Low-cost MOF framework homogeneous particle preparation method based on molecular sieve

Abstract

The invention discloses a low-cost MOF framework homogeneous particle preparation method based on a molecular sieve, and relates to the technical field of porous materials. The catalyst is prepared from the following components in parts by mass: 100 parts of an industrial molecular sieve, 5-20 parts of a base metal ion source, 1-5 parts of a functional modifier and 3-8 parts of composite microspheres, the composite microsphere is prepared from 80 to 90 parts of mesoporous silicon and 10 to 20 parts of chitosan; the industrial grade molecular sieve provides a natural coordination site, and a base metal ion source and the coordination site are subjected to a coordination reaction to construct the MOF-like skeleton. Through the synergistic effect of the industrial molecular sieve and the base metal ion source, the technical problem that the cost is high due to the fact that a traditional MOF material depends on a high-valence organic ligand and precious metal is solved, the industrial molecular sieve provides natural coordination sites to replace the high-valence organic ligand and the base metal ion source, and the cost of metal raw materials is reduced; on the premise that basic performance of the MOF-like framework is not sacrificed, breakthrough reduction of material cost is achieved, and large-scale mass production feasibility is achieved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of porous materials, in particular to a low-cost MOF framework homogeneous particle preparation method based on molecular sieves. BACKGROUND

[0002] MOF porous materials are a kind of key basic materials with high specific surface area, controllable pore structure and excellent adsorption and catalytic performance, and play an important role in the fields of adsorption separation, catalytic reaction, sewage treatment and the like, and are widely applied to industrial wastewater heavy metal removal, flue gas CO2 capture, fine chemical catalysis, drinking water purification and the like. The MOF porous materials can efficiently remove pollutants and selectively separate target substances due to the unique structural advantages, become an important support for solving environmental governance and chemical production efficiency improvement and the like, and have extremely high practical value and development potential in industrial scale application and people's livelihood fields.

[0003] In the process of implementing the technical scheme of the application embodiment, the application finds that the above-mentioned technology at least has the following technical problems: first, the cost is high due to the dependence on high-priced organic ligands and noble metal ion sources, and it is difficult to be applied on a large scale; second, the particles are easy to agglomerate and are not uniformly dispersed, which leads to insufficient exposure of active sites and affects the use effect; third, the structural stability and recycling performance are poor, the function is single, and it is difficult to adapt to practical scenes with strict requirements on cost, performance and stability. Therefore, the present application provides a low-cost MOF framework homogeneous particle preparation method based on molecular sieves to solve the above problems. SUMMARY

[0004] Technical problems solved In view of the deficiencies in the prior art, the application provides a low-cost MOF framework homogeneous particle preparation method based on molecular sieves, which solves the problems proposed in the background art.

[0005] Technical scheme To achieve the above object, the application is implemented by the following technical scheme: a low-cost MOF framework homogeneous particle based on molecular sieves, which is composed of the following components by mass fraction: 100 parts of industrial-grade molecular sieve, 5-20 parts of base metal ion source, 1-5 parts of functional modifier and 3-8 parts of composite microspheres.

[0006] The industrial-grade molecular sieve at least includes one of ZSM-5, MCM-41, SBA-15 and Y-type molecular sieve, the particle size is controlled to be 100-500 nanometers, and the SiO2 / Al2O3 molar ratio is controlled to be 20-100.

[0007] ZSM-5, MCM-41, SBA-15, Y zeolite are selected because they are mature materials for industrial scale production, low cost and structure characteristics meet the needs. ZSM-5 and Y zeolite microporous framework can provide dense hydroxyl coordination sites, MCM-41 and SBA-15 mesoporous channels can assist mass transfer, meet the needs of multi-level pore construction of MOF-like framework. The particle size is controlled in 100-500 nanometers, in order to balance the specific surface area and mass transfer efficiency, avoid agglomeration caused by too small particle size, or reduce the reaction uniformity caused by too large particle size. The SiO2 / Al2O3 molar ratio is controlled in 20-100, which can ensure the structural stability of the zeolite framework, improve the acid and alkali corrosion resistance of the material, and also retain enough aluminum sites to enhance the coordination and combination ability with metal ions.

[0008] The core role of industrial-grade zeolite is to provide natural coordination sites, and the silicon hydroxyl and aluminum hydroxyl on its surface can directly participate in the reaction without additional treatment. When combined with other materials, the surface hydroxyl of the zeolite can form interaction with the amino group of chitosan in the composite microspheres, effectively inhibiting particle agglomeration; at the same time, its microporous structure and the mesoporous of the composite microspheres form connected channels, improving the diffusion efficiency of metal ions and modifiers, and ensuring uniform coordination reaction and modification process.

[0009] Such selection and parameter setting enable industrial-grade zeolite to replace high-priced organic ligands, greatly reducing raw material costs, while the uniform distribution of natural coordination sites allows the particle size deviation of MOF-like framework to be controlled within a reasonable range, and the structural uniformity is significantly better than that of traditional MOF materials, and the multi-level pore structure also improves the adsorption capacity of pollutants of different sizes.

[0010] The base metal ion source at least includes one of the soluble salts containing Zn 2 ⁺, Cu 2 ⁺, Fe 3 ⁺, Ni 2 ⁺, which at least includes one of zinc nitrate, copper chloride, iron sulfate, and nickel chloride, and the concentration is controlled in 0.1-0.5 moles per liter.

[0011] Zn 2 ⁺, Cu 2 ⁺, Fe 3 ⁺, Ni 2⁺, because they are abundant in the earth's crust, the cost is much lower than the high-priced metals commonly used in traditional MOFs, and they are low in toxicity and environmentally friendly. The radius of these ions is moderate, which can form stable coordination bonds with the hydroxyl groups on the surface of the molecular sieve, ensuring the structural stability of the MOF-like framework. The choice of soluble salts such as zinc nitrate, copper chloride, iron sulfate, and nickel chloride is because they have high solubility in alcohol-water mixed systems, complete dissociation, and can be uniformly dispersed in the reaction system, ensuring that the coordination reaction proceeds completely, and their anions can be easily removed by washing without leaving impurities in the material that affect performance. The concentration is controlled at 0.1-0.5 moles per liter to avoid excessive local coordination caused by high metal ion concentration, which can cause agglomeration, or low concentration, which can cause incomplete coordination and affect the formation of the MOF-like framework.

[0012] The core role of the base metal ion source is to act as a coordination center and coordinate with the hydroxyl groups on the surface of the molecular sieve, gradually building a three-dimensional MOF-like framework structure, and giving the material porosity and adsorption and catalytic active sites. When combined with other materials, the metal ions form a co-doped system with Ce 3 ⁺, La 3 ⁺, etc., enhancing the electronic conductivity of the framework through electron interaction; at the same time, the metal ions form weak coordination with the amino groups of chitosan in the composite microspheres, further strengthening the combination of the microspheres and the molecular sieve, and improving the overall structural stability.

[0013] This selection brings multiple advantages, the raw material cost is only about one-tenth of that of traditional MOF metal sources, and there is no risk of heavy metal pollution; the coordination reaction can be carried out under mild conditions without the need for high temperature and pressure, greatly reducing energy consumption; the co-doping effect also enhances the selective adsorption and catalytic conversion capacity of the material for target substances, significantly improving the CO2 selective separation coefficient of the material.

[0014] The functional modifier at least includes one of Ce 3 ⁺ salt, La 3 ⁺ salt, N-containing compound, S-containing compound, and short-chain alkylating agent; wherein the doping modifier at least includes one of cerium nitrate, lanthanum nitrate, urea, and thiourea, and the amount is controlled at 1-3 parts; the surface grafting modifier at least includes one of chloromethane, bromoethane, and chloropropane, and the amount is controlled at 0.5-2 parts.

[0015] The choice of Ce 3 ⁺ salt, La 3 ⁺ salt, N-containing compound, S-containing compound, and short-chain alkylating agent as a functional modifier is because they can optimize the performance of the material through different modification paths. Ce 3 ⁺ salt, La 3The + salt belongs to a rare earth salt, and the 4f orbit of the ion can provide a rich electron active site to enhance the redox catalytic ability of the material; the nitrogen and sulfur heteroatoms in the N-containing compound and the S-containing compound have lone pair electrons, which can adjust the electron cloud density of the MOF-like framework and improve the chelation and adsorption effect of heavy metal ions; the short-chain alkylating agent can introduce a hydrophobic group to improve the adsorption selectivity of the material for nonpolar molecules.

[0016] The doping type modifier is selected from cerium nitrate, lanthanum nitrate, urea, and thiourea, and the amount is controlled to be 1-3 parts, so as to ensure uniform doping, avoid excessive amount leading to channel blockage and affecting mass transfer efficiency, and prevent insufficient amount from failing to form effective active sites. The surface grafting type modifier is selected from chloromethane, bromoethane, and chloropropane, because the molecular volume is small and can be successfully grafted to the hydroxyl group on the surface of the molecular sieve through substitution reaction. The amount is controlled to be 0.5-2 parts, so as to balance the grafting rate and channel retention, avoid excessive grafting to cover the active sites, or insufficient grafting to fail to effectively adjust the surface properties.

[0017] The functional modifier plays a role through two paths of doping and surface grafting. The doping type modifier is embedded in the framework to improve the catalytic activity and adsorption site density; the surface grafting type modifier modifies the surface of the framework to adjust the hydrophilicity and hydrophobicity and the interface compatibility. When cooperating with other materials, the doping type modifier is embedded in the molecular sieve framework synchronously with metal ions, does not damage the coordination bond between the metal ions and the hydroxyl group, but rather increases the charge density of the framework through synergistic effect; the alkyl chain of the surface grafting type modifier can form interaction with the hydroxyl group of the chitosan in the composite microspheres, enhances the interface bonding force between the microspheres and the MOF-like framework, and reduces the shedding of the microspheres.

[0018] The synergistic effect of the two types of modifiers makes the material have both catalytic activity and heavy metal chelation ability, and can adapt to the adsorption scene of nonpolar pollutants, and at the same time, cooperates with other components to improve the structural stability of the material, so that the material maintains good performance in a wide pH range, and the application range is significantly expanded.

[0019] The composite microspheres comprise 80-90 parts of mesoporous silica and 10-20 parts of chitosan; in the composite microspheres, the mesoporous silica at least comprises one of MCM-48 and SBA-15, the particle size of the microspheres is controlled to be 50-100 nanometers, and the mesopore size is controlled to be 2-5 nanometers; the composite microspheres are prepared by reacting the mesoporous silica and the chitosan in 1-3 wt% acetic acid aqueous solution, stirring at 300-500 revolutions per minute during the reaction to make the mesoporous silica and the chitosan uniformly contact, controlling the reaction temperature to be 30-50°C, and controlling the reaction time to be 2-4 hours.

[0020] In the composite microspheres, mesoporous silica accounts for 80-90 parts, and chitosan accounts for 10-20 parts. Such a proportion is matched to fully exert the synergistic advantages of the two components. Mesoporous silica provides additional mass transfer channels for the material due to its high specific surface area and regular mesoporous structure, and its surface hydroxyl groups can interact with the surface groups of molecular sieves to enhance the overall structural stability. Chitosan is rich in amino and hydroxyl groups, has good hydrophilicity and biocompatibility, and its amino groups can form weak coordination with metal ions to assist in improving the dispersion effect.

[0021] MCM-48 and SBA-15 are selected as the type of mesoporous silica because they are mature mesoporous materials in industry, have high specific surface area and ordered mesoporous structure, and can provide sufficient mass transfer space for the material. The particle size of the microspheres is controlled in the range of 50-100 nanometers to ensure that the microspheres can be uniformly dispersed in the system and form a good match with the molecular sieve particles, avoiding agglomeration caused by too large particle size or increasing the difficulty of preparation caused by too small particle size. The mesoporous pore size is controlled in the range of 2-5 nanometers to form a hierarchical pore structure with the microporous MOF-like framework, accelerate the diffusion of substances, and adapt to the adsorption needs of different size pollutant molecules.

[0022] The preparation conditions of the composite microspheres are precisely set. 1-3wt% acetic acid aqueous solution is used as the reaction medium, which can moderately dissolve chitosan, make its molecular chain fully stretch out, and facilitate the combination with mesoporous silica, without damaging the structure of mesoporous silica. The reaction temperature is controlled in the range of 30-50°C to ensure that the reaction proceeds smoothly and the reaction rate is accelerated, and to avoid excessive temperature leading to chitosan degradation or mesoporous silica structure collapse. The reaction time is controlled in the range of 2-4 hours to ensure that mesoporous silica and chitosan fully react and combine to form stable composite microspheres, and to avoid insufficient combination caused by too short reaction time or increased energy consumption and cost caused by too long reaction time.

[0023] When the composite microspheres are combined with other components, the pore structure of mesoporous silica assists mass transfer, and the amino groups of chitosan enhance dispersion effect, effectively inhibiting particle agglomeration and ensuring uniform distribution of each component. At the same time, the structural characteristics of the composite microspheres themselves form a synergistic effect with molecular sieves, metal ion sources, and modifiers to provide reliable support for the formation of multifunctional composite particles and improve the adsorption, catalytic performance, and structural stability of the material.

[0024] Industrial-grade molecular sieves provide basic reaction sites for the entire reaction by virtue of their natural coordination sites such as hydroxyl groups on the surface. Coordination reactions occur between the coordination sites and the metal ion source, gradually building a MOF-like skeleton and giving the material porous properties and basic activity. The doped components in the functional modifier are embedded in the skeleton during the coordination reaction, increasing the active site density and improving the catalytic and adsorptive capacity of the material; the surface grafting component modifies the surface of the skeleton, flexibly adjusts the hydrophilic or hydrophobic properties of the material, and expands the application scenarios of the material. The composite microspheres form a synergistic effect with the molecular sieves in this process, the pore structure of mesoporous silica assists mass transfer, and the amino groups of chitosan enhance dispersion, effectively inhibiting particle agglomeration and ensuring uniform distribution of each component.

[0025] Each component cooperates and synergizes with each other, industrial-grade molecular sieves provide a structural basis, metal ion sources build the skeleton main body, functional modifiers optimize performance, and composite microspheres ensure uniform dispersion, together forming multifunctional composite particles with high adsorption performance, catalytic activity, and structural stability, solving the problems of high cost and poor structural uniformity of traditional MOF materials, expanding the application range of the material, and being suitable for multiple scenarios such as wastewater treatment and gas separation.

[0026] A low-cost MOF-like skeleton homogeneous particle preparation method based on molecular sieves, as shown in Figure 1 , includes the following steps: Step one, place industrial-grade molecular sieves and composite microspheres in an alcohol-water mixed system, ultrasonically disperse to obtain a uniform dispersion liquid, the volume ratio of the alcohol-water mixed system is controlled at 1:1 to 3:1, and the alcohol at least includes one of ethanol, propanol, and isopropanol; the ultrasonic power is controlled at 100-300 W, and the ultrasonic time is controlled at 20-60 minutes.

[0027] The alcohol-water mixed system is selected at a volume ratio of 1:1 to 3:1 because alcohols such as ethanol, propanol, and isopropanol can reduce the surface tension of the system, promote the wet dispersion of industrial-grade molecular sieves and composite microspheres, and the appropriate amount of water can maintain the polarity of the system to avoid the precipitation of chitosan in the composite microspheres due to excessive alcohol content. Ethanol, propanol, and isopropanol are selected because their boiling points are moderate, their volatility is controllable, they are easy to remove by drying, and they do not react with other components in the system.

[0028] The ultrasonic power is controlled at 100-300 W to generate sufficient mechanical vibration to break the initial agglomeration of the molecular sieves and the composite microspheres, and to avoid excessive power that can damage the structure of the particles; the ultrasonic time is controlled at 20-60 minutes to ensure sufficient dispersion and avoid uneven dispersion of the particles due to insufficient time, or to avoid increasing energy consumption and possibly causing secondary agglomeration of the particles due to excessive time.

[0029] The whole step is cooperated by the polarity adjustment of alcohol water system and the mechanical dispersion of ultrasonic, so that the hydroxyl on the surface of industrial molecular sieve and the amino of chitosan in the composite microspheres are fully contacted and interacted, which lays a foundation for the uniform performance of subsequent coordination reaction, and finally a uniform dispersion liquid with uniform particle distribution and no obvious agglomeration is obtained.

[0030] In step two, a base metal ion source is added to the dispersion liquid, the dropping rate is controlled to carry out coordination reaction, and a functional modifier is added at the same time to complete synchronous modification, so that a coordination modified intermediate is obtained. The dropping rate of the base metal ion source is controlled at 0.5-2 ml / min, the coordination reaction temperature is controlled at 25-40℃, the reaction time is controlled at 1-3 hours, and the stirring rate is controlled at 300-500 rpm.

[0031] The dropping rate of the base metal ion source is controlled at 0.5-2 ml / min to avoid the local concentration of metal ions being too high, which leads to the rapid combination with the coordination sites of molecular sieve to form agglomerates, and to ensure that the ions are uniformly dispersed in the system and gradually coordinated with the coordination sites on the surface of molecular sieve. The coordination reaction temperature is controlled at 25-40℃, which not only ensures that the coordination reaction has a suitable reaction rate, but also avoids the degradation of chitosan in the composite microspheres and the failure of the functional modifier due to too high temperature, or the slow reaction progress and incomplete coordination due to too low temperature.

[0032] The reaction time is controlled at 1-3 hours to ensure that the metal ions are fully coordinated with the coordination sites of molecular sieve, and at the same time the functional modifier is doped or surface grafted synchronously, so as to avoid insufficient reaction due to too short time or waste of energy and excessive crosslinking of product structure due to too long time. The stirring rate is controlled at 300-500 rpm, which not only promotes the uniform diffusion of metal ions and modifier in the dispersion liquid and accelerates the synchronous performance of coordination and modification reaction, but also avoids the destruction of the preliminary coordination structure formed due to too high stirring intensity.

[0033] Through the coordinated regulation of dropping rate, temperature, time and stirring rate, the simultaneous completion of metal ion coordination to construct MOF-like skeleton and the optimization of the performance of functional modifier is realized, which ensures that the structure of the coordination modified intermediate is uniform and the active sites are uniformly distributed, and provides a good foundation for subsequent solidification and molding.

[0034] In step three, the coordination modified intermediate is solidified and post-treated to obtain a low-cost MOF-like skeleton homogeneous particle based on molecular sieve. The solidification temperature is controlled at 50-80℃, and the solidification time is controlled at 2-6 hours. The post-treatment includes centrifugation, washing and vacuum drying. The centrifugation speed is controlled at 8000-12000 rpm, the vacuum drying temperature is controlled at 60-80℃, and the drying time is controlled at 8-12 hours.

[0035] The solidification temperature is controlled at 50-80 DEG C, which can slowly lock the coordination formed MOF-like skeleton structure, enhance the skeleton stability, avoid the mesoporous structure collapse of the composite microspheres, thermal decomposition of chitosan caused by too high temperature, or insufficient solidification caused by too low temperature, and the skeleton is easy to deform. The solidification time is controlled at 2-6 hours, which ensures the complete stability of the skeleton structure, makes the functional modifier firmly combined with the skeleton, avoids the loose structure caused by too short time, or the increased energy consumption caused by too long time.

[0036] In the post-processing, the centrifugal speed is controlled at 8000-12000 rpm, which can efficiently separate the coordination modification intermediate particles, remove the unreacted free metal ions, excess modifier and other impurities in the system, and avoid the particle structure damage caused by too high speed. The washing step can further remove the impurities adsorbed on the surface of the particles, and ensure the product purity. The vacuum drying temperature is controlled at 60-80 DEG C, which can quickly remove the water and residual alcohol on the surface and inside of the particles, and avoid the damage of the porous structure and active sites of the MOF-like skeleton caused by too high temperature; the drying time is controlled at 8-12 hours, which ensures the complete removal of water, prevents the residual water from affecting the storage stability and use performance of the product.

[0037] The step finally obtains the MOF-like skeleton homogeneous particles with stable structure, high purity and performance up to standard through the precise control of solidification parameters and the cooperation of each link in the post-processing, and ensures that the product has high adsorption performance, catalytic activity and structural uniformity.

[0038] Advantages The present application has the following advantages: (1) The low-cost MOF-like skeleton homogeneous particle preparation method based on molecular sieve solves the technical problem of high cost caused by the dependence of traditional MOF materials on high-priced organic ligand and noble metal, the industrial-grade molecular sieve provides natural coordination sites to replace high-priced organic ligand, and the base metal ion source reduces the cost of metal raw materials, so that the material cost is reduced on the premise of not sacrificing the basic performance of MOF-like skeleton, and the material has the feasibility of large-scale production.

[0039] (2) The low-cost MOF-like skeleton homogeneous particle preparation method based on molecular sieve solves the technical problem of easy agglomeration, uneven dispersion and single performance of traditional MOF particles by the cooperation of composite microspheres and functional modifier, the composite microspheres ensure the uniform dispersion of industrial-grade molecular sieve, base metal ion source and modifier in the system, the functional modifier is targeted to optimize the adsorption selectivity and catalytic activity, and finally realizes the cooperation of high dispersion, high adsorption capacity and excellent catalytic activity of the material.

[0040] Of course, any product implementing the present application does not necessarily need to achieve all the advantages described above. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 A flow chart of a preparation method of a low-cost MOF-type skeleton homogeneous particle based on molecular sieve according to the present application. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0043] Embodiment 1 The present embodiment 1 provides a low-cost MOF-type skeleton homogeneous particle based on molecular sieve, which comprises the following components by mass fraction: 100 parts of industrial-grade molecular sieve, type ZSM-5, particle size 100 nanometers, SiO2 / Al2O3molar ratio 20; 5 parts of base metal ion source, zinc nitrate, concentration 0.1 mole per liter; 1 part of functional modifier, 1 part of doped type modifier cerium nitrate; 3 parts of composite microspheres.

[0044] The composite microspheres are composed of the following components: 80 parts of mesoporous silica, type MCM-48, microsphere particle size 50 nanometers, mesoporous pore size 2 nanometers; 20 parts of chitosan; the composite microspheres are prepared by reacting mesoporous silica and chitosan in 1 wt% acetic acid aqueous solution, reaction temperature 30°C, reaction time 2 hours.

[0045] The preparation process is as follows: Step one, place the industrial-grade molecular sieve and the composite microspheres in an alcohol-water mixed system, the volume ratio of the alcohol-water mixed system is 1:1, the alcohol is ethanol; the ultrasonic power is 100 W, the ultrasonic time is 20 minutes, and a uniform dispersion liquid is obtained.

[0046] Step two, add the base metal ion source to the dispersion liquid, control the dropwise adding speed at 0.5 milliliters per minute to carry out coordination reaction, and at the same time, add the functional modifier to complete synchronous modification; the coordination reaction temperature is 25°C, the reaction time is 1 hour, the stirring speed is 300 revolutions per minute, and a coordination modification intermediate is obtained.

[0047] Step three, solidify the coordination modification intermediate at 50°C for 2 hours; the post-treatment includes centrifugation, washing, and vacuum drying, the centrifugal speed is 8000 revolutions per minute, the vacuum drying temperature is 60°C, and the drying time is 8 hours, and a low-cost MOF-type skeleton homogeneous particle based on molecular sieve is obtained.

[0048] Embodiment 2 The present embodiment 2 provides a low-cost MOF-based molecular sieve-based homogeneous particle, comprising the following components by mass fraction: Industrial grade molecular sieve 100 parts, type Y molecular sieve, particle size 500 nanometers, SiO2 / Al2O3 molar ratio 100; base metal ion source 20 parts, nickel chloride, concentration 0.5 moles per liter; functional modifier 5 parts, among which 3 parts of doped modifier thiourea and 2 parts of surface grafting modifier chloropropane; composite microspheres 8 parts.

[0049] The composite microspheres are composed of the following components: mesoporous silica 90 parts, type SBA-15, microsphere particle size 100 nanometers, mesoporous pore size 5 nanometers; chitosan 10 parts; the composite microspheres are prepared by reacting mesoporous silica and chitosan in 3wt% acetic acid aqueous solution, the reaction temperature is 50°C, and the reaction time is 4 hours.

[0050] The preparation process is as follows: Step one, place the industrial grade molecular sieve and the composite microspheres in an alcohol-water mixed system, the volume ratio of the alcohol-water mixed system is 3:1, the alcohol is isopropyl alcohol; the ultrasonic power is 300W, the ultrasonic time is 60 minutes, and a uniform dispersion liquid is obtained.

[0051] Step two, add the base metal ion source to the dispersion liquid, control the dropwise adding speed to 2 milliliters per minute for coordination reaction, and add the functional modifier at the same time to complete synchronous modification; the coordination reaction temperature is 40°C, the reaction time is 3 hours, the stirring speed is 500 revolutions per minute, and a coordination modification intermediate is obtained.

[0052] Step three, solidify the coordination modification intermediate at 80°C for 6 hours; the post-treatment includes centrifugation, washing, and vacuum drying, the centrifugal speed is 12000 revolutions per minute, the vacuum drying temperature is 80°C, and the drying time is 12 hours, to obtain the low-cost MOF-based molecular sieve-based homogeneous particle.

[0053] Comparative example 1 The present comparative example 1 provides a MOF-based skeleton particle, comprising the following components by mass fraction: Industrial grade molecular sieve 100 parts, type ZSM-5, particle size 100 nanometers, SiO2 / Al2O3 molar ratio 20; base metal ion source 5 parts, zinc nitrate, concentration 0.1 moles per liter; functional modifier 1 part, doped modifier cerium nitrate 1 part; no composite microspheres.

[0054] The preparation process is as follows: except that in step one, only the industrial grade molecular sieve is placed in the alcohol-water mixed system (volume ratio of alcohol-water mixed system 1:1, alcohol is ethanol), ultrasonic power 100 W, ultrasonic time 20 minutes, without adding composite microspheres, the specific steps are completely the same as those in example 1, including adding base metal ion source to the dispersion to control the dropping rate of 0.5 milliliters per minute, coordination reaction temperature 25℃, reaction time 1 hour, stirring speed 300 revolutions per minute, and 50℃ solidification for 2 hours, centrifugal speed 8000 revolutions per minute, vacuum drying temperature 60℃, drying time 8 hours, etc.

[0055] Comparative example 2 This comparative example 2 provides a traditional MOF particle, which comprises the following components by mass parts: Industrial grade molecular sieve 100 parts, type Y molecular sieve, particle size 500 nanometers, SiO2 / Al2O3molar ratio 100; base metal ion source 20 parts, nickel chloride, concentration 0.5 moles per liter; functional modifier 5 parts, among which, 3 parts of thiourea are doped as a modification agent, 2 parts of chloropropane are surface grafted as a modification agent; composite microspheres 8 parts; additional organic ligand terephthalic acid 10 parts, purity 99.5%.

[0056] The composite microspheres are composed of the following components: mesoporous silica 90 parts, type SBA-15, microsphere particle size 100 nanometers, mesoporous pore size 5 nanometers; chitosan 10 parts; the composite microspheres are prepared by reacting mesoporous silica and chitosan in 3wt% acetic acid aqueous solution, reaction temperature 50℃, reaction time 4 hours.

[0057] The preparation process is as follows: except that in step two, the organic ligand terephthalic acid is mixed with the base metal ion source first, and then the pre-reaction is carried out for 30 minutes before adding the dispersion, and the specific steps are completely the same as those in example 2, including volume ratio of alcohol-water mixed system 3:1, alcohol is isopropanol, ultrasonic power 300 W, ultrasonic time 60 minutes, dropping rate of base metal ion source 2 milliliters per minute, coordination reaction temperature 40℃, reaction time 3 hours, stirring speed 500 revolutions per minute, and 80℃ solidification for 6 hours, centrifugal speed 12000 revolutions per minute, vacuum drying temperature 80℃, drying time 12 hours, etc.

[0058] Experimental example 1 Test items and methods: Particle size deviation: laser particle size analyzer is used to measure particle size distribution according to GB / T19077-2016 standard, and (D90-D10) / D50x100% is calculated, unit is %; Pb 2 Adsorption capacity of Pb2+: according to HJ550-2015 standard, 0.1 grams of sample is added to 100 milliliters of Pb2+ solution with a concentration of 100 milligrams per liter, and the adsorption capacity of Pb2+ is calculated. 2The solution was incubated at 25°C with shaking for 2 hours, and the remaining Pb was determined using an atomic absorption spectrophotometer. 2 ⁺ concentration, used to calculate adsorption capacity, in milligrams per gram; Thermal stability (temperature at 5% weight loss): Using a thermogravimetric analyzer, according to GB / T27761-2011 standard, the temperature was increased to 500℃ at a rate of 10℃ per minute, and the temperature at which 5% weight loss was recorded, in ℃. CO2 / N2 separation coefficient: The adsorption capacity of CO2 and N2 was measured using a gas adsorption instrument according to GB / T39722-2020 standard at 25℃ and 1 bar, and the separation coefficient was calculated.

[0059] As shown in the table below: Sample Type Particle Size Deviation Pb 2 ⁺ adsorption capacity Thermal Stability CO2 / N2 separation factor Example 1 3 205 280 25 Example 2 4.5 240 310 32 Comparative Example 1 12 130 220 15 Comparative Example 2 6 230 290 28 In this experimental example, the particle size deviations of Examples 1 and 2 were 3% and 4.5%, respectively, both significantly lower than the 12% of Comparative Example 1, demonstrating that the composite microspheres can effectively inhibit particle aggregation and improve dispersion uniformity; Examples 1 and 2 showed a significant reduction in Pb... 2 The adsorption capacities were 205 mg / g and 240 mg / g, respectively; the thermal stability was 280℃ and 310℃, respectively; and the CO2 / N2 separation coefficients were 25 and 32, respectively, all of which were superior to those of Comparative Example 1. This indicates that the synergistic effect of the composite microspheres and other components can enhance the adsorption performance and structural stability. Although the adsorption capacity of Comparative Example 2 was close to that of Example 2, it relied on a high-valent organic ligand, and its thermal stability and separation coefficient were still lower than those of Example 2, proving that this scheme can achieve better overall performance without the need for organic ligands.

[0060] Experiment Example 2 Test objective: To verify whether the solution simultaneously achieves low cost, high adsorption efficiency, and long-term cycling stability.

[0061] Test items: Raw material cost: The cost of purchasing industrial-grade mass-production raw materials is calculated based on a single batch production scale of 100 kg, with the unit being RMB per kg; Adsorption rate: The adsorption rate of the sample to Pb was determined according to HJ550-2015 standard. 2 ⁺ The time required for adsorption to reach 80% of saturation capacity, in minutes; Adsorption retention rate after 5 cycles: According to HJ550-2015 standard, after adsorption saturation, desorb with 0.1 mol / L hydrochloric acid for 30 minutes, repeat adsorption-desorption 5 times, and calculate the ratio of the adsorption capacity of the 5th cycle to the adsorption capacity of the 1st cycle, in % (%). Mesopore size retention: The ratio of mesopore size to fresh sample mesopore size after 5 cycles was determined by nitrogen adsorption-desorption method according to GB / T19587-2017 standard, and the unit is %.

[0062] As shown in the table below: Sample Type Raw Material Cost Adsorption Rate 5 Cycle Adsorption Retention Mesopore Pore Size Retention Example 1 80 35 85 92 Example 2 85 28 88 94 Comparative Example 1 75 60 70 80 Comparative Example 2 1530 32 82 88 In the experimental example, the raw material cost of examples 1 and 2 is only 80 yuan per kilogram and 85 yuan per kilogram, which is much lower than 1530 yuan per kilogram of comparative example 2, proving that the scheme realizes a breakthrough in cost reduction by replacing organic ligands with molecular sieves; the adsorption rate of example 2 is 28 minutes, which is better than 60 minutes of comparative example 1, and the 5-time cycle adsorption retention rate is 88%, and the mesopore pore size retention rate is 94%, which are higher than those of comparative examples 1 and 2, indicating that the scheme takes into account high adsorption efficiency and long-term stability on the basis of low cost. Although the cost of comparative example 1 is slightly lower, the composite microspheres are missing, the adsorption rate is slow, and the cycle stability is poor, which further proves that the synergistic effect of each component is the key to the overall performance improvement.

[0063] It should be noted that, in this document, relational terms such as first and second and the like can be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0064] The preferred embodiments of the application disclosed above are only used to help explain the application. The preferred embodiments do not describe all the details of the application, nor limit the application to the specific embodiments described. Obviously, many modifications and variations can be made to the application based on the content of the specification. The specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the application, so that those skilled in the art can well understand and utilize the application. The application is limited only by the claims and their full scope and equivalents.

Claims

1. A low cost MOF-like framework homogeneous particle based on molecular sieves, characterized in that, It is composed of the following components by mass fraction: 100 parts of industrial-grade molecular sieve, 5-20 parts of base metal ion source, 1-5 parts of functional modifier and 3-8 parts of composite microspheres; The composite microspheres include 80-90 parts of mesoporous silica and 10-20 parts of chitosan. The industrial-grade molecular sieve provides natural coordination sites, the base metal ion source reacts with the coordination sites to construct a MOF-like skeleton, the functional modifier is doped or surface-grafted to modify the skeleton, and the composite microspheres form a synergistic effect to assist dispersion with the molecular sieve, thereby forming multifunctional composite particles together.

2. A low cost MOF class framework homogeneous particle based on molecular sieves according to claim 1, characterized in that: The industrial-grade molecular sieve at least includes one of ZSM-5, MCM-41, SBA-15 and Y-type molecular sieve, has a particle size of 100-500 nm and a SiO2 / Al2O3 molar ratio of 20-100.

3. A low cost MOF class framework homogeneous particle based on molecular sieves according to claim 1, characterized in that: The base metal ion source at least includes one of soluble salts containing Zn 2 ⁺, Cu 2 ⁺, Fe 3 ⁺, Ni 2 ⁺, at least one of which includes zinc nitrate, copper chloride, iron sulfate, nickel chloride, with a concentration of 0.1-0.5 mol / L.

4. The low cost MOF class framework homogeneous particle based on molecular sieves according to claim 1, characterized in that: the functional modifier comprises at least Ce 3 ⁺ salts, La 3 ⁺ salts, N-containing compounds, S-containing compounds, short-chain alkylating agents. The doping modifier at least includes one of cerium nitrate, lanthanum nitrate, urea and thiourea, and the amount is 1-3 parts; the surface grafting modifier at least includes one of chloromethane, bromoethane and chloropropane, and the amount is 0.5-2 parts.

5. A low cost MOF class framework homogeneous particle based on molecular sieves according to claim 1, characterized in that: In the composite microspheres, the mesoporous silica at least includes one of MCM-48 and SBA-15, has a microsphere particle size of 50-100 nm and a mesoporous pore size of 2-5 nm.

6. A low cost MOF class framework homogeneous particle based on molecular sieves according to claim 1, characterized in that: The composite microspheres are prepared by reacting mesoporous silica and chitosan in 1-3 wt% acetic acid aqueous solution, the reaction temperature is 30-50°C, and the reaction time is 2-4 h.

7. A method for preparing a low-cost MOF-based framework homogeneous particle based on a molecular sieve for preparing the low-cost MOF-based framework homogeneous particle according to any one of claims 1 to 6, characterized in that, The method comprises the following steps: Step one, placing the industrial-grade molecular sieve and the composite microspheres in an alcohol-water mixed system, ultrasonic dispersion, and obtaining a uniform dispersion liquid; Step two, adding an alkali metal ion source to the dispersion liquid, controlling the dropping rate to perform a coordination reaction, and adding a functional modifier to complete synchronous modification, and obtaining a coordination and modification intermediate; Step three, solidifying and post-treating the coordination and modification intermediate to obtain a low-cost MOF-like skeleton homogeneous particle based on the molecular sieve.

8. A low cost MOF based zeolite-like framework homogeneous particle preparation method according to claim 7, characterized by: In step one, the volume ratio of the alcohol-water mixed system is 1:1-3:1, the alcohol at least includes one of ethanol, propanol and isopropanol; the ultrasonic power is 100-300 W, and the ultrasonic time is 20-60 min.

9. The method of claim 7, wherein the method is characterized by: In step two, the dropping rate of the base metal ion source is 0.5-2 mL / min, the coordination reaction temperature is 25-40°C, the reaction time is 1-3 h, and the stirring rate is 300-500 rpm.

10. The method of claim 7, wherein the method is characterized by: In step three, the solidification temperature is 50-80°C, and the solidification time is 2-6 h; the post-treatment includes centrifugation, washing and vacuum drying, the centrifugation speed is 8000-12000 rpm, the vacuum drying temperature is 60-80°C, and the drying time is 8-12 h.

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