Ion sensor member using carbon nanotube composite material having bound thereto metal-organic framework modified with organic molecules, ion sensor, and method for manufacturing ion sensor

Abstract

Disclosed are an ion sensor member using a carbon nanotube composite material to which a metal-organic framework modified with organic molecules is bound, an ion sensor, and a method for manufacturing an ion sensor. An ion sensor member according to an embodiment may include a composite material in which a metal-organic framework is uniformly bound to the surface of carbon nanotubes. In this case, the metal-organic framework may be modified by functionalizing an organic molecule including at least one unshared electron pair.

Description

Ion sensor component, ion sensor, and method for fabricating the ion sensor using a carbon nanotube composite material bound to a metal-organic framework modified with organic molecules

[0001] Embodiments of the present invention relate to an ion sensor member, an ion sensor, and a method for fabricating an ion sensor utilizing a carbon nanotube composite material to which a metal-organic framework modified with organic molecules is bonded.

[0002] Project ID: (2025-RISE-01-027-04)

[0003] Assignment No.: 04

[0004] Ministry Name: Ministry of Education

[0005] Name of Project Management Agency: Seoul RISE Center

[0006] Research Project Name: Seoul Metropolitan Government Regional Innovation-Centered University Support System (RISE)

[0007] Research Project Title: Revitalization of the Industry-Academic Cooperation Ecosystem

[0008] Contribution rate: 100%

[0009] Principal Research Institution: Hanyang University (Hanyang RISE Project Group)

[0010] Research Period: June 1, 2025 – February 28, 2026

[0011] Carbon nanotube-based ion sensors exist for detecting harmful heavy metal cations contained in solutions for purposes such as water pollution monitoring. However, these carbon nanotube-based ion sensors have problems such as low selectivity and sensitivity, material limitations, and difficulty in securing reliable sensor characteristics depending on the measurement technology.

[0012] The present invention provides an ion sensor component, an ion sensor, and a method for fabricating the ion sensor using a carbon nanotube composite material to which a metal-organic framework modified with organic molecules is bonded.

[0013] The present invention provides an ion sensor member comprising a composite material in which a metal-organic framework is uniformly bound to the surface of a carbon nanotube, wherein the metal-organic framework is modified by functionalizing an organic molecule containing at least one non-covalent electron pair.

[0014] According to one aspect, the organic molecule comprising at least one non-covalent electron pair may be characterized by including a single bond or a double bond to at least one element among oxygen (O), sulfur (S), nitrogen (N), and phosphorus (P).

[0015] According to another aspect, the molecular weight (M) of an organic molecule comprising at least one non-covalent electron pair is w ) may be characterized by being included in the range of 10 to 10,000 g / mol.

[0016] According to another aspect, the organic molecule comprising at least one non-covalent electron pair may be characterized by further comprising 3,5-bis(trifluoromethyl)benzene, which is an electron-pulling group, as a functional group.

[0017] According to another aspect, the organic ligand constituting the metal-organic framework may be characterized by comprising at least one functional group among carboxylic acid (-COOH), amine (-NH2), and hydroxyl (-OH) groups.

[0018] According to another aspect, the diameter of the metal-organic framework may be characterized as being in the range of 1 nm to 100 μm.

[0019] According to another aspect, the specific surface area of ​​the metal-organic framework is 100 m² 2 / g to 5,000 m 2 It can be characterized as being included within the range of / g.

[0020] According to another aspect, the carbon nanotube may be characterized by having at least one of a carboxylic acid (-COOH) and a hydroxyl (-OH) group on its surface.

[0021] The present invention provides an ion sensor comprising: the ion sensor member; and a glassy carbon electrode (GCE) coated with the ion sensor member, wherein the ion sensor member detects a change in current based on a chemical reaction between the composite material containing the ion sensor member and a cation contained in an aqueous solution upon the application of voltage to the glassy carbon electrode coated with the ion sensor member.

[0022] According to one side, the cation contained in the aqueous solution is Na + , K + , Li + , Sc 2+ , V 2+ , Ti 2+ , Be 2+ , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , Ra 2+ , Ru 2+ , Mo 2+ , Fe 2+ , Cd 2+ , Cr 2+ , Co 2+ , Cu 2+ , Pb 2+ , Mn 2+ , Hg 2+ , Ni 2+ , Pt 2+ , Sn 2+ , Zn 2+ , Ag 2+ , Hf 2+ , Au 2+ , Al 3+ , Fe 3+ , Cr 3+ , Sn 4+ , Ti 4+ , and Mn 4+It may be characterized by including at least one of the following.

[0023] According to another aspect, the ion sensor may be characterized by being capable of simultaneously detecting various types of metal cations contained in the aqueous solution through the detected current change.

[0024] (a) a step of growing a metal-organic framework on the surface of a carbon nanotube through a solvothermal synthesis method; (b) a step of chemically modifying the metal-organic framework bound to the surface of the carbon nanotube using an organic molecule containing at least one non-covalent electron pair; (c) a step of preparing a dispersion solution by dispersing a carbon nanotube-based composite material bound to the metal-organic framework modified using the organic molecule in a solvent; and (d) a step of uniformly coating the dispersion solution onto a glass carbon electrode to produce a working electrode coated with the composite material. A method for fabricating an ion sensor is provided.

[0025] According to one aspect, the weight ratio between the metal precursor and the carbon nanotube for growing a metal-organic framework on the surface of the carbon nanotube through the solvothermal synthesis method may be characterized as being in the range of 0.01 to 500.

[0026] According to another aspect, the solvent used in the above solvothermal synthesis method may be characterized by comprising at least one of ethanol, methanol, propanol, butanol, isopropyl alcohol (IPA), dimethylformamide (DMF), acetone, acetonitrile, toluene, tetrahydrofuran, 1,2-dichlorobenzene, and water.

[0027] According to another aspect, the temperature range of the heat treatment for the solvothermal synthesis method may be characterized as being included in the range of 50 °C to 500 °C.

[0028] According to another aspect, in step (b) above, the metal-organic framework may be characterized by being modified by forming a secondary amine (-NH) through a chemical reaction between a primary amine (-NH2) group contained in the organic ligand and a functional group contained in the organic molecule.

[0029] According to another aspect, in step (d) above, the composite material may be coated on the top of the glass carbon electrode with a thickness ranging from 0.1 nm to 500 μm.

[0030] According to another aspect, the single and multiple types of cations contained in an aqueous solution can be detected by a differential pulse anode peeling voltage and current measurement method using a working electrode coated with the composite material.

[0031] According to another aspect, the differential pulse anode peeling voltage and current measurement may be characterized by applying a voltage included in the range of -2 V to 2 V to the working electrode.

[0032] By modifying a metal-organic framework using an organic molecule containing at least one non-covalent electron pair and utilizing a composite material in which the modified metal-organic framework is uniformly bound to the top of a carbon nanotube, it is possible to provide an ion sensor member, an ion sensor, and a method for fabricating an ion sensor capable of detecting multiple or single types of cations contained in an aqueous solution with enhanced sensitivity.

[0033] An organic molecule containing at least one non-covalent electron pair can act as a Lewis acid by forming a single or double bond with at least one element among oxygen (O), sulfur (S), nitrogen (N) to phosphorus (P), and a cation can act as a Lewis base, allowing the cation to be detected with high sensitivity through a chemical acid-base reaction between the organic molecule and the cation.

[0034] An ion sensor can be fabricated as an electrochemical sensor by uniformly coating a carbon nanotube composite material functionalized with modified organic molecules onto the top of a glass carbon electrode of a working electrode. This ion sensor can generate current in the glass carbon electrode of the working electrode coated with the composite material by inducing an acid-reduction reaction of cations contained in an aqueous solution according to the applied voltage through an electrochemical-based differential pulse anode peeling voltage-current measurement method. Furthermore, due to the chemical reaction between the organic molecules contained in the composite material and the cations, the ion sensor exhibits a high current change for multiple or single types of cations contained in the aqueous solution compared to a pure glass carbon electrode without the composite material coating, thereby enabling the detection of cations with enhanced sensitivity.

[0035] FIG. 1 is a schematic diagram illustrating an example of an ion sensor according to an embodiment of the present invention.

[0036] FIG. 2 is a flowchart illustrating an example of a method for manufacturing an ion sensor according to an embodiment of the present invention.

[0037] Figure 3 is a photograph of a carbon nanotube with a metal-organic framework attached, fabricated according to Example 1 of the present invention.

[0038] Figure 4 is a scanning electron microscope (SEM) image of a carbon nanotube with a metal-organic framework attached, fabricated according to Example 1 of the present invention.

[0039] Figure 5 is a photograph of a carbon nanotube to which a metal-organic framework modified with an organic molecule containing at least one non-covalent electron pair, fabricated according to Example 1 of the present invention, is attached.

[0040] FIG. 6 is a scanning electron microscope image of a composite material in which a metal-organic framework modified with an organic molecule containing sulfur (S) atoms, prepared according to Examples 1 and 2 of the present invention, is uniformly bonded to the top of a carbon nanotube.

[0041] FIG. 7 is a scanning electron microscope image of a composite material in which a metal-organic framework modified with an organic molecule containing oxygen (O) atoms, prepared according to Examples 1 and 2 of the present invention, is uniformly bonded to the top of a carbon nanotube.

[0042] Figure 8 is an X-ray diffraction graph of a carbon nanotube with a metal-organic framework uniformly bonded according to Examples 1 and 2 of the present invention, and a composite material in which a metal-organic framework modified with an organic molecule is uniformly bonded to the top of a carbon nanotube.

[0043] Figure 9 is a Fourier-Transform Infrared Spectroscopy (FT-IR) graph of a carbon nanotube with a metal-organic framework uniformly bonded according to Examples 1 and 2 of the present invention, and a composite material in which a metal-organic framework modified with an organic molecule is uniformly bonded to the top of a carbon nanotube.

[0044] FIG. 10 is a photograph of a dispersion solution of a composite material in which a metal-organic framework modified with an organic molecule containing at least one non-covalent electron pair, prepared according to Experimental Example 1 of the present invention, is uniformly bound to the surface of a carbon nanotube.

[0045] FIG. 11 is a photograph of a composite material coated on a working electrode in which a metal-organic framework modified with an organic molecule containing sulfur (S) atoms, prepared according to Examples 1 and 2 of the present invention, is uniformly bonded to the surface of a carbon nanotube.

[0046] FIG. 12 is a graph evaluating the voltage-current characteristics for various metal cations using a composite material in which a metal-organic framework modified with an organic molecule containing sulfur (S) atoms, prepared according to Examples 1 and 2 of the present invention, is uniformly bound to the surface of a carbon nanotube.

[0047] FIG. 13 is a photograph of a composite material coated on a working electrode in which a metal-organic framework modified with an organic molecule containing oxygen (O) atoms, prepared according to Examples 1 and 2 of the present invention, is uniformly bonded to the surface of a carbon nanotube.

[0048] FIG. 14 is a graph evaluating the voltage-current characteristics for various metal cations using a composite material in which a metal-organic framework modified with an organic molecule containing oxygen (O) atoms, prepared according to Examples 1 and 2 of the present invention, is uniformly bound to the surface of a carbon nanotube.

[0049] FIG. 15 is a photograph of a working electrode not coated with a sensing material, prepared according to Comparative Example 1 of the present invention.

[0050] FIG. 16 is a graph evaluating the voltage-current characteristics for various metal cations using working electrodes prepared according to Experimental Example 1, Experimental Example 2 and Comparative Example 1 of the present invention.

[0051] FIG. 17 shows a cadmium (Cd) using a working electrode fabricated according to Experimental Example 1, Experimental Example 2, and Comparative Example 1 of the present invention. 2+ This is a graph evaluating the voltage-current characteristics for cations.

[0052] FIG. 18 shows a copper (Cu) working electrode prepared according to Experimental Example 1, Experimental Example 2 and Comparative Example 1 of the present invention. 2+This is a graph evaluating the voltage-current characteristics for cations.

[0053] FIG. 19 shows mercury (Hg) using a working electrode prepared according to Experimental Example 1, Experimental Example 2 and Comparative Example 1 of the present invention. 2+ This is a graph evaluating the voltage-current characteristics for cations.

[0054] Hereinafter, embodiments will be described in detail with reference to the attached drawings.

[0055] Embodiments of the present invention relate to an ion sensor member, an ion sensor, and a method for fabricating an ion sensor utilizing a composite material in which metal-organic frameworks modified with organic molecules containing lone pair electrons capable of chemically interacting with cations are uniformly bound to the top of a carbon nanotube.

[0056] Metal-organic frameworks (MOFs) can possess pores of a specific size and a high specific surface area through chemical bonding between metal nodes and organic ligands. The surface of the MOF can be further modified by utilizing organic molecules capable of chemically interacting with cations. In this case, the MOF modified with organic molecules exhibits a high surface chemical reactivity toward specific cations, enabling the detection of trace amounts of cations. In particular, the non-covalent electron pairs contained in the organic molecules act as Lewis bases, and the metal cations act as Lewis acids, allowing for selective acid-base reactions. Carbon nanotube composites in which MOFs modified with organic molecules are uniformly bound can be utilized as sensing materials for cation detection in electrochemical-based ion sensors. Such ion sensors can be used as water pollution monitoring sensors to detect heavy metal ions contained in aqueous solutions.

[0057] FIG. 1 is a schematic diagram illustrating an example of an ion sensor according to an embodiment of the present invention. An ion sensor for detecting trace amounts of cations contained in an aqueous solution may include a working electrode (001). The working electrode (001) may be fabricated by coating a carbon nanotube (003)-based composite material on top of a glass carbon electrode (002). Metal-organic frameworks (004) may be uniformly attached to the carbon nanotubes (003), and these metal-organic frameworks (004) may be in a modified state functionalized with organic molecules (005 and / or 006) containing lone pair electrons. The organic molecules (005 and / or 006) may chemically interact with cations (007).

[0058] Thus, the functional group provided through the organic molecule (005 and / or 006) includes at least one non-covalent electron pair, and by providing the non-covalent electron pair to the cation (007), which is a Lewis acid, a chemical acid-base reaction can occur with the cation (007). In this case, the ion sensor can have its sensing characteristics for the cation (007) improved through the acid-base chemical reaction, thereby increasing its sensitivity. The organic molecule (005 and / or 006) containing at least one non-covalent electron pair can be functionalized on the surface of a metal-organic framework (004) having a large specific surface area, and the metal-organic framework (004) modified with the organic molecule (005 and / or 006) can be attached to the top of a carbon nanotube (003) having excellent electrical conductivity to form a composite material for the ion sensor. The composite material can be utilized as an ion sensor component by inducing oxidation and reduction through an electrochemical reaction. Since the ion sensor utilizing such an ion sensor component can detect multiple or single types of cations (007) contained in an aqueous solution according to concentration, it is possible to provide a cation sensor that can be used for water quality management.

[0059] An organic molecule (005 and / or 006) containing at least one non-covalent electron pair may include non-metallic elements included in Groups 15 to 16 of the periodic table, such as oxygen (O), sulfur (S), nitrogen (N), and phosphorus (P). These non-metallic elements form single or double bonds within the organic molecule (005 and / or 006), and electrons that do not participate in the bonding may pair up to form non-covalent electron pairs. The non-covalent electron pair may be a Lewis base that provides electrons to a heterogeneous component other than the organic molecule (005 and / or 006). Here, the heterogeneous component may be a cation (007) which is a Lewis acid that is an electron acceptor. Through such acid-base chemical reactions, organic molecules (005 and / or 006) containing non-covalent electron pairs can form a complex with a cation (007). The strong chemical bond between the organic molecules (005 and / or 006) and the cation (007) obtained through this complex formation can provide enhanced ion sensing performance.

[0060] The metal-organic framework (004) can have a constant pore size and a high specific surface area through the chemical bonding of metal nodes and organic ligands. Therefore, the metal-organic framework (004) modified with organic molecules (005 and / or 006) can exhibit excellent sensing performance for cations (007) because it can maximize chemical reactions for cations (007) at the surface. To modify the surface of the metal-organic framework (004) using organic molecules (005 and / or 006), the organic ligand of the metal-organic framework (004) may additionally include a functional group for functionalizing the organic molecules (005 and / or 006). The functional group of such organic ligand may include at least one of a carboxylic acid (-COOH), an amine (-NH2), and a hydroxyl (-OH) group. Organic molecules (005 and / or 006) containing non-covalent electron pairs can be functionalized by utilizing the functional groups of organic ligands on the surface of the metal-organic framework (004) through a post-processing process. The metal-organic framework (004) modified with organic molecules (005 and / or 006) containing at least one non-covalent electron pair can exhibit a chemical Lewis acid-base reaction sensitive and selectively to cations (007), including a high specific surface area and porosity.

[0061] Meanwhile, the metal-organic framework (004) can be attached to the surface along the carbon nanotube (003) having a one-dimensional structure. For example, the metal-organic framework (004) can be attached to the surface of the carbon nanotube (003) using a chemical bonding method. This chemical bonding method enables the metal-organic framework (004) to be uniformly and mechanically strongly bonded to the top of the carbon nanotube (003) with minimal aggregation. This chemical bonding method may include a solvothermal synthesis method utilizing a solution in which the carbon nanotube (003) is dispersed with a precursor to form the metal-organic framework (004). The carbon nanotube (003) can chemically grow a metal-organic framework (004) uniformly on the surface of the carbon nanotube (003) by including at least one of a carboxylic acid (-COOH) and a hydroxyl (-OH) group on the surface.

[0062] A metal-organic framework (004) bonded to the surface of a carbon nanotube (003) via a chemical bonding method can form a carbon nanotube-based composite material by modifying it into an organic molecule (005 and / or 006) through a post-processing process. At this time, a change in electrical properties may occur in the composite material through a chemical reaction between an organic molecule (005 and / or 006) containing at least one non-covalent electron pair and a cation (007). As previously described, the chemical reaction is an acid-base reaction between an organic molecule (005 and / or 006) which is a Lewis base and a cation (007) which is a Lewis acid, and a composite between the organic molecule (005 and / or 006) and the cation (007) may be formed by this acid-base reaction. An ion sensor can detect the cation (007) with enhanced sensitivity by utilizing the change in electrical properties of this composite material.

[0063] The ion sensor can be fabricated as an electrochemical sensor. Such an electrochemical sensor can operate based on a Differential Pulse Anodic Stripping Voltammetry (DPASV) method, which measures the current generated according to a constantly changing applied voltage. For differential pulse anodic stripping voltammetry, the electrochemical sensor may include a potentiostat connected to a 3-electrode system consisting of a glassy carbon electrode (GCE, 002) used as a working electrode (001), a platinum counter electrode (Pt wire counter electrode), and a silver / silver chloride reference electrode (Ag / AgCl reference electrode). To this end, an ion sensor member containing a composite material may be uniformly coated on the top of the working electrode (001). Differential pulse anode stripping voltage and current measurement can reduce and adsorb metal cations (e.g., cations (007)) dissolved in an aqueous solution onto a glass carbon electrode (002) coated with a composite material by applying a negative voltage. Subsequently, a differential pulse with a positive voltage is applied to oxidize the metal reduced on the glass carbon electrode (002) coated with the composite material, causing it to undergo an ionization process. Through the ionization process, the reduced metal is stripped from the anode, thereby forming a current. The more metal adsorbed through reduction, the greater the amount of metal cations stripped by the differential pulse applied with a positive voltage, and the higher the intensity of the generated current. The composite material coated on the glass carbon electrode (002) of the working electrode (001) may include organic molecules (005 and / or 006) containing non-covalent electron pairs that react sensitively with metal cations, thereby adsorbing more metal cations when a negative voltage is applied, which can increase the amount of reduced metal.In this way, the glass carbon electrode (002) coated with a composite material can be used as a cation sensor to detect cations (007) contained in an aqueous solution.

[0064] As such, an ion sensor member according to one embodiment of the present invention may include a composite material in which a metal-organic structure modified with an organic molecule containing at least one non-covalent electron pair is uniformly attached to the top of a carbon nanotube.

[0065] In addition, an ion sensor utilizing such an ion sensor component may include a working electrode in which the ion sensor component is uniformly coated on the top of a glass carbon electrode, and can detect electrical signals using this working electrode. More specifically, the ion sensor can provide enhanced sensing characteristics for multiple or single types of cations through chemical interactions between trace amounts of cationic components contained in an aqueous solution and the composite material.

[0066] As previously explained, an organic molecule having at least one non-covalent electron pair may include a single bond and / or double bond to at least one element among oxygen (O), sulfur (S), nitrogen (N), and phosphorus (P). Additionally, the non-covalent electron pair of the organic molecule may form a complex with a cation through an acid-base chemical reaction. Furthermore, the molecular weight (M) of the organic molecule containing the non-covalent electron pair w ) may be included in the range of 10 to 10,000 g / mol.

[0067] Meanwhile, the metal-organic framework may contain pores of a certain size through chemical bonding between metal ions and organic ligands. In this case, the pore size may be in the range of 0.01 nm to 500 nm. Additionally, the specific surface area of ​​the metal-organic framework is 100 m² 2 / g to 5,000 m 2It may be included in the range of / g, and the size of the metal-organic framework may be included in the diameter range of 1 nm to 100 μm. In addition, the organic ligand of the metal-organic framework may include at least one functional group among carboxylic acid (-COOH), amine (-NH2), and hydroxyl (-OH) groups.

[0068] In this case, an organic molecule containing a non-covalent electron pair can chemically react with the functional groups of the organic ligand constituting the metal-organic framework to form a modified metal-organic framework. The modified metal-organic framework can be uniformly bound to the surface of a one-dimensional carbon nanotube to form a carbon nanotube-based composite material in which the modified metal-organic framework is uniformly bound. Here, the carbon nanotube may include carbon nanotubes exhibiting metallic properties and / or carbon nanotubes exhibiting semiconductor properties. Additionally, the carbon nanotube may include a single-wall to multi-wall structure. Meanwhile, the carbon nanotube may include at least one of a carboxylic acid (-COOH) and a hydroxyl (-OH) group on its surface.

[0069] Carbon nanotube-based composite materials bound to modified metal-organic frameworks can be composited through chemical reactions between non-covalent electron pairs and cations. Here, the cation is Na + , K + , Li + , Sc 2+ , V 2+ , Ti 2+ , Be 2+ , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , Ra 2+ , Ru 2+ , Mo 2+ , Fe 2+ , Cd 2+ , Cr 2+ , Co2+ , Cu 2+ , Pb 2+ , Mn 2+ , Hg 2+ , Ni 2+ , Pt 2+ , Sn 2+ , Zn 2+ , Ag 2+ , Hf 2+ , Au 2+ , Al 3+ , Fe 3+ , Cr 3+ , Sn 4+ , Ti 4+ , and Mn 4+ It may include at least one of the following. The chemical reaction may include an acid-base reaction. In this case, the chemical reaction may occur within a pH range of 2 to 10 of the solution, and the electrochemical properties of the composite material may change due to this chemical reaction, and an electrochemical ion sensor may be provided by utilizing this change in electrochemical properties. The electrochemical ion sensor may include a working electrode, a platinum counter electrode, and a silver / silver chloride reference electrode. Here, the working electrode may include a glass carbon electrode. The glass carbon electrode of the working electrode may be manufactured in a circular shape, in which case the diameter may be in the range of 1 mm to 20 mm. A modified working electrode may be fabricated by coating a composite material (an ion sensor member including the composite material) on top of the glass carbon electrode of the working electrode, and such a working electrode may be utilized for the electrochemical ion sensor. The ion sensor may include an electrochemical measuring instrument that measures the change in current of the working electrode coated with the composite material according to the application of voltage. The glass carbon electrode of the working electrode coated with the composite material exhibits a change in current due to an oxidation-reduction reaction upon voltage application in a solution containing cations, and through the chemical interaction between the trace amount of cations contained in this solution and the composite material, it becomes possible to detect multiple or single types of cations with enhanced sensitivity.

[0070] FIG. 2 is a flowchart illustrating an example of a method for fabricating an ion sensor according to an embodiment of the present invention. The method for fabricating an ion sensor according to the present embodiment may include the steps of: uniformly growing a metal-organic structure on top of a carbon nanotube through a solvothermal synthesis method (210); chemically modifying the metal-organic structure uniformly bound to the surface of the carbon nanotube using an organic molecule containing at least one non-covalent electron pair (220); preparing a dispersion solution by dispersing a carbon nanotube composite material, in which the metal-organic structure modified by the organic molecule is uniformly bound, in a solvent (230); and fabricating a working electrode coated with the composite material by uniformly coating the dispersion solution onto a glass carbon electrode (240).

[0071] The solvent used in the solvothermal synthesis method in step (210) may include at least one solvent selected from ethanol, methanol, propanol, butanol, isopropyl alcohol (IPA), dimethylformamide (DMF), acetone, acetonitrile, toluene, tetrahydrofuran, 1,2-dichlorobenzene, and water. Additionally, the heat treatment of the solvothermal synthesis method may be performed in a range of 50 °C to 500 °C, and the reaction time of the solvothermal synthesis method may be in a range of 1 hour to 100 hours. Meanwhile, the weight ratio between the metal precursor and the carbon nanotube for forming the metal-organic framework may be in a range of 0.01 to 500.

[0072] In step (220), the organic molecule containing at least one non-covalent electron pair may additionally include a 3,5-bis(trifluoromethyl)benzene functional group which is an electron withdrawing group. Additionally, the reaction temperature for functionalizing the organic molecule containing at least one non-covalent electron pair into the metal-organic framework may be in the range of 25 °C to 200 °C. Additionally, the functionalization of the organic molecule may be achieved by forming a secondary amine (-NH) through a chemical reaction with a primary amine (-NH2) group contained in the organic ligand of the metal-organic framework.

[0073] The solvent for preparing the dispersion solution in step (230) may include at least one solvent selected from ethanol, methanol, propanol, butanol, isopropyl alcohol (IPA), dimethylformamide (DMF), acetone, acetonitrile, toluene, tetrahydrofuran, 1,2-dichlorobenzene, water, and mixtures thereof. At this time, the concentration of the composite material included in the dispersion solution may be in the range of 0.01 mg / mL to 10 mg / mL.

[0074] In step (240), the method of coating the dispersion solution of the composite material onto the glass carbon electrode may include at least one of drop coating, spray coating, and dip coating. At this time, the thickness of the composite material coated on the top of the glass carbon electrode may be in the range of 0.1 nm to 500 μm.

[0075] The fabricated working electrode can be physically connected to an electrochemical measuring instrument to form a measurement system, and the measurement system can measure the current according to the potential difference of the glass carbon electrode coated with the composite material. Through this measurement system, the current generated according to the voltage applied by the differential pulse anode peeling voltage-current measurement method can be measured. Here, the voltage applied through the differential pulse anode peeling voltage-current measurement may be within the range of -2 V to 2 V. In addition, the scan rate of the voltage applied through the differential pulse anode peeling voltage-current measurement may be within the range of 1 mV / sec to 500 mV / sec. In this way, the glass carbon electrode of the working electrode coated with the composite material can generate a current by inducing an oxidation-reduction reaction of multiple or single types of cationic components contained in an aqueous solution through the differential pulse anode peeling voltage-current measurement method. Therefore, multiple types of metal cations contained in an aqueous solution can be simultaneously detected through the glass carbon electrode of the working electrode coated with the composite material.

[0076] As previously explained, various types of metal cations contained in the aqueous solution are Na + , K + , Li + , Sc 2+ , V 2+ , Ti 2+ , Be 2+ , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , Ra 2+ , Ru 2+ , Mo 2+ , Fe 2+ , Cd 2+ , Cr 2+ , Co 2+ , Cu 2+ , Pb 2+ , Mn 2+ , Hg 2+ , Ni 2+ , Pt 2+ , Sn2+ , Zn 2+ , Ag 2+ , Hf 2+ , Au 2+ , Al 3+ , Fe 3+ , Cr 3+ , Sn 4+ , Ti 4+ , and Mn 4+ It may include at least one of the following.

[0077] As described above, according to the embodiments of the present invention, a composite material in which a metal-organic framework modified using organic molecules is uniformly bound to the top of a carbon nanotube can be used as a sensing material for an ion sensor that converts into an electrical signal through chemical interaction with a number of harmful heavy metal cations contained in an aqueous solution. Such an ion sensor can sensitively detect harmful heavy metal cations through an enhanced change in current intensity according to the concentration of cations.

[0078] Example 1: Uniformly growing a metal-organic framework on top of carbon nanotubes via solvothermal synthesis

[0079] In Example 1, zirconium (Zr) was synthesized through a solvothermal synthesis method. 4+ UiO66-NH2(C), a )-based metal-organic framework 48 H 34 N6O 32 A composite material was manufactured by uniformly growing Zr6 on top of carbon nanotubes.

[0080] Specifically, 30 mg of carboxylic acid-functionalized multi-walled carbon nanotubes (MWCNT-COOH) were added to 100 mL of dimethylformamide (DMF), and a dispersion solution was prepared by dispersing the mixture for 2 hours using an ultrasonic injector. Subsequently, 233.04 mg of zirconium chloride (ZrCl4), a precursor of the metal-organic framework, and 181.15 mg of 2-aminoterephthalic acid (NH2-BDC) were added to the dispersion solution, and a mixed solution was prepared by heating at 85 °C for 30 minutes. Then, the mixed solution was stored in an autoclave, heated at 120 °C for 24 hours using a furnace, and a precipitate was obtained by centrifugation. Next, the above precipitate is washed with dimethylformamide to remove residues, and the remaining solvent is substituted with acetone three times, and then dried under vacuum at 60°C for 18 hours to obtain the product. The product is evenly ground using a mortar and pestle to obtain carbon nanotube (MWCNT-UiO66-NH2) powder with metal-organic frameworks bound thereto, having fine-scale particles.

[0081] Figure 3 is a photograph of a carbon nanotube with a metal-organic framework uniformly bonded thereto, fabricated according to Example 1 of the present invention. In the photograph of Figure 3, the carbon nanotube with the metal-organic framework bonded thereto appears as a black powder.

[0082] Figure 4 is a scanning electron microscope (SEM) image of a carbon nanotube with a metal-organic framework attached, fabricated according to Example 1 of the present invention. It can be observed that the metal-organic framework has grown on the top of the carbon nanotube through solvothermal synthesis, and that polyhedral crystals of the metal-organic framework, having an average diameter of 70 nm, are uniformly distributed on the top of the carbon nanotube.

[0083] Example 2: A metal-organic framework uniformly bound to the top of a carbon nanotube is chemically modified using an organic molecule containing at least one non-covalent electron pair.

[0084] In Example 2, the metal-organic framework attached to the top of the carbon nanotube prepared according to Example 1 is chemically modified through a post-processing step by utilizing a thiourea (TU) functional group containing a sulfur (S) atom or a squaramide (SQ) functional group containing an oxygen (O) atom. At this time, a chemical reaction is induced by utilizing the said organic molecule on the amine group of NH2-BDC used as a ligand of the metal-organic framework.

[0085] First, a composite material (MWCNT-UiO66-TU) is prepared in which a ligand of a metal-organic framework attached to the top of a carbon nanotube is chemically bonded to an organic molecule containing a sulfur (S) atom. Specifically, to prepare the composite material, 60 mg of carbon nanotubes attached to a metal-organic framework prepared according to Example 1 is added to 10 mL of dichloromethane (DCM) and sonicated for 2 hours to prepare a dispersion solution. Subsequently, 194.84 mg of 3,5-bis(trifluoromethyl)phenyl isothiocyanate, a precursor of an organic molecule containing a sulfur (S) atom, is added to the dispersion solution, and a nucleophilic addition reaction is induced by refluxing at 50 °C for 72 hours. After the reaction is complete, a precipitate is obtained from the solution by centrifugation, and the precipitate is washed with dichloromethane to remove residues. Next, after centrifugation, the precipitate is dried under vacuum at 60°C for 12 hours to obtain carbon nanotubes (MWCNT-UiO66-TU) bound to a metal-organic framework modified with an organic molecule containing sulfur (S) atoms.

[0086] Secondly, a composite material (MWCNT-UiO66-SQ) is prepared in which a ligand of a metal-organic framework attached to the top of a carbon nanotube is chemically bonded to an organic molecule containing an oxygen (O) atom. Specifically, to prepare the composite material, 60 mg of carbon nanotubes attached to a metal-organic framework prepared according to Example 1 is added to 10 mL of methanol, and a dispersion solution is prepared by sonication for 2 hours. Subsequently, 243.7 mg of 3-((3,5-bis(trifluoromethyl)phenyl)amino)-4-methoxycyclobut-3-ene-1,2-dione, a precursor of an organic molecule containing an oxygen (O) atom, is added to the dispersion solution, and a nucleophilic substitution reaction is induced by refluxing at 70 °C for 72 hours. The solution from which the reaction is completed is centrifuged to obtain a precipitate, and the precipitate is washed with methanol to remove residue. Subsequently, the precipitate after centrifugation is dried under vacuum at 60°C for 12 hours to obtain carbon nanotubes (MWCNT-UiO66-SQ) bound to a metal-organic framework modified with an organic molecule containing an oxygen (O) atom.

[0087] FIG. 5 is a photograph of a carbon nanotube (MWCNT-UiO66-TU) bonded to a metal-organic framework modified with an organic molecule containing sulfur (S) atoms and a carbon nanotube (MWCNT-UiO66-SQ) bonded to a metal-organic framework modified with an organic molecule containing oxygen (O) atoms, fabricated according to Example 2 of the present invention. In the photograph of FIG. 5, the composite material appears in the form of a black powder.

[0088] Figure 6 is a scanning electron microscope (SEM) image of a carbon nanotube (MWCNT-UiO66-TU) bound with a metal-organic framework modified with an organic molecule containing sulfur (S) atoms, fabricated according to Example 2 of the present invention. In the image of Figure 6, it can be seen that the metal-organic framework remains stable on the top of the carbon nanotube even after chemically modifying the organic molecule containing sulfur (S) atoms through a post-processing step.

[0089] Figure 7 is a scanning electron microscope (SEM) image of a carbon nanotube (MWCNT-UiO66-SQ) bound with a metal-organic framework modified with an organic molecule containing an oxygen (O) atom, fabricated according to Example 2 of the present invention. In the image of Figure 7, it can be seen that the metal-organic framework remains stable on the top of the carbon nanotube even after chemically modifying the organic molecule containing an oxygen (O) atom through a post-processing step.

[0090] Figure 8 is an X-ray diffraction pattern to determine the crystallinity maintained even after the metal-organic framework was attached to the top of the carbon nanotube, and to determine that the crystallinity was stably maintained even after chemical modification through a post-processing step. By confirming that the X-ray diffraction pattern of the metal-organic framework matches the X-ray diffraction pattern of the carbon nanotube (MWCNT-UiO66-NH2) to which the metal-organic framework was attached according to Example 1, it can be confirmed that the metal-organic framework was stably attached to the carbon nanotube while maintaining its crystallinity. Subsequently, it can be observed that the crystallinity of the carbon nanotube to which the metal-organic framework was attached was stably maintained even after chemical modification through a post-processing step.

[0091] Figure 9 is a Fourier transform infrared (FT-IR) graph to elucidate the functionalization through nucleophilic reactions of organic molecules containing sulfur (S) or oxygen (O) atoms and amine groups included in the ligands of metal-organic frameworks. In carbon nanotubes bound to metal-organic frameworks, the NH2 vibration of the amine group included in the ligands of the metal-organic framework is 3474 cm⁻¹. -1 and 3365 cm -1 It can be confirmed that this appears in... After organic molecules containing sulfur (S) or oxygen (O) atoms are functionalized through a post-processing step, the intensity of the NH2 vibration peak decreases, and in carbon nanotubes bound to metal-organic frameworks modified with organic molecules containing oxygen (O) atoms, it is 1793 cm⁻¹. -1 It can be confirmed that a peak corresponding to the ring breathing mode of squaramide appears. Through the change in intensity of the above NH2 vibration peak and the generation of the ring breathing mode peak, it can be confirmed that a composite material was prepared in which an organic molecule containing sulfur (S) or oxygen (O) atoms is functionalized in the amine group of a metal-organic framework attached to the top of a carbon nanotube.

[0092] Experimental Example 1: A carbon nanotube composite material uniformly bound with a metal-organic framework modified with an organic molecule containing sulfur (S) or oxygen (O) atoms, prepared according to Example 2, was dispersed in a solvent to prepare a dispersion solution.

[0093] In Experimental Example 1, a dispersion solution is prepared by dispersing in ethanol a carbon nanotube composite material uniformly bound with a metal-organic framework modified with an organic molecule containing sulfur (S) or oxygen (O) atoms, prepared according to Example 2 above. Specifically, to prepare the dispersion solution, 2 mg of the composite material is added to 1 mL of ethanol. Then, a 2 mg / mL composite material dispersion solution is prepared by dispersing for 1 hour using an ultrasonic sprayer.

[0094] FIG. 10 is a photograph of a carbon nanotube composite dispersion solution bound with a metal-organic framework modified with an organic molecule containing sulfur (S) or oxygen (O) atoms, prepared according to Experimental Example 1 of the present invention. In the photograph of FIG. 10, it can be seen that the composite material is uniformly dispersed in ethanol.

[0095] Experimental Example 2: After uniformly coating the dispersion solution prepared according to Experimental Example 1 onto a glassy carbon electrode, the metal cation sensing characteristics were evaluated.

[0096] In Experimental Example 2, a working electrode used for electrochemical analysis is fabricated by drop-coating a composite material dispersion solution prepared according to Experimental Example 1 onto a glassy carbon electrode (GCE), and metal cation sensing characteristics are evaluated using this.

[0097] In order to uniformly coat the dispersion solution prepared in Experimental Example 1 above onto the glass carbon electrode, the surface of the glass carbon electrode is polished using an aluminum oxide polishing slurry. Then, 2 μL of the dispersion solution is uniformly applied and dried under vacuum to evaporate the solvent. The above coating process is repeated two more times to produce a working electrode coated with a carbon nanotube composite material to which a metal-organic framework modified with an organic molecule containing sulfur (S) or oxygen (O) atoms is bonded.

[0098] Next, the electrochemical metal cation sensing characteristics are evaluated using the working electrode coated with the aforementioned composite material. The evaluation of electrochemical cation sensing characteristics is performed using a potentiostat connected to a 3-electrode system. The 3-electrode system consists of a working electrode where the oxidation-reduction reaction of the substance to be measured takes place, a reference electrode used for measuring reference potential, and a counter electrode where a reaction paired with the reaction occurring at the working electrode takes place. The evaluation of metal cation sensing characteristics is conducted using a differential pulse anode stripping voltage-current measurement method consisting of a deposition step, a stripping step, and a cleaning step. First, in the deposition step, a voltage of -1.0 V is applied for 5 minutes to deposit metal cations on the working electrode. Second. In the stripping step, a voltage from -1.0 V to 0.6 V is scanned at a scan rate of 5 mV per second to measure the change in oxidation current resulting from the desorption of metal cations from the working electrode due to oxidation. Finally, in the washing step, a voltage of 1.0 V is applied for 10 minutes to remove residual metal cations from the working electrode.

[0099] For electrochemical metal cation detection, a pH buffer solution with a pH of 6 and a molarity of 0.1 (M = mg / L) is prepared by adding monopotassium phosphate and disodium phosphate to distilled water, and an electrolyte is prepared by purging with argon gas for 15 minutes to remove dissolved oxygen from the solution. Subsequently, Cd(NO3)2·4H2O, Pb(NO3)2, Cu(NO3)2·3H2O, and HgCl2 are each added to distilled water, and 10 -3 Prepare a solution of molar concentration, and add 37% hydrogen chloride (HCl) to the solution to obtain cadmium (Cd) at pH 2. 2+ ), lead (Pb 2+ ), copper (Cu 2+ ), mercury (Hg 2+ Prepare a metal cation solution containing ).

[0100] Simultaneous metal cation detection using a working electrode coated with the above composite material is performed for cadmium (Cd₂) of 0 μM, 1 μM, 3 μM, 5 μM, 8 μM, and 10 μM, respectively. 2+ ), lead (Pb 2+ ), copper (Cu 2+ ), mercury (Hg 2+ It was measured in an electrolyte environment containing metal cations including ).

[0101] Figure 11 is a photograph of a working electrode coated with a carbon nanotube composite material bound to a metal-organic framework modified with an organic molecule containing sulfur (S) atoms, prepared according to Experimental Example 2. In the photograph of Figure 11, it can be observed that the composite material is uniformly coated on the top of a glass carbon electrode with a diameter of about 3 mm.

[0102] FIG. 12 shows a multi-metal cation (Cd) utilizing a working electrode coated with a carbon nanotube composite material bound to a metal-organic framework modified with an organic molecule containing sulfur (S) atoms, fabricated according to Experimental Example 2. 2+ , Pb2+ , Cu 2+ , Hg 2+ This is a graph evaluating the voltage-current characteristics for ). It can be observed that the oxidation current value increases as the concentration of metal cations increases, and at 10 μM, Cu 2+ It can be confirmed that the oxidation current value for is 83.98 μA, showing the highest selectivity.

[0103] FIG. 13 is a photograph of a working electrode coated with a carbon nanotube composite material bound to a metal-organic framework modified with an organic molecule containing an oxygen (O) atom, prepared according to Experimental Example 2. In the photograph of FIG. 13, it can be observed that the composite material is uniformly coated on the top of a glass carbon electrode with a diameter of about 3 mm.

[0104] FIG. 14 shows a multi-metal cation (Cd) utilizing a working electrode coated with a carbon nanotube composite material bound to a metal-organic framework modified with an organic molecule containing an oxygen (O) atom, fabricated according to Experimental Example 2. 2+ , Pb 2+ , Cu 2+ , Hg 2+ This is a graph evaluating the voltage-current characteristics for ). It can be observed that the oxidation current value increases as the concentration of metal cations increases, and at 10 μM, Cu 2+ It can be confirmed that the oxidation current value for is 121.17 μA, showing the highest selectivity.

[0105] Comparative Example 1: Comparison of single and multiple metal cation sensing characteristics using a working electrode not coated with a composite material

[0106] In Comparative Example 1, to compare the metal cation sensing characteristics of a working electrode coated with a carbon nanotube composite material to which a metal-organic framework modified with an organic molecule containing sulfur (S) or oxygen (O) atoms is bonded, a step of evaluating the sensing characteristics using a working electrode not coated with said composite material is described.

[0107] In Comparative Example 1, a working electrode coated with the composite material prepared in Experimental Example 2 and a working electrode not coated with the composite material are prepared.

[0108] In Comparative Example 1, metal cation sensing characteristics are compared and evaluated under the same conditions as shown in Experimental Example 2 of the present invention.

[0109] Figure 15 is a photograph of a working electrode not coated with the composite material. It can be seen that the top of the glass carbon electrode is exposed on the surface of the working electrode not coated with the composite material.

[0110] FIG. 16 shows a working electrode coated with the composite material and a working electrode not coated with the composite material fabricated in Experimental Example 2 of the present invention, using 10 μM of multi-metal cations (Cd 2+ , Pb 2+ , Cu 2+ , Hg 2+ This is a graph evaluating the voltage-current characteristics for ). As the metal cation sensing characteristics of the working electrode coated with the composite material were higher, it can be confirmed that the sensing characteristics are improved compared to the working electrode not coated with the composite material.

[0111] FIG. 17 shows a cadmium (Cd₂) working electrode prepared according to Experimental Example 2 and Comparative Example 1 of the present invention. 2+ This is a graph evaluating the characteristics of the change in current according to the concentration of metal cations. Compared to a working electrode not coated with the composite material, 8 M cadmium (Cd 2+ A 2.25-fold increase in current value change can be observed only in the working electrode coated with a carbon nanotube composite material to which a metal-organic framework modified with an organic molecule containing an oxygen (O) atom is attached for the cation.

[0112] FIG. 18 shows a copper (Cu) working electrode utilizing the electrode fabricated according to Experimental Example 2 and Comparative Example 1 of the present invention. 2+This is a graph evaluating the characteristics of the change in current according to the concentration of metal cations. Compared to a working electrode not coated with the composite material, 8 M copper (Cu 2+ For ) regarding the cation, changes in current values ​​improved by 1.74 times and 4.47 times can be observed in the working electrode coated with a carbon nanotube composite material bound to a metal-organic framework modified with an organic molecule containing sulfur (S) atoms or oxygen (O) atoms.

[0113] FIG. 19 shows mercury (Hg) using a working electrode prepared according to Experimental Example 2 and Comparative Example 1 of the present invention. 2+ This is a graph evaluating the characteristics of the change in current according to the concentration of metal cations. Compared to a working electrode not coated with the composite material, 8 M mercury (Hg 2+ For ) regarding the cation, changes in current values ​​improved by 1.72 times and 2.85 times, respectively, can be observed in the working electrode coated with a carbon nanotube composite material to which a metal-organic framework modified with an organic molecule containing sulfur (S) or oxygen (O) atoms is attached.

[0114] Although the embodiments have been described above with reference to limited examples and drawings, those skilled in the art can make various modifications and variations from the description above. For example, suitable results can be achieved even if the described techniques are performed in a different order than described, and / or the components of the described system, structure, device, circuit, etc. are combined or assembled in a form different from described, or replaced or substituted by other components or equivalents.

[0115] Therefore, other implementations, other embodiments, and equivalents to the claims also fall within the scope of the claims set forth below.

Claims

1. Composite material in which a metal-organic framework is uniformly bonded to the surface of a carbon nanotube Includes, The above metal-organic framework is a functionalized and modified organic molecule comprising at least one non-covalent electron pair. An ion sensor member characterized by 2. In Paragraph 1, The organic molecule comprising at least one non-covalent electron pair comprises a single bond or a double bond to at least one element among oxygen (O), sulfur (S), nitrogen (N), and phosphorus (P). An ion sensor member characterized by 3. In Paragraph 1, The molecular weight (M) of the organic molecule containing at least one non-covalent electron pair mentioned above w ) is included in the range of 10 to 10,000 g / mol An ion sensor member characterized by 4. In Paragraph 1, The organic molecule comprising at least one non-covalent electron pair further comprises 3,5-bis(trifluoromethyl)benzene as an electron-pulling group as a functional group. An ion sensor member characterized by 5. In Paragraph 1, The organic ligand constituting the metal-organic framework comprises at least one functional group selected from carboxylic acid (-COOH), amine (-NH2), and hydroxyl (-OH) groups. An ion sensor member characterized by 6. In Paragraph 1, The diameter of the above metal-organic framework is included in the range of 1 nm to 100 μm. An ion sensor member characterized by 7. In Paragraph 1, The specific surface area of ​​the above metal-organic framework is 100 m² 2 / g to 5,000 m 2 Things included in the range of / g An ion sensor member characterized by 8. In Paragraph 1, The carbon nanotube above comprises at least one of a carboxylic acid (-COOH) and a hydroxyl (-OH) group on its surface. An ion sensor member characterized by 9. An ion sensor member of any one of claims 1 to 8; and Glass carbon electrode coated with the above-mentioned ion sensor component Includes, Detecting a change in current based on a chemical reaction between a composite material containing the ion sensor member and a cation contained in an aqueous solution, depending on the application of voltage to a glass carbon electrode coated with the ion sensor member. An ion sensor characterized by 10. In Paragraph 9, The cation contained in the above aqueous solution is Na + , K + , Li + , Sc 2+ , V 2+ , Ti 2+ , Be 2+ , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , Ra 2+ , Ru 2+ , Mo 2+ , Fe 2+ , Cd 2+ , Cr 2+ , Co 2+ , Cu 2+ , Pb 2+ , Mn 2+ , Hg 2+ , Ni 2+ , Pt 2+ , Sn 2+ , Zn 2+ , Ag 2+ , Hf 2+ , Au 2+ , Al 3+ , Fe 3+ , Cr 3+ , Sn 4+ , Ti 4+ , and Mn 4+ Includes at least one of An ion sensor characterized by 11. In Paragraph 9, An ion sensor characterized by being capable of simultaneously detecting various types of cations contained in the aqueous solution through the detected current change. 12.(a) A step of growing a metal-organic framework on the surface of a carbon nanotube via solvothermal synthesis; (b) a step of chemically modifying a metal-organic framework bound to the surface of a carbon nanotube using an organic molecule containing at least one non-covalent electron pair; (c) a step of preparing a dispersion solution by dispersing a carbon nanotube-based composite material, to which a metal-organic framework modified using the above organic molecule is bound, in a solvent; (d) a step of uniformly coating the above dispersion solution onto a glass carbon electrode to produce a working electrode coated with the above composite material. A method for manufacturing an ion sensor including 13. In Paragraph 12, The weight ratio between the metal precursor and the carbon nanotube for growing a metal-organic framework on the surface of the carbon nanotube through the above solvothermal synthesis method is included in the range of 0.01 to 500. A method for manufacturing an ion sensor characterized by 14. In Paragraph 12, The solvent used in the above solvothermal synthesis method comprises at least one of ethanol, methanol, propanol, butanol, isopropyl alcohol (IPA), dimethylformamide (DMF), acetone, acetonitrile, toluene, tetrahydrofuran, 1,2-dichlorobenzene, and water. A method for manufacturing an ion sensor characterized by 15. In Paragraph 12, The temperature range of the heat treatment for the above solvothermal synthesis method is included in the range of 50 °C to 500 °C. A method for manufacturing an ion sensor characterized by 16. In Paragraph 12, In step (b) above, The above metal-organic framework is modified by forming a secondary amine (-NH) through a chemical reaction between a primary amine (-NH2) group contained in an organic ligand and a functional group contained in the organic molecule. A method for manufacturing an ion sensor characterized by 17. In Paragraph 12, In step (d) above, The composite material is coated on the top of the glass carbon electrode with a thickness ranging from 0.1 nm to 500 μm. A method for manufacturing an ion sensor characterized by 18. In Paragraph 12, Single and multiple types of cations contained in an aqueous solution are detected by a differential pulse anode peeling voltage and current measurement method using a working electrode coated with the above composite material. A method for manufacturing an ion sensor characterized by 19. In Paragraph 18, A voltage included in the range of -2 V to 2 V is applied to the working electrode through the above differential pulse anode peeling voltage and current measurement. A method for manufacturing an ion sensor characterized by

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