Crystalline supramolecular polymer, preparation thereof and application of crystalline supramolecular polymer in detection of amine steam

Abstract

The invention discloses a crystalline supramolecular polymer, preparation thereof and application of the crystalline supramolecular polymer in detection of amine steam. The crystalline supramolecular polymer is formed by self-assembly of an electron-rich host molecular cage (Cage) and an electron-deficient guest naphthalene diimide derivative (NDI-4 or NDI-8) through charge transfer interaction and pi-pi accumulation interaction. The preparation method comprises the two steps of synthesis of the naphthalimide derivative and co-crystallization of a subject and an object, and is simple in process and mild in condition. The crystalline supramolecular polymer has excellent gasochromic performance and has high selectivity and sensitivity to propylamine, isopropylamine and butylamine steam, the response time at the room temperature does not exceed 4 hours, and rapid and visual detection can be achieved through color change (from purple black to orange or brown) and / or reduction of absorption intensity at the position of 533 nm. The method enriches a supramolecular chemical research system, provides an efficient and low-cost amine steam detection scheme, and has wide application prospects in the fields of environmental monitoring, industrial safety and the like.

Description

Technical Field

[0001] This invention belongs to the field of supramolecular functional materials technology, specifically relating to a crystalline supramolecular polymer based on charge transfer interaction, its preparation method, and its application as a gas-induced color-changing sensing material in the detection of amine vapors (especially propylamine, isopropylamine, and butylamine). Background Technology

[0002] In the field of supramolecular chemistry, molecular cages, with their unique cavity structure, precise molecular recognition capabilities, and tunable physicochemical properties, have become one of the core directions in host-guest chemistry research. Developing novel molecular cage recognition systems not only helps deepen our understanding of host-guest interaction mechanisms but also further expands the application boundaries of supramolecular chemistry across multiple disciplines. Currently, molecular cages have achieved significant applications in several interdisciplinary fields, including supramolecular self-assembly, intelligent molecular machines, functional polymer preparation, optical sensing, targeted drug delivery systems, and highly selective separation materials, demonstrating particularly significant advantages and broad prospects in the construction of functionalized supramolecular polymers.

[0003] Molecular cages, with their controllable cavity size and excellent guest recognition properties, occupy a crucial position in modern supramolecular assembly systems. However, current research in this field largely focuses on the controllable assembly of solution-state soft materials, lacking systematic and in-depth exploration of the structural design and functional regulation of crystalline supramolecular materials. Compared to solution systems, crystalline materials possess higher stability, superior mechanical properties, and more clearly defined structural characterization, making them more suitable for practical applications.

[0004] Charge transfer interactions are one of the key driving forces for constructing functional supramolecular assemblies. However, how to utilize this force to construct well-defined, high-performance crystalline supramolecular polymers in the solid state and endow them with stimulus-responsiveness (such as gas-induced color change) remains a current technical challenge.

[0005] Amine compounds (such as propylamine, isopropylamine, and butylamine) are important chemical raw materials, but they can also be harmful pollutants. Developing rapid, convenient, and visualized amine vapor detection materials is of practical significance. Existing detection methods often rely on large instruments, which are complex to operate, costly, and unable to provide real-time on-site detection.

[0006] Therefore, developing a crystalline supramolecular polymer material with significant gas-induced color-changing properties, constructed through charge transfer based on a novel molecular cage, is of great significance for promoting the development of supramolecular functional materials and addressing the practical needs of amine vapor detection. Summary of the Invention

[0007] The primary objective of this invention is to provide a crystalline supramolecular polymer based on charge transfer interactions, which has a stable structure and exhibits significant gas-induced color-changing properties.

[0008] Another object of the present invention is to provide a method for preparing the above-mentioned crystalline supramolecular polymer, which is simple, controllable, and easy to obtain materials with good crystallinity.

[0009] Another objective of this invention is to provide the above-mentioned crystalline supramolecular polymer as a gas-induced colorimetric sensing material for the detection of amine vapors, particularly propylamine, isopropylamine, and butylamine vapors, thereby solving the technical problems of existing amine detection materials being time-consuming, expensive, and complex to operate, and achieving rapid, intuitive, and efficient identification of propylamine, isopropylamine, and butylamine.

[0010] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A crystalline supramolecular polymer is formed by the self-assembly of an electron-rich host molecular cage and an electron-deficient guest naphthalimide derivative through charge transfer interactions and π-π stacking.

[0011] The structural formula of the electron-rich host molecular cage is: This molecular cage is prepared by synthesizing intermediate molecular fragments via Friedel-Crafts reaction, followed by cyclization condensation reaction of paraformaldehyde with the intermediate molecules, exhibiting good crystallinity and electron-rich properties.

[0012] The electron-deficient guest is a naphthalimide derivative, NDI-4 or NDI-8, with the following structural formulas: NDI-4: ; NDI-8: ; Both NDI-4 and NDI-8 are electron-deficient systems, and both contain naphthalene functional groups in their electron-rich host molecular cages. They can form strong π-π stacking interactions, thereby achieving self-assembly through synergistic charge transfer interactions.

[0013] The molar ratio of the electron-rich host molecular cage to the electron-deficient guest naphthalimide derivative is 1:1, which ensures that the two can fully interact to form a structurally stable crystalline supramolecular polymer.

[0014] The preparation method of the above-mentioned crystalline supramolecular polymer includes the following steps: 1. Synthesis of electron-rich host molecular cages: a. 1,3,5-Tris(4-formylphenyl)benzene was reacted with the reducing agent NaBH4, followed by bromination with a mixed acid mixture of HBr and CH3COOH to obtain compound 1, whose structural formula is: The volume ratio of HBr to CH3COOH in the mixed acid is 1:2 to 1:5. The reduction reaction is carried out at room temperature for 20 to 40 minutes, and the bromination reaction is carried out under reflux and stirring at 50 to 70°C for 4 to 6 hours. b. Under aluminum chloride catalysis, compound 1 and 2,6-dimethoxynaphthalene were reacted in dichloromethane at room temperature with stirring for 10-20 min to carry out a Friedel-Crafts reaction, yielding compound 2, whose structural formula is: ; c. Under the catalysis of BF3·(OEt2), compound 2 and polyoxymethylene were reacted in 1,2-dichloroethane at room temperature with stirring for 8-12 min to carry out a cyclization condensation reaction, thereby obtaining an electron-rich host molecular cage.

[0015] 2. Preparation of electron-deficient guest naphthalimide derivatives: 1,4,5,8-naphthalenetetracarboxylic anhydride and an amine compound are added to dry dimethylformamide (DMF) at a molar ratio of 1:3 to form a suspension. Under an inert atmosphere, the suspension is heated to 120-140°C and stirred for 10-15 hours. After the reaction is complete, the mixture is cooled to room temperature, filtered under reduced pressure, and the filter cake is washed with distilled water to obtain a pink solid product, which is the naphthalenediimide derivative. When the amine compound is butylamine, the product is NDI-4; when the amine compound is octylamine, the product is NDI-8. Preferably, the inert atmosphere is nitrogen, and the reaction temperature is controlled at 130°C.

[0016] 3. Co-crystallization for the preparation of crystalline supramolecular polymers: The electron-rich host molecular cage (Cage) and the naphthalimide derivative (NDI-4 or NDI-8) prepared in step 1 were added to a round-bottom flask in a 1:1 molar ratio. Chloroform was added as a solvent, and the mixture was stirred until both molecules were completely dissolved. Acetonitrile, a poor solvent, was then added, with the volume of acetonitrile added being 1 / 30 to 1 / 20 of the volume of chloroform. The mixed solution was subjected to vacuum distillation, repeated three times to completely remove the solvent, inducing co-crystallization of the host and guest molecules to obtain a purplish-black solid crystalline powder, which is the target crystalline supramolecular polymer (denoted as Cage@NDI-4α and Cage@NDI-8α, respectively).

[0017] The above-mentioned crystalline supramolecular polymer is used as a gas-induced color-changing sensing material in the detection of amine vapors, specifically propylamine, isopropylamine, or butylamine vapors.

[0018] The specific detection method is as follows: After activating the crystalline supramolecular polymer under vacuum conditions, it is placed in the test atmosphere; the color change of the polymer is observed, and its absorption spectrum change in the visible light region can be detected simultaneously; if the polymer changes from purplish-black to orange or brown, and / or the absorption intensity near 533 nm decreases significantly, it indicates the presence of propylamine, isopropylamine, or butylamine vapor in the test atmosphere. The response time of the crystalline supramolecular polymer at room temperature is no more than 4 hours, resulting in high detection efficiency.

[0019] The beneficial effects of this invention are as follows: 1. This invention designs and synthesizes a crystalline supramolecular polymer constructed from a specific molecular cage and a naphthalimide derivative (NDI-4 or NDI-8) through strong charge transfer (CT) interactions and π-π stacking. This material exhibits good crystallinity, a well-defined structure, and high thermal stability.

[0020] 2. This crystalline supramolecular polymer exhibits excellent gas-induced color-changing properties, showing high selectivity and sensitivity to propylamine, isopropylamine, and butylamine vapors. The detection method is intuitive (color changes are visible to the naked eye), rapid, and inexpensive, requiring no complex detection instruments and enabling rapid on-site detection.

[0021] 3. The detection mechanism is clear. Characterization by PXRD, 1H NMR, and solid-state UV-Vis diffuse reflectance spectroscopy confirms that the adsorption of amine vapors alters the interaction between the host and guest, leading to a weakening of charge transfer and consequently causing color and spectral changes, which provides strong support for the reliability of the detection results.

[0022] 4. The preparation method provided by this invention is simple, and the target crystalline material can be obtained efficiently through solvent co-crystallization with good reproducibility. This invention provides an innovative approach for developing novel stimulus-responsive crystalline supramolecular materials, and has broad application prospects in fields such as chemical sensing, environmental monitoring, and food safety. Attached Figure Description

[0023] Figure 1 The 1H NMR spectrum of compound 1.

[0024] Figure 2 The 1H NMR spectrum of compound 2.

[0025] Figure 3 This is the hydrogen NMR spectrum of Cage.

[0026] Figure 4 The image shows the 1H NMR spectrum of the naphthalimide derivative NDI-4.

[0027] Figure 5 The image shows the 1H NMR spectrum of the naphthalimide derivative NDI-8.

[0028] Figure 6 This is the crystal structure diagram of Cage@NDI-4.

[0029] Figure 7 This is the crystal structure diagram of Cage@NDI-8.

[0030] Figure 8 This is the crystal structure of Cage.

[0031] Figure 9 PXRD patterns for Cage@NDI-4α: (I) PXRD simulated by crystal; (II) PXRD measured using Cage@NDI-4α.

[0032] Figure 10 Thermogravimetric analysis (TGA) plot of Cage@NDI-4α.

[0033] Figure 11 Thermogravimetric analysis (TGA) plot for Cage@NDI-8α.

[0034] Figure 12 The solid UV-Vis spectra of Cage, Cage@NDI-4α, and NDI-4 are shown.

[0035] Figure 13 The solid-state UV-Vis spectra of Cage, Cage@NDI-8α, and NDI-8 are shown.

[0036] Figure 14 Density functional theory (DFT) calculations were performed for: (a) NDI-4, (b) Cage@NDI-4α, (c) Cage, (d) Cage@NDI-8α, and (e) the frontier molecular orbitals of NDI-8 and the corresponding first band gap differences.

[0037] Figure 15 SEM image of the Cage@NDI-4α charge-transfer complex.

[0038] Figure 16 SEM image of the Cage@NDI-8α charge-transfer complex.

[0039] Figure 17 The image shows the gas-induced color change response of Cage@NDI-4α in propylamine, isopropylamine, and butylamine vapors.

[0040] Figure 18 The image shows the gas-induced color change response of Cage@NDI-8α in propylamine, isopropylamine, and butylamine vapors.

[0041] Figure 19 Solid-state UV-Vis diffuse reflectance spectra of propylamine, isopropylamine, and butylamine vapors adsorbed on Cage@NDI-4α, respectively.

[0042] Figure 20 Solid-state UV-Vis diffuse reflectance spectra of propylamine, isopropylamine, and butylamine vapors adsorbed on Cage@NDI-8α, respectively.

[0043] Figure 21 X-ray powder diffraction (PXRD) images of propylamine (a), isopropylamine (b), and butylamine (c) before and after adsorption by Cage@NDI-4α.

[0044] Figure 22 X-ray powder diffraction (PXRD) images of propylamine (a), isopropylamine (b), and butylamine (c) before and after adsorption by Cage@NDI-8α.

[0045] Figure 23 The 1H NMR shifts of propylamine (a), Cage@NDI-4α after propylamine adsorption (b), and Cage@NDI-4α (c) are compared.

[0046] Figure 24 The 1H NMR shifts of isopropylamine (a), Cage@NDI-4α after propylamine adsorption (b), and Cage@NDI-4α (c) are compared.

[0047] Figure 25 The 1H NMR shifts of butylamine (a), Cage@NDI-4α after propylamine adsorption (b), and Cage@NDI-4α (c) are compared.

[0048] Figure 26 The 1H NMR shifts of propylamine (a), Cage@NDI-8α after propylamine adsorption (b), and Cage@NDI-8α (c) are compared.

[0049] Figure 27 The 1H NMR shifts of isopropylamine (a), Cage@NDI-8α after propylamine adsorption (b), and Cage@NDI-8α (c) are compared.

[0050] Figure 28 The proton NMR shifts of butylamine (a), Cage@NDI-8α after adsorption of propylamine (b), and Cage@NDI-8α (c) are compared. Detailed Implementation

[0051] The present invention will be further described in detail below with reference to specific embodiments, so as to enable those skilled in the art to understand the present invention more clearly, but the scope of protection of the present invention is not limited to the following embodiments.

[0052] Example 1: Preparation of crystalline supramolecular polymer Cage@NDI-4α 1. Synthesis of the naphthalimide derivative NDI-4 In a 100 mL round-bottom flask, 1,4,5,8-naphthalenetetracarboxylic anhydride (0.30 g, 1.12 mmol) was suspended in dry N,N-dimethylformamide (DMF, 50 mL), and butylamine (0.25 g, 3.36 mmol) was added. Under nitrogen protection, the mixture was heated to 130 °C and stirred for 12 hours. After the reaction was complete, the mixture was cooled to room temperature, filtered under reduced pressure, and the filter cake was washed with distilled water and dried to give a pink solid product NDI-4 (0.52 g, 75% yield). 1 H NMR (400 MHz, CDCl3, 298K) δ (ppm): 8.75 (s, 4H), 4.20 (s, 4H), 1.73 (s, 4H), 1.47 (s, 4H), 0.99 (s, 6H). 2. Synthesis of novel molecular cages Step 1: Compound 1,3,5-tris(4-formylphenyl)benzene (2 g, 5.12 mmol) was added to a 250 mL round-bottom flask. After dissolving in CH3OH (20 mL) and CH2Cl2 (100 mL), NaBH4 (0.7 g, 18.5 mmol) was added to the solution. The mixture was stirred at room temperature for 30 minutes. After the reaction was complete, the solvent was evaporated under reduced pressure to obtain a pale yellow solid. CH3COOHHBr (100 mL) and HBr (30 mL) were added to the solid, and the mixture was heated to 60 °C and stirred under reflux for 5 hours. The reaction was then terminated with water. The suspension was extracted with CH2Cl2. The organic layer was neutralized to pH 7 with saturated NaHCO3 solution. The organic layer was washed with saturated NaCl solution, dried over anhydrous Na2SO4, and evaporated under reduced pressure to obtain a pale yellow solid, compound 1 (2.57 g, 86%). 1 H NMR (400 MHz, CDCl3, 298K) δ (ppm): 7.75 (s, 3H), 7.64 (s, 6H), 7.52 (s, 6H), 4.57 (s, 6H).

[0053] Step 2: In a 250 mL round-bottom flask, 2,6-dimethoxynaphthalene (3.22 g, 17.11 mmol), compound 1 (1 g, 0.54 mmol), and dry dichloromethane (DCM) were added. The mixture was stirred at room temperature for 15 minutes under the catalysis of aluminum chloride (AlCl3) (0.57 g, 4.28 mmol). The reaction was then terminated with water. The organic layer was washed with saturated sodium chloride solution and dried over anhydrous sodium sulfate (Na2SO4). The organic layer was filtered, and the solvent was evaporated under reduced pressure. The residue was purified by silica gel column chromatography (mobile phase: petroleum ether / DCM, ratio 6:1 to 3:2) to give compound 2 (0.63 g, 41%) as a white solid. 1 H NMR (400 MHz, CDCl3, 298 K) δ (ppm): 7.84 (s, 3H), 7.59 (s, 6H), 7.44 (s, 6H), 7.32 (s, 3H), 7.22 (s, 6H), 7.11 (s, 6H), 4.48 (s, 6H), 3.90 (d, J = 13.8 Hz, 18H).

[0054] Step 3: Compound 2 (0.2 g, 0.22 mmol), polyoxymethylene (0.06 g, 2.00 mmol), and dry Cl2CH2CH2Cl2 (100 mL) were mixed in a 250 mL round-bottom flask. Then, catalyst BF3·(OEt2) (0.5 mL, 4.00 mmol) was added, and the mixture was stirred at room temperature for 10 minutes. The reaction was quenched with water afterward. The organic layer was washed with saturated sodium chloride solution and dried over anhydrous Na2SO4. After filtration, the organic layer was evaporated under reduced pressure. The resulting residue was purified by silica gel column chromatography (mobile phase: petroleum ether / DCM, ratio 3:2 to 1:2) to give a white solid compound, Cage (56 mg, 14%). 1 H NMR (400 MHz, CDCl3, 298 K) δ (ppm): 8.36 (s, 6H), 7.93 (s, 6H), 7.31 (s, 6H), 7.16 (s, 36H), 4.89 (s, 6H), 4.38 (s, 12H), 3.98 (s, 18H), 3.84 (s, 18H).

[0055] 3. Preparation of crystalline supramolecular polymer Cage@NDI-4α Weigh 100 mg (0.054 mmol) of Cage and 20.45 mg (0.054 mol) of NDI-4 (molar ratio 1:1) into a 50 mL round-bottom flask, and add 30 mL of chloroform to dissolve them completely. Then, add 1 mL of acetonitrile (1 / 30 of the volume of chloroform) to the solution, and perform vacuum distillation, repeating this process three times to completely remove the solvent and induce co-crystallization. The final product, Cage@NDI-4α, is a purplish-black solid crystalline powder.

[0056] Example 2: Preparation of the crystalline supramolecular polymer Cage@NDI-8α 1. Synthesis of the naphthalimide derivative NDI-8 In a 100 mL round-bottom flask, 1,4,5,8-naphthalenetetracarboxylic anhydride (0.30 g, 1.12 mmol) was added and suspended in 50 mL of dry dimethylformamide (DMF), followed by octylamine (0.43 g, 3.36 mmol). Under nitrogen protection, the mixture was heated to 130 °C and stirred for 12 hours. After the reaction was complete, the mixture was cooled to room temperature, filtered under reduced pressure, and the filter cake was washed three times with distilled water to obtain a pink solid compound, NDI-8 (0.52 g, 75% yield). 1 H NMR (400 MHz, CDCl3, 298 K) δ (ppm): 8.75 (s, 4H), 4.19 (s, 4H), 1.74 (s, 4H), 1.27 (s, 20H), 0.87 (s, 6H). 2. Preparation of the crystalline supramolecular polymer Cage@NDI-8α Take Cage (100 mg, 0.054 mol, prepared as in Example 1) and NDI-8 (26.52 mg, 0.054 mol) (molar ratio 1:1) and place them in a 50 mL round-bottom flask. Add 30 mL of chloroform solution and stir until completely dissolved. Then add 1 mL of acetonitrile and perform vacuum distillation. Repeat three times to completely remove the solvent and induce co-crystallization to obtain a purplish-black solid crystalline powder, which is Cage@NDI-8α.

[0057] Example 3 Material structure characterization and performance testing 1. Characterization of the crystalline supramolecular polymer Cage@NDI-4α (1) Crystal structure: such as Figure 6 The image shows the crystal structure of Cage@NDI-4, which demonstrates how host and guest molecules interact through π-π stacking and charge transfer to form an ordered crystalline supramolecular structure. (2) PXRD analysis: such as Figure 9 As shown, the measured PXRD pattern of Cage@NDI-4α matches well with the simulated PXRD pattern of the crystal, indicating that the product has high crystallinity and is a pure phase crystal. (3) Thermal stability: such as Figure 10 As shown, TGA analysis results indicate that Cage@NDI-4α exhibits no significant mass loss below 303℃, demonstrating good thermal stability. (4) Spectral properties: such as Figure 12 As shown, a broad absorption band appears in the solid UV-Vis spectrum of Cage@NDI-4α, indicating that a charge transfer complex is formed between the host and guest components. (5) DFT calculation: such as Figure 14 As shown, DFT calculations indicate that there is a significant charge transfer interaction between Cage and NDI-4, and the first bandgap difference is consistent with the characteristics of a charge transfer complex. (6) Microscopic morphology: such as Figure 15 As shown, the SEM image reveals that Cage@NDI-4α exhibits a blocky structure with a regular morphology.

[0058] 2. Characterization of the crystalline supramolecular polymer Cage@NDI-8α (1) Crystal structure: such as Figure 7 The image shows the crystal structure of Cage@NDI-8, which demonstrates how host and guest molecules interact through π-π stacking and charge transfer to form an ordered crystalline supramolecular structure. (2) Thermal stability: such as Figure 11 As shown, TGA analysis results indicate that Cage@NDI-8α exhibits no significant mass loss below 337℃, demonstrating excellent thermal stability. (3) Spectral properties: such as Figure 13 As shown, a broad absorption band appears in the solid UV-Vis spectrum of Cage@NDI-8α, confirming the formation of the charge-transfer complex; (4) DFT calculation: such as Figure 14 As shown, DFT calculations indicate a strong charge transfer interaction between Cage and NDI-8; (5) Microscopic morphology: such as Figure 13 As shown, the SEM image reveals that Cage@NDI-8α exhibits a blocky structure with a regular morphology.

[0059] Example 4: Performance Test of Gas-Induced Color Changing Sensor 1. Gas-induced color change study of Cage@NDI-4α 5.00 mg of Cage@NDI-4α prepared in Example 1 was activated under vacuum for 2 hours and placed in a 5.00 mL open vial. The open vial was then placed into a 20.00 mL sealed vial containing 1.00 mL of propylamine, isopropylamine, and butylamine, respectively. The vials were left to stand at room temperature, and the color change was observed and the solid-state UV-Vis diffuse reflectance spectrum was detected.

[0060] Color changes: such as Figure 17 As shown, the activated Cage@NDI-4α changes color from purplish-black to orange and brown in propylamine, isopropylamine and butylamine vapors. This color change process is completed within 4 hours at room temperature and is clearly visible to the naked eye. Spectral changes: such as Figure 19 As shown, the solid-state UV-Vis diffuse reflectance spectrum reveals that after exposure to three amine vapors, the absorption intensity of Cage@NDI-4α near 533 nm is significantly reduced, indicating a weakening of charge transfer. Structural changes: such as Figure 21 As shown, the PXRD pattern of Cage@NDI-4α changed significantly after adsorbing amine vapor, confirming that the adsorption of amine molecules altered the interaction between the host and guest molecules. Mechanism verification: such as Figure 23-25 As shown, the 1H NMR spectroscopy results indicate that after adsorption of propylamine, isopropylamine, and butylamine, the H protons of NDI-4 underwent a significant high-field shift, while the H protons of propylamine, isopropylamine, and butylamine underwent a significant low-field shift. This suggests that the host-guest interaction between Cage and NDI-4 has changed. These results provide strong evidence for the adsorption mechanism of propylamine, isopropylamine, and butylamine.

[0061] 2. Gas-induced color change study of Cage@NDI-8α 5.00 mg of Cage@NDI-8α prepared in Example 5 was activated under vacuum for 2 hours and placed in a 5.00 mL open vial. The open vial was then placed into a 20.00 mL sealed vial containing 1.00 mL of propylamine, isopropylamine, and butylamine, respectively. The vials were left to stand at room temperature, and the color change was observed and the solid-state UV-Vis diffuse reflectance spectrum was detected.

[0062] Color changes: such as Figure 18 As shown, the activated Cage@NDI-8α changes color from purplish-black to brown in propylamine, isopropylamine and butylamine vapors. This color change process is completed within 4 hours at room temperature, and the color change is visually obvious. Spectral changes: such as Figure 20 As shown, the solid-state UV-Vis diffuse reflectance spectrum reveals that after exposure to propylamine, isopropylamine, and butylamine vapors, the absorption intensity of Cage@NDI-8α near 533 nm is significantly reduced, indicating a weakening of charge transfer. Structural changes: such as Figure 22 As shown, the PXRD pattern of Cage@NDI-8α after adsorbing amine vapors changed significantly, confirming the change in the adsorption of amine molecules and the host-guest interaction. Mechanism of action investigation: such as Figure 26-28 As shown, the 1H NMR spectroscopy results indicate that after adsorption of propylamine, isopropylamine, and butylamine, the H protons of NDI-8 underwent a significant high-field shift, while the H protons of propylamine, isopropylamine, and butylamine underwent a significant low-field shift. This suggests that the host-guest interaction between Cage and NDI-8 has changed. These results provide strong evidence for the adsorption mechanism of propylamine, isopropylamine, and butylamine.

[0063] In summary, this invention successfully constructed two novel crystalline supramolecular polymers, Cage@NDI-4α and Cage@NDI-8α. These polymers not only possess novel structures and good stability, but more importantly, they exhibit rapid, highly selective, and visually perceptible gas-induced color-changing responses to propylamine, isopropylamine, and butylamine vapors, making them promising new amine vapor sensing materials with significant application potential.

Claims

1. A crystalline supramolecular polymer, characterized in that, It is formed by the self-assembly of an electron-rich host molecular cage and an electron-deficient guest naphthalimide derivative through charge transfer interactions and π-π stacking interactions; The structural formula of the electron-rich host molecular cage is: ; The electron-deficient guest is a naphthalimide derivative, NDI-4 or NDI-8, with the following structural formulas: AND-4: ; AND-8: 。 2. The crystalline supramolecular polymer according to claim 1, characterized in that, The molar ratio of the electron-rich host molecular cage to the electron-deficient guest naphthalimide derivative is 1:

1.

3. A method for preparing a crystalline supramolecular polymer according to claim 1 or 2, characterized in that, Includes the following steps: (1) Synthesis of electron-rich host molecular cages: a. 1,3,5-Tris(4-formylphenyl)benzene was reacted with the reducing agent NaBH4, followed by bromination with a mixed acid mixture of HBr and CH3COOH to obtain compound 1, whose structural formula is: ; b. Compound 1 is reacted with 2,6-dimethoxynaphthalene in dichloromethane via a Friedel-Crafts reaction in the presence of a catalyst to give compound 2, whose structural formula is: ; c. In the presence of a catalyst, compound 2 is subjected to a cyclization condensation reaction with paraformaldehyde in 1,2-dichloroethane to obtain the electron-rich host molecular cage; (2) Synthesis of naphthalimide derivatives: 1,4,5,8-naphthalenetetracarboxylic anhydride and amine compounds are reacted in DMF under an inert atmosphere at 120-140℃, and the naphthalimide derivatives NDI-4 or NDI-8 are obtained by separation and purification; when the amine compound is butylamine, the product is NDI-4; when the amine compound is octylamine, the product is NDI-8. (3) Co-crystallization: The electron-rich host molecular cage and the naphthalimide derivative are dissolved in chloroform at a molar ratio of 1:

1. Acetonitrile, a poor solvent, is added. The solvent is removed by vacuum distillation to induce co-crystallization and obtain a purple-black solid crystal powder.

4. The preparation method according to claim 3, characterized in that, In step (1)a, the volume ratio of HBr to CH3COOH in the mixed acid is 1:2 to 1:5, the reduction reaction is carried out at room temperature for 20 to 40 min, and the bromination reaction is refluxed and stirred at 50 to 70 °C for 4 to 6 h; in step (1), the catalyst is aluminum chloride, and the Friedel-Crafts reaction is carried out at room temperature with stirring for 10 to 20 min; in step (1), the catalyst is BF3·(OEt2), and the cyclization condensation reaction is carried out at room temperature with stirring for 8 to 12 min.

5. The preparation method according to claim 3, characterized in that, In step (2), the molar ratio of 1,4,5,8-naphthalenetetracarboxylic anhydride to amine compounds is 1:

3.

6. The preparation method according to claim 4, characterized in that, In step (2), the volume of the undesirable solvent acetonitrile added is 1 / 30 to 1 / 20 of the volume of chloroform.

7. The application of the crystalline supramolecular polymer of claim 1 or 2 as a gas-induced color-changing sensing material in the detection of amine vapors.

8. The application according to claim 7, characterized in that, The amine vapor is propylamine, isopropylamine, or butylamine vapor.

9. The application according to claim 8, characterized in that, The detection method includes the following steps: activating the crystalline supramolecular polymer and exposing it to the test atmosphere; observing the color change of the crystalline supramolecular polymer and / or detecting the absorption spectrum change of the crystalline supramolecular polymer in the visible light region; if the crystalline supramolecular polymer changes from purplish-black to orange or brown, and / or the absorption intensity decreases near 533 nm, it indicates the presence of the amine vapor.

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