Application of a metal ion-doped graphene oxide membrane in the catalytic synthesis of Schiff base

Abstract

The present invention discloses an application of a metal ion-doped graphene oxide membrane in the catalytic synthesis of Schiff bases. The metal ion-doped graphene oxide membrane comprises a graphene oxide membrane and metal ions loaded on the surface and between the layers of the graphene oxide membrane. The metal ions in the metal ion-doped graphene oxide membrane of the present invention induce the orientation of reactant molecules through cation-π interaction, and combined with the confinement channels formed between the metal ions and GO, the frontier molecular orbitals of the reactants for the catalytic synthesis of Schiff bases are more matched, reducing the molecular freedom degree, and enabling the molecules to undergo bond-breaking and bond-forming reactions in a specific orientation. The molecules are arranged orderly between the layers and flow through the two-dimensional nano-confinement channels provided by the graphene oxide nanosheets between the membrane layers, thereby reducing the reaction activation energy and achieving the efficient catalytic synthesis of various Schiff bases at room temperature. At the same time, by regulating the chemical microstructure of the membrane material, the catalytic reaction efficiency and reaction selectivity can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the application and technology field of membrane catalytic materials, and relates to the application of a metal ion-doped graphene oxide membrane in the catalytic synthesis of Schiff bases. Specifically, it relates to a graphene oxide membrane catalytic material with adjustable metal ion doping content, its preparation method, and its application in the rapid high-conversion catalytic synthesis of Schiff bases at room temperature. Background Art

[0002] Schiff base (English name: Schiff base, also known as Schiff's base, Seif's base, or Schiff base) is a type of imine compound with a carbon-nitrogen double bond, which is widely used in the fields of organic synthesis, functional dyes, energy catalysis, and biomedicine. The literature (J. Supercrit. Fluids 2018, 138, 221-227; Int. J. Org. Chem. 2014, 4, 7-15) reports that the formation mechanism of Schiff base compounds is that the lone pair electrons of the amino N atom in primary amines (such as aliphatic amines like ethylamine or aromatic amines like aniline) attack the carbonyl carbon atom in aldehyde or ketone molecules, undergoing a nucleophilic addition reaction to form an α-hydroxyamine intermediate, and then generating Schiff base compounds through a dehydration reaction.

[0003] To improve the reaction efficiency of Schiff base compounds, currently, the synthesis of Schiff bases usually uses Lewis acids (such as acetic acid, hydrochloric acid, alumina complexes, etc.) or Lewis bases (such as sodium tert-butoxide, sodium hydroxide, etc.) as catalysts (as reported in Chem. Sci. 2024, 15, 9582-9590; J. Mol. Catal. A: Chem. 2006, 260, 100-4; Tetrahedron: Asymmetry, 2007, 18, 2507-2509). However, since the synthesis reaction of Schiff bases is a reversible reaction and is affected by chemical equilibrium, the reaction still faces some challenges at present, such as a relatively high reaction temperature (50-150 °C), a relatively long reaction time (>2 h), and a relatively low reaction conversion rate at room temperature (50-80%) (as reported in the literature Chem. Sci. 2024, 15, 3872-3878; J. Mex. Chem. Soc. 2021, 65, 3, 376-395; Adv. Synth. Catal. 2023, 365, 4132-4137). In addition, the process of separating the catalyst from the product is relatively complex, and the crude product usually needs to be separated and purified by silica gel column chromatography, preparative liquid chromatography, or recrystallization. Due to the instability of the imine structure, the decomposition of Schiff bases may occur during the post-treatment process, which will increase the production cost, consume a large amount of reagents, and cause environmental pollution.

[0004] In addition to traditional catalytic methods, the microwave synthesis method, as a new method for synthesizing Schiff bases, although having advantages such as short reaction time and high reaction conversion rate, also faces problems such as high preparation cost, poor universality, and high operation risk coefficient. Summary of the Invention

[0005] In order to improve the above technical problems, the present invention provides an application of a metal ion-doped graphene oxide membrane in the catalytic synthesis of Schiff bases.

[0006] According to an embodiment of the present invention, the metal ion-doped graphene oxide membrane includes a graphene oxide membrane and metal ions loaded on the surface and between the layers of the graphene oxide membrane. Preferably, the metal ions are loaded on the surface and between the layers of the graphene membrane through oxygen-containing groups and graphite domains in the graphene oxide membrane.

[0007] According to an embodiment of the present invention, the metal ions include main group metal ions and transition metal ions, and may be, but are not limited to, Li + , Na + , K + , Mg 2+ , Ca 2+ , Al 3+ , Mn 2+ , Fe 3+ , Co 2+ , Ni 2+ , Cu 2+ and Zn 2+ and at least one of them.

[0008] According to an embodiment of the present invention, the thickness of the graphene oxide membrane is, for example, 0.2 - 10 μm, 0.3 - 8 μm, 0.5 - 6 μm, or 0.8 - 2 μm.

[0009] According to an embodiment of the present invention, the interplanar spacing of the metal ion-doped graphene oxide membrane is 0.8 - 1.6 nm.

[0010] According to an embodiment of the present invention, in the metal ion-doped graphene oxide membrane, the mass ratio of the metal ions is 0.01 - 10%.

[0011] According to an embodiment of the present invention, in the metal ion-doped graphene oxide membrane, the atomic ratio of oxygen to carbon is 0.3 - 0.6.

[0012] According to an embodiment of the present invention, the metal ion-doped graphene oxide membrane may contain a solvent, such as water.

[0013] According to an embodiment of the present invention, the metal ion-doped graphene oxide membrane is prepared by reacting a graphene oxide (GO) membrane with a metal salt.

[0014] According to an embodiment of the present invention, the metal salt includes compounds of main group metal ions and compounds of transition metal ions, and can be but not limited to LiCl, NaCl, KCl, MgCl 2 、CaCl 2 、AlCl 3 、MnCl 2 、FeCl 3 、CoCl 2 、NiCl 2 、CuCl 2 、ZnCl 2 。

[0015] In an embodiment of the present invention, the graphene oxide film comprises graphene oxide nanosheets with a layered structure.

[0016] In some embodiments of the present invention, the method for preparing the metal ion-doped graphene oxide film comprises the following steps: 1) Assembling a graphene oxide dispersion into a graphene oxide film by vacuum filtration; 2) Mixing the graphene oxide (denoted as GO) film with a metal salt solution to obtain a metal ion-doped graphene oxide (denoted as M-GO) film; 3) Optionally, heat-treating the film obtained in step 2) to obtain a metal ion-doped graphene oxide (denoted as T-M-GO) film.

[0017] In the present invention, by mixing the GO film with a metal salt solution, metal ions enter the interlayer of the GO film and are fixed by the oxygen-containing groups and graphite domains in the GO film.

[0018] According to an embodiment of the present invention, the graphene oxide is monolayer graphene oxide, and preferably the diameter of the graphene oxide nanosheets > 500 nm.

[0019] According to an embodiment of the present invention, the concentration of the graphene oxide dispersion is 0.01 - 2.5 mg / mL, and an example is 0.075 mg / mL.

[0020] In the present invention, in step 1), the graphene oxide dispersion is, for example, a graphene oxide aqueous dispersion. The GO aqueous dispersion is obtained, for example, by mixing GO (such as GO nanosheets) with water, stirring, and ultrasonic dispersion. For example, the stirring time is 10 - 20 min, the ultrasonic time is 5 - 15 min, and the ultrasonic power is 100 - 300 W to uniformly disperse the GO nanosheets without destroying the structure of the GO nanosheets.

[0021] In one embodiment of the present invention, the vacuum filtration method is specifically implemented as follows: Add the GO aqueous dispersion into a vacuum filtration flask, start the vacuum pump, and perform vacuum filtration (for example, the vacuum degree of vacuum filtration is 1-5 Pa); as the filtration progresses, the GO nanosheets in the GO aqueous dispersion are assembled into a layered structure under the action of water flow. After the filtration is completed, the GO film is obtained.

[0022] According to the embodiment of the present invention, the thickness of the GO film is, for example, 0.2-10 μm, 0.3-8 μm, 0.5-6 μm, or 0.8-2 μm.

[0023] According to the embodiment of the present invention, the concentration of the metal salt solution is 0.01-1.6 mol / L, preferably 0.5-1.0 mol / L, and for example, 0.01 mol / L, 0.1 mol / L, 0.2 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.75 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L.

[0024] According to the embodiment of the present invention, in step 2), the mixing can be soaking the GO film in the metal salt solution. The soaking time is, for example, 0.1 h-60 h, 2 h-48 h, or 4-26 h, and exemplarily, 4 h, 8 h, 24 h.

[0025] According to the embodiment of the present invention, step 2) also includes washing and drying the GO film with mixed metal ions. For example, the drying is carried out under conditions of a constant temperature (such as 20-40 °C) and a constant humidity (such as 5-30% RH), such as in a constant temperature and humidity chamber. Exemplarily, it is left standing for 6-12 h at 20-30 °C and 10-20% RH. The constant temperature and humidity standing treatment can remove some free water in the graphene oxide film after the filtration is completed.

[0026] According to the embodiment of the present invention, in step 3), the heat treatment time is 4-15 hours; the heat treatment temperature is 40-180 °C, preferably 40-100 °C, and for example, 40 °C, 50 °C, 60 °C, 80 °C, 100 °C. The heat treatment can promote the water loss process of the M-GO film, thereby regulating the interaction between metal ions and the oxygen-containing groups and graphite domains on the surface of GO, enhancing the induction effect of metal ions on reactant molecules, and improving the catalytic effect. Too low a treatment temperature is not conducive to promoting the water loss process of the M-GO film to regulate the interaction between ions and oxygen-containing groups and graphite domains; while too high a treatment temperature will cause thermal decomposition of the M-GO film, which is not conducive to maintaining the intrinsic chemical structure of the M-GO film.

[0027] In one embodiment of the present invention, the method for preparing the metal ion-doped graphene oxide film comprises the following steps:

[0028] 1) Disperse GO in water to obtain a GO aqueous dispersion; assemble the obtained GO aqueous dispersion into a GO film by vacuum filtration;

[0029] 2) Immerse the GO film obtained in step 1) in a metal salt solution, take it out after immersion and perform constant temperature and humidity treatment to obtain an M-GO film;

[0030] Optionally, 3) heat-treat the M-GO film obtained in step 2) to obtain a T-M-GO film.

[0031] According to the embodiment of the present invention, the application of the metal ion-doped graphene oxide film in catalyzing the formation of Schiff base from aldehyde-ketone compounds and primary amines. For example, the metal ion-doped graphene oxide film is used as a membrane reactor to catalyze the formation of Schiff base from aldehyde-ketone compounds and primary amines.

[0032] The present invention also provides a catalytic system containing the above metal ion-doped graphene oxide film.

[0033] The present invention also provides a method for catalytic synthesis of Schiff base using a metal ion-doped graphene oxide film, which includes reacting an aldehyde-ketone compound with a primary amine in the above catalytic system to prepare a Schiff base compound.

[0034] In the present invention, the product Schiff base will flow out with the mobile phase and separate from the catalytic system.

[0035] According to the embodiment of the present invention, the method for catalytic synthesis of Schiff base using the metal ion-doped graphene oxide film comprises the following steps:

[0036] a) Dissolve an aldehyde-ketone compound and a primary amine in an organic reagent to obtain a solution for membrane passing reaction;

[0037] b) At room temperature, drive by a pressure difference to make the solution for membrane passing reaction pass through the metal ion-doped graphene oxide film in the above catalytic system to carry out an acylation reaction.

[0038] In one embodiment of the present invention, in step a), the molar ratio of the aldehyde-ketone compound to the primary amine is 1:0.9 to 1.2.

[0039] In one embodiment of the present invention, in step a), the organic solvent is acetonitrile.

[0040] In one embodiment of the present invention, in step a), the concentration of the aldehyde-ketone compound in the solution for membrane passing reaction is 0.01 to 5 mol / L.

[0041] In one embodiment of the present invention, in step b), the reaction time is about 2 to 20 s.

[0042] In one embodiment of the present invention, in step b), room temperature refers to a temperature range of 20 to 30 °C.

[0043] In one embodiment of the present invention, in step b), the pressure difference is greater than or equal to 0.8 atm.

[0044] In one embodiment of the present invention, in step b), the reaction conversion rate can reach up to ~100%.

[0045] In one embodiment of the present invention, the aldehyde-ketone compound can be selected from, for example, benzaldehyde, 4-methoxybenzaldehyde.

[0046] In one embodiment of the present invention, the primary amine can be selected from, for example, aniline, 2-cyanoaniline, 3-cyanoaniline, 3-nitroaniline.

[0047] Advantages of the present invention:

[0048] (1) The present invention provides a metal ion-doped graphene oxide membrane for use as a catalytic material in the efficient catalytic synthesis of Schiff bases. The metal ion-doped graphene oxide membrane of the present invention retains the inherent acidic catalytic sites of graphene oxide nanosheets while doping metal ions that can induce the orientation of reactants through cation-π interactions. At the same time, by regulating the chemical microstructure of the membrane material (such as the type of metal ions, the content of metal ions, and the heat treatment temperature of the membrane material), the catalytic reaction efficiency and reaction selectivity can be effectively improved.

[0049] (2) The metal ions in the metal ion-doped graphene oxide membrane of the present invention induce the orientation of reactant molecules through cation-π interactions, combined with the confinement channels formed between the metal ions and GO, making the frontier molecular orbitals of the reactants for the catalytic synthesis of Schiff bases more matched, reducing the molecular freedom, and enabling the molecules to undergo bond-breaking and bond-forming reactions in a specific orientation. The molecules are arranged orderly between the layers and flow through the two-dimensional nano-confinement channels provided by the graphene oxide nanosheets between the membrane layers, thereby reducing the reaction activation energy and achieving the efficient catalytic synthesis of various Schiff bases at room temperature.

[0050] (3) While retaining the inherent acidic catalytic sites of graphene oxide nanosheets, the metal ion-doped graphene oxide membrane catalytic material of the present invention is also doped with metal ions that can induce the orientation of reactants through cation-π interactions. Utilizing the two-dimensional nano-confined channels provided by graphene oxide nanosheets between the membrane layers and the synergistic effect of metal ions on the orientation induction of reactant molecules, the simultaneously generated water rapidly flows within the graphite domain in the channels and escapes from the reaction system, thereby promoting the forward progress of the reaction equilibrium. Combining the synergistic catalytic effect of acidic catalytic sites, under the driving force of a pressure difference, through a continuous flow reaction method, it exhibits a high catalytic efficiency at room temperature, with a higher reaction conversion rate (up to 100% at most), a significantly shortened reaction time (residence time < 20 s), and avoids the energy consumption and operation complexity brought about by high-temperature heating and long-time reactions. This room-temperature membrane catalytic system not only simplifies the synthesis steps of Schiff bases but also significantly improves the purity and yield of the products, provides a new path for the efficient and green synthesis of Schiff bases, and the products do not require separation and purification, being environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a schematic diagram of the preparation process of the metal ion-doped graphene oxide membrane catalytic material of the present invention and the catalytic synthesis reaction of Schiff bases;

[0052] Figure 2 It is the structure and catalytic performance characterization of the Mg-GO membrane. Among them: Figure 2 In (A), it is the X-ray diffraction (XRD) characterization results of the GO membrane (Comparative Example 7) and the Mg-GO membrane catalytic materials soaked in different Mg ion concentrations in the dry and wet states (the solvent is acetonitrile); Figure 2 In (B), it is the comparison of the infrared characterization results between the Mg-GO-1.0M membrane of Example 2 and the GO membrane of Comparative Example 7; Figure 2 In (C), it is the nuclear magnetic hydrogen spectrum of the substance passing through the Mg-GO membrane in Example 1; Figure 2 In (D), it is the comparison result diagram of the conversion rates of the confined catalytic synthesis of Schiff bases by metal salt + GO powder (Comparative Example 1), single metal salt bulk phase (Comparative Example 2), single GO powder (Comparative Example 3), and Mg-GO membrane (Example 1). DETAILED DESCRIPTION OF THE EMBODIMENTS

[0053] The technical solutions of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are only illustrative and explanatory of the present invention and should not be construed as limiting the protection scope of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0054] Unless otherwise specified, the raw materials and reagents used in the following embodiments are all commercially available products or can be prepared by known methods.

[0055] In the following examples and comparative examples, unless otherwise specified, "GO dispersion" refers to "graphene oxide dispersion".

[0056] In the following examples and comparative examples, unless otherwise specified, "GO film" refers to "graphene oxide film".

[0057] In the following examples and comparative examples, unless otherwise specified, "M-GO film" refers to "metal ion-doped graphene oxide film without heat treatment".

[0058] In the following examples and comparative examples, unless otherwise specified, "T-M-GO film" refers to "metal ion-doped graphene oxide film after heat treatment".

[0059] As Figure 1 shown, first, the GO dispersion was assembled into a GO film by vacuum filtration; then, through soaking in a metal salt solution, metal ions were loaded on the surface and between the layers of the GO film to obtain an M-GO film. Through heat treatment, the dehydration of the M-GO film was promoted to change the interaction between metal ions and the oxygen-containing groups and graphite domains inside the GO film, obtaining a T-M-GO film. By changing the heat treatment temperature, the catalytic performance of the metal ion-doped graphene oxide film can be optimized.

[0060] Quantitative analysis of the liquid collected through the film was carried out by nuclear magnetic resonance hydrogen spectrum to calculate the reaction conversion rate, which specifically included the following steps:

[0061] Take a part of the collected liquid and prepare a nuclear magnetic sample using deuterated reagent (DMSO). There are characteristic hydrogens in both the reactant and product molecules. There is a corresponding relationship between the characteristic hydrogens and the number of molecules. By calculating and comparing the integral areas of the singlets at different chemical shifts through singlet fitting, the corresponding molecular quantity ratio is calculated, and then the reaction conversion rate is calculated, where:

[0062]

[0063] Example 1

[0064] 1) Prepare a 0.075 mg / mL GO aqueous dispersion: Take 3 mg of GO and add it to 40 mL of deionized water, mechanically stir for 10 min, and ultrasonically disperse (200 W) in an ice-water bath for 5 min to obtain a brown transparent solution;

[0065] Prepare a 0.01 mol / L MgCl 2 solution: Weigh 38 mg of MgCl 2 , add it to 40 mL of deionized water, and mechanically stir for 10 min.

[0066] (2) The prepared GO dispersion was assembled into a GO film by vacuum filtration. After the water above the film was drained, the film was removed from the filtration device and immersed in 10 mL of 0.01 mol / L MgCl 2 solution for 24 h. After taking it out, the surface was rinsed with deionized water, placed in a petri dish, and placed in a thermostatic and humidified chamber at 25.0 °C and 15% RH for drying for 12 hours and then taken out for standby, named Mg-GO-0.01M; Inductively coupled plasma optical emission spectrometry (ICP-OES) data showed that the Mg 2+ content in the Mg-GO-0.01M film was 1.4 μmol; X-ray diffraction data showed that the interlayer spacing of the Mg-GO-0.01M film in acetonitrile solution was about

[0067] (3) Using the Mg-GO-0.01M film as a catalyst to catalyze the reaction of benzaldehyde and aniline to form Schiff base, the specific operation is as follows: The Mg-GO-0.01M film was purged with nitrogen to remove surface dust, and then a flat and smooth part was selected and cut into a regular octagon (side length 0.8 cm), and then purged with nitrogen again, fixed and equipped with a sealing gasket to ensure its sealing in the microfiltration device; Subsequently, the reaction solution was prepared: 2 mmol of benzaldehyde and 2 mmol of aniline were dissolved in 25 mL of acetonitrile to prepare the reaction solution, which was prepared immediately before use; 15 mL of the above reaction solution was added above the microfiltration device, and under the driving of the pressure difference (∼0.9 atm), the reaction solution passed through the interlayer two-dimensional nano-confined channel of the Mg-GO-0.01M film reactor, the reactants reacted between the layers, and the products flowed out with the acetonitrile solvent; The reaction temperature was 22.3 ± 0.1 °C, and the residence time of the reactants was about 7 s.

[0068] Use 1 1H NMR spectrum to analyze the components and calculate the reaction conversion rate to be 100%.

[0069] Comparative Example 1

[0070] Prepare a 0.075 mg / mL GO aqueous dispersion containing Mg 2+ in advance: Take 3 mg of GO and add it to 40 mL of deionized water, add 14 μL of 0.1 mol / L MgCl 2 solution, mechanically stir for 10 min, and ultrasonically disperse (200 W) in an ice-water bath for 5 min to obtain a brown transparent solution; Transfer to a petri dish and place it in a 25 °C vacuum oven for vacuum evaporation for 48 h to obtain Mg-GO powder;

[0071] Prepare the reaction solution: Dissolve 2 mmol of benzaldehyde and 2 mmol of aniline in 25 mL of acetonitrile to obtain the reaction solution, which is prepared freshly before use; Take 5 mL of the above reaction solution, add the above Mg-GO powder, maintain mechanical stirring, and take 0.5 mL of the sample from the above reaction system 48 h after the start of the reaction, add the deuterated reagent DMSO, and use 1 1H NMR spectroscopy to analyze the components and calculate the reaction conversion rate, and the reaction conversion rate is 68%.

[0072] Comparative Example 2

[0073] Prepare the reaction solution: Dissolve 2 mmol of benzaldehyde and 2 mmol of aniline in 25 mL of acetonitrile to obtain the reaction solution; Take 5 mL of the above reaction solution and add 0.2 mg of MgCl 2 solid, maintain mechanical stirring, take 0.5 mL of the sample from the above reaction solution 48 h after the start of the reaction, add the deuterated reagent DMSO, and use 1 1H NMR spectroscopy to analyze the components and calculate the reaction conversion rate, and the reaction conversion rate is 55%.

[0074] Comparative Example 3

[0075] Prepare a 0.075 mg / mL aqueous GO solution in advance: Take 3 mg of GO and add it to 40 mL of deionized water, stir mechanically for 10 min, disperse it by ultrasonic wave (200 W) in an ice-water bath for 5 min to obtain a brown transparent solution; Transfer it to a petri dish and place it in a vacuum oven at 25 °C for vacuum evaporation for 48 h to obtain GO powder;

[0076] Prepare the reaction solution: Dissolve 2 mmol of benzaldehyde and 2 mmol of aniline in 25 mL of acetonitrile to obtain the reaction solution, which is prepared freshly before use; Take 5 mL of the above reaction solution, add the above GO powder, maintain mechanical stirring, and take 0.5 mL of the sample from the above reaction system 48 h after the start of the reaction, add the deuterated reagent DMSO, and use 1 1H NMR spectroscopy to analyze the components and calculate the reaction conversion rate, and the reaction conversion rate is 75%.

[0077] Example 2

[0078] (1) Prepare a 0.075 mg / mL aqueous GO solution: Take 3 mg of GO and add it to 40 mL of deionized water, stir mechanically for 10 min, disperse it by ultrasonic wave (200 W) in an ice-water bath for 5 min to obtain a brown transparent solution;

[0079] Prepare a 1.0 mol / L MgCl 2 solution: Weigh 3796 mg of MgCl 2 , add it to 40 mL of deionized water, and stir mechanically for 10 min.

[0080] (2) The prepared GO dispersion was assembled into a GO film by vacuum filtration. After the water above the film was drained, the film was removed from the filtration device and immersed in 10 mL of 1.0 mol / L MgCl 2 solution for 24 h. After taking it out, the surface was rinsed with deionized water, placed in a petri dish, and placed in a thermo-hygrostat at 25.0 °C and 15% RH for drying for 12 h and then taken out for standby, named Mg-GO-1.0M; Inductively coupled plasma optical emission spectrometry (ICP-OES) data showed that the Mg 2+ content in the Mg-GO-1.0M film was 17.9 μmol; X-ray diffraction data showed that the interlayer spacing of the Mg-GO-1.0M film in acetonitrile solution was about

[0081] (3) Using the Mg-GO-1.0M film as a catalyst, the reaction of 4-methoxybenzaldehyde and 2-cyanoaniline to form Schiff base was catalyzed. The specific operation was as follows: The Mg-GO-1.0M film was purged with nitrogen to remove surface dust, and then a flat and smooth part was selected and cut into a regular octagon (side length 0.8 cm), and then purged with nitrogen again, fixed and equipped with a sealing gasket to ensure its sealing in a micro-filtration device; Subsequently, the reaction solution was prepared: 2 mmol of 4-methoxybenzaldehyde and 2 mmol of 2-cyanoaniline were dissolved in 25 mL of acetonitrile to prepare the reaction solution, which was prepared immediately before use; 15 mL of the above reaction solution was added above the micro-filtration device. Driven by the pressure difference (~0.9 atm), the reaction solution passed through the interlayer two-dimensional nano-confined channels of the Mg-GO-1.0M film reactor, and the reactants reacted between the layers, and the products flowed out with the acetonitrile solvent; The reaction temperature was 22.3 ± 0.1 °C, and the residence time of the reactants was about 13 s.

[0082] The composition was analyzed by 1 H NMR spectrum, and the reaction conversion rate was calculated to be 95%.

[0083] Comparative Example 4

[0084] A 0.075 mg / mL GO aqueous solution containing Mg 2+ was prepared in advance: 3 mg of GO was added to 40 mL of deionized water, 17.9 μL of 1.0 mol / L MgCl 2 solution was added thereto, mechanically stirred for 10 min, and ultrasonically dispersed (200 W) in an ice-water bath for 5 min to obtain a brown transparent solution; transferred to a petri dish and placed in a 25 °C vacuum oven for vacuum evaporation for 48 h to obtain Mg-GO powder;

[0085] Prepare the reaction solution: Dissolve 2 mmol of 4-methoxybenzaldehyde and 2 mmol of 2-cyanoaniline in 25 mL of acetonitrile to prepare the reaction solution, which is prepared immediately before use. Take 5 mL of the above reaction solution, add the above Mg-GO powder, maintain mechanical stirring, and take 0.5 mL of the sample from the above reaction system 48 h after the start of the reaction, add the deuterated reagent DMSO, and use 1 1H NMR spectroscopy to analyze the components and calculate the reaction conversion rate, and the reaction conversion rate is 7.4%.

[0086] Comparative Example 5

[0087] Prepare a 0.075 mg / mL aqueous solution of GO in advance: Take 3 mg of GO and add it to 40 mL of deionized water, stir mechanically for 10 min, and ultrasonically disperse it in an ice-water bath (200 W) for 5 min to obtain a brown transparent solution; transfer it to a petri dish and place it in a vacuum oven at 25 °C for vacuum evaporation for 48 h to obtain GO powder;

[0088] Prepare the reaction solution: Dissolve 2 mmol of 4-methoxybenzaldehyde and 2 mmol of 2-cyanoaniline in 25 mL of acetonitrile to prepare the reaction solution, which is prepared immediately before use. Take 5 mL of the above reaction solution, add the above GO powder, maintain mechanical stirring, and take 0.5 mL of the sample from the above reaction system 48 h after the start of the reaction, add the deuterated reagent DMSO, and use 1 1H NMR spectroscopy to analyze the components and calculate the reaction conversion rate, and the reaction conversion rate is 28%.

[0089] Comparative Example 6

[0090] Prepare the reaction solution: Dissolve 2 mmol of 4-methoxybenzaldehyde and 2 mmol of 2-cyanoaniline in 25 mL of acetonitrile to prepare the reaction solution. Take 5 mL of the above reaction solution and add 1.7 mg of MgCl 2 solid, maintain mechanical stirring, take 0.5 mL of the sample from the above reaction solution 48 h after the start of the reaction, add the deuterated reagent DMSO, and use 1 1H NMR spectroscopy to analyze the components and calculate the reaction conversion rate, and the reaction conversion rate is 7%.

[0091] Comparative Example 7

[0092] (1) Prepare a 0.075 mg / mL aqueous solution of GO: Take 3 mg of GO in 40 mL of deionized water, stir mechanically for 10 min, and ultrasonically disperse it in an ice-water bath (200 W) for 5 min to obtain a brown transparent solution.

[0093] (2) The prepared GO dispersion liquid above was assembled into a GO film by vacuum filtration. After the water above the film was dried by suction, the film was removed from the filtration device, placed in a petri dish, and placed in a constant temperature and humidity chamber at 25.0 °C and 15% RH for drying for 12 hours and then taken out for standby, named GO film; X-ray diffraction data showed that the interlayer spacing of the GO film in acetonitrile solution was about

[0094] (3) Using the GO film as a catalyst, catalyze the reaction of 4-methoxybenzaldehyde and 2-cyanoaniline to form Schiff base. The specific operation is as follows: The GO film was purged with nitrogen to remove surface dust, and then a flat and smooth part was selected and cut into a regular octagon (side length 0.8 cm), and purged with nitrogen again. It was fixed and equipped with a sealing gasket to ensure its sealing in a microfiltration device; Subsequently, the reaction solution was prepared: 2 mmol of 4-methoxybenzaldehyde and 2 mmol of 2-cyanoaniline were dissolved in 25 mL of acetonitrile to prepare the reaction solution, which was prepared and used immediately; 15 mL of the above reaction solution was added above the microfiltration device. Driven by the pressure difference (∼0.9 atm), the reaction solution passed through the interlayer two-dimensional nano-confined channels of the GO film reactor, and the reactants reacted between the layers, and the products flowed out with the acetonitrile solvent; The reaction temperature was 22.3 ± 0.1 °C, and the residence time of the reactants was about 3 s.

[0095] Use 1 1H NMR spectrum to analyze the composition and calculate the reaction conversion rate to be 74%.

[0096] Example 3

[0097] (1) Prepare a 0.075 mg / mL GO aqueous solution: Take 3 mg of GO and add it to 40 mL of deionized water, mechanically stir for 10 min, and ultrasonically disperse (200 W) in an ice-water bath for 5 min to obtain a brown transparent solution;

[0098] Prepare a 0.9 mol / L MgCl 2 solution: Weigh 3416 mg of MgCl 2 , add it to 40 mL of deionized water, and mechanically stir for 10 min.

[0099] (2) The prepared GO dispersion liquid above was assembled into a GO film by vacuum filtration. After the water above the film was dried by suction, the film was removed from the filtration device, immersed in 10 mL of 0.9 mol / L MgCl 2 solution for 24 h. After taking it out, rinse the surface with deionized water, place it in a petri dish, and place it in a constant temperature and humidity chamber at 25.0 °C and 15% RH for drying for 12 hours and then taken out for standby, named Mg-GO-0.9M-24h; Inductively coupled plasma emission spectrometry (ICP-OES) data showed that Mg in the Mg-GO-0.9M-24h film 2+The content is 16.1 μmol; X-ray diffraction data shows that the interlayer spacing of the Mg-GO-0.9M-24h film in acetonitrile solution is about

[0100] (3) Using the Mg-GO-0.9M-24h film as a catalyst, the reaction of 4-methoxybenzaldehyde and 2-cyanoaniline to form Schiff base was carried out. The specific operation is as follows: The Mg-GO-0.9M-24h film was purged with nitrogen to remove surface dust. Then, a flat and smooth part was selected and cut into a regular octagon (side length 0.8 cm). It was purged with nitrogen again, fixed and equipped with a sealing gasket to ensure its sealing in a micro suction filtration device. Subsequently, the reaction solution was prepared: 2 mmol of 4-methoxybenzaldehyde and 2 mmol of 2-cyanoaniline were dissolved in 25 mL of acetonitrile to prepare the reaction solution, which was prepared freshly before use. 15 mL of the above reaction solution was added above the micro suction filtration device. Driven by the pressure difference (~0.9 atm), the reaction solution passed through the interlayer two-dimensional nano-confined channels of the Mg-GO-0.9M-24h film reactor, and the reactants reacted between the layers, and the products flowed out with the acetonitrile solvent. The reaction temperature was 22.3 ± 0.1 °C, and the residence time of the reactants was about 7 s.

[0101] Use 1 1H NMR spectrum to analyze the composition and calculate the reaction conversion rate to be 95%.

[0102] Example 4

[0103] (1) Prepare a 0.075 mg / mL GO aqueous solution: Take 3 mg of GO and add it to 40 mL of deionized water. Stir mechanically for 10 min and disperse it by ultrasonic wave (200 W) in an ice-water bath for 5 min to obtain a brown transparent solution;

[0104] Prepare a 0.9 mol / L MgCl 2 solution: Weigh 3416 mg of MgCl 2 , add it to 40 mL of deionized water, and stir mechanically for 10 min.

[0105] (2) The above-prepared GO dispersion was assembled into a GO film by vacuum filtration. After the water above the film was drained, the film was removed from the filtration device and immersed in 10 mL of 0.9 mol / L MgCl 2 solution for 4 h. After taking it out, rinse the surface with deionized water, place it in a petri dish, and place it in a constant temperature and humidity box at 25.0 °C and 15% RH for drying for 12 hours, and then take it out for standby, named Mg-GO-0.9M-4h; Inductively coupled plasma optical emission spectrometry (ICP-OES) data shows that Mg in the Mg-GO-0.9M-4h film 2+The content is 16.1 μmol; X-ray diffraction data shows that the interlayer spacing of the Mg-GO-0.9M-4h film in acetonitrile solution is about

[0106] (3) Using the Mg-GO-0.9M-4h film as a catalyst, the reaction of 4-methoxybenzaldehyde and 2-cyanoaniline to form Schiff base was carried out. The specific operation is as follows: The Mg-GO-0.9M-4h film was purged with nitrogen to remove surface dust. Then, a flat and smooth part was selected and cut into a regular octagon (side length 0.8 cm). It was purged with nitrogen again, fixed and equipped with a sealing gasket to ensure its sealing in a microfiltration device. Subsequently, the reaction solution was prepared: 2 mmol of 4-methoxybenzaldehyde and 2 mmol of 2-cyanoaniline were dissolved in 25 mL of acetonitrile to prepare the reaction solution, which was prepared freshly. 15 mL of the above reaction solution was added above the microfiltration device. Driven by the pressure difference (∼0.9 atm), the reaction solution passed through the interlayer two-dimensional nano-confined channels of the Mg-GO-0.9M-4h film reactor. The reactants reacted between the layers, and the products flowed out with the acetonitrile solvent. The reaction temperature was 22.3 ± 0.1 °C, and the residence time of the reactants was about 7 s.

[0107] Use 1 1H NMR spectrum to analyze the composition and calculate the reaction conversion rate to be 95%.

[0108] Example 5

[0109] (1) Prepare a 0.075 mg / mL GO aqueous solution: Take 3 mg of GO and add it to 40 mL of deionized water. Stir mechanically for 10 min and disperse it by ultrasonic treatment (200 W) in an ice-water bath for 5 min to obtain a brown transparent solution;

[0110] Prepare a 0.75 mol / L MgCl 2 solution: Weigh 2847 mg of MgCl 2 , add it to 40 mL of deionized water, and stir mechanically for 10 min.

[0111] (2) The above-prepared GO dispersion was assembled into a GO film by vacuum filtration. After the water above the film was drained, the film was removed from the filtration device and immersed in 10 mL of 0.75 mol / L MgCl 2 solution for 4 h. After taking it out, rinse the surface with deionized water, place it in a petri dish, and place it in a constant temperature and humidity chamber at 25.0 °C and 15% RH for drying for 12 hours, and then take it out for standby. It was named Mg-GO-0.75M; Inductively coupled plasma optical emission spectrometry (ICP-OES) data shows that the Mg 2+The content is 13.6 μmol; X-ray diffraction data shows that the interlayer spacing of the Mg-GO-0.75M film in acetonitrile solution is about

[0112] (3) Using the Mg-GO-0.75M film as a catalyst, catalyze the reaction of 4-methoxybenzaldehyde and 2-cyanoaniline to form Schiff base. The specific operation is as follows: Purge the Mg-GO-0.75M film with nitrogen to remove surface dust. Then select a flat and smooth part and cut it into a regular octagon (side length 0.8 cm). Purge it with nitrogen again, fix it and install a sealing gasket to ensure it is sealed in a microfiltration device. Subsequently, prepare the reaction solution: Dissolve 2 mmol of 4-methoxybenzaldehyde and 2 mmol of 2-cyanoaniline in 25 mL of acetonitrile to prepare the reaction solution, which is prepared and used immediately. Add 15 mL of the above reaction solution above the microfiltration device. Driven by the pressure difference (~0.9 atm), the reaction solution passes through the interlayer two-dimensional nano-confined channels of the Mg-GO-0.75M film reactor. The reactants react between the layers, and the products flow out with the acetonitrile solvent. The reaction temperature is 22.3 ± 0.1 °C, and the residence time of the reactants is about 8 s.

[0113] Use 1 1H NMR spectrum to analyze the composition and calculate the reaction conversion rate to be 95%.

[0114] Example 6

[0115] (1) Prepare a 0.075 mg / mL GO aqueous solution: Take 3 mg of GO and add it to 40 mL of deionized water. Stir mechanically for 10 min and disperse it by ultrasonic treatment (200 W) in an ice-water bath for 5 min to obtain a brown transparent solution;

[0116] Prepare a 0.5 mol / L MgCl 2 solution: Weigh 1898 mg of MgCl 2 , add it to 40 mL of deionized water, and stir mechanically for 10 min.

[0117] (2) Prepare and assemble a GO film by vacuum filtration method using the above-prepared GO dispersion. After the water above the film is drained, remove the film from the filtration device and immerse it in 10 mL of 0.5 mol / L MgCl 2 solution for 24 h. After taking it out, rinse the surface with deionized water, place it in a petri dish, and place it in a constant temperature and humidity box at 25.0 °C and 15% RH for drying for 12 hours, and then take it out for standby. Name it Mg-GO-0.5M; Inductively coupled plasma optical emission spectrometry (ICP-OES) data shows that the Mg 2+ content in the Mg-GO-0.5M film is 9.5 μmol; X-ray diffraction data shows that the interlayer spacing of the Mg-GO-0.5M film in acetonitrile solution is about

[0118] (3) Using Mg-GO-0.5M as the catalyst, the reaction of 4-methoxybenzaldehyde and 2-cyanoaniline to form Schiff base was carried out. The specific operation is as follows: The Mg-GO-0.5M film was purged with nitrogen to remove the surface dust. Then, a flat and smooth part was selected and cut into a regular octagon (side length 0.8 cm). It was purged with nitrogen again, fixed and equipped with a sealing gasket to ensure its sealing in the microfiltration device. Subsequently, the reaction solution was prepared: 2 mmol of 4-methoxybenzaldehyde and 2 mmol of 2-cyanoaniline were dissolved in 25 mL of acetonitrile to prepare the reaction solution, which was prepared freshly before use. 15 mL of the above reaction solution was added above the microfiltration device. Driven by the pressure difference (~0.9 atm), the reaction solution passed through the interlayer two-dimensional nano-confined channel of the Mg-GO-0.5M membrane reactor, and the reactants reacted in the interlayer, and the products flowed out with the acetonitrile solvent. The reaction temperature was 22.3 ± 0.1 °C, and the residence time of the reactants was about 16 s.

[0119] Use 1 1H NMR spectrum to analyze the components and calculate the reaction conversion rate to be 95%.

[0120] Example 7

[0121] (1) Prepare a 0.075 mg / mL GO aqueous solution: Take 3 mg of GO and add it to 40 mL of deionized water. Mechanically stir for 10 min and ultrasonically disperse (200 W) in an ice-water bath for 5 min to obtain a brown transparent solution;

[0122] Prepare a 0.01 mol / L MgCl 2 solution: Weigh 38 mg of MgCl 2 , add it to 40 mL of deionized water, and mechanically stir for 10 min.

[0123] (2) Prepare and assemble a GO film from the above-prepared GO dispersion by vacuum filtration. After the water above the film was drained, the film was removed from the filtration device and immersed in 10 mL of 0.01 mol / L MgCl 2 solution for 24 h. After taking it out, rinse the surface with deionized water, place it in a petri dish, and place it in a thermo-hygrostat at 25.0 °C and 15% RH for drying for 12 hours, and then take it out for standby. It was named Mg-GO-0.01M. Inductively coupled plasma optical emission spectrometry (ICP-OES) data showed that the Mg 2+ content in the Mg-GO-0.01M film was 1.4 μmol; X-ray diffraction data showed that the interlayer spacing of the Mg-GO-0.01M film in the acetonitrile solution was about

[0124] (3) Using the Mg-GO-0.01M membrane as a catalyst, the reaction of 4-methoxybenzaldehyde and 2-cyanoaniline to form Schiff base was catalyzed. The specific operation is as follows: The Mg-GO-0.01M membrane was purged with nitrogen to remove surface dust. Then, a flat and smooth part was selected and cut into a regular octagon (side length 0.8 cm). It was purged with nitrogen again, fixed and equipped with a sealing gasket to ensure its sealing in a microfiltration device. Subsequently, the reaction solution was prepared: 2 mmol of 4-methoxybenzaldehyde and 2 mmol of 2-cyanoaniline were dissolved in 25 mL of acetonitrile to obtain the reaction solution, which was prepared immediately before use. 15 mL of the above reaction solution was added above the microfiltration device. Driven by the pressure difference (~0.9 atm), the reaction solution passed through the interlayer two-dimensional nano-confined channels of the Mg-GO-0.01M membrane reactor. The reactants reacted in the interlayer, and the products flowed out with the acetonitrile solvent. The reaction temperature was 22.3 ± 0.1 °C, and the residence time of the reactants was about 5 s.

[0125] Use 1 H NMR spectrum to analyze the composition and calculate the reaction conversion rate to be 75%.

[0126] Example 8

[0127] (1) Prepare a 0.075 mg / mL GO aqueous solution: Take 3 mg of GO and add it to 40 mL of deionized water. Stir mechanically for 10 min and disperse it by ultrasonic wave (200 W) in an ice-water bath for 5 min to obtain a brown transparent solution.

[0128] Prepare a 0.1 mol / L MgCl 2 solution: Weigh 380 mg of MgCl 2 , add it to 40 mL of deionized water, and stir mechanically for 10 min.

[0129] (2) The above-prepared GO dispersion was assembled into a GO membrane by vacuum filtration. After the water above the membrane was drained, the membrane was removed from the filtration device and immersed in 10 mL of 0.1 mol / L MgCl 2 solution for 24 h. After taking it out, rinse the surface with deionized water, place it in a petri dish, and place it in a constant temperature and humidity box at 25.0 °C and 15% RH for drying for 12 hours and then take it out for standby, named Mg-GO-0.1M; Inductively coupled plasma optical emission spectrometry (ICP-OES) data showed that the Mg 2+ content in the Mg-GO-0.1M membrane was 2.5 μmol; X-ray diffraction data showed that the interlayer spacing of the Mg-GO-0.1M membrane in the acetonitrile solution was about

[0130] (3) Using the Mg-GO-0.1M membrane as a catalyst, the reaction of 4-methoxybenzaldehyde and aniline to form Schiff base was catalyzed. The specific operation is as follows: The Mg-GO-0.1M membrane was purged with nitrogen to remove surface dust. Then, a flat and smooth part was selected and cut into a regular octagon (side length 0.8 cm). It was purged with nitrogen again, fixed and equipped with a sealing gasket to ensure its sealing in the microfiltration device. Subsequently, the reaction solution was prepared: 2 mmol of 4-methoxybenzaldehyde and 2 mmol of aniline were dissolved in 25 mL of acetonitrile to prepare the reaction solution, which was prepared freshly before use. 15 mL of the above reaction solution was added above the microfiltration device. Driven by the pressure difference (~0.9 atm), the reaction solution passed through the interlayer two-dimensional nano-confined channel of the Mg-GO-0.1M membrane reactor, and the reactants reacted in the interlayer, and the products flowed out with the acetonitrile solvent. The reaction temperature was 22.3 ± 0.1 °C, and the residence time of the reactants was about 7 s.

[0131] Use 1 H NMR spectrum to analyze the components and calculate the reaction conversion rate to be 100%.

[0132] Example 9

[0133] (1) Prepare a 0.075 mg / mL GO aqueous solution: Take 3 mg of GO and add it to 40 mL of deionized water. Stir mechanically for 10 min and disperse it by ultrasonic wave (200 W) in an ice-water bath for 5 min to obtain a brown transparent solution.

[0134] Prepare a 0.75 mol / L MgCl 2 solution: Weigh 2847 mg of MgCl 2 , add it to 40 mL of deionized water, and stir mechanically for 10 min.

[0135] (2) The above-prepared GO dispersion was assembled into a GO membrane by vacuum filtration. After the water above the membrane was drained, the membrane was removed from the filtration device and immersed in 10 mL of 0.75 mol / L MgCl 2 solution for 4 h. After taking it out, rinse the surface with deionized water, place it in a petri dish, and place it in a constant temperature and humidity box at 25.0 °C and 15% RH for drying for 12 hours and then take it out for standby, named Mg-GO-0.75M; Inductively coupled plasma optical emission spectrometry (ICP-OES) data showed that the Mg 2+ content in the Mg-GO-0.75M membrane was 13.6 μmol; X-ray diffraction data showed that the interlayer spacing of the Mg-GO-0.75M membrane in the acetonitrile solution was about

[0136] (3) Using the Mg-GO-0.75M membrane as a catalyst, the reaction of 4-methoxybenzaldehyde and 3-cyanoaniline to form Schiff base was catalyzed. The specific operation is as follows: The Mg-GO-0.75M membrane was purged with nitrogen to remove surface dust. Then, a flat and smooth part was selected and cut into a regular octagon (side length 0.8 cm). It was purged with nitrogen again, fixed and equipped with a sealing gasket to ensure its sealing in a microfiltration device. Subsequently, the reaction solution was prepared: 2 mmol of 4-methoxybenzaldehyde and 2 mmol of 3-cyanoaniline were dissolved in 25 mL of acetonitrile to prepare the reaction solution, which was prepared immediately before use. 15 mL of the above reaction solution was added above the microfiltration device. Driven by the pressure difference (~0.9 atm), the reaction solution passed through the interlayer two-dimensional nano-confined channel of the Mg-GO-0.75M membrane reactor. The reactants reacted in the interlayer, and the products flowed out with the acetonitrile solvent. The reaction temperature was 22.3 ± 0.1 °C, and the residence time of the reactants was about 8 s.

[0137] Use 1 The composition was analyzed by 1H NMR spectrum, and the reaction conversion rate was calculated to be 99%.

[0138] Example 10

[0139] (1) Preparation of 0.075 mg / mL GO aqueous dispersion: 3 mg of GO was added to 40 mL of deionized water, mechanically stirred for 10 min, and ultrasonically dispersed (200 W) in an ice-water bath for 5 min to obtain a brown transparent solution;

[0140] Preparation of 0.01 mol / L MgCl 2 solution: 38 mg of MgCl 2 was weighed and added to 40 mL of deionized water, and mechanically stirred for 10 min.

[0141] (2) The above-prepared GO dispersion was assembled into a GO membrane by vacuum filtration. After the water above the membrane was drained, the membrane was removed from the filtration device and immersed in 10 mL of 0.01 mol / L MgCl 2 solution for 24 h. After taking out, it was rinsed with deionized water on the surface, placed in a petri dish, and placed in a constant temperature and humidity chamber at 25.0 °C and 15% RH for drying for 12 hours and then taken out for standby, named Mg-GO-0.01M; Inductively coupled plasma optical emission spectrometry (ICP-OES) data showed that the Mg 2+ content in the Mg-GO-0.01M membrane was 1.4 μmol; X-ray diffraction data showed that the interlayer spacing of the Mg-GO-0.01M membrane in acetonitrile solution was about

[0142] (3) Using the Mg-GO-0.01M membrane as a catalyst, catalyze the reaction of 4-methoxybenzaldehyde and 3-nitroaniline to form Schiff base. The specific operation is as follows: Purge the Mg-GO-0.01M membrane with nitrogen to remove surface dust. Then select a flat and smooth part and cut it into a regular octagon (side length 0.8 cm). Purge it with nitrogen again, fix it and install a sealing gasket to ensure its sealing in a microfiltration device. Subsequently, prepare the reaction solution: Dissolve 2 mmol of 4-methoxybenzaldehyde and 2 mmol of 3-nitroaniline in 25 mL of acetonitrile to obtain the reaction solution, which is prepared and used immediately. Add 15 mL of the above reaction solution above the microfiltration device. Driven by the pressure difference (~0.9 atm), the reaction solution passes through the interlayer two-dimensional nano-confined channel of the Mg-GO-0.01M membrane reactor. The reactants react in the interlayer, and the products flow out with the acetonitrile solvent. The reaction temperature is 22.3 ± 0.1 °C, and the residence time of the reactants is about 8 s.

[0143] Use 1 Analyze the components by 1H NMR spectrum and calculate the reaction conversion rate to be 87%.

[0144] Example 11

[0145] (1) Prepare a 0.075 mg / mL GO aqueous solution: Take 3 mg of GO and add it to 40 mL of deionized water. Mechanically stir for 10 min, and ultrasonically disperse (200 W) in an ice-water bath for 5 min to obtain a brown transparent solution.

[0146] Prepare a 0.01 mol / L MgCl 2 solution: Weigh 38 mg of MgCl 2 , add it to 40 mL of deionized water, and mechanically stir for 10 min.

[0147] (2) Prepare and assemble a GO membrane by vacuum filtration method using the above-prepared GO dispersion. After the water above the membrane is drained, remove the membrane from the filtration device and soak it in 10 mL of 0.01 mol / L MgCl 2 solution for 24 h. After taking it out, rinse the surface with deionized water, place it in a petri dish, and place it in a thermo-hygrostat at 25.0 °C and 15% RH for drying for 12 hours to obtain Mg-GO-0.01M. Transfer the Mg-GO-0.01M membrane to a vacuum oven and heat-treat it at 60 °C under vacuum for 12 h, then take it out and set it aside, named T-Mg-GO-0.01M; Inductively coupled plasma optical emission spectrometry (ICP-OES) data shows that the Mg 2+ content in the T-Mg-GO-0.01M membrane is 1.4 μmol; X-ray diffraction data shows that the interlayer spacing of the T-Mg-GO-0.01M membrane in acetonitrile solution is about

[0148] (3) The T-Mg-GO-0.01M membrane was used as a catalyst to catalyze the reaction of 4-methoxybenzaldehyde and 3-nitroaniline to form a Schiff base. The specific operation was as follows: the T-Mg-GO-0.01M membrane was purged with nitrogen to remove the dust on the surface, and then the flat and smooth part was selected and cut into a regular octagon (side length 0.8 cm), and then purged with nitrogen again. It was fixed and a sealing gasket was installed to ensure that it was sealed in the micro-filtration device; then the reaction solution was prepared: 2 mmol 4-methoxybenzaldehyde and 2 mmol 3-Nitroaniline was dissolved in 25 mL of acetonitrile to prepare a reaction solution, which was prepared on demand. 15 mL of the reaction solution was added above a micro-filtration device. Driven by a pressure difference (~0.9 atm), the reaction solution passed through the interlayer two-dimensional nano-confined channels of the T-Mg-GO-0.01M membrane reactor, and the reactants reacted in the interlayers, and the products flowed out with the acetonitrile solvent. The reaction temperature was 22.3±0.1°C, and the residence time of the reactants was about 6 s.

[0149] use 1 The components were analyzed by H NMR spectroscopy, and the reaction conversion was calculated to be 98%.

[0150] like Figure 1 As shown, the prepared GO dispersion is assembled into a GO membrane by vacuum filtration, and the metal ions are loaded inside the GO membrane by immersion in a metal salt solution to obtain an M-GO membrane. The M-GO membrane is dehydrated by heat treatment to obtain a TM-GO membrane. The M-GO and TM-GO membranes are used as membrane reactors to catalyze aldehydes and ketones and primary amines to form Schiff bases. The reaction solution permeates through the M-GO membrane and the TM-GO membrane under the drive of pressure difference. The intrinsic acidic functional groups of the GO nanosheets and the doped metal ions catalyze the reaction of aldehydes and ketones and primary amines in the confined channels between the membrane layers, and the product Schiff base flows out of the membrane system with the solvent. Specifically, the GO nanosheets provide intrinsic acidic catalytic sites, the nano-confinement between the M-GO membrane and the TM-GO membrane reduces the freedom of the reactant molecules, and the interlayer metal ions induce the orientation of the reactant molecules, enhance their orderliness, and reduce the activation energy of the reaction, thereby greatly improving the efficiency of Schiff base synthesis.

[0151] like Figure 2 As shown in A, the dry interlayer spacing of Mg-GO-0.01M (Example 1), Mg-GO-0.1M (Example 8), and Mg-GO-1.0M (Example 2) obtained by immersion for 24 h and the wet interlayer spacing in acetonitrile solvent show that as the Mg content in the immersion solution increases, the 2+ With the increase of ion concentration, the change of dry-wet interlayer spacing of Mg-GO membrane decreases.

[0152] like Figure 2 As shown in B, 1730cm -1 、1260cm -1and 1060 cm -1 The characteristic absorption peaks at are the stretching vibrations of the C=O, C-O-C, and C-O groups on the aromatic ring of graphene oxide. Compared with the GO film of Comparative Example 7, the intensities of the C-O and C=O absorption peaks of the Mg-GO film of Example 2 decreased, which is usually interpreted as evidence of the coordination of carboxylic acid groups with metal ions. At the same time, after doping with Mg 2+ , the relative stretching intensity of C-O-C decreased significantly, which is mainly due to the ring-opening reaction caused by Mg 2+ .

[0153] As shown in Example 1, the ammonolysis reaction of benzaldehyde and aniline was carried out in the Mg-GO-0.01M membrane reactor, and the proton nuclear magnetic resonance spectrum of the product is as shown in C of Figure 2 . The chemical shifts of the benzene ring hydrogens are located at 7.94 - 7.95 (2H) ppm, 7.52 - 7.55 (3H) ppm, 7.41 - 7.44 (2H) ppm, and 7.25 - 7.27 (3H) ppm, combined with the characteristic peak at 8.61 ppm in the non-benzene ring region, corresponding one by one to the product peaks; in addition, the characteristic peaks of the reactants benzaldehyde and aniline completely disappeared, and the reaction conversion rate was calculated to be 100%.

[0154] The comparison of the conversion rates of the Schiff base synthesis catalyzed by the metal salt + GO powder of Comparative Example 1, the single metal salt of Comparative Example 2, the single GO powder bulk phase of Comparative Example 3, and the Mg-GO membrane of Example 1 is shown in (D) of Figure 2 . It can be seen from the figure that the Schiff base synthesis catalyzed by the Mg-GO-0.01M membrane catalyst achieved rapid (reactant residence time ~ 7 s) and efficient (yield of 100%) material synthesis during the directional flow process compared with the bulk phase catalysis.

[0155] Compared with catalytic materials such as Lewis acids like alumina composites and sulfuric acid, Lewis bases like sodium hydroxide, and other zeolites and molecular sieves, the metal ion-doped graphene oxide membrane catalytic material of the present invention significantly improves the reaction efficiency, shortens the reaction time, and achieves a maximum conversion rate of 100% for Schiff base at room temperature.

[0156] In summary, the present invention provides a (T-)M-GO membrane catalytic material for catalytic synthesis of Schiff base, its preparation method and use. While retaining the inherent acidic catalytic sites of graphene oxide nanosheets, the (T-)M-GO membrane catalytic material is also doped with metal ions that can induce the orientation of reactants through cation-π interaction. By utilizing the two-dimensional nano-confined channels provided by graphene oxide nanosheets between the membrane layers and the induction effect of metal ions on the orientation of reactant molecules, and at the same time, the generated water can flow rapidly in the graphite domain and escape from the reaction system to promote the forward progress of the reaction equilibrium. Combining with the synergistic catalytic effect of acidic catalytic sites, under the drive of pressure difference, in the form of continuous flow-phase reaction, the efficient and rapid (time < 20 s) catalytic synthesis of Schiff base is realized at room temperature (22.3 ± 0.1 °C), the conversion rate of reactants can reach up to ~100%, and the product does not need to be separated and purified.

[0157] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. Application of a metal ion-doped graphene oxide film in catalytic synthesis of Schiff base; the metal ion-doped graphene oxide film comprises a graphene oxide film and metal ions loaded on the surface and between layers of the graphene oxide film; The metal ion is Mg 2+ , Ca 2+ At least one of; the thickness of the graphene oxide film is 0.2~10 μm; The interplanar spacing of the metal ion-doped graphene oxide film is between 0.8 and 1.6 nm; In the metal ion-doped graphene oxide film, the mass proportion of metal ions is 0.01-10%.

2. The use according to claim 1, characterized in that The thickness of the graphene oxide film is 0.8-2 μm.

3. The use according to claim 1, characterized in that The metal ion-doped graphene oxide film is prepared by reacting the graphene oxide film with a metal salt; The metal salts include MgCl2 and CaCl2.

4. The use according to any one of claims 1 to 3, characterized in that: The method for preparing the metal ion-doped graphene oxide film comprises the following steps: 1) assembling a graphene oxide dispersion into a graphene oxide film by vacuum filtration; 2) mixing the graphene oxide film with a metal salt solution to obtain a metal ion-doped graphene oxide film; 3) optionally, heat treating the film obtained in step 2).

5. The use according to claim 4, characterized in that In step 1), the graphene oxide dispersion is a graphene oxide aqueous dispersion; The thickness of the graphene oxide film obtained in step 1) is 0.2~10 μm.

6. The use according to claim 4, characterized in that In step 2), the concentration of the metal salt solution is 0.01-1.6 mol / L.

7. The use according to claim 4, characterized in that In step 2), the mixing is performed by immersing the graphene oxide film in a metal salt solution; the immersion time is 0.1 h to 60 h.

8. The use according to claim 4, characterized in that Step 2) also includes washing and drying the metal ion-doped graphene oxide film obtained after mixing; the drying is performed under conditions of constant temperature and constant humidity.

9. The use according to claim 8, characterized in that The constant temperature is 20-40°C; the constant humidity is 5-30%RH.

10. The use according to claim 4, characterized in that In step 3), the heat treatment time is 4 to 15 hours; the heat treatment temperature is 40 to 180°C.

11. The use according to any one of claims 1 to 3, characterized in that: The method for synthesizing Schiff base by catalysis of metal ion-doped graphene oxide film comprises reacting aldehyde ketone compound with primary amine in the metal ion-doped graphene oxide film to prepare Schiff base compound.

12. The use according to claim 11, characterized in that The steps include: a) dissolving an aldehyde or ketone compound and a primary amine in an organic reagent to obtain a transmembrane reaction solution; b) Driven by pressure difference at room temperature, the transmembrane reaction solution passes through the metal ion-doped graphene oxide membrane to carry out the acylation reaction.

13. The use according to claim 12, characterized in that The aldehyde and ketone compounds are selected from benzaldehyde and 4-methoxybenzaldehyde, and the primary amine is selected from aniline, 2-cyanoaniline, 3-cyanoaniline and 3-nitroaniline.

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