An electro-synthesis of 1-(2-pyridinyl)ethylamine

Abstract

The application discloses an electro-synthesis method of 1-(2-pyridine)ethylamine. The method comprises the following steps: performing electrolysis in an H-type electrolytic cell, a three-electrode system, a constant potential of-0.1 to-0.6 V vs. RHE for 2 to 6 hours to obtain 1-(2-pyridine)ethylamine; wherein the carbon paper loaded with PbCu / MXene is used as a working electrode, silver / silver chloride is used as a reference electrode, and a platinum sheet is used as a counter electrode; and a cathode electrolyte is an electrolyte solution containing a nitrogen source and a carbon source. In the application, the selectivity of PbCu / MXene to 1-(2-pyridine)ethylamine is 100%, and the conversion rate of the substrate 2-acetylpyridine is 98.3%.

Description

Technical Field

[0001] This invention belongs to the field of green electrosynthesis technology of high-value nitrogen-containing fine chemicals, specifically involving a green and efficient electrosynthesis method of 1-(2-pyridine)ethylamine based on MXene-supported PbCu bimetallic catalyst, using nitrogen oxides as nitrogen source, 2-acetylpyridine as carbon source, and water as hydrogen source. Background Technology

[0002] 1-(2-pyridine)ethylamine is a key synthetic unit for pharmaceuticals, functional dyes, and polymer intermediates, and is widely in demand in the fields of medicine, pesticides, coordination chemistry, and materials chemistry. Currently, the industrial synthesis of 1-(2-pyridine)ethylamine mainly employs high-temperature, high-pressure thermocatalytic amination, multi-step reduction, and hydroxylamine condensation routes. These methods rely on highly toxic or corrosive reagents such as hydroxylamine, hydrazine, and sodium borohydride, resulting in harsh reaction conditions, high energy consumption, and poor safety. Furthermore, the byproducts are complex and difficult to separate and purify, easily causing serious environmental pressure and resource waste.

[0003] Electrocatalytic synthesis, using electrons as a reducing agent and water as a proton source, allows for the control of multiple electron transfer steps at room temperature and atmospheric pressure, providing a sustainable pathway for the green construction of CN bonds and the resource utilization of nitrogen oxides. Recent studies have shown that electrocatalytic nitrogen oxide reduction reactions can generate hydroxylamine intermediates (*NH₂OH), which can spontaneously condense with carbonyl compounds to form oximes, followed by electrochemical hydrogenation to generate amine products. This provides a new approach for the electrosynthesis of fine chemicals. However, methods for the electrosynthesis of 1-(2-pyridine)ethylamine via CN coupling have not yet been reported. Furthermore, existing electrocatalytic CN coupling systems suffer from three major bottlenecks: First, the reduction pathway of nitrogen oxides is complex, easily leading to over-reduction to generate byproducts such as ammonia or competitive hydrogen evolution reactions, making it difficult to stably retain the key intermediate *NH2OH; second, the active sites have weak adsorption and activation capabilities for the carbonyl groups of organic substrates, resulting in low coupling efficiency with *NH2OH and a tendency for direct reduction to alcohol byproducts; third, traditional monometallic catalysts cannot simultaneously achieve nitrogen intermediate regulation, organic substrate activation, and tandem hydrogenation, while conventional bimetallic catalysts are prone to aggregation and have low active site coverage, greatly limiting the efficiency and selectivity of electrosynthesis. Therefore, developing a mild, simple, green, and sustainable synthetic method and designing a highly selective, high-conversion, and highly active catalyst is of great significance for the efficient synthesis of 1-(2-pyridine)ethylamine. Summary of the Invention

[0004] The purpose of this invention is to address the limitations of current technologies by providing an electrosynthetic method for 1-(2-pyridine)ethylamine. This method uses nitrogen oxides as the nitrogen source. Using acetylpyridine as the carbon source, an H-type electrochemical reactor was constructed with an MXene-supported PbCu bimetallic catalyst (PbCu / MXene) as the working electrode, a platinum sheet as the counter electrode, and silver / silver chloride as the reference electrode. Constant-potential electrolysis was performed at room temperature and atmospheric pressure to achieve the one-step electrosynthesis of 1-(2-pyridine)ethylamine. In this invention, the selectivity of PbCu / MXene for 1-(2-pyridine)ethylamine was 100%, and the conversion rate of the substrate 2-acetylpyridine was 98.3%.

[0005] The technical solution of this invention is as follows: An electrosynthetic method for 1-(2-pyridine)ethylamine, comprising the following steps: Electrolysis was performed for 2–6 hours in an H-type electrolytic cell using a three-electrode system and a constant potential of -0.1 to -0.6 V vs. RHE to obtain 1-(2-pyridine)ethylamine. Among them, carbon paper loaded with PbCu / MXene is used as the working electrode, silver / silver chloride is used as the reference electrode, and platinum sheet is used as the counter electrode; The cathode electrolyte is an electrolyte solution containing a nitrogen source and a carbon source; The concentration of the cathode electrolyte solution is 1~3 M; the electrolyte is one or more of sodium hydroxide, potassium hydroxide, potassium bicarbonate, potassium carbonate, sodium bicarbonate, sodium carbonate, sodium sulfate, potassium sulfate, and sodium perchlorate. The concentration of the nitrogen source is 0.1~0.5M, and the concentration of the carbon source is 0.01~0.03M; The nitrogen source is one or more of nitrogen oxides, sodium nitrite, potassium nitrite, sodium nitrate, potassium nitrate, ammonium nitrate, or lithium nitrate; the carbon source is 2-acetylpyridine. The concentration of the anolyte solution is 1~3 M; the electrolyte is one or more of sodium hydroxide, potassium hydroxide, potassium bicarbonate, potassium carbonate, sodium bicarbonate, sodium carbonate, sodium sulfate, potassium sulfate, and sodium perchlorate. The anolyte and the cathode electrolyte are the same; A Nafion 117 membrane is installed between the cathode chamber and the anode chamber.

[0006] The method for preparing the working electrode includes the following steps: (1) Under an argon atmosphere, Ti3AlC2MAX, PbCl2, CuCl2, NaCl and KCl were added to a mortar and ground for 20-30 minutes to obtain a mixed powder; The molar ratio of Ti3AlC2MAX, PbCl2, CuCl2, NaCl, and KCl is 1:1.5~3:1.5~3:2~4:2~4; (2) The prepared mixed powder was annealed in an argon atmosphere at a temperature of 700~800℃ for 24~36 hours, washed and then freeze-dried for 48~72 hours to obtain PbCu / MXene; (3) Disperse PbCu / MXene in a mixed solution, then sonicate for 0.5 to 1.5 hours to form ink, and finally drop the ink onto carbon paper and dry at room temperature to obtain the working electrode; In this mixture, 2-15 mg of PbCu / MXene is added to every 0.95 mL of the mixed solution; the mixed solution consists of anhydrous ethanol, deionized water and Nafion reagent in a volume ratio of 9:9:1. per 1 cm 2 Add 20-100 μL of ink to carbon paper; It should be further noted that the technical features corresponding to the above examples can be combined or substituted to form new technical solutions.

[0007] The essential features of this invention are: This invention develops an electrosynthesis method for 1-(2-pyridine)ethylamine based on a PbCu / MXene catalyst, wherein nitrate is electroreduced at Cu active sites to generate *NH2OH; 2-pyridine is adsorbed on Pb sites... Acetylpyridine spontaneously undergoes C–N coupling with in-situ generated NH2OH to generate 1-(2-pyridine)ethyl ketone oxime; the oxime intermediate is further electrochemically hydrogenated under the synergistic effect of active hydrogen and bimetal to generate 1-(2-pyridine)ethylamine.

[0008] Compared with the prior art, the present invention has the following beneficial effects: 1. The electrosynthesis method developed in this invention has mild reaction conditions and can be carried out at room temperature and normal pressure. At the same time, it does not require dangerous reducing agents and has the advantages of being green, safe and energy-efficient.

[0009] 2. This invention uses nitrate, a common pollutant in wastewater, as a nitrogen source, realizing the resource utilization of pollutants and conforming to the concept of green and sustainable development.

[0010] 3. The electrosynthesis method developed in this invention can reduce nitrates to NH2OH in situ without the need for prior preparation of NH2OH. Therefore, this method not only avoids the storage of NH2OH and the use of hazardous gases such as hydrogen, but also enables the one-step electrosynthesis of 1-(2-pyridine)ethylamine under mild conditions.

[0011] 4. PbCu / MXene enables precise segmented tandem catalysis, with Cu sites regulating the selective generation of *NH2OH and Pb sites activating 2 Acetylpyridine promotes the subsequent hydrogenation process of oxime, effectively improving the selectivity of 1-(2-pyridine)ethylamine.

[0012] 5. MXene support has excellent conductivity and large specific surface area, which can effectively inhibit the aggregation of PbCu bimetallic nanoparticles and enhance the stability and service life of the catalyst.

[0013] 6. Thanks to the tandem catalysis of the bimetallic active sites of PbCu and the support effect of MXene, PbCu / MXene exhibited nearly 100% selectivity, 98.3% conversion and 68.5% Faraday efficiency at an applied potential of -0.6 V vs. RHE, achieving efficient electrosynthesis of 1-(2-pyridine)ethylamine. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the reaction mechanism provided in Example 1.

[0015] Figure 2 The blank control experiment test diagram provided in Example 1.

[0016] Figure 3 The differential electrochemical mass spectra of the working electrode catalyst provided in Example 1 in different reactions; Figure 3 In Figure a, the differential electrochemical mass spectrum of the working electrode catalyst provided in Example 1 in the nitrate reduction reaction is shown. Figure 3 In Figure b, the differential electrochemical mass spectrum of the working electrode catalyst provided in Example 1 during the C–N coupling process is shown.

[0017] Figure 4 This is a scanning electron microscope image of the working electrode catalyst provided in Example 1.

[0018] Figure 5 This is a transmission electron microscope image of the working electrode catalyst provided in Example 1.

[0019] Figure 6 The X-ray photoelectron spectrum of the working electrode catalyst provided in Example 1 is shown below. Figure 6 a is the high-resolution Ti 2p XPS spectrum. Figure 6 b is the high-resolution Al 2p XPS spectrum. Figure 6 c is the high-resolution Pb 4f XPS spectrum. Figure 6 d is the high-resolution Cu 2p XPS spectrum.

[0020] Figure 7 The X-ray diffraction patterns are those of the working electrode catalysts provided in Examples 1, 2, and 3.

[0021] Figure 8This is a schematic diagram of the linear sweep voltammetry curves of the working electrode catalysts provided in Examples 1, 2, and 3 at different potentials.

[0022] Figure 9 This is a schematic diagram showing the selectivity and conversion rate of the working electrode catalysts provided in Examples 1, 2, and 3 at different potentials.

[0023] Figure 10 This is a schematic diagram of the Faraday efficiency of the working electrode catalysts provided in Examples 1, 2, and 3 at different potentials.

[0024] Figure 11 This is a schematic diagram showing the yield of the working electrode catalysts provided in Examples 1, 2, and 3 at different potentials.

[0025] Figure 12 The images show the 1H NMR spectra of the working electrode catalysts provided in Examples 1, 2, and 3 after electrolysis.

[0026] Figure 13 This is a graph showing the long-term cycling stability of the working electrode catalyst provided in Example 1.

[0027] Figure 14 This is a schematic diagram of the tandem catalytic mechanism of the working electrode catalyst provided in Example 1 during electrosynthesis. Detailed Implementation

[0028] The specific implementation steps and accompanying drawings of the present invention will be described in full and clearly below. It should be noted that the specific implementation of the present invention should not be considered limited to these descriptions. For those skilled in the art, other embodiments or inferences obtained without innovation should be considered to fall within the scope of protection of the present invention.

[0029] The Ti3AlC2 MAX (titanium aluminum carbide) involved in this invention is a known material and is commercially available. This invention uses the product of Jilin Yiyi Technology Co., Ltd., but is not limited thereto.

[0030] An electrochemical reactor was constructed using an H-type electrolytic cell with a three-electrode system. The H-type electrolytic cell includes a cathode chamber and an anode chamber, with a Nafion 117 membrane placed between the cathode and anode chambers. The three-electrode system includes a working electrode, a reference electrode, and a counter electrode. The working electrode is a PbCu / MXene loaded on carbon paper and located in the cathode chamber. The reference electrode is silver / silver chloride and located in the cathode chamber. The counter electrode is a platinum sheet and located in the anode chamber. A 1.0 M potassium bicarbonate cathode electrolyte containing 0.1 M potassium nitrate and 0.01 M 2-acetylpyridine is added to the cathode chamber. A 1.0 M potassium bicarbonate anolyte is added to the anode chamber.

[0031] Electrochemical synthesis process: Potassium nitrate and 2-acetylpyridine are added to the cathode chamber as nitrogen source and carbon source, respectively, and water in the electrolyte is used as proton source; then constant potential electrolysis is carried out in the cathode and anode chambers for 2 to 6 hours, with a potential range of -0.1 to -0.6 V vs. RHE. After electrolysis, an electrolyte containing 1-(2-pyridine)ethylamine is prepared in the cathode chamber.

[0032] The nitrogen source is one or a mixture of several of sodium nitrite, potassium nitrite, sodium nitrate, potassium nitrate, ammonium nitrate, or lithium nitrate, and is directly added to the cathode chamber as a nitrogen source.

[0033] The cathode electrolyte solution is one or more aqueous solutions selected from sodium hydroxide, potassium hydroxide, potassium bicarbonate, potassium carbonate, sodium bicarbonate, sodium carbonate, sodium sulfate, potassium sulfate, and sodium perchlorate. The anolyte solution is one or more aqueous solutions of sodium hydroxide, potassium hydroxide, potassium bicarbonate, potassium carbonate, sodium bicarbonate, sodium carbonate, sodium sulfate, potassium sulfate, and sodium perchlorate.

[0034] The cathode electrolyte is a 1-3 M sodium bicarbonate solution containing 0.1-0.5 M potassium nitrate and 0.01-0.05 M 2-acetylpyridine, and the anolyte solution is a 1-3 M sodium bicarbonate solution. The volume of the cathode electrolyte solution is 10-45 mL, and the volume of the anolyte solution is 10-45 mL.

[0035] Example 1: Preparation of the working electrode: Before constructing the chemical reactor, the preparation of the PbCu / MXene working electrode includes the following steps: 1. Add Ti3AlC2MAX, PbCl2, CuCl2, NaCl and KCl to a mortar and grind in an argon-filled glove box for 20 minutes to obtain a uniformly mixed powder; The molar ratio of Ti3AlC2MAX, PbCl2, CuCl2, NaCl, and KCl is 1:1.5:1.5:2:2. 2. The mixed powder obtained in step 1 is subjected to an argon atmosphere at 4°C for 1 minute. -1 The heating rate was increased to 700 °C and held for 24 hours, then washed three times with deionized water and freeze-dried for 48 hours to obtain PbCu / MXene. 3. Disperse 10 mg PbCu / MXene in a mixed solution containing 0.45 mL anhydrous ethanol, 0.45 mL deionized water, and 50 μL Nafion reagent. After sonication for 1 h, a uniform ink is formed. Finally, 50 μL of the catalyst ink is dropped onto a 1 × 1 cm⁻¹ substrate. 2 It is placed on carbon paper and dried at room temperature.

[0036] The reaction mechanism of the synthesis of 1-(2-pyridine)ethylamine from nitrate and 2-acetylpyridine via CN coupling is as follows: Figure 1 As shown, the entire reaction proceeds via an electrochemical-chemical-electrochemical (ECE) cascade mechanism. First, the nitrate undergoes an electrochemical reduction (E) reaction at the electrode surface to generate the key intermediate *NH₂OH. Subsequently, *NH₂OH undergoes a spontaneous chemical condensation (C) reaction with 2-acetylpyridine to generate 1-(2-pyridine)acetone oxime. Finally, the oxime intermediate undergoes further electrochemical hydrogenation reduction (E) at the cathode to yield the final product, 1-(2-pyridine)ethylamine.

[0037] Given that *NH2OH may be a key intermediate in the carbon-nitrogen coupling reaction, blank experiments were conducted comparing the addition of NH3 or NH2OH to the electrolyte while maintaining an open circuit or applying a cathode potential. Figure 2 As shown, 2-acetylpyridine and NH2OH can spontaneously generate 1-(2-pyridine)ethyl ketone oxime without the application of an electric potential, indicating that this process is a potential-independent chemical process. However, no formation of 1-(2-pyridine)ethyl ketone oxime was observed when NH3 replaced NH2OH, further demonstrating that *NH2OH directly participates in the CN coupling process. Crucially, a large amount of 1-(2-pyridine)ethylamine was detected only in the presence of NH2OH and with an applied reduction potential, while almost no 1-(2-pyridine)ethylamine was formed in the electrolyte system with NH3 as the nitrogen source, regardless of whether an electric current was applied. This directly proves that *NH2OH is the key nitrogen-containing intermediate for CN coupling and that the entire reduction process follows the ECE reaction pathway.

[0038] Differential electrochemical mass spectrometry (DEMS) was used to further monitor the reaction intermediates in the nitrate reduction and CN coupling reaction in real time. The DEMS signals at m / z = 17, 30, and 33 corresponded to NH3, NO, and NH2OH, respectively. Figure 3 As shown in figure a, in a 1M KHCO3 electrolyte containing only 0.1 M KNO3, characteristic signals of NH3, NO, and NH2OH were continuously detected on PbCu / MXene during four potential cycles. However, as Figure 3 As shown in b, after adding 2-acetylpyridine to the electrolyte, the characteristic signal of NH2OH was significantly weakened and then rapidly disappeared. Simultaneously, the signal intensities of NO and NH3 showed increasing and decreasing trends, respectively, indicating that the continuous generation and consumption of NH2OH promoted the nitrate reduction process and inhibited the production of NH3. DEMS results directly confirm that the reduction of nitrate on PbCu / MXene follows the NHO reaction pathway (NO3 + NH2OH). -→*NH2OH), and NH2OH, rather than NH3, is the key intermediate for achieving C–N coupling and generating 1-(2-pyridine)ethylamine.

[0039] The morphology of the PbCu / MXene catalyst was analyzed using scanning electron microscopy (SEM). Figure 4 As shown, PbCu / MXene not only exhibits a two-dimensional layered folded structure and a typical accordion morphology, but also clearly shows metal nanoparticles in the interlayer and on the surface of the support. This proves that molten salt etching can achieve the synthesis of MXene and the loading of metal sites in one step.

[0040] The structure of PbCu / MXene was analyzed using transmission electron microscopy (TEM). Figure 5 As shown, the metal nanoparticles are uniformly distributed on the layered structure of MXene without obvious agglomeration, demonstrating the excellent anchoring and dispersing effect of MXene on the metal particles. In addition, two sets of non-overlapping lattice fringes can be clearly observed. The lattice spacing of 0.285 nm corresponds to the (111) crystal plane of metal Pb, and the other set of 0.208 nm lattice spacing matches the (111) crystal plane of metal Cu, directly confirming that Pb and Cu are loaded on MXene in the form of bimetallic nanoparticles.

[0041] The surface bonding information and chemical state of the PbCu / MXene catalyst were analyzed using X-ray photoelectron spectroscopy (XPS). Figure 6 As shown in Figure a, in the high-resolution Ti 2p XPS spectrum, the characteristic peaks of PbCu / MXene can all be deconvolved to Ti-C(I) (454.8 / 460.8 eV), Ti-C(II) (455.7 / 461.8 eV), Ti-Cl (456.8 / 462.9 eV), and Ti-O (458.8 / 464.8 eV). Notably, the presence of Ti-C(I) and Ti-C(II) indicates the successful preparation of MXene with a Ti6C octahedral structure. Furthermore, as... Figure 6 As shown in b, no corresponding signal was observed in the high-resolution Al 2p XPS spectrum of PbCu / MXene, further demonstrating that the Al layer in the Ti3AlC2 MAX phase was selectively etched away. Figure 6 c and Figure 6 As shown in d, only 136.4 / 141.3 eV Pb were observed in the high-resolution Pb 4f XPS spectrum. 0 The characteristic peaks of Cu, and the high-resolution Cu 2p XPS spectrum can be deconvolved to Cu 0 (932.9 / 952.8 eV) and Cu 2+(935.3 / 955.6 eV).

[0042] The phase composition of PbCu / MXene was characterized using X-ray diffraction (XRD). Figure 7 As shown, characteristic MXene diffraction peaks at 7.9° and 15.9° were observed on PbCu / MXene, confirming that molten salt etching successfully achieved the transformation from the Ti3AlC2 MAX phase to Ti3C2T. x The transformation to the MXene phase. In addition, PbCu / MXene simultaneously exhibited characteristic diffraction peaks of metallic Pb at 31.3°, 36.3°, 52.2°, and 62.1° and characteristic diffraction peaks of metallic Cu at 43.3° and 50.4°, indicating that Pb and Cu are loaded onto MXene in the form of bimetallic nanoparticles.

[0043] The electrosynthesis performance of PbCu / MXene was investigated using linear sweep voltammetry (LSV). Figure 8 As shown, PbCu / MXene exhibits a more positive reaction initiation potential and a higher current density, indicating that the bimetallic sites can effectively reduce the reaction energy barrier and enhance the electrosynthesis activity.

[0044] Specifically, the steps are as follows: (1) The electrosynthesis of 1-(2-pyridine)ethylamine was carried out using a three-electrode system on the CHI-760E electrochemical workstation of Shanghai Chenhua, with an area of ​​1 cm². 2 Carbon paper supported catalyst, silver / silver chloride, and platinum sheet were used as working electrode, reference electrode, and counter electrode, respectively. (2) Electrolysis test was carried out in an H-type electrolytic cell separated by a Nafion 117 membrane, which included a cathode chamber and an anode chamber. A 1.0 M KHCO3 cathode electrolyte containing 0.1 M KNO3 and 0.01 M 2-acetylpyridine was added to the cathode chamber, and a 1.0 M KHCO3 anolyte was added to the anode chamber. A Nafion 117 membrane was installed between the cathode chamber and the anode chamber. The Nafion 117 membrane was pretreated by first being treated in a 5 wt% H2O2 solution at 80°C for 1 hour and then soaked in deionized water for 30 minutes, then soaked in H2SO4 at 80°C for 1 hour and then soaked in deionized water at 80°C for 30 minutes to remove any impurities that may be present on the Nafion 117 membrane. (3) The preparation steps of the working electrode are as follows: 10 mg of catalyst is dispersed in a mixed solution (50 μL Nafion solution + 0.45 mL deionized water + 0.45 mL anhydrous ethanol) and ultrasonically treated for half an hour to form a uniform catalyst ink. 50 μL of the catalyst ink is dropped onto a 1 cm... 2(4) All electrolysis potentials involved in this work are reversible hydrogen electrode (RHE) potentials, and the conversion formula is E(RHE) = E(Ag / AgCl) + 0.059 × pH + 0.197. (5) The electrocatalyst was subjected to constant potential electrolysis tests for 3 hours at different potentials, and the electrolysis potential range was -0.1 to -0.6 V vs. RHE. (6) After the constant potential electrolysis test was completed, 500 μL of electrolyte was taken out and the electrosynthesized 1-(2-pyridine)ethylamine was qualitatively and quantitatively analyzed by nuclear magnetic resonance hydrogen spectroscopy.

[0045] The selectivity and conversion rate of PbCu / MXene to 1-(2-pyridine)ethylamine at different potentials were quantified using a potentiostatic test. Figure 9 As shown, PbCu / MXene exhibits higher conversion and selectivity across the entire potential window, especially at -0.5 V vs. RHE, where PbCu / MXene demonstrates a 97.6% conversion of 2-acetylpyridine and nearly 100% selectivity for 1-(2-pyridine)ethylamine.

[0046] The Faraday efficiency of PbCu / MXene for 1-(2-pyridine)ethylamine at different potentials was quantified using a constant potential test. Figure 10 As shown, PbCu / MXene exhibits a higher Faraday efficiency for the synthesis of 1-(2-pyridine)ethylamine over the voltage range, reaching 68.5% at -0.5 V.

[0047] The yield of 1-(2-pyridine)ethylamine to PbCu / MXene at different potentials was quantified using a potentiostatic test. Figure 11 As shown, PbCu / MXene exhibits a stoichiometric coefficient of 128.1 μmol h⁻¹ at -0.5 V. -1 cm -2 Maximum yield.

[0048] The product distribution of PbCu / MXene at the optimal potential was qualitatively and quantitatively determined using proton nuclear magnetic resonance spectroscopy. Figure 12 As shown, thanks to the tandem catalytic effect between the lead and copper sites, PbCu / MXene promotes the CN coupling reaction to generate 1-(2-pyridine)ethylamine while effectively suppressing the formation of byproducts. Furthermore, since 1-(2-pyridine)ethyl oxime rapidly converts to 1-(2-pyridine)ethylamine at the applied potential, 1-(2-pyridine)ethyl oxime is almost undetectable in the liquid product.

[0049] Long-term stability is a key indicator for evaluating practical application potential. PbCu / MXene was continuously electrolyzed for 60 hours, with the electrolyte collected and replaced every 3 hours. For example... Figure 13 As shown, PbCu / MXene maintained high stability in the yield and FE of 1-(2-pyridine)ethylamine during 20 cycles of continuous electrolysis, which further demonstrates the excellent stability of PbCu / MXene.

[0050] The PbCu / MXene synthesis of 1-(2-pyridine)ethylamine via CN coupling follows a tandem catalytic mechanism. Figure 14 As shown, the Cu sites in PbCu / MXene are responsible for nitrate (NO3) - The selective reduction and stable formation of *NH2OH by Pb sites achieves 2 The activation of acetylpyridine (2-AP) and the construction of the CN bond simultaneously accelerate the electrochemical hydrogenation of 1-(2-pyridine)acetone oxime (12-PAO) to 1-(2-pyridine)ethylamine (12-PEA). Meanwhile, the MXene support provides a stable structure for electron transfer, metal dispersion, and the synergistic effect of dual active sites. Highly efficient synergy of co-reduction, C–N coupling, and deep hydrogenation is achieved through multi-component tandem catalysis and interfacial coupling.

[0051] Example 2: To further demonstrate the high efficiency of the electrosynthesis of 1-(2-pyridine)ethylamine by the method of the present invention, a comparative example of the above preferred example is given. Other steps are the same as in Example 1, except that CuCl2 is not added in step (1) of Example 1, and the sample obtained is an MXene-supported Pb single metal catalyst (Pb / MXene). The phase composition of Pb / MXene was characterized using X-ray diffraction (XRD). Figure 7 As shown, characteristic MXene diffraction peaks at 7.9° and 15.9° were observed on Pb / MXene, confirming that molten salt etching successfully achieved the transformation from the Ti3AlC2MAX phase to the Ti3C2T phase. x The MXene phase transition. In addition, Pb / MXene only showed characteristic diffraction peaks of metallic Pb at 31.3°, 36.3°, 52.2° and 62.1°, indicating that Pb is loaded on MXene in the form of single metal nanoparticles.

[0052] The electrosynthesis performance of Pb / MXene was investigated using linear sweep voltammetry (LSV). Figure 8 As shown, Pb / MXene exhibits a more negative reaction initiation potential and a lower current density, indicating that the Pb site has poor co-reduction activity for the two reactants.

[0053] The selectivity and conversion rate of Pb / MXene to 1-(2-pyridine)ethylamine at different potentials were quantified using potentiostatic testing. Figure 9As shown, Pb / MXene exhibited a high conversion rate of 2-acetylpyridine (78.4%), but a low selectivity (36.7%), indicating that the Pb site can achieve efficient conversion of 2-acetylpyridine, but is prone to generating a large number of byproducts.

[0054] The Faraday efficiency of Pb / MXene for 1-(2-pyridine)ethylamine at different potentials was quantified using a constant potential test. Figure 10 As shown, Pb / MXene exhibits a Faraday efficiency of 27.1% at the optimal potential, indicating low charge utilization efficiency for the electrosynthesis of the target product.

[0055] The yields of 1-(2-pyridine)ethylamine to Pb / MXene at different potentials were quantified using a potentiostatic test. Figure 11 As shown, Pb / MXene exhibited a 24.5 μmol h⁻¹ -1 cm -2 The yield.

[0056] The product distribution of Pb / MXene at the optimal potential was quantified using proton nuclear magnetic resonance spectroscopy. For example... Figure 12 As shown, Pb / MXene can promote the conversion of 2-acetylpyridine, but generates a large amount of 1-(2-pyridine)ethanol byproduct. This is because Pb / MXene lacks an active site that can selectively reduce nitrate to *NH2OH, which leads to further hydrogenation of 2-acetylpyridine to form alcohol byproduct instead of CN coupling to form oxime intermediate.

[0057] Example 3: To further demonstrate the high efficiency of the electrosynthesis of 1-(2-pyridine)ethylamine by the method of the present invention, a comparative example of the above preferred example is given. Other steps are the same as in Example 1, except that PbCl2 is not added in step (1) of Example 1, and the sample obtained is MXene supported Cu single metal catalyst (Cu / MXene). The phase composition of Cu / MXene was characterized using X-ray diffraction (XRD). Figure 7 As shown, characteristic MXene diffraction peaks at 7.9° and 15.9° were observed on Cu / MXene, confirming that molten salt etching successfully achieved the transformation from the Ti3AlC2MAX phase to the Ti3C2T phase. x The transformation to the MXene phase. Furthermore, Cu / MXene exhibited only characteristic diffraction peaks of metallic Cu at 43.3° and 50.4°, indicating that Cu is loaded onto MXene as single-metal nanoparticles.

[0058] The electrosynthesis performance of Cu / MXene was investigated using linear sweep voltammetry (LSV). Figure 8As shown, Cu / MXene exhibits a positive reaction initiation potential and a high current density, indicating that Cu sites can adsorb and activate nitrates.

[0059] The selectivity and conversion rate of Cu / MXene to 1-(2-pyridine)ethylamine at different potentials were quantified using potentiostatic testing. Figure 9 As shown, Cu / MXene exhibited high selectivity (81.3%), but relatively limited conversion (39.8%), indicating that its ability to convert 2-acetylpyridine was weak. However, the majority of the products generated by the conversion were 1-(2-pyridine)ethylamine.

[0060] The Faraday efficiency of Cu / MXene for 1-(2-pyridine)ethylamine at different potentials was quantified using a potentiostatic test. Figure 10 As shown, Cu / MXene exhibits a Faraday efficiency of 46.6% at the optimal potential.

[0061] The yield of 1-(2-pyridine)ethylamine to Cu / MXene at different potentials was quantified using a potentiostatic test. Figure 11 As shown, Cu / MXene exhibits a stoichiometric coefficient of 40.3 μmol h⁻¹ at -0.5 V. -1 cm -2 Maximum yield.

[0062] The product distribution of Cu / MXene at the optimal potential was quantified using 1H NMR spectroscopy. As shown in Figure 12, Pb / MXene can generate 1-(2-pyridine)ethylamine and significantly suppress the formation of 1-(2-pyridine)ethanol byproducts, but its substrate conversion ability is poor. This is because Cu has weak adsorption and activation of 2-acetylpyridine, resulting in insufficient conversion of 2-acetylpyridine. However, once the converted 2-acetylpyridine is activated, it can efficiently couple with *NH2OH generated at the Cu site and further convert to 1-(2-pyridine)ethylamine.

[0063] Example 4: The other steps are the same as in Example 1, except that the annealing temperature for preparing the working electrode in Example 1 is changed from 700 ℃ to 800 ℃; The resulting material properties are close; Example 5: The other steps are the same as in Example 1, except that the heating rate for preparing the working electrode in Example 1 is changed from 4 °C / min. -1 Replace with 6 ℃ min -1 ; The resulting material properties are close; Example 6: The other steps are the same as in Example 1, except that the pyrolysis time for preparing the working electrode in Example 1 is changed from 24 hours to 36 hours. The resulting material properties are close; Example 7: The other steps are the same as in Example 1, except that the concentration of potassium nitrate in the cathode electrolyte in Example 1 is replaced with 0.5 M instead of 0.1 M. The target product 1-(2-pyridine)ethylamine can be obtained; Example 8: The other steps are the same as in Example 1, except that the nitrogen source of the cathode electrolyte in Example 1 is replaced by potassium nitrate instead of potassium nitrite. The target product 1-(2-pyridine)ethylamine can be obtained; Example 9: The other steps are the same as in Example 1, except that the nitrogen source of the cathode electrolyte in Example 1 is replaced by sodium nitrate instead of potassium nitrate. The target product 1-(2-pyridine)ethylamine can be obtained; Example 10: The other steps are the same as in Example 1, except that the nitrogen source of the cathode electrolyte in Example 1 is replaced by sodium nitrite instead of potassium nitrate. The target product 1-(2-pyridine)ethylamine can be obtained; In summary, this invention proposes an electrosynthetic strategy for 1-(2-pyridyl)ethylamine, achieving efficient and green synthesis of 1-(2-pyridyl)ethylamine under mild conditions through CN coupling of nitrate and 2-acetylpyridine on an MXene-supported PbCu bimetallic catalyst (PbCu / MXene). PbCu / MXene exhibits near 100% selectivity, 98.3% conversion, and 68.5% Faradaic efficiency. Specifically, Cu preferentially adsorbs nitrate and selectively generates the key active intermediate *NH₂OH rather than excessively reducing it to NH₃, while the Pb sites optimize the adsorption and activation of 2-acetylpyridine to promote the formation of 1-(2-pyridyl)acetone oxime and subsequent hydrogenation. Furthermore, MXene, as a support, possesses both high conductivity and excellent dispersibility, effectively anchoring PbCu bimetallic nanoparticles to prevent particle aggregation and providing an efficient electron transport channel. The electrosynthesis strategy proposed in this work not only provides a new approach for the resource utilization of nitrates and the green electrosynthesis of fine amine compounds, but also offers new insights into the design of bimetallic catalysts in multi-reactant coupled electrocatalytic reactions.

[0064] The above content is merely an example and illustration of the concept of the present invention. It should be noted that those skilled in the art can make various improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention. Any modifications, alterations, and equivalent changes made by those skilled in the art based on the above-disclosed technical content without departing from the spirit and scope of the present invention are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, and evolutions made to the above embodiments based on the essential technology of the present invention still fall within the scope of the technical solution of the present invention.

[0065] Matters not covered in this invention are common knowledge.

Claims

1. A method for the electrosynthesis of 1-(2-pyridine)ethylamine, characterized in that, The method includes the following steps: Electrolysis was performed for 2–6 hours in an H-type electrolytic cell using a three-electrode system and a constant potential of -0.1 to -0.6 V vs. RHE to obtain 1-(2-pyridine)ethylamine. Among them, carbon paper loaded with PbCu / MXene is used as the working electrode, silver / silver chloride is used as the reference electrode, and platinum sheet is used as the counter electrode; The cathode electrolyte is an electrolyte solution containing a nitrogen source and a carbon source; The nitrogen source is one or more of sodium nitrite, potassium nitrite, sodium nitrate, potassium nitrate, ammonium nitrate, or lithium nitrate; the carbon source is 2-acetylpyridine. The concentration of the nitrogen source is 0.1~0.5 M, and the concentration of the carbon source is 0.01~0.03 M.

2. The electrosynthesis method of 1-(2-pyridine)ethylamine as described in claim 1, characterized in that, The concentration of the cathode electrolyte solution is 1~3 M; the electrolyte is one or more of sodium hydroxide, potassium hydroxide, potassium bicarbonate, potassium carbonate, sodium bicarbonate, sodium carbonate, sodium sulfate, potassium sulfate, and sodium perchlorate. The concentration of the anolyte solution is 1~3 M; the electrolyte is one or more of sodium hydroxide, potassium hydroxide, potassium bicarbonate, potassium carbonate, sodium bicarbonate, sodium carbonate, sodium sulfate, potassium sulfate, and sodium perchlorate.

3. The electrosynthesis method of 1-(2-pyridine)ethylamine as described in claim 1, characterized in that, A Nafion 117 membrane is installed between the cathode chamber and the anode chamber.

4. The electrosynthesis method of 1-(2-pyridine)ethylamine as described in claim 1, characterized in that, The method for preparing the working electrode includes the following steps: (1) Under an argon atmosphere, Ti3AlC2MAX, PbCl2, CuCl2, NaCl and KCl were added to a mortar and ground for 20-30 minutes to obtain a mixed powder; The molar ratio of Ti3AlC2MAX, PbCl2, CuCl2, NaCl, and KCl is 1:1.5~3:1.5~3:2~4:2~4; (2) The prepared mixed powder was annealed in an argon atmosphere at a temperature of 700~800℃ for 24~36 hours, washed and then freeze-dried for 48~72 hours to obtain PbCu / MXene; (3) Disperse PbCu / MXene in a mixed solution, then sonicate for 0.5 to 1.5 hours to form ink, and finally drop the ink onto carbon paper and dry at room temperature to obtain the working electrode; In this mixture, 2-15 mg of PbCu / MXene is added to every 0.95 mL of the mixed solution; the mixed solution consists of anhydrous ethanol, deionized water and Nafion reagent in a volume ratio of 9:9:

1. per 1 cm 2 Add 20~100 μL of ink to the carbon paper.

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