A hollow sandwich composite structure catalyst constructed by noble metal and covalent organic framework and a preparation method and application thereof

Abstract

The application provides a hollow sandwich composite structure catalyst constructed by a noble metal and a covalent organic framework and a preparation method and application thereof. The hollow sandwich composite structure catalyst comprises, from inside to outside, a hollow core layer, a sandwich layer and an outer shell layer. The hollow core layer and the outer shell layer are respectively and independently covalent organic framework materials. The sandwich layer is distributed with noble metal. The application uses COF as the hollow core layer and the outer shell layer, uses noble metal particles as the sandwich layer and uniformly distributes the noble metal particles in the sandwich layer, so that the noble metal particles can realize high conversion rate, excellent selectivity, high turnover frequency and good stability at the same time in the selective catalytic semi-hydrogenation reaction of different alkyne-containing organic matters.

Description

Technical Field

[0001] This invention belongs to the field of selective hydrogenation catalyst technology, specifically relating to a hollow sandwich composite catalyst constructed from a noble metal and a covalent organic framework, its preparation method, and its application. Background Technology

[0002] The semi-hydrogenation of alkynyl alcohols to enols is a key process in the production of many important fine chemicals, including vitamins, pharmaceuticals, fragrances, synthetic materials, corrosion inhibitors, and synthetic fibers. The synthesis of vitamin E, for example, involves various enols, such as isophyllene, linalool, and 2-methyl-3-buten-2-ol (MBE). Generally, these enols are obtained through the semi-hydrogenation of alkynyl alcohols. Currently, palladium-based catalysts are commonly used in industry for the semi-hydrogenation of alkynyl alcohols. However, because it is difficult to distinguish the adsorption capacity of C≡C and C=C groups for active metal sites, it is challenging to avoid the formation of over-hydrogenation products (alkane).

[0003] Currently, catalysts are typically modified with another metal or a reversible organic adsorbent (such as pyridine or quinoline) to block or isolate surface active sites to some extent. The most well-known example is the Lindlar catalyst, which modifies Pd / CaCO3 with Pb and quinoline. However, the addition of Pb leads to severe heavy metal contamination and activity loss, and it is difficult to simultaneously achieve high conversion, excellent selectivity, high turnover frequency (TOF), and good stability. Therefore, the development of a high-performance, lead-free, selective semi-hydrogenation catalyst is urgently needed.

[0004] Covalent organic frameworks (COFs), often referred to as crystalline porous networks, exhibit potential research value in heterogeneous catalysis due to their high porosity, well-defined structure, ease of modification, and designable topologies. Furthermore, COFs combined with metal nanoparticles (MNPs) can produce synergistic catalytic effects, demonstrating significantly enhanced catalytic performance compared to single-component materials. To date, typical yolk-shell structures have been constructed; however, nanoparticles are typically larger than 10 nm, resulting in weak interactions with the shell and thus relatively low catalytic performance. Another approach involves dispersing metal nanoparticles throughout a hollow shell using conventional impregnation and reduction methods; however, the size and distribution of metal nanoparticles are difficult to control precisely.

[0005] Therefore, there is an urgent need to develop a novel composite catalyst and its preparation method that can regulate the distribution of metal nanoparticles in the catalyst to achieve high catalytic efficiency. Summary of the Invention

[0006] The purpose of this invention is to provide a hollow sandwich composite catalyst constructed from a noble metal and a covalent organic framework, its preparation method and application. The hollow sandwich composite catalyst has high activity, high selectivity and excellent stability, and exhibits excellent performance in the selective catalytic semi-hydrogenation of different alkyne-containing organic compounds.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a hollow sandwich composite structure catalyst constructed from a noble metal and a covalent organic framework, wherein the hollow sandwich composite structure catalyst comprises, from the inside out, a hollow core layer, an interlayer and an outer shell layer.

[0009] The hollow core layer and the outer shell layer are each independently covalent organic framework materials;

[0010] The interlayer contains precious metals (PM).

[0011] The hollow sandwich composite catalyst provided by this invention has a hollow core layer and a hollow shell layer with COF as the core layer and a noble metal particle as the interlayer, which is uniformly distributed in the interlayer. The hollow sandwich composite catalyst has a thin shell layer, which is easy to diffuse and has a strong adsorption capacity for substrates. This makes it exhibit excellent performance in the selective catalytic semi-hydrogenation of different alkyne-containing organic compounds, and can simultaneously achieve high conversion rate, excellent selectivity, high turnover frequency and good stability.

[0012] As a preferred technical solution of the present invention, the general formula of the hollow sandwich composite structure catalyst is HoCOF@PM@COF.

[0013] Preferably, the covalent organic framework material includes any one or a combination of at least two of TpPa-1, TpPa-2, or TpBD.

[0014] Preferably, the precious metal includes any one or a combination of at least two of Pd, Pt, or Rh.

[0015] Preferably, based on the total mass of the hollow sandwich composite catalyst, the mass content of the precious metal is 0.01wt%-2wt%, for example, it can be 0.02wt%, 0.05wt%, 0.07wt%, 0.1wt%, 0.3wt%, 0.5wt%, 0.7wt%, 1wt%, 1.2wt%, 1.5wt%, or 1.75wt%, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0016] In this invention, the catalyst is loaded with only trace amounts of precious metal particles to achieve highly efficient selective semi-hydrogenation conversion of alkynes.

[0017] As a preferred technical solution of the present invention, the thickness of the hollow core layer is 15-35nm, for example, it can be 17nm, 19nm, 20nm, 22nm, 25nm, 27nm, 30nm, 32nm or 34nm, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0018] Preferably, the thickness of the outer shell layer is 15-35nm, for example, it can be 17nm, 19nm, 20nm, 22nm, 25nm, 27nm, 30nm, 32nm or 34nm, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0019] In this invention, the type of covalent organic framework material and the thickness of its hollow core layer and outer shell layer can be adjusted according to actual needs.

[0020] Preferably, the average particle size of the precious metal is 1-3 nm, for example, it can be 1.2 nm, 1.5 nm, 1.7 nm, 2 nm, 2.2 nm, 2.4 nm, 2.5 nm, 2.7 nm or 2.9 nm, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] In a second aspect, the present invention provides a method for preparing a hollow sandwich composite structure catalyst as described in the first aspect, the preparation method comprising the following steps:

[0022] (1) Mix ZIFs, phenylenediamine monomer, aldehyde monomer and first solvent, and carry out first stirring reaction to obtain ZIFs@Am-COF;

[0023] (2) Mix the noble metal solution and the ZIFs@Am-COF solution obtained in step (1) and carry out a second stirring reaction to obtain ZIFs@Am-COF@PM;

[0024] (3) Mix phenylenediamine monomer, aldehyde monomer, ZIFs@Am-COF@PM from step (2) and the first solvent, and carry out a third stirring reaction to obtain ZIFs@Am-COF@PM@Am-COF;

[0025] (4) Disperse the ZIFs@Am-COF@PM@Am-COF obtained in step (3) in a second solvent and perform acid etching to obtain HoCOF@PM@COF.

[0026] The preparation method provided by this invention synthesizes hollow covalent organic framework materials (HoCOF) using the sacrificial template (ZIFs) method, and further constructs a hollow sandwich composite structure catalyst; the preparation method is easy to operate, uses simple equipment, is easy to implement, and is highly efficient.

[0027] In this invention, the COF material obtained in steps (1) to (3) is an amorphous COF material (Am-COF). Subsequently, acid etching can not only transform the COF material from disordered to an ordered crystalline framework, but also selectively remove the ZIF template.

[0028] As a preferred technical solution of the present invention, the ZIFs in step (1) include ZIF-8.

[0029] In this invention, since ZIFs will eventually be etched away and their addition amount has no effect on the performance of the catalyst, this invention does not specifically limit the amount of ZIFs used, and those skilled in the art can adjust the addition amount according to actual needs.

[0030] In this invention, the ZIFs material is the conventional ZIFs material used in the field, which can be prepared by technicians or purchased commercially. Therefore, the preparation process and specific conditions of the ZIFs material are not specifically limited here.

[0031] In this invention, the specific method of mixing in step (1) is as follows: add phenylenediamine monomer first solvent dropwise to ZIFs first solvent, stir for 10 min, and then continue to add aldehyde monomer first solvent dropwise.

[0032] Preferably, the phenylenediamine monomer in step (1) comprises any one or a combination of at least two of 2,5-dimethyl-1,4-phenylenediamine (Pa-2), p-phenylenediamine (Pa-1), or benzidine (BD), wherein typical but non-limiting combinations include: a combination of 2,5-dimethyl-1,4-phenylenediamine and p-phenylenediamine, a combination of p-phenylenediamine and benzidine, a combination of 2,5-dimethyl-1,4-phenylenediamine, p-phenylenediamine, and benzidine, etc.

[0033] Preferably, the mass concentration of the phenylenediamine monomer in the first solvent in step (1) is 0.1-1 mg / mL, for example, it can be 0.2 mg / mL, 0.3 mg / mL, 0.4 mg / mL, 0.5 mg / mL, 0.6 mg / mL, 0.7 mg / mL or 0.9 mg / mL, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0034] Preferably, the aldehyde monomer in step (1) includes trialdehyde phloroglucinol (Tp).

[0035] Preferably, the mass concentration of the aldehyde monomer in the first solvent in step (1) is 0.1-1 mg / mL, for example, it can be 0.2 mg / mL, 0.3 mg / mL, 0.4 mg / mL, 0.5 mg / mL, 0.6 mg / mL, 0.7 mg / mL or 0.9 mg / mL, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] Preferably, the mass ratio of phenylenediamine monomer to aldehyde monomer in step (1) is 1:(1-6), for example, it can be 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5 or 1:5.5, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] Preferably, in step (1), the first solvent comprises tetrahydrofuran.

[0038] Preferably, the temperature of the first stirring reaction in step (1) is 20-35°C, for example, it can be 22°C, 25°C, 27°C, 30°C, 32°C, 33°C or 34°C, etc., but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0039] Preferably, the stirring reaction time in step (1) is 20-30h, for example, it can be 21h, 22h, 23h, 24h, 25h, 26h, 27h, 28h or 29h, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] In this invention, the first stirring reaction is followed by a solid-liquid separation and washing process, wherein the solvents used for washing are tetrahydrofuran and methanol, respectively. Furthermore, this invention does not specifically limit the technical means of solid-liquid separation, as long as it can separate the products of this stage.

[0041] As a preferred technical solution of the present invention, the noble metal solution in step (2) includes a noble metal and an alcohol solvent.

[0042] In this invention, the alcohol solvent includes ethylene glycol or ethanol.

[0043] In this invention, the specific method of mixing in step (2) is as follows: adding a noble metal solution dropwise into the ZIFs@Am-COF solution.

[0044] Preferably, the precious metal includes any one or a combination of at least two of Pd, Pt, or Rh.

[0045] In this invention, the precious metal materials can be prepared by technicians or purchased commercially, so the preparation process of the precious metal materials is not specifically limited here.

[0046] In this invention, the average particle size of the precious metal is 1-4 nm, for example, it can be 1.2 nm, 1.5 nm, 1.7 nm, 2 nm, 2.2 nm, 2.4 nm, 2.5 nm, 2.7 nm, 3 nm, 3.2 nm, 3.5 nm, 3.7 nm or 3.9 nm, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0047] Preferably, the ZIFs@Am-COF solution in step (2) comprises ZIFs@Am-COF and methanol.

[0048] Preferably, the temperature of the second stirring reaction in step (2) is 20-35°C, for example, it can be 22°C, 25°C, 27°C, 30°C, 32°C, 33°C or 34°C, etc., but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0049] Preferably, the second stirring reaction time in step (2) is 1-3 hours, for example, it can be 1.2 hours, 1.5 hours, 1.7 hours, 2 hours, 2.2 hours, 2.5 hours, 2.7 hours or 2.9 hours, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0050] In this invention, the second stirring reaction is followed by a solid-liquid separation and washing process, wherein the solvent used for washing is tetrahydrofuran; furthermore, this invention does not specifically limit the technical means of solid-liquid separation, as long as it can separate the products of this stage.

[0051] As a preferred technical solution of the present invention, the mass concentration of the phenylenediamine monomer in the first solvent in step (3) is 0.1-1 mg / mL, for example, it can be 0.2 mg / mL, 0.3 mg / mL, 0.4 mg / mL, 0.5 mg / mL, 0.6 mg / mL, 0.7 mg / mL or 0.9 mg / mL, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0052] In this invention, the specific mixing method in step (3) is as follows: add phenylenediamine monomer first solvent dropwise to ZIFs@Am-COF@PM first solvent, stir for 10 min, and then continue to add aldehyde monomer first solvent dropwise.

[0053] Preferably, the mass concentration of the aldehyde monomer in the first solvent in step (3) is 0.1-1 mg / mL, for example, it can be 0.2 mg / mL, 0.3 mg / mL, 0.4 mg / mL, 0.5 mg / mL, 0.6 mg / mL, 0.7 mg / mL or 0.9 mg / mL, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0054] Preferably, the mass ratio of phenylenediamine monomer to aldehyde monomer in step (3) is 1:(1-6), for example, it can be 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5 or 1:5.5, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0055] Preferably, the temperature of the third stirring reaction in step (3) is 20-35℃, for example, it can be 22℃, 25℃, 27℃, 30℃, 32℃, 33℃ or 34℃, etc., but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0056] Preferably, the third stirring reaction time in step (3) is 20-30h, for example, it can be 21h, 22h, 23h, 24h, 25h, 26h, 27h, 28h or 29h, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0057] In this invention, the third stirring reaction is followed by a solid-liquid separation and washing process, wherein the solvent used for washing is tetrahydrofuran solution; furthermore, this invention does not specifically limit the technical means of solid-liquid separation, as long as it can separate the products of this stage.

[0058] As a preferred technical solution of the present invention, the mass-volume ratio of ZIFs@Am-COF@PM@Am-COF and the second solvent in step (4) is (13-23):1mg / mL, for example, it can be 14:1mg / mL, 15:1mg / mL, 17:1mg / mL, 19:1mg / mL, 20:1mg / mL or 22:1mg / mL, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0059] Preferably, in step (4), the second solvent is a mixed solution of 1,4-dioxane and acetic acid.

[0060] In this invention, the concentration of acetic acid is 5.5-6.5 mmol, for example, it can be 5.6 mmol, 5.7 mmol, 5.8 mmol, 6 mmol, 6.2 mmol or 6.4 mmol, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0061] Preferably, the volume ratio of 1,4-dioxane to acetic acid is (3-10):1, for example, it can be 4:1, 5:1, 6:1, 7:1, 8:1 or 9:1, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0062] Preferably, the acid etching temperature in step (4) is 30-130℃, for example, it can be 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃ or 120℃, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0063] Preferably, the acid etching time in step (4) is 68-80h, for example, it can be 70h, 71h, 72h, 73h, 74h, 75h, 76h, 77h or 78h, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0064] In this invention, the acid etching process further includes sequential solid-liquid separation and washing, wherein the solvents used for washing are tetrahydrofuran, ultrapure water, and acetone, respectively. Furthermore, this invention does not specifically limit the technical means of solid-liquid separation, as long as it can separate the products of this stage.

[0065] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0066] (1) Mix ZIFs, phenylenediamine monomer, aldehyde monomer and first solvent, and carry out the first stirring reaction at a temperature of 20-35℃ for 20-30h to obtain ZIFs@Am-COF;

[0067] (2) Mix the noble metal solution and the ZIFs@Am-COF solution described in step (1), and carry out a second stirring reaction at a temperature of 20-35℃ for 1-3 hours to obtain ZIFs@Am-COF@PM;

[0068] (3) Mix phenylenediamine monomer, aldehyde monomer, ZIFs@Am-COF@PM from step (2) and the first solvent, and carry out a third stirring reaction at a temperature of 20-35℃ for 20-30h to obtain ZIFs@Am-COF@PM@Am-COF;

[0069] (4) Disperse the ZIFs@Am-COF@PM@Am-COF obtained in step (3) in a mixed solution of 1,4-dioxane and acetic acid at a mass-to-volume ratio of (13-23):1 mg / mL, and perform acid etching at a temperature of 30-130℃ for 68-80 h to obtain HoCOF@PM@COF;

[0070] The phenylenediamine monomer includes any one or a combination of at least two of 2,5-dimethyl-1,4-phenylenediamine, p-phenylenediamine, or benzidine; the mass concentration of the phenylenediamine monomer in the first solvent is 0.1-1 mg / mL; the aldehyde monomer includes trialdehyde phloroglucinol; the mass concentration of the aldehyde monomer in the first solvent is 0.1-1 mg / mL; the mass ratio of the phenylenediamine monomer to the aldehyde monomer is 1:(1-6); the first solvent includes tetrahydrofuran.

[0071] Thirdly, the present invention provides an application of the hollow sandwich composite structure catalyst as described in the first aspect, wherein the hollow sandwich composite structure catalyst is used to catalyze the selective half-hydrogenation reaction of alkyne-containing organic compounds (a schematic diagram of the catalytic process is shown below).

[0072]

[0073] Where: A is an alkyne organic compound, B is an alkene organic compound, and C is an alkane organic compound.

[0074] In this invention, the alkyne-containing organic compound includes 2-methyl-3-butyn-2-ol (MBY), phenylacetylene, or 3-hexyn-1-ol, preferably 2-methyl-3-butyn-2-ol.

[0075] The hollow sandwich composite catalyst provided by this invention achieves a conversion rate of 96.5% and a selectivity of 93.7% in the catalytic half-hydrogenation of MBY to MBE at a low temperature of 10°C, with a turnover frequency (TOF) as high as 47542 h. -1 It has high catalytic efficiency; in addition, the catalyst has good stability, and the conversion rate and selectivity remain basically unchanged after 10 cycles of use.

[0076] Compared with the prior art, the present invention has the following beneficial effects:

[0077] (1) The hollow sandwich composite catalyst provided by the present invention uses COF materials as the hollow core layer and the outer shell layer, respectively, and noble metal particles as the interlayer and are evenly distributed in the interlayer. When selectively catalyzing the semi-hydrogenation reaction of different alkyne-containing organic compounds, it can simultaneously achieve high conversion rate, excellent selectivity, high turnover frequency and good stability.

[0078] (2) The preparation method provided by the present invention uses the sacrificial template method to synthesize hollow sandwich composite catalysts. The type and thickness of the shell can be adjusted by changing the type and amount of ligands added. The loading of noble metals can be flexibly adjusted by changing the amount of noble metal nanoparticles added as needed. The preparation method is easy to operate, has simple equipment, is easy to implement, and is highly efficient. Attached Figure Description

[0079] Figure 1 TEM image of the hollow sandwich composite catalyst prepared in Example 1;

[0080] Figure 2 TEM image of the hollow sandwich composite catalyst prepared in Example 1;

[0081] Figure 3 TEM image of the hollow sandwich composite catalyst prepared in Example 1;

[0082] Figure 4 This is a particle size distribution diagram of Pd metal in the hollow sandwich composite catalyst prepared in Example 1;

[0083] Figure 5 The XRD pattern of the hollow sandwich composite catalyst prepared in Example 1;

[0084] Figure 6 This is a TEM image of the hollow sandwich composite catalyst prepared in Example 2;

[0085] Figure 7 This is a TEM image of the hollow sandwich composite catalyst prepared in Example 3;

[0086] Figure 8 This is a TEM image of the hollow sandwich composite catalyst prepared in Example 4;

[0087] Figure 9 This is a TEM image of the hollow sandwich composite catalyst prepared in Example 5;

[0088] Figure 10 TEM image of the hollow covalent organic framework catalyst prepared in Comparative Example 3;

[0089] Figure 11 TEM image of the hollow covalent organic framework catalyst prepared in Comparative Example 3;

[0090] Figure 12 The image shows a TEM image of the selective semi-hydrogenation reaction of MBY catalyzed by the hollow sandwich composite catalyst prepared in Example 1.

[0091] Figure 13The image shows a TEM image of the selective semi-hydrogenation reaction of MBY catalyzed by the hollow sandwich composite catalyst prepared in Example 1.

[0092] Figure 14 The graph shows the conversion and selectivity results of the hollow sandwich composite catalyst prepared in Example 1 after 10 cycles of catalytic selective semi-hydrogenation of MBY. Detailed Implementation

[0093] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0094] Example 1

[0095] This embodiment provides a hollow sandwich composite catalyst constructed from a noble metal and a covalent organic framework and its preparation method. The hollow sandwich composite catalyst comprises, from the inside out, a hollow core layer, an interlayer, and an outer shell layer.

[0096] The hollow sandwich composite catalyst has the general formula HoTpPa-2@Pd@TpPa-2; both the hollow core layer and the outer shell layer are TpPa-2; and Pd nanoparticles are distributed in the interlayer.

[0097] Based on the total mass of the hollow sandwich composite catalyst, the Pd mass content is 0.064 wt%.

[0098] The preparation method of the hollow sandwich composite structure catalyst includes the following steps:

[0099] (1) Disperse ZIF-8 in 45 mL of tetrahydrofuran, then add 5 mL of Pa-2 solution dropwise, stir for 10 min, then add 5 mL of Tp solution dropwise, and then carry out the first stirring reaction at 25 °C for 24 h. Collect the solid by centrifugation and wash it several times with tetrahydrofuran and methanol to obtain ZIF-8@Am-TpPa-2.

[0100] The specific preparation method of ZIF-8 is as follows: 1.68g of zinc nitrate hexahydrate and 3.70g of 2-methylimidazole are ultrasonically dispersed in 40mL of methanol, and then the zinc nitrate hexahydrate solution is quickly poured into the 2-methylimidazole solution. After stirring at 25℃ for 24h, the solid is collected by centrifugation and washed several times with methanol.

[0101] (2) Add 3.3 mL of Pd particle ethylene glycol solution with a particle size of 2 nm to 10 mL of ZIF-8@Am-TpPa-2 methanol solution, and then carry out a second stirring reaction at 25 °C for 2 h. Collect the solid by centrifugation and wash it several times with tetrahydrofuran to obtain ZIF-8@Am-TpPa-2@Pd.

[0102] (3) Add 5 mL of Pa-2 solution dropwise to 45 mL of ZIF-8@Am-TpPa-2@Pd tetrahydrofuran solution, stir for 10 min, then add 5 mL of Tp solution dropwise, and then carry out a third stirring reaction at 25 °C for 24 h. Collect the solid by centrifugation and wash it several times with tetrahydrofuran to obtain ZIF-8@Am-TpPa-2@Pd@Am-TpPa-2;

[0103] (4) 50 mg ZIF-8@Am-TpPa-2@Pd@Am-TpPa-2 was dispersed in a mixed solution of 1,4-dioxane (3 mL) and acetic acid (0.8 mL 6 mmol), and then transferred to a pressure-resistant bottle. Acid etching was performed at 120 °C for 72 h. The solid was collected by centrifugation and washed several times with tetrahydrofuran, ultrapure water and acetone to obtain HoTpPa-2@Pd@TpPa-2.

[0104] The Pa-2 solution was prepared by dissolving 18.8 mg of Pa-2 in 5 mL of tetrahydrofuran; the Tp solution was prepared by dissolving 20 mg of Tp in 5 mL of tetrahydrofuran.

[0105] Figure 1-3 All images are TEM images of the catalysts prepared in this embodiment. Figure 4 This is a Pd metal particle size distribution diagram of the catalyst prepared in this embodiment, from... Figure 1-4 It can be seen that the Pd nanoparticles are uniformly distributed in the interlayer, with a Pd particle size of 2.0 nm. The thickness of both the TpPa-2 hollow core layer and the outer shell layer is 16.3 nm.

[0106] Figure 5 The XRD pattern of the catalyst prepared in Example 1 is shown below; Figure 5 It can be seen that after acid etching, COF successfully transformed from a disordered to an ordered crystalline framework, while selectively removing the ZIF-8 template.

[0107] Example 2

[0108] This embodiment provides a hollow sandwich composite catalyst constructed from a noble metal and a covalent organic framework, and its preparation method. Except that the general formula of the hollow sandwich composite catalyst is HoTpPa-1@Pd@TpPa-1, that is, the covalent organic framework material is TpPa-1, all other conditions are the same as in Example 1.

[0109] The TEM image of the catalyst prepared in this embodiment is as follows. Figure 6 As shown.

[0110] Example 3

[0111] This embodiment provides a hollow sandwich composite catalyst constructed from a noble metal and a covalent organic framework, and its preparation method. Except that the general formula of the hollow sandwich composite catalyst is HoTpBD@Pd@TpBD, that is, the covalent organic framework material is TpBD, all other conditions are the same as in Example 1.

[0112] The TEM image of the catalyst prepared in this embodiment is as follows. Figure 7 As shown.

[0113] Example 4

[0114] This embodiment provides a hollow sandwich composite catalyst constructed from a noble metal and a covalent organic framework, and its preparation method. Except that the general formula of the hollow sandwich composite catalyst is HoTpPa-1@Pt@TpPa-1, that is, the covalent organic framework material is TpPa-1 and the noble metal is Pt, all other conditions are the same as in Example 1.

[0115] The TEM image of the catalyst prepared in this embodiment is as follows. Figure 8 As shown.

[0116] Example 5

[0117] This embodiment provides a hollow sandwich composite catalyst constructed from a noble metal and a covalent organic framework, and its preparation method. Except that the general formula of the hollow sandwich composite catalyst is HoTpPa-1@Rh@TpPa-1, that is, the covalent organic framework material is TpPa-1 and the noble metal is Pt, all other conditions are the same as in Example 1.

[0118] The TEM image of the catalyst prepared in this embodiment is as follows. Figure 9 As shown.

[0119] Example 6

[0120] This embodiment provides a hollow sandwich composite catalyst constructed from a noble metal and a covalent organic framework and its preparation method. Except for the thickness of the hollow core layer and the outer shell layer being 25 nm, i.e., adjusting the amount of Pa-2 and Tp, all other conditions are the same as in Example 1.

[0121] Example 7

[0122] This embodiment provides a hollow sandwich composite catalyst constructed from a noble metal and a covalent organic framework and its preparation method. Except for the thickness of the hollow core layer and the outer shell layer being 32 nm, i.e., adjusting the amount of Pa-2 and Tp, all other conditions are the same as in Example 1.

[0123] Example 8

[0124] This embodiment provides a hollow sandwich composite catalyst constructed from a noble metal and a covalent organic framework and its preparation method. Except for the thickness of the hollow core layer and the outer shell layer being 45 nm, i.e., adjusting the amount of Pa-2 and Tp, all other conditions are the same as in Example 1.

[0125] Example 9

[0126] This embodiment provides a hollow sandwich composite catalyst constructed from a noble metal and a covalent organic framework, and its preparation method, except that the preparation method of the hollow sandwich composite catalyst includes the following steps:

[0127] (1) Disperse ZIF-8 in 45 mL of tetrahydrofuran, then add 5 mL of Pa-2 solution dropwise, stir for 10 min, then add 5 mL of Tp solution dropwise, and then carry out the first stirring reaction at 35 °C for 20 h. Collect the solid by centrifugation and wash it several times with tetrahydrofuran and methanol to obtain ZIF-8@Am-TpPa-2.

[0128] The specific preparation method of ZIF-8 is as follows: 1.68g of zinc nitrate hexahydrate and 3.70g of 2-methylimidazole are ultrasonically dispersed in 40mL of methanol, and then the zinc nitrate hexahydrate solution is quickly poured into the 2-methylimidazole solution. After stirring at 25℃ for 24h, the solid is collected by centrifugation and washed several times with methanol.

[0129] (2) Add 3.3 mL of Pd particle ethylene glycol solution with a particle size of 2 nm to 10 mL of ZIF-8@Am-TpPa-2 methanol solution, and then carry out a second stirring reaction at 35 °C for 1 h. Collect the solid by centrifugation and wash it several times with tetrahydrofuran to obtain ZIF-8@Am-TpPa-2@Pd.

[0130] (3) Add 5 mL of Pa-2 solution dropwise to 45 mL of ZIF-8@Am-TpPa-2@Pd tetrahydrofuran solution, stir for 10 min, then add 5 mL of Tp solution dropwise, and then carry out a third stirring reaction at 25 °C for 24 h. Collect the solid by centrifugation and wash it several times with tetrahydrofuran to obtain ZIF-8@Am-TpPa-2@Pd@Am-TpPa-2;

[0131] (4) 40 mg ZIF-8@Am-TpPa-2@Pd@Am-TpPa-2 was dispersed in a mixed solution of 1,4-dioxane (3 mL) and acetic acid (0.8 mL 6 mmol), and then transferred to a pressure-resistant bottle. Acid etching was performed at 130 °C for 70 h. The solid was collected by centrifugation and washed several times with tetrahydrofuran, ultrapure water and acetone to obtain HoTpPa-2@Pd@TpPa-2.

[0132] The Pa-2 solution was prepared by dissolving 18.8 mg of Pa-2 in 5 mL of tetrahydrofuran; the Tp solution was prepared by dissolving 20 mg of Tp in 5 mL of tetrahydrofuran.

[0133] All other conditions are the same as in Example 1.

[0134] Comparative Example 1

[0135] This comparative example provides a sandwich composite catalyst constructed from a noble metal and a covalent organic framework and its preparation method. Except that the general formula of the sandwich composite catalyst is ZIF-8@Am-TpPa-2@Pd@Am-TpPa-2, all other conditions are the same as in Example 1.

[0136] Comparative Example 2

[0137] This comparative example provides a hollow composite catalyst constructed from a noble metal and a covalent organic framework, and its preparation method. Except that the general formula of the hollow composite catalyst is HoTpPa-2@Pd, i.e., no outer shell layer is provided, all other conditions are the same as in Example 1.

[0138] Comparative Example 3

[0139] This comparative example provides a hollow covalent organic framework catalyst and its preparation method. Except that the general formula of the hollow covalent organic framework catalyst is HoTpPa-2, all other conditions are the same as in Example 1.

[0140] TEM images of the catalyst prepared in this comparative example are shown below. Figure 10-11 As shown.

[0141] Comparative Example 4

[0142] This comparative example provides a noble metal nanoparticle and its preparation method. Except that the noble metal nanoparticle is PdNPs, all other conditions are the same as in Example 1.

[0143] The catalysts obtained in Examples 1, 6-9 and Comparative Examples 1-4 were used to catalyze the selective half-hydrogenation reaction of MBY. The catalytic test results are shown in Table 1.

[0144] Figure 12-13 All images are TEM images of the selective semi-hydrogenation reaction of MBY catalyzed by the hollow sandwich composite catalyst prepared in Example 1. Figure 12-13 As can be seen, the catalyst still retains its intact morphology, indicating that the hollow sandwich composite structure catalyst has excellent stability.

[0145] The specific testing method is as follows: The catalyst prepared above (where the content of the active component Pd in ​​the catalyst is 0.0144 mg) is dispersed in 5 mL of ethyl acetate. 2 mmol MBY is added to the above solution. After the solution is mixed evenly, it is transferred to a 50 mL polytetrafluoroethylene-lined stainless steel reactor. Hydrogen gas is introduced and replaced 5 times to remove the air in the reactor. The final hydrogen pressure is 0.1 MPa. Then, the reactor is placed in a 10°C water bath and magnetically stirred at a speed of 300 rad / min. The reaction is stopped after the required reaction time is reached (wherein, under these reaction conditions and stirring speed, the effect of mass transfer inside and outside the reactor on the catalytic performance is not considered). After the reaction is completed, the catalyst is separated by centrifugation. The resulting reaction solution is filtered through a 0.22 μm filter membrane and analyzed by a gas chromatograph (Shimadzu GC-2014C, Japan).

[0146] Table 1

[0147] Example 1 18 96.5 93.7 47542 Example 6 22 99.4 93.5 40067 Example 7 25 92.1 92.7 32670 Example 8 35 97.2 92.5 24628 Example 9 19 94.5 93.5 44107 Comparative Example 1 70 96.6 81.2 12238 Comparative Example 2 45 94.7 93.9 18662 Comparative Example 3 190 - - - Comparative Example 4 270 92.9 91.1 3051

[0148] Among them, gas chromatography was used to determine the alkyne conversion rate and olefin selectivity; the TOF value was calculated by dividing the number of moles of the conversion substrate by the number of moles of the noble metal and the reaction time.

[0149] As shown in Table 1:

[0150] (1) The hollow sandwich composite structure catalyst and its preparation method provided by the present invention can be used to convert MBY into the value-added product MBE while achieving high conversion rate, excellent selectivity and high turnover frequency.

[0151] (2) A comparison of Examples 1 and 6-8 shows that when the thickness of the hollow core layer and the outer shell layer increases, the catalytic performance of the catalyst becomes worse due to the increased diffusion resistance.

[0152] (3) Comparison of Example 1 and Comparative Examples 1-3 shows that when the catalyst is a solid sandwich composite structure, the catalytic performance of the catalyst is worse due to the obstruction of diffusion; when the catalyst does not have a shell layer, the noble metal nanoparticles will agglomerate and fall off due to the lack of protection of the shell layer, which will reduce the catalytic performance of the catalyst; when a hollow covalent organic framework is used as the catalyst, there is no hydrogenation active component, so no hydrogenation product is generated.

[0153] The catalyst obtained in Example 1 was used to catalyze the selective half-hydrogenation reaction of phenylacetylene and 3-hexyne-1-ol. The catalytic method was consistent with that of MBY catalysis, and the catalytic test results are shown in Table 2.

[0154] Table 2

[0155]

[0156] As shown in Table 2, the catalyst provided by this invention can not only be used for the efficient catalytic selective semi-hydrogenation of alkynes and alcohols, but also for the selective semi-hydrogenation of various terminal alkynes and internal alkynes, thus having a wide range of applications.

[0157] The catalyst obtained in Example 1 was subjected to a cycle stability test. The catalytic conditions were consistent with the first MBY catalysis. The test results are as follows: Figure 14 As shown. By Figure 14 It can be seen that after 10 consecutive cycles of the experiment, the conversion rate of the substrate can still be maintained at over 95%, and the selectivity of the product can still be maintained at over 92%, which shows that the catalyst provided by the present invention has excellent stability.

[0158] The applicant declares that the detailed structural features of the present invention are illustrated through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components selected in the present invention, additions of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A hollow sandwich composite catalyst constructed from a noble metal and a covalent organic framework, characterized in that, The hollow sandwich composite structure catalyst comprises, from the inside out, a hollow core layer, an interlayer, and an outer shell layer; The hollow core layer and the outer shell layer are each independently a covalent organic framework material; the covalent organic framework material includes any one or a combination of at least two of TpPa-1, TpPa-2, or TpBD; The interlayer contains a precious metal; the precious metal includes any one or a combination of at least two of Pd, Pt, or Rh. The hollow sandwich composite catalyst is used to catalyze the selective semi-hydrogenation reaction of alkyne-containing organic compounds.

2. The hollow sandwich composite structure catalyst according to claim 1, characterized in that, Based on the total mass of the hollow sandwich composite catalyst, the mass content of precious metals is 0.01wt%-2wt%.

3. The hollow sandwich composite structure catalyst according to claim 1 or 2, characterized in that, The thickness of the hollow core layer is 15-35 nm.

4. The hollow sandwich composite structure catalyst according to claim 1, characterized in that, The thickness of the outer shell layer is 15-35 nm.

5. The hollow sandwich composite structure catalyst according to claim 1, characterized in that, The average particle size of the precious metal is 1-3 nm.

6. A method for preparing a hollow sandwich composite structure catalyst as described in any one of claims 1-5, characterized in that, The preparation method includes the following steps: (1) Mix ZIFs, phenylenediamine monomer, aldehyde monomer and first solvent, and carry out the first stirring reaction to obtain ZIFs@Am-COF; (2) Mix the noble metal solution and the ZIFs@Am-COF solution described in step (1) and carry out a second stirring reaction to obtain ZIFs@Am-COF@PM; (3) Mix phenylenediamine monomer, aldehyde monomer, ZIFs@Am-COF@PM from step (2) and the first solvent, and carry out a third stirring reaction to obtain ZIFs@Am-COF@PM@Am-COF; (4) Disperse the ZIFs@Am-COF@PM@Am-COF obtained in step (3) in a second solvent and perform acid etching to obtain HoCOF@PM@COF.

7. The preparation method according to claim 6, characterized in that, The ZIFs mentioned in step (1) include ZIF-8.

8. The preparation method according to claim 6, characterized in that, The phenylenediamine monomer in step (1) includes any one or a combination of at least two of 2,5-dimethyl-1,4-phenylenediamine, p-phenylenediamine, or benzidine.

9. The preparation method according to claim 6, characterized in that, The mass concentration of the phenylenediamine monomer in the first solvent in step (1) is 0.1-1 mg / mL.

10. The preparation method according to claim 6, characterized in that, The aldehyde monomer in step (1) includes trialdehyde phloroglucinol.

11. The preparation method according to claim 6, characterized in that, The mass concentration of the aldehyde monomer in the first solvent in step (1) is 0.1-1 mg / mL.

12. The preparation method according to claim 6, characterized in that, The mass ratio of phenylenediamine monomer to aldehyde monomer in step (1) is 1:(1-6).

13. The preparation method according to claim 6, characterized in that, Step (1) The first solvent includes tetrahydrofuran.

14. The preparation method according to claim 6, characterized in that, In step (1), the temperature of the first stirring reaction is 20-35℃.

15. The preparation method according to claim 6, characterized in that, Step (1) The first stirring reaction time is 20-30h.

16. The preparation method according to claim 6, characterized in that, The precious metal solution in step (2) includes a precious metal and an alcohol solvent.

17. The preparation method according to claim 6, characterized in that, The ZIFs@Am-COF solution in step (2) includes ZIFs@Am-COF and methanol.

18. The preparation method according to claim 6, characterized in that, In step (2), the temperature of the second stirring reaction is 20-35℃.

19. The preparation method according to claim 6, characterized in that, Step (2) The second stirring reaction time is 1-3 hours.

20. The preparation method according to claim 6, characterized in that, The mass concentration of the phenylenediamine monomer in the first solvent in step (3) is 0.1-1 mg / mL.

21. The preparation method according to claim 6, characterized in that, The mass concentration of the aldehyde monomer in the first solvent in step (3) is 0.1-1 mg / mL.

22. The preparation method according to claim 6, characterized in that, The mass ratio of phenylenediamine monomer to aldehyde monomer in step (3) is 1:(1-6).

23. The preparation method according to claim 6, characterized in that, The temperature of the third stirring reaction in step (3) is 20-35℃.

24. The preparation method according to claim 6, characterized in that, The third stirring reaction in step (3) takes 20-30 hours.

25. The preparation method according to claim 6, characterized in that, In step (4), the mass-to-volume ratio of ZIFs@Am-COF@PM@Am-COF and the second solvent is (13-23):1 mg / mL.

26. The preparation method according to claim 6, characterized in that, Step (4) The second solvent is a mixed solution of 1,4-dioxane and acetic acid.

27. The preparation method according to claim 26, characterized in that, The volume ratio of 1,4-dioxane to acetic acid is (3-10):

1.

28. The preparation method according to claim 6, characterized in that, The acid etching temperature in step (4) is 30-130℃.

29. The preparation method according to claim 6, characterized in that, The acid etching time in step (4) is 68-80 hours.

30. The preparation method according to claim 6, characterized in that, The preparation method includes the following steps: (1) Mix ZIFs, phenylenediamine monomer, aldehyde monomer and first solvent, and carry out the first stirring reaction at a temperature of 20-35℃ for 20-30h to obtain ZIFs@Am-COF; (2) Mix the noble metal solution and the ZIFs@Am-COF solution described in step (1), and carry out a second stirring reaction at a temperature of 20-35℃ for 1-3 hours to obtain ZIFs@Am-COF@PM; (3) Mix phenylenediamine monomer, aldehyde monomer, ZIFs@Am-COF@PM from step (2) and the first solvent, and carry out a third stirring reaction at a temperature of 20-35℃ for 20-30h to obtain ZIFs@Am-COF@PM@Am-COF; (4) Disperse the ZIFs@Am-COF@PM@Am-COF obtained in step (3) in a mixed solution of 1,4-dioxane and acetic acid at a mass-to-volume ratio of (13-23):1 mg / mL, and perform acid etching at a temperature of 30-130℃ for 68-80 h to obtain HoCOF@PM@COF; The phenylenediamine monomer includes any one or a combination of at least two of 2,5-dimethyl-1,4-phenylenediamine, p-phenylenediamine, or benzidine; the mass concentration of the phenylenediamine monomer in the first solvent is 0.1-1 mg / mL; the aldehyde monomer includes trialdehyde phloroglucinol; the mass concentration of the aldehyde monomer in the first solvent is 0.1-1 mg / mL; the mass ratio of the phenylenediamine monomer to the aldehyde monomer is 1:(1-6); the first solvent includes tetrahydrofuran.

31. The application of a hollow sandwich composite structure catalyst as described in any one of claims 1-5, characterized in that, The hollow sandwich composite catalyst is used to catalyze the selective semi-hydrogenation reaction of alkyne-containing organic compounds.

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