Zinc-based metal organic framework as well as preparation method and application thereof

Abstract

The invention provides a zinc-based metal organic framework as well as a preparation method and application thereof, the preparation method comprises the following steps: mixing a zinc source, an organic ligand and a catalyst, then extruding the obtained mixture at least once through extrusion equipment, and reacting to obtain the zinc-based metal organic framework. The preparation method provided by the invention is mild in condition, high-temperature and high-pressure reaction is not needed in the process, and the zinc-based metal organic framework can be rapidly and continuously synthesized; according to the preparation method, special production equipment is not needed, the process is simple, safe and controllable, the production difficulty, cost and equipment requirements are reduced, and the reaction rate, the product yield and the space time yield are remarkably increased under the assistance of the catalyst; the preparation method is green and environment-friendly, the zinc-based metal organic framework with adjustable structure and performance can be prepared, and the zinc-based metal organic framework has a very high industrial production prospect and is suitable for industrial large-scale production.

Description

Technical Field

[0001] The present invention belongs to the field of metal organic framework material synthesis, and in particular relates to a zinc-based metal organic framework and a preparation method and application thereof. Background Art

[0002] Metal organic frameworks (MOFs) are porous crystalline materials with a certain topological structure formed by the connection of metal ions or metal clusters with organic ligands. Because MOFs materials usually have a high specific surface area, high porosity, structural periodicity and adjustability, and are easy to functionalize, have adjustable pore sizes and structural diversity, they have received widespread attention in recent years as a new type of material with good application prospects. Research by numerous scientific researchers has shown that metal organic frameworks can be widely used in adsorption, separation, catalysis, energy storage, sensors, drug transport, carbon fixation and other fields. Due to the different ways in which metal ions are coordinated with organic ligands, there are many types of metal organic framework materials, and tens of thousands of metal organic framework materials have been synthesized.

[0003] An important branch of MOFs materials is zeolitic imidazolate framework materials (ZIFs). Currently, the most studied materials in this series are the ones that utilize Zn 2+ or Co 2+ A class of metal organic framework compound materials formed by self-assembly with imidazoles, which to some extent overcome the shortcomings of MOFs materials in terms of thermal stability, water stability and chemical stability. The typical representative is ZIF-8, which is formed by Zn 2+ The material with a zeolite-like framework topology structure obtained by coordination with 2-methylimidazole has a high specific surface area and good thermal stability, water stability and chemical stability.

[0004] Throughout the development of ZIF-8 synthesis and applications, researchers have continuously explored new methods to synthesize products with superior crystal structure, excellent performance, and high specific surface area. However, as people increasingly prioritize environmental issues related to the depletion of non-renewable resources, environmental pollution, global warming, and biodiversity loss, efforts are underway to identify new materials and environmentally friendly synthesis strategies as "green" processes. ZIF-8 synthesis methods have also evolved from solvothermal and hydrothermal methods at high temperatures and pressures to more energy-efficient methods at room temperature, such as room-temperature co-precipitation, sonochemistry, microwaves, and mechanical methods.

[0005] In recent years, mechanochemical methods have become more environmentally friendly in industrial preparation technology because they avoid or reduce the use of organic solvents and reduce reaction time compared to traditional solvent thermal and hydrothermal methods. They are also used for the synthesis of MOFs. Common mechanochemical methods include ball milling and extrusion. Ball milling can improve the reaction efficiency of some MOFs synthesis and reduce solvent usage, but it is usually an intermittent operation, and the uniformity and batch stability of large-scale production products are difficult to control. The extrusion method uses extrusion equipment to mix and react reactants under continuous pressure and shear conditions, and extruders are already conventional equipment used in industry, especially in the plastics, coatings, rubber and food industries. This method can easily control process conditions and achieve the goal of continuous and uniform production.

[0006] Patent CN105246906A discloses a "process for preparing metal organic compounds," which is a general synthesis method for preparing MOFs materials using an extruder as a reaction device. It has certain versatility, and in particular, the synthesis of some MOFs in the examples has very good yield (based on the raw materials) and time-space yield, which is a new method for preparing MOFs in uniform powder form. However, for the synthesis of zinc-based metal-organic frameworks, its metal ions are mainly basic zinc carbonate as the raw material, and the atomic utilization rate is not as good as ZnO and Zn(OH)2. In addition, the reaction requires an excess of ligands to synthesize MOFs with higher purity, resulting in the loss of some ligand raw materials, and the synthesized MOFs must be post-treated to remove excess ligands before further use.

[0007] Therefore, there is an urgent need to design a preparation method for zinc-based metal organic frameworks with simple process, high atomic utilization, fast reaction rate, high yield and low cost. Summary of the Invention

[0008] In response to the shortcomings of the prior art, the present invention aims to provide a zinc-based metal organic framework (MOF), a preparation method thereof, and its application. The preparation method provided by the present invention operates under mild conditions, does not require high temperature or high pressure reactions, and can rapidly and continuously synthesize the MOF. This preparation method does not require special production equipment, is simple in process, and is safe and controllable, reducing production difficulty, cost, and equipment requirements. Furthermore, with the assistance of a catalyst, it significantly improves the reaction rate, product yield, and space-time yield. This preparation method is environmentally friendly and can produce a MOF with adjustable structure and performance. It has high industrial production prospects and is suitable for industrial-scale production.

[0009] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a method for preparing a zinc-based metal organic framework, the preparation method comprising the following steps:

[0011] A zinc source, an organic ligand and a catalyst are mixed, and then the obtained mixture is extruded at least once through an extrusion device, and the zinc-based metal organic framework is obtained after reaction.

[0012] The preparation method provided by the present invention has mild conditions and does not require high temperature and high pressure reactions during the process, and can quickly and continuously synthesize a zinc-based metal organic framework. The preparation method does not require special production equipment, has a simple process, is safe and controllable, reduces production difficulty, cost and equipment requirements, and with the assistance of a catalyst, significantly improves the reaction rate, product yield and time-space yield. The preparation method is green and environmentally friendly, can prepare a zinc-based metal organic framework with adjustable structure and performance, has high industrial production prospects, and is suitable for industrial-scale production.

[0013] As a preferred technical solution of the present invention, the molar ratio of the zinc ions in the zinc source and the organic ligand is (1-2):(1-4), for example, it can be 1:1:, 1:2, 1:3, 1:4, 1.5:1, 1.5:2, 1.5:3, 1.5:4, 2:1, 2:2, 2:3 or 2:4, etc., preferably the stoichiometric ratio of the zinc ions in the zinc source and the organic ligand.

[0014] In the present invention, if the molar ratio of zinc ions to organic ligands in the zinc source is too small, that is, the content of organic ligands is too high, a further purification process is required to remove the excess ligands, which increases the number of preparation steps and causes loss of raw materials; if the molar ratio of zinc ions to organic ligands in the zinc source is too large, that is, the content of organic ligands is too low, the zinc source reaction is incomplete, the yield is reduced, and the product and the zinc source are difficult to separate and purify.

[0015] Preferably, based on the total weight of the zinc source, organic ligand and catalyst, the content of the organic ligand is 10-80%, for example, 10%, 20%, 30%, 40%, 50%, 60%, 70% or 80%, etc., preferably 40-75%.

[0016] Preferably, the organic ligand comprises at least one at least bidentate organic compound.

[0017] It should be noted that the at least bidentate organic compound can coordinate with the zinc ions in the zinc source.

[0018] Preferably, the at least bidentate organic compound includes any one of an imidazole compound, a triazole compound or a pyrimidine compound, or a combination of at least two of them.

[0019] Preferably, the imidazole compound includes any one of 2-methylimidazole, 2-ethylimidazole or benzimidazole, or a combination of at least two thereof, preferably 2-methylimidazole and / or 2-ethylimidazole.

[0020] Preferably, the triazole compound includes any one of 1,2,4-triazole, 3-amino-1,2,4-triazole or 3,5-diamino-1,2,4-triazole, or a combination of at least two thereof, preferably 1,2,4-triazole.

[0021] Preferably, the pyrimidine compound includes 2-hydroxypyrimidine and / or 4-hydroxypyrimidine.

[0022] Preferably, the zinc source comprises any one or a combination of at least two of zinc-containing chloride, zinc salt, zinc-containing oxide or zinc-containing hydroxide, preferably zinc-containing oxide and / or zinc-containing hydroxide.

[0023] Preferably, the zinc salt includes any one or a combination of at least two of zinc carbonate, basic zinc carbonate, zinc nitrate, zinc sulfate, zinc acetate or zinc oxalate, preferably zinc carbonate and / or basic zinc carbonate.

[0024] Preferably, the zinc-containing oxide comprises zinc oxide.

[0025] Preferably, the zinc-containing hydroxide comprises zinc hydroxide.

[0026] As a preferred technical solution of the present invention, based on the total weight of the zinc source, the organic ligand and the catalyst, the content of the catalyst is 0.1-10%, for example, it can be 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc., preferably 0.2-6%, and more preferably 0.4-4%.

[0027] In the present invention, the content of the catalyst is 0.1-10%. Within this range, the catalyst can play its due role and has little effect on the XRD analysis results of the product. If the content of the catalyst is too low, the reaction time is prolonged and the reaction rate is reduced, which is not conducive to the operation of the extrusion process, and the reaction is incomplete or even cannot be caused. If the content of the catalyst is too high, it causes waste of raw materials and even affects the change of the crystal structure of the product.

[0028] Preferably, the catalyst comprises any one of a soluble ammonium salt, a soluble salt containing a metal ion, or an acid, or a combination of at least two thereof.

[0029] Preferably, the soluble ammonium salt includes any one or a combination of at least two of ammonium carbonate, ammonium bicarbonate, ammonium nitrate, ammonium chloride, ammonium sulfate, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium oxalate or ammonium acetate.

[0030] Preferably, the soluble salt containing metal ions includes any one of nitrate, sulfate, formate, acetate, oxalate or chloride, or a combination of at least two thereof.

[0031] Preferably, the metal ions in the soluble salt containing metal ions include Cu 2+ 、Mn 2+ 、Co 2+ or Zn 2+ Any one or a combination of at least two of .

[0032] Preferably, the acid comprises any one of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, boric acid, formic acid, acetic acid, benzoic acid, oxalic acid, terephthalic acid, trimesic acid or fumaric acid, or a combination of at least two thereof.

[0033] As a preferred technical solution of the present invention, the rotation speed of the extrusion equipment is 15-600rpm, for example, it can be 15rpm, 30rpm, 50rpm, 100rpm, 200rpm, 300rpm, 400rpm or 500rpm, etc., preferably 15-400rpm, and more preferably 20-300rpm.

[0034] In the present invention, if the speed of the extruder is too low, the shear force generated is too small, the mixing effect is reduced, resulting in uneven preparation of the product, reduced reaction efficiency, and even incomplete reaction; if the speed of the extruder is too high, the mixing process and reaction time are too short, resulting in incomplete reaction.

[0035] Preferably, the residence time of the mixture in the extrusion device is 10-600s, for example, 10s, 50s, 100s, 200s, 300s, 400s, 500s or 600s, etc., preferably 30-480s, more preferably 60-300s.

[0036] It should be noted that the residence time is the reaction time of one extrusion process, which can be controlled by controlling the speed and length of the extrusion equipment.

[0037] Preferably, the extrusion is performed 1-5 times, for example, 1 time, 2 times, 3 times, 4 times or 5 times, preferably 1-3 times.

[0038] It should be noted that the reactants can be recycled through the extrusion equipment to meet the requirements.

[0039] Preferably, the feed rate of the mixture into the extrusion equipment is 1-5000 g / min, for example, it can be 1 g / min, 10 g / min, 100 g / min, 500 g / min, 1000 g / min, 2000 g / min, 3000 g / min, 4000 g / min or 5000 g / min, etc., preferably 10-3000 g / min.

[0040] It should be noted that the feeding speed of the mixture into the extrusion equipment is controlled by a feeding system.

[0041] As a preferred technical solution of the present invention, the extrusion equipment is a screw extruder.

[0042] Preferably, the screw extruder includes any one of a single-screw extruder, a twin-screw extruder or a multi-screw extruder, or a combination of at least two thereof, preferably a twin-screw extruder.

[0043] It should be noted that the multi-screw extruder refers to an extruder containing at least three screws.

[0044] Preferably, in the screw extruder, the aspect ratio of the screw is 1:(18-60), for example, it can be 1:18, 1:20, 1:30, 1:40, 1:50 or 1:60, etc., preferably 1:(25-56), and more preferably 1:(32-52).

[0045] As a preferred technical solution of the present invention, a diluent is further added during the mixing process;

[0046] The mixed method includes method 1 or method 2:

[0047] The specific steps of the method 1 include: blending a zinc source, an organic ligand and a catalyst to obtain a first mixture, and then conveying the first mixture and a diluent to an extrusion device in parallel;

[0048] The specific steps of the second method include: blending the zinc source and the organic ligand to obtain a second mixture, blending the diluent and the catalyst to obtain a third mixture, and then conveying the second mixture and the third mixture into an extrusion device in parallel.

[0049] In the present invention, the added diluent can be mixed with the zinc source, the organic ligand and the catalyst to form a homogeneous reaction system, so that the reaction is more complete.

[0050] In the present invention, compared with the first method, the catalyst is dissolved in the diluent and can be added to the second mixture in a more uniform manner, thereby uniformly inducing the reaction between the zinc source and the organic ligand during the mixing and dispersion process, avoiding the problem of uneven mixing and dispersion of the solid catalyst, and allowing the reaction to occur more rapidly and more fully.

[0051] Preferably, in the first and second methods, the diluent addition rate is independently 0.2-5000 mL / min, for example, it can be 0.2 mL / min, 0.5 mL / min, 1 mL / min, 10 mL / min, 100 mL / min, 1000 mL / min, 2000 mL / min, 3000 mL / min, 4000 mL / min or 5000 mL / min, etc., preferably 2-3000 mL / min.

[0052] It should be noted that the diluent is added by quantitative dropwise addition via a peristaltic pump or quantitative spraying via a spray system.

[0053] Preferably, in the first embodiment, the mass ratio of the diluent to the first mixture is (2-10):10, for example, 2:10, 4:10, 6:10, 8:10 or 10:10, and preferably (3-7):10.

[0054] Preferably, in the third mixture, the concentration of the catalyst is 0.1-50%, for example, 0.1%, 0.5%, 1%, 10%, 20%, 30%, 40% or 50%, etc., preferably 0.5-20%, more preferably 1-15%.

[0055] Preferably, in the first and second manners, the diluent independently includes water and / or an alcohol compound, preferably a combination of water and an alcohol compound.

[0056] Preferably, the alcohol compound includes any one of methanol, ethanol, isopropanol or n-propanol, or a combination of at least two of them.

[0057] Preferably, the volume ratio of water to alcohol compound is (0-100):(100-0), wherein the selection range of water "0-100" can be, for example, 0, 10, 30, 50, 70 or 90, and the selection range of alcohol compound "100-0" can be, for example, 0, 10, 30, 50, 70 or 90, preferably (0-70):(30-100), more preferably (5-50):(50-95), and further preferably (10-30):(70-90).

[0058] As a preferred technical solution of the present invention, a metal dopant is also added during the mixing process.

[0059] It should be noted that metal dopants can be added during the preparation process provided by the present invention to prepare the polymetallic organic framework, and functional structure modification can also be performed simultaneously to achieve functional goals.

[0060] Preferably, the metal element in the metal dopant includes any one or a combination of at least two of Cu, Mg, Co, Ca, Mn, Al, Fe, Sr, Ba, Sc, Y, Ln, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Re, Ru, Os, Rh, Ir, Ni, Pd, Pt, Ag, Au, Cd, Hg, Ga, In, Tl, Ge, Sn, Pb, As, Sb or Bi, and is preferably any one or a combination of at least two of Cu, Mn, Fe, Co, Ni, Al, Mg, Ti, Zr, Y, Sc, V, In, Ca, Cr, Mo, W or Ln.

[0061] As a preferred technical solution of the present invention, the reaction temperature is room temperature-200°C, for example, it can be 50°C, 100°C, 150°C or 200°C, preferably room temperature-80°C.

[0062] It should be noted that the present invention does not limit the specific temperature of room temperature. For example, it can be 20°C, 25°C or 30°C.

[0063] Preferably, the reaction is followed by further steps including any one or a combination of at least two of washing, drying or crushing.

[0064] It should be noted that washing, drying and crushing can be selected according to application requirements.

[0065] Preferably, the drying method includes any one of room temperature drying, heating evaporation, vacuum drying, freeze drying, spray drying or continuous tunnel kiln drying, or a combination of at least two thereof.

[0066] Preferably, the temperature of the heating evaporation is 30-200°C, for example, 30°C, 50°C, 100°C, 150°C or 200°C, etc., preferably 80-150°C.

[0067] In a second aspect, the present invention provides a zinc-based metal organic framework prepared by the preparation method according to the first aspect, wherein the space-time yield of the zinc-based metal organic framework is ≥5000 kg / m 3 / d, for example, it can be 5000kg / m 3 / d、10000kg / m 3 / d、50000kg / m 3 / d、70000kg / m 3 / d or 100000kg / m 3 / d, etc., preferably ≥50000kg / m 3 / d, more preferably ≥100000kg / m 3 / d.

[0068] It should be noted that the unit is kg / m 3 / d in, m 3 represents unit volume, d represents day, and refers to the unit reaction time.

[0069] Preferably, the crystal particle size D50 of the zinc-based metal organic framework is 50-300 nm, for example, it can be 50 nm, 100 nm, 150 nm, 200 nm, 250 nm or 300 nm.

[0070] Preferably, the particle size of the zinc-based metal organic framework is 50 nm-100 μm, for example, it can be 50 nm, 100 nm, 1 μm, 10 μm, 50 μm or 100 μm.

[0071] It should be noted that if the purity of the zinc-based metal organic framework needs to be improved, the obtained zinc-based metal organic framework can be washed with alcohol or water to remove a small amount of residual unreacted substances and catalysts, and then used for other purposes according to the use environment.

[0072] In a third aspect, the present invention provides an application of the zinc-based metal organic framework as described in the second aspect, wherein the zinc-based metal organic framework is used in the fields of adsorption, separation, catalysis, energy storage, sensors, drug transport and carbon fixation.

[0073] The numerical range described in the present invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0074] Compared with the prior art, the present invention has the following beneficial effects:

[0075] (1) The preparation method provided by the present invention has mild conditions and does not require high temperature and high pressure reaction, and can quickly and continuously synthesize zinc-based metal organic frameworks; the preparation method does not require special production equipment, has a simple process, is safe and controllable, reduces production difficulty, cost and equipment requirements, and with the assistance of a catalyst, significantly improves the reaction rate, product yield and time-space yield; the preparation method is green and environmentally friendly, can prepare a zinc-based metal organic framework with adjustable structure and performance, has a high industrial production prospect, and is suitable for industrial-scale production.

[0076] (2) The zinc-based metal organic framework prepared by the preparation method provided by the present invention can obtain a zinc-based organic framework powder with a good MOF crystal shape, and can be directly further processed, such as composite film formation or molding. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] Figure 1This is a schematic diagram of the process for preparing a zinc-based metal organic framework according to Example 1 of the present invention.

[0078] Figure 2 These are the XRD patterns of the zinc-based metal organic framework prepared in Example 1 of the present invention after single extrusion, double extrusion and post-treatment.

[0079] Figure 3 This is the XRD pattern of the zinc-based metal organic framework prepared in Examples 2-4 of the present invention.

[0080] Figure 4 The XRD patterns of the zinc-based metal organic frameworks prepared in Examples 6-7 and Comparative Example 1 of the present invention are shown.

[0081] Figure 5 This is the XRD pattern of the zinc-based metal organic framework prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0082] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0083] It should be noted that the room temperature below refers to 25°C.

[0084] Example 1

[0085] This embodiment provides a method for preparing a zinc-based metal organic framework, and its flow diagram is as follows: Figure 1 As shown, the preparation method comprises the following steps:

[0086] (1) physically mixing a zinc source (40.70 g zinc oxide, 0.5 mol), an organic ligand (82.1 g 2-methylimidazole, 1 mol), and 5 g catalyst (ammonium nitrate) to obtain a mixture;

[0087] The molar ratio of zinc ions in zinc oxide to 2-methylimidazole is 1:2, the content of 2-methylimidazole accounts for 64% of the total weight of the mixture, and the content of ammonium nitrate accounts for 4% of the total weight of the mixture;

[0088] (2) The obtained mixture was then fed to a twin-screw extruder using a feeder at a feed rate of 10 g / min. Simultaneously, 50 mL of methanol was fed to the twin-screw extruder at a rate of 4 mL / min using a peristaltic pump. The reaction was carried out at room temperature for 120 s to obtain a white powder product, which was recorded as one extrusion.

[0089] The total time for conveying and reacting was 12 min, the aspect ratio of the screws in the twin-screw extruder was 1:42, the rotation speed was 30 rpm, and the mass ratio of methanol to the mixture was 3.1:10;

[0090] (3) The white powder product was again fed to the twin-screw extruder at a feeding rate of 10 g / min. The obtained product was recorded as the second extrusion. Its XRD test was as follows: Figure 1 As shown in spectrum B, the product of the second extrusion was then washed with methanol to obtain a zinc-based metal organic framework, and its XRD test was as follows Figure 1 As shown in the C spectrum in , the crystal particle size D50 of the zinc-based metal organic framework is 240 nm, and the particle size of the zinc-based metal organic framework is 15 μm.

[0091] The white powder product obtained by extrusion in this embodiment was placed in an oven at 80°C for 8 hours for drying to obtain a dried product, which was subjected to XRD analysis. Figure 2 The product obtained by extrusion twice in this embodiment was placed in an oven at 80°C for 8 hours for drying to obtain a dried product, which was subjected to XRD testing. Figure 2 The Zn-based metal organic framework obtained after washing was subjected to XRD test, as shown in the B spectrum. Figure 2 As shown in the C spectrum, Figure 2 From the comparison of spectra A, B and C in the figure, it can be seen that a zinc-based metal organic framework with the crystal structure of 2-methylimidazole zinc salt can be prepared by one extrusion. Multiple extrusions can improve the degree of crystallization of the product. The washing process has a more obvious improvement on the crystal structure, and the catalyst and a small amount of unreacted ligand reactants can be removed.

[0092] Example 2

[0093] This embodiment provides a method for preparing a zinc-based metal organic framework, the preparation method comprising the following steps:

[0094] (1) Zinc oxide (813.9 g, 10 mol), 2-methylimidazole (1642 g, 20 mol) and 75 g of ammonium sulfate were physically mixed to obtain a mixture;

[0095] The molar ratio of zinc ions in zinc oxide to 2-methylimidazole is 1:2, the content of 2-methylimidazole accounts for 65% of the total weight of the mixture, and the content of ammonium sulfate accounts for 3% of the total weight of the mixture;

[0096] (2) The obtained mixture was then fed to a twin-screw extruder using a feeder at a feed rate of 30 g / min, and at the same time, a diluent with a volume of 850 mL (prepared by mixing methanol and water in a volume ratio of 4:1) was fed to the twin-screw extruder at a rate of 10 mL / min by a peristaltic pump, and the mixture was reacted at 80° C. for 120 s to obtain a white powder product, which was then dried in an oven at 80° C. for 8 h to obtain a zinc-based metal organic framework, wherein the crystal particle size D50 of the zinc-based metal organic framework was 200 nm and the particle size of the zinc-based metal organic framework was 10 μm;

[0097] The total time for conveying and reacting is 84 min, the aspect ratio of the screws in the twin-screw extruder is 1:42, the rotation speed is 100 rpm, and the mass ratio of the diluent to the mixture is 3:10.

[0098] Example 3

[0099] This embodiment provides a method for preparing a zinc-based metal organic framework, the preparation method comprising the following steps:

[0100] (1) Zinc oxide (40.7 g, 0.5 mol) and 2-methylimidazole (82.1 g, 1 mol) were physically mixed to obtain a mixture;

[0101] The molar ratio of zinc ions in zinc oxide to 2-methylimidazole is 1:2;

[0102] (2) dissolving 2 g of oxalic acid in 60 mL of ethanol to obtain a catalyst-containing dilution solution, wherein the concentration of the catalyst in the dilution solution is 4%;

[0103] The content of 2-methylimidazole accounts for 66% of the total weight of zinc oxide, 2-methylimidazole and oxalic acid, and the content of oxalic acid accounts for 2% of the total weight of zinc oxide, 2-methylimidazole and oxalic acid;

[0104] (3) The obtained mixture was fed to a twin-screw extruder using a feeder at a feed rate of 10 g / min, and the catalyst-containing diluent was fed to the twin-screw extruder at a rate of 5 mL / min by a peristaltic pump. The mixture was reacted at 80° C. for 90 s to obtain a white powder product, which was then dried in an oven at 80° C. for 8 h to obtain a zinc-based metal organic framework having a crystal particle size D50 of 220 nm and a particle size of 10 μm.

[0105] The total time for conveying and reacting is 12 minutes, the aspect ratio of the screws in the twin-screw extruder is 1:42, the rotation speed is 50 rpm, and the mass ratio of the diluent to the mixture is 3.9:10.

[0106] Example 4

[0107] This embodiment provides a method for preparing a zinc-based metal organic framework, the preparation method comprising the following steps:

[0108] (1) Zinc oxide (40.7 g, 0.5 mol) and 2-methylimidazole (82.1 g, 1 mol) were physically mixed to obtain a mixture;

[0109] The molar ratio of zinc ions in zinc oxide to 2-methylimidazole is 1:2;

[0110] (2) dissolving 0.65 g of hydrochloric acid in 60 mL of a mixture of ethanol and water (the volume ratio of ethanol to water is 7:3) to obtain a catalyst-containing dilution solution, wherein the concentration of the catalyst in the dilution solution is 1.1%;

[0111] The content of 2-methylimidazole accounts for 66.5% of the total weight of zinc oxide, 2-methylimidazole and hydrochloric acid, and the content of hydrochloric acid accounts for 0.5% of the total weight of zinc oxide, 2-methylimidazole and hydrochloric acid;

[0112] (3) The obtained mixture was fed to a twin-screw extruder using a feeder at a feed rate of 20 g / min, and the catalyst-containing diluent was fed to the twin-screw extruder at a rate of 10 mL / min by a peristaltic pump. The mixture was reacted at room temperature for 90 s to obtain a white powder product, which was then dried in an oven at 80° C. for 8 h to obtain a zinc-based metal organic framework having a crystal particle size D50 of 180 nm and a particle size of 6 μm.

[0113] The total time for conveying and reacting is 6 minutes, the aspect ratio of the screws in the twin-screw extruder is 1:42, the rotation speed is 50 rpm, and the mass ratio of the diluent to the mixture is 4.3:10.

[0114] Figure 3 The XRD patterns of the zinc-based metal organic frameworks prepared in Examples 2-4 are shown. As can be seen from the figure, the zinc-based metal organic frameworks prepared in Examples 2, 3 and 4 all have the crystal structure of 2-methylimidazole zinc, and the desired product can be obtained by only one extrusion, with a high yield.

[0115] Example 5

[0116] This embodiment provides a method for preparing a zinc-based metal organic framework, the preparation method comprising the following steps:

[0117] (1) Zinc oxide (40.70 g, 0.5 mol), 2-methylimidazole (20.525 g, 0.25 mol) and 5 g of ammonium nitrate were physically mixed to obtain a mixture;

[0118] The molar ratio of zinc ions in zinc oxide to 2-methylimidazole is 2:1, the content of 2-methylimidazole accounts for 31% of the total weight of the mixture, and the content of ammonium nitrate accounts for 8% of the total weight of the mixture;

[0119] (2) The obtained mixture was then fed to a twin-screw extruder using a feeder at a feed rate of 5 g / min. Simultaneously, 80 mL of methanol was fed to the twin-screw extruder using a peristaltic pump at a rate of 6.5 mL / min. The reaction was carried out at room temperature for 200 s to obtain a white powder product, which was recorded as one extrusion.

[0120] The aspect ratio of the screw in the twin-screw extruder is 1:52, the rotation speed is 20 rpm, and the mass ratio of methanol to the mixture is 9.8:10;

[0121] (3) The white powder product was again conveyed to the twin-screw extruder at a feeding rate of 5 g / min, and the obtained product was recorded as the second extrusion. The second extruded product was then placed in an oven at 80°C for 8 hours for drying to obtain a zinc-based metal organic framework. The crystal particle size D50 of the zinc-based metal organic framework was 180 nm, and the particle size of the zinc-based metal organic framework was 5 μm.

[0122] Example 6

[0123] This embodiment provides a method for preparing a zinc-based metal organic framework, the preparation method comprising the following steps:

[0124] (1) Zinc oxide (40.7 g, 0.5 mol) and 2-methylimidazole (82.1 g, 1 mol) were physically mixed to obtain a mixture;

[0125] The molar ratio of zinc ions in zinc oxide to 2-methylimidazole is 1:2;

[0126] (2) dissolving 5 g of ammonium sulfate in 60 mL of a diluent (composed of methanol and water in a volume ratio of 4:1) to obtain a catalyst-containing dilution solution, wherein the catalyst concentration in the dilution solution is 9%;

[0127] The content of 2-methylimidazole accounts for 64% of the total weight of zinc oxide, 2-methylimidazole and ammonium sulfate, and the content of ammonium sulfate accounts for 4% of the total weight of zinc oxide, 2-methylimidazole and ammonium sulfate;

[0128] (3) The obtained mixture was fed to a twin-screw extruder using a feeder at a feed rate of 10 g / min, and the catalyst-containing diluent was fed to the twin-screw extruder at a rate of 5 mL / min by a peristaltic pump. The mixture was reacted at 80° C. for 20 s to obtain a white powder product, which was then dried in an oven at 80° C. for 8 h to obtain a zinc-based metal organic framework having a crystal particle size D50 of 120 nm and a particle size of 4 μm.

[0129] The total time for conveying and reacting is 12 minutes, the aspect ratio of the screws in the twin-screw extruder is 1:42, the rotation speed is 400 rpm, and the mass ratio of the diluent to the mixture is 3.9:10.

[0130] Example 7

[0131] This embodiment provides a method for preparing a zinc-based metal organic framework, the preparation method comprising the following steps:

[0132] (1) Zinc oxide (40.7 g, 0.5 mol) and 2-methylimidazole (82.1 g, 1 mol) were physically mixed to obtain a mixture;

[0133] The molar ratio of zinc ions in zinc oxide to 2-methylimidazole is 1:2;

[0134] (2) dissolving 5 g of ammonium sulfate in 60 mL of a diluent (composed of methanol and water in a volume ratio of 4:1) to obtain a catalyst-containing dilution solution, wherein the catalyst concentration in the dilution solution is 9%;

[0135] The content of 2-methylimidazole accounts for 64% of the total weight of zinc oxide, 2-methylimidazole and ammonium sulfate, and the content of ammonium sulfate accounts for 4% of the total weight of zinc oxide, 2-methylimidazole and ammonium sulfate;

[0136] (3) The obtained mixture was fed to a twin-screw extruder using a feeder at a feed rate of 10 g / min, and the catalyst-containing diluent was fed to the twin-screw extruder at a rate of 5 mL / min by a peristaltic pump. The mixture was reacted at 80° C. for 25 s to obtain a white powder product. The white powder product was then fed to the twin-screw extruder again at a feed rate of 10 g / min. The cycle was repeated 5 times. Finally, the extruded product was dried in an oven at 80° C. for 8 h to obtain a zinc-based metal organic framework. The crystal particle size D50 of the zinc-based metal organic framework was 130 nm, and the particle size of the zinc-based metal organic framework was 5 μm.

[0137] The total time for conveying and reacting is 12 minutes, the aspect ratio of the screws in the twin-screw extruder is 1:48, the rotation speed is 400 rpm, and the mass ratio of the diluent to the mixture is 3.9:10.

[0138] Example 8

[0139] The difference between this embodiment and embodiment 3 is that the amount of 2-methylimidazole added is adjusted so that the molar ratio of zinc ions in zinc oxide to 2-methylimidazole in step (1) is 1:5.

[0140] The rest of the preparation methods and parameters remained the same as in Example 3.

[0141] Example 9

[0142] The difference between this embodiment and embodiment 3 is that the amount of 2-methylimidazole added is adjusted so that the molar ratio of zinc ions in zinc oxide to 2-methylimidazole in step (1) is 3:1.

[0143] The rest of the preparation methods and parameters remained the same as in Example 3.

[0144] Example 10

[0145] The difference between this embodiment and embodiment 3 is that the amount of oxalic acid added is adjusted so that the concentration of the catalyst in the diluted solution is 55%.

[0146] The rest of the preparation methods and parameters remained the same as in Example 3.

[0147] Example 11

[0148] The difference between this embodiment and embodiment 3 is that the rotation speed of the twin-screw extruder is 650 rpm.

[0149] The rest of the preparation methods and parameters remained the same as in Example 3.

[0150] Comparative Example 1

[0151] This comparative example provides a method for preparing a zinc-based metal organic framework, which comprises the following steps:

[0152] (1) Zinc oxide (40.7 g, 0.5 mol) and 2-methylimidazole (82.1 g, 1 mol) were physically mixed to obtain a mixture;

[0153] The molar ratio of zinc ions in zinc oxide to 2-methylimidazole is 1:2;

[0154] (2) The obtained mixture was fed to a twin-screw extruder using a feeder at a feed rate of 10 g / min, and 60 mL of ethanol was fed to the twin-screw extruder at a rate of 5 mL / min using a peristaltic pump. The mixture was reacted at 80° C. for 90 s to obtain a white powder product, which was then dried in an oven at 80° C. for 8 h to obtain a mixture of a zinc-based metal organic framework and the raw material. The particle size D50 of the mixture was 160 nm, and the particle size was 3 μm.

[0155] The total time for conveying and reacting is 12 minutes, the aspect ratio of the screws in the twin-screw extruder is 1:42, the rotation speed is 50 rpm, and the mass ratio of the diluent to the mixture is 3.9:10.

[0156] Figure 4 The XRD patterns of the zinc-based metal organic frameworks prepared in Examples 6-7 and Comparative Example 1 are shown, wherein spectrum A represents Example 5, spectrum B represents Example 6, and spectrum C represents Comparative Example 1. It can be seen that although the zinc-based metal organic frameworks prepared in Examples 6-7 and Comparative Example 1 have the crystal structure of 2-methylimidazole zinc, a ZnO peak is still detected, indicating that the reaction is incomplete.

[0157] Figure 5 The XRD pattern of the zinc-based metal organic framework prepared in this comparative example is shown. As can be seen from the figure, the product has characteristic peaks of ZnO, indicating that the reaction is not complete in the absence of a catalyst.

[0158] Performance Testing

[0159] The product yield and space-time yield of the methods provided in the above examples and comparative examples were tested, and the test results are shown in Table 1.

[0160] Table 1

[0161]

[0162] analyze:

[0163] As can be seen from the above table, the preparation method provided by the present invention, with the assistance of the catalyst, significantly improves the reaction rate, product yield, and space-time yield, and can produce a zinc-based metal-organic framework with adjustable structure and performance. It has high industrial production prospects and is suitable for industrial-scale production.

[0164] It can be seen from Examples 3 and 8-9 that if the molar ratio of zinc ions to 2-methylimidazole in zinc oxide is too small, the excess organic ligand requires further washing and purification processes to remove excess organic matter, resulting in loss of operating procedures and raw materials; if the molar ratio of zinc ions to 2-methylimidazole in zinc oxide is too large, the product has only a very weak characteristic peak of 2-methylimidazole zinc salt, and the main characteristic peak is zinc oxide. The zinc-based metal-organic framework formed is too small and cannot be separated and purified from the raw material zinc oxide, and cannot meet the use requirements.

[0165] It can be seen from Examples 3 and 10 that if the concentration of the catalyst in the dilution solution is too high, the reaction environment of the zinc salt and the organic ligand will be changed, the structure of the zinc-based metal organic framework will be destroyed, and the desired product cannot be obtained.

[0166] It can be seen from Examples 3 and 11 that if the speed of the twin-screw extruder is too high, the mixing and reaction time is too short, the yield of the formed product is not high, and multiple cycles of extrusion may be required, resulting in reduced efficiency and energy waste.

[0167] It can be seen from Example 3 and Comparative Example 1 that if no catalyst is added, the yield of the generated Zn-MOF is not high, and an additional washing and purification process is required to obtain a purer product, which results in a waste of raw materials.

[0168] The applicant states that while the above-described embodiments illustrate the process of the present invention, the present invention is not limited to the above-described process steps, nor does it imply that the present invention must rely on the above-described process steps for implementation. Those skilled in the art will appreciate that any improvements to the present invention, equivalent substitutions for the raw materials used, additions of auxiliary components, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing a zinc-based metal organic framework, characterized in that: The preparation method comprises the following steps: A zinc source, an organic ligand and a catalyst are mixed, and then the obtained mixture is extruded at least once through an extrusion device, and the zinc-based metal organic framework is obtained after reaction.

2. The preparation method according to claim 1, characterized in that The molar ratio of the zinc ions in the zinc source to the organic ligand is (1-2):(1-4), preferably the stoichiometric ratio of the zinc ions in the zinc source to the organic ligand; Preferably, the content of the organic ligand is 10-80%, preferably 40-75%, based on the total weight of the zinc source, the organic ligand and the catalyst; Preferably, the organic ligand comprises at least one at least bidentate organic compound; Preferably, the at least bidentate organic compound comprises any one or a combination of at least two of an imidazole compound, a triazole compound or a pyrimidine compound; Preferably, the zinc source comprises any one or a combination of at least two of zinc-containing chloride, zinc salt, zinc-containing oxide or zinc-containing hydroxide, preferably zinc-containing oxide and / or zinc-containing hydroxide.

3. The preparation method according to claim 1 or 2, characterized in that Based on the total weight of the zinc source, the organic ligand and the catalyst, the content of the catalyst is 0.1-10%, preferably 0.2-6%, and more preferably 0.4-4%; Preferably, the catalyst comprises any one of a soluble ammonium salt, a soluble salt containing a metal ion, or an acid, or a combination of at least two thereof.

4. The preparation method according to any one of claims 1 to 3, characterized in that The rotation speed of the extrusion equipment is 15-600 rpm, preferably 15-400 rpm, more preferably 20-300 rpm; Preferably, the residence time of the mixture in the extrusion device is 10-600s, preferably 30-480s, more preferably 60-300s; Preferably, the extrusion is performed 1-5 times, preferably 1-3 times; Preferably, the feed rate of the mixture into the extrusion device is 1-5000 g / min, preferably 10-3000 g / min.

5. The preparation method according to any one of claims 1 to 4, characterized in that The extrusion equipment is a screw extruder; Preferably, the screw extruder comprises any one of a single-screw extruder, a twin-screw extruder or a multi-screw extruder, or a combination of at least two thereof, preferably a twin-screw extruder; Preferably, in the screw extruder, the aspect ratio of the screw is 1:(18-60), preferably 1:(25-56), and more preferably 1:(32-52).

6. The preparation method according to any one of claims 1 to 5, characterized in that A diluent is also added during the mixing process; The mixed method includes method 1 or method 2: The specific steps of the method 1 include: blending a zinc source, an organic ligand and a catalyst to obtain a first mixture, and then conveying the first mixture and a diluent into an extrusion device in parallel; The specific steps of the second method include: blending a zinc source and an organic ligand to obtain a second mixture, blending a diluent and a catalyst to obtain a third mixture, and then conveying the second mixture and the third mixture to an extrusion device in parallel; Preferably, in the first and second methods, the diluent addition rate is independently 0.2-5000 mL / min, preferably 2-3000 mL / min; Preferably, in the first embodiment, the mass ratio of the diluent to the first mixture is (2-10):10, preferably (3-7):10; Preferably, in the third mixture, the concentration of the catalyst is 0.1-50%, preferably 0.5-20%, more preferably 1-15%; Preferably, in the first and second manners, the diluent independently includes water and / or an alcohol compound, preferably a combination of water and an alcohol compound.

7. The preparation method according to any one of claims 1 to 6, characterized in that: A metal dopant is also added during the mixing process; Preferably, the metal element in the metal dopant includes any one or a combination of at least two of Cu, Mg, Co, Ca, Mn, Al, Fe, Sr, Ba, Sc, Y, Ln, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Re, Ru, Os, Rh, Ir, Ni, Pd, Pt, Ag, Au, Cd, Hg, Ga, In, Tl, Ge, Sn, Pb, As, Sb or Bi, and is preferably any one or a combination of at least two of Cu, Mn, Fe, Co, Ni, Al, Mg, Ti, Zr, Y, Sc, V, In, Ca, Cr, Mo, W or Ln.

8. The preparation method according to any one of claims 1 to 7, characterized in that The reaction temperature is room temperature-200°C, preferably room temperature-80°C; Preferably, the reaction is followed by the following steps, including any one or a combination of at least two of washing, drying or crushing; Preferably, the drying method includes any one or a combination of at least two of room temperature drying, heating evaporation, vacuum drying, freeze drying, spray drying or continuous tunnel kiln drying; Preferably, the heating evaporation temperature is 30-200°C, preferably 80-150°C.

9. A zinc-based metal organic framework prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The space-time yield of the zinc-based metal organic framework is ≥5000 kg / m 3 / d, preferably ≥50000kg / m 3 / d, more preferably ≥100000kg / m 3 / d; Preferably, the crystal particle size D50 of the zinc-based metal organic framework is 50-300 nm; Preferably, the particle size of the zinc-based metal organic framework is 50 nm-100 μm.

10. A use of the zinc-based metal organic framework according to claim 9, characterized in that: The zinc-based metal organic framework is used in the fields of adsorption, separation, catalysis, energy storage, sensors, drug transport and carbon fixation.

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