Method for catalytic conversion of CO2 by using cuprous ion-loaded melamine-based functionalized super-crosslinked polymer

Abstract

The invention discloses a method for catalytically converting CO2 (carbon dioxide) by using a cuprous ion-loaded melamine-functionalized super-crosslinked polymer. The method comprises the following steps: firstly, synthesizing a series of melamine-functionalized super-crosslinked polymers HCP-3N-nNH2-Cu; then, according to the types of substituent groups in melamine monomers and the proportion of the monomers to a cross-linking agent, the catalyst with different specific surface areas and CO2 adsorption capacities is prepared. HCP-3N-2NH2-Cu having the maximum specific surface area and CO2 adsorption capacity is preferably used as a catalyst. And then, the HCP-3N-2NH2-Cu is characterized by a plurality of characterization methods, so that the structure and the composition of the HCP-3N-2NH2-Cu are confirmed. The HCP-3N-2NH2-Cu shows an excellent catalytic effect in the two-component reaction of catalytic conversion of CO2 and alkynyl amine. In addition, the recycling performance of HCP-3N-2NH2-Cu is verified, and the result shows that the yield is not obviously reduced after the catalyst is recycled for three times.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a method for catalytic conversion of CO2 using melamine-functionalized hypercrosslinked polymers loaded with cuprous ions. Background Technology

[0002] Carbon dioxide (CO2) is one of the major greenhouse gases, and its massive emissions have exacerbated global climate change. How to achieve the resource utilization of CO2 has become a current research hotspot. The CO2 molecule has high chemical stability and a linear structure, with its carbon atoms in the highest oxidation state and a high activation energy barrier, thus posing a significant challenge to direct conversion and utilization. Converting CO2 into high-value-added chemicals (such as oxazolidinones and carbonates) through catalytic methods not only helps reduce greenhouse gas emissions but also enables the recycling of carbon resources, aligning with the principles of green chemistry and sustainable development.

[0003] Currently, CO2 catalytic conversion technology mainly includes two systems: homogeneous catalysis and heterogeneous catalysis. In homogeneous catalysis systems, noble metal complexes (such as silver, palladium, copper, etc.) or organic bases are usually used as catalysts. Although these systems exhibit high catalytic activity and selectivity under specific conditions, they have obvious drawbacks: (1) the reaction often needs to be carried out at high temperature and high pressure, resulting in high energy consumption and harsh reaction conditions; (2) the catalyst is difficult to separate and recover from the reaction system, resulting in poor reusability, which not only increases costs but may also cause heavy metal pollution; (3) some systems have a narrow range of substrate applicability, many side reactions, and difficult product purification.

[0004] To overcome the aforementioned problems, heterogeneous catalytic materials such as metal-organic frameworks (MOFs), covalent organic frameworks (COFs), polyionic liquids (PILs), and hypercrosslinked polymers (HCPs) have been extensively studied. These materials possess high specific surface areas, tunable pore structures, and excellent CO2 adsorption capabilities, effectively promoting CO2 activation and conversion. However, existing porous catalytic materials still have some shortcomings: for example, the synthesis conditions of MOFs and COFs are complex and costly, and their stability in hydrothermal or chemical environments is limited; although PILs have good CO2 affinity, their pore structure and active site distribution are not easily controlled precisely, and structural collapse or loss of active components can easily occur during recycling. In recent years, hypercrosslinked polymers have attracted attention due to their advantages such as simple synthesis, tunable structure, and good physicochemical stability. By introducing nitrogen-containing functional groups (such as triazine and amino groups) and loading transition metal ions (such as silver, copper, and palladium), heterogeneous catalysts with highly efficient CO2 adsorption and activation capabilities can be constructed. In particular, cuprous ions (Cu... +As an inexpensive active center with a unique electronic structure, copper ions have shown excellent potential in CO2 reduction and cyclization reactions. However, existing reports on supported copper catalysts mostly focus on copper nanoparticles or copper oxides, whose easy aggregation and oxidation lead to a decline in catalytic performance. Research on hypercrosslinked polymer catalysts based on cuprous ions, especially their efficient catalytic conversion of CO2 under mild conditions and good cycling stability, is still insufficient. Therefore, developing a structurally stable, highly active, and recyclable cuprous-supported melamine-based functionalized ionic hypercrosslinked polymer catalyst to achieve efficient CO2 conversion under mild conditions is of significant scientific importance and application value. Summary of the Invention

[0005] The technical problem this invention aims to solve is to overcome the shortcomings of existing CO2 catalytic conversion technologies, such as low catalyst efficiency, harsh reaction conditions, poor recyclability, and difficulty in recovering homogeneous catalysts. This invention provides a method for the catalytic conversion of CO2 using a melamine-based functionalized hypercrosslinked polymer loaded with cuprous ions. This method involves designing and synthesizing a hypercrosslinked polymer with high specific surface area and CO2 adsorption capacity, and loading it with cuprous ions (Cu). + As the active center, it enables efficient catalysis of the two-component reaction between CO2 and alkynylamine under mild conditions to generate high-value-added oxazolidinone compounds, and the catalyst has good structural stability and recyclability.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A method for catalytically converting CO2 using a melamine-functionalized hypercrosslinked polymer loaded with cuprous ions, comprising the following steps:

[0008] Step 1: Synthesis of melamine-functionalized hypercrosslinked polymer loaded with cuprous ions: Using melamine as a monomer and 1,4-dichlorobenzyl as a crosslinking agent, a hypercrosslinked polymer HCP-3N-nNH2 (where n represents the number of amino groups, n=0-3) was synthesized via Friedel-Crafts alkylation. Then, copper ions were loaded onto copper acetate (Cu(OAc)2) in an aqueous solution, and sodium borohydride (NaBH4) was added as a reducing agent to further enhance the crosslinking effect. 2+ Reduced to cuprous ions (Cu) + ), to obtain a melamine-functionalized hypercrosslinked polymer HCP-3N-nNH2-Cu loaded with cuprous ions;

[0009] Step 2, Optimize catalyst structure: By adjusting the ratio of monomer to crosslinking agent (preferably molar ratio 1:6) and metal loading (preferably Cu(OAc)2 addition amount is 16 wt%), a catalyst with high specific surface area and CO2 adsorption capacity is prepared, with HCP-3N-2NH2-Cu preferred as the best catalyst;

[0010] Step 3, characterizing the catalyst: Specific surface area and porosity analysis (BET), Fourier transform infrared spectroscopy (FT-IR), and solid-state nuclear magnetic resonance (SMR) were used. 13 The structure, composition and performance of the catalyst were systematically characterized by methods such as C NMR, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), in-situ Raman spectroscopy, thermogravimetric analysis (TGA), flame atomic absorption spectroscopy and elemental analysis, confirming its porous structure, functional group distribution and successful loading of cuprous ions.

[0011] Step 4: Applying the catalyst: The HCP-3N-2NH2-Cu catalyst was applied to the two-component reaction of CO2 and alkynylamine. The catalytic conversion was carried out under mild conditions (such as 30 °C and atmospheric pressure CO2). After the reaction was completed, the products were separated and quantitatively analyzed by extraction, column chromatography or high performance liquid chromatography (HPLC).

[0012] Step 5, Catalyst Recycling: After the reaction, the catalyst is washed (with water and methanol) and vacuum dried, and can be directly recycled to verify its stability and repeatability.

[0013] Further, in step 2, the molar ratio of the monomer to the crosslinking agent ranges from 1:3 to 1:8, preferably 1:6; the metal loading, calculated as Cu(OAc)2, is 0-28 wt%, preferably 16 wt%; the amount of the reducing agent NaBH4 ensures that Cu 2+ Completely reduced to Cu + .

[0014] Further, in step 4, the optimized reaction conditions include: catalyst dosage of 10-50 mg, preferably 30 mg; reaction temperature of 20-60 ℃, preferably 30 ℃; solvent of DMSO or solvent-free, preferably 0.5 mL DMSO; base of TMG (tetramethylguanidine), with a dosage of n(TMG):n(substrate) of 1:20 (0.013 mmol); and reaction time depending on the substrate, typically 24 h.

[0015] Furthermore, in step 3, HCP-3N-2NH2-Cu is characterized by various methods including the following: specific surface area and porosity analysis, Fourier transform infrared spectroscopy, solid-state nuclear magnetic resonance, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, in-situ Raman spectroscopy, thermogravimetric analysis, flame atomic absorption spectroscopy, and nuclear magnetic resonance spectroscopy.

[0016] Polymer characterization methods:

[0017] Specific surface area and porosity analysis (BET): The specific surface area, pore volume, and pore size distribution of the melamine-functionalized hypercrosslinked polymer HCP-3N-2NH2-Cu loaded with cuprous ions were determined by BET to investigate its adsorption capacity for CO2. CO2 adsorption curves were measured at 273 K and 298 K to determine the adsorption volume of CO2 by the polymer. The specific experimental method was as follows: 150 mg of sample was weighed and degassed at 135℃ for 8 h; the N2 adsorption-desorption isotherm was measured in liquid nitrogen at 298 K using a Bio-Kubo-X1000 thermometer; and the CO2 adsorption isotherm was measured at 273 K and 298 K by adjusting the water temperature.

[0018] Fourier Transform Infrared Spectroscopy (FTIR): To verify the successful preparation of the hypercrosslinked polymer and the melamine-functionalized hypercrosslinked polymer loaded with cuprous ions, FT-IR was used to analyze the major functional groups in the catalyst sample. 150 mg of KBr and 2 mg of the sample were weighed and dried at 110 °C for 5 h. After cooling to room temperature, the sample was pressed into a KBr pan and measured on a Thermo Scientific Nicoleti S20 spectrometer in the spectral range of 4000–400 cm⁻¹. -1 .

[0019] Solid-state NMR (13C NMR): Solid-state NMR (13C NMR) was used to determine the structure of the catalyst. The testing instrument was a Bruker AVANCE NEO 400MHz from Bruker (Beijing) Technology Co., Ltd.

[0020] Scanning electron microscopy (SEM) and transmission electron microscopy (TEM): SEM was used to observe the surface morphology of the catalyst, while TEM was used to observe whether metallic Cu was successfully loaded onto the polymer and the EDX images of various elements in the polymer. The SEM method involved sonicating the sample for 10 minutes followed by ethanol decomposition. Since the sample was non-conductive, gold sputtering was required. TEM measurements were performed using a FEI Tecnai F20 microscope.

[0021] X-ray photoelectron spectroscopy (XPS): XPS full-spectrum and fine-spectrum scanning can verify whether Cu has been successfully loaded and can observe the dispersion state of various elements in the polymer. Before analyzing the sample, an appropriate amount of sample is taken out, made into a thin film by pressing, and then fixed onto the sample tray and placed into the Thermo K-Alpha XPS instrument for scanning.

[0022] In-situ Raman spectroscopy: In-situ Raman spectroscopy was used to investigate the activation effect of catalysts on CO2. After degassing, the absorption peaks of the samples were measured at room temperature under N2 and CO2 atmospheres using a Horiba LabRAM HR Evolution spectrometer. The excitation wavelength was 785 nm, and the wavenumber range was 50-4000 cm⁻¹. -1 .

[0023] Thermogravimetric analysis (TGA): TGA is used to evaluate the thermal stability of polymers. A NETZSCH TG 209F3 instrument was used to determine the temperature profiles of the samples at a heating rate of 10 °C / min, with a temperature range of 30 °C–800 °C.

[0024] Flame atomic absorption spectrometry: To determine the content of metallic Cu in the polymer, flame atomic absorption spectrometry was used. The experimental steps are as follows: (1) Carbonization. Weigh 100 mg of HCP-3N-2NH2-Cu into a quartz crucible and pyrolyze it at 300 °C in a muffle furnace for 2 h. (2) Ashing. Raise the temperature of the muffle furnace to 500 °C and continue pyrolysis for 2 h. (3) Melting. After ashing, allow it to cool naturally and remove the quartz crucible. Add 1 mL of hydrogen peroxide to the crucible and place it in a muffle furnace at 700 °C for 5 h. (4) Digestion. After ashing, transfer the ash to a conical flask, add 20 mL of nitric acid (1:1), and reflux at 125 °C on a hot plate for 2 h. (5) Measurement. After digestion, take the supernatant and filter it through a 0.45 μm filter membrane. Test it using flame atomic absorption spectrometry. The specific method is based on the national standard HJ 751-2015.

[0025] Nuclear magnetic resonance spectroscopy (NMR): The structure of the reaction products in this experiment was determined using nuclear magnetic resonance spectroscopy (NMR). Among other things, 1 In the 1H NMR spectroscopy, CDCl3 was used as the solvent, and its chemical shift reference standard was 7.26 ppm (parts per million). 13 The C NMR spectrum also uses CDCl3 as a reference, with a chemical shift reference value of 77.16 ppm for the carbon signal. The following abbreviations are used for spectral calibration: s is singlet, d is multiply, t is triplet, m is multiply, and J is the coupling constant in Hz.

[0026] Furthermore, in step 4, the synthesis method of propargylamine compounds is as follows:

[0027] Dichloromethane was added to K2CO3 and amine compounds and reacted at room temperature. Then, 3-bromopropyne was added at 0 °C. After the reaction was completed, the reaction solution was extracted, evaporated, concentrated, separated, and purified to obtain alkynylamine compounds.

[0028] Furthermore, in step 4, the qualitative and quantitative analysis methods for the reaction products of alkynylamine compounds and CO2 are as follows: Qualitative method: The alkynylamine compounds are reacted with CO2. After the reaction is complete, the filtrate is extracted with water and dichloromethane. The supernatant is collected and the crude product is obtained by rotary evaporation. The pure product is obtained by column chromatography using n-hexane (PE:EA = 5:1) as the eluent. The structure of the product is determined by nuclear magnetic resonance. Quantitative method: The alkynylamine compounds are reacted with CO2. After the reaction is complete, the mixture is filtered, and the filtrate is collected. The reaction solution is quantitatively analyzed by high performance liquid chromatography (HPLC). o-phenylenediamine is used as the internal standard. The mobile phase ratio is methanol:water = 70:30, the flow rate is 1 mL / min, the column temperature is 35 ℃, the absorption wavelength is 273 nm, and the injection volume is 2.5 μL.

[0029] Furthermore, in step 5, the recycled material is directly used for the next reaction after simple washing (3 times each with water and methanol) and vacuum drying, and the catalytic efficiency remains above 80% after 3 cycles.

[0030] Compared with the prior art, the technical effects and advantages of the present invention are as follows:

[0031] Highly efficient catalytic performance: The HCP-3N-2NH2-Cu catalyst prepared in this invention exhibits high catalytic activity and selectivity for the two-component reaction of 10 vol% CO2 with alkynylamine under mild conditions (30℃, atmospheric pressure), with a yield of over 88%, and has broad applicability to a variety of substrates (including electron-donating groups, electron-withdrawing groups, non-aromatic rings, heterocycles and complex molecules).

[0032] Excellent cycle stability and recyclability: The catalyst can be recovered through simple washing, and the catalytic efficiency does not decrease significantly after being recycled 3 times, with the yield remaining above 80%, which significantly reduces catalyst cost and environmental risk.

[0033] Controllable structure and well-defined characterization: By systematically optimizing the crosslinking ratio and metal loading, the specific surface area, pore structure, and CO2 adsorption capacity of the catalyst were precisely controlled. Multiple characterization methods confirmed that the catalyst possesses a stable triazine framework, amino functional groups, and cuprous active centers, and can effectively activate CO2 molecules (e.g., in-situ Raman spectroscopy shows a 1202 cm⁻¹ concentration). -1 (Characterial peak of CO2 adsorption).

[0034] Environmentally friendly and easy to operate: The reaction conditions are mild and do not require high temperature and high pressure; the amount of solvent used is small or there is no solvent, which is in line with the principles of green chemistry; the catalyst synthesis method is simple and easy to scale up, which provides potential for industrial applications.

[0035] This invention provides a novel, efficient, and recyclable heterogeneous catalytic system for the resource utilization of CO2, which has significant scientific value and practical application prospects. Attached Figure Description

[0036] Figure 1 This diagram illustrates the synthesis method of the melamine-functionalized hypercrosslinked polymer loaded with cuprous ions according to the present invention.

[0037] Figure 2 The N2 adsorption-desorption curves of HCP-3N-2NH2 and HCP-3N-2NH2-Cu of the present invention are shown (where the molar ratio of monomer to crosslinking agent in the polymer is 1:6).

[0038] Figure 3 N2 adsorption-desorption curves for different monomers and crosslinking agents in this invention;

[0039] Figure 4 The CO2 adsorption curves of HCP-3N-2NH2 and HCP-3N-2NH2-Cu of the present invention at 273K and 298K (wherein the molar ratio of monomer to crosslinking agent in the polymer is 1:6);

[0040] Figure 5 CO2 adsorption curves at 273K and 298K for different monomer:crosslinking agent molar ratios of the present invention;

[0041] Figure 6 The CO2 adsorption curves of different melamine monomers of the present invention at 273K and 298K (wherein the molar ratio of monomer to crosslinking agent in the polymer is 1:6);

[0042] Figure 7 The FTIR spectra of HCP-3N-2NH2, HCP-3N-2NH2-Cu and benzo-melamine of this invention are shown below.

[0043] Figure 8 The solid-state NMR spectrum of HCP-3N-2NH2-Cu of this invention;

[0044] Figure 9 The SEM image of HCP-3N-2NH2-Cu of this invention;

[0045] Figure 10(a) is a TEM image of HCP-3N-2NH2-Cu of the present invention; (b)(c)(d) are EDX elemental mapping images of HCP-3N-2NH2-Cu of the present invention, representing N, C and Cu, respectively;

[0046] Figure 11 (a) Full spectrum of HCP-3N-2NH2-Cu; (b) Fine C 1s spectrum of HCP-3N-2NH2-Cu; (c) Fine N 1s spectrum of HCP-3N-2NH2-Cu; (d) Fine Cu 2p spectrum of HCP-3N-2NH2-Cu;

[0047] Figure 12 This is the in-situ Raman spectrum of HCP-3N-2NH2-Cu of the present invention;

[0048] Figure 13 The thermogravimetric curve of HCP-3N-2NH2-Cu in this invention;

[0049] Figure 14 (a) Screening chart of catalysts for synthesis with different substituent monomers; (b) Screening chart of catalysts for synthesis with different monomer:crosslinker molar ratios; (c) Screening chart of catalysts for synthesis with different metal loading amounts;

[0050] Figure 15 (a) Comparison of specific surface area of ​​catalysts synthesized with different substituent monomers; (b) Comparison of CO2 adsorption capacity of catalysts synthesized with different substituent monomers; (c) Comparison of specific surface area of ​​catalysts synthesized with different molar ratios of substituent monomers to crosslinking agents; (d) Comparison of CO2 adsorption of catalysts synthesized with different molar ratios of substituent monomers to crosslinking agents.

[0051] Figure 16 (a) Screening chart for base types; (b) Screening chart for base dosage; (c) Screening chart for solvent types; (d) Screening chart for solvent dosage;

[0052] Figure 17 (a) Screening chart for reaction temperature; (b) Screening chart for catalyst dosage;

[0053] Figure 18 This is a diagram illustrating the effect of catalyst recycling in this invention;

[0054] Figure 19 (a) SEM image of HCP-3N-2NH2-Cu before recycling; (b) SEM image of HCP-3N-2NH2-Cu after recycling;

[0055] Figure 20TEM images of HCP-3N-2NH2-Cu before recycling, (b)(c)(d) are EDX elemental mapping images, representing N, C and Cu respectively;

[0056] Figure 21 The TEM spectrum of HCP-3N-2NH2-Cu after recycling, (b)(c)(d)(e) are EDX elemental mapping images, which are N, C and Cu respectively. Detailed Implementation

[0057] The present invention will be further described in detail below with reference to specific embodiments. The described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. In the following embodiments, unless otherwise specified, the experimental methods used are conventional methods, and the materials and reagents used are commercially available.

[0058] Example 1: Synthesis of HCP-3N-2NH2-Cu, a melamine-functionalized hypercrosslinked polymer loaded with cuprous ions.

[0059] (1) Preparation of melamine-functionalized hypercrosslinked polymer HCP-3N-2NH2: Melamine (monomer, 1.0 mmol) and 1,4-dichlorobenzyl chloride (crosslinking agent, 6.0 mmol, molar ratio 1:6) were dissolved in 30 mL of anhydrous dichloroethane, and anhydrous ferric chloride (FeCl3, 12.0 mmol) was added as a catalyst. The reaction was carried out under nitrogen protection and stirred at 85 °C for 24 h. After the reaction was completed, the mixture was cooled to room temperature, dilute hydrochloric acid was added to terminate the reaction, and the mixture was washed three times alternately with ethyl acetate, deionized water, and methanol. After filtration, the mixture was dried under vacuum for 12 h to obtain the yellowish-brown solid hypercrosslinked polymer HCP-3N-2NH2.

[0060] (2) Loading of cuprous ions: The above HCP-3N-2NH2 (200 mg) was dispersed in 40 mL of deionized water, and copper acetate (Cu(OAc)2, 32 mg, equivalent to 16 wt% metal loading) was added. The mixture was stirred at room temperature for 1 h to allow for complete adsorption of copper ions. Subsequently, sodium borohydride (NaBH4, 100 mg) was slowly added, and the mixture was stirred for 2 h under nitrogen protection to load the copper ions. 2+ Reduced to Cu + After the reaction was completed, the mixture was filtered, washed three times each with deionized water and ethanol, and dried under vacuum to obtain the catalyst HCP-3N-2NH2-Cu supported on cuprous ions, which was a yellowish-brown solid.

[0061] Example 2: Characterization of the catalyst

[0062] The HCP-3N-2NH2-Cu prepared in Example 1 was systematically characterized as follows:

[0063] Specific surface area and porosity analysis (BET): The specific surface area of ​​the catalyst was determined by nitrogen adsorption-desorption method, and the value was 910.6347 m². 2 / g, pore volume is 1.56339 cm³ 3 The average pore size is 1.7168 nm, which indicates that it has a rich microporous structure, which is beneficial for CO2 adsorption.

[0064] Fourier transform infrared (FT-IR) spectrum: at 2920 cm⁻¹ -1 An absorption peak of -CH2 vibration (from the crosslinking agent) appears at 1548 cm⁻¹. -1 1384 cm -1 and 778 cm -1 The presence of triazine skeleton and amino group characteristic peaks confirms that the polymer was successfully synthesized and that the functional groups were retained.

[0065] Scanning electron microscopy (SEM): Fresh catalyst exhibits an irregular porous network structure; after three cycles, the overall morphology remains stable.

[0066] X-ray photoelectron spectroscopy (XPS): In the Cu 2p spectrum, the binding energy is 933.18 eV (Cu 2p). 3 / 2 ) and 953.15 eV (Cu 2p 1 / 2 ) Corresponding to Cu + Characteristic peaks confirm successful loading of cuprous ions.

[0067] In-situ Raman spectroscopy: 1202 cm⁻¹ under CO₂ atmosphere -1 The presence of CO2 adsorption characteristic peaks indicates that the catalyst can effectively activate CO2.

[0068] Thermogravimetric analysis (TGA): Under N2 atmosphere, the catalyst showed no significant weight loss below 405 °C, demonstrating excellent thermal stability.

[0069] Flame atomic absorption spectrometry: The Cu content in the catalyst was found to be 1.70 wt%.

[0070] Elemental analysis: The contents of C, H and N elements are 70.90%, 4.75% and 2.80% respectively, which are consistent with the theoretical values.

[0071] Example 3: Two-component reaction of CO2 with propargylamine (condition optimization)

[0072] In a 10 mL side-joint reaction tube, add HCP-3N-2NH2-Cu catalyst (30 mg), propargylamine (0.25 mmol), TMG (tetramethylguanidine, 0.013 mmol, n(TMG):n(substrate) = 1:20), and DMSO (0.5 mL). Connect the reaction tube to a CO2 gas bag, evacuate the gas three times to remove air, and stir the reaction at 30 °C for 24 h. After the reaction is complete, collect the filtrate and perform quantitative analysis of the reaction solution by high performance liquid chromatography (HPLC). Use o-phenylenediamine as an internal standard, with a mobile phase ratio of methanol:water = 70:30, a flow rate of 1 mL / min, a column temperature of 35 °C, an absorption wavelength of 273 nm, and an injection volume of 2.5 μL.

[0073] Optimization Results: Crosslinking Ratio: The highest yield (82%) was achieved when the monomer to crosslinking agent ratio was 1:6. Metal Loading: The highest yield (84%) was achieved when the Cu(OAc)₂ dosage was 16 wt%. Catalyst Dosage: The yield reached 88% with 30 mg of catalyst, and increasing the dosage did not significantly improve the yield. Reaction Temperature: The yield was 88% at 30 ℃, and the yield decreased above or below this temperature. Solvent: The highest yield (91%) was achieved with DMSO (0.5 mL) or without solvent. Base Type and Dosage: TMG was the optimal base, and the yield was 86% when the ratio of n(TMG):n(substrate) = 1:20.

[0074] Example 4: Substrate Expansion Experiment: Using the optimal conditions of Example 3, the catalytic effect of HCP-3N-2NH2-Cu on different alkynylamine substrates was investigated: Electron-donating group substrates (3 examples): such as p-methoxyphenylpropynylamine, yield 85%-88%. Electron-withdrawing group substrates (1 example): such as p-nitrophenylpropynylamine, yield 82%. Non-aromatic ring substrates (1 example): such as cyclohexylpropynylamine, yield 80%. Heterocyclic substrates (1 example): such as pyridylpropynylamine, yield 78%. Complex molecular substrates (2 examples): such as drug molecule derivatives, yield 75%-77%. The structures of all products were analyzed by nuclear magnetic resonance (NMR). 1 H NMR and 13 Confirmed by C NMR.

[0075] Example 5: Catalyst Recycling Performance: After the reaction, the catalyst was washed three times each with deionized water and methanol, dried under vacuum at 60 °C for 12 h, and then directly used in the next reaction. Recycling results: First cycle: 88% yield. Second cycle: 85% yield. Third cycle: 82% yield. Fourth cycle: yield decreased to 70%. After three cycles, the yield remained above 82%. SEM characterization of the catalyst structure showed slight swelling, but the main active sites were retained. Reduction or metal loading treatment could not completely restore the activity, indicating that structural changes were the main cause of performance degradation.

[0076] Example 6: Catalytic reaction under solvent-free conditions The reaction of Example 3 was repeated under solvent-free conditions: propargylamine (0.5 mmol), TMG (0.013 mmol), and HCP-3N-2NH2-Cu (30 mg) were mixed and reacted at 30 °C for 24 h under a CO2 atmosphere. The yield reached 91%, indicating that the catalyst still has high efficiency in a solvent-free system, which meets the requirements of green chemistry.

[0077] The above embodiments demonstrate that the melamine-functionalized hypercrosslinked polymer catalyst supported on cuprous ions provided by this invention exhibits high activity, high selectivity, and excellent cycling stability for CO2 conversion under mild conditions, and has broad substrate applicability, providing a feasible solution for CO2 resource utilization. Those skilled in the art can make appropriate modifications to the above embodiments without departing from the principles of this invention, and these modifications should also be considered within the scope of protection of this invention.

Claims

1. A process for catalytic conversion of CO2 by cuprous ion loaded melamine based functionalized hypercrosslinked polymer characterized in that, The method comprises the following steps: Step 1: Synthesis of melamine-functionalized hypercrosslinked polymers loaded with cuprous ions: Crosslinking polymerization was carried out by selecting different melamine monomers and crosslinking agents (1,4-dichlorobenzyl) via Friedel-Crafts alkylation reaction, and copper acetate (Cu(OAc)2) was loaded, followed by the addition of sodium borohydride (NaBH4) as a reducing agent to release copper ions (Cu... 2+ ) is reduced to cuprous ions (Cu) + A series of melamine-functionalized hypercrosslinked polymers HCP-3N-nNH2-Cu (n=0-3) loaded with cuprous ions were prepared. Step 2, optimizing the catalyst structure: by adjusting the type of substituent in the monomer and the ratio of monomer to crosslinking agent, catalysts with different specific surface areas and CO2 adsorption capacities are prepared, and HCP-3N-2NH2-Cu with the largest specific surface area and CO2 adsorption capacity is used as the catalyst; Step 3, characterizing the catalyst: various characterizations are performed on HCP-3N-2NH2-Cu to confirm its structure and composition, and further verify its catalytic effect and reaction mechanism; Step 4, applying the catalyst: HCP-3N-2NH2-Cu is applied to the two-component reaction of CO2 and alkynyl amine, after the reaction is completed, the product is separated and quantitatively analyzed to determine the efficiency of the catalytic reaction; Step 5, recycling of the catalyst: by washing and drying, the recycling performance of the catalyst HCP-3N-2NH2-Cu is verified.

2. A method for catalytic conversion of CO2 by a melamine-based functionalized hypercrosslinked polymer loaded with cuprous ions according to claim 1, characterized in that: In step 1, the preparation of the catalyst, i.e., the synthesis of the melamine-based functionalized hypercrosslinked polymer HCP-3N-nNH2(n=0-3) and HCP-3N-nNH2-Cu (n=0-3) loaded with cuprous ions; first, copolymerization with a crosslinking agent through Friedel-Crafts alkylation to obtain a hypercrosslinked polymer HCP-3N-nNH2, then, loading copper with HCP-3N-nNH2 and Cu(OAc)2 in an aqueous solution, and adding NaBH4 to reduce copper ions (Cu 2+ ) to obtain a HCP-3N-nNH2-Cu catalyst loaded with cuprous ions.

3. Process for the catalytic conversion of CO2 by a melamine-based functionalized hypercrosslinked polymer loaded with subcupric ions according to claim 2, characterized in that: The synthesis of HCP-3N-nNH2-Cu comprises the following steps: Preparation of melamine-based functionalized hypercrosslinked polymer HCP-3N-nNH2: the monomer (melamine) and the crosslinking agent (1,4-p-dichlorobenzyl) are reacted in dichloroethane to obtain the hypercrosslinked polymer HCP-3N-nNH2; Vacuum drying: remove the solvent to obtain the dried hypercrosslinked polymer HCP-3N-nNH2; Copper-loaded: HCP-3N-nNH2 was loaded with copper in aqueous solution with Cu(OAc)2, and reduced with NaBH4 to copper ions (Cu 2 + ) to obtain HCP-3N-nNH2-Cu catalyst loaded with cuprous ions.

4. The method of catalytic conversion of CO2 by the cuprous ion- loaded melamine-based functionalized hypercrosslinked polymer according to claim 1, characterized in that: In step 3, various characterizations are performed on HCP-3N-2NH2-Cu, including the following characterization methods: specific surface area and porosity analysis, Fourier infrared spectroscopy, solid nuclear magnetic resonance, scanning electron microscope, transmission electron microscope, X-ray photoelectron spectroscopy, in-situ Raman spectroscopy, thermogravimetric analysis, flame atomic absorption spectroscopy, and nuclear magnetic resonance spectroscopy.

5. The method of catalytic conversion of CO2 by the cuprous ion- loaded melamine-based functionalized hypercrosslinked polymer according to claim 1, characterized in that: In step 4, the synthesis method of propargyl amine compounds is as follows: After adding dichloromethane to K2CO3 and amine compounds at room temperature, 3-bromopropargyl is added at 0°C, the reaction liquid is extracted after the reaction is completed, and the propargyl amine compound is obtained after evaporation, concentration, separation and purification.

6. The method of catalytic conversion of CO2 by the cuprous ion- loaded melamine-based functionalized hypercrosslinked polymer according to claim 1, characterized in that: In step 4, the qualitative and quantitative methods of the reaction product of propargyl amine compound and CO2 are as follows: Qualitative method: after the reaction of propargyl amine compound and CO2 is completed, the filtrate is extracted with water and dichloromethane, the upper liquid is taken, and the crude product is obtained after rotary evaporation, and the pure product is obtained by column chromatography with n-hexane PE:EA=5:1 as the eluent, and the structure of the product is determined by nuclear magnetic resonance; Quantitative method: after the reaction of propargyl amine compound and CO2 is completed, the filtrate is collected, and the reaction liquid is quantitatively analyzed by high performance liquid chromatography, with o-phenylenediamine as the internal standard, the mobile phase ratio is methanol:water=70:30, the flow rate is 1 mL / min, the column temperature is 35 ℃, the absorption wavelength is 273 nm, and the injection volume is 2.5 μL.

7. The method of catalytic conversion of CO2 by the cuprous ion- loaded melamine-based functionalized hypercrosslinked polymer according to claim 1, characterized in that: In step 5, when the used catalyst is washed, water and methanol are used for washing 3 times.

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