Suspension containing MOF (Metal Organic Framework) fibers as well as preparation method and application of suspension

Abstract

The invention discloses a suspension containing MOF (Metal Organic Framework) fibers as well as a preparation method and application of the suspension. The preparation method of the suspension containing the MOF fiber comprises the following steps: dissolving an organic ligand in water to obtain a saturated organic ligand solution; heating the organic ligand solution to 50-200 DEG C, and adding an iron-based metal element salt for coordination reaction to obtain an iron-based coordination solution; then filtering the iron-based coordination solution and washing the iron-based coordination solution with water to remove unreacted organic ligands and quickly condense a product; and standing the product, and separating out crystals to obtain a suspension containing the MOF fibers. An in-situ hydrothermal synthesis method is adopted, iron series metal elements and organic ligands are coordinated to construct linear long-chain molecules, adjacent molecular chains attract each other through hydrogen bonds, and the MOF with the high length-diameter ratio and similar to a textile nanofiber structure is formed. Under pressure driving, the MOF fibers can be wound to form a self-supporting pure MOF fiber membrane, and the gas separation performance is excellent.

Description

Technical Field

[0001] The invention relates to the field of functional materials, in particular to a suspension containing MOF fibers and a preparation method and application thereof. Background Art

[0002] Membrane separation is a new gas separation technology. Compared with traditional separation technologies such as cryogenic distillation and pressure swing adsorption, it is easier to operate, has lower costs, occupies less space, and produces less carbon source and consumes less energy. Therefore, it is widely used in the field of gas separation.

[0003] Membrane materials are the key to determining membrane separation efficiency. Metal-organic framework (MOF) materials are currently one of the hottest materials for preparing high-performance gas separation membranes due to their unique advantages such as high porosity, high specific surface area, and adjustable pore size. However, MOF is a discrete crystal, and it is difficult to independently form a continuous self-supporting pure MOF membrane. Usually, a supporting layer such as alumina, titanium dioxide, and polymer membrane is required to provide strength for assembly into a membrane. However, due to the shortcomings of low strength and high price of inorganic alumina and titanium dioxide supporting layers, the polymer supporting layer has the disadvantage of low permeability coefficient, and the interaction between the MOF crystal layer and the supporting layer is weak, so it is urgent to develop new processes to prepare self-supporting pure MOF membranes, which is of great significance for promoting the development of MOF membranes in the field of gas separation. Summary of the invention

[0004] In view of the deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a suspension containing MOF fibers and a preparation method and application thereof.

[0005] The technical solution of the present invention to solve the technical problem of the method is to provide a method for preparing a suspension containing MOF fibers, which is characterized in that the method comprises the following steps:

[0006] Step 1, dissolving the organic ligand in water to obtain a saturated organic ligand solution;

[0007] Step 2, after heating the organic ligand solution to 50-200° C., adding an iron-based metal element salt to carry out coordination reaction to obtain an iron-based coordination solution;

[0008] Step 3: Filter the iron-based coordination solution obtained in step 2 and wash it with water to remove unreacted organic ligands and quickly condense the product; then let the product stand to precipitate crystals to obtain a suspension containing MOF fibers.

[0009] The technical solution of the present invention to solve the technical problem of the suspension is to provide a suspension containing MOF fibers prepared by a method for preparing a suspension containing MOF fibers.

[0010] The technical solution of the present invention to solve the application technical problem is to provide an application of a suspension containing MOF fibers, characterized in that the suspension containing MOF fibers is used as a raw material to obtain MOF fibers and a self-supporting MOF fiber membrane.

[0011] Compared with the prior art, the present invention has the following beneficial effects:

[0012] (1) The present invention uses an in-situ hydrothermal synthesis method to coordinate iron-based metal elements with organic ligands to construct linear long-chain molecules, and adjacent molecular chains attract each other through hydrogen bonds to form MOF fibers with a high aspect ratio similar to textile nanofiber structures. Under pressure, MOF fibers can be entangled into self-supporting pure MOF fiber membranes with excellent gas separation performance.

[0013] (2) The MOF fiber prepared by the present invention has a strength greater than 10 3 The high aspect ratio and textile-like nanofiber structure, chain-like molecular structure and hydrogen bonding interactions between adjacent chains make MOF fibers entangleable and flexible, and the fiber length can reach 1 mm.

[0014] (3) Under pressure, MOF fibers can be entangled to form self-supporting pure MOF fiber membranes, which can be used for gas separation, providing a new design idea for the application of pure MOF materials in the field of gas separation.

[0015] (4) The MOF fiber prepared by the present invention is suitable for a variety of industrial scenarios, including: sewage treatment (can be used to adsorb heavy metal ions and organic pollutants in sewage, thereby purifying sewage), chemical product separation and purification (can be used to separate and purify target products in chemical synthesis production, improve product purity and quality, and reduce impurity content), industrial solvent recovery (can be used to recover organic solvents in industrial production to obtain high-purity solvents), electronic industry gas purification (can be used in the precision electronics industry to remove trace harmful gases in the environment and ensure the ultra-clean state of the production environment), pharmaceutical industry solvent refining (can be used to remove trace impurities in solvents during the pharmaceutical process and improve the purity of solvents), air purification (can be used to adsorb pollutants in the air and improve air quality), gas separation and storage (can be used to adsorb gases with large interactions to achieve gas separation and storage).

[0016] (5) The self-supporting MOF fiber membrane prepared by the present invention is suitable for a variety of industrial scenarios, including: industrial waste gas purification (can be used to remove harmful gases generated in industrial production processes), natural gas purification (can be used to remove impurity gases from natural gas and improve the quality of natural gas), biogas purification (can be used to remove impurity gases from gases generated in the biomass fermentation process and improve the purity of biogas), fuel cell applications (can be used to provide high-purity hydrogen to improve the efficiency and life of fuel cells), air separation (can be used to separate oxygen, nitrogen and other components in the air for use in the medical, chemical and other fields), automobile exhaust treatment (can be used to capture and separate harmful components such as solid suspended particles, carbon monoxide, carbon dioxide, hydrocarbons, nitrogen oxides, lead and sulfur oxides in automobile exhaust to reduce harm to the environment and human body), air filtration (can be used to capture suspended solid and liquid droplets in the air and their mixtures to control and improve severe air pollution problems and reduce particulate matter inhaled by the human body). BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a crystal structure diagram of the MOF fiber prepared in the present invention along the a-axis;

[0018] Figure 2 The crystal structure diagram of the MOF fiber prepared by the present invention along the b axis;

[0019] Figure 3 This is a crystal structure diagram of the MOF fiber prepared in the present invention along the c-axis;

[0020] Figure 4 A hydrogen bond interaction diagram of the MOF fiber prepared in the present invention;

[0021] Figure 5 This is a surface morphology image of the MOF fiber of Example 1 of the present invention magnified 245 times;

[0022] Figure 6 This is a surface morphology image of the MOF fiber of Example 1 of the present invention magnified 8250 times;

[0023] Figure 7 This is a diameter distribution diagram of the MOF fiber of Example 1 of the present invention;

[0024] Figure 8 HRTEM image of the MOF fiber of Example 1 of the present invention;

[0025] Fig. 9 For the present invention Figure 8 SAED pattern of MOF fiber in the region;

[0026] Fig.10 This is a surface element distribution diagram of the MOF fiber of Example 1 of the present invention;

[0027] Fig.11 This is a surface morphology of the MOF fiber membrane of Example 1 of the present invention;

[0028] Fig.12 This is a cross-sectional morphology diagram of the MOF fiber membrane of Example 1 of the present invention;

[0029] Fig.13 This is a physical picture of the MOF fiber membrane of Example 1 of the present invention;

[0030] Fig.14 The single gas permeability coefficients of H2 and CO2 and the ideal selectivity diagram of H2 / CO2 of the MOF fiber membrane of Example 1 of the present invention are shown;

[0031] Fig.15 The H2 and CO2 mixed gas permeability coefficients and H2 / CO2 mixed gas separation selectivity diagram of the MOF fiber membrane of Example 1 of the present invention;

[0032] Fig.16 This is a physical picture of the MOF fiber membrane of Example 3 of the present invention. DETAILED DESCRIPTION

[0033] The specific embodiments of the present invention are given below. The specific embodiments are only used to further illustrate the present invention in detail and do not limit the protection scope of the present invention.

[0034] The present invention provides a method for preparing a suspension containing MOF fibers (hereinafter referred to as the method), which is characterized in that the method comprises the following steps:

[0035] Step 1, dissolving the organic ligand in water (preferably deionized water) to obtain a saturated organic ligand solution;

[0036] Preferably, in step 1, the organic ligand is an organic ligand with three carboxyl groups, specifically trimesic acid, trimellitic acid, tricarboxypyridine, 1,3,5-tri(4-carboxyphenyl)benzene or 2,4,6-triethyl-1,3,5-tricarboxybenzene.

[0037] Preferably, in step 1, the ratio of the mass of the organic ligand to the volume of water is 1-10 g:10-100 mL.

[0038] Preferably, in step 1, the dissolution process is: stirring at a speed of 300 to 600 r / min at room temperature for 10 to 60 min (preferably 20 to 60 min).

[0039] Step 2, after heating the organic ligand solution to 50-200° C., adding an iron-based metal element salt to carry out coordination reaction to obtain an iron-based coordination solution;

[0040] Preferably, in step 2, the iron-based metal element is iron, cobalt or nickel; and the salt is nitrate (preferably nitrate hydrate).

[0041] Preferably, in step 2, the iron-based metal element salt is nickel nitrate hexahydrate, cobalt nitrate hexahydrate or iron nitrate nonahydrate.

[0042] Preferably, in step 2, the mass ratio of the iron-based metal element salt to the organic ligand is 1-20:0.51-10.21.

[0043] Preferably, in step 2, the coordination reaction time is 5 to 60 minutes.

[0044] Step 3: Filter the iron-based coordination solution obtained in step 2 and wash it with water (preferably deionized water) to remove unreacted organic ligands and quickly condense the product; then let the product stand to precipitate crystals to obtain a suspension containing MOF fibers.

[0045] Preferably, in step 3, the filtration is performed by vacuum filtration.

[0046] Preferably, the volume ratio of the dissolving water in step 1 to the washing water in step 3 is 1-100:3.03-303.

[0047] Preferably, in step 3, the temperature of the washing water is room temperature.

[0048] Preferably, in step 3, the standing temperature is room temperature and the standing time is 5 to 120 min (preferably 1 to 60 min).

[0049] Depend on Figure 1-3 It can be seen that the three carboxyl groups of the organic ligand are deprotonated (-COO - ) and coordinate with three Ni(II) centers in a bidentate and two monodentate manners, respectively, to form a linear long-chain molecule.

[0050] Depend on Figure 4 It can be seen that each hexacoordinated Ni(II) ion is coordinated with four H2O molecules, and the adjacent molecular chains can construct a complex 3D network due to the strong hydrogen bonding interactions between the hydrogen ions and carboxylates of each H2O molecule.

[0051] The invention also provides a method for preparing a suspension containing MOF fibers and obtains the suspension containing MOF fibers.

[0052] The present invention also provides an application of a suspension containing MOF fibers, characterized in that the suspension containing MOF fibers is used as a raw material to obtain MOF fibers and a self-supporting MOF fiber membrane.

[0053] Preferably, the preparation method of MOF fiber is: take out the MOF fiber from the suspension containing MOF fiber by using a glass rod, dry and remove water, and obtain MOF fiber. The fiber is a nanometer-level fiber with an aspect ratio of more than 10. 3 The soft and slender body presents the appearance of a fiber with a high aspect ratio.

[0054] Preferably, the drying process is: drying at 30-180° C. for 12-240 hours.

[0055] Preferably, the preparation method of the self-supporting MOF fiber membrane is: filtering the suspension containing MOF fibers and washing with water (preferably deionized water) at the same time, so that the MOF fibers are tightly stacked and entangled into a MOF fiber membrane, and after drying, a self-supporting MOF fiber membrane is obtained.

[0056] Preferably, the filtration pressure is -0.01 to -0.1 MPa; the drying process is: natural drying for 12 to 60 hours in an atmospheric environment and at room temperature; the volume ratio of the dissolving water to the washing water in step 1 is 1 to 100:3.03 to 303.

[0057] In the embodiment, the surface morphology and fiber structure of MOF fiber and self-supporting MOF fiber membrane are observed using scanning electron microscope (SEM). The internal structure and crystal morphology of the fiber are observed using transmission electron microscope (TEM). Energy dispersive X-ray spectroscopy (EDS) analysis is performed to determine the elemental composition of the fiber. The permeability coefficient of different gases is determined using analytical means such as gas chromatography.

[0058] Embodiment 1:

[0059] Preparation of suspension containing MOF fibers:

[0060] (1) 5.106 g of trimesic acid was added to 33 mL of deionized water, and the mixture was magnetically stirred at 500 r / min for 30 min at room temperature to obtain a saturated trimesic acid solution;

[0061] (2) using a Wiggens WH240-R heater to heat the trimesic acid solution to 150° C., adding 10 g of nickel nitrate hexahydrate and continuing heating for 20 min to perform a coordination reaction, thereby obtaining an iron-based coordination solution;

[0062] (3) The iron-based coordination solution was filtered by vacuum filtration and washed with 100 mL of deionized water to remove trimesic acid that did not participate in the coordination reaction and quickly condense the product; finally, the solution was allowed to stand at room temperature for 60 minutes to precipitate crystals, thereby obtaining a suspension containing MOF fibers.

[0063] Preparation of MOF fibers: The MOF fibers were taken out from a suspension containing the MOF fibers using a glass rod, and then the MOF fibers were dried at 80° C. for 24 h to obtain MOF fibers.

[0064] Preparation of self-supporting MOF fiber membrane: The suspension containing MOF fibers was filtered (pressure was -0.075 MPa) and washed with 100 mL of deionized water, so that the MOF fibers were tightly stacked and entangled into a MOF fiber membrane; then naturally dried in atmospheric environment for 24 hours to prepare a self-supporting MOF fiber membrane with a certain thickness.

[0065] The test results show that the length of MOF fiber is 1 mm and the average fiber diameter is 0.54 μm. Under the single-component gas test conditions, the H2 permeability coefficient of the self-supporting MOF fiber membrane is 64.4×10 6 Barrer, the ideal separation selectivity of H2 / CO2 is 6.22. Under the test conditions of equal volume H2 and CO2 mixed gas, the H2 permeability coefficient of the self-supporting MOF fiber membrane is 21.8×10 6 Barrer, the separation selectivity of H2 / CO2 is 5.04.

[0066] Depend on Figure 5-7 It can be seen that the MOF fibers present a fiber appearance with a high aspect ratio, a length of 1 mm, an average fiber diameter of 0.54 μm, and a fiber thickness of 85 nm.

[0067] Depend on Figure 8-9 It can be seen that the surface of the MOF fiber is smooth and defect-free, and the atoms that make up the MOF fiber are arranged in a periodic and orderly manner, forming a single crystal structure.

[0068] Depend on Fig.10 It can be seen that C, O and Ni elements are evenly distributed on the MOF fibers.

[0069] Depend on Figure 11-13 It can be seen that the fibers in the membrane are tightly packed and the area of ​​the membrane is 10 cm 2 .

[0070] Depend on Fig.14 It can be seen that the H2 permeability coefficient of the self-supporting MOF fiber membrane under the single-component gas test condition is 64.4×10 6 Barrer, the ideal separation selectivity of H2 / CO2 is 6.22.

[0071] Depend on Fig.15 It can be seen that the H2 permeability coefficient of the self-supporting MOF fiber membrane is 21.8×10 6 Barrer, the separation selectivity of H2 / CO2 is 5.04.

[0072] Embodiment 2:

[0073] Preparation of suspension containing MOF fibers:

[0074] (1) 3 g of trimesic acid was added to 19.38 mL of deionized water, and the mixture was magnetically stirred at 400 r / min for 20 min at room temperature to obtain a saturated trimesic acid solution;

[0075] (2) using a Wiggens WH240-R heater to heat the trimesic acid solution to 120° C., adding 5.88 g of nickel nitrate hexahydrate and continuing heating for 15 min to carry out a coordination reaction, thereby obtaining an iron-based coordination solution;

[0076] (3) The iron-based coordination solution was filtered by vacuum filtration and washed with 60 mL of deionized water to remove trimesic acid that did not participate in the coordination reaction and quickly condense the product; finally, the solution was allowed to stand at room temperature for 30 minutes to precipitate crystals and obtain a suspension containing MOF fibers.

[0077] Preparation of MOF fibers: The MOF fibers were taken out from a suspension containing the MOF fibers using a glass rod, and then the MOF fibers were dried at 80° C. for 24 h to obtain MOF fibers.

[0078] Preparation of self-supporting MOF fiber membrane: The suspension containing MOF fibers was filtered (pressure was -0.075 MPa) and washed with 60 mL of deionized water, so that the MOF fibers were tightly stacked and entangled into a MOF fiber membrane; then it was naturally dried in atmospheric environment for 20 hours to prepare a self-supporting MOF fiber membrane with a certain thickness.

[0079] Embodiment 3:

[0080] Preparation of the suspension containing MOF fibers: The method is exactly the same as that in Example 1, except that in step (2), nickel nitrate hexahydrate is replaced with cobalt nitrate hexahydrate.

[0081] The preparation of MOF fibers and the preparation of self-supporting MOF fiber membranes are exactly the same as in Example 1.

[0082] After testing, by Fig.16 It can be seen that the area of ​​the membrane is 10 cm 2 .

[0083] Embodiment 4:

[0084] Preparation of suspension containing MOF fibers:

[0085] (1) 7 g of trimesic acid was added to 45.22 mL of deionized water, and the mixture was magnetically stirred at 550 r / min for 50 min at room temperature to obtain a saturated trimesic acid solution;

[0086] (2) After heating the trimesic acid solution to 170° C. using a Wiggens WH240-R heater, 13.72 g of nickel nitrate hexahydrate was added and heated for 30 min to perform a coordination reaction, thereby obtaining an iron-based coordination solution;

[0087] (3) The iron-based coordination solution was filtered by vacuum filtration and washed with 140 mL of deionized water to remove trimesic acid that did not participate in the coordination reaction and quickly condense the product; finally, the solution was allowed to stand at room temperature for 90 minutes to precipitate crystals and obtain a suspension containing MOF fibers.

[0088] Preparation of MOF fibers: The MOF fibers were taken out from a suspension containing the MOF fibers using a glass rod, and then the MOF fibers were dried at 80° C. for 24 h to obtain MOF fibers.

[0089] Preparation of self-supporting MOF fiber membrane: The suspension containing MOF fibers was filtered (pressure was -0.075 MPa) and washed with 140 mL of deionized water, so that the MOF fibers were tightly stacked and entangled into a MOF fiber membrane; then naturally dried in atmospheric environment for 48 hours to prepare a self-supporting MOF fiber membrane with a certain thickness.

[0090] Embodiment 5:

[0091] Preparation of suspension containing MOF fibers:

[0092] (1) adding 10 g of trimesic acid to 64.63 mL of deionized water, and stirring the mixture with a magnetic stirrer at 600 r / min for 60 min at room temperature to obtain a saturated trimesic acid solution;

[0093] (2) using a Wiggens WH240-R heater to heat the trimesic acid solution to 200° C., adding 19.58 g of nickel nitrate hexahydrate and continuing heating for 60 min to carry out a coordination reaction, thereby obtaining an iron-based coordination solution;

[0094] (3) The iron-based coordination solution was filtered by vacuum filtration and washed with 200 mL of deionized water to remove trimesic acid that did not participate in the coordination reaction and quickly condense the product; finally, the solution was allowed to stand at room temperature for 120 min to precipitate crystals and obtain a suspension containing MOF fibers.

[0095] Preparation of MOF fibers: The MOF fibers were taken out from a suspension containing the MOF fibers using a glass rod, and then the MOF fibers were dried at 80° C. for 24 h to obtain MOF fibers.

[0096] Preparation of self-supporting MOF fiber membrane: The suspension containing MOF fibers was filtered (pressure was -0.075 MPa) and washed with 200 mL of deionized water, so that the MOF fibers were tightly stacked and entangled into a MOF fiber membrane; then it was naturally dried in atmospheric environment for 60 hours to prepare a self-supporting MOF fiber membrane with a certain thickness.

[0097] Any matters not described in the present invention are applicable to the prior art.

Claims

1. A method for preparing a suspension containing MOF fibers, characterized in that the method comprises the following steps: Step 1, dissolving the organic ligand in water to obtain a saturated organic ligand solution; Step 2, after heating the organic ligand solution to 50-200° C., adding an iron-based metal element salt to carry out coordination reaction to obtain an iron-based coordination solution; Step 3: Filter the iron-based coordination solution obtained in step 2 and wash it with water to remove unreacted organic ligands and quickly condense the product; then let the product stand to precipitate crystals to obtain a suspension containing MOF fibers.

2. The method for preparing a suspension containing MOF fibers according to claim 1, characterized in that: In step 1, the organic ligand is an organic ligand with three carboxyl groups; In step 1, the ratio of the mass of the organic ligand to the volume of water is 1-10 g:10-100 mL; In step 1, the dissolution process is: stirring at a speed of 300 to 600 r / min at room temperature for 10 to 60 minutes.

3. The method for preparing a suspension containing MOF fibers according to claim 1 or 2, characterized in that: The organic ligand is trimesic acid, trimellitic acid, tricarboxypyridine, 1,3,5-tris(4-carboxyphenyl)benzene or 2,4,6-triethyl-1,3,5-tricarboxybenzene.

4. The method for preparing a suspension containing MOF fibers according to claim 1, characterized in that: In step 2, the iron-based metal element is iron, cobalt or nickel; the salt is nitrate; In step 2, the mass ratio of the iron-based metal element salt to the organic ligand is 1-20:0.51-10.21; In step 2, the coordination reaction time is 5 to 60 minutes.

5. The method for preparing a suspension containing MOF fibers according to claim 1 or 4, characterized in that: In step 2, the iron-based metal element salt is nickel nitrate hexahydrate, cobalt nitrate hexahydrate or iron nitrate nonahydrate.

6. The method for preparing a suspension containing MOF fibers according to claim 1, characterized in that: The volume ratio of the dissolving water in step 1 to the washing water in step 3 is 1-100:3.03-303; In step 3, the temperature of the washing water is room temperature; In step 3, the standing temperature is room temperature and the standing time is 5 to 120 minutes.

7. A suspension containing MOF fibers prepared by the method for preparing a suspension containing MOF fibers according to any one of claims 1 to 6.

8. Use of the suspension containing MOF fibers according to claim 7, characterized in that: The suspension containing the MOF fibers is used as a raw material to obtain MOF fibers and a self-supporting MOF fiber membrane.

9. The use according to claim 8, characterized in that: The preparation method of MOF fiber is as follows: taking out MOF fiber from a suspension containing MOF fiber, drying and removing water, and obtaining MOF fiber; The drying process is: drying at 30-180°C for 12-240 hours.

10. The use according to claim 8, characterized in that: The preparation method of the self-supporting MOF fiber membrane is as follows: a suspension containing MOF fibers is filtered and washed with water at the same time, so that the MOF fibers are tightly stacked and entangled into a MOF fiber membrane, and after drying, a self-supporting MOF fiber membrane is obtained; The filtration pressure is -0.01~-0.1Mpa; The drying process is: natural drying in atmospheric environment and room temperature for 12 to 60 hours.

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