Preparation method and application of calcium-based organic framework for selectively adsorbing fishy smell substances

Abstract

The present invention discloses a preparation method and application of a calcium-based metal-organic framework (Ca-MOF) for selectively adsorbing fishy smell substances, relating to the technical field of metal-organic framework materials; the preparation method comprises the following steps: dissolving an organic acid and a calcium salt in an organic solvent; transferring the fully dissolved solution to a high-pressure reactor for high-temperature reaction, and then cooling to room temperature; centrifuging, washing with alcohol, and drying the cooled solution to obtain Ca-MOF crystals. The calcium-based metal-organic framework prepared in the present invention has a significant selective adsorption effect on sulfur-containing compounds in fishy smell substances, and the adsorption rate for dimethyl trisulfide can reach 97.3%, with a fast adsorption rate. The calcium-based metal-organic framework has diverse application scenarios and can be directly added to foods or used as an external adsorption package. Therefore, the calcium-based metal-organic framework with selective adsorption can efficiently adsorb and remove sulfur-containing odor substances and can be used in multiple fields such as foods, medicines, and pesticides.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal-organic framework materials, and relates to a preparation method and application of a calcium-based organic framework for selectively adsorbing fishy substances. Background Art

[0002] As one of the three major animal foods alongside livestock and poultry meats and eggs, aquatic products provide high-quality protein required by humans, and have advantages such as high nutritional value, delicious taste, and low calories, and are deeply favored by consumers. The derived surimi products have high economic value. However, due to the fact that fish meat is extremely prone to lipid oxidation, enzymatic reactions, and microbial degradation, and itself has a strong earthy smell, it is extremely easy to produce unpleasant odors during processing and storage, resulting in spoilage of fish meat, waste of a large amount of fish protein resources, and greatly affecting the consumption and processing of fish meat.

[0003] The fishy smell of aquatic products is mainly caused by substances such as hexanal, nonanal, 4-heptenal, 2,4-heptadienal, and 1-octen-3-ol produced by lipid oxidation, nitrogen- and sulfur-containing substances produced by protein degradation, and geosmin and 2-methylisoborneol produced by microbial metabolism in the water environment. Among them, the sulfur-containing substances with a garlic smell and a fishy smell contribute greatly to the fishy smell due to their high content and low threshold, but are difficult to remove. Therefore, the problems of strong fishy smell and difficulty in removing it in aquatic products have seriously hindered the further development of the aquatic product industry. Summary of the Invention

[0004] The present invention provides a preparation method and application of a calcium-based metal-organic framework for selectively adsorbing fishy substances, and uses its high specific surface area and unsaturated metal sites to adsorb and remove the fishy smell of aquatic products, so as to solve the problems of strong fishy smell and difficulty in removing it in aquatic products. The preparation process is simple, the adsorption performance is excellent, and it has great application prospects.

[0005] To achieve the above object, the present invention is realized by adopting the following technical solutions:

[0006] A preparation method of a calcium-based metal-organic framework for selectively adsorbing fishy substances, the method comprising the following steps:

[0007] S1. Dissolve an organic acid and a calcium salt in an organic reagent;

[0008] S2. After dissolution, transfer the solution to a reaction kettle for high-temperature reaction, and then cool it to room temperature;

[0009] S3. Centrifuge, wash with alcohol, and dry the cooled solution to obtain Ca-MOF crystals.

[0010] Preferably, the organic acid in S1 is one or a combination of fumaric acid, succinic acid, lactic acid, oxalic acid, citric acid, malic acid, benzoic acid, cinnamic acid, caffeic acid, ferulic acid, p-coumaric acid, sinapic acid, and syringic acid.

[0011] Preferably, the calcium salt in S1 is one or a combination of calcium acetate, calcium carbonate, calcium chloride, calcium nitrate, calcium phosphate, and calcium hydrogen phosphate, and the molar ratio of the organic acid to the calcium salt is 1: (1 to 5).

[0012] Preferably, the organic acid in S1 can be used after being modified with an ammonium salt. The ammonium salt is one or a combination of ammonium bicarbonate, ammonium carbonate, ammonium chloride, ammonium phosphate, and ammonium hydrogen phosphate. The modification method is that the ammonium salt and the organic acid are dissolved in a saturated NaCl solution, and the molar ratio of the ammonium salt to the organic acid is 1: (1 to 5). After generating the organic acid monoammonium salt, it is dissolved in an organic solvent with the calcium salt. The organic reagent is methanol or ethanol, and the volume ratio of the organic solvent to water in the organic reagent is 1: (1 to 5).

[0013] More preferably, an ammonium salt can be added to the organic acid and the calcium salt in S1. The ammonium salt is one or a combination of ammonium bicarbonate, ammonium carbonate, ammonium chloride, ammonium phosphate, and ammonium hydrogen phosphate, and the molar ratio of the ammonium salt, the organic acid, and the calcium salt is 1: (1 to 5): (1 to 5).

[0014] Preferably, the high-temperature reaction in S2 is specifically: placing the high-pressure reactor at 60 to 300 °C, and the reaction time is 6 to 72 h.

[0015] Preferably, the alcohol washing in S3 is carried out with ethanol or methanol for 1 to 5 times, and the drying conditions are: vacuum drying at 20 to 100 °C for 1 to 24 h, and the pressure is -0.01 to -0.1 MPa.

[0016] The calcium-based metal-organic framework with selective adsorption obtained by the preparation method can participate in the preparation process of the γ-cyclodextrin metal-organic framework, and a composite supramolecular MOF is prepared by the method of nucleation kinetics-guided growth and then used for adsorption.

[0017] The calcium-based metal-organic framework with selective adsorption obtained by the preparation method is used for adsorbing various substances such as sulfur-containing, aldehyde-containing, alcohol-containing, nitrogen-containing, and heterocyclic substances, and can be used in an external adsorption package or directly added to food.

[0018] Preferably, the calcium-based organic framework with selective adsorption obtained by the preparation method is characterized in that the calcium-based organic framework is used for the separation and purification of gases in the chemical industry, for the adsorption and removal of heavy metals and pesticides in the treatment of three wastes, and can also be used as a biological or electrochemical sensor to detect toxins, heavy metals, and pesticides, and as a drug carrier in the pharmaceutical industry.

[0019] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0020] (1) The Ca-MOF prepared in the present invention has three advantages. First, it can efficiently adsorb various bad fishy smell substances. Second, Ca 2+ can enhance the gel strength of surimi and inhibit the release of fishy smell. Third, it introduces the essential macroelement Ca for the human body.

[0021] (2) The Ca-MOF prepared in the present invention has a variety of application scenarios. It can not only be directly added to food, but also be used as an external adsorption package to significantly remove various odor substances.

[0022] (3) The Ca-MOF prepared in the present invention is structurally characterized by a powder X-ray diffractometer, a specific surface area and porosity analyzer, and a Fourier transform infrared spectrometer. The results show that the Ca-MOF has been successfully prepared and has a high specific surface area (600 - 1200 m 2 / g)

[0023] (4) The adsorption experiment results of the present invention show that Ca-MOF has an extremely high selective adsorption ability for sulfur-containing fishy smell substances. Among them, the adsorption rate of dimethyl trisulfide can reach 97.3%, and the adsorption equilibrium can be achieved in 30 minutes.

[0024] (5) The functionalized and modified Ca-MOF prepared in the present invention can significantly improve the adsorption of sulfur-containing substances due to the increase of polar adsorption sites.

[0025] (6) The composite supramolecular MOF material prepared in the present invention has microporous, mesoporous and macroporous structures, which greatly broadens the adsorption range of the adsorbent and can significantly improve the adsorption ability of various substances.

[0026] (7) The present invention combines food science, material preparation technology and physical adsorption principle to develop a calcium-based metal-organic framework with selective adsorption. It not only broadens the application of metal-organic frameworks in the food field, but also provides a green and safe porous material that can be applied in multiple fields such as chemical engineering, three wastes treatment, medicine, and food safety detection. Description of the Drawings

[0027] Figure 1 is a flow chart of a method for preparing a calcium-based metal-organic framework for selectively adsorbing sulfur-containing fishy smell substances in the present invention;

[0028] Figure 2 is the powder X-ray diffraction pattern of Ca-MOF in Example 1 of the present invention;

[0029] Figure 3 is the Fourier transform infrared spectrum of Ca-MOF in Example 1 of the present invention;

[0030] Figure 4 It is the N2 isothermal adsorption and desorption curve of Ca-MOF in Example 1 of the present invention;

[0031] Figure 5 It is the pore size distribution diagram of Ca-MOF in Example 1 of the present invention;

[0032] Figure 6 It is the powder X-ray diffraction pattern of Example 1 of the present invention and the comparative example

[0033] Figure 7 It is the Fourier infrared spectrum of Example 1 of the present invention and the comparative example. Detailed implementation manners

[0034] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0035] Example 1

[0036] The preparation of a calcium-based metal-organic framework with selective adsorption is as follows: Refer to Figure 1 , accurately weigh 5 g of fumaric acid and 5 g of calcium acetate, dissolve them in a solution of methanol (10 mL) and ultrapure water (20 mL), and stir magnetically until fully dissolved. Transfer the solution to a polytetrafluoroethylene high-pressure reaction kettle, react at 120 °C for 24 h, cool to room temperature, centrifuge to obtain white crystals, wash with methanol 3 times, and dry in vacuum at 60 °C for 4 h to obtain Ca-MOF1.

[0037] Figure 2 It is the XRD pattern of Ca-MOF1, showing that Ca-MOF1 has a good crystalline structure, and sharp diffraction peaks appear at 10.3°, 13.9°, 14.6°, 19.8°, 28.6°, and 38.2° respectively, which is consistent with the XRD spectrum simulated by Materials Studio software; Figure 1 consistent; Figure 3 It is the FTIR spectrum of Ca-MOF1, showing absorption peaks at 3465, 1530, and 1407 cm -1 −1, which are attributed to the O-H stretching vibration and the symmetric and asymmetric stretching vibrations of C=O respectively, and at 1203, 983, and 817 cm-1 There are sharp and strong absorption peaks, indicating that the carboxyl group of fumaric acid coordinates with Ca, and the peak at 664 cm -1 is attributed to the vibration of Ca-O. The XRD and FTIR results prove the successful synthesis of the Ca-MOF material.

[0038] Combined with Figure 4 the N2 adsorption-desorption isotherm curve of Figure 5 and the pore size distribution diagram of 2 it shows that the specific surface area of Ca-MOF1 is 762.272 m

[0039] Experimental verification of the deodorization application in this example:

[0040] (1) Static adsorption test;

[0041] The standard products of the characteristic fishy substances nonanal, 1-octen-3-ol, dimethyl trisulfide, trimethylamine, and 2-methylisoborneol were first dissolved in methanol. According to the proportion of the odor activity values (OVA values) of different substances in surimi, solutions of different concentrations of fishy substances were prepared by diluting with ultrapure water (nonanal 150 μg / mL, 1-octen-3-ol 350 μg / mL, dimethyl trisulfide 200 μg / mL, trimethylamine 500 μg / mL, and 2-methylisoborneol 15 μg / mL). Weigh 1 g of Ca-MOF1 and add it to 2 mL of the mixed fishy substance solution, seal it, and place it in a magnetic heating stirrer. Stir at a low speed at 40 °C and 100 rpm. After 60 min, centrifuge, take 1 mL of the supernatant, and use solid-phase microextraction-gas chromatography (SPME-GC) to measure the concentration C t of the fishy substances in the filtrate. The adsorption capacity q t (μg / g) of Ca-MOF1 for fishy substances at time t and the adsorption rate Q i are calculated according to the following formulas:

[0042] Adsorption capacity of fishy substances at time t:

[0043] Adsorption rate:

[0044] In the formulas, C0 and C t are the initial concentration of the fishy substance solution and the concentration of the fishy substance in the solution at time t, respectively; v is the volume of the solution; m is the mass of Ca-MOF1; Table 1 shows the equilibrium adsorption capacity and adsorption rate of Ca-MOF1 for five types of fishy substances.

[0045] Table 1

[0046]

[0047] As can be seen from Table 1, Ca-MOF1 has a strong adsorption capacity for aldehydes, dimethyl trisulfide and trimethylamine, and has a strong selective adsorption capacity for dimethyl trisulfide (sulfur-containing substances) (the adsorption rate can reach 97.3%). This may be because Ca-MOF1 has a high specific surface area, and the metal Ca is not fully coordinated, and can form coordination bonds with sulfur-containing functional groups in fishy substances.

[0048] (2) Adsorption energy

[0049] Based on the density functional theory (DFT) of first principles, the adsorption energies of Ca-MOF1 for different fishy substances were calculated using the CASTEP module in Materials Studio software. The formula is as follows:

[0050]

[0051] In the formula, E 吸附剂 is the optimized energy of Ca-MOFs, E 吸附质 is the optimized energy of fishy substances, and E 吸附剂+吸附质 is the energy of Ca-MOF after adsorbing fishy substances.

[0052] In addition, based on the molecular dynamics simulation theory, the kinetic adsorption simulation was carried out using the FORCITE module in Materials Studio software to calculate the adsorption rates of Ca-MOF1 for five types of fishy substances.

[0053] Table 2

[0054]

[0055] As can be seen from Table 2, according to the DFT theory calculation, the maximum adsorption energy is for nonanal (-32.055 kcal / mol), followed by 2-methylisoborneol (-29.216 kcal / mol), and then dimethyl trisulfide (-26.119 kcal / mol). According to the analysis of molecular dynamics simulation and experimental values, the adsorption rate of dimethyl trisulfide is the highest. Since nonanal and 2-methylisoborneol have larger molecules, although their adsorption energies are higher, they cannot be adsorbed in the pores of Ca-MOF, and only surface adsorption exists. The adsorption sites in the pores are occupied by small molecule substances such as dimethyl trisulfide and trimethylamine. Dimethyl trisulfide can be adsorbed both on the surface and in the internal pores. Therefore, the adsorption rate of dimethyl trisulfide is the highest, and Ca-MOF1 can selectively adsorb dimethyl trisulfide.

[0056] To highlight the excellent effects of the technical solution proposed in the present invention compared with the prior art, the following comparative experiments were carried out:

[0057] Comparative Example 1

[0058] Accurately weigh 324 mg of γ-cyclodextrin and 112 mg of potassium hydroxide, dissolve them in 10 mL of ultrapure water (the molar ratio of γ-cyclodextrin to potassium hydroxide is 1:8), place them in a glass tube, then ultrasonicate for 5 min to disperse them evenly, filter through a 0.45 μm aqueous membrane, transfer to a small beaker containing 1 mL of methanol, place the small beaker in a large beaker containing methanol, and allow methanol to slowly diffuse into the solution in the small beaker. After incubating at 50 °C for 6 h, precipitate the crystals with methanol, collect the MOF crystal precipitate by centrifugation at 4000 rpm, wash twice with anhydrous methanol, and dry overnight under vacuum at 45 °C. This is γ-cyclodextrin metal-organic framework (γ-CD-MOF1). (Digital specificity)

[0059] Comparative Example 2

[0060] Accurately weigh 260 mg of γ-cyclodextrin and 256 mg of potassium benzoate, dissolve them in 10 mL of ultrapure water (the molar ratio of γ-cyclodextrin to potassium benzoate is 1:8), place them in a glass tube, then ultrasonicate for 5 min to disperse them evenly, filter through a 0.45 μm aqueous membrane, transfer to a small beaker containing 0.5 mL of methanol, place the small beaker in a large beaker containing methanol, and allow methanol to slowly diffuse into the solution in the small beaker. After incubating at 50 °C for 6 h, precipitate the crystals with methanol, collect the MOF crystal precipitate by centrifugation at 4000 rpm, wash twice with anhydrous methanol, and dry overnight under vacuum at 45 °C. This is γ-cyclodextrin metal-organic framework (γ-CD-MOF2).

[0061] Figure 6 The XRD results of the examples and comparative examples demonstrated that Ca-MOF, γ-CD-MOF1, and γ-CD-MOF2 all had good crystallinity; Figure 7 The FTIR results of the examples and comparative examples both showed characteristic peaks of coordination between organic ligands and metal ions. The XRD and FTIR results indicated that the three crystalline materials could all be successfully synthesized.

[0062] Adsorption experiments were conducted on the characteristic fishy odor substances nonanal, 1-octen-3-ol, dimethyl trisulfide, trimethylamine, and 2-methylisoborneol using Ca-MOF1 in the present invention, γ-cyclodextrin metal-organic framework (γ-CD-MOF1) in Comparative Example 1, and γ-cyclodextrin metal-organic framework (γ-CD-MOF2) in Comparative Example 2, respectively. The adsorption rates of Ca-MOF, γ-CD-MOF1, and γ-CD-MOF2 for different types of fishy odor substances are shown in Table 3.

[0063] Table 3

[0064]

[0065] As can be seen from Table 3, the adsorption rate of Ca-MOF1 for dimethyl trisulfide in the present invention is greater than that of γ-CD-MOF1 and γ-CD-MOF2, and it also has better adsorption effects on nonanal, 1-octen-3-ol, trimethylamine, and 2-methylisoborneol.

[0066] Based on Example 1, the following comparative experiments were carried out:

[0067] Example 2

[0068] Accurately weigh 5 g of fumaric acid and 5 g of calcium carbonate, dissolve them in a methanol and ultrapure water (volume ratio 1:2) solution, and stir magnetically until fully dissolved. Transfer the solution to a polytetrafluoroethylene high-pressure reaction kettle, react at 120 °C for 24 h, cool to room temperature, centrifuge to obtain white crystals, wash with methanol 3 times, and vacuum dry at 60 °C for 4 h to obtain Ca-MOF2. Perform a static adsorption experiment on the obtained Ca-MOF2. Table 4 shows the equilibrium adsorption amounts and adsorption rates of Ca-MOF2 for five types of fishy smell substances.

[0069] Table 4

[0070]

[0071] As can be seen from Table 4, after replacing the calcium salt with calcium carbonate during the preparation of Ca-MOF, the adsorption ability for various fishy smell substances decreases, and the adsorption for sulfur-containing substances is not selective.

[0072] Based on Example 1, change the types of calcium salts, and keep other conditions the same as in Example 1. The comparison results are shown in Table 5.

[0073] Table 5

[0074]

[0075] As can be seen from Table 5, different calcium salts have different effects on the pore structure of Ca-MOF. Using calcium acetate as the calcium salt, the prepared MOF material has strong adsorption abilities for nonanal and dimethyl trisulfide; using calcium carbonate as the calcium salt, the prepared MOF material has strong adsorption abilities for trimethylamine and 2-methylisoborneol, but does not have the ability of selective adsorption. This may be because the MOF material formed by calcium carbonate has larger pores, enhancing the adsorption abilities for small molecule trimethylamine and larger molecule 2-methylisoborneol, thereby reducing the adsorption for other molecules; using calcium chloride as the calcium salt, the prepared MOF material has strong adsorption ability for 1-octen-3-ol; using calcium nitrate as the calcium salt, the prepared MOF material has weak adsorption abilities for various fishy smell substances, probably because the self-assembled structure of MOF is incomplete and the pore size distribution is uneven.

[0076] Example 3

[0077] Accurately weigh 5 g of fumaric acid and 5 g of calcium acetate, dissolve them in a methanol - ultrapure water (volume ratio 1:2) solution, and stir magnetically until fully dissolved. Transfer the solution to a polytetrafluoroethylene high - pressure reaction kettle, react at 65 °C for 24 h, cool to room temperature, centrifuge to obtain white crystals, wash with methanol 3 times, and dry in vacuum at 65 °C for 4 h to obtain Ca - MOF3. Perform a static adsorption experiment on the obtained Ca - MOF3. Table 6 shows the equilibrium adsorption capacity and adsorption rate of Ca - MOF3 for five types of fishy smell substances.

[0078] Table 6

[0079]

[0080] As can be seen from Table 6, after the reaction temperature in the MOF preparation process changes from 120 °C to 65 °C, the adsorption capacity for nonanal, dimethyl trisulfide, and 2 - methylisoborneol decreases, but the adsorption capacity for 1 - octen - 3 - ol and trimethylamine increases slightly, indicating that the preparation temperature significantly affects the structure of the MOF material and thus affects the adsorption capacity.

[0081] Based on Example 1, change the different preparation reaction temperatures, and keep other conditions the same as in Example 1. The comparison results are shown in Table 7.

[0082] Table 7

[0083]

[0084] As can be seen from Table 7, different reaction temperatures have different effects on the crystal structure of Ca - MOF. The MOF material prepared at 65 °C has a strong adsorption capacity for dimethyl trisulfide and trimethylamine, but is less than that of Example 1. This may be because smaller pore diameters can be formed at this temperature compared to other temperatures, but due to the pore structure and the flexibility of the framework, the adsorption capacity is worse than that of Example 1; the MOF materials prepared at 95 °C and 150 °C have a weak adsorption capacity for various fishy smell substances, indicating that the self - assembled structures of the MOF formed at these two temperatures are incomplete and the pore size distribution is uneven.

[0085] Example 4

[0086] Accurately weigh 5 g of fumaric acid and 5 g of calcium acetate, dissolve them in a methanol (60 mL) solution, and stir magnetically until fully dissolved. Transfer the solution to a polytetrafluoroethylene high - pressure reaction kettle, react at 120 °C for 24 h, cool to room temperature, centrifuge to obtain white crystals, wash with methanol 3 times, and dry in vacuum at 60 °C for 4 h to obtain Ca - MOF4. Perform a static adsorption experiment on the obtained Ca - MOF4. Table 8 shows the equilibrium adsorption capacity and adsorption rate of Ca - MOF4 for five types of fishy smell substances.

[0087] Table 8

[0088]

[0089] As can be seen from Table 8, different ratios of the reaction solvent in the MOF preparation process also affect the structure. Using methanol as the reaction solvent, the prepared MOF material has a relatively high adsorption capacity for 1-octene-3-ol, indicating that different ratios of the solvent also affect the structure of the MOF material, thereby affecting the adsorption capacity.

[0090] Based on Example 1, the ratio of the solvent to water was changed, and other conditions were the same as in Example 1. The comparison results are shown in Table 9.

[0091] Table 9

[0092]

[0093] As can be seen from Table 9, different ratios of the solvent also have different effects on the structure of Ca-MOF. Using methanol or ethanol as the reaction solvent, the prepared MOF material not only adsorbs a large amount of trimethylamine but also has a strong adsorption capacity for 1-octene-3-ol; using pure water or ethanol-water (v:v = 1:2) as the reaction solvent, the prepared MOF material has a weak adsorption capacity for fishy smell substances, possibly because calcium acetate has a weak solubility in ethanol-water, greatly affecting the formation process of MOF self-assembly and thus affecting the structure of MOF.

[0094] Comparing Examples 2-4 and Tables 4-9 shows that the type of calcium salt, reaction temperature, and solvent ratio all affect the structure of Ca-MOF, thereby affecting the adsorption capacity for five different types of fishy smell substances. The adsorption rate of Ca-MOF1 prepared in Example 1 of the present invention for dimethyl trisulfide is much greater than that of Examples 2, 3, and 4, and has obvious selectivity, indicating that Ca-MOF1 has a selective adsorption effect on sulfur-containing fishy smell substances.

[0095] Example 5

[0096] Based on Example 1 and Comparative Example 1, a composite hybrid supramolecular MOF material can be constructed by the method of nucleation kinetics-guided growth. 3 g of γ-cyclodextrin and 1 g of potassium hydroxide were dissolved in 30 mL of ultrapure water, placed in a glass tube, and then ultrasonicated for 5 min to make it evenly dispersed. After passing through a 0.45 μm water-based membrane, it was transferred to a small beaker containing 10 mL of methanol. 1 g of Ca-MOF1 obtained in Example 1 was added. The small beaker was placed in a large beaker containing methanol, and methanol was slowly diffused into the solution of the small beaker. After incubating at 50 °C for 6 h, the crystals were precipitated with methanol, and the MOF crystal precipitate was collected by centrifugation at 4000 rpm, washed twice with anhydrous methanol, and dried overnight under vacuum at 55 °C to obtain the composite hybrid supramolecular MOF. The obtained composite hybrid supramolecular MOF was subjected to a static adsorption experiment, and Table 10 shows the equilibrium adsorption amounts and adsorption rates for five types of fishy smell substances.

[0097] Table 10

[0098]

[0099] As can be seen from Table 10, the composite hybrid supramolecular MOF can efficiently adsorb five kinds of fishy substances. This may be due to the microporous, mesoporous and macroporous structures of this material, which greatly expands the application of MOF materials in the field of odor adsorption.

[0100] Example 6

[0101] Add 0.5 M ammonium bicarbonate or ammonium carbonate to 50 mL of saturated NaCl solution, stir to dissolve, add 1 M fumaric acid at room temperature, and centrifuge and dry to produce ammonium fumarate. Accurately weigh 5 g of ammonium fumarate, 5 g of fumaric acid and 10 g of calcium acetate, dissolve them in a methanol and ultrapure water (volume ratio 1:2) solution, and stir magnetically until fully dissolved. Transfer the solution to a polytetrafluoroethylene autoclave, react at 120 °C for 24 h, cool to room temperature, centrifuge to obtain white crystals, wash with methanol 3 times, and dry in vacuum at 60 °C for 4 h to obtain the modified Ca-MOF5. Perform a static adsorption experiment on the obtained Ca-MOF5. Table 11 shows the equilibrium adsorption capacity and adsorption rate of Ca-MOF5 for five types of fishy substances.

[0102] Table 11

[0103]

[0104] As can be seen from Table 11, the adsorption capacity of Ca-MOF5 for sulfur-containing substances is significantly affected. Since trimethylamine has a low boiling point, compared with 40 °C, the adsorption capacity of Ca-MOF1 for trimethylamine is stronger at 25 °C. However, after the treatment in Example 6, its adsorption rate is not significantly improved, but the adsorption rate of dimethyl trisulfide is increased. This may be because the trimethylamine molecule is small and not easily retained in the MOF pores. Since the polarity of the modified MOF material is enhanced, more polar adsorption sites can be provided, and the flexibility of the MOF pores is compatible with the pore size and dimethyl trisulfide. Therefore, more dimethyl trisulfide molecules are retained in the pores, indicating that the treatment in Example 6 can improve the adsorption capacity for sulfur-containing substances. Ammonium bicarbonate is not easily affected by the environment or reaction conditions, which helps to maintain the stability of the reaction during synthesis, and the conditions are mild. The decomposition of ammonium bicarbonate releases ammonia and carbon dioxide, which is beneficial to avoiding damage to the MOF structure.

[0105] Example 7

[0106] Dissolve 0.5 M ammonium bicarbonate or ammonium carbonate, 1.5 M fumaric acid, and 2 M calcium acetate in 50 mL of saturated NaCl solution, and then add it to methanol and ultrapure water (volume ratio 1:2), and stir magnetically until fully dissolved. Transfer the solution to a polytetrafluoroethylene autoclave, react at 120 °C for 24 h, cool to room temperature, centrifuge to obtain white crystals, wash with methanol 3 times, and dry in vacuum at 60 °C for 4 h to obtain functionalized Ca-MOF6 prepared by the direct method. Conduct a static adsorption experiment on the obtained Ca-MOF6. Table 12 shows the equilibrium adsorption amounts and adsorption rates of Ca-MOF6 for five types of fishy substances.

[0107] Table 12

[0108]

[0109] As can be seen from Table 12, Ca-MOF modified directly with ammonium bicarbonate or ammonium carbonate has a strong adsorption capacity for sulfur-containing substances, but has little effect on nitrogen-containing substances, which can further verify the conclusion of Example 6. And through the treatment of Examples 6-7, the applicable range of the adsorbent can be broadened.

[0110] As described above, it is only used to help understand the method and its core essence of the present invention, but the protection scope of the present invention is not limited thereto. For those of ordinary skill in the art in the technical field disclosed by the present invention, any equivalent replacement or change made according to the technical solution and inventive concept of the present invention should be covered within the protection scope of the present invention. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A preparation method of a calcium-based metal-organic framework for selectively adsorbing fishy smell substances, characterized in that The method includes the following steps: S1. Dissolve an organic acid and a calcium salt in an aqueous solution containing methanol. The organic acid is fumaric acid, the calcium salt is calcium acetate, the volume ratio of methanol to water is 1:2, and the molar ratio of the organic acid to the calcium salt is 1:(1 - 5); S2. Transfer the fully dissolved solution to a high-pressure reactor for a high-temperature reaction at 120 °C for 6 - 72 h, and then cool it to room temperature; S3. Centrifuge, wash with alcohol, and dry the cooled solution to obtain Ca-MOF crystals.

2. The preparation method of the calcium-based metal-organic framework for selectively adsorbing fishy smell substances according to claim 1, characterized in that, In S1, the organic acid is modified with an ammonium salt before use. The ammonium salt is one or a combination of ammonium bicarbonate, ammonium carbonate, ammonium chloride, ammonium phosphate, and ammonium hydrogen phosphate. The modification method is to dissolve the ammonium salt and the organic acid in a saturated NaCl solution, and the molar ratio of the ammonium salt to the organic acid is 1:(1 - 5). After generating the organic acid monoamine salt, it is dissolved in an aqueous solution containing methanol together with the calcium salt.

3. The preparation method of the calcium-based metal-organic framework for selectively adsorbing fishy smell substances according to claim 1, wherein, In S1, an ammonium salt is also added to the organic acid and the calcium salt. The ammonium salt is one or a combination of ammonium bicarbonate, ammonium carbonate, ammonium chloride, ammonium phosphate, and ammonium hydrogen phosphate. The molar ratio of the ammonium salt, the organic acid, and the calcium salt is 1:(1 - 5):(1 - 5).

4. The preparation method of the calcium-based metal-organic framework for selectively adsorbing fishy smell substances according to claim 1, characterized in that, In S3, the alcohol washing is carried out by washing with ethanol or methanol 1 - 5 times, and the drying conditions are: vacuum drying at 20 - 100 °C for 1 - 24 h, and the pressure is -0.01 - -0.1 MPa.

5. A preparation method of a calcium-based metal-organic framework for selectively adsorbing fishy odor substances according to any one of claims 1-4, characterized in that, The obtained calcium-based metal-organic framework participates in the preparation process of the γ-cyclodextrin metal-organic framework. The composite supramolecular MOF is prepared by the method of nucleation kinetics-guided growth and then used for adsorption.

6. Use of a calcium-based metal-organic framework having selective adsorption of fishy smell substances obtained by the preparation method according to any one of claims 1-4, characterized in that, The calcium-based metal-organic framework is used for adsorbing fishy smell substances, and the fishy smell substances include dimethyl trisulfide, nonanal, 1-octen-3-ol, trimethylamine, or 2-methylisoborneol.

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