Interface covalently constructed MOF (Metal Organic Framework) composite electrolyte film as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of polymer composite materials and functional electrolyte materials, and relates to an interface covalently constructed MOF composite electrolyte film, and a preparation method and application thereof. The method comprises the following steps: preparing a polymer matrix formed by polymerizing imidazole zwitterionic monomers and a metal organic framework material; the preparation method comprises the following steps: sequentially adding a polymer matrix formed by polymerizing imidazole zwitterionic monomers, a metal organic framework material, an ionic liquid and a photoinitiator into a methanol solvent to obtain a precursor suspension; initiating free radical polymerization reaction of acrylate double bonds by the precursor suspension in a photo-initiation or thermal initiation mode to form an initial three-dimensional cross-linked network; and heating the initial three-dimensional cross-linked network to volatilize the methanol solvent, and cooling to room temperature to obtain the interface covalently constructed MOF composite electrolyte film. Through covalent bonding interface engineering design, the problems of poor dispersibility and weak interface bonding of MOF in a polymer matrix are solved. The obtained film has excellent mechanical properties and ionic conductivity.

Description

Technical Field

[0001] This invention belongs to the technical field of polymer composite materials and functional electrolyte materials, and relates to an interfacial covalently constructed MOF composite electrolyte film, its preparation method and its application. Background Technology

[0002] With the rapid development of flexible electronics and wearable devices, flexible sensors and flexible solid electrolyte materials have become research hotspots. Among them, imidazole zwitterionic polymers have attracted much attention due to their ion migration channels and good biocompatibility. However, single polymer electrolyte systems present a dilemma: ionic conductivity and mechanical properties are difficult to balance. Reducing the crosslinking density can improve conductivity but decreases mechanical strength, while increasing the crosslinking density restricts chain segment movement, leading to decreased ion conduction performance, and also results in insufficient structural stability under repeated deformation.

[0003] To overcome the aforementioned problems, researchers have attempted to introduce metal-organic frameworks (MOFs) to construct composite electrolyte systems. MOFs, due to their ordered channels, high specific surface area, and tunable functional groups, are considered to improve mechanical properties and provide additional channels for ion migration. Currently, physical blending methods are mainly used to disperse MOF powders in monomer or polymer solutions, followed by polymerization or film formation to achieve filler dispersion and performance synergy. However, existing physical blending methods have significant shortcomings: the interaction between MOFs and the polymer matrix is ​​primarily physical, resulting in limited interfacial bonding; high MOF content easily leads to agglomeration, causing internal defects in the material; stress concentration easily occurs at the interface during stretching or bending, leading to cracking or filler detachment; and there is a risk of filler migration or leaching during long-term use. Although some studies have performed surface functionalization modifications on MOFs to improve dispersibility, they have still failed to enable MOFs to directly participate in polymerization reactions to form chemically bonded structures. MOFs are only embedded in the system as filler particles rather than network structural units, making it impossible to achieve a continuous and stable three-dimensional cross-linked network, and thus difficult to synergistically optimize mechanical and ion conduction properties. Summary of the Invention

[0004] The purpose of this invention is to provide an interfacial covalently constructed MOF composite electrolyte film, its preparation method, and its application, in order to solve the technical problems in the prior art where MOFs cannot directly participate in the polymerization reaction to form a chemically bonded structure, and MOFs are only embedded in the system as filler particles rather than network structural units, making it impossible to achieve a continuous and stable three-dimensional cross-linked network and difficult to synergistically optimize mechanical properties and ion conduction properties.

[0005] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, this application discloses an interfacial covalently constructed MOF composite electrolyte film, which, by mass percentage, comprises 40% to 55% of a polymer matrix formed by polymerizing imidazole zwitterionic monomers, 25% to 45% of a metal-organic framework material, and 15% to 30% of an ionic liquid.

[0006] Preferably, the polymer matrix formed by the polymerization of the imidazole zwitterionic monomer is 1,3-bis(6-acryloyloxyhexyl)imidazolium propane sulfonate monomer; the ionic liquid is an imidazole ionic liquid; and the metal-organic framework material is UiO-66-NH-AA.

[0007] Secondly, this application discloses a method for preparing an interfacially covalently constructed MOF composite electrolyte thin film, comprising: Preparation of polymer matrices and metal-organic frameworks formed by the polymerization of imidazole zwitterionic monomers; A precursor suspension was obtained by sequentially adding a polymer matrix formed by polymerizing imidazole zwitterionic monomers, a metal-organic framework material, an ionic liquid, and a photoinitiator into a methanol solvent. The precursor suspension was photo-initiated or thermally-initiated to initiate the free radical polymerization of acrylate double bonds, forming an initial three-dimensional cross-linked network. The initial three-dimensional cross-linked network was heated to evaporate the methanol solvent and then cooled to room temperature to obtain an interfacial covalently constructed MOF composite electrolyte film.

[0008] Preferably, the mass ratio of the polymer matrix formed by the polymerization of the imidazole zwitterionic monomer, the metal-organic framework material, and the ionic liquid is (40-55):(25-45):(15-30).

[0009] Preferably, the polymer matrix formed by polymerizing the imidazole zwitterionic monomer is 1,3-bis(6-acryloyloxyhexyl)imidazolium propane sulfonate monomer; the ionic liquid is an imidazole ionic liquid; and the metal-organic framework material is UiO-66-NH-AA.

[0010] Preferably, the preparation of the polymer matrix formed by polymerizing imidazole zwitterionic monomers includes: 6-(1-imidazolyl)-1-hexanol monomer was synthesized from imidazole via quaternization reaction; The monomer 6-(1-imidazolyl)-1-hexanol was reacted with sodium tribromopropane sulfonate to synthesize 1,3-bis(6-hydroxyhexyl)imidazolylpropane sulfonate monomer; The 1,3-bis(6-hydroxyhexyl)imidazolium propane sulfonate monomer was esterified with acryloyl chloride, and the purified product was obtained as the target product, 1,3-bis(6-acryloyloxyhexyl)imidazolium propane sulfonate monomer.

[0011] Preferably, the molar ratio of 6-(1-imidazolyl)-1-hexanol monomer to sodium tribromopropane sulfonate is (1~1.2):1; and the molar ratio of 1,3-bis(6-hydroxyhexyl)imidazolyl propane sulfonate monomer to acryloyl chloride is (1~1.3):3.

[0012] Preferably, the preparation of the metal-organic framework material specifically includes: Zirconium chloride and 2-aminoterephthalic acid were dissolved in N,N-dimethylformamide containing concentrated hydrochloric acid, and UiO-66-NH2 powder was synthesized by a solvothermal method. UiO-66-NH2 powder was dispersed in dichloromethane, and acrylic anhydride was added to carry out an amidation reaction. Acryloyl groups were covalently grafted onto the amino groups on the surface of UiO-66-NH2 to obtain a functionalized filler UiO-66-NH-AA with polymerizable double bonds on the surface.

[0013] Preferably, the molar ratio of zirconium chloride to 2-aminoterephthalic acid is 1:(1.3-1.5); the amount of N,N-dimethylformamide used per 1 mmol of zirconium chloride is 2.3-2.7 mL, the amount of concentrated hydrochloric acid used is 0.4-0.6 mL, the total amount of the N,N-dimethylformamide mixed solvent containing concentrated hydrochloric acid is 2.7-3.3 mL, and the volume ratio of N,N-dimethylformamide to concentrated hydrochloric acid is (4.5-5.5):1; when preparing UiO-66-NH-AA, the molar ratio of UiO-66-NH2 powder, acrylic anhydride, and dichloromethane is 1:(2.3-2.5):126.

[0014] Thirdly, this application discloses the application of an interfacially covalently constructed MOF composite electrolyte film in a flexible sensor, characterized in that the interfacially covalently constructed MOF composite electrolyte film serves as a sensing layer and is disposed between the electrode layers.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The interfacial covalently constructed MOF composite electrolyte film disclosed in this application significantly improves the interfacial compatibility between the metal-organic framework material and the polymer matrix through interfacial covalent bonding design. Within the aforementioned mass fraction range, the polymer matrix formed by the polymerization of imidazole zwitterionic monomers and the metal-organic framework material form a stable interfacial structure through covalent bonding, effectively suppressing MOF aggregation and enhancing the mechanical integrity and structural stability of the composite electrolyte film. Simultaneously, by rationally controlling the mass ratio of the polymer matrix, metal-organic framework material, and ionic liquid, synergistic optimization of ion conduction performance and mechanical properties is achieved. Within the specified composition range, the composite film can form a suitable microstructure, balancing good molecular chain flexibility and network integrity, thereby exhibiting low ion conduction activation energy and stable electrochemical performance under both room temperature and heated conditions.

[0016] This application discloses a method for preparing a covalently constructed MOF composite electrolyte film. The invention involves blending a polymer matrix formed by the polymerization of imidazole zwitterionic monomers, a metal-organic framework (MOF) material, an ionic liquid, and a photoinitiator in a methanol solvent to form a uniform precursor suspension. A free radical polymerization reaction is then initiated using photoinitiation or thermal initiation, causing in-situ copolymerization between the polymerizable double bonds on the surface of the MOF material and the polymer matrix. This constructs a "molecular-level" covalent interface between the MOF and the polymer matrix. This interface structure effectively solves the problem of poor interfacial compatibility in traditional physical blending, significantly improving the mechanical integrity and structural stability of the composite film. Furthermore, the method maintains the structural integrity of the cross-linked network during solvent removal by first constructing a three-dimensional cross-linked network and then evaporating the solvent, avoiding phase separation or network collapse. This results in a composite electrolyte film with a uniform structure and controllable microstructure. The photoinitiation or thermal initiation methods are mild and easy to operate, which helps maintain the functional properties of the MOF material and the ionic liquid during preparation, thus endowing the composite film with good flexibility and stable ion conductivity.

[0017] The composite electrolyte film described in this invention exhibits excellent signal response performance in flexible sensor applications. Flexible sensors constructed using this film as the core sensing layer demonstrate regular periodic signal responses, good peak consistency, fast response / recovery speed, and excellent anti-interference capabilities in dynamic motion scenarios such as fingers, wrists, and elbows, as well as in monitoring weak physiological signals such as swallowing. Furthermore, the signal exhibits no significant baseline drift or clutter interference, fully validating the enormous application potential of this composite electrolyte film in the field of wearable health monitoring. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 Comparison of optical photographs of the dispersions of UiO-66-NH2 and UiO-66-NH-AA prepared in the embodiments of the present invention; Figure 2 Scanning electron microscope (SEM) images of UiO-66-NH2 and UiO-66-NH-AA prepared in the embodiments of the present invention at different magnifications; Figure 3 The X-ray diffraction (XRD) patterns of UiO-66-NH2 and UiO-66-NH-AA prepared for the embodiments of the present invention are shown and compared with those of simulated UiO-66-NH2. Figure 4 Fourier transform infrared (FT-IR) spectra of UiO-66-NH2 and UiO-66-NH-AA prepared in the embodiments of the present invention; Figure 5 Scanning electron microscope (SEM) images of five polymer electrolyte films with different ratios prepared in the embodiments of the present invention at different magnifications; Figure 6 Wide-angle X-ray scattering (WAXS) spectra of five polymer electrolyte films with different ratios prepared in the embodiments of the present invention; Figure 7 Fourier transform infrared (FT-IR) spectra of five polymer electrolyte films with different ratios prepared in the embodiments of the present invention; Figure 8 A summary graph of differential scanning calorimetry (DSC) curves and glass transition temperatures (Tg) of five polymer electrolyte films with different ratios prepared in the embodiments of the present invention; Figure 9 Tensile stress-strain curves of five polymer electrolyte films with different ratios prepared in the embodiments of the present invention; Figure 10 The diagram shows the ionic conductivity of five polymer electrolyte films with different ratios prepared in the embodiments of the present invention. Figure 11 The signal response curves of the flexible sensor based on five different ratios of polymer electrolyte films constructed in this embodiment of the invention during the finger bending-resetting cycle are shown. Figure 12The signal response curves of the flexible sensor based on five different ratios of polymer electrolyte films constructed in this embodiment of the invention during the wrist flexion-reset cycle are shown. Figure 13 The image shows the signal response curves of a flexible sensor based on five different ratios of polymer electrolyte films constructed according to an embodiment of the present invention during an elbow flexion-reset cycle. Detailed Implementation

[0020] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0021] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0022] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0023] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0024] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0025] The present invention will now be described in further detail with reference to the accompanying drawings: This application discloses an interfacially covalently constructed MOF composite electrolyte film, comprising, by mass percentage, 40%–55% of a polymer matrix formed by the polymerization of imidazole zwitterionic monomers, 25%–45% of a metal-organic framework material, and 15%–30% of an ionic liquid. By introducing polymerizable double bonds on the MOF surface, the MOF participates in the copolymerization reaction during in-situ free radical polymerization, thereby forming a molecular-level covalently bonded interfacial structure. Compared with traditional physical blending systems, this invention has the following significant advantages: MOF particles are fixed in a cross-linked network, avoiding aggregation and detachment; the covalent interface improves stress transfer efficiency; continuous ion migration channels are constructed; and synergistic optimization of mechanical properties and ionic conductivity is achieved.

[0026] In some embodiments, the polymer matrix formed by polymerizing the imidazole zwitterionic monomer is 1,3-bis(6-acryloyloxyhexyl)imidazolium propane sulfonate monomer; the ionic liquid is an imidazole ionic liquid; and the metal-organic framework material is UiO-66-NH-AA. A covalently bonded MOF-zwitterionic polymer composite electrolyte film is constructed using an imidazole zwitterionic polymer as the matrix, acryloyl-functionalized UiO-66-NH-AA as the active filler, and the ionic liquid [C2mim][FSI] as the ion-conducting medium, through an in-situ free radical copolymerization strategy. The functional filler is covalently bonded to the polymer matrix through polymerizable double bonds on its surface, forming a stable three-dimensional cross-linked network structure. This composite electrolyte film possesses both excellent mechanical properties and efficient ion conduction characteristics, and can be used as a core sensing layer in flexible sensors to achieve accurate detection of human motion signals.

[0027] This application also discloses a method for preparing an interfacially covalently constructed MOF composite electrolyte thin film, comprising: Preparation of polymer matrices and metal-organic frameworks formed by the polymerization of imidazole zwitterionic monomers; A precursor suspension was obtained by sequentially adding a polymer matrix formed by polymerizing imidazole zwitterionic monomers, a metal-organic framework material, an ionic liquid, and a photoinitiator into a methanol solvent. The precursor suspension was photo-initiated or thermally-initiated to initiate the free radical polymerization of acrylate double bonds, forming an initial three-dimensional cross-linked network. The initial three-dimensional cross-linked network was heated to evaporate the methanol solvent and then cooled to room temperature to obtain an interfacial covalently constructed MOF composite electrolyte film.

[0028] In some embodiments, the mass ratio of the polymer matrix formed by the polymerization of the imidazole zwitterionic monomer, the metal-organic framework material, and the ionic liquid is (40-55):(25-45):(15-30).

[0029] In some embodiments, the polymer matrix formed by polymerizing the imidazole zwitterionic monomer is 1,3-bis(6-acryloyloxyhexyl)imidazolium propane sulfonate monomer; the ionic liquid is an imidazole ionic liquid; and the metal-organic framework material is UiO-66-NH-AA.

[0030] In some embodiments, the preparation of the polymer matrix formed by polymerizing imidazole zwitterionic monomers includes: 6-(1-imidazolyl)-1-hexanol monomer was synthesized from imidazole via quaternization reaction; The monomer 6-(1-imidazolyl)-1-hexanol was reacted with sodium tribromopropane sulfonate to synthesize 1,3-bis(6-hydroxyhexyl)imidazolylpropane sulfonate monomer; The 1,3-bis(6-hydroxyhexyl)imidazolium propane sulfonate monomer was esterified with acryloyl chloride, and the purified product was obtained as the target product, 1,3-bis(6-acryloyloxyhexyl)imidazolium propane sulfonate monomer.

[0031] In some embodiments, the molar ratio of 6-(1-imidazolyl)-1-hexanol monomer to sodium tribromopropane sulfonate is (1~1.2):1; the molar ratio of 1,3-bis(6-hydroxyhexyl)imidazolyl propane sulfonate monomer to acryloyl chloride is (1~1.3):3.

[0032] In some embodiments, the preparation of the metal-organic framework material specifically includes: Zirconium chloride and 2-aminoterephthalic acid were dissolved in N,N-dimethylformamide containing concentrated hydrochloric acid, and UiO-66-NH2 powder was synthesized by a solvothermal method. UiO-66-NH2 powder was dispersed in dichloromethane, and acrylic anhydride was added to carry out an amidation reaction. Acryloyl groups were covalently grafted onto the amino groups on the surface of UiO-66-NH2 to obtain a functionalized filler UiO-66-NH-AA with polymerizable double bonds on the surface.

[0033] In some embodiments, the molar ratio of zirconium chloride to 2-aminoterephthalic acid is 1:(1.3-1.5); the amount of N,N-dimethylformamide used per 1 mmol of zirconium chloride is 2.3-2.7 mL, the amount of concentrated hydrochloric acid used is 0.4-0.6 mL, the total amount of the N,N-dimethylformamide mixed solvent containing concentrated hydrochloric acid is 2.7-3.3 mL, and the volume ratio of N,N-dimethylformamide to concentrated hydrochloric acid is (4.5-5.5):1; when preparing UiO-66-NH-AA, the molar ratio of UiO-66-NH2 powder, acrylic anhydride, and dichloromethane is 1:(2.3-2.5):126.

[0034] In some embodiments, the preparation method of the covalently bonded MOF-zwitterionic polymer composite electrolyte film specifically includes the following steps: S1: Preparation of imidazole zwitterionic monomer PIM3S: Using imidazole as a raw material, 6-(1-imidazolyl)-1-hexanol (HIm) monomer was synthesized by quaternization reaction; then reacted with sodium tribromopropane sulfonate (3-BPS) to synthesize 1,3-bis(6-hydroxyhexyl)imidazolium propane sulfonate (HIm3S) monomer; finally, it was esterified with acryloyl chloride (ACC), and purified to obtain the target product 1,3-bis(6-acryloyloxyhexyl)imidazolium propane sulfonate (PIm3S) monomer. S2: Preparation of Acryloyl-functionalized metal-organic framework UiO-66-NH-AA: UiO-66-NH2 was synthesized by a solvothermal method, dispersed in dichloromethane, and subjected to amidation reaction by adding acrylic anhydride. Acryloyl groups were covalently grafted onto the amino groups on the surface of UiO-66-NH2 to obtain functionalized filler UiO-66-NH-AA with polymerizable double bonds on the surface. S3: Preparation of precursor suspension: The PIM3S monomer obtained in step S1, the UiO-66-NH-AA obtained in step S2, the ionic liquid [C2mim][FSI], and the photoinitiator 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone (907) were added to methanol solvent in sequence and ultrasonically dispersed for 30 min to form a uniform and stable precursor suspension; S4: In-situ polymerization and film formation: The precursor suspension obtained in step S3 is transferred to a polytetrafluoroethylene mold, leveled and covered to the bottom of the mold; the mold is placed under a UV light source to initiate the free radical polymerization reaction of the acrylate double bonds, forming an initial three-dimensional cross-linked network; the polymerized film is transferred to a 70 ℃ heating stage to evaporate and remove the methanol solvent, promoting network shrinkage and densification; after cooling to room temperature, it is peeled off from the mold to obtain a self-supporting solid polymer electrolyte film.

[0035] Further, the preparation method of the HIm monomer in step S1 is as follows: at room temperature, imidazole, potassium hydroxide and dimethyl sulfoxide are mixed in a molar ratio of 1:1.2:7 and heated to reflux at 70 °C until the solid is completely dissolved; after cooling, 6-chloro-1-hexanol is added and the mixture is stirred at room temperature for 24 hours; after the reaction is completed, the HIm monomer is obtained by extraction with dichloromethane, washing and rotary evaporation.

[0036] Further, the preparation method of the HIm3S monomer in step S1 is as follows: HIm monomer and sodium tribromopropanesulfonate are dissolved in N,N-dimethylformamide at a molar ratio of 1:1 and stirred at 70 °C overnight; after the reaction is completed, the monomer is dissolved in ethanol, washed with ethyl acetate, and dried under vacuum to obtain HIm3S monomer.

[0037] Further, the preparation method of the HIm3S monomer in step S1 is as follows: HIm monomer and sodium tribromopropanesulfonate are dissolved in N,N-dimethylformamide at a molar ratio of 1.1:1 and stirred overnight at 70 °C; after the reaction is completed, the monomer is dissolved in ethanol, washed with ethyl acetate, and dried under vacuum to obtain HIm3S monomer.

[0038] Further, the preparation method of the HIm3S monomer in step S1 is as follows: HIm monomer and sodium tribromopropanesulfonate are dissolved in N,N-dimethylformamide at a molar ratio of 1.2:1 and stirred overnight at 70 °C; after the reaction is completed, the monomer is dissolved in ethanol, washed with ethyl acetate, and dried under vacuum to obtain HIm3S monomer.

[0039] Further, the preparation method of the PIm3S monomer in step S1 is as follows: HIm3S monomer and acryloyl chloride are dissolved in tetrahydrofuran at a molar ratio of 1:3, 4-pyrrolidinylpyridine and 2,6-di-tert-butyl-p-cresol are added, and the mixture is stirred overnight in an ice-water bath at 0 °C; after the reaction is completed, the mixture is washed with a mixed solvent of petroleum ether and ethyl acetate, filtered, dissolved in acetonitrile, filtered, and rotary evaporated to obtain the crude PIm3S product; it is purified by dry column chromatography using a mixed solution of dichloromethane and methanol with a volume ratio of 95:5 as the eluent, the target fraction is collected, and the purified PIm3S monomer is obtained after rotary evaporation and drying.

[0040] Further, the preparation method of the PIm3S monomer in step S1 is as follows: HIm3S monomer and acryloyl chloride are dissolved in tetrahydrofuran at a molar ratio of 1.2:3, 4-pyrrolidinylpyridine and 2,6-di-tert-butyl-p-cresol are added, and the mixture is stirred overnight in an ice-water bath at 0 °C; after the reaction is completed, the mixture is washed with a mixed solvent of petroleum ether and ethyl acetate, filtered, dissolved in acetonitrile, filtered, and rotary evaporated to obtain crude PIm3S product; it is purified by dry column chromatography using a mixed solution of dichloromethane and methanol with a volume ratio of 95:5 as the eluent, the target fraction is collected, and the purified PIm3S monomer is obtained after rotary evaporation and drying.

[0041] Further, the preparation method of the PIm3S monomer in step S1 is as follows: HIm3S monomer and acryloyl chloride are dissolved in tetrahydrofuran at a molar ratio of 1.3:3, 4-pyrrolidinylpyridine and 2,6-di-tert-butyl-p-cresol are added, and the mixture is stirred overnight in an ice-water bath at 0 °C. After the reaction is completed, the mixture is washed with a mixed solvent of petroleum ether and ethyl acetate, filtered, dissolved in acetonitrile, filtered, and rotary evaporated to obtain the crude PIm3S product. The crude product is purified by dry column chromatography using a mixed solution of dichloromethane and methanol with a volume ratio of 95:5 as the eluent. The target fraction is collected, and the purified PIm3S monomer is obtained after rotary evaporation and drying.

[0042] Further, the preparation method of UiO-66-NH2 in step S2 is as follows: zirconium chloride and 2-aminoterephthalic acid are dissolved separately in N,N-dimethylformamide containing concentrated hydrochloric acid at a molar ratio of 1:1.4. After mixing, the mixture is transferred to a reaction vessel and reacted at 80 °C for 12 hours. The reaction product is collected by centrifugation, washed with DMF, soaked in ethanol for 3 days, and vacuum dried at 150 °C for 12 hours to obtain UiO-66-NH2 powder. The amount of N,N-dimethylformamide used is 2.3 mL, the amount of concentrated hydrochloric acid used is 0.4 mL, the total amount of the N,N-dimethylformamide mixed solvent containing concentrated hydrochloric acid is 2.7 mL, and the volume ratio of N,N-dimethylformamide to concentrated hydrochloric acid is 4.5:1. Further, the preparation method of UiO-66-NH2 in step S2 is as follows: zirconium chloride and 2-aminoterephthalic acid are dissolved in N,N-dimethylformamide containing concentrated hydrochloric acid at a molar ratio of 1:1.3, respectively. After mixing, the mixture is transferred to a reaction vessel and reacted at 80 °C for 12 hours. The reaction product is collected by centrifugation, washed with DMF, soaked in ethanol for 3 days, and vacuum dried at 150 °C for 12 hours to obtain UiO-66-NH2 powder. The amount of N,N-dimethylformamide used is 2.5 mL, the amount of concentrated hydrochloric acid used is 0.5 mL, the total amount of the N,N-dimethylformamide mixed solvent containing concentrated hydrochloric acid is 3.0 mL, and the volume ratio of N,N-dimethylformamide to concentrated hydrochloric acid is 5:1.

[0043] Further, the preparation method of UiO-66-NH2 in step S2 is as follows: zirconium chloride and 2-aminoterephthalic acid are dissolved in N,N-dimethylformamide containing concentrated hydrochloric acid at a molar ratio of 1:1.5, respectively. After mixing, the mixture is transferred to a reaction vessel and reacted at 80 °C for 12 hours. The reaction product is collected by centrifugation, washed with DMF, soaked in ethanol for 3 days, and vacuum dried at 150 °C for 12 hours to obtain UiO-66-NH2 powder. The amount of N,N-dimethylformamide used is 2.7 mL, the amount of concentrated hydrochloric acid used is 0.6 mL, the total amount of the N,N-dimethylformamide mixed solvent containing concentrated hydrochloric acid is 3.3 mL, and the volume ratio of N,N-dimethylformamide to concentrated hydrochloric acid is 5.5:1.

[0044] Further, the preparation method of UiO-66-NH-AA in step S2 is as follows: dry UiO-66-NH2 powder is dispersed in dichloromethane, acrylic anhydride is added at 0 °C, wherein the molar ratio of UiO-66-NH2, acrylic anhydride and dichloromethane is 1:2.3:126; the mixture is refluxed at 55 °C for 24 hours; after the reaction is completed, the product is collected by centrifugation, washed multiple times with fresh dichloromethane, and dried under vacuum at 40 °C for 6 hours to obtain UiO-66-NH-AA.

[0045] Further, the preparation method of UiO-66-NH-AA in step S2 is as follows: dry UiO-66-NH2 powder is dispersed in dichloromethane, acrylic anhydride is added at 0 °C, wherein the molar ratio of UiO-66-NH2, acrylic anhydride and dichloromethane is 1:2.4:126; the mixture is refluxed at 55 °C for 24 hours; after the reaction is completed, the product is collected by centrifugation, washed multiple times with fresh dichloromethane, and dried under vacuum at 40 °C for 6 hours to obtain UiO-66-NH-AA.

[0046] Further, the preparation method of UiO-66-NH-AA in step S2 is as follows: dry UiO-66-NH2 powder is dispersed in dichloromethane, acrylic anhydride is added at 0 °C, wherein the molar ratio of UiO-66-NH2, acrylic anhydride and dichloromethane is 1:2.5:126; the mixture is refluxed at 55 °C for 24 hours; after the reaction is completed, the product is collected by centrifugation, washed several times with fresh dichloromethane, and dried under vacuum at 40 °C for 6 hours to obtain UiO-66-NH-AA.

[0047] Furthermore, the mass ratio of each component in step S3 is as follows: based on 100 parts of PIM3S monomer, the amount of UiO-66-NH-AA added is 70 parts, the amount of [C2mim][FSI] added is 40 parts, and the amount of photoinitiator 907 added is 10 parts.

[0048] Further, the mass ratio of each component in step S3 is as follows: the mass ratio of the polymer matrix formed by the polymerization of the imidazole zwitterionic monomer, the metal-organic framework material, and the ionic liquid is 40: 25: 15.

[0049] Further, the mass ratio of each component in step S3 is as follows: the mass ratio of the polymer matrix formed by the polymerization of the imidazole zwitterionic monomer, the metal-organic framework material, and the ionic liquid is 55: 45: 30.

[0050] Further, the mass ratio of each component in step S3 is as follows: the mass ratio of the polymer matrix formed by the polymerization of the imidazole zwitterionic monomer, the metal-organic framework material, and the ionic liquid is 46:35:25.

[0051] Furthermore, in step S3, the amount of methanol solvent added is 0.3 mL of methanol for every 0.05 g PIm3S monomer.

[0052] Furthermore, the conditions for ultraviolet light-induced polymerization in step S4 are: ultraviolet light source wavelength of 365 nm, irradiation time of 60 min, and irradiation intensity of 10-20 mW / cm2.

[0053] This invention innovatively introduces acryloyl groups onto the surface of UiO-66-NH2 through a post-synthetic modification strategy, transforming it into a "macromonomer" capable of participating in polymerization reactions. This macromonomer is then subjected to in-situ free radical copolymerization with a self-designed imidazole zwitterionic monomer, PIM3S, achieving the construction of a covalently bonded interface between the MOF and the polymer matrix. This method fundamentally solves the core problems of poor dispersibility and weak interfacial bonding in traditional physical blending systems. By chemically coupling the rigid porous structure of the MOF with the flexible ionic conductivity of the zwitterionic polymer at the molecular scale, it achieves a synergistic performance of "high conductivity, strong mechanical properties, and stable interface." The resulting composite electrolyte film, with an optimal ratio of 70% MOF-40% [C2mim][FSI], exhibits a uniform and dense microstructure, a glass transition temperature of -28.6 ℃, an elastic modulus of 32.2 MPa, and an elongation at break of approximately 14%, demonstrating both excellent mechanical flexibility and structural stability. Furthermore, it exhibits high ionic conductivity and low ionic activation energy within the temperature range of room temperature to 70 ℃, providing an ideal core functional layer material for the development of high-performance flexible sensors.

[0054] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other. The invention will be further described in detail below with reference to specific embodiments.

[0055] In the performance tests of the embodiments, all tests were conducted under standard conditions.

[0056] The method for determining ionic conductivity is as follows: using an electrochemical workstation, AC impedance testing is performed under conditions of frequency range of 100 kHz to 0.1 Hz and AC amplitude of 10 mV. The film resistance Rb is obtained analytically through Nyquist plot, and the ionic conductivity is calculated according to the formula σ = d / (Rb × A) in combination with the film thickness d and electrode area A.

[0057] The method for determining the elastic modulus is as follows: a universal testing machine is used to perform a tensile test on the sample at a constant rate (10 mm / min), the stress-strain curve is recorded, and the elastic modulus is calculated according to the formula E = σ / ε within the elastic deformation range.

[0058] The method for determining the glass transition temperature is as follows: using a differential scanning calorimeter, under a nitrogen protective atmosphere, the temperature is increased from -50 °C to 40 °C at a rate of 10 °C / min, the heat flow change curve is recorded, and the Tg value is determined by analysis.

[0059] The method for determining the uniformity of MOF dispersion is SEM analysis.

[0060] Example 1: Synthesis of Pim3S monomer The preparation method of imidazole zwitterionic monomer PIM3S is illustrated below as an example. The preparation method includes the following steps: 1) Synthesis of HIm monomer: At room temperature, imidazole (60 g), potassium hydroxide (49.2 g) and dimethyl sulfoxide (400 g) were added sequentially to a dry three-necked flask and heated to reflux at 70 °C until the solid was completely dissolved. After cooling, 6-chloro-1-hexanol (100 g) was added and the mixture was stirred at room temperature for 24 hours. After the reaction was completed, deionized water and dichloromethane were added for extraction and separation. The washing was repeated 5 times. The organic phase was removed by rotary evaporation to obtain the HIm monomer.

[0061] 2) Synthesis of HIm3S monomer: HIm monomer (5 g), sodium tribromopropanesulfonate (6.7 g) and N,N-dimethylformamide (30 mL) were added to a reaction flask and stirred overnight at 70 °C. After the reaction was completed, ethanol was added to dissolve the product, which was washed three times with ethyl acetate and dried under vacuum to obtain HIm3S monomer.

[0062] 3) Synthesis of PIm3S monomer: HIm3S monomer (5 g), tetrahydrofuran (20 mL), 4-pyrrolidinylpyridine (0.051 g), 2,6-di-tert-butyl-p-cresol (0.05 g), and acetonitrile (2 mL) were added to a reaction flask. Acryloyl chloride (4.2 mL) was slowly added dropwise in an ice-water bath at 0 ℃. After the addition was complete, the mixture was stirred overnight at 0 ℃. After the reaction was completed, the mixture was washed with a 1:1 mixture of petroleum ether and ethyl acetate and filtered. The filter cake was collected and dried. The dried solid was dissolved in acetonitrile and filtered to remove insoluble impurities. The filtrate was evaporated under reduced pressure to remove the solvent, yielding crude PIm3S product. The product was purified by dry column chromatography using a 95:5 mixture of dichloromethane and methanol as the eluent. The target fraction was collected, dried by rotary evaporation, and the purified PIm3S monomer was obtained.

[0063] Example 2: Synthesis of UiO-66-NH-AA The following description uses the preparation method of acryloyl-functionalized metal-organic framework UiO-66-NH-AA as an example. The preparation method includes the following steps: 1) Synthesis of UiO-66-NH2: Zirconium chloride (approximately 10 mmol) was pre-dissolved in a mixed solution of 25 mL N,N-dimethylformamide and 5 mL concentrated hydrochloric acid. Separately, 2-aminoterephthalic acid (approximately 14 mmol) was pre-dissolved in an appropriate amount of N,N-dimethylformamide. The two solutions were mixed thoroughly and transferred to a 100 mL reactor. The reaction was carried out at 80 °C for 12 hours. After the reaction, the solid product was collected by centrifugation, washed three times with N,N-dimethylformamide, and then soaked and washed in ethanol for 3 days (changing the ethanol daily). Finally, it was vacuum dried at 150 °C for 12 hours to obtain UiO-66-NH2 powder. Its optical photographs, SEM images, XRD patterns, and FTIR spectra are shown below. Figure 1-4 As shown.

[0064] 2) Synthesis of UiO-66-NH-AA: Dry UiO-66-NH2 powder was dispersed in dichloromethane, and excess acrylic anhydride was added at 0 °C (the molar ratio of UiO-66-NH2, acrylic anhydride, and dichloromethane was 1:2.5:126). The mixture was refluxed at 55 °C for 24 hours. After the reaction was completed, the solid product was collected by centrifugation, washed several times with fresh dichloromethane, and dried under vacuum at 40 °C for 6 hours to obtain acrylamide-functionalized UiO-66-NH-AA. Its morphology and structure are shown in [reference needed]. Figure 1-4 .

[0065] Example 3: Preparation of composite electrolyte membrane (70% MOF-40% IL) In a nitrogen-protected glove box (with water and oxygen content below 0.1 ppm), based on 100 parts (0.05 g) of the Pim3S monomer prepared in Example 1, 70 parts (0.035 g) of UiO-66-NH-AA, 40 parts (0.02 g) of [C2mim][FSI], and 10 parts (0.005 g) of photoinitiator 907 prepared in Example 2 were weighed and added to 0.3 mL of methanol. The mixture was ultrasonically dispersed for 30 min to obtain a uniform suspension. The suspension was transferred to a polytetrafluoroethylene mold, leveled, and then placed under a UV light source (wavelength 365 nm, light intensity 15 mW / cm²) for polymerization initiation for 60 min. After polymerization, the mixture was transferred to a 70 °C heating stage to evaporate the solvent. After cooling, it was peeled off to obtain a self-supporting solid polymer electrolyte film, denoted as 70% MOF-40% IL.

[0066] Comparative Example 1: Preparation of 70% MOF-30% IL thin film The preparation method of Example 3 was followed, except that the amount of [C2mim][FSI] added was changed to 30 parts (0.015 g), and the other operations were the same as in Example 3, to obtain a 70% MOF-30% IL film.

[0067] Comparative Example 2: Preparation of 70% MOF-50% IL films The preparation method of Example 3 was followed, except that the amount of [C2mim][FSI] added was changed to 50 parts (0.025 g), and the other operations were the same as in Example 3, to obtain a 70% MOF-50% IL film.

[0068] Comparative Example 3: Preparation of 80% MOF-40% IL films The preparation method of Example 3 was followed, except that the amount of UiO-66-NH-AA added was changed to 80 parts (0.04 g), and the other operations were the same as in Example 3, to obtain an 80% MOF-40% IL film.

[0069] Comparative Example 4: Preparation of 90% MOF-40% IL films The preparation method of Example 3 was followed, except that the amount of UiO-66-NH-AA added was changed to 90 parts (0.045 g), and the other operations were the same as in Example 3, to obtain a 90% MOF-40% IL film.

[0070] Table 1 shows a comparison of the performance of the composite electrolyte films obtained in Example 3 and Comparative Examples 1-4.

[0071] Table 1. Performance Comparison of Composite Electrolyte Films with Different Ratios

[0072] As can be seen from Table 1, the composite electrolyte film prepared in Example 3 is superior to Comparative Examples 1-4 in terms of microstructure, thermal properties and mechanical properties, indicating that the 70% MOF-40% [C2mim][FSI] ratio is the composition with the best overall performance in this system.

[0073] Morphology and structural characterization of composite electrolyte films 1. Microstructure characterization of composite electrolyte films The composite films prepared in Example 3 and Comparative Examples 1-4 were cut into 1 cm × 1 cm sizes, attached to conductive adhesive, and then sputtered with gold using an ion sputtering apparatus (15 mA, 60 s). The surface morphology was then observed using a scanning electron microscope.

[0074] Figure 5 The images show SEM images of five polymer electrolyte films with different formulations prepared in the embodiments and comparative examples of this invention at different magnifications. As can be seen from the figures: In Example 3, the film exhibited a continuous, uniform, and smooth morphology without obvious particles at the 5 μm, 1 μm, and 500 nm scales. No MOF agglomeration or phase separation traces were observed, indicating that the crosslinking efficiency of [C2mim][FSI] and Pim3S monomers was optimal under this ratio. The ionic liquid can fully coat the MOF particles and promote their uniform dispersion, forming a dense and defect-free three-dimensional crosslinked network.

[0075] In Comparative Example 1, obvious granular protrusions are visible on the film at the 5 μm scale. Upon magnification, local agglomeration of the UiO-66-NH-AA filler is observed, and microcracks are present on the film surface. This is due to insufficient ionic liquid content, which fails to fully coat the MOF particles and fill the crosslinking network, resulting in excessively high crosslinking density and increased internal stress in the system.

[0076] Comparative Example 2: The film surface exhibits a uniform "foggy" morphology with no obvious particles or cracks, but slight phase separation textures are visible under high magnification. This is because the ionic liquid content is too high, and the excessive [C2mim][FSI] acts as a plasticizer, reducing the density of the cross-linked network and causing the system to exhibit a semi-gel state.

[0077] In Comparative Example 3, numerous granular protrusions were visible on the film at the 5 μm scale. Upon magnification, the aggregation of UiO-66-NH-AA particles was clearly observed, and there were obvious gaps between the particles. This was due to the excessive MOF content, which prevented the ionic liquid from fully coating all the filler particles.

[0078] In Comparative Example 4, a large number of MOF particle aggregates with uneven size were observed at both the 5 μm and 1 μm scales. There was no continuous polymer matrix connection between the particles, and they exhibited obvious "powder-like" stacking characteristics, indicating that the MOF content had far exceeded the dispersion limit of the system.

[0079] 2. Crystal structure characterization of composite electrolyte films The composite films prepared in Example 3 and Comparative Examples 1-4 were tested using a wide-angle X-ray scattering instrument, and the results are as follows: Figure 6 As shown. With a fixed UiO-66-NH-AA content of 70%, as the [C2mim][FSI] content increases from 30% to 50%, the film at q≈6 nm... -The characteristic diffraction peak intensity at position ¹ decreased significantly while the peak width increased, indicating that increasing the ionic liquid content weakened the orderly crystalline phase stacking of the MOF filler. With a fixed [C2mim][FSI] content of 40%, as the MOF content increased, the characteristic diffraction peak intensity gradually increased, the peak shape became sharper, and shifted to the right, indicating that excessive MOF content would induce crystalline phase aggregation. The film in Example 3 (70% MOF - 40% IL) exhibited a synergistic hybrid structure of "weak crystalline phase + amorphous," with moderate diffraction peak intensity and broadened peak shape. This retained the appropriate crystalline support of the MOF filler while maintaining the mobility of the polymer chains through the plasticizing effect of the ionic liquid.

[0080] The composite films prepared in Example 3 and Comparative Examples 1-4 were tested using Fourier transform infrared spectroscopy, and the results are as follows: Figure 7 As shown. The characteristic peaks of the film in Example 3 have moderate intensity and no obvious shift, indicating that the interaction between the ionic liquid, MOF filler and PIM3S monomer is in a synergistic equilibrium state under this ratio. It retains a moderate crosslinking effect to maintain mechanical strength, and ensures ionic conductivity through ionic dipole interaction.

[0081] 3. Differential scanning calorimetry analysis of composite electrolyte thin films The composite films prepared in Example 3 and Comparative Examples 1-4 were tested using differential scanning calorimetry, and the results are as follows: Figure 8 As shown, no obvious melting or crystallization peaks were observed in any of the film formulations during the cooling and heating stages, indicating that the composite films were predominantly amorphous. The Tg value of the film in Example 3 was -28.6 °C, which is in the middle of all formulations. This optimized value ensures the flexibility of the molecular chains of the film at room temperature while avoiding the network looseness caused by too low a Tg (e.g., Comparative Example 2 Tg = -31.7 °C) or the excessive rigidity caused by too high a Tg (e.g., Comparative Example 4 Tg = -15.4 °C).

[0082] 4. Mechanical property testing of composite electrolyte films The tensile properties of the composite films prepared in Example 3 and Comparative Examples 1-4 were tested using a universal testing machine. The results are as follows: Figure 9 As shown. The film in Example 3 exhibits an elastic modulus as high as 32.2 MPa, demonstrating optimal overall mechanical properties. This is attributed to the synergistic balance between the MOF and ionic liquid content—the plasticizing effect of an appropriate amount of ionic liquid ensures the mobility of chain segments, while the modified MOF is tightly bonded to the matrix through covalent bonding interfaces, effectively transferring and dispersing stress as a rigid reinforcing phase.

[0083] 5. Electrochemical performance testing of composite electrolyte films The conductivity of the composite films prepared in Example 3 and Comparative Examples 1-4 was tested using an electrochemical workstation, and the results are as follows: Figure 10As shown. The ionic conductivity of the film in Example 3 is at a high level across the entire temperature range (0.025 mS / cm at room temperature and 0.2 mS / cm at 70 °C).

[0084] 6. Performance Testing of Flexible Sensors Based on Composite Electrolyte Thin Films Flexible sensors were constructed using the composite films prepared in Examples 3 and Comparative Examples 1-4. First, composite polymer electrolyte films with different component ratios were cut into small circular pieces of uniform size and stably sandwiched between two symmetrical positive and negative electrode patches (slightly larger than the composite polymer electrolyte film) to form a sandwich structure of "positive electrode patch / composite electrolyte film / negative electrode patch". Then, two copper wires of the same length were fixed at the edges of the positive and negative electrode patches to ensure stable conductivity. The sensor was then tightly attached to the target test site on the human body, and the impedance change signal during human movement was collected in real time using an AC impedance meter.

[0085] like Figure 11 As shown, a finger bending test was performed on the composite electrolyte film. In Example 3, the sensor signal curve exhibited regular periodic fluctuations, with the signal rising rapidly during bending and falling back quickly upon resetting. The peak consistency was strong, with no baseline drift or clutter interference. In Comparative Example 1, the sensor signal fluctuation amplitude was small, exhibiting a "signal loss" phenomenon; in Comparative Example 2, the sensor signal baseline drift was severe; in Comparative Example 3, the sensor signal had sharp clutter peaks; and in Comparative Example 4, the sensor signal fluctuation was weak and irregular.

[0086] like Figure 12 As shown, a wrist bending test was performed on the composite electrolyte membrane. In Example 3, the sensor signal curve exhibited a symmetrical "rise-fall" characteristic, with a stable baseline and no drift. The signal amplitude did not attenuate after multiple cycles. In Comparative Example 1, the sensor signal peak was small and had low discrimination; in Comparative Example 2, the sensor signal was "sawtooth"; and in Comparative Examples 3 and 4, the sensor signal response was lagging and fluctuated significantly, exhibiting a "tailing" phenomenon during reset.

[0087] like Figure 13 As shown, elbow bending tests were performed on the composite electrolyte membrane. In Example 3, the sensor signal curve clearly exhibited a cyclical characteristic of "bending up - resetting down," with the highest signal peak reaching 6.5. After resetting, the signal returned to the baseline. In Comparative Example 1, the sensor signal peak was approximately 0.05; in Comparative Example 2, the sensor signal baseline drifted significantly; in Comparative Example 3, the sensor signal rose slowly; and in Comparative Example 4, the sensor signal fluctuated violently and irregularly.

[0088] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0089] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0090] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A covalently constructed MOF composite electrolyte film at the interface, characterized in that, By mass percentage, it comprises 40%–55% of a polymer matrix formed by the polymerization of imidazole zwitterionic monomers, 25%–45% of a metal-organic framework material, and 15%–30% of an ionic liquid.

2. The interfacial covalently constructed MOF composite electrolyte film according to claim 1, characterized in that, The polymer matrix formed by the polymerization of the imidazole zwitterionic monomer is 1,3-bis(6-acryloyloxyhexyl)imidazolium propane sulfonate monomer; the ionic liquid is an imidazole ionic liquid; and the metal-organic framework material is UiO-66-NH-AA.

3. A method for preparing an interfacially covalently constructed MOF composite electrolyte thin film, characterized in that, include: Preparation of polymer matrices and metal-organic frameworks formed by the polymerization of imidazole zwitterionic monomers; A precursor suspension was obtained by sequentially adding a polymer matrix formed by polymerizing imidazole zwitterionic monomers, a metal-organic framework material, an ionic liquid, and a photoinitiator into a methanol solvent. The precursor suspension was photo-initiated or thermally-initiated to initiate the free radical polymerization of acrylate double bonds, forming an initial three-dimensional cross-linked network. The initial three-dimensional cross-linked network was heated to evaporate the methanol solvent and then cooled to room temperature to obtain an interfacial covalently constructed MOF composite electrolyte film.

4. The method for preparing an interfacially covalently constructed MOF composite electrolyte film according to claim 3, characterized in that, The mass ratio of the polymer matrix formed by the polymerization of the imidazole zwitterionic monomer, the metal-organic framework material, and the ionic liquid is (40-55):(25-45):(15-30).

5. The method for preparing an interfacially covalently constructed MOF composite electrolyte film according to claim 3, characterized in that, The polymer matrix formed by the polymerization of the imidazole zwitterionic monomer is 1,3-bis(6-acryloyloxyhexyl)imidazolium propane sulfonate monomer; the ionic liquid is an imidazole ionic liquid; and the metal-organic framework material is UiO-66-NH-AA.

6. The method for preparing an interfacially covalently constructed MOF composite electrolyte thin film according to claim 5, characterized in that, The preparation of the polymer matrix formed by polymerizing imidazole zwitterionic monomers includes: 6-(1-imidazolyl)-1-hexanol monomer was synthesized from imidazole via quaternization reaction; The monomer 6-(1-imidazolyl)-1-hexanol was reacted with sodium tribromopropane sulfonate to synthesize 1,3-bis(6-hydroxyhexyl)imidazolylpropane sulfonate monomer; The 1,3-bis(6-hydroxyhexyl)imidazolium propane sulfonate monomer was esterified with acryloyl chloride, and the purified product was obtained as the target product, 1,3-bis(6-acryloyloxyhexyl)imidazolium propane sulfonate monomer.

7. The method for preparing an interfacially covalently constructed MOF composite electrolyte thin film according to claim 6, characterized in that, The molar ratio of 6-(1-imidazolyl)-1-hexanol monomer to sodium tribromopropane sulfonate is (1~1.2):1; the molar ratio of 1,3-bis(6-hydroxyhexyl)imidazolyl propane sulfonate monomer to acryloyl chloride is (1~1.3):

3.

8. The method for preparing an interfacially covalently constructed MOF composite electrolyte thin film according to claim 5, characterized in that, The preparation of the metal-organic framework material specifically includes: Zirconium chloride and 2-aminoterephthalic acid were dissolved in N,N-dimethylformamide containing concentrated hydrochloric acid, and UiO-66-NH2 powder was synthesized by a solvothermal method. UiO-66-NH2 powder was dispersed in dichloromethane, and acrylic anhydride was added to carry out an amidation reaction. Acryloyl groups were covalently grafted onto the amino groups on the surface of UiO-66-NH2 to obtain a functionalized filler UiO-66-NH-AA with polymerizable double bonds on the surface.

9. The method for preparing an interfacially covalently constructed MOF composite electrolyte thin film according to claim 8, characterized in that, The molar ratio of zirconium chloride to 2-aminoterephthalic acid is 1:(1.3-1.5); the volume ratio of N,N-dimethylformamide to concentrated hydrochloric acid is (4.5-5.5):1; when preparing UiO-66-NH-AA, the molar ratio of UiO-66-NH2 powder, acrylic anhydride, and dichloromethane is 1:(2.3-2.5):

126.

10. The application of the interfacial covalently constructed MOF composite electrolyte film as described in claim 1 or 2 in a flexible sensor, characterized in that, The interface covalently constructed MOF composite electrolyte film serves as a sensing layer and is disposed between the electrode layers.

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