Pressure-sensitive material based on copper metal-organic framework, preparation method and sensor

Abstract

The present invention discloses a pressure-sensitive material based on a copper metal-organic framework (MOF), a preparation method, and a sensor. The method comprises: by using a polymer microfiber membrane as a substrate, after surface treatment and modification, performing in-situ chemical deposition of metallic copper on a fiber surface, and after further oxidation treatment in an alkaline solution to obtain copper oxide, performing in-situ self-assembly with an organic ligand to obtain the copper metal-organic framework (Cu MOF); the polymer microfiber membrane is prepared by means of electrostatic spinning of polyether sulfone (PES). The reaction conditions of the present invention are mild, and a Cu MOF conductive phase can be uniformly grown on PES fibers in situ, such that a piezoresistive sensor prepared using the conductive composite film as a pressure-sensitive material has good pressure sensing resilience and cycle stability, and has good application prospects in other flexible sensing fields, such as wearable equipment.

Description

A pressure-sensitive material based on copper metal-organic framework, preparation method and sensor Technical Field

[0001] The present invention belongs to the field of composite conductive fiber preparation, and specifically relates to a copper metal-organic framework-based pressure-sensitive material and a preparation method thereof. The pressure-sensitive material can be used for a flexible piezoresistive sensor. Background Art

[0002] In recent years, flexible pressure sensors, due to their excellent flexibility, have gained significant significance in various advanced applications, including human-machine interfaces, electronic skin, and health monitoring. Compared to piezoelectric and capacitive pressure sensors, resistive pressure sensors offer simpler fabrication processes and lower energy consumption. These sensors are typically fabricated by combining conductive functional materials, such as zero-dimensional nanoparticles, one-dimensional nanowires, nanotubes, and two-dimensional nanosheets, with flexible substrates. The trend toward device miniaturization places higher demands on sensor size and shape. Therefore, the challenge is to appropriately design materials that allow conductive functional materials to adhere to complex surfaces without altering the original surface structure, thereby creating sensor materials with specific shapes and sizes. Metal-organic frameworks (MOFs) are inorganic-organic hybrid porous materials composed of metal ion nodes and organic linkers. They are typically prepared by the spontaneous assembly of metal ions and organic ligands and can be grown in situ on various templates. However, their poor conductivity hinders their application in electronic devices. Emerging conductive MOFs are opening up new application opportunities in sensing and electrochemistry. Polyethersulfone (PES), a thermoplastic polymer with excellent overall performance, boasts excellent physical and mechanical properties, acid and alkali resistance, and a high glass transition temperature, and has been widely used in medical devices. Electrospun fiber membranes offer excellent flexibility and a large specific surface area. By electrospinning polyethersulfone to prepare a fiber membrane and then compounding it with the polyethersulfone fiber membrane using in situ coordination growth of a conductive MOF, it is possible to produce a conductive composite membrane with excellent overall performance for applications in wearable devices, medical devices, flexible sensing, and other fields.

[0003] Summary of the Invention

[0004] The object of the present invention is to provide a pressure-sensitive material based on a copper metal-organic framework and a preparation method thereof, wherein the pressure-sensitive material can be used to prepare a flexible piezoresistive sensor.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] In a first aspect, an embodiment of the present invention provides a method for preparing a copper metal-organic framework-based pressure-sensitive material, comprising:

[0007] Step 1: Preparation of PES electrospinning fiber membrane

[0008] The PES solid was dissolved in an organic solvent to prepare an electrospinning solution, and a uniform PES fiber membrane was prepared by electrospinning.

[0009] Step 2: Surface treatment of PES electrospun fiber membrane

[0010] The PES fiber membrane in step 1 is treated under a UV-ozone environment, and the treated fiber membrane is immersed in an ethanol solution of a surface modifier, and then the fiber membrane is taken out, washed, and dried;

[0011] Step 3: Grafting polymer on the surface of PES fiber membrane

[0012] The PES fiber membrane after the surface treatment in step 2 is immersed in an aqueous solution of methacryloyloxyethyl trimethylammonium chloride at room temperature, and the methacryloyloxyethyl trimethylammonium chloride is polymerized on the surface of the fiber membrane under the action of the initiator, and then the fiber membrane is taken out, washed and dried;

[0013] Step 4: Reduce copper ions on the surface of the PES fiber membrane under the action of an activator to obtain metallic copper

[0014] The PES fiber membrane grafted with the polymer in step 3 is immersed in an aqueous solution of an activator at room temperature in a dark environment, washed, and then immersed in a mixed aqueous solution of copper ions and a reducing agent, washed and dried to obtain a fiber membrane PES@Cu with metallic copper grown on the surface;

[0015] Step 5: Oxidize the copper-grown fiber membrane under alkaline conditions to obtain copper oxide

[0016] An alkaline solution containing an oxidant is prepared, and the fiber membrane PES@Cu after growing copper is immersed in the solution at room temperature, and then taken out, washed and dried to obtain the fiber membrane PES@CuO after growing copper oxide;

[0017] Step 6: The copper oxide on the fiber membrane is coordinated with the organic ligand in the solution to obtain Cu MOF

[0018] The fiber membrane PES@CuO on which copper oxide is grown in step five is immersed in an organic ligand solution, subjected to a hydrothermal reaction in a reactor, and washed and dried to obtain a PES fiber membrane PES@Cu MOF on which a Cu MOF conductive phase is grown.

[0019] In the above technical solution, further, in the step 1, the organic solvent is usually a mixed solution of N-dimethylformamide (DMF) and acetone (AC). The dielectric constant and boiling point of DMF and AC are quite different. The solvent ratio of the two affects the fiber morphology and the film forming property of the fiber membrane. The preferred volume ratio of the mixed solution is: V DMF :V AC =17:3.

[0020] Furthermore, in step 1, the solid content of the spinning solution is generally 20-25 wt%.

[0021] Furthermore, in the step 1, the electrospinning parameters are preferably: spinning voltage of 10-16 kV, pushing speed of 0.001-0.003 mm / s, receiving distance of 15 cm, and ambient temperature of 10-30°C.

[0022] Furthermore, the surface modifier in step 2 is a silane coupling agent containing a vinyl group.

[0023] Furthermore, the initiator in step three may be one of potassium persulfate and ammonium persulfate.

[0024] Furthermore, in the step 4, the activator contains Pd 2+ The anionic complex of the copper ions and the reducing agent is typically ammonium tetrachloropalladate. The immersion time in the mixed aqueous solution of copper ions and the reducing agent is preferably 1-50 minutes. Different immersion (i.e., copper growth) times generally result in different copper layer thicknesses, and the conductivity of the fiber membrane after copper growth also varies, ranging from 0-20.6 S / cm. The reducing agent is typically formaldehyde.

[0025] Furthermore, in step 5, the soaking time is preferably 1-30 minutes. Different soaking times generally result in different morphologies. In a short period of time, tubular and rod-shaped copper hydroxide are initially produced. As the reaction time increases, flaky copper oxide appears, and ultimately all flaky copper oxide is produced. The alkaline oxidant solution is typically a mixed aqueous solution of ammonium persulfate and sodium hydroxide.

[0026] Furthermore, the organic ligand in step 6 is 2,3,6,7,10,11-hexahydroxytriphenyl (HHTP), and the concentration of the organic ligand solution is in the range of 0.152-0.606 g / L. The temperature of the hydrothermal reaction is usually 70-85°C.

[0027] In a second aspect, an embodiment of the present invention provides a copper metal-organic framework-based pressure-sensitive material, which is prepared by any of the above methods.

[0028] In a third aspect, an embodiment of the present invention provides a flexible piezoresistive sensor, which uses the above-mentioned pressure-sensitive material as a sensitive layer.

[0029] Advantages of the present invention:

[0030] The present invention prepares a copper metal-organic framework conductive phase on a polyethersulfone electrospun fiber membrane based on in-situ self-assembly of a copper oxide template. Through ultraviolet-ozone treatment, oxygen-containing groups such as hydroxyl groups are generated on the surface of the polyethersulfone fiber, which react with surfactants, and then methacryloyloxyethyltrimethylammonium chloride is grafted to form a cationic polymer to fix the activator, and then the activator is reduced to catalytically prepare Cu, thereby chemically depositing a uniform and continuous layer of copper on the polyethersulfone fiber membrane; under the action of the oxidant, the copper is oxidized into flaky copper oxide, which acts as a template and solid copper source to coordinate with organic ligands for self-assembly to prepare Cu MOF. In summary, the present invention utilizes the characteristics of MOF self-assembly to achieve its in-situ preparation on polyethersulfone fibers. The flexible piezoresistive sensor prepared as a pressure-sensitive material has good pressure sensing recovery and cyclic stability, and is expected to be used in wearable devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 (a) is a schematic diagram of an embodiment of growing copper on a PES electrospun fiber membrane; (b) is a schematic diagram of an embodiment of in-situ coordinated growth of Cu MOF on a PES fiber membrane on which copper is grown;

[0032] Figure 2 (a) is the SEM image of the PES electrospun fiber membrane; (b) is the SEM image of the PES fiber membrane with copper growth; (c) is the conductivity of the fiber membrane with different copper growth times;

[0033] Figure 3 shows the SEM images of the copper-grown PES fiber membrane immersed in the oxidant solution for different times, (af) are 1 min, 3 min, 5 min, 10 min, 20 min, and 30 min respectively;

[0034] Figure 4 (a) is the XRD spectrum of the PES fiber membrane grown with copper; (b) is the XRD spectrum of the PES fiber membrane grown with copper after being immersed in the oxidant solution for 3 minutes; (c) is the XRD spectrum of the PES fiber membrane grown with copper after being immersed in the oxidant solution for 30 minutes;

[0035] Figure 5 (ad) is the SEM images of the in situ formation of Cu MOF by coordination of 2,3,6,7,10,11-hexahydroxytriphenyl with copper oxide on PES fiber membrane at different concentrations, (ad) are 0.152 g / L, 0.303 g / L, 0.303 g / L, and 0.606 g / L, respectively; (e) is the corresponding XRD spectrum;

[0036] Figure 6 (a) and (b) show the current response platform of the PES@Cu MOF conductive composite membrane prepared with 2,3,6,7,10,11-hexahydroxytriphenylene at a concentration of 0.303 g / L under different loads; (c) shows the sensitivity obtained after linear fitting; and (d) shows the 10,000 cycle stability under a certain load. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0038] The present invention discloses a method for preparing a copper metal-organic framework (CuMOF)-based pressure-sensitive material. The method uses a polymer micron fiber membrane as a substrate. After surface treatment and modification, copper metal is chemically deposited in situ on the fiber surface. The surface is further oxidized in an alkaline solution to obtain copper oxide, which is then in situ self-assembled with organic ligands to form a copper metal-organic framework (CuMOF). The polymer micron fiber membrane is prepared by electrospinning polyethersulfone (PES). The chemically deposited copper metal is treated with UV-ozone, then modified with a surface modifier, and deposited with polymer assistance and catalyzed by an activator. The in situ self-assembled CuMOF is achieved by further treating the copper-deposited fiber membrane in an alkaline solution to obtain copper oxide. The copper oxide serves as a solid copper source and template for coordination with organic ligands to form a CuMOF conductive phase. The present invention utilizes mild reaction conditions, allowing the CuMOF conductive phase to grow relatively uniformly in situ on the PES fiber. Piezoresistive sensors prepared using this conductive composite membrane as a pressure-sensitive material exhibit excellent pressure sensing recovery and cyclic stability.

[0039] According to a specific embodiment of the present invention, a method for preparing a copper metal-organic framework-based pressure-sensitive material may include the following steps:

[0040] (1) Preparation of PES electrospun fiber membrane

[0041] PES was weighed and dissolved in a mixture of N-(N-methylformamide) (DMF) and acetone (AC) to form a uniform spinning solvent with a solids content of 20-25 wt%. Electrospun fiber membranes with an average fiber diameter of 0.5-1.5 μm and an average thickness of 100-300 μm were obtained under spinning parameters of 10-16 kV, a feed speed of 0.001-0.003 mm / s, and a receiving distance of 15 cm.

[0042] Preferably, the spinning solution concentration is usually 23 wt %, the electrospinning voltage is 14 kV, the pushing speed is 0.0025 mm / s, the receiving distance is 15 cm, the ambient temperature is 25° C., and the average diameter of the obtained fiber is 1 μm.

[0043] (2) Surface treatment of PES electrospun fiber membrane

[0044] The PES electrospun fiber membrane was treated under a UV-ozone environment, and the treated fiber membrane was immersed in an ethanol solution of vinyltrimethoxysilane for 2 hours, washed and dried.

[0045] (3) Grafting polymers on the surface of PES electrospun fiber membranes

[0046] The surface-treated PES electrospun fiber membrane was immersed in an aqueous solution of methacryloyloxyethyltrimethylammonium chloride at room temperature for 1 hour. Methacryloyloxyethyltrimethylammonium chloride was polymerized on the surface of the fiber membrane under the action of an initiator, potassium persulfate (KPS). The fiber membrane was then taken out, washed, and dried.

[0047] (4) Under the action of the activator, copper ions are reduced on the surface of the PES electrospun fiber membrane to obtain metallic copper

[0048] The PES electrospun fiber membrane after grafting the polymer was immersed in an aqueous solution of ammonium tetrachloropalladate ((NH4)2PdCl4) at room temperature in a dark environment for 30 minutes. After washing, it was immersed in a mixed aqueous solution of copper ion aqueous solution A and reducing agent aqueous solution B for 1-50 minutes. After washing and drying, a fiber membrane with metallic copper grown on the surface (PES@Cu) was obtained.

[0049] The concentration of the ammonium tetrachloropalladate aqueous solution is preferably 0.005 mol / L;

[0050] The copper ion aqueous solution A is preferably a mixed solution of sodium hydroxide, copper sulfate pentahydrate, and potassium sodium tartrate, with concentrations of 0.12 g / L, 0.13 g / L, and 0.29 g / L, respectively;

[0051] The reducing agent aqueous solution B is preferably an aqueous solution of formaldehyde with a concentration of 9.50 mL / L;

[0052] The electrical conductivity of the fiber membrane grown with metallic copper is in the range of 0-20.6 S / cm.

[0053] Preferably, the growth time of copper is 20 minutes. At this time, the grown copper layer will not be completely consumed in the solution during the subsequent reaction due to being too thin, nor will it be broken due to being too thick.

[0054] (5) Oxidizing the copper-grown fiber membrane under alkaline conditions to obtain copper oxide

[0055] An alkaline solution containing an oxidant is prepared, and the fiber membrane after copper growth is immersed in the solution at room temperature for 1-30 minutes. The fiber membrane is then taken out, washed, and dried to obtain copper oxide (PES@CuO).

[0056] The copper-grown fiber membrane forms different morphologies when immersed in the oxidant solution for different periods of time. In a short period of time, tubular and rod-shaped copper hydroxides are first generated. As the reaction time increases, flaky copper oxide appears, and eventually all flaky copper oxide is generated.

[0057] The time for the reaction to generate tubular and rod-shaped copper hydroxide was very short and difficult to control, and the sizes of the copper hydroxide tubes and rods were too large. Ultimately, fiber membranes grown with flake copper oxide were used for subsequent experiments.

[0058] (6) The copper oxide on the fiber membrane is coordinated with the organic ligand in the solution to obtain Cu MOF

[0059] The copper oxide fiber membrane was immersed in a solution of an organic ligand 2,3,6,7,10,11-hexahydroxytriphenyl (HHTP) and subjected to a hydrothermal reaction in a reactor at 70°C. After washing and drying, a PES fiber membrane with a Cu MOF conductive phase (PES@Cu MOF) was obtained.

[0060] The concentration of the organic ligand 2,3,6,7,10,11-hexahydroxytriphenyl (HHTP) is 0.152-0.606 g / L;

[0061] Preferably, the PES@Cu MOF conductive composite fiber membrane prepared with 2,3,6,7,10,11-hexahydroxytriphenyl (HHTP) at a concentration of 0.303 g / L has a more uniform morphology, and is therefore used for subsequent pressure-sensitive performance testing.

[0062] In the following examples, in the step of growing metallic copper on a PES fiber membrane, the fiber membrane is immersed in a mixed solution of copper ions and a reducing agent for 1-50 min, and a fiber membrane coated with different copper layer thicknesses can be obtained; in the step of further preparing copper oxide on the PES fiber membrane on which copper is grown, the experiment is carried out using a fiber membrane grown for 20 min of copper, and the immersion time in an alkaline oxidant solution is 1-30 min; in the step of in situ self-assembly of a Cu MOF conductive phase based on a copper oxide template and an organic ligand, the experiment is carried out using copper oxide obtained by oxidation for 30 min, and the concentrations of the organic ligands are 0.152 g / L, 0.303 g / L, 0.303 g / L, and 0.606 g / L, respectively.

[0063] In the pressure-sensitive test step using the PES@Cu MOF conductive composite film as the pressure-sensitive material, the conductive composite film is cut into small discs with a diameter of 8 mm and placed on a screen-printed silver electrode. There is an insulating area in the middle of the silver electrode, and the two sides of the insulating area are respectively connected to the positive and negative poles of the digital source meter. Pressure is applied to the conductive composite film using a push-pull force gauge, and the resistance value is read on the digital source meter. A pressure-resistance curve is established, and the slope of the curve is obtained by linear fitting, that is, the sensitivity of the conductive composite film as a pressure sensor.

[0064] Example 1:

[0065] Comparison of different growth times of copper on PES fiber membrane

[0066] The preparation method for growing metallic copper on a PES fiber membrane comprises the following steps:

[0067] 1. First, 5.52g of PES was dissolved in a mixed solvent of 16.15g of NN-dimethylformamide and 2.37g of acetone at room temperature to form a uniform spinning solution with a solid content of 23wt%. Under the spinning parameters of 14kV, a feed speed of 0.0025mm / s, a receiving distance of 15cm, and an ambient temperature of 25°C, an electrospun fiber membrane with an average fiber diameter of 1μm and an average thickness of 150μm was obtained.

[0068] 2. Measure 38 mL of anhydrous ethanol, 0.4 mL of glacial acetic acid, 1.6 mL of deionized water, and 1.6 mL of vinyltrimethoxysilane and place them in beaker a. Ultrasonicate and mix them evenly. 3 The spun fiber membrane was treated in a UV-ozone environment for 30 seconds; the spun fiber membrane was completely immersed in the solution in beaker a at room temperature for 2 hours, and then taken out and washed three times with deionized water.

[0069] 3. Measure 20 mL of deionized water, weigh 4 g of methacryloyloxyethyltrimethylammonium chloride, and 0.1 g of potassium persulfate and place them in beaker b. Ultrasonicate until all the solids are dissolved. Immerse the fiber membrane after washing in 2 in the solution in beaker b at 80°C for 1 hour, then take it out, wash it three times with deionized water, and dry it.

[0070] 4. The fiber membrane dried in step 3 was immersed in 0.005 mol / L ammonium tetrachloropalladate solution at room temperature in a dark environment for 30 minutes, then taken out, washed three times with deionized water and dried.

[0071] 5. Weigh 0.24 g of sodium hydroxide, 0.26 g of copper sulfate pentahydrate, and 0.58 g of potassium sodium tartrate and dissolve them in beaker c containing 20 mL of deionized water, recorded as solution A; measure 19.2 mL of deionized water and 500 μL of formaldehyde solution and place them in beaker d, and ultrasonicate until the solution is uniform, recorded as solution B; add solution B to solution A, ultrasonically mix evenly, recorded as solution C; immerse the fiber membrane dried in 4 in solution C, soak it at room temperature for 1-50 min, then wash it three times with deionized water and dry it to obtain copper-coated PES fiber membrane PES@Cu.

[0072] The SEM images and electrical conductivity of the obtained PES@Cu are shown in Figure 2 (b) (sample soaked for 20 minutes) and (c) (conductivity of samples obtained at different soaking times).

[0073] Example 2:

[0074] The PES@Cu fiber membrane obtained by growing copper for 20 minutes was used for subsequent experiments.

[0075] Comparison of the growth of copper PES fiber membranes immersed in alkaline oxidant solution for different time

[0076] The method for further preparing copper oxide on the PES fiber membrane on which copper is grown comprises the following steps:

[0077] 1. First, 5.52g of PES was dissolved in a mixed solvent of 16.15g of NN-dimethylformamide and 2.37g of acetone at room temperature to form a uniform spinning solution with a solid content of 23wt%. Under the spinning parameters of 14kV, a feed speed of 0.0025mm / s, a receiving distance of 15cm, and an ambient temperature of 25°C, an electrospun fiber membrane with an average fiber diameter of 1μm and an average thickness of 150μm was obtained.

[0078] 2. Measure 38 mL of anhydrous ethanol, 0.4 mL of glacial acetic acid, 1.6 mL of deionized water, and 1.6 mL of vinyltrimethoxysilane and place them in beaker a. Ultrasonicate and mix them evenly. 3 The spun fiber membrane was treated in a UV-ozone environment for 30 seconds; the spun fiber membrane was completely immersed in the solution in beaker a at room temperature for 2 hours, and then taken out and washed three times with deionized water.

[0079] 3. Measure 20 mL of deionized water, weigh 4 g of methacryloyloxyethyltrimethylammonium chloride, and 0.1 g of potassium persulfate and place them in beaker b. Ultrasonicate until all the solids are dissolved. Immerse the fiber membrane after washing in 2 in the solution in beaker b at 80°C for 1 hour, then take it out, wash it three times with deionized water, and dry it.

[0080] 4. The fiber membrane dried in step 3 was immersed in 0.005 mol / L ammonium tetrachloropalladate solution at room temperature in a dark environment for 30 minutes, then taken out, washed three times with deionized water and dried.

[0081] 5. Weigh 0.24g of sodium hydroxide, 0.26g of copper sulfate pentahydrate, and 0.58g of potassium sodium tartrate and dissolve them in beaker c containing 20mL of deionized water, recorded as solution A; measure 19.2mL of deionized water and 500μL of formaldehyde solution and place them in beaker d, and ultrasonicate until the solution is uniform, recorded as solution B; add solution B to solution A, ultrasonically mix evenly, recorded as solution C; immerse the fiber membrane dried in 4 in solution C, soak it at room temperature for 20min, then wash it three times with deionized water and dry it to obtain a copper-coated PES fiber membrane.

[0082] 6. Prepare a 10 mol / L sodium hydroxide solution and record it as solution D; prepare a 1 mol / L ammonium persulfate solution and record it as solution E; measure 4 mL of solution D, 2 mL of solution E, and 9 mL of deionized water in beaker e and mix them evenly by ultrasonication; immerse the copper-coated PES fiber membrane in 5 in the solution in beaker e, soak it at room temperature for 1-30 minutes, then wash it three times with deionized water and dry it to obtain a copper hydroxide / copper oxide-coated PES fiber membrane.

[0083] The SEM images of the samples obtained at different immersion times are shown in Figure 3.

[0084] Example 3:

[0085] The PES@CuO membrane obtained by soaking in alkaline oxidant solution for 30 min was used for subsequent experiments to compare the different concentrations of organic ligand 2,3,6,7,10,11-hexahydroxytriphenyl (HHTP) as variables.

[0086] The method for preparing the in-situ self-assembled Cu MOF conductive phase on the PES fiber membrane based on the copper oxide template comprises the following steps:

[0087] 1. First, 5.52g of PES was dissolved in a mixed solvent of 16.15g of NN-dimethylformamide and 2.37g of acetone at room temperature to form a uniform spinning solution with a solid content of 23wt%. Under the spinning parameters of 14kV, a feed speed of 0.0025mm / s, a receiving distance of 15cm, and an ambient temperature of 25°C, an electrospun fiber membrane with an average fiber diameter of 1μm and an average thickness of 150μm was obtained.

[0088] 2. Measure 38 mL of anhydrous ethanol, 0.2 mL of glacial acetic acid, 1.6 mL of deionized water, and 1.6 mL of vinyltrimethoxysilane and place them in beaker a. Ultrasonicate and mix them evenly. 3 The spun fiber membrane was treated in a UV-ozone environment for 30 seconds; the spun fiber membrane was completely immersed in the solution in beaker a at room temperature for 2 hours, and then taken out and washed three times with deionized water.

[0089] 3. Measure 20 mL of deionized water, weigh 4 g of methacryloyloxyethyltrimethylammonium chloride, and 0.1 g of potassium persulfate and place them in beaker b. Ultrasonicate until all the solids are dissolved. Immerse the fiber membrane after washing in 2 in the solution in beaker b at 80°C for 1 hour, then take it out, wash it three times with deionized water, and dry it.

[0090] 4. The fiber membrane dried in step 3 was immersed in 0.005 mol / L ammonium tetrachloropalladate solution at room temperature in a dark environment for 30 minutes, then taken out, washed three times with deionized water and dried.

[0091] 5. Weigh 0.24g of sodium hydroxide, 0.26g of copper sulfate pentahydrate, and 0.58g of potassium sodium tartrate and dissolve them in beaker c containing 20mL of deionized water, recorded as solution A; measure 19.2mL of deionized water and 500μL of formaldehyde solution and place them in beaker d, and ultrasonicate until the solution is uniform, recorded as solution B; add solution B to solution A, ultrasonically mix evenly, recorded as solution C; immerse the fiber membrane dried in 4 in solution C, soak it at room temperature for 20min, then wash it three times with deionized water and dry it to obtain a copper-coated PES fiber membrane.

[0092] 6. Prepare a 10 mol / L sodium hydroxide solution and record it as solution D; prepare a 1 mol / L ammonium persulfate solution and record it as solution E; measure 4 mL of solution D, 2 mL of solution E, and 9 mL of deionized water in beaker e and mix them evenly by ultrasonication; immerse the copper-coated PES fiber membrane in 5 in the solution in beaker e for 30 minutes at room temperature, then wash it three times with deionized water and dry it to obtain a copper oxide-coated PES fiber membrane.

[0093] 7. Weigh 5-20 mg of 2,3,6,7,10,11-hexahydroxytriphenyl (HHTP) into a glass bottle, measure 3 mL of NN dimethylformamide respectively, and ultrasonically dissolve it; add 30 mL of deionized water and continue ultrasonically homogenizing; immerse the copper oxide-coated PES fiber membrane in 6 in the solution in the glass bottle and tighten the bottle cap, incubate at 70°C for 30 minutes, then wash and dry with ethanol and deionized water to obtain a Cu3(HHTP)2(Cu MOF)-coated PES fiber membrane structure.

[0094] The SEM and XRD patterns of samples prepared with different HHTP concentrations are shown in Figure 5 .

[0095] The pressure-sensitive properties of the PES@Cu MOF conductive composite membrane prepared with 2,3,6,7,10,11-hexahydroxytriphenylene at a concentration of 0.303 g / L are shown in Figure 6. (a) and (b) show that the composite membrane has good loading-unloading stability within a load of 4.6 kPa; (c) shows that it has a 9.236 kPa load within the range of 0-1 kPa. -1 The sensitivity is 5.645kPa in the range of 1-7kPa -1 (d) shows that it still has good stability and recovery after 10,000 cycles of loading and unloading.

[0096] The present invention uses the above-described embodiments to illustrate the detailed methods of the present invention. The described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without any creative work are within the scope of protection of the present invention.

Claims

1. A method for preparing a copper metal-organic framework-based pressure-sensitive material, characterized in that: The following steps are involved: Step 1: Preparation of PES electrospinning fiber membrane The PES solid is dissolved in an organic solvent to prepare an electrospinning solution, and a uniform PES fiber membrane is prepared by electrospinning; Step 2: Surface treatment of PES electrospun fiber membrane The PES fiber membrane in step 1 is treated in an ultraviolet-ozone environment, and the treated fiber membrane is immersed in an ethanol solution of a surface modifier, and then the fiber membrane is taken out, washed and dried; the surface modifier is a silane coupling agent containing a vinyl group; Step 3: Grafting polymer on the surface of PES fiber membrane The PES fiber membrane surface-treated in step 2 is immersed in an aqueous solution of methacryloyloxyethyl trimethylammonium chloride at room temperature, and the methacryloyloxyethyl trimethylammonium chloride is polymerized on the surface of the fiber membrane under the action of the initiator, and then the fiber membrane is taken out, washed and dried; Step 4: Reduce copper ions on the surface of the PES fiber membrane under the action of an activator to obtain metallic copper The PES fiber membrane grafted with the polymer in step 3 is immersed in an aqueous solution of an activator at room temperature in a dark environment, and then immersed in a mixed aqueous solution of copper ions and a reducing agent after washing. After washing and drying, a fiber membrane PES@Cu with metallic copper grown on the surface is obtained; the activator is a Pd 2+ Anionic complexes of Step 5: Oxidize the fiber membrane after growing copper under alkaline conditions to obtain copper oxide An alkaline solution containing an oxidant is prepared, and the fiber membrane PES@Cu after growing copper is immersed in the solution at room temperature, and then taken out, washed and dried to obtain the fiber membrane PES@CuO after growing copper oxide; the immersion time is 1-30 minutes; Step 6: The copper oxide on the fiber membrane is coordinated with the organic ligand in the solution to obtain Cu MOF The fiber membrane PES@CuO grown with copper oxide in step 5 is immersed in an organic ligand solution, subjected to hydrothermal reaction in a reactor, and washed and dried to obtain a PES fiber membrane PES@Cu MOF grown with a Cu MOF conductive phase; the organic ligand is 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP), and the concentration range of the organic ligand solution is 0.152-0.606 g / L.

2. The method for preparing a copper metal-organic framework-based pressure-sensitive material according to claim 1, characterized in that: In the step 1, the organic solvent is a mixed solution of N-dimethylformamide (DMF) and acetone (AC), and the solid content of the spinning solution is 20-25wt%.

3. The method for preparing a copper metal-organic framework-based pressure-sensitive material according to claim 1, characterized in that: In the step 1, the electrospinning parameters are: spinning voltage is 10-16 kV, pushing speed is 0.001-0.003 mm / s, receiving distance is 15 cm, and ambient temperature is 10-30°C.

4. The method for preparing a copper metal-organic framework-based pressure-sensitive material according to claim 1, characterized in that: In the step 4, the immersion time in the mixed aqueous solution of copper ions and reducing agent is 1-50 minutes.

5. A copper metal-organic framework-based pressure-sensitive material, characterized in that: The method is prepared by the method according to any one of claims 1 to 4.

6. A flexible piezoresistive sensor, characterized in that: The pressure-sensitive material as claimed in claim 5 is used as the sensitive layer.

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