Preparation and application of a high-performance double-copper structure composite nanocatalytic material

Abstract

The conjugated diyne produced by the self-coupling of terminal alkynes is an important chemical intermediate. The present invention uses a metal-organic framework PCN-222 (Cu) with a high surface area and carboxyl porphyrin as a ligand as a carrier, and uses a double solvent method to impregnate solutions of different copper concentrations into the one-dimensional pores of the MOF to obtain Cu 2+ @PCN‑222(Cu), which was then reduced with a reducing agent to yield composite catalysts with varying copper loadings. The Cu@PCN‑222(Cu) nanoparticles, containing 1.9 wt% copper nanoparticles, exhibited excellent catalytic activity for the self-coupling of terminal alkynes at 50°C and atmospheric pressure. This activity stems from the catalyst's bifunctional nature: PCN‑222(Cu) not only stabilizes the Cu NPs and controls size selectivity, but both PCN‑222(Cu) and Cu NPs serve as active sites, synergistically catalyzing the coupling reaction. This synergistic effect between the two components can enhance catalytic performance or expand the reaction range. Under the combined catalysis of the dual copper structure, the composite catalyst exhibits excellent catalytic activity and stability for the self-coupling of terminal alkynes.

Description

Technical Field

[0001] The present invention relates to the field of metal-organic framework material technology and applied catalysis, specifically to the field of nanomaterials. Specifically, it relates to a method for preparing a catalyst for synthesizing conjugated dialkynes, the self-coupling products of terminal alkynes. A composite catalytic material, Cu@PCN-222(Cu), is formed by embedding copper nanoparticles in a porphyrin metal-organic framework as a carrier. This material, with its double-copper structure, exhibits excellent catalytic activity for the self-coupling of terminal alkynes to form conjugated dialkynes. Background Art

[0002] The self-coupling reaction of terminal alkynes is an important tool in organic synthesis and is currently widely used in pharmaceutical synthesis and materials research. In recent years, various metal-catalyzed Glaser coupling reactions have been reported. However, Glaser coupling reactions in organic phases often suffer from complex procedures, the requirement for co-catalysts and excess base, high reaction temperatures, and long reaction times, thus requiring further improvement.

[0003] In the Glaser reaction, Cu(I) is commonly used as a catalyst. Later research on catalytic oxidation reactions has largely relied on transition metals to catalyze the self-coupling reaction of terminal alkynes. Transition metals used include Cu, Ag, Ag, and Pt, with Cu and Pd being the most common catalysts. Compared to precious metal catalysts such as gold and palladium, copper catalysts are more affordable and do not pose environmental risks due to the use of phosphine or amine ligands. The copper-catalyzed Glaser reaction typically uses a CuCl / TMEDA catalytic system with oxygen as the oxidant and can be carried out in most solvents. However, its efficiency is very low when applied to the coupling reaction of alkoxy-substituted alkynes. In addition to copper salt catalysis, the use of metallic copper nanoparticles for the homogeneous and heterogeneous coupling of alkynes has also been reported. This reaction system is clean and offers high yields, making it a novel, efficient, and environmentally friendly method. However, due to their high surface activity, copper nanoparticles are prone to aggregation and oxidation, leading to loss of activity, limiting their role in catalytic reactions. Therefore, controlling the stability, size, and morphology of copper nanoparticles is a key factor in achieving efficient catalysis.

[0004] MOFs based on porphyrin structural units, such as PCN-222, can be used as catalysts. They possess one-dimensional pores and a stable structure. Their large pore size (up to 3.7 nm) limits the size of metal nanoparticles and facilitates diffusion during reactions. Furthermore, the porphyrin unit structure exhibits catalytic oxidation activity, making it an excellent template for synthesizing composite nanocatalytic materials. Dispersing copper nanoparticles within the MOF pores to form a composite catalyst for terminal alkyne self-coupling presents a challenge, which is addressed by the present invention. Summary of the Invention

[0005] To address the shortcomings and deficiencies of the aforementioned prior art, the present invention provides a high-performance dual-copper composite catalytic nanomaterial. The catalytic material is composed of a copper porphyrin metal-organic framework (PCN-222(Cu)) and copper nanoparticles. The pores of the metal-organic framework not only limit the size and crystal form of the copper nanoparticles, stabilizing their activity, but also the high porosity and one-dimensional pores of PCN-222(Cu) facilitate the transport of the reaction substrate, terminal alkynes, and coupling products, significantly improving the activity and reaction efficiency of the nano-copper catalyst. Furthermore, the copper metalloporphyrin ligand also participates in the catalytic process of the coupling reaction products. The resulting composite catalytic material exhibits excellent chemical properties as a catalyst for terminal alkyne self-coupling reactions.

[0006] The present invention provides a preparation method of the high-performance double-copper structure catalytic nanomaterial and its application in alkyne self-coupling.

[0007] The technical solutions of the present invention are as follows:

[0008] A high-performance dual-copper structure composite catalytic nanomaterial is composed of copper nanoparticles grown in the pores of PCN-222(Cu) and a copper porphyrin metal-organic framework (labeled as Cu@PCN-222(Cu)). The metal-organic framework has a rod-like structure that embeds copper nanoparticles. The copper nanoparticles are evenly dispersed in the pores. The rod-like crystal structure has a diameter of about 500nm and a length of about 5-8 μm. The encapsulated copper nanoparticles are 1-3.5nm in size.

[0009] According to the present invention, the X-ray diffraction (XRD) spectrum of the Cu@PCN-222(Cu) composite material corresponds to the crystal structure of Cu and the crystal structure of PCN-222(Cu).

[0010] According to the present invention, the preparation method of the above-mentioned high-performance double copper structure composite catalytic nanomaterial Cu@PCN-222 (Cu) is as follows Figure 1 As shown, the following steps are included:

[0011] (1) Synthesis of the copper porphyrin metal-organic framework: After ultrasonically dissolving the zirconium source and benzoic acid in a polar solvent, Cu-TCPP (5,10,15,20-tetrakis(4-carboxyphenyl)copperporphyrin) (50 mg) was added and ultrasonicated again. The mixture was transferred to a 25 ml reactor and heated in an oven for reaction. After cooling to room temperature, the brick-red solid obtained by filtration was washed with DMF and dried in vacuo to obtain PCN-222(Cu).

[0012] (2) PCN-222(Cu) solid was added to DMF solvent, HCl was added, and the mixture was stirred under heating conditions. After filtering, the mixture was washed several times with DMF and acetone in sequence. The solid was then transferred to an acetone solution and stirred at room temperature to obtain activated PCN-222(Cu).

[0013] (3) 100 mg of activated PCN-222(Cu) was added to a 100 ml round-bottom flask, a non-polar solvent was added, and ultrasonic dispersion was performed. The copper source was slowly added dropwise under vigorous stirring. After stirring, the non-polar solvent was removed. The solid was dried and reduced with a reducing agent. The solid was collected by filtration, washed with a large amount of ethanol, and dried to obtain a high-performance dual-copper structure composite catalytic nanomaterial. The products were named Cu@PCN-222(Cu)-1, Cu@PCN-222(Cu)-2, ​​and Cu@PCN-222(Cu)-3 according to different copper loadings.

[0014] According to the present invention, preferably, the zirconium source in step (1) is zirconium chloride, the solvent DMF is N,N-diethylformamide, and the hydrothermal reaction is carried out in a polytetrafluoroethylene high-pressure reactor.

[0015] According to the present invention, preferably, the amount of the zirconium source in step (1) is 70 mg, and the amount of benzoic acid is 2700 mg.

[0016] According to the present invention, preferably, the reaction temperature of the hydrothermal reaction in step (1) is 120° C., the reaction time is 48 h, and the volume of the polar solvent is 8 ml.

[0017] According to the present invention, preferably, the solvent in step (2) is DMF, the volume is 70 ml, the stirring temperature is 100° C., the reaction time is 12 h, the concentration of hydrochloric acid is 1 M, and the volume is 1 ml.

[0018] According to the present invention, preferably, the volume of acetone in step (2) is 50 ml, the stirring time in acetone is 10 h, and the drying temperature is 80°C.

[0019] According to the present invention, preferably, in step (3), the non-polar solvent is n-hexane, the copper source is a copper chloride solution, and the reducing agent is an ethanol solution of NaBH4.

[0020] According to the present invention, preferably, in step (3), the volume of the non-polar solvent is 20 ml, the ultrasonic time is 20 min, the concentration of copper chloride is (0.2 M, 0.6 M, 1.0 M), the volume is 80 μl, and the stirring time is 4 h.

[0021] According to the present invention, preferably, the drying time after removing the non-polar solvent in step (3) is 8 hours, the concentration of NaBH4 is 0.2M, and the molar ratio of NaBH4 to copper ion is 5:1.

[0022] According to the present invention, preferably, the solid collected after reduction with a reducing agent is repeatedly washed with anhydrous ethanol 5 times and dried at 70° C. in a vacuum to obtain a Cu@PCN-222 (Cu) composite catalytic nanomaterial.

[0023] The present invention also provides the application of the above-mentioned high-performance double-copper structure composite catalytic nanomaterial in catalyzing the terminal alkyne self-coupling reaction. The specific application test is as follows:

[0024] Cu@PCN-222 (Cu) (100 mg) and the co-catalyst tetramethylethylenediamine (TMEDA) (300 μl) were added to a 100-ml round-bottom flask. 10 ml of 1,4-dioxane and 20 ml of chloroform were then added as solvents. 20 mmol of various terminal alkynes were added as substrates, and the reaction was stirred at 50°C for 24 hours. After completion of the reaction, the mixture was cooled to room temperature and the catalyst was isolated by high-speed centrifugation. The liquid mixture was then added with 60 ml of chloroform and washed with a saturated NH4Cl solution. The organic phase was dried over anhydrous water and concentrated in vacuo to obtain the reaction product.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] 1. This invention prepares a novel nanocomposite catalytic system, Cu@PCN-222(Cu), based on porphyrin MOFs. This catalyst combines the advantages of porphyrin MOFs and nanoparticles: while the MOF acts as a threshold limiter and stabilizes the nanoparticles, the porphyrin copper structure within its framework also serves as a reactive center, synergistically catalyzing the Glaser self-coupling reaction of terminal alkynes with the confined nanocopper particles.

[0027] 2. The present invention uses phenylacetylene as the reaction substrate, CHCl₃ / dioxane as the reaction solvent, and TMEDA as the ligand. When 100 mg of Cu@PCN-222(Cu) with varying nanocopper contents is used as the catalyst, 1,4-diphenylbutadiyne is produced in good yields (45.3–85.0%). Cu@PCN-222(Cu) with 1.9% nanocopper ion content exhibits the strongest catalytic activity and the highest product yield, surpassing results reported in the literature. Both linear and aromatic terminal alkynes can be efficiently converted to their corresponding products. DETAILED DESCRIPTION

[0028] The following describes in detail the method for preparing a high-performance dual-copper structure composite catalytic nanomaterial according to the present invention, in conjunction with specific embodiments and examples. The raw materials used in the examples are all commercially available products. The main experimental reagents used are listed below: copper chloride dihydrate (CuCl2·2H2O, ≥99.9%), tetramethylethylenediamine (TMEDA, ≥98%), zirconium tetrachloride (ZrCl4), N,N-diethylformamide (DEF, 99.5%), n-hexane (99%), and sodium borohydride (NaBH4, ≥98%).

[0029] The present invention is described below by way of example, and the present invention includes but is not limited to the following embodiments:

[0030] Example 1

[0031] (1) Preparation of copper porphyrin metal organic framework material (PCN-222(Cu))

[0032] ZrCl4 (70 mg) and benzoic acid (2700 mg) were ultrasonically dissolved in 8 mL of DDF. Cu-TCPP (50 mg) was added and ultrasonication continued for 30 minutes. The mixture was transferred to a 25 mL reactor and heated in a 120°C oven for 48 hours. After cooling to room temperature, the brick-red solid was collected by filtration, washed with DMF, and dried in vacuo to yield PCN-222(Cu).

[0033] (2) Preparation of copper nanoparticles and porphyrin-based metal-organic framework composites (Cu@PCN-222)

[0034] Solid PCN-222(Cu) was added to DMF, followed by HCl and stirring under heating. After filtration, the solid was washed several times with DMF and acetone. The solid was then transferred to acetone and stirred at room temperature to obtain activated PCN-222(Cu). Three 100mg portions of activated PCN-222 were added to a 100ml round-bottom flask, followed by 20ml of hexane. Ultrasonic dispersion was performed for 20 minutes. Under vigorous stirring, 80μl of 0.2M, 0.6M, and 1.0M CuCl2 solutions were slowly added dropwise. After stirring for 4 hours, the hexane was removed, the solid was dried for 8 hours, and then reduced with 0.2M NaBH4 ethanolic solution. The solid was collected by filtration, washed with copious amounts of ethanol, and dried. The resulting copper nanoparticles and porphyrin-based metal-organic framework composites (Cu@PCN-222(Cu)) had copper loadings of 0.65%, 1.9%, and 2.7%, respectively.

[0035] (3) The characterization test of the double copper structure composite catalytic nanomaterial catalyst (Cu@PCN-222(Cu)) obtained in the above steps is as follows:

[0036] Scanning electron microscopy (SEM): The scanning electron microscopy image of the double copper structure composite catalytic nanomaterial (Cu@PCN-222(Cu)) is shown in the attached Figure 2 As shown, the rod-like structure of MOF was not destroyed after embedding low-concentration copper nanoparticles, and the high specific surface area and porosity of the metal-organic framework were retained. When the concentration of the added copper chloride was 1M, the rod-like structure was destroyed after reduction.

[0037] Transmission electron microscopy (TEM): The transmission electron microscopy image of the double copper structure composite catalytic nanomaterial Cu@PCN-222 (Cu) is shown in the attached Figure 3 As shown in the figure, the morphology of Cu@PCN-222(Cu)-2 with 1.9% copper nanoparticle content is the same as that of the carrier PCN-222(Cu), showing a rod-like structure with a diameter of 500nm. The TEM image clearly shows the presence of copper nanoparticles. The loaded nanoparticles are evenly distributed on PCN-222(Cu) and are relatively uniform in size ( Figure 3 b). The interplanar spacings measured from the HRTEM image are 0.127nm, 0.182nm, and 0.209nm, corresponding to the (220), (200), and (111) planes of copper, respectively ( Figure 3 d).

[0038] Infrared spectrum analysis: The infrared spectrum of the catalyst is as shown in the attached Figure 4 Compared with the monomeric porphyrin TCPP, Cu-TCPP, PCN-222(Cu) and Cu@PCN-222(Cu) have the highest ion density at 1000 cm -1 Strong symmetrical Cu-N bond stretching appears near 2+ Coordinated with the porphyrin ring to form copper porphyrin. And after further introduction of copper into the pores, it did not affect the Cu 2+ In this way, in the composite nanocatalytic material Cu@PCN-222(Cu), active sites are formed where two copper structures, porphyrin copper and nano copper, coexist.

[0039] N2 adsorption-desorption analysis: Nitrogen adsorption-desorption isotherms show that the specific surface area of ​​PCN-222(Cu) is 2256m 2 / g, and the pore size is calculated to be 3.6nm according to the density functional theory (DFT) method. Figure 5From the results, as the content of Cu nanoparticles increases, the specific surface area decreases. The order of BET surface area is PCN-222(Cu)>Cu@PCN-222(Cu)-1>Cu@PCN-222(Cu)-2>Cu@PCN-222(Cu)-3. Among them, PCN-222(Cu)-3 has a significantly lower specific surface area due to the collapse of the PCN-222 structure due to the excessive size of the copper nanoparticles (Table 1). Figure 5 b shows that after loading with copper nanoparticles, the peak intensity of the 3.6 nm mesopores decreases. These results indicate that although a portion of the mesopores in the framework are occupied by copper nanoparticles, the MOF still retains a portion of mesopores that are conducive to the diffusion of substrates and solvents, ensuring efficient reaction.

[0040] Table 1. Specific surface area and nano-copper content of composite catalytic materials

[0041]

[0042] (4) The performance test of the double copper structure composite catalytic nanomaterial catalyst obtained above is as follows:

[0043] The self-coupling reaction of phenylacetylene was used as a model reaction. Table 2 shows the self-coupling reaction of phenylacetylene to produce 1,4-diphenylbutadiyne in the presence of Cu@PCN-222(Cu) with varying copper loadings. Using CHCl₃ / dioxane as the reaction solvent and TMEDA as the ligand, when 100 mg of Cu@PCN-222(Cu) with varying nanocopper loadings was used as the catalyst, Cu@PCN-222(Cu)-2 with a copper nanoparticle content of 1.9% exhibited the strongest catalytic activity, achieving a maximum product yield of 81.7%. Both linear and aromatic terminal alkynes were efficiently converted to their corresponding products (Table 3).

[0044] After four catalytic cycles, the yield of Cu@PCN-222(Cu)-2 in the self-coupling reaction of phenylacetylene to 1,4-diphenylbutadiyne was 80.2%, and it still maintained high catalytic activity.

[0045] The above examples illustrate that the dual-copper structure composite catalytic nanomaterial is a rod-shaped material composed of embedded copper nanoparticles and a metal-organic framework. The uniformly dispersed nanoparticles are efficient catalytic active sites. At the same time, the copper porphyrin units on the metal-organic framework also participate in the reaction. The MOF still retains a portion of mesopores that are conducive to the diffusion of substrates and solvents, which can ensure the efficient progress of the reaction and thus has excellent catalytic performance for terminal alkyne self-coupling.

[0046] Table 2 Results of the self-coupling reaction of phenylacetylene to 1,4-diphenylbutadiyne catalyzed by Cu@PCN-222(Cu)

[0047]

[0048] Table 3 Reaction results of different terminal alkyne coupling catalyzed by Cu@PCN-222(Cu)

[0049]

[0050] BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Attachment Figure 1 This is a flow chart for the preparation of the double-copper structure composite catalytic nanomaterial Cu@PCN-222(Cu) obtained in Example 1.

[0052] Attachment Figure 2 This is an SEM image of the double-copper structure composite catalytic nanomaterial Cu@PCN-222(Cu) obtained in Example 1.

[0053] Attachment Figure 3 This is a TEM image of the double-copper structure composite catalytic nanomaterial Cu@PCN-222(Cu) obtained in Example 1.

[0054] Attachment Figure 4 This is the FTIR graph of the double-copper structure composite catalytic nanomaterial Cu@PCN-222(Cu) obtained in Example 1.

[0055] Attachment Figure 5 This is a diagram showing the nitrogen adsorption and desorption of the double-copper structure composite catalytic nanomaterial Cu@PCN-222(Cu) obtained in Example 1.

Claims

1. A high-performance double-copper structure composite catalytic nanomaterial, characterized in that: The catalytic material is composed of a copper porphyrin metal organic framework PCN-222 (Cu) and copper nanoparticles grown and confined in the MOF pores, labeled Cu@PCN-222 (Cu). The material has a rod-shaped crystal structure with a length of 5-8 μm and a diameter of 0.5 μm. The copper nanoparticles have a size of 1 to 3.5 nm. The preparation of the catalytic material includes the following steps: (1) Synthesis of copper porphyrin metal organic framework: After the zirconium source and benzoic acid were ultrasonically dissolved in a polar solvent, 50 mg of 5,10,15,20-tetrakis(4-carboxyphenyl)copper porphyrin was added and ultrasonication continued. The mixture was transferred to a 25 ml reactor and heated in an oven for reaction. After cooling to room temperature, the brick red solid obtained was washed and filtered with DMF and vacuum dried to obtain PCN-222(Cu); (2) PCN-222 (Cu) activated with acetone was added to a 100 ml round-bottom flask, and then a non-polar solvent was added, ultrasonically dispersed, and the copper source was slowly added dropwise under vigorous stirring. After stirring, the solvent was removed, the solid was dried and reduced with a reducing agent, the solid was collected by filtration, washed with ethanol and dried to obtain a high-performance dual-copper structure composite catalytic nanomaterial; different nano-copper particle loadings can be obtained according to different concentrations of the copper source, and the copper particle loading is between 0-5%.

2. The catalytic nanomaterial according to claim 1, characterized in that In its structure, a copper ion is complexed to the center of the porphyrin ring, and elemental copper particles are located in the pores; the organic ligand in the framework structure is tetrakis(4-carboxyphenyl)copperporphyrin, and the node is a zirconium ion. The structure was confirmed to be PCN-222(Cu) by X-ray diffraction; the elemental copper nanoparticle structure was also confirmed by XRD-ray diffraction.

3. The method for preparing the high-performance double-copper structure composite catalytic nanomaterial according to claim 1 comprises the following steps: (1) Synthesis of copper porphyrin metal organic framework: After the zirconium source and benzoic acid were ultrasonically dissolved in a polar solvent, 50 mg of 5,10,15,20-tetrakis(4-carboxyphenyl)copper porphyrin was added and ultrasonication continued. The mixture was transferred to a 25 ml reactor and heated in an oven for reaction. After cooling to room temperature, the brick red solid obtained was washed and filtered with DMF and vacuum dried to obtain PCN-222(Cu); (2) PCN-222 (Cu) activated with acetone was added to a 100 ml round-bottom flask, and then a non-polar solvent was added, ultrasonically dispersed, and the copper source was slowly added dropwise under vigorous stirring. After stirring, the solvent was removed, the solid was dried and reduced with a reducing agent, the solid was collected by filtration, washed with ethanol and dried to obtain a high-performance dual-copper structure composite catalytic nanomaterial; different nano-copper particle loadings can be obtained according to different concentrations of the copper source, and the copper particle loading is between 0-5%.

4. The method for preparing a high-performance double-copper structure composite catalytic nanomaterial according to claim 3, characterized in that: The zirconium source in step (1) is zirconium chloride, the polar solvent is N,N-diethylformamide, and the hydrothermal reaction is carried out in a polytetrafluoroethylene high-pressure reactor.

5. The method for preparing a high-performance double-copper structure composite catalytic nanomaterial according to claim 3, characterized in that: The amount of the zirconium source in step (1) is 50-100 mg, the amount of benzoic acid is 1000-3000 mg, the reaction temperature of the hydrothermal reaction is 80-150° C., the reaction time is 36-72 h, and the volume of the polar solvent is 5-20 ml.

6. The method for preparing a high-performance double-copper structure composite catalytic nanomaterial according to claim 3, characterized in that: In step (2), the solvent is DMF, the volume is 50-100 ml, the stirring temperature is 8-120° C., and the reaction time is 8-20 h; the volume of acetone is 20-100 ml, and the stirring time in acetone is 8-15 h.

7. The method for preparing a high-performance double-copper structure composite catalytic nanomaterial according to claim 3, characterized in that: In step (2), the non-polar solvent is n-hexane, the copper source is one of copper chloride, copper nitrate, and copper sulfate solution, the reducing agent is an ethanol solution of NaBH4, the volume of the non-polar solvent is 10-50 ml, the concentration of copper chloride is 0.2-1.0 M, the volume is 5-100 μl, and the stirring time is 4-8 h.

8. The method for preparing a high-performance double-copper structure composite catalytic nanomaterial according to claim 3, characterized in that: After removing the non-polar solvent in step (2), the drying time is 5-10 hours, the concentration of NaBH4 is 0.1-0.5M, and the molar ratio of NaBH4 to copper ion is (1-8):

1.

9. Application of the high-performance dual-copper structure composite catalytic nanomaterial according to claim 1 in the terminal alkyne self-coupling reaction, using phenylacetylene as the substrate, CHCl3 / dioxane as the reaction solvent, and tetramethylethylenediamine as the ligand. When 100 mg of Cu@PCN-222(Cu) with different nano-copper contents is used as the catalyst, the yield of 1,4-diphenylbutadiyne is good, ranging from 45.0–85.0%. Among them, Cu@PCN-222(Cu) with a nano-Cu content of 1.9% has the strongest catalytic activity and the highest product yield.

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