Interference-resistant ph electrode based on confined ionic liquid-mof composite structure and application thereof

Abstract

The application discloses a kind of anti-interference pH electrode based on limited domain ionic liquid-MOF composite structure and application thereof.The electrode includes metal oxide pH electrode body and the SPEEK / MOF@IL composite modification film covering the surface of its metal oxide sensitive layer;The composite modification film takes SPEEK as main body matrix, and takes the metal organic framework material MOF@IL loaded with ionic liquid as functional filler, and the ionic liquid is limitedly loaded in the pore structure of metal organic framework material, which can effectively reduce the diffusion and leakage of ionic liquid in water environment;Ionic liquid forms stable proton conduction network inside the composite film, improves the proton conduction performance of the composite film.The application can effectively reduce the potential drift in complex environment while maintaining the fast response performance of metal oxide pH electrode, improve the long-term stability of the electrode, and can be widely used in pH in-situ detection in complex medium environment.

Description

Technical Field

[0001] This invention relates to the field of electrochemical sensing and functional composite membrane materials, and particularly to an anti-interference pH electrode based on a confined ionic liquid-MOF composite structure and its application. Background Technology

[0002] pH is a crucial parameter in marine environmental monitoring, bio-fermentation, environmental analysis, and chemical process control. Long-term stable in-situ pH monitoring in complex media environments is of great significance for marine chemistry, biochemistry, and environmental science. However, natural water bodies, marine hydrothermal environments, biological systems, and complex chemical systems often contain a large number of redox-active substances, organic pollutants, biomass components, and small-sized anions, which can easily affect the stable detection of pH electrodes.

[0003] Currently, metal oxide pH electrodes are widely used for pH detection in complex environments due to their advantages such as fast response speed, high mechanical strength, resistance to high temperature and pressure, and ease of miniaturization. However, the surface of the metal oxide sensitive layer is susceptible to interference from redox-active substances, organic pollutants, and small-sized anions. These interfering substances can not only adsorb onto the metal oxide surface but may also undergo surface redox reactions with the metal oxide sensitive layer, thereby altering the valence equilibrium and interfacial electrochemical state of the metal oxide surface. This leads to a drift in the electrode surface potential, reducing the accuracy and long-term stability of pH measurements.

[0004] To mitigate the impact of interfering substances in complex media on metal oxide pH electrodes, existing technologies typically employ polymer-modified films on the electrode surface, such as Nafion films, SPEEK films, and ionic liquid composite films, to block redox substances and organic pollutants from contacting the electrode surface. However, while traditional polymer-modified films improve anti-interference performance, they often reduce hydrogen ion transport efficiency, leading to a decrease in electrode response speed. Furthermore, when ionic liquids are directly blended with the polymer matrix, the ionic liquids tend to diffuse into the aqueous environment during long-term use, reducing the number of proton conduction channels within the composite film and decreasing its proton conductivity. Ultimately, this results in prolonged electrode response time, reduced response speed, and decreased long-term stability.

[0005] Therefore, developing a metal oxide pH electrode modified membrane that can effectively block interference from redox-active substances, organic pollutants, and biomass components while maintaining excellent proton conduction performance, rapid response capability, and long-term stability is of great significance for the stable detection of pH in complex media environments. Summary of the Invention

[0006] The purpose of this invention is to address the problem that existing metal oxide pH electrodes are easily affected by redox-active substances, organic pollutants, and biomass components in complex media environments, leading to potential drift, response instability, and decreased long-term stability. This invention provides an anti-interference metal oxide pH electrode based on a metal-organic framework (MOF) confined ionic liquid composite structure, its preparation method, and its application.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] This invention provides an anti-interference pH electrode based on a confined ionic liquid-MOF composite structure. The pH electrode includes a metal oxide pH electrode body and a SPEEK / MOF@IL composite modification film covering the surface of its metal oxide sensitive layer. The composite modification film uses SPEEK as the main matrix and MOF@IL, a metal-organic framework material loaded with ionic liquid, as the functional filler. The ionic liquid is confined and loaded in the pore structure of the metal-organic framework material. The SPEEK / MOF@IL composite modification film completely covers the metal oxide sensitive layer on the surface of the pH electrode body. The metal-organic framework material is UiO-66-4F.

[0009] In this invention, the SPEEK matrix has dense and tortuous ion transport channels, which can effectively block the penetration of redox reactive substances, organic pollutants, and small-sized anions; the fluorinated pore structure of UiO-66-4F can enhance the hydrophobicity of the composite membrane and improve the interfacial compatibility with SPEEK and hydrophobic ionic liquids, while the confinement effect of MOF channels can inhibit the diffusion and leakage of ionic liquids into the aqueous environment; the ionic liquid can construct a continuous proton conduction network inside the composite membrane, improving the proton conduction capacity of the composite membrane, thereby maintaining excellent anti-interference performance while maintaining the rapid and stable pH response performance of the electrode.

[0010] According to a preferred embodiment of the present invention, the ionic liquid is TEA-PS•HSO4, [HOEtMIM][Cl], or [C8mim] + [C1C1N] - ].

[0011] According to a preferred embodiment of the present invention, the metal oxide pH electrode body is Ru / RuO. x pH electrode or Ir / IrO x pH electrode.

[0012] According to a preferred embodiment of the present invention, in the SPEEK / MOF@IL composite modified film, the mass ratio of SPEEK, metal-organic framework material and ionic liquid is (0.5-2):(0.5-2):(0.5-2).

[0013] The present invention also provides a method for preparing the above-mentioned anti-interference pH electrode, which includes the following steps:

[0014] 1) Prepare a sulfonated polyether ether ketone solution with a mass fraction of 5-15 wt%;

[0015] 2) Dissolve the ionic liquid in alcohol to form an ionic liquid alcohol solution; then add metal-organic framework material powder and stir continuously for 4-6 h, so that the ionic liquid enters the pore structure of the metal-organic framework material under the capillary wetting and pore confinement effects;

[0016] 3) Place the mixture obtained in step 2) in a vacuum oven and evaporate the solvent at 60-80°C to obtain MOF@IL powder loaded with ionic liquid;

[0017] 4) Add the MOF@IL powder obtained in step 3) to the sulfonated polyether ether ketone solution and stir to mix, to obtain the SPEEK / MOF@IL composite modified solution;

[0018] 5) The SPEEK / MOF@IL composite modification solution was coated onto the surface of the sensitive layer of the metal oxide pH electrode and dried to obtain the SPEEK / MOF@IL composite modified membrane pH electrode.

[0019] According to a preferred embodiment of the present invention, in step 5), the covering method is dipping or immersion, and the covering is repeated 2 to 5 times, with drying performed after each covering. The drying method in step 5) is vacuum drying.

[0020] This invention also provides the application of the anti-interference pH electrode in in-situ pH detection in an aqueous environment. Preferably, the aqueous environment is a natural water body, a biological system feed solution, or a chemical system feed solution. Preferably, the aqueous environment contains redox-active substances, organic pollutants, or biomass components.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The present invention constructs a SPEEK / MOF@IL composite modified membrane. The composite modified membrane uses SPEEK as the main matrix and MOF@IL (i.e., confined ionic liquid-MOF composite structure) loaded with ionic liquid as the functional filler. The ionic liquid is confined and loaded in the pore structure of the metal-organic framework material. The confinement effect of the metal-organic framework material on the ionic liquid can effectively inhibit the diffusion and leakage of the ionic liquid and improve the stability of the composite membrane during long-term use. The ionic liquid forms a stable proton conduction network inside the composite membrane, which improves the proton conduction performance of the composite membrane and avoids the problem of decreased response speed caused by traditional polymer modified membranes. The anti-interference pH electrode based on the confined ionic liquid-MOF composite structure obtained in the present invention can effectively reduce the interference of redox active substances, organic pollutants and biomass components on the metal oxide pH electrode, reduce electrode potential drift and improve detection stability in complex environments.

[0023] (2) By comparing the internal morphology of the SPEEK / MOF@IL composite membrane, this invention found that the SPEEK matrix has narrower and more tortuous ion transport channels, resulting in a denser composite semi-permeable membrane structure. This effectively reduces the penetration of redox-active substances, organic pollutants, biomass components, and small-sized anions into the metal oxide sensitive layer. Simultaneously, the confinement and stabilization effect of the metal-organic framework material on the ionic liquid further enhances the stability of the composite membrane in long-term complex aquatic environments. Therefore, the SPEEK / MOF@IL composite modified membrane constructed in this invention possesses excellent anti-interference performance, rapid response performance, and long-term stability, and can be widely applied in fields such as marine environmental monitoring, biological system detection, complex chemical process analysis, and long-term in-situ pH detection.

[0024] (3) The preparation method of the present invention is simple, the composite membrane structure is stable, and it is suitable for long-term in-situ pH detection in marine environmental monitoring, biological system detection, environmental analysis and complex chemical systems. Attached Figure Description

[0025] Figure 1 The SPEEK / MOF@IL modified RuO obtained in Example 1 x SEM image of electrode surface;

[0026] Figure 2 Here is a SEM image of the SPEEK-modified electrode surface obtained in Comparative Example 4;

[0027] Figure 3 The SPEEK / IL modified RuO obtained in Example 5 x SEM image of electrode surface;

[0028] Figure 4The potential response diagrams of the electrodes obtained in Comparative Example 4 and Example 1 to changes in solution pH are shown, where (a) is Comparative Example 4 and (b) is Example 1.

[0029] Figure 5 The stability potential diagram of the electrode obtained in Example 1 under different interfering substances;

[0030] Figure 6 This is a photograph of the electrode obtained in Example 1 being monitored in a high-concentration algal solution;

[0031] Figure 7 This is a potential graph of the electrode obtained in Example 1 monitored in a high-concentration algal solution;

[0032] Figure 8 The potential response of the electrode obtained in Example 6 to changes in solution pH is shown in the graph.

[0033] Figure 9 The potential response of the electrode obtained in Example 7 to changes in solution pH is shown in the graph.

[0034] Figure 10 This is a potential response diagram of the electrode obtained in Example 8 to changes in solution pH. Detailed Implementation

[0035] The following examples provide those skilled in the art with guidance on how to manufacture and evaluate the invention. These examples are merely illustrative of the present disclosure and do not limit its scope. While every effort has been made to ensure accuracy regarding numerical values ​​(e.g., quantities, temperatures, etc.), some errors and deviations should be considered. Unless otherwise stated, temperatures are in °C or at ambient temperature, and pressures are at or near atmospheric pressure.

[0036] The reagents and raw materials used in the examples are all commercially available. The preparation of SPEEK (sulfonated polyether ether ketone) particles and metal-organic framework materials (such as UiO-66-4F) can be referred to existing literature or techniques. SPEEK particles and the corresponding metal-organic framework materials in the examples can also be purchased commercially.

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

[0038] Example 1

[0039] 1) Add polyetheretherketone particles to concentrated sulfuric acid with a mass fraction of 98% and stir continuously in an ice-water bath until completely dissolved; then heat to 50°C under a nitrogen atmosphere to carry out a sulfonation reaction for 4 hours.

[0040] 2) Slowly pour the obtained polymer solution into an ice-water mixture to terminate the reaction, collect the precipitated particles, and wash them repeatedly with deionized water until the pH of the washing solution is 6-7; then place the particles in a 70℃ oven to dry for 24 h to obtain SPEEK particles;

[0041] 3) Add the obtained SPEEK particles to DMF and stir to dissolve, preparing a SPEEK solution with a mass fraction of 10 wt%;

[0042] 4) Add tetrafluoroterephthalic acid and zirconium oxynitrate hydrate in a molar ratio of 1:1 to concentrated acetic acid and heat and stir at 50°C to dissolve them, forming a homogeneous precursor solution; transfer the two solutions obtained to a reaction vessel and carry out a solvothermal reaction at 50°C for 5 min.

[0043] 5) After the reaction is complete, allow the mixture to cool naturally to room temperature, centrifuge to collect the white precipitate, and wash it three times with DMF and ethanol alternately. Then, place the product in an 80℃ vacuum oven to dry for 12 h to obtain UiO-66-4F powder.

[0044] 6) Dissolve the ionic liquid TEA-PS·HSO4 in ethanol to form an ionic liquid alcohol solution; then add UiO-66-4F powder and stir continuously for 6 h, so that the ionic liquid enters the pore structure of UiO-66-4F under the action of capillary wetting and pore confinement; the mass ratio of UiO-66-4F to ionic liquid TEA-PS·HSO4 is 1:1;

[0045] 7) Place the mixture obtained in step 6) in a vacuum oven at 70°C to evaporate the solvent and obtain MOF@IL powder loaded with ionic liquid;

[0046] 8) Add the MOF@IL powder obtained in step 7) to the SPEEK solution obtained in step 3) and stir to mix to obtain SPEEK / MOF@IL composite modified solution, wherein the mass ratio of SPEEK, UiO-66-4F and ionic liquid is 1:1:1;

[0047] 9) Use a ruthenium oxide pH electrode (RuO2). x The metal electrode was immersed in the SPEEK / MOF@IL composite modification solution for 5 seconds for coating, and then dried under vacuum conditions. The coating was repeated 3 times to finally obtain the SPEEK / MOF@IL modified ruthenium oxide pH electrode.

[0048] from Figure 1 It can be seen that the dip-coating method has been used in RuO xA complete and uniform SPEEK / MOF@IL composite film was formed on the metal pH electrode, completely covering the sensitive layer of the pH electrode. The surface of the composite film was intact, without obvious defects or damage. MOF@IL showed good dispersion and compatibility in SPEEK. SEM results indicated that the introduction of UiO-66-4F and the confined ionic liquid resulted in a continuous and dense network microstructure on the surface of the SPEEK / MOF@IL composite film. This structure enhances the structural stability of the composite film, improves the continuity of the proton transport path, and reduces the penetration of interfering substances into the ruthenium oxide sensitive layer in complex environments, thereby improving the electrode's anti-interference performance and long-term stability.

[0049] from Figure 4 As can be seen in (b), the RuO modified by SPEEK / MOF@IL... x Metal electrodes still exhibit a rapid and accurate response to changes in the pH of the external solution, compared to... Figure 4 In (a) of the image, the SPEEK film-modified electrode, and the RuO2 modified with SPEEK / MOF@IL. x The metal electrode exhibits better stability and faster response in a buffer solution at pH 2.00, indicating that MOF@IL significantly enhances the proton conductivity and stability of SPEEK.

[0050] from Figure 5 It can be seen that RuO modified with SPEEK / MOF@IL x The metal electrode immersion concentration is 10 -3 In mol / L buffer solutions of KI, KBr, NaF, Na2S, ascorbic acid, and fulvic acid, the electrode can accurately measure the pH value of the solution within a few seconds, and the electrode potential remains stable within 5 minutes, indicating that the modified electrode is not affected by interfering substances in the solution and can still work normally.

[0051] Figure 6 RuO modified by SPEEK / MOF@IL x Images of metal electrodes monitored in high-concentration algal solutions. The algal solution system contains a large amount of organic matter and biomass, which poses a severe challenge to the stability of the electrodes. Figure 7 The electrode potential data obtained during the detection process show an overall stable trend, indicating that interfering substances in the solution system did not affect the stability of the modified electrode. During monitoring, the potential decreased under illumination, because the algae's net photosynthesis absorbs CO2 and releases oxygen, leading to an increase in the solution's pH. Conversely, under darkness, the algae only respire, releasing CO2 and causing a decrease in pH, thus the potential either increased or remained stable. This phenomenon indicates that the SPEEK / MOF@IL-modified RuO2...x Metal electrodes, while possessing anti-interference capabilities, can still accurately measure the pH of the environment.

[0052] In summary, this invention constructs a SPEEK / MOF@IL composite modified film on the surface of the ruthenium oxide pH electrode sensitive layer, using SPEEK as the main matrix and UiO-66-4F (MOF@IL) loaded with ionic liquid as the functional filler. This improves the proton conductivity and long-term stability of the composite film while maintaining the excellent anti-interference performance of SPEEK.

[0053] Example 2

[0054] 1) Add polyetheretherketone particles to concentrated sulfuric acid with a mass fraction of 98% and stir continuously in an ice-water bath until completely dissolved; then heat to 50°C under a nitrogen atmosphere to carry out a sulfonation reaction for 4 hours.

[0055] 2) Slowly pour the obtained polymer solution into an ice-water mixture to terminate the reaction, collect the precipitated particles, and wash them repeatedly with deionized water until the pH of the washing solution is 6-7; then place the particles in a 70℃ oven to dry for 24 h to obtain SPEEK particles;

[0056] 3) Add the obtained SPEEK particles to DMF and stir to dissolve, preparing a SPEEK solution with a mass fraction of 5 wt%;

[0057] 4) Add tetrafluoroterephthalic acid and zirconium oxynitrate hydrate in a molar ratio of 1:1 to concentrated acetic acid and heat and stir at 50°C to dissolve them, forming a homogeneous precursor solution; transfer the two solutions obtained to a reaction vessel and carry out a solvothermal reaction at 50°C for 5 min.

[0058] 5) After the reaction is complete, allow the mixture to cool naturally to room temperature, centrifuge to collect the white precipitate, and wash it three times with DMF and ethanol alternately. Then, place the product in an 80℃ vacuum oven to dry for 12 h to obtain UiO-66-4F powder.

[0059] 6) Dissolve the ionic liquid TEA-PS·HSO4 in ethanol to form an ionic liquid alcohol solution; then add UiO-66-4F powder and stir continuously for 6 h, so that the ionic liquid enters the pore structure of UiO-66-4F under the capillary wetting and pore confinement effects.

[0060] 7) Place the mixture obtained in step 6) in a vacuum oven at 70°C to evaporate the solvent and obtain MOF@IL powder loaded with ionic liquid;

[0061] 8) Add the MOF@IL powder obtained in step 7) to the SPEEK solution obtained in step 3) and stir to mix to obtain SPEEK / MOF@IL composite modified solution, wherein the mass ratio of SPEEK, UiO-66-4F and ionic liquid is 1:0.5:0.5;

[0062] 9) The ruthenium oxide pH electrode was dipped into the SPEEK / MOF@IL composite modification solution for 5 s for coating, and then dried under vacuum conditions. The coating was repeated 3 times to finally obtain the SPEEK / MOF@IL modified ruthenium oxide pH electrode.

[0063] Example 3

[0064] 1) Add polyetheretherketone particles to concentrated sulfuric acid with a mass fraction of 98% and stir continuously in an ice-water bath until completely dissolved; then heat to 50°C under a nitrogen atmosphere to carry out a sulfonation reaction for 4 hours.

[0065] 2) Slowly pour the obtained polymer solution into an ice-water mixture to terminate the reaction, collect the precipitated particles, and wash them repeatedly with deionized water until the pH of the washing solution is 6-7; then place the particles in a 70℃ oven to dry for 24 h to obtain SPEEK particles;

[0066] 3) Add the obtained SPEEK particles to DMF and stir to dissolve, preparing a SPEEK solution with a mass fraction of 10 wt%;

[0067] 4) Add tetrafluoroterephthalic acid and zirconium oxynitrate hydrate in a molar ratio of 1:1 to concentrated acetic acid and heat and stir at 50°C to dissolve them, forming a homogeneous precursor solution; transfer the two solutions obtained to a reaction vessel and carry out a solvothermal reaction at 50°C for 5 min.

[0068] 5) After the reaction is complete, allow the mixture to cool naturally to room temperature, centrifuge to collect the white precipitate, and wash it three times with DMF and ethanol alternately. Then, place the product in an 80℃ vacuum oven to dry for 12 h to obtain UiO-66-4F powder.

[0069] 6) Dissolve the ionic liquid TEA-PS·HSO4 in ethanol to form an ionic liquid alcohol solution; then add UiO-66-4F powder and stir continuously for 6 h, so that the ionic liquid enters the pore structure of UiO-66-4F under the capillary wetting and pore confinement effects.

[0070] 7) Place the mixture obtained in step 6) in a vacuum oven at 70°C to evaporate the solvent and obtain MOF@IL powder loaded with ionic liquid;

[0071] 8) Add the MOF@IL powder obtained in step 7) to the SPEEK solution obtained in step 3) and stir to mix to obtain SPEEK / MOF@IL composite modified solution, wherein the mass ratio of SPEEK, UiO-66-4F and ionic liquid is 1:0.082:0.028;

[0072] 9) The ruthenium oxide pH electrode was dipped into the SPEEK / MOF@IL composite modification solution for 5 s for coating, and then dried under vacuum conditions. The coating was repeated 3 times to finally obtain the SPEEK / MOF@IL modified ruthenium oxide pH electrode.

[0073] Comparative Example 4

[0074] 1) Add polyetheretherketone particles to concentrated sulfuric acid with a mass fraction of 98% and stir continuously in an ice-water bath until completely dissolved; then heat to 50°C under a nitrogen atmosphere to carry out a sulfonation reaction for 4 hours.

[0075] 2) Slowly pour the obtained polymer solution into an ice-water mixture to terminate the reaction, collect the precipitated particles, and wash them repeatedly with deionized water until the pH of the washing solution is 6-7; then place the particles in a 70℃ oven to dry for 24 h to obtain SPEEK particles;

[0076] 3) Add the obtained SPEEK particles to DMF and stir to dissolve, preparing a SPEEK solution with a mass fraction of 10 wt%;

[0077] 4) Immerse the ruthenium oxide pH electrode in the SPEEK / IL composite modification solution for 5 seconds for coating, remove it and dry it under vacuum conditions; repeat the coating 3 times to finally obtain the SPEEK modified ruthenium oxide pH electrode.

[0078] Figure 4 As can be seen in (a), the SPEEK-modified RuO x The metal pH electrode can achieve continuous response to buffer solutions of different pH values, but a significant potential drift phenomenon was observed in the pH 2.00 buffer solution, and a certain response hysteresis effect was also exhibited during the switching between different pH solutions. In particular, when switching from a strongly acidic environment to neutral and alkaline environments, the time required for the electrode to reach a stable potential increased significantly, indicating that while the dense SPEEK film improves the anti-interference performance, it also increases the proton transport resistance, thus affecting the dynamic response performance of the electrode.

[0079] In comparison, Figure 4 (b) shows the SPEEK / MOF@IL modification of RuO xThe metal pH electrode exhibits a rapid and stable potential response across the entire pH range of 2.00–12.00. Compared to the SPEEK-modified electrode, its potential drift in pH 2.00 buffer solution is significantly reduced, the time required to reach steady-state potential when switching between different pH conditions is significantly shortened, the response process is more stable and continuous, and the hysteresis effect is significantly reduced.

[0080] This result demonstrates that the introduction of MOF@IL effectively improves the proton transport performance within the SPEEK membrane. The UiO-66-4F-loaded ionic liquid forms a continuous proton conduction network within the composite membrane, providing a more convenient transport channel for proton migration and thus reducing the hindrance effect of the dense SPEEK structure on proton diffusion. Simultaneously, the confinement effect of UiO-66-4F on the ionic liquid helps maintain a uniform distribution of the conductive components within the composite membrane, enabling the electrode to maintain good response consistency and reversibility over a wide pH range.

[0081] Combination Figure 3 The SEM results shown suggest that the continuous network structure formed by the SPEEK / MOF@IL composite film is not only conducive to building a stable proton transport channel, but also maintains a fast response speed while ensuring anti-interference capability. This effectively overcomes the problem of "enhanced anti-interference but slower response" of traditional SPEEK modified films, and achieves a synergistic improvement in anti-interference performance and response performance.

[0082] Comparative Example 5

[0083] 1) Add polyetheretherketone particles to concentrated sulfuric acid with a mass fraction of 98% and stir continuously in an ice-water bath until completely dissolved; then heat to 50°C under a nitrogen atmosphere to carry out a sulfonation reaction for 4 hours.

[0084] 2) Slowly pour the obtained polymer solution into an ice-water mixture to terminate the reaction, collect the precipitated particles, and wash them repeatedly with deionized water until the pH of the washing solution is 6-7; then place the particles in a 70℃ oven to dry for 24 h to obtain SPEEK particles;

[0085] 3) Add the obtained SPEEK particles to DMF and stir to dissolve, preparing a SPEEK solution with a mass fraction of 10 wt%;

[0086] 4) Dissolve the ionic liquid TEA-PS·HSO4 in the 10 wt% SPEEK solution obtained in step 3) and stir continuously for 4 h to obtain the SPEEK / IL modified solution; wherein the mass ratio of SPEEK to ionic liquid is 1:1.

[0087] 5) Immerse the ruthenium oxide pH electrode in the SPEEK / IL composite modification solution for 5 seconds for coating, remove it and dry it under vacuum conditions; repeat the coating 3 times to finally obtain the SPEEK / IL modified ruthenium oxide pH electrode.

[0088] from Figure 3 It can be seen that the SPEEK / IL modification solution has been applied to RuO2 using the dip-coating method. x A complete and uniform SPEEK / IL composite film was formed on the metal pH electrode, completely covering the sensitive layer of the pH electrode. The surface of the composite film was intact, without obvious defects or damage. Figure 1 Compared to the SPEEK / MOF@IL composite membrane, both the SPEEK membrane and the SPEEK / IL composite membrane exhibit relatively smooth and flat morphologies, with no obvious network cross-linking structure observed. The pure SPEEK membrane primarily displays a uniform and dense polymer surface, while the SPEEK / IL composite membrane, due to the plasticizing effect of the ionic liquid, shows further improved surface smoothness, but still fails to form a distinct continuous network structure. In contrast, the introduction of UiO-66-4F-loaded ionic liquid resulted in a continuous and dense network microstructure on the surface of the SPEEK / MOF@IL composite membrane. This phenomenon indicates that the introduction of UiO-66-4F not only altered the arrangement of SPEEK molecular chains during film formation but also promoted the reconstruction of the internal microstructure of the composite membrane. Due to its abundant pore structure and high specific surface area, UiO-66-4F can act as a structural node within the composite membrane, forming stable interfacial interactions with the SPEEK molecular chains and the confined ionic liquid, thereby inducing the formation of a continuous three-dimensional network structure. Furthermore, the fluorinated organic ligands in UiO-66-4F exhibit good interfacial compatibility with SPEEK molecular chains and hydrophobic ionic liquids, which is beneficial for improving the dispersion uniformity of MOFs in the polymer matrix and reducing the generation of internal defects in the composite membrane. The formed network structure not only enhances the mechanical and structural stability of the composite membrane but also constructs a more continuous proton transport path, improving the proton conductivity within the composite membrane. Simultaneously, this dense network structure increases the transport path length required for interfering substances to penetrate the membrane layer, increasing diffusion resistance and effectively reducing the permeation rate of redox-active substances, organic pollutants, biomass components, and small-sized anions into the RuOx sensitive layer. These structural features provide an important structural basis for the excellent anti-interference performance, rapid response capability, and long-term stability exhibited by the subsequent electrodes.

[0089] Example 6

[0090] 1) Add polyetheretherketone particles to concentrated sulfuric acid with a mass fraction of 98% and stir continuously in an ice-water bath until completely dissolved; then heat to 50°C under a nitrogen atmosphere to carry out a sulfonation reaction for 4 hours.

[0091] 2) Slowly pour the obtained polymer solution into an ice-water mixture to terminate the reaction, collect the precipitated particles, and wash them repeatedly with deionized water until the pH of the washing solution is 6-7; then place the particles in a 70℃ oven to dry for 24 h to obtain SPEEK particles;

[0092] 3) Add the obtained SPEEK particles to DMF and stir to dissolve, preparing a SPEEK solution with a mass fraction of 10 wt%;

[0093] 4) Add tetrafluoroterephthalic acid and zirconium oxynitrate hydrate in a molar ratio of 1:1 to concentrated acetic acid and heat and stir at 50°C to dissolve them, forming a homogeneous precursor solution; transfer the two solutions obtained to a reaction vessel and carry out a solvothermal reaction at 50°C for 5 min.

[0094] 5) After the reaction is complete, allow the mixture to cool naturally to room temperature, centrifuge to collect the white precipitate, and wash it three times with DMF and ethanol alternately. Then, place the product in an 80℃ vacuum oven to dry for 12 h to obtain UiO-66-4F powder.

[0095] 6) Dissolve the ionic liquid TEA-PS·HSO4 in ethanol to form an ionic liquid alcohol solution; then add UiO-66-4F powder and stir continuously for 6 h, so that the ionic liquid enters the pore structure of UiO-66-4F under the action of capillary wetting and pore confinement; the mass ratio of UiO-66-4F to ionic liquid TEA-PS·HSO4 is 1:1;

[0096] 7) Place the mixture obtained in step 6) in a vacuum oven at 70°C to evaporate the solvent and obtain MOF@IL powder loaded with ionic liquid;

[0097] 8) Add the MOF@IL powder obtained in step 7) to the SPEEK solution obtained in step 3) and stir to mix to obtain SPEEK / MOF@IL composite modified solution, wherein the mass ratio of SPEEK, UiO-66-4F and ionic liquid is 1:1:1;

[0098] 9) The iridium oxide pH electrode (IrO) x The metal electrode was immersed in the SPEEK / MOF@IL composite modification solution for 5 seconds for coating, and then dried under vacuum conditions. The coating was repeated 3 times to finally obtain the SPEEK / MOF@IL modified ruthenium oxide pH electrode.

[0099] from Figure 8 As can be seen from this, the SPEEK / MOF@IL modified IrO x Metal oxide electrodes still exhibit a rapid and accurate response to changes in the pH of the external solution, compared to... Figure 4(a) SPEEK film modified electrode and SPEEK / MOF@IL modified RuO x Metal electrode, modified IrO x The metal electrode exhibits better stability and faster response when switching pH buffer solutions, reaching 90% of its final stable potential within 10 seconds. This indicates that MOF@IL significantly enhances the proton conductivity and stability of SPEEK, and that SPEEK / MOF@IL modification is beneficial for RuO2. x and IrO x Metal oxide pH electrodes are all effective.

[0100] Example 7

[0101] 1) Add polyetheretherketone particles to concentrated sulfuric acid with a mass fraction of 98% and stir continuously in an ice-water bath until completely dissolved; then heat to 50°C under a nitrogen atmosphere to carry out a sulfonation reaction for 4 hours.

[0102] 2) Slowly pour the obtained polymer solution into an ice-water mixture to terminate the reaction, collect the precipitated particles, and wash them repeatedly with deionized water until the pH of the washing solution is 6-7; then place the particles in a 70℃ oven to dry for 24 h to obtain SPEEK particles;

[0103] 3) Add the obtained SPEEK particles to DMF and stir to dissolve, preparing a SPEEK solution with a mass fraction of 10 wt%;

[0104] 4) Add tetrafluoroterephthalic acid and zirconium oxynitrate hydrate in a molar ratio of 1:1 to concentrated acetic acid and heat and stir at 50°C to dissolve them, forming a homogeneous precursor solution; transfer the two solutions obtained to a reaction vessel and carry out a solvothermal reaction at 50°C for 5 min.

[0105] 5) After the reaction is complete, allow the mixture to cool naturally to room temperature, centrifuge to collect the white precipitate, and wash it three times with DMF and ethanol alternately. Then, place the product in an 80℃ vacuum oven to dry for 12 h to obtain UiO-66-4F powder.

[0106] 6) The ionic liquid TEA-PS·HSO4 was dissolved in ethanol to form an ionic liquid alcohol solution; then UiO-66-4F powder was added and stirred continuously for 6 h, allowing the ionic liquid to enter the pore structure of UiO-66-4F under capillary wetting and pore confinement effects; the mass ratio of UiO-66-4F to ionic liquid [HOEtMIM][Cl] was 1:1, and the structural formula of ionic liquid [HOEtMIM][Cl] is shown below:

[0107]

[0108] 7) Place the mixture obtained in step 6) in a vacuum oven at 70°C to evaporate the solvent and obtain MOF@IL powder loaded with ionic liquid;

[0109] 8) Add the MOF@IL powder obtained in step 7) to the SPEEK solution obtained in step 3) and stir to mix to obtain SPEEK / MOF@IL composite modified solution, wherein the mass ratio of SPEEK, UiO-66-4F and ionic liquid is 1:1:1;

[0110] 9) Use a ruthenium oxide pH electrode (RuO2). x The metal electrode was immersed in the SPEEK / MOF@IL composite modification solution for 5 seconds for coating, and then dried under vacuum conditions. The coating was repeated 3 times to finally obtain the SPEEK / MOF@IL modified ruthenium oxide pH electrode. Figure 9 The graph shows the potential response of the electrode obtained in Example 7 to changes in solution pH. As can be seen from the graph, the electrode has a rapid and accurate response to changes in the pH value of the external solution.

[0111] Example 8

[0112] 1) Add polyetheretherketone particles to concentrated sulfuric acid with a mass fraction of 98% and stir continuously in an ice-water bath until completely dissolved; then heat to 50°C under a nitrogen atmosphere to carry out a sulfonation reaction for 4 hours.

[0113] 2) Slowly pour the obtained polymer solution into an ice-water mixture to terminate the reaction, collect the precipitated particles, and wash them repeatedly with deionized water until the pH of the washing solution is 6-7; then place the particles in a 70℃ oven to dry for 24 h to obtain SPEEK particles;

[0114] 3) Add the obtained SPEEK particles to DMF and stir to dissolve, preparing a SPEEK solution with a mass fraction of 10 wt%;

[0115] 4) Add tetrafluoroterephthalic acid and zirconium oxynitrate hydrate in a molar ratio of 1:1 to concentrated acetic acid and heat and stir at 50°C to dissolve them, forming a homogeneous precursor solution; transfer the two solutions obtained to a reaction vessel and carry out a solvothermal reaction at 50°C for 5 min.

[0116] 5) After the reaction is complete, allow the mixture to cool naturally to room temperature, centrifuge to collect the white precipitate, and wash it three times with DMF and ethanol alternately. Then, place the product in an 80℃ vacuum oven to dry for 12 h to obtain UiO-66-4F powder.

[0117] 6) Dissolve the ionic liquid TEA-PS·HSO4 in ethanol to form an ionic liquid alcohol solution; then add UiO-66-4F powder and stir continuously for 6 h, allowing the ionic liquid to enter the pore structure of UiO-66-4F under capillary wetting and pore confinement effects; UiO-66-4F reacts with the ionic liquid [C8mim + [C1C1N] - The mass ratio of [C8mim] is 1:1, ionic liquid [C8mim] + [C1C1N] - The molecular formula of ] is shown below:

[0118]

[0119] 7) Place the mixture obtained in step 6) in a vacuum oven at 70°C to evaporate the solvent and obtain MOF@IL powder loaded with ionic liquid;

[0120] 8) Add the MOF@IL powder obtained in step 7) to the SPEEK solution obtained in step 3) and stir to mix to obtain SPEEK / MOF@IL composite modified solution, wherein the mass ratio of SPEEK, UiO-66-4F and ionic liquid is 1:1:1;

[0121] 9) Use a ruthenium oxide pH electrode (RuO2). x The metal electrode was immersed in the SPEEK / MOF@IL composite modification solution for 5 seconds for coating, and then dried under vacuum conditions. The coating was repeated 3 times to finally obtain the SPEEK / MOF@IL modified ruthenium oxide pH electrode. Figure 10 The graph shows the potential response of the electrode obtained in Example 8 to changes in solution pH. As can be seen from the graph, the electrode has a rapid and accurate response to changes in the pH value of the external solution.

[0122] The above-described embodiments are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. Those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. An anti-interference pH electrode based on a confined ionic liquid-MOF composite structure, characterized in that: The pH electrode comprises a metal oxide pH electrode body and a SPEEK / MOF@IL composite modified film covering the surface of its metal oxide sensitive layer; the composite modified film uses SPEEK as the main matrix and MOF@IL, a metal-organic framework material loaded with ionic liquid, as the functional filler; the ionic liquid is confined and loaded in the pore structure of the metal-organic framework material; the SPEEK / MOF@IL composite modified film completely covers the metal oxide sensitive layer on the surface of the pH electrode body; wherein, the metal-organic framework material is UiO-66-4F.

2. The anti-interference pH electrode based on a confined ionic liquid-MOF composite structure according to claim 1, characterized in that, The ionic liquid is TEA-PS•HSO4, [HOEtMIM][Cl], or [C8mim]. + [C1C1N] - ]; The structural formula of TEA-PS•HSO4 is: ; The structural formula of [HOEtMIM][Cl] is: ; [C8mim + [C1C1N] - The structural formula of ] is: .

3. The anti-interference pH electrode based on a confined ionic liquid-MOF composite structure according to claim 1, characterized in that, The metal oxide pH electrode body is Ru / RuO. x pH electrode or Ir / IrO x pH electrode.

4. The anti-interference pH electrode based on a confined ionic liquid-MOF composite structure according to claim 1, characterized in that, In the SPEEK / MOF@IL composite modified film, the mass ratio of SPEEK, metal-organic framework material and ionic liquid is (0.5~2):(0.5~2):(0.5~2).

5. A method for preparing an anti-interference pH electrode according to any one of claims 1-4, characterized in that, Includes the following steps: 1) Prepare a sulfonated polyether ether ketone solution with a mass fraction of 5-15 wt%; 2) Dissolve the ionic liquid in alcohol to form an ionic liquid alcohol solution; then add metal-organic framework material powder and stir continuously for 4-6 h, so that the ionic liquid enters the pore structure of the metal-organic framework material under the capillary wetting and pore confinement effects; 3) Place the mixture obtained in step 2) in a vacuum oven and evaporate the solvent at 60-80°C to obtain MOF@IL powder loaded with ionic liquid; 4) Add the MOF@IL powder obtained in step 3) to the sulfonated polyether ether ketone solution and stir to mix, to obtain the SPEEK / MOF@IL composite modified solution; 5) The SPEEK / MOF@IL composite modification solution was coated onto the surface of the sensitive layer of the metal oxide pH electrode and dried to obtain the SPEEK / MOF@IL composite modified membrane pH electrode.

6. The preparation method according to claim 5, characterized in that, In step 5), the covering method is dipping or immersion, and the covering is repeated 2 to 5 times, with drying performed after each covering.

7. The preparation method according to claim 5, characterized in that, The drying method in step 5) is vacuum drying.

8. The application of the anti-interference pH electrode according to any one of claims 1-4 in in-situ pH detection in an aqueous environment.

9. The application according to claim 8, characterized in that, The water medium environment includes natural water bodies, biological system liquids, and chemical system liquids.

10. The application according to claim 8, characterized in that, The aqueous medium environment contains redox-active substances, organic pollutants, or biomass components.

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