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

Abstract

The application provides a sandwich structure catalyst constructed by noble metal and metal organic framework and a preparation method and application thereof, the sandwich structure catalyst comprises an inner core, a sandwich layer and an outer shell layer from inside to outside; the inner core comprises a Zr-MOF material; the sandwich layer comprises a noble metal nanoparticle layer; and the outer shell layer is a MOF material constructed based on a second organic ligand and a Zr central metal, wherein the second organic ligand comprises any one of tetrakis(4-carboxyphenyl) cobalt porphyrin, tetrakis(4-carboxyphenyl) iron porphyrin or tetrakis(4-carboxyphenyl) nickel porphyrin. The Zr-MOF is used as the inner core, the Zr-MOF(M) is used as the outer shell layer, and the noble metal nanoparticles are used as the sandwich layer and are uniformly distributed in the sandwich layer, so that when the catalyst is used for catalyzing the selective hydrogenation and deoxidation reaction of halogenated nitrobenzene, high conversion rate, excellent selectivity, high turnover frequency and good stability can be simultaneously achieved.

Description

Technical Field

[0001] This invention belongs to the field of selective hydrogenation deoxygenation catalyst technology, and relates to a sandwich structure catalyst constructed from noble metals and metal-organic frameworks, its preparation method and application. Background Technology

[0002] Halogenated anilines are important organic intermediates and basic chemical raw materials, widely used in pharmaceuticals, pesticides, dyes, and other fields. Currently, the industrial production of halogenated anilines mainly relies on the catalytic hydrogenation of halogenated nitrobenzene. Iron powder is commonly used to reduce halogenated nitrobenzene under acidic conditions to obtain the corresponding halogenated anilines. This method easily generates large amounts of toxic solid waste, causing environmental pollution. Currently, selective hydrogenation deoxygenation is one of the main methods for preparing halogenated anilines. However, dehalogenation side reactions easily occur during catalytic hydrogenation, reducing the product yield and making it difficult to simultaneously achieve high conversion, excellent selectivity, high time-of-conversion (TOF), and good stability. Therefore, the development of efficient, highly selective, and highly stable hydrogenation catalysts is urgently needed.

[0003] CN112547124B discloses a selective hydrogenation catalyst for halonitrobenzene, its preparation method, and a method for selective hydrogenation of halonitrobenzene, comprising: Pd@MIL-101-Fx, where x = 3, 5, 7; x represents the number of small molecule carbon chains introduced on the MOF; the preparation method of the selective hydrogenation catalyst for halonitrobenzene comprises: introducing an aqueous solution of palladium precursor into MIL-101-NH2, reducing it with ammonia borane, and then modifying it with fluorinated carboxylic anhydride to obtain the catalyst Pd@MIL-101-Fx.

[0004] Metal-organic frameworks (MOFs) possess excellent application prospects in catalysis due to their high specific surface area, wide pore size range, and rich variety of functional groups. Furthermore, the combination of MOFs and metal nanoparticles (MNPs) can produce a synergistic catalytic effect, exhibiting significantly enhanced catalytic performance compared to single-component materials. The morphology, composition distribution, and interfacial interactions of the composite material are key factors determining its catalytic performance, directly affecting its catalytic performance in hydrogenation reactions.

[0005] Traditional impregnation reduction methods disperse MNPs in MOFs. However, the composite structures prepared by this method cannot precisely control the size and distribution of metal nanoparticles. Another typical type of catalyst is the core-shell structure catalyst. Typically, the core nanoparticles are large in size, with limited contact interfaces and weak interactions with the shell. This results in limited space for morphology and structure regulation, making it difficult to optimize for excellent catalytic performance.

[0006] Therefore, there is an urgent need to develop a new composite catalyst and to precisely design and control the size and spatial distribution of metal nanoparticles in the composite catalyst to achieve high catalytic efficiency. Summary of the Invention

[0007] The purpose of this invention is to provide a sandwich structure catalyst constructed from noble metals and metal-organic frameworks, its preparation method and application. The sandwich structure catalyst uses Zr-MOF as the core and Zr-MOF(M) as the outer shell, with noble metal nanoparticles as the interlayer and uniformly distributed in the interlayer, so that the catalyst exhibits excellent catalytic activity, selectivity and stability.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a sandwich structure catalyst constructed from a noble metal and a metal-organic framework, wherein the sandwich structure catalyst consists of a core, an interlayer, and an outer shell layer from the inside out.

[0010] The core comprises Zr-MOF material;

[0011] The interlayer includes a layer of noble metal nanoparticles;

[0012] The outer shell is a MOF material constructed based on a second organic ligand (M-TCPP) and a Zr central metal, wherein the second organic ligand includes any one of tetra(4-carboxyphenyl)cobalt porphyrin (Co-TCPP), tetra(4-carboxyphenyl)iron porphyrin (Fe-TCPP), or tetra(4-carboxyphenyl)nickel porphyrin (Ni-TCPP).

[0013] In this invention, the general formula of the sandwich structure catalyst is Zr-MOF@noble metal nanoparticles@Zr-MOF(M), wherein Zr-MOF is preferably PCN-221.

[0014] The sandwich-structured catalyst provided by this invention uses Zr-MOF as the core and Zr-MOF(M) as the outer shell, with noble metal nanoparticles as the interlayer and uniformly distributed in the interlayer. It can not only control the size and spatial distribution of noble metal nanoparticles in the composite catalyst, but also achieve a synergistic effect between the M metal in the M-TCPP ligand and the noble metal nanoparticles, so that the catalyst has better catalytic activity, selectivity and stability.

[0015] It is worth noting that porphyrin-based metal-organic frameworks (PMOFs) combine the characteristics of porphyrin and porous metal-organic framework materials, such as high porosity, well-defined structure, ease of modification, and designable topology. Furthermore, zirconium metal sources have high stability, so Zr-porphyrin-based metal-organic frameworks are selected as the core. In addition, metalloporphyrin ligands can promote the catalytic effect of noble metal nanoparticles, so Zr-MOF(M) metal-organic frameworks are selected as the outer shell layer.

[0016] As a preferred embodiment of the present invention, the first organic ligand of the Zr-MOF material includes tetrakis(4-carboxyphenyl)porphyrin (H2TCPP).

[0017] Preferably, the second organic ligand is tetra(4-carboxyphenyl)cobalt porphyrin (Co-TCPP) or tetra(4-carboxyphenyl)iron porphyrin (Fe-TCPP).

[0018] Preferably, in the Zr-MOF material, the molar ratio of the Zr central metal to the first organic ligand is 1:(0.1-2), for example, it can be 1:0.2, 1:0.5, 1:0.7, 1:1, 1:1.2, 1:1.5, 1:1.7 or 1:1.9, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0019] Preferably, the molar ratio of the Zr central metal to the second organic ligand is 1:(0.1-1), for example, it can be 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8 or 1:0.9, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] As a preferred embodiment of the present invention, the noble metal nanoparticles in the interlayer include Pt nanoparticles or Pd nanoparticles.

[0021] Preferably, based on the total mass of the sandwich structure catalyst, the mass content of the noble metal nanoparticles is 0.2wt%-1wt%, for example, it can be 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, or 0.9wt%, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] In this invention, the sandwich-structured catalyst contains only a small amount of noble metal nanoparticles, yet it can achieve a highly efficient selective hydrodeoxygenation reaction of halonitrobenzenes. However, if the loading of noble metal nanoparticles is too high, the catalyst production cost increases significantly without a noticeable improvement in catalytic performance; conversely, if the loading of noble metal nanoparticles is too low, the catalytic performance will decrease.

[0023] As a preferred technical solution of the present invention, the diameter of the core is 400-600nm, for example, it can be 420nm, 450nm, 470nm, 490nm, 500nm, 520nm, 550nm, 570nm or 590nm, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0024] Preferably, the average particle size of the noble metal nanoparticles in the interlayer is 2-5 nm, for example, it can be 2.2 nm, 2.5 nm, 2.7 nm, 3 nm, 3.2 nm, 3.5 nm, 3.7 nm, 4 nm, 4.2 nm, 4.5 nm, 4.7 nm or 4.9 nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] Preferably, the thickness of the outer shell layer is 10-30nm, for example, it can be 12nm, 15nm, 16nm, 18nm, 20nm, 22nm, 25nm, 26nm or 28nm, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 10-20nm.

[0026] In this invention, if the outer shell layer is too thick, it will lead to an increase in mass transfer resistance and a decrease in catalyst efficiency; if the outer shell layer is too thin, it will lead to a decrease in catalyst stability and selectivity.

[0027] In a second aspect, the present invention provides a method for preparing a sandwich-structured catalyst as described in the first aspect, the method comprising the following steps:

[0028] (1) Disperse Zr-MOF in a solvent, add a noble metal nanoparticle solution to it, and stir to obtain Zr-MOF@noble metal nanoparticles;

[0029] (2) Mix the zirconium source, the second organic ligand, the regulator and the solvent to obtain the precursor solution;

[0030] (3) Mix the Zr-MOF@noble metal nanoparticle solution from step (1) with the precursor solution from step (2) and carry out a second solvothermal reaction to obtain the sandwich structure catalyst.

[0031] The preparation method provided by this invention involves coating a layer of noble metal nanoparticles onto a Zr-MOF material, and then coating the outermost layer with another Zr-MOF(M) material to obtain the sandwich-structured catalyst. This preparation method is easy to operate, requires simple equipment, is readily achievable, and is highly efficient.

[0032] As a preferred technical solution of the present invention, the preparation method of Zr-MOF in step (1) includes:

[0033] A zirconium source, modifier, and solvent are mixed, heated, cooled, and then a first organic ligand is added to carry out a first solvothermal reaction to obtain Zr-MOF.

[0034] Preferably, the zirconium source includes zirconium oxychloride and / or zirconium tetrachloride.

[0035] Preferably, the regulator includes benzoic acid.

[0036] Preferably, the solvent includes N,N-dimethylformamide (DMF).

[0037] Preferably, the molar ratio of the zirconium source to the regulator is 1:(30-50), for example, it can be 1:32, 1:35, 1:37, 1:40, 1:42, 1:45, 1:47 or 1:49, etc., but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0038] Preferably, the solid-liquid ratio of the zirconium source to the solvent is (3-8):1 mg / mL, for example, it can be 4 mg / mL, 4.5 mg / mL, 5 mg / mL, 5.5 mg / mL, 6 mg / mL or 7 mg / mL, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0039] Preferably, the heating temperature is 75-85℃, for example, it can be 76℃, 77℃, 78℃, 79℃, 80℃, 81℃, 82℃, 83℃ or 84℃, etc., but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] Preferably, the heating time is 0.5-2 hours, for example, 0.7 hours, 0.9 hours, 1 hour, 1.2 hours, 1.4 hours, 1.5 hours, 1.6 hours or 1.8 hours, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] In this invention, the molar ratio of the zirconium source to the first organic ligand is 1:(0.1-2).

[0042] Preferably, the temperature of the first solvothermal reaction is 110-130°C, for example, it can be 112°C, 115°C, 117°C, 120°C, 122°C, 125°C, 127°C or 129°C, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0043] Preferably, the time for the first solvothermal reaction is 4-6 hours, for example, 4.2 hours, 4.5 hours, 4.7 hours, 5 hours, 5.2 hours, 5.5 hours, 5.7 hours or 5.9 hours, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0044] In this invention, the first solvothermal reaction is followed by sequential solid-liquid separation, washing, and drying. The solvents used for washing are DMF and acetone, respectively. Furthermore, this invention does not specifically limit the technical means or parameters of solid-liquid separation and drying, and those skilled in the art can select them according to the actual situation.

[0045] As a preferred technical solution of the present invention, the noble metal nanoparticle solution in step (1) includes noble metal nanoparticles and alcohol solvent.

[0046] Preferably, the noble metal nanoparticles include Pt nanoparticles or Pd nanoparticles.

[0047] In this invention, the precious metal nanoparticles can be prepared by technicians or purchased commercially, so the preparation process of the precious metal nanoparticles is not specifically limited here.

[0048] In this invention, the average particle size of the noble metal nanoparticles is 2-5 nm.

[0049] Preferably, the stirring temperature in step (1) 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.

[0050] Preferably, the stirring time in step (1) 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.

[0051] In this invention, after stirring in step (1), solid-liquid separation and washing are performed sequentially, wherein the solvent used for washing is DMF; in addition, this invention does not specifically limit the technical means of solid-liquid separation, as long as it can separate the products of this stage.

[0052] As a preferred technical solution of the present invention, the solvents used in steps (1) and (2) are both N,N-dimethylformamide.

[0053] Preferably, the zirconium source in step (2) includes zirconium oxychloride and / or zirconium tetrachloride.

[0054] Preferably, the regulator includes benzoic acid.

[0055] Preferably, the molar ratio of zirconium source to regulator in step (2) is 1:(30-50), for example, it can be 1:32, 1:35, 1:37, 1:40, 1:42, 1:45, 1:47 or 1:49, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0056] In this invention, the molar ratio of the zirconium source to the second organic ligand in step (2) is 1:(0.1-1).

[0057] Preferably, the solid-liquid ratio of the zirconium source to the solvent in step (2) is (3-8):1 mg / mL, for example, it can be 4 mg / mL, 4.5 mg / mL, 5 mg / mL, 5.5 mg / mL, 6 mg / mL or 7 mg / mL, etc., but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0058] As a preferred technical solution of the present invention, the volume ratio of the Zr-MOF@noble metal nanoparticle solution to the precursor solution in step (3) is 1:(0.5-2), for example, it can be 1:0.7, 1:0.9, 1:1, 1:1.2, 1:1.5, 1:1.7 or 1:1.9, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0059] Preferably, the temperature of the second solvothermal reaction in step (3) is 110-130℃, for example, it can be 112℃, 115℃, 117℃, 120℃, 122℃, 125℃, 127℃ or 129℃, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0060] Preferably, the time for the second solvothermal reaction in step (3) is 1-1.5h, for example, it can be 1.1h, 1.2h, 1.3h or 1.4h, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0061] In this invention, the second solvothermal reaction further includes sequential solid-liquid separation, washing, and drying, wherein the solvents used for washing are DMF and acetone in sequence; in addition, this invention does not specifically limit the technical means and parameters of solid-liquid separation and drying, and those skilled in the art can select them according to the actual situation.

[0062] Thirdly, the present invention provides an application of the sandwich-structured catalyst as described in the first aspect, wherein the sandwich-structured catalyst is used to catalyze selective hydrogenation reactions, preferably selective hydrogenation reactions of halonitrobenzenes.

[0063] The sandwich-structured catalyst provided by this invention, when used for the selective hydrodeoxygenation reaction of halonitrobenzenes, achieves a high conversion rate of o-chloronitrobenzene (o-CNB) of up to 99% and a selectivity of o-chloroaniline (o-CAN) of up to 96.7% under H2 conditions at 80°C and 1 MPa, with a turnover frequency (TOF) of up to 11049 h⁻¹. -1 In addition, the catalyst has good stability, and its conversion rate and selectivity remain basically unchanged after 10 cycles of use.

[0064] Compared with the prior art, the present invention has the following beneficial effects:

[0065] (1) The sandwich structure catalyst provided by the present invention uses Zr-MOF as the core and Zr-MOF(M) as the outer shell, with noble metal nanoparticles as the interlayer and the nanoparticles are evenly distributed in the interlayer. It can not only control the size and spatial distribution of noble metal nanoparticles in the composite structure catalyst, but also achieve a synergistic effect between the M metal in the M-TCPP ligand and the noble metal nanoparticles, so that the catalyst has better catalytic activity, selectivity and stability.

[0066] (2) When the sandwich-structured catalyst provided by this invention is used to catalyze the selective hydrogenation reaction of halonitrobenzenes, it can simultaneously achieve high conversion rate, excellent selectivity, high turnover rate and good stability, with a conversion rate as high as 99%, a selectivity as high as 96% or more, and a TOF value as high as 10000 h⁻¹. -1 above;

[0067] (3) The preparation method provided by the present invention coats a layer of noble metal nanoparticles onto Zr-MOF material, and then coats it with Zr-MOF(M) material on its outermost layer. The type and thickness of the shell can be adjusted by changing the type and amount of ligands added. The preparation method is easy to operate, the equipment is simple, the efficiency is high, and the catalyst structure can be precisely controlled. Attached Figure Description

[0068] Figure 1 TEM image of PCN-221@Pt@PCN-221(Co) prepared in Example 1;

[0069] Figure 2 This is a magnified TEM image of PCN-221@Pt@PCN-221(Co) prepared in Example 1;

[0070] Figure 3 This is a statistical chart of the outer shell layer thickness of PCN-221@Pt@PCN-221(Co) prepared in Example 1;

[0071] Figure 4TEM image of Pt nanoparticles in PCN-221@Pt@PCN-221(Co) prepared in Example 1;

[0072] Figure 5 The XRD pattern of PCN-221@Pt@PCN-221(Co) prepared in Example 1;

[0073] Figure 6 The image shows a SEM image of PCN-221 obtained in Example 1.

[0074] Figure 7 The graph shows the conversion and selectivity results of PCN-221@Pt@PCN-221(Co) catalyzing the selective hydrogenation of o-chloronitrobenzene in 10 cycles, prepared in Example 1.

[0075] Figure 8 The image shows a TEM image of PCN-221@Pt@PCN-221(Co) prepared in Example 1 after 10 cycles of selective hydrogenation of o-chloronitrobenzene. Detailed Implementation

[0076] 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.

[0077] Example 1

[0078] This embodiment provides a sandwich structure catalyst constructed from a noble metal and a metal-organic framework and its preparation method. The sandwich structure catalyst consists of a core, an interlayer, and an outer shell layer from the inside out.

[0079] The general formula of the sandwich structure catalyst is PCN-221@Pt@PCN-221(Co);

[0080] The core is PCN-221 constructed based on Zr and H2TCPP with a molar ratio of 1:0.2, and the outer shell is PCN-221(Co) constructed based on Zr and Co-TCPP with a molar ratio of 1:0.19.

[0081] Based on the total mass of the sandwich-structured catalyst, the mass content of noble metal nanoparticles is 0.5 wt%.

[0082] The diameter of the PCN-221 core is 590 nm; the pore size of the PCN-221(Co) in the outer shell is...

[0083] The preparation method of the sandwich structure catalyst includes the following steps:

[0084] (1) Disperse 50 mg PCN-221 in 5 mL DMF, add 3.5 mL of Pt nanoparticle ethanol solution with an average particle size of 2.8 nm dropwise, stir at 25 °C for 2 h, collect the solid by centrifugation and wash several times with DMF to obtain PCN-221@Pt;

[0085] The specific preparation method of PCN-221 is as follows: 50 mg of zirconium dichloride octahydrate and 0.750 g of benzoic acid are dispersed in 10 mL of DMF and heated at 80 °C for 1 h. After cooling to room temperature, 25 mg of H2TCPP is added to the solution and sonicated for 5 min. Then, the solution is placed in an oven and subjected to a first solvothermal reaction at 120 °C for 5 h. After cooling to room temperature, the solid is collected by centrifugation and washed several times with DMF and acetone. Finally, the obtained PCN-221 is dried at 80 °C.

[0086] (2) 50 mg zirconium dichloride octahydrate, 0.750 g benzoic acid and 25 mg Co-TCPP were ultrasonically dispersed in 10 mL DMF to obtain a precursor solution;

[0087] (3) Mix 3.5 mL of PCN-221@Pt DMF solution and 3.5 mL of precursor solution, and react with the second solvothermal reaction at 120 °C for 1 h. Collect the solid by centrifugation and wash it several times with DMF and acetone. Finally, dry the obtained PCN-221@Pt@PCN-221(Co) at 80 °C.

[0088] The catalyst obtained in this example was tested using a field emission transmission electron microscope (Tecnai G2 F20 U-TWIN), and the results are as follows: Figure 1-4 As shown. By Figure 1-3 It can be seen that the Pt nanoparticles are uniformly distributed in the interlayer, and the thickness of the PCN-221(Co) outer shell is approximately 15 nm. Figure 4 It can be seen that the Pt nanoparticles in the obtained catalyst have a uniform size distribution and an average size of 2.8 nm.

[0089] The catalyst obtained in this example was characterized using an X-ray diffractometer (Rigaku D / MAX-TTRIII), and the results are as follows: Figure 5 As shown. By Figure 5 It can be seen that the epitaxially grown PCN-221@Pt@PCN-221(Co) has a good crystal structure.

[0090] The prepared PCN-221 was characterized using an ultra-high resolution cold field emission scanning electron microscope (Hitachi-8220), and the results are as follows: Figure 6 As shown. By Figure 6 It can be seen that the prepared PCN-221 particles have a uniform size distribution with an average size of 590 nm.

[0091] Example 2

[0092] This embodiment provides a sandwich-structured catalyst constructed from a noble metal and a metal-organic framework, and its preparation method. The preparation method of the sandwich-structured catalyst includes the following steps:

[0093] (1) Disperse 50 mg PCN-221 in 5 mL DMF, add 3.5 mL of Pt nanoparticle ethanol solution with an average particle size of 2.5 nm dropwise, stir at 20 °C for 3 h, collect the solid by centrifugation and wash several times with DMF to obtain PCN-221@Pt;

[0094] The preparation method of PCN-221 is the same as that of PCN-221 in Example 1;

[0095] (2) 50 mg zirconium dichloride octahydrate, 0.750 g benzoic acid and 25 mg Co-TCPP were ultrasonically dispersed in 10 mL DMF to obtain a precursor solution;

[0096] (3) Mix 3.5 mL of PCN-221@Pt DMF solution and 2 mL of precursor solution, and react with the second solvothermal reaction at 110 °C for 1 h. Collect the solid by centrifugation and wash it several times with DMF and acetone in sequence. Finally, dry the obtained PCN-221@Pt@PCN-221(Co) at 80 °C.

[0097] All other conditions are the same as in Example 1.

[0098] Example 3

[0099] This embodiment provides a sandwich structure catalyst constructed from noble metal and metal-organic framework and its preparation method. Except for the thickness of the outer shell layer being 5 nm, i.e. shortening the time of the second solvothermal reaction in step (3), all other conditions are the same as in Example 1.

[0100] Example 4

[0101] This embodiment provides a sandwich structure catalyst constructed from noble metal and metal-organic framework and its preparation method. Except for the thickness of the outer shell layer being 30 nm, i.e. extending the time of the second solvothermal reaction in step (3), all other conditions are the same as in Example 1.

[0102] Example 5

[0103] This embodiment provides a sandwich structure catalyst constructed from a noble metal and a metal-organic framework and its preparation method. Except for the thickness of the outer shell layer being 40 nm, i.e. extending the time of the second solvothermal reaction in step (3), all other conditions are the same as in Example 1.

[0104] Example 6

[0105] This embodiment provides a sandwich structure catalyst constructed from a noble metal and a metal-organic framework and its preparation method. Except that the general formula of the sandwich structure catalyst is UiO-66(Zr)@Pt@PCN-221(Co), all other conditions are the same as in Example 1.

[0106] Example 7

[0107] This embodiment provides a sandwich structure catalyst constructed from a noble metal and a metal-organic framework and its preparation method. Except that the general formula of the sandwich structure catalyst is PCN-221@Pt@PCN-221(Fe), i.e. Fe-TCPP is used as the ligand in step (2), all other conditions are the same as in Example 1.

[0108] Example 8

[0109] This embodiment provides a sandwich structure catalyst constructed from a noble metal and a metal-organic framework and its preparation method. Except that the general formula of the sandwich structure catalyst is PCN-221@Pt@PCN-221(Ni), i.e., Ni-TCPP is used as the ligand in step (2), all other conditions are the same as in Example 1.

[0110] Comparative Example 1

[0111] This comparative example provides a composite catalyst constructed from noble metals and metal-organic frameworks and its preparation method. Except that the catalyst has the general formula PCN-221, i.e. it is not coated with noble metal nanoparticles and a shell layer, all other conditions are the same as in Example 1.

[0112] Comparative Example 2

[0113] This comparative example provides a composite catalyst constructed from a noble metal and a metal-organic framework and its preparation method. Except that the catalyst has the general formula PCN-221@Pt, i.e., it is not coated with an outer shell, all other conditions are the same as in Example 1.

[0114] Comparative Example 3

[0115] This comparative example provides a sandwich-structured catalyst constructed from a noble metal and a metal-organic framework and its preparation method. Except for the general formula of the catalyst being PCN-221@Pt@PCN-221, all other conditions are the same as in Example 1.

[0116] The catalysts obtained in the above examples and comparative examples were used for the selective hydrodeoxygenation reaction of o-chloronitrobenzene, with a reaction time of 21 min in each case. The catalytic test results are shown in Table 1. The specific test method was as follows: The catalyst prepared above (containing 0.05 mg of the active component Pt) was dispersed in 5 mL of methanol. 1 mmol of o-chloronitrobenzene was added to the solution, and the mixture was then transferred to a 50 mL polytetrafluoroethylene-lined stainless steel reactor. Hydrogen gas was introduced and purged five times to remove air from the reactor, with a final hydrogen pressure of 1 MPa. The reactor was then placed in an 80°C oil bath and magnetically stirred at 600 rad / min until the desired reaction time was reached (the effect of mass transfer inside and outside the reactor on catalytic performance was not considered under these reaction conditions and stirring speed). After the reaction, the catalyst was separated by centrifugation, and the resulting reaction solution was filtered through a 0.22 μm filter membrane and analyzed using a gas chromatograph (Shimadzu GC-2014C).

[0117] Table 1

[0118] Example 1 99 96.7 11049 Example 2 >99 96.3 11161 Example 3 >99 93 11161 Example 4 54 96 6027 Example 5 40 96.5 4464 Example 6 / / / Example 7 98 95 10938 Example 8 93 90 10379 Comparative Example 1 / / / Comparative Example 2 67 83 7478 Comparative Example 3 50 91 5580

[0119] The TOF value is calculated by dividing the number of moles of the conversion substrate by the number of moles of the noble metal nanoparticles and the reaction time; " / " indicates no catalytic activity.

[0120] As shown in Table 1:

[0121] (1) The sandwich structure catalyst and its preparation method constructed by noble metal and metal-organic framework provided by the present invention are used to catalyze the selective hydrogenation reaction of o-chloronitrobenzene to prepare o-chloroaniline, and can simultaneously achieve high conversion rate, high selectivity and high conversion frequency.

[0122] (2) Comparing Examples 1 and 3-5, it can be seen that when the outer shell layer in the catalyst is too thin, the outer shell layer is less uniform and there is a problem of incomplete coating of noble metal nanoparticles, which leads to a decrease in the selectivity of the catalyst; when the outer shell layer in the catalyst is too thick, it will lead to an increase in mass transfer resistance and a decrease in catalyst performance and efficiency.

[0123] (3) Comparison of Example 1 and Example 6 shows that when UiO-66(Zr) is selected as the core carrier, PCN-221(Co) cannot grow on the carrier UiO-66(Zr) due to the lattice mismatch between the two MOFs.

[0124] (3) A comparison of Example 1 and Comparative Example 1 shows that when the catalyst does not contain noble metal nanoparticles, PCN-221 does not have catalytic activity;

[0125] (4) Comparison of Example 1 and Comparative Example 2 shows that when the catalyst does not contain the outermost PCN-221(Co) shell, on the one hand, Pt nanoparticles are easy to fall off and aggregate during the reaction, resulting in a decrease in catalyst activity; on the other hand, due to the inability to synergistically catalyze, the selectivity of the catalyst decreases.

[0126] (5) Comparison of Example 1 and Comparative Example 3 shows that when H2TCPP is selected as the organic ligand for the outermost shell, the selectivity and activity of the catalyst decrease because it cannot synergistically catalyze with the noble metal nanoparticles.

[0127] The catalyst obtained in Example 1 was used to catalyze the selective hydrogenation and deoxygenation reaction of other halonitrobenzenes. The catalytic method was consistent with that used for catalyzing o-chloronitrobenzenes. The catalytic test results are shown in Table 2.

[0128] Table 2

[0129] p-Chloronitrobenzene 21 99 99 11049 m-chloronitrobenzene 23 99 99 10088 o-fluoronitrobenzene 25 99 99 9281 o-bromonitrobenzene 35 98 97 6563

[0130] As shown in Table 2, the catalyst provided by this invention is applicable to the selective hydrogenation of various halogen-substituted halonitrobenzenes, and has a wide range of applications.

[0131] The catalyst obtained in Example 1 was subjected to a cycle stability test. The catalytic conditions were consistent with the first catalytic reaction of o-chloronitrobenzene. The test results are as follows: Figure 7 As shown. By Figure 7 It can be seen that after 10 consecutive cycles, the substrate conversion rate remains above 98%, and the product selectivity remains above 96%. The catalyst after 10 cycles was characterized by TEM, and the results are as follows: Figure 8 As shown. By Figure 8 As can be seen, the catalyst morphology remains intact. This indicates that the catalyst provided by this invention has excellent stability.

[0132] 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 sandwich-structured catalyst constructed from a noble metal and a metal-organic framework, characterized in that, The sandwich-structured catalyst consists of a core, interlayer, and outer shell layer from the inside out. The core comprises a Zr-MOF material, wherein the first organic ligand of the Zr-MOF material comprises tetrakis(4-carboxyphenyl)porphyrin; The interlayer includes a layer of noble metal nanoparticles; the noble metal nanoparticles in the interlayer include Pt nanoparticles or Pd nanoparticles. The outer shell is a MOF material constructed based on a second organic ligand and a Zr central metal, wherein the second organic ligand includes any one of tetra(4-carboxyphenyl)cobalt porphyrin, tetra(4-carboxyphenyl)iron porphyrin, or tetra(4-carboxyphenyl)nickel porphyrin; The sandwich-structured catalyst is used to catalyze the selective hydrogenation and deoxygenation reaction of halonitrobenzenes.

2. The sandwich-structured catalyst according to claim 1, characterized in that, The second organic ligand is tetra(4-carboxyphenyl)cobalt porphyrin or tetra(4-carboxyphenyl)iron porphyrin.

3. The sandwich-structured catalyst according to claim 1, characterized in that, In the Zr-MOF material, the molar ratio of the Zr central metal to the first organic ligand is 1:(0.1-2).

4. The sandwich-structured catalyst according to claim 1, characterized in that, The molar ratio of the Zr central metal to the second organic ligand is 1:(0.1-1).

5. The sandwich-structured catalyst according to claim 1, characterized in that, Based on the total mass of the sandwich-structured catalyst, the mass content of noble metal nanoparticles is 0.2wt%-1wt%.

6. The sandwich-structured catalyst according to claim 1, characterized in that, The diameter of the core is 400-600nm.

7. The sandwich-structured catalyst according to claim 1, characterized in that, The average particle size of the noble metal nanoparticles in the interlayer is 2-5 nm.

8. The sandwich-structured catalyst according to claim 1, characterized in that, The thickness of the outer shell layer is 10-30 nm.

9. The sandwich-structured catalyst according to claim 8, characterized in that, The thickness of the outer shell layer is 10-20 nm.

10. A method for preparing a sandwich-structured catalyst as described in any one of claims 1-9, characterized in that, The preparation method includes the following steps: (1) Disperse Zr-MOF in a solvent, add a solution of noble metal nanoparticles to it, and stir to obtain Zr-MOF@noble metal nanoparticles; (2) Mix the zirconium source, the second organic ligand, the regulator and the solvent to obtain the precursor solution; (3) Mix the Zr-MOF@noble metal nanoparticle solution from step (1) with the precursor solution from step (2) and carry out a second solvothermal reaction to obtain the sandwich structure catalyst.

11. The preparation method according to claim 10, characterized in that, The preparation method of Zr-MOF in step (1) includes: A zirconium source, modifier, and solvent are mixed, heated, cooled, and then a first organic ligand is added to carry out a first solvothermal reaction to obtain Zr-MOF.

12. The preparation method according to claim 11, characterized in that, The zirconium source includes zirconium oxychloride and / or zirconium tetrachloride.

13. The preparation method according to claim 11, characterized in that, The regulator includes benzoic acid.

14. The preparation method according to claim 11, characterized in that, The solvent includes N,N-dimethylformamide.

15. The preparation method according to claim 11, characterized in that, The molar ratio of the zirconium source to the regulator is 1:(30-50).

16. The preparation method according to claim 11, characterized in that, The solid-liquid ratio of the zirconium source to the solvent is (3-8):1 mg / mL.

17. The preparation method according to claim 11, characterized in that, The heating temperature is 75-85℃.

18. The preparation method according to claim 11, characterized in that, The heating time is 0.5-2 hours.

19. The preparation method according to claim 11, characterized in that, The temperature of the first solvothermal reaction is 110-130℃.

20. The preparation method according to claim 11, characterized in that, The first solvothermal reaction takes 4-6 hours.

21. The preparation method according to claim 10, characterized in that, The noble metal nanoparticle solution in step (1) includes noble metal nanoparticles and an alcohol solvent.

22. The preparation method according to claim 10, characterized in that, The stirring temperature in step (1) is 20-35℃.

23. The preparation method according to claim 10, characterized in that, The stirring time in step (1) is 1-3 hours.

24. The preparation method according to claim 10, characterized in that, The solvents used in steps (1) and (2) are both N,N-dimethylformamide.

25. The preparation method according to claim 10, characterized in that, The zirconium source in step (2) includes zirconium oxychloride and / or zirconium tetrachloride.

26. The preparation method according to claim 10, characterized in that, The regulator includes benzoic acid.

27. The preparation method according to claim 10, characterized in that, The molar ratio of zirconium source to regulator in step (2) is 1:(30-50).

28. The preparation method according to claim 10, characterized in that, In step (2), the solid-liquid ratio of the zirconium source to the solvent is (3-8):1 mg / mL.

29. The preparation method according to claim 10, characterized in that, The volume ratio of the Zr-MOF@noble metal nanoparticle solution to the precursor solution in step (3) is 1:(0.5-2).

30. The preparation method according to claim 10, characterized in that, In step (3), the temperature of the second solvothermal reaction is 110-130℃.

31. The preparation method according to claim 10, characterized in that, In step (3), the second solvothermal reaction takes 1-1.5 hours.

32. The application of a sandwich-structured catalyst as described in any one of claims 1-9, characterized in that, The sandwich-structured catalyst is used to catalyze the selective hydrogenation and deoxygenation reaction of halonitrobenzenes.

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