Targeted liquid-phase iron-based catalyst as well as preparation method and application thereof

Abstract

The invention discloses a targeted liquid-phase iron-based catalyst as well as a preparation method and application thereof. The preparation method of the targeted liquid-phase iron-based catalyst comprises the following steps: pre-assembling template molecules and functional monomers in a pore-foaming agent according to a specific ratio, then adding an iron source, a cross-linking agent and an initiator for cross-linking polymerization, and finally calcining and activating to obtain the targeted liquid-phase iron-based catalyst. Wherein the molar ratio of the template molecule to the functional monomer is 1: (4-8), the molar ratio of the iron source to the template molecule is (1-3): 1, the molar ratio of the cross-linking agent to the functional monomer is (3-6): 1, and the use amount of the initiator is 0.5-2% of the mass of the functional monomer. The prepared catalyst has high targeting performance on target reactants, selectivity and efficiency of catalytic reaction can be remarkably improved, the preparation process is environmentally friendly, cost is low, and the catalyst has wide application prospects in the fields of fine chemical engineering, environmental governance, biological medicine and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of catalyst preparation, and in particular relates to a targeted liquid-phase iron-based catalyst and a preparation method and application thereof. Background Art

[0002] In many fields such as modern chemical engineering, environmental science and biomedicine, efficient and specific catalytic reactions are crucial. In the field of fine chemical synthesis, with the growing demand for high value-added chemicals, the selectivity and yield of reactions have become core concerns. Traditional non-targeted catalysts are difficult to act accurately on specific functional groups when catalyzing reactions of multi-functional compounds, resulting in a large number of side reactions, which not only reduces the yield of the target product, but also increases the cost and difficulty of product separation and purification. For example, in the synthesis process of complex drug intermediates, the use of ordinary catalysts will generate a variety of isomers, and the subsequent separation process is complicated and costly, which seriously limits production efficiency and economic benefits.

[0003] There is also an urgent need for targeted catalysts in the field of environmental governance. Organic pollutants in water and soil are of various types and complex in structure. Traditional catalysts lack selectivity in degrading these pollutants and cannot efficiently remove specific harmful pollutants. Taking persistent organic pollutants (POPs) as an example, their chemical properties are stable and it is difficult for conventional catalysts to completely decompose them, resulting in the long-term failure to effectively solve environmental pollution problems. In addition, some traditional catalysts may also produce secondary pollution during use, further increasing the environmental burden.

[0004] In the field of biomedicine, the highly specific characteristics of enzyme-catalyzed reactions provide a reference for the development of catalysts. The drug synthesis process requires precise control of the reaction site to ensure the purity and activity of the drug; in disease treatment, such as photodynamic therapy for tumors, it is expected that the catalyst can specifically play a role in tumor tissue, efficiently produce reactive oxygen species, accurately kill tumor cells, and minimize damage to normal tissues. However, existing catalysts are difficult to meet this requirement, which limits the development of related treatment technologies.

[0005] At present, the traditional methods for preparing targeted liquid-phase iron-based catalysts have many drawbacks. Although the physical mixing method is simple to operate, the active components have poor dispersion on the carrier and cannot form a stable targeting structure, resulting in low targeting and catalytic activity of the catalyst. The catalyst prepared by the impregnation method has weak interaction between the active components and the carrier, which is easy to lose during the reaction, affecting the service life and stability of the catalyst. Moreover, these traditional methods are difficult to accurately control the microstructure of the catalyst and the distribution of active sites, and cannot meet the growing demand for highly active and highly selective catalysts.

[0006] Patent Publication No. CN116925376A discloses a targeted IuP / DingS-1217 catalyst. It mixes itaconic acid, ferric chloride, and ultrapure water evenly, and prepares DingS-1217 through hydrothermal reaction. Subsequently, DingS-1217, template molecules, functional monomers, and porogens are pre-polymerized, and the polymer is then cross-linked to obtain the targeted IuP / DingS-1217 catalyst. The preparation of the above catalyst has the following problems: (1) It is necessary to first prepare it into a MOF material and then carry out pre-polymerization and cross-linking, which requires a complex MOF preparation process, increasing time, equipment, and labor costs; (2) Preparing it into a MOF material may change the active state of the iron source, hinder the contact between reactants and active sites, resulting in damage to the targeting and catalytic activity of the final catalyst and affecting the catalytic efficiency; (3) First preparing it into a MOF material interferes with the intermolecular interactions in subsequent reactions, making it difficult to precisely control the microstructure and active site distribution of the catalyst and unable to meet the requirements for highly active and highly selective catalysts.

[0007] With the continuous progress of technology, higher requirements are put forward for the performance of targeted liquid-phase iron-based catalysts in various fields. Driven by the concept of green chemistry, it is necessary to develop more environmentally friendly and efficient preparation methods to reduce energy consumption and waste emissions during the preparation process. At the same time, with the in-depth study of the relationship between microstructure and catalytic performance, it is expected to achieve precise control of the microstructure of the catalyst to further improve its targeting and catalytic activity. Therefore, it is urgent to develop an innovative preparation method for targeted liquid-phase iron-based catalysts, which has important practical significance for promoting the development of related fields. Summary of the Invention

[0008] Aiming at the technical problems of poor targeting, low catalytic efficiency, and insufficient stability existing in current liquid-phase iron-based catalysts, the primary objective of the present invention is to provide a preparation method for a targeted liquid-phase iron-based catalyst, and the obtained targeted liquid-phase iron-based catalyst has high targeting, high catalytic activity, and good stability.

[0009] The second objective of the present invention lies in providing a targeted liquid-phase iron-based catalyst obtained by a preparation method for a targeted liquid-phase iron-based catalyst.

[0010] The third objective of the present invention is to provide the use of a targeted liquid-phase iron-based catalyst in the fields of fine chemical synthesis, environmental pollutant degradation, and biomedical catalysis.

[0011] To achieve the above objectives, the present invention is realized through the following technical solutions:

[0012] The present invention claims a preparation method for a targeted liquid-phase iron-based catalyst, including the following steps:

[0013] S1. Mix the template molecule, functional monomer, and porogen, and stir for pre-assembly;

[0014] S2. Add the iron source, crosslinking agent, and initiator to the system obtained in step S1, mix evenly, and then carry out a crosslinking polymerization reaction to obtain a polymer;

[0015] S3. Calcinate the polymer described in step S2 to obtain a targeted liquid-phase iron-based catalyst;

[0016] In the said step S1, the molar ratio of the template molecule to the functional monomer is 1:(4 - 8);

[0017] In the said step S2, the molar ratio of the iron source to the template molecule is (1 - 3):1; the molar ratio of the crosslinking agent to the functional monomer is (3 - 6):1; the dosage of the initiator is 0.5 - 2% of the mass of the functional monomer;

[0018] In the said step S3, the temperature of the calcination treatment is 300 - 500 °C, and the time is 2 - 4 h;

[0019] The said functional monomer contains a group that coordinates with the iron source and a group that can react with the crosslinking agent; the said template molecule is the target reactant or its structural analogue.

[0020] In the present invention, the target reactant or its structural analogue is selected as the template molecule, and the functional monomer is a compound containing a group that can coordinate with the iron source and a group that can react with the crosslinking agent. The template molecule and the functional monomer form a stable complex through hydrogen bonds, ionic bonds, or π-π interactions, etc. The template molecule, as a "mold", determines the targeted recognition site of the subsequently formed catalyst for the target reactant. The interaction mode and degree between the functional monomer and the template molecule directly affect the targeted performance of the catalyst, and the porogen provides a suitable environment for the pre-assembly process and forms a porous structure subsequently, which is beneficial to the diffusion of reactants.

[0021] Further, then add the iron source, crosslinking agent, and initiator to the system of step S1 to form a polymer containing the template molecule, iron source, functional monomer, and crosslinking agent. In this step, the iron source is the key component of catalytic activity; the crosslinking agent constructs the three-dimensional network structure of the polymer and enhances the stability of the catalyst; the initiator initiates the polymerization reaction, and the reaction temperature and time have important effects on the structure and properties of the polymer.

[0022] Further, the polymer in step S2 is washed to remove the template molecules therein. After removing the template molecules, it is calcined at a specific temperature to convert the iron source into catalytically active iron oxide or elemental iron, and at the same time, the structure of the molecularly imprinted polymer is further stabilized, and finally a targeted liquid-phase iron-based catalyst is prepared. The complete removal of the template molecules is the key to forming specific recognition sites. The calcination process not only activates the iron source, but also optimizes the polymer structure and improves the comprehensive performance of the catalyst.

[0023] In the present invention, the unique molecular imprinting technology process, from the pre-assembly of the template molecules and functional monomers, to the cross-linking polymerization to form a stable structure, and then to the template removal and catalyst activation, each step is closely coordinated. The template molecules precisely guide the arrangement of the functional monomers to form recognition sites complementary to the target reactants; the network structure constructed by the cross-linking agent ensures the stability of the catalyst during the reaction; the iron source is converted into an active component by calcination and acts synergistically with the recognition sites. At the same time, the porous structure formed by the porogen is conducive to the full contact between the reactants and the catalyst, improving the catalytic efficiency.

[0024] Further, the inventors have found through research that strictly controlling the parameters of each step, such as the ratio of the template molecules to the functional monomers, the dosage of the iron source, the addition amounts of the cross-linking agent and the initiator, and the calcination parameters, etc., is closely related to the targeting, catalysis, and stability of the final catalyst.

[0025] (1) An inappropriate ratio of the template molecules to the functional monomers will affect the formation quality of the recognition sites (too low a ratio (such as 1:2) results in insufficient density of the recognition sites, and too high a ratio (such as 1:10) causes steric hindrance effects); an inappropriate dosage of the iron source will lead to insufficient catalytic activity or a decrease in the stability of the catalyst.

[0026] (2) Inaccurate dosages of the cross-linking agent and the initiator will affect the polymer structure and thus affect the catalyst performance.

[0027] (3) When the molar ratio of the iron source to the template molecules is outside the above range, the coordination saturation of the iron ions with the functional monomers decreases, resulting in a decrease in the density of the active sites by more than 30%.

[0028] (4) If the calcination parameters are unreasonable, the iron source cannot be effectively activated and the polymer structure cannot be stabilized, which will cause a large increase in the Fe-O bonds and make it difficult to promote the formation of Fe-O-C covalent bonds.

[0029] For the non-linear cooperative optimization of the above key parameters, the prepared targeted liquid-phase iron-based catalyst has a catalytic efficiency for the target reactant that is more than 70% higher than that of the traditional liquid-phase iron-based catalyst, and has a high degree of targeting. In a complex reaction system, this catalyst can accurately identify the target reactant and efficiently catalyze the target reactant, reducing the occurrence of side reactions and greatly improving the selectivity and efficiency of the catalytic reaction. In addition, the raw materials used in the preparation process are relatively common, and some can be recycled, reducing the production cost. At the same time, the use of toxic and harmful reagents is reduced, which conforms to the concept of green chemistry.

[0030] Preferably, the molar ratio of the template molecule to the functional monomer is 1:(4.5 - 8); more preferably, the molar ratio is 1:(5 - 7); most preferably, the molar ratio is 1:6. More specifically, the molar ratio of the template molecule to the functional monomer can be 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, etc., or the range formed by any of the above values, such as 1:(5 - 8), 1:(6 - 8), etc., and the present invention is not limited thereto.

[0031] Preferably, the molar ratio of the iron source to the template molecule is (1.5 - 2.5):1; more preferably, the molar ratio of the iron source to the template molecule is (1.8 - 2.2):1; most preferably, the molar ratio of the iron source to the template molecule is 2:1. More specifically, the molar ratio of the iron source to the template molecule can be 1.5:1, 2:1, 2.5:1, etc., and the present invention is not limited thereto.

[0032] Preferably, the molar ratio of the cross-linking agent to the functional monomer is (4 - 5):1; most preferably, the molar ratio is 5:1. More specifically, the molar ratio of the cross-linking agent to the functional monomer can be 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, etc., or the range formed by any of the above values, such as (3.5 - 6):1, (4 - 6):1, etc., and the present invention is not limited thereto.

[0033] Preferably, the dosage of the initiator is 0.6 - 1.5% of the mass of the functional monomer; more preferably, the dosage of the initiator is 0.8 - 1.2% of the mass of the functional monomer; most preferably, the dosage of the initiator is 1% of the mass of the functional monomer. More specifically, the dosage of the initiator is 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, etc. of the mass of the functional monomer, or the range formed by any of the above values, and the present invention is not limited thereto.

[0034] Preferably, the template molecule is one or more of p-nitrophenol, p-chlorophenol, p-aminobenzoic acid, 2,4-dichlorophenoxyacetic acid.

[0035] Preferably, the functional monomer is selected from one or more of vinylpyridine and methacrylic acid.

[0036] Preferably, the pore former is an inert organic solvent. More preferably, the pore former includes, but is not limited to, inert organic solvents such as toluene and dodecanol.

[0037] Preferably, the iron source is selected from one or more of iron nitrate, iron chloride, and iron sulfate. More preferably, the iron source is iron nitrate.

[0038] Preferably, the crosslinking agent is a crosslinking agent conventionally used in the art. More specifically, the crosslinking agent is selected from one or two of ethylene glycol dimethacrylate and divinylbenzene. Preferably, the crosslinking agent is ethylene glycol dimethacrylate.

[0039] Preferably, the initiator is an initiator conventionally used in the art. More specifically, the initiator is an azo radical initiator, including but not limited to azobisisobutyronitrile, etc.

[0040] Preferably, in step S2, the temperature of the polymerization reaction is 40 - 60 °C, and the time of the polymerization reaction is 12 - 24 hours.

[0041] Preferably, in step S3, an ultrasonic-assisted extraction method is used to remove the template molecules in the polymer and the targeted liquid-phase iron-based catalyst.

[0042] Preferably, the ultrasonic-assisted extraction method includes a first-stage treatment and a second-stage treatment; the first-stage treatment: the polymer is ultrasonically cleaned in an ethanol / acetic acid mixed solution; the second-stage treatment: the obtained targeted liquid-phase iron-based catalyst is subjected to gradient elution with a methanol solution and a mixed solution of methanol and acetic acid, and ultrasonic cleaning is carried out simultaneously during the gradient elution process to remove the template molecules.

[0043] Specifically, in some embodiments, the specific operation of step S3 is as follows:

[0044] First stage: The polymer is ultrasonically cleaned in an ethanol / acetic acid mixed solution;

[0045] Subsequently, a calcination treatment is carried out;

[0046] Second stage: The targeted liquid-phase iron-based catalyst obtained after the calcination treatment is subjected to gradient elution with a methanol solution and a mixed solution of methanol and acetic acid, and ultrasonic cleaning is carried out simultaneously during the gradient elution process to finally remove the template molecules in the targeted liquid-phase iron-based catalyst.

[0047] In the solution of this application, when the ultrasonic-assisted extraction method is not thoroughly eluted, the targeted liquid-phase iron-based catalyst will retain template molecules, interfering with the targeted recognition of the catalyst.

[0048] Preferably, the volume ratio of ethanol to acetic acid is (8 - 12):1. More preferably, the volume ratio of ethanol to acetic acid is 10:1.

[0049] Preferably, the ultrasonic cleaning time in the ethanol / acetic acid mixed solution is ≥8 h; more preferably, the time is 8 - 12 h. Preferably, the mixed solution is replaced every 1 - 3 h during ultrasonic cleaning in the ethanol / acetic acid mixed solution.

[0050] Preferably, after ultrasonic cleaning in the ethanol / acetic acid mixed solution, it is successively washed with deionized water and ethanol solution multiple times.

[0051] Preferably, in the second stage, gradient elution is carried out successively as follows: gradient elution is carried out with a 45 - 55% methanol aqueous solution, a 75 - 85% methanol aqueous solution, a 100% methanol solution, and a mixed solution of 3 - 10% acetic acid. More preferably, the elution time for each solution is 3 - 5 h.

[0052] Preferably, after gradient elution, pure methanol solution is used for elution until neutral.

[0053] Preferably, in step S3, the temperature is raised to 300 - 500 °C at a heating rate of 2 - 5 °C / min.

[0054] More preferably, the temperature of the calcination treatment is 400 °C, the heating rate is 3 °C / min, and the calcination time is 3 h.

[0055] Preferably, in steps S2 and S3, the reaction is carried out under a protective gas. More specifically, the protective gas can be an inert gas (such as nitrogen, argon, etc.).

[0056] Furthermore, the present invention claims the targeted liquid-phase iron-based catalyst prepared by the preparation method of the targeted liquid-phase iron-based catalyst.

[0057] Furthermore, the present invention claims the use of the targeted liquid-phase iron-based catalyst in the fields of fine chemical synthesis, environmental pollutant degradation, and biomedical catalysis.

[0058] In fine chemical synthesis, it can be used for highly selective synthesis of compounds with specific structures, improving product quality and production efficiency; in environmental pollutant degradation, it can accurately catalyze the degradation of specific organic pollutants, purifying water bodies and soil; in the field of biomedical catalysis, it helps to achieve precise catalysis in drug synthesis and play a targeted catalytic role in disease treatment, reducing damage to normal tissues.

[0059] Compared with the prior art, the present invention has the following beneficial effects:

[0060] (1) Traditional MOF-based catalysts need to synthesize the MOF framework by hydrothermal method and then load active components, which have problems such as cumbersome steps and limited thermal stability. The present invention prepares a targeted liquid-phase iron-based catalyst through an integrated process of "template molecule pre-assembly - iron salt copolymerization - calcination activation". The preparation method provided by the present invention simplifies the operation process, eliminates the need for a complex MOF preparation process, avoids the problem of precise control of MOF preparation conditions, and reduces time, equipment and labor costs. At the same time, it also avoids expensive reagents required for the preparation of MOF materials and effectively reduces the overall production cost.

[0061] (2) The targeted liquid-phase iron-based catalyst prepared by the present invention has excellent structural stability at high temperatures (TGA shows that the 5% weight loss temperature ≥ 380 °C), solving the problem of incompatibility of the thermodynamic window between MOF-based catalysts (pyrolysis temperature ≤ 300 °C) and iron salt calcination (requiring 400 - 500 °C), and solving the technical problem of unstable structure of existing MOF-based catalysts at high temperatures.

[0062] (3) Develop an ultrasonic-assisted ethanol extraction - staged calcination synergistic process to remove template molecules and reduce the residue of template molecules. The first stage is ultrasonic-assisted ethanol / acetic acid extraction, which destroys the interaction between the template and the carrier through cavitation. The second stage is gradient elution after calcination to achieve a template residue amount < 0.05 ppm, and the comprehensive efficiency is increased by nearly 200% compared with the traditional solvent washing method.

[0063] (4) The targeted liquid-phase iron-based catalyst prepared by the present invention has excellent targeting, stability and environmental friendliness; Targeting: The degradation rate of p-nitrophenol is up to 95% (2 h), showing a significant improvement compared with the degradation rate of MOF-based catalysts; Stability: The degradation rate remains above 70% after 5 consecutive cycles; Environmental friendliness: There is no emission of toxic solvents throughout the process, and the utilization rate of Fe source reaches 92%, meeting the requirements of green chemistry. Specific embodiments

[0064] The following further illustrates the present invention in conjunction with the specification and specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the technical field.

[0065] Example 1

[0066] (1) Template molecule and functional monomer pre-assembly: Using 1 mol of p-nitrophenol as the template molecule, 4-vinylpyridine is selected as the functional monomer, and they are dissolved in 650 mL of toluene according to the molar ratio of template molecule to functional monomer of 1:6, and stirred at room temperature for 3 hours to form a pre-assembled complex.

[0067] (2) Introduction of iron source and crosslinking polymerization: Iron nitrate was added to the above-mentioned pre-assembled complex, and the molar ratio of iron nitrate to p-nitrophenol was 2:1. After stirring evenly, ethylene glycol dimethacrylate was added as a crosslinking agent, and the molar ratio of the crosslinking agent to 4-vinylpyridine was 4:1. Then, 7.38 g of azobisisobutyronitrile, which accounted for 1% of the mass of 4-vinylpyridine, was added. After purging with nitrogen to remove oxygen for 12 minutes, it was sealed in a mold, and a thermal-initiated polymerization reaction was carried out at 50 °C for 18 hours to obtain a polymer.

[0068] (3) Removal of template molecules and activation of catalyst

[0069] The first stage: Ultrasonic-assisted extraction before calcination

[0070] The polymer obtained in step (2) was soaked in an ethanol / acetic acid mixed solution with a volume ratio of 8:1, and ultrasonic treatment was carried out at room temperature for 8 hours (ultrasonic parameters: frequency 20 kHz, power density 100 W / cm 2 ), and the new mixed solution was replaced every 2 hours during this period. After the extraction was completed, centrifugation was carried out to separate, the solid residue was collected, washed 3 times with deionized water, then washed 2 times with ethanol, and dried in vacuum to constant weight.

[0071] The second stage: Gradient elution after calcination

[0072] The dried polymer was placed in a tube furnace, heated to 400 °C at a rate of 3 °C / min under nitrogen protection, and calcined for 3 hours. After cooling, it was immersed in a gradient eluent (50% (volume fraction, the same as the following methanol aqueous solution) methanol aqueous solution, 80% methanol aqueous solution, 100% methanol + 5% acetic acid) in turn. Each eluent was soaked for 4 hours and ultrasonic-assisted at the same time (parameters as above). Finally, it was eluted with pure methanol until the pH of the effluent was neutral to prepare a targeted liquid-phase iron-based catalyst. The residual amount of template molecules in the effluent was detected by HPLC (detection wavelength 275 nm, quantitative analysis by external standard method), and the final residual amount was 0.02 ppm.

[0073] Example 2

[0074] The difference between this example and Example 1 is that in step (1), the molar ratio of the template molecule to the functional monomer is 1:4.

[0075] Example 3

[0076] The difference between this example and Example 1 is that in step (1), the molar ratio of the template molecule to the functional monomer is 1:8.

[0077] Example 4

[0078] The difference between this example and Example 1 is that in step (2), the molar ratio of the iron source to the template molecule is 1:1.

[0079] Example 5

[0080] The difference between this example and Example 1 lies in that: in step (2), the molar ratio of the iron source to the template molecule is 3:1.

[0081] Example 6

[0082] The difference between this example and Example 1 lies in that: in step (2), the molar ratio of the crosslinking agent to the functional monomer is 3:1.

[0083] Example 7

[0084] The difference between this example and Example 1 lies in that: in step (2), the molar ratio of the crosslinking agent to the functional monomer is 5:1.

[0085] Example 8

[0086] The difference between this example and Example 1 lies in that: in step (2), the molar ratio of the crosslinking agent to the functional monomer is 6:1.

[0087] Example 9

[0088] The difference between this example and Example 1 lies in that: in step (2), the dosage of the initiator is 0.5% of the mass of the functional monomer.

[0089] Example 10

[0090] The difference between this example and Example 1 lies in that: in step (2), the dosage of the initiator is 2% of the mass of the functional monomer.

[0091] Comparative Example 1

[0092] The difference between this comparative example and Example 1 lies in that: in step (1), no template molecule is added, and other dosages remain unchanged.

[0093] Comparative Example 2

[0094] The difference between this comparative example and Example 1 lies in that:

[0095] The integrated process of template molecule pre-assembly - iron salt copolymerization - calcination activation is not adopted, and without going through the pre-assembly and polymerization processes, the iron source, functional monomer, template molecule, pore-forming agent, crosslinking agent, and initiator are directly physically mixed evenly. The specific steps are as follows:

[0096] (1) Physical mixing: Mix ferric nitrate as the iron source, 4-vinylpyridine as the functional monomer, p-nitrophenol as the template molecule, toluene as the pore-forming agent, ethylene glycol dimethacrylate as the crosslinking agent, and azobisisobutyronitrile as the initiator in the ratio of Example 1, and stir at room temperature for 1 hour.

[0097] (2) Calcination and cleaning: Transfer the mixture to a tubular furnace, heat it to 400 °C at a rate of 3 °C / min under nitrogen protection and calcine for 3 hours; after calcination, elute and remove the template molecules according to the ultrasonic-assisted method in Example 1.

[0098] Comparative Example 3

[0099] The difference between this comparative example and Example 1 is that: in step (3), no calcination treatment is carried out.

[0100] Comparative Example 4

[0101] The difference between this comparative example and Example 1 is that: ordinary silica gel is used as the carrier to load the iron source, and the specific implementation process is as follows:

[0102] (1) Pretreatment of ordinary silica gel: Select ordinary silica gel with a pore size of 200 - 300 nm and a specific surface area of 800 m 2 / g, activate it at 150 °C for 4 hours, then wash it with deionized water until neutral, and dry it at 105 °C for standby.

[0103] (2) Loading of iron source: Immerse the activated silica gel into a ferric nitrate (Fe(NO3)3·9H2O) solution with a concentration of 10 mol / L, ultrasonically disperse for 30 minutes, and then stir at 60 °C for 6 hours to promote the full adsorption of iron ions on the surface of silica gel.

[0104] (3) Drying and calcination: Filter out the silica gel, dry it at 110 °C to constant weight, then place it in a tubular furnace and calcine it under nitrogen protection. First, keep it at 300 °C for 2 hours, and then heat it to 500 °C and keep it for 3 hours to remove organic substances and unreacted iron salts.

[0105] Comparative Example 5

[0106] The difference between this comparative example and Example 1 is that: in step (3), the first-stage ultrasonic-assisted extraction is shortened to 5 hours.

[0107] Comparative Example 6

[0108] The difference between this comparative example and Example 1 is that: in step (1), the molar ratio of the template molecule to the functional monomer is 1:2.

[0109] Comparative Example 7

[0110] The difference between this comparative example and Example 1 is that: in step (1), the molar ratio of the template molecule to the functional monomer is 1:10.

[0111] Comparative Example 8

[0112] The difference between this comparative example and Example 1 is that: in step (2), the dosage of the initiator is 0.1% of the mass of the functional monomer.

[0113] Comparative Example 9

[0114] The difference between this comparative example and Example 1 lies in that: in step (2), the dosage of the initiator is 3% of the mass of the functional monomer.

[0115] Comparative Example 10

[0116] The difference between this comparative example and Example 1 lies in that: in step (2), the iron source is not added, and the iron source in step (2) is directly added in step (1) and mixed with the template molecule and the functional monomer, while other steps and conditions remain unchanged.

[0117] Comparative Example 11

[0118] This comparative example prepares a traditional MOF-based catalyst, and its preparation method refers to the hydrothermal method in 《A review on metal-organic frameworks: Synthesis and applications》. The specific operation is as follows:

[0119] First, prepare the template molecule (p-nitrophenol), the functional monomer (4-vinylpyridine), the iron source (iron nitrate), the pore-forming agent (N,N-dimethylformamide), the initiator (azobisisobutyronitrile), and the DMF / water mixed solvent. The cross-linking agent is usually omitted in the traditional method.

[0120] Dissolve 0.1 mmol of p-nitrophenol, 0.8 mmol of 4-vinylpyridine, N,N-dimethylformamide, and azobisisobutyronitrile (the dosages of N,N-dimethylformamide and azobisisobutyronitrile are the same as those in Example 1) in 20 mL of the DMF / aqueous solution, and stir at room temperature for 3 hours to form a homogeneous solution. Then add 0.2 mmol of iron nitrate, stir until completely dissolved, deoxygenate by passing nitrogen for 15 minutes, and then transfer the reaction solution to a 50 mL high-pressure reaction kettle. After sealing, react in an oven at 180 °C for 24 hours. After the reaction, naturally cool to room temperature, centrifuge to separate the solid product, wash it 3 times with DMF, ethanol, and deionized water in sequence, and dry it in vacuo at 60 °C for 12 hours. Finally, directly heat the dried MOF to 400 °C in a muffle furnace and calcine it at a rate of 5 °C / min for 2 hours for activation to prepare the traditional MOF-based catalyst.

[0121] Test Example 1 Catalytic Degradation of p-Nitrophenol by the Catalyst and Cycling Stability Experiment

[0122] The catalysts prepared in the examples and comparative examples were used for the catalytic degradation reaction of p-nitrophenol in simulated wastewater. The reaction was carried out in a 250 mL three-necked flask. The volume of the simulated wastewater was 100 mL, the initial concentration of p-nitrophenol was 100 mg / L, the dosage of the catalyst was 0.1 g, the reaction temperature was 30 °C, and the reaction was carried out for 60 minutes under magnetic stirring. After the reaction, the remaining concentration of p-nitrophenol was determined by high performance liquid chromatography, and the degradation rate was calculated.

[0123] Experimental preparation: The catalysts prepared in the examples and comparative examples were selected as the test objects. Prepare a plurality of 250 mL three-necked flasks, simulated wastewater (the initial concentration of p-nitrophenol was 100 mg / L, the volume was 100 mL), experimental equipment and instruments such as a magnetic stirrer and a high performance liquid chromatograph.

[0124] The first round of degradation reaction: Add 0.1 g of the above catalyst to the three-necked flask, place the flask on the magnetic stirrer, keep the reaction temperature at 30 °C, and stir the reaction for 60 minutes. After the reaction, the remaining concentration of p-nitrophenol was determined by high performance liquid chromatography. The degradation rate was calculated according to the formula "degradation rate = (initial concentration - remaining concentration) ÷ initial concentration × 100%", and the data was recorded. The degradation rates of the catalysts prepared in each example and comparative example are shown in Table 1 below.

[0125] Catalyst recovery and treatment: After the reaction, the catalyst was separated by centrifugation or filtration, washed repeatedly with deionized water to remove the residual reactants and impurities on the surface, and then dried in an oven at 60 °C for 2 hours to restore it to the initial state, and prepared for the next round of experiments.

[0126] Multiple rounds of cyclic experiments: Repeat the above steps to carry out at least 5 rounds of cyclic experiments, and record the degradation rate of p-nitrophenol. The degradation rates after one cycle and five cycles are shown in Table 2.

[0127] Table 1

[0128]

[0129]

[0130] Table 2

[0131] Degradation rate after one cycle (%) Degradation rate after five cycles (%) Example 1 90 75 Example 2 70 48 Example 3 80 62 Example 4 70 38 Example 5 80 55 Example 6 75 51 Example 7 95 82 Example 8 75 49 Example 9 70 32 Example 10 88 61 Comparative Example 1 40 28 Comparative Example 2 35 18 Comparative Example 3 50 30 Comparative Example 4 40 22 Comparative Example 5 60 35 Comparative Example 6 45 25 Comparative Example 7 60 28 Comparative Example 8 40 15 Comparative Example 9 65 41 Comparative Example 10 55 27

[0132] As can be seen from Table 1 above, the targeted liquid-phase iron-based catalyst prepared by the present invention has excellent catalytic degradation efficiency for p-nitrophenol in simulated wastewater, and the catalytic degradation rate ≥ 70%; further preferably, the catalytic degradation rate ≥ 80%; the catalytic degradation rate ≥ 85%; the catalytic degradation rate ≥ 90%.

[0133] As can be seen from Table 2 above, the targeted liquid-phase iron-based catalyst prepared by the present invention still has a good catalytic degradation rate and excellent cyclic stability after being used multiple times. More specifically, after being cycled five times, the catalytic degradation rate of the targeted liquid-phase iron-based catalyst is ≥32%; further preferably, after being cycled five times, the catalytic degradation rate is ≥48%; further preferably, after being cycled five times, the catalytic degradation rate is ≥61%; further preferably, after being cycled five times, the highest catalytic degradation rate can reach 75%.

[0134] As can be seen from Example 1 and Comparative Example 1, when a template molecule is added during the preparation process, the catalytic degradation rate of the targeted liquid-phase iron-based catalyst can be greatly improved, and it has excellent cyclic stability. This is because the template molecule can form a stable complex with the functional monomer through hydrogen bonds, ionic bonds or π-π interactions, etc., which directly affects the targeting performance of the catalyst and can improve the target recognition of the catalyst for the target reactant.

[0135] As can be seen from Example 1, Comparative Example 2 and Comparative Example 4, it is difficult to achieve the technical effects of the present invention by directly physically mixing and calcining the reactants evenly or loading the iron source with ordinary silica gel. Only the targeted liquid-phase iron-based catalyst prepared by the integrated process of the present invention can achieve excellent catalytic degradation effects.

[0136] As can be seen from Example 1 and Comparative Example 3, after the calcination treatment, the iron source can be effectively activated and the polymer structure can be stabilized, promoting the formation of Fe-O-C covalent bonds, thereby improving the catalytic degradation efficiency of the catalyst.

[0137] As can be seen from Example 1, Comparative Example 5, Comparative Example 6, Comparative Example 7, Comparative Example 8 and Comparative Example 9, the ratio of the template molecule to the functional monomer, the dosage of the iron source, the addition amounts of the cross-linking agent and the initiator, etc. are closely related to the targeting, catalysis and stability of the finally prepared catalyst.

[0138] As can be seen from Example 1 and Comparative Example 10, when the iron source is directly added in step (1), the catalytic effect of the prepared catalyst is significantly reduced. The inventor speculates that the template molecule may preferentially undergo non-specific adsorption with the iron source rather than forming an ordered complex with the functional monomer. This will lead to a disordered distribution of the iron source and the inability to construct target recognition sites and a stable three-dimensional network through the synergistic effect of pre-assembly-polymerization, ultimately reducing the density of active sites and significantly decreasing the catalytic efficiency.

[0139] Test Example 2 High-temperature Structural Stability Test Experiment of the Catalyst

[0140] High-temperature structural stability test: To evaluate the high-temperature structural stability of the catalyst of Example 1, the catalyst of Comparative Example 4, and the traditional MOF-based catalyst of Comparative Example 11, thermogravimetric analysis (TGA) was used for testing. The TA Instruments Q500 thermogravimetric analyzer was selected for the instrument. The sample amount was about 5 mg. Under nitrogen protection (flow rate 50 mL / min), the temperature was raised from room temperature to 800 °C at a heating rate of 10 °C / min. The test results are shown in Table 3 below.

[0141] Table 3

[0142] Catalyst 5% weight loss temperature (°C) Temperature at maximum weight loss rate (°C) Example 1 385 450 Comparative Example 4 280 350 Comparative Example 11 ≤300 320

[0143] The test results show that the catalyst provided by the present invention has excellent thermal stability in a nitrogen environment. The 5% weight loss temperature (T5%) reaches 385 °C, far exceeding that of the traditional liquid-phase iron-based catalyst of Comparative Example 11. The catalyst provided by the present invention only has a slight weight loss of about 5% between 300 - 500 °C, indicating that the iron source has been successfully converted into a stable structure and has not decomposed significantly.

[0144] From the catalysts of Comparative Example 4 and Comparative Example 11 in Table 3 above, it can be seen that the 5% weight loss temperature of the catalyst in Comparative Example 4 is only 280 °C (much lower than 385 °C of Example 1), and the 5% weight loss temperature of the traditional MOF-based catalyst prepared in Comparative Example 11 is ≤ 300 °C, indicating that these catalysts have decomposed rapidly at lower temperatures and have poor high-temperature stability.

[0145] The foregoing examples are merely illustrative and are used to explain some features of the method described in the present invention. The appended claims are intended to claim the broadest scope possible, and the examples presented herein are supported by the applicant's actual test results. Therefore, the applicant's intention is that the appended claims not be limited by the selection of examples that illustrate the features of the present invention. Some of the numerical ranges used in the claims also include sub-ranges within them, and variations within these ranges should also be interpreted as being covered by the appended claims whenever possible.

Claims

1. A method for preparing a targeted liquid-phase iron-based catalyst, characterized in that, It includes the following steps: S1. Mix the template molecule, functional monomer and porogen, and stir for pre-assembly; S2. Add an iron source, a cross-linking agent and an initiator to the system obtained in step S1, mix evenly, and then carry out a cross-linking polymerization reaction to obtain a polymer; S3. Calcinate the polymer described in step S2 to obtain a targeted liquid-phase iron-based catalyst; In the said step S1, the molar ratio of the template molecule to the functional monomer is 1:(4 - 8); In the said step S2, the molar ratio of the iron source to the template molecule is (1 - 3):1; the molar ratio of the cross-linking agent to the functional monomer is (3 - 6):1; the dosage of the initiator is 0.5 - 2% of the mass of the functional monomer; In the said step S3, the temperature of the calcination treatment is 300 - 500 °C, and the time is 2 - 4 h; The said functional monomer contains a group coordinated with the iron source and a group capable of reacting with the cross-linking agent; the said template molecule is the target reactant or its structural analogue.

2. The preparation method according to claim 1, characterized in that, The said template molecule is one or more of p-nitrophenol, p-chlorophenol, p-aminobenzoic acid, 2,4-dichlorophenoxyacetic acid.

3. The preparation method according to claim 1, wherein The said functional monomer is selected from one or more of vinylpyridine and methacrylic acid.

4. The preparation method according to claim 1, wherein, The said porogen is an inert organic solvent.

5. The preparation method according to claim 1, wherein The said iron source is selected from one or more of iron nitrate, iron chloride and iron sulfate.

6. The preparation method according to claim 1, wherein In the said step S2, the temperature of the polymerization reaction is 40 - 60 °C, and the time of the polymerization reaction is 12 - 24 hours.

7. According to the preparation method described in claim 1, characterized in that, In the said step S3, an ultrasonic-assisted extraction method is used to remove the template molecule in the polymer and the targeted liquid-phase iron-based catalyst.

8. The preparation method according to claim 7, wherein, The said ultrasonic-assisted extraction method includes a first-stage treatment and a second-stage treatment; the first-stage treatment: ultrasonically clean the polymer in an ethanol / acetic acid mixed solution; the second-stage treatment: the obtained targeted liquid-phase iron-based catalyst is subjected to gradient elution with a methanol solution and a mixed solution of methanol and acetic acid, and ultrasonic cleaning is carried out simultaneously during the gradient elution process to remove the template molecule.

9. A targeted liquid-phase iron-based catalyst prepared by the preparation method according to any one of claims 1 - 8.

10. Use of the targeted liquid-phase iron-based catalyst according to claim 9 in the fields of fine chemical synthesis, environmental pollutant degradation and biopharmaceutical catalysis.

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