magnification FESEM image.

[0032] Figure 4 The images shown are TEM images of the 2-amino-terephthalic acid copper-based MOFs micro / nanosheets prepared in Example 2 of this invention, where Figures a and b are TEM images of different positions.

[0033] Figure 5 This is a FESEM image of the 2-hydroxy-terephthalic acid copper-based MOFs micro / nanosheets prepared in Example 3 of this invention.

[0034] Figure a is a low-magnification FESEM image, and Figure b is a high-magnification FESEM image.

[0035] Figure 6 These are TEM images of the 2-hydroxy-terephthalic acid copper-based MOFs micro / nanosheets prepared in Example 3 of the present invention, wherein Figure a is a low-magnification TEM image and Figure b is a high-magnification TEM image.

[0036] Figure 7 The XRD (X-ray diffraction analysis) patterns of the 2-x-copper terephthalate-based MOFs micro / nanosheets and copper terephthalate-based MOFs prepared in Examples 1-3 of this invention are shown.

[0037] Figure 8 This is a Faraday efficiency diagram of the electrocatalytic CO2 reduction products of the 2-methyl-terephthalic acid copper-based MOFs micro / nanosheets under different constant current conditions in Application Example 1 of this invention;

[0038] Figure 9 This is a Faraday efficiency diagram of the electrocatalytic CO2 reduction products of 2-amino-terephthalic acid copper-based MOFs micro / nanosheets under different constant current conditions in Application Example 2 of this invention;

[0039] Figure 10This is a Faraday efficiency diagram of the electrocatalytic CO2 reduction products of the 2-hydroxy-terephthalic acid copper-based MOFs micro / nanosheets under different constant current conditions in Application Example 3 of this invention; Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0041] Example 1

[0042] A method for preparing 2-methyl-copper terephthalate-based MOFs micro / nanosheets includes the following steps:

[0043] (1) Dissolve 85.2 mg of copper chloride dihydrate in 15 mL of deionized water and sonicate for 15 min to form solution A;

[0044] (2) Dissolve 40 mg NaOH in 35 mL of deionized water to form solution B, and sonicate for 5 min; dissolve 90.1 mg 2-methyl-terephthalic acid in solution B, and sonicate for 20 min to form solution C;

[0045] (3) Solution C was slowly added dropwise to solution A, and the reaction was stirred at room temperature for 2 h. After centrifugation and washing three times with deionized water, the product was dried at 60 °C for 8 h to obtain 2-methyl-terephthalic acid copper-based MOFs micro / nanosheet powder.

[0046] like Figures 1-2 As shown, the 2-methyl-terephthalic acid copper-based MOFs micro / nanosheets have a size of 0.3–3 µm. This material exhibits rich wrinkled morphology and macroporous structure. Through its open two-dimensional micro / nanosheet structure, it achieves high-activity site exposure while significantly optimizing mass transfer pathways and the accessibility of active sites.

[0047] Example 2

[0048] A method for preparing 2-amino-terephthalic acid copper-based MOFs micro / nanosheets includes the following steps:

[0049] (1) Dissolve 85.24 mg of copper chloride dihydrate in 15 mL of deionized water and sonicate for 15 min to form solution A;

[0050] (2) Dissolve 40 mg NaOH in 35 mL of deionized water to form solution B, dissolve 90.6 mg 2-amino-terephthalic acid in solution B, and sonicate for 20 min to form solution C;

[0051] (3) Solution C was slowly added dropwise to solution A, and the reaction was stirred at room temperature for 2 h. After centrifugation and washing three times with deionized water, the product was dried at 60 ℃ for 8 h to obtain 2-amino-terephthalic acid copper-based MOFs micro / nanosheet powder.

[0052] like Figures 3-4 As shown, the 2-amino-terephthalic acid copper-based MOFs micro / nanosheets have a size of 0.3–3 µm and exhibit a wrinkled, sheet-like structure. This open two-dimensional wrinkled morphology of the thin micro / nanosheets endows the material with a high specific surface area and ample accessibility to active sites, significantly improving mass transfer efficiency and reaction interface activity.

[0053] Example 3

[0054] A method for preparing 2-hydroxy-copper terephthalate-based MOFs micro / nanosheets includes the following steps:

[0055] (1) Dissolve 85.24 mg of copper chloride dihydrate in 15 mL of deionized water and sonicate for 15 min to form solution A;

[0056] (2) Dissolve 40 mg NaOH in 35 mL of deionized water to form solution B, dissolve 91.1 mg 2-hydroxy-terephthalic acid in solution B, and sonicate for 20 min to form solution C;

[0057] (3) Solution C was slowly added dropwise to solution A, and the reaction was stirred at room temperature for 2 h. After centrifugation and washing three times with deionized water, the mixture was dried at 60 ℃ for 8 h to obtain 2-hydroxy-terephthalic acid copper-based MOFs micro / nanosheet powder.

[0058] like Figures 5-6 As shown, the 2-hydroxy-terephthalic acid copper-based MOFs micro / nanosheets have a size of 0.5–3 µm and a continuously open, wrinkled, sheet-like structure. This morphology effectively improves the specific surface area and accessibility of active sites, promoting mass transfer and electron transport processes.

[0059] Figure 7The XRD diffraction patterns of the 2-x-copper terephthalate-based MOFs (x = methyl, amino, and hydroxyl) micro / nanosheets and copper terephthalate-based MOFs prepared in Examples 1-3 are shown in the figures. As can be seen from the figures, the 2-x-copper terephthalate-based MOFs micro / nanosheets all maintained similar main diffraction peaks as the copper terephthalate-based MOFs, indicating that their basic framework structure was preserved. Meanwhile, the introduction of functional groups caused local shifts in the diffraction peaks, with some samples showing new peaks at specific angles or significant changes in the intensity of existing diffraction peaks, reflecting the differentiated regulatory effects of different substituents on the interlayer spacing, symmetry, and order of the crystals. These structural changes further confirm that the introduction of ligand groups can effectively regulate the crystal structure and microenvironment of MOF materials.

[0060] Application Example 1

[0061] A method for preparing a flow cell includes the following steps:

[0062] (1) Weigh 20 mg of the 2-methyl-terephthalic acid copper-based MOFs micro / nanosheet powder prepared in Example 1, disperse it in 10 mL of a mixed solution of ethanol and water (volume ratio of ethanol to water is 4:1), add 60 μL of D520 perfluorosulfonic acid solution (naphthol binder), and sonicate for 20 min to completely disperse the catalyst powder in the mixed solution to prepare a catalyst slurry.

[0063] (2) The catalyst slurry was drop-sprayed onto 2 cm × 4 cm carbon paper with a loading of 0.5 mg / cm². -2 The carbon paper loaded with the catalyst after drying is then placed in a vacuum drying oven at 70°C and dried for 1 hour. This dried carbon paper is the cathode of the flow cell.

[0064] (3) The carbon paper loaded with the catalyst after drying is used as the cathode of the flow cell, the platinum sheet electrode is used as the anode, the Ag / AgCl electrode is used as the reference electrode, the 1.0 mol / L potassium hydroxide solution is used as the electrolyte, and the fumasep membrane is used as the ion exchange membrane.

[0065] -100 to -700 mA cm -2 Electrocatalytic performance was tested within a constant current range. The main products of its electrocatalysis of carbon dioxide were ethylene and ethanol.

[0066] like Figure 8 As shown, 2-methyl-copper terephthalate-based MOFs micro / nanosheets catalyze the conversion of CO2 to C2. + The selectivity of the products can reach up to 61.4%, with the highest partial current density of C2H4 reaching -239.2 mA cm⁻¹. -2 .

[0067] Application Example 2

[0068] A method for preparing a flow cell includes the following steps:

[0069] (1) Weigh 20 mg of the 2-amino-terephthalic acid copper-based MOFs micro / nanosheet powder prepared in Example 2, disperse it in 10 mL of a mixed solution of ethanol and water (volume ratio of ethanol to water is 4:1), add 60 μL of 5% D520 perfluorosulfonic acid solution, and sonicate for 20 min to completely disperse the catalyst powder in the mixed solution to prepare a catalyst slurry.

[0070] (2) The catalyst slurry was drop-sprayed onto 2 cm × 4 cm carbon paper with a loading of 0.5 mg / cm². -2 The carbon paper loaded with the catalyst after drying is then placed in a vacuum drying oven at 70°C and dried for 1 hour. This dried carbon paper is the cathode of the flow cell.

[0071] (3) The carbon paper loaded with the catalyst after drying is used as the cathode of the flow cell, the platinum sheet electrode is used as the anode, the Ag / AgCl electrode is used as the reference electrode, the 1.0 mol / L potassium hydroxide solution is used as the electrolyte, and the fumasep membrane is used as the ion exchange membrane.

[0072] -100 to -650 mA cm -2 Electrocatalytic performance was tested within a constant current range. The main products of its electrocatalysis of carbon dioxide were ethylene and ethanol.

[0073] like Figure 9 As shown, 2-amino-terephthalic acid copper-based MOFs micro / nanosheet powder catalyzes the conversion of CO2 to C2. + The selectivity can reach up to 61.4%, with C2H4 exhibiting the highest partial current density of -176.5 mA cm⁻¹. -2 .

[0074] Application Example 3

[0075] A method for preparing a flow cell includes the following steps:

[0076] (1) Weigh 20 mg of the 2-hydroxy-terephthalic acid copper-based MOFs micro / nanosheet powder prepared in Example 3, disperse it in 10 mL of a mixed solution of ethanol and water (volume ratio of ethanol to water is 4:1), add 60 μL of 5% D520 perfluorosulfonic acid solution, and sonicate for 20 min to completely disperse the catalyst powder in the mixed solution to prepare a catalyst slurry.

[0077] (2) The catalyst slurry was drop-sprayed onto 2 cm × 4 cm carbon paper with a loading of 0.5 mg / cm². -2 The carbon paper loaded with the catalyst after drying is then placed in a vacuum drying oven at 70°C and dried for 1 hour. This dried carbon paper is the cathode of the flow cell.

[0078] (3) The carbon paper loaded with the catalyst after drying is used as the cathode of the flow cell, the platinum sheet electrode is used as the anode, the Ag / AgCl electrode is used as the reference electrode, the 1.0 mol / L potassium hydroxide solution is used as the electrolyte, and the fumasep membrane is used as the ion exchange membrane.

[0079] -100 to -650 mA cm -2 Electrocatalytic performance was tested within a constant current range. The main products of its electrocatalysis of carbon dioxide were ethylene and ethanol.

[0080] like Figure 10 As shown, the selectivity of 2-hydroxy-terephthalic acid copper-based MOFs micro / nanosheet powder for catalytic conversion of CO2 to alkanes can reach up to 60.8%, with the highest partial current density of CH4 reaching -276 mA cm⁻¹. -2 .

[0081] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the scope defined by the present invention, and all such modifications and additions should fall within the protection scope of the present invention.

Claims

1. A method for preparing 2-x-copper terephthalate-based MOFs micro / nanosheets, characterized in that, Includes the following steps: A copper chloride dihydrate solution was added dropwise to a pre-deprotonated 2-x-terephthalic acid solution, and the reaction was stirred. The product was then centrifuged, washed, and dried to obtain 2-x-terephthalic acid copper-based MOFs micro / nanosheets, wherein x is one of methyl, amino, or hydroxyl groups.

2. The method for preparing 2-x-terephthalic acid copper-based MOFs micro / nanosheets according to claim 1, characterized in that: The concentration of the copper chloride dihydrate solution is 0.02~0.2 mol / L; The concentration of the pre-deprotonated 2-x-terephthalic acid solution is 0.01~0.06 mol / L; The volume ratio of the copper chloride dihydrate solution to the pre-deprotonated 2-x-terephthalic acid solution is 1:(2~3). The stirring reaction was carried out at room temperature for 1–6 hours. The centrifugal washing is performed using deionized water, and the number of centrifugal washing cycles is 2 to 3. The drying temperature is 60~80 ℃, and the drying time is 6~12 h.

3. The method for preparing 2-x-terephthalic acid copper-based MOFs micro / nanosheets according to claim 1, characterized in that: The pre-deprotonated 2-x-terephthalic acid solution is obtained by dissolving the 2-x-terephthalic acid ligand in a deionized aqueous solution of sodium hydroxide, wherein the concentration ratio of the sodium hydroxide solution to the concentration of the 2-x-terephthalic acid ligand is 2:

1.

4. The 2-x-tetraphthalate copper-based MOFs micro / nanosheets prepared by the method of any one of claims 1-3.

5. The 2-x-terephthalic acid copper-based MOFs micro / nanosheets according to claim 4, characterized in that: When x is methyl, the size of the 2-x-terephthalic acid copper-based MOFs micro / nanosheets is 0.3~3 µm, exhibiting obvious macroporous features and a wrinkled sheet-like structure.

6. The 2-x-terephthalic acid copper-based MOFs micro / nanosheets according to claim 4, characterized in that: When x is amino, the size of the 2-x-terephthalic acid copper-based MOFs micro / nanosheets is 0.3~3 µm, exhibiting a wrinkled, continuous sheet-like structure.

7. The 2-x-terephthalic acid copper-based MOFs micro / nanosheets according to claim 4, characterized in that: When x is a hydroxyl group, the size of the 2-x-tetraphthalate copper-based MOFs micro / nanosheets is 0.5~5 µm, exhibiting a wrinkled, continuous sheet-like structure.

8. An application of the 2-x-terephthalic acid copper-based MOFs micro / nanosheets according to claim 4, characterized in that: The 2-x-terephthalic acid copper-based MOFs micro / nanosheets are used for electrocatalytic carbon dioxide reduction.

9. A method for preparing a flow cell cathode, characterized in that, The process includes the following steps: dispersing the 2-x-terephthalic acid copper-based MOFs micro / nanosheets as described in claim 4 in a mixed solution of ethanol and water, ultrasonically dispersing them to form a suspension, then adding a binder to prepare a catalyst slurry, spraying the catalyst slurry onto carbon paper, and drying the carbon paper loaded with the catalyst to obtain the cathode of the flow cell.

10. The method for preparing a flow cell cathode according to claim 9, characterized in that: The volume ratio of ethanol to water is (4~9):1; The mass ratio of the 2-x-terephthalic acid copper-based MOFs micro / nanosheets to the mixed solution of ethanol and water is 1:(1000~3000). The ultrasonic dispersion time is 10~30 min; The adhesive is a naphthol adhesive; The catalyst slurry loading on the carbon paper is 0.25~0.75 mg cm⁻¹. -2 ; The drying temperature is 60~80 ℃, and the drying time is 0.5~2 h.

Images