A Mo-doped multi-metal MOFs catalyst and its preparation method and application

Abstract

The present invention belongs to the technical field of high value-added biomass, and specifically relates to a Mo-doped multi-metal MOFs catalyst, a preparation method thereof, and an application thereof. The preparation method of the Mo-doped multi-metal MOFs catalyst comprises the following steps: dissolving a basic ligand, a molybdenum salt, and an aluminum salt in a solvent to obtain a mixed solution; heating and centrifuging the mixed solution to obtain a solid substrate; and washing and drying the solid substrate. The present invention successfully prepares a Mo-doped multi-metal Al MOFs catalyst by utilizing the thermal stability of the metal Al structure and the alkaline environment provided by the amino group introduced by 2-aminoterephthalic acid, and realizes efficient thermal catalytic isomerization of glucose to synthesize mannose and fructose, as well as catalytic epimerization of fructose to synthesize psicose, providing a new synthesis route for the efficient catalytic synthesis of high-value monosaccharides including fructose, mannose, and psicose using glucose as a raw material.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-value biomass, and specifically relates to a Mo-doped multi-metal MOFs catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] The multi-stage isomerization of biomass-derived glucose can synthesize a variety of value-added monosaccharides, such as fructose, mannose, and psicose. These high-value monosaccharides are precursors for a variety of pharmaceuticals and high-value-added chemicals. The isomerization of glucose to fructose is considered a key intermediate step in the production of biofuels and platform chemicals. Because fructose readily converts to furanose structures, the catalytic conversion of fructose to 5-hydroxymethylfurfural is generally easier than glucose, resulting in higher product selectivity. Fructose can also be converted into levorotatory propionic acid (LA) and 2,5-furancarboxylic acid (FDCA), important precursors for the production of plastics, green solvents, lubricants, and biofuels. Mannose, a naturally occurring aldohexose, plays an important role in the design of antiviral drugs, low-calorie sweeteners, and anti-inflammatory agents, and has industrial significance for the production of mannitol. D-psicose is a rare monosaccharide with considerable industrial value, particularly as a low-calorie sweetener in the food industry. D-psicose, the C3 exopolymer of D-fructose, possesses nutritional properties similar to those of sucrose, but offers additional health benefits, such as hypoglycemic effects, anti-inflammatory effects, neuroprotection, and glucose suppression. The isomerization of monosaccharides such as glucose and fructose is typically achieved through enzymatic hydrolysis, but this method requires stringent raw material quality and catalytic conditions. Therefore, the research focused on the chemical synthesis of solid catalysts for the high-value conversion of monosaccharides.

[0003] MOFs are highly porous materials composed of metal clusters or ions linked to organic ligands through covalent bonds. Due to their exceptional properties, they are widely used in a variety of fields, including catalysis, gas storage and separation, sensors, biomedicine, energy, and water remediation. Multimetallic MOF catalysts (abbreviated as multimetallic catalysts) can be categorized as metal-site catalysis, organic ligand catalysis, and MOF-supported catalyst catalysis. Multimetallic organic framework catalytic materials, with their advantages such as more metal active sites and unique structural tunability, have become a hot topic in catalysis research.

[0004] Patent application CN109721631 discloses a method for preparing fructose from glucose through selective isomerization. This method utilizes supported and unsupported catalysts to catalyze the isomerization of glucose to produce fructose. While the fructose yield and selectivity are relatively high, the catalysts require a long time, have a low catalytic efficiency, and are unable to catalyze the isomerization of fructose to produce psicose. Summary of the Invention

[0005] The present invention aims to provide a Mo-doped multi-metal MOFs catalyst. The preparation method of the Mo-doped multi-metal MOFs catalyst is simple, and the catalyst can efficiently thermally catalyze the isomerization of glucose to mannose and fructose, and catalyze the epimerization of fructose to picose.

[0006] In order to achieve the above objectives, the technical solution adopted by the present invention is: a method for preparing a Mo-doped multi-metal MOFs catalyst, comprising the following steps:

[0007] 1) dissolving a basic ligand, a molybdenum salt, and an aluminum salt in a solvent to obtain a mixed solution;

[0008] 2) heating and centrifuging the mixed solution to obtain a solid substrate;

[0009] 3) washing and drying the solid substrate.

[0010] Furthermore, the mass ratio of the basic ligand, molybdenum salt and aluminum salt is 1.1-1.2:0.8-1.0:1.5-1.6; and the mass of the molybdenum salt in every 1 mL of solvent is 0.008-0.01 g.

[0011] Furthermore, in step 2), the mixed solution is heated at a temperature of 120 to 140° C. for a heating time of 12 to 72 hours.

[0012] Furthermore, the solvent is N,N-dimethylformamide.

[0013] Furthermore, the molybdenum salt is ammonium molybdate tetrahydrate, the aluminum salt is aluminum chloride hexahydrate; and the basic ligand is 2-aminoterephthalic acid.

[0014] Furthermore, in step 3), the solid substrate is washed alternately with water or ethanol 3 to 4 times; and the drying temperature is 40 to 90°C.

[0015] Furthermore, the centrifugal speed in step 2) is 10,000 to 12,000 r / min.

[0016] A Mo-doped multi-metal MOFs catalyst is prepared by adopting the above-mentioned preparation method of the Mo-doped multi-metal MOFs catalyst.

[0017] An application of a Mo-doped multi-metal MOFs catalyst, wherein the MOFs catalyst is added to an aqueous solution of glucose, and heated to catalyze glucose isomerization to obtain mannose, fructose, and psicose.

[0018] Furthermore, the concentration of the glucose aqueous solution is 8 to 10 g / L; the added mass of the MOFs catalyst is 0.01 to 0.0125 g per mL of glucose aqueous solution; and the temperature of the heating catalysis is 100 to 130°C.

[0019] Beneficial effects of the present invention:

[0020] The present invention successfully prepared a Mo-doped multi-metallic Al MOFs catalyst by utilizing the thermal stability of the metallic Al structure and the alkaline environment provided by the amino group introduced by 2-aminoterephthalic acid. It also achieved efficient thermal catalytic isomerization of glucose to synthesize mannose and fructose, and catalytic epimerization of fructose to synthesize picose, providing a new synthetic route for the efficient catalytic synthesis of high-value monosaccharides including fructose, mannose and picose using glucose as raw material.

[0021] Metal-organic framework (MOFs) materials that exhibit high stability and high specific surface area in hydrothermal reactions are ideal catalysts. The present invention uses metal Al and 2-aminoterephthalic acid to form the basic MOF framework, and uses aluminum chloride hexahydrate and ammonium molybdate tetrahydrate to provide aluminum and molybdenum bimetallic catalytic active sites, so that the prepared MOFs catalyst has unique structural tunability. The MOFs catalyst can catalyze the isomerization of glucose to produce mannose and fructose, and can also catalyze the isomerization of fructose to produce psicose.

[0022] The present invention develops a Mo-doped multi-metal MOFs catalyst through a solvothermal method, and applies the MOFs catalyst to the synthesis of high-value monosaccharides. When using the Mo-doped multi-metal MOFs catalyst to catalyze the isomerization of glucose to produce mannose and fructose, and to catalyze the isomerization of fructose to produce psicose, water is used as a green reaction medium, and no other organic solvents are introduced.

[0023] The Mo-doped multi-metal MOFs catalyst of the present invention, under optimal conditions, can isomerize glucose to obtain a combined yield of 50.77% of mannose and fructose, and a combined selectivity of 94.61% for mannose and fructose. Under reaction conditions of 120°C for 15 minutes, the MOFs catalyst catalyzes glucose to achieve a mannose yield of 32.85%, a fructose yield of 8.04%, and a mannose selectivity of 79.35%. Under reaction conditions of 120°C for 60 minutes, the MOFs catalyst catalyzes the isomerization of fructose to produce 7.18% of allulose. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is the scanning electron microscope image of NH2-MIL-101(Al);

[0025] Figure 2 This is a scanning electron microscope image of the Mo-doped multi-metal MOFs catalyst in Example 3;

[0026] Figure 3 This is the XPS analysis chart of the Mo-doped multi-metal MOFs catalyst in Example 3 before and after catalysis at 120°C for 30 min (C 1s);

[0027] Figure 4 This is the XPS analysis diagram of the Mo-doped multi-metal MOFs catalyst in Example 3 before and after catalysis at 120°C for 30 minutes (Mo 3d);

[0028] Figure 5 The XPS analysis chart (N 1s) of the Mo-doped multi-metal MOFs catalyst before and after catalysis at 120°C for 30 min in Example 3;

[0029] Figure 6 The XPS analysis chart (Al 2p) of the Mo-doped multi-metal MOFs catalyst before and after catalysis at 120°C for 30 min in Example 3;

[0030] Figure 7 FTIR spectra of the Mo-doped multi-metal MOFs catalyst in Example 3 before and after catalysis at 120°C for 30 min and NH2-MIL-101(Al);

[0031] Figure 8 TG spectrum of Mo-doped multi-metal MOFs catalyst in Example 3;

[0032] Figure 9 This is the nitrogen adsorption and desorption diagram of the Mo-doped multi-metal MOFs catalyst in Example 3;

[0033] Figure 10 This is a graph showing the catalytic efficiency of glucose catalyzed by the Mo-doped multi-metal MOFs catalyst at 120°C and different reaction times in Example 3;

[0034] Figure 11 The catalytic efficiency of Mo-doped multi-metal MOFs catalyst for glucose conversion at different catalytic temperatures in 30 min in Example 3 is shown;

[0035] Figure 12 This is a graph showing the catalytic efficiency of fructose catalyzed by the Mo-doped multi-metal MOFs catalyst at 120°C and different reaction times in Example 3;

[0036] Figure 13 The catalytic efficiency of fructose catalyzed by the Mo-doped multi-metal MOFs catalyst in Example 3 at different catalytic temperatures in 60 minutes is shown;

[0037] Figure 14The catalytic efficiency of the Mo-doped multi-metal MOFs catalyst in Example 3 for glucose at 120°C for 30 min (repeated four times);

[0038] Figure 15 This is a diagram showing the catalytic efficiency of fructose catalyzed by the Mo-doped multi-metal MOFs catalyst in Example 3 at 120°C for 60 min (repeated four times). DETAILED DESCRIPTION

[0039] The freeze dryer used in the present invention is an oil bath pot from Zhengzhou Huate Instrument Equipment Co., Ltd., model ZNCL-GS, the X-ray photoelectron spectrometer is from Thermo Fisher Nexsa of the United States, and the scanning electron microscope is from Hitachi Regulus 8230 of Japan.

[0040] The present invention will be further described below with reference to the embodiments of the present invention and the accompanying drawings.

[0041] Example 1

[0042] The preparation method of the Mo-doped multi-metal MOFs catalyst of this embodiment comprises the following steps:

[0043] 1. Dissolve 1.1 g of 2-aminoterephthalic acid, 0.80 g of ammonium molybdate tetrahydrate, and 1.5 g of aluminum chloride hexahydrate in 90 mL of N,N-dimethylformamide, and stir at 600 rpm for 1 h with magnetic stirring to obtain a mixed solution.

[0044] 2. The mixed solution was added to a microreactor lined with polytetrafluoroethylene, heated at 130°C in a vacuum drying oven for 72 hours, and centrifuged at a speed of 10,000 r / min to retain the solid substrate.

[0045] 3. The solid substrate was washed once with water and once with anhydrous ethanol, centrifuged at 10,000 r / min, washed alternately with water and anhydrous ethanol three times, and then dried in a vacuum drying oven at 40°C to obtain the obtained MOFs catalyst of 1.6 to 1.7 g.

[0046] 4 mL of 9 g / L glucose aqueous solution was placed in a 10 mL microreactor lined with polytetrafluoroethylene, 0.05 g of MOFs catalyst was added to the glucose aqueous solution, and the microreactor was placed in an oil bath at 120°C for heating to catalyze the isomerization of glucose to produce mannose and fructose, and fructose was isomerized to produce allulose.

[0047] Example 2

[0048] The preparation method of the Mo-doped multi-metal MOFs catalyst of this embodiment comprises the following steps:

[0049] 1. Dissolve 1.15 g of 2-aminoterephthalic acid, 0.9 g of ammonium molybdate tetrahydrate, and 1.55 g of aluminum chloride hexahydrate in 90 mL of N,N-dimethylformamide, and stir at 600 rpm for 1 h with magnetic stirring to obtain a mixed solution.

[0050] 2. The mixed solution was added to a microreactor lined with polytetrafluoroethylene, heated in a vacuum drying oven at 130°C for 72 hours, and centrifuged at a speed of 10,000 r / min to retain the solid substrate.

[0051] 3. The solid substrate was washed once with water and once with anhydrous ethanol, centrifuged at 11000 r / min, washed alternately with water and anhydrous ethanol three times, and then dried in a vacuum drying oven at 65°C to obtain the obtained MOFs catalyst of 1.6 to 1.7 g.

[0052] 4 mL of a 10 g / L glucose aqueous solution was placed in a 10 mL microreactor lined with polytetrafluoroethylene, 0.05 g of MOFs catalyst was added to the glucose aqueous solution, and the microreactor was placed in an oil bath at 120°C to heat and catalyze the isomerization of glucose to obtain mannose and fructose.

[0053] Example 3

[0054] The preparation method of the Mo-doped multi-metal MOFs catalyst of this embodiment comprises the following steps:

[0055] 1. Dissolve 1.2 g of 2-aminoterephthalic acid, 1.2 g of ammonium molybdate tetrahydrate, and 1.6 g of aluminum chloride hexahydrate in 90 mL of N,N-dimethylformamide, and stir at 600 rpm for 1 h with magnetic stirring to obtain a mixed solution.

[0056] 2. The mixed solution was added to a microreactor lined with polytetrafluoroethylene, heated at 130°C in a vacuum drying oven for 72 hours, and centrifuged at a speed of 10,000 r / min to retain the solid substrate.

[0057] 3. The solid substrate was washed once with water and once with anhydrous ethanol, centrifuged at 12000 r / min, washed alternately with water and anhydrous ethanol three times, and dried in a vacuum drying oven at 90°C to obtain the obtained MOFs catalyst of 1.6 to 1.7 g.

[0058] 4 mL of a 10 g / L glucose aqueous solution was placed in a 10 mL microreactor lined with polytetrafluoroethylene, 0.05 g of MOFs catalyst was added to the glucose aqueous solution, and the microreactor was placed in an oil bath at 120°C to heat and catalyze the isomerization of glucose to obtain mannose and fructose.

[0059] The scanning electron microscope image of the Mo-doped multi-metal MOFs catalyst prepared in this example is as follows: Figure 2 As shown, Figure 1 This is the scanning electron microscope image of NH2-MIL-101(Al). Figure 1 It can be seen that the whole structure is strip-shaped and almost all aggregated together, with a length of about 500 nm, which is consistent with the overall structure of NH2-MIL-101(Al); Figure 2 The 500nm scanning electron microscope image of the Mo-doped multi-metal MOFs catalyst prepared in this example shows that the long strips are about 500nm long, among which small particles of about 100nm appear. This is caused by the doping of metallic Mo, indicating that Mo is successfully embedded in NH2-MIL-101(Al), and NH2-MIL-101(Al) helps to enhance its stability.

[0060] The XPS pattern of the Mo-doped multi-metal MOFs catalyst prepared in this example is shown in FIG. Figure 3 、 Figure 4 、 Figure 5 、 Figure 6 shown. Figure 3 The peak of C1s element, 284.8eV corresponds to the indeterminate CC carbon-hydrogen hybrid, 286.5eV corresponds to sp 3 CN coordination hybridization, 288.9eV corresponds to sp 2 C=N hybridization, which is the basic skeleton structure of MOFs materials; Figure 4 The Mo 3d spectrum can be divided into three groups of peaks, of which 232.6eV and 235.8eV correspond to Mo 6+ The peak of Mo 6+ The peaks at 236.5 eV and 237.4 eV, which occupy the majority, are formed by the coupling of Mo and O with N; Figure 5 The peaks are the element peak of N1s, the N=C and NH hybrid peaks at 399.6eV and 401.5eV, and a new peak belonging to N-Mo is formed at 397.6eV, which is the result of strong electronic coupling between atomic Mo and N; Figure 6 The element peak of Al 2p is generated due to the presence of aluminum oxide or aluminum hydroxide. Figure 3 , Figure 4 , Figure 5 as well as Figure 6 It can be seen that the intensity of the four element peaks of C, N, Al, and Mo in the Mo-doped multi-metal MOFs catalyst prepared in this example does not change much before and after the reaction, proving that the element peaks do not change much before and after the reaction.

[0061] The FT-IR image of the Mo-doped multi-metal MOFs catalyst prepared in this example is shown in FIG. Figure 7The NH2-MIL-101(Al) and Mo-doped multimetallic MOFs catalysts showed the following changes before and after the reaction at about 750-1000, 1250-1750 and 3000-3500 cm -1 There are obvious peaks at 3000-3500cm -1 The absorption peaks between them correspond to the vibration peaks of -COOH and NH in carbonyl and amino groups. Compared with the single large peak of NH2-MIL-101(Al), the existence of two vibration peaks can be clearly seen, 1250-1750cm -1 The five-finger peaks generated by the benzene ring and the stretching peaks of CN in the carbon group and amino group are located at 750-1000 cm -1 Medium, 1000cm -1 There is an N-Mo and Mo=O vibration peak at , which proves the successful doping of Mo.

[0062] The TG diagram of the Mo-doped multi-metal MOFs catalyst prepared in this example is shown in FIG. Figure 8 As shown. The decomposition process of NH2-Mo-MIL-101(Al) mainly consists of three stages. The first stage is in the range of 150-300℃. This weight loss stage is mainly caused by the volatilization of physically bound water in the material structure or organic solvent molecules in its pores and the decomposition of -NH2 in the material. The mass loss caused by volatilization in the form of NH3 accounts for 17.41%; the second stage is in the range of 300-450℃. The weight loss is very slow. After 450℃, there is almost no -NH2. During this period, the main structure of the material begins to decompose; the third stage is in the temperature range of 450-600℃. At this time, the carbon skeleton of NH2-Mo-MIL-101(Al) has decomposed and volatilized in the form of carbon oxides such as CO and CO2. The remaining structure may be in the form of composite metal oxides.

[0063] The nitrogen adsorption and desorption diagram of the Mo-doped multi-metal MOFs catalyst prepared in this example is shown in FIG. Figure 9 As shown in the figure, the two materials clearly show type IV adsorption curves, which are consistent with the adsorption trend of the mesoporous structure. In the relative pressure P / P0=0~0.05 stage, the adsorption amount of NH2-Mo-MIL-101(Al) gas increases rapidly, mainly due to the rapid adsorption of N2 in the smaller pore paths. In the P / P0=0.05~0.10 stage, the rise of the adsorption isotherm of Mo-doped multi-metal MOFs catalyst slows down, indicating that there are larger sizes that need to be filled with gas. Then, with the increase of P / P0, until P / P0=0.9, the adsorption isotherm of Mo-doped multi-metal MOFs catalyst is almost horizontal, indicating that the gas adsorption is basically fully covered.

[0064] The catalytic efficiency of Mo-doped multi-metal MOFs catalyst prepared in this example at 120°C and different catalytic reaction times for glucose is shown in the figure below. Figure 10 As shown in the figure, the catalytic efficiency of glucose catalysis at different catalytic reaction temperatures in 30 minutes is as follows Figure 11 As shown. Figure 10 and Figure 11 It can be seen from the data that when the reaction temperature is 100℃ and the reaction time is 30min, only mannose is produced by isomerization, and the mannose yield is 2.62%. With the increase of temperature, at 120℃ and 15min, the mannose yield generated by isomerization is the highest, reaching 32.85%, the fructose yield is 8.04%, and the mannose selectivity reaches 79.35%. At 120℃ and 30min, the glucose conversion rate and the total value of mannose and fructose generated by isomerization reach the highest, with the fructose yield reaching 20.47%, the mannose yield reaching 30.30%, and the comprehensive selectivity of fructose and mannose being 94.61%. As the temperature and time continue to increase, because monosaccharides are easily degraded in high-temperature aqueous solutions, at 130℃ and 30min and 120℃ and 60min, the glucose, mannose, and fructose all show a significant decrease.

[0065] The catalytic efficiency of fructose catalysis of the Mo-doped multi-metal MOFs catalyst prepared in this example at 120°C and different catalytic reaction times is shown in the figure below. Figure 12 As shown in the figure, the catalytic efficiency of fructose catalysis at different catalytic reaction temperatures in 60 minutes is as follows Figure 13 As shown. Figure 12 and Figure 13 As can be seen in the results, the MOFs catalyst not only produces psicose but also small amounts of glucose and mannose when catalyzing fructose. At 120°C for 1 hour, the highest psicose yield is 7.18%, but the selectivity for fructose is very low, at only 37.98%. Fructose is unstable and readily produces glycosides, organic acids, and humus in alkaline and hydrothermal environments.

[0066] The reproducibility of the Mo-doped multimetallic MOFs catalyst prepared in this example in catalyzing glucose and fructose under optimal conditions is shown in the figure below. Figure 14 and Figure 15 shown. Figure 14 The Mo-doped multi-metallic MOFs catalyst prepared in this example was reused four times under the following conditions: a catalytic reaction temperature of 120°C, a reaction time of 30 minutes, a glucose aqueous solution concentration of 10 g / L, a volume of 4 ml, and a catalyst dosage of 0.05 g. The yields of fructose and mannose remained at 95% of the initial yields after four repetitions, demonstrating that the Mo-doped multi-metallic MOFs catalyst can be reused after repeated washing and drying. Figure 15The Mo-doped multi-metallic MOFs catalyst prepared in this example was reused four times under the following conditions: a catalytic reaction temperature of 120°C, a reaction time of 1 hour, a glucose aqueous solution concentration of 10 g / L, a volume of 4 ml, and a catalyst dosage of 0.05 g. The psicose yield remained at 85% of the initial yield after four repetitions, demonstrating that the Mo-doped multi-metallic MOFs catalyst can be repeatedly washed and dried for reuse. The catalyst in this example was washed with water and ethanol and then dried.

[0067] With glucose as the substrate, the Mo-doped multi-metal MOFs catalyst prepared in this example was used to catalyze the isomerization of glucose into mannose and fructose. The catalytic results are shown in Table 1.

[0068] Table 1 Catalytic selectivity of Mo-doped multimetallic MOFs catalysts with glucose as substrate

[0069]

[0070] As can be seen in Table 1, when the catalytic temperature is above 120°C, the combined selectivity of fructose and mannose decreases significantly, indicating that the high temperature causes dehydration of mannose and fructose, resulting in the formation of impurities such as humus. At catalyst temperatures of 110°C and 120°C, the combined selectivity of fructose and mannose exceeds 90%.

[0071] Example 4

[0072] The preparation method of the Mo-doped multi-metal MOFs catalyst of this embodiment comprises the following steps:

[0073] 1. Dissolve 1g of 2-aminoterephthalic acid, 0.9g of ammonium molybdate tetrahydrate and 1.6g of aluminum chloride hexahydrate in 90mL of N,N-dimethylformamide, stir magnetically at 600r / min for 1h to obtain a mixed solution.

[0074] 2. The mixed solution was added to a microreactor lined with polytetrafluoroethylene, heated at 130°C in a vacuum drying oven for 72 hours, and centrifuged at a speed of 10,000 r / min to retain the solid substrate.

[0075] 3. The solid substrate was washed once with water and once with anhydrous ethanol, centrifuged at 11000 r / min, washed alternately with water and anhydrous ethanol three times, and then dried in a vacuum drying oven at 80°C to obtain the obtained MOFs catalyst of 1.6 to 1.7 g.

[0076] 4 mL of a 10 g / L glucose aqueous solution was placed in a 10 mL microreactor lined with polytetrafluoroethylene, 0.05 g of MOFs catalyst was added to the glucose aqueous solution, and the microreactor was placed in an oil bath at 120°C to heat and catalyze the isomerization of glucose to obtain mannose and fructose, and the fructose was isomerized to obtain allulose.

[0077] Using fructose as a substrate, the Mo-doped multi-metal MOFs catalyst prepared in this example was used to catalyze the isomerization of fructose to synthesize psicose. The catalytic results are shown in Table 2.

[0078] Table 2 Catalytic selectivity of Mo-doped multimetallic MOFs catalysts with fructose as substrate

[0079]

[0080] Table 2 shows the catalytic results under the conditions of catalytic temperatures of 100°C, 110°C, 120°C, and 130°C, and catalytic times of 0.5 h and 1 h, respectively. Due to the low stability of fructose, the higher the temperature, the fructose is hydrolyzed first, resulting in a lower yield of psicose.

[0081] Example 5

[0082] The preparation method of the Mo-doped multi-metal MOFs catalyst of this embodiment comprises the following steps:

[0083] 1. Dissolve 1.1 g of 2-aminoterephthalic acid, 0.90 g of ammonium molybdate tetrahydrate, and 1.5 g of aluminum chloride hexahydrate in 90 mL of N,N-dimethylformamide, and stir at 600 rpm for 1 h with magnetic stirring to obtain a mixed solution.

[0084] 2. The mixed solution was added to a microreactor lined with polytetrafluoroethylene, heated in a vacuum drying oven at 140°C for 60 h, and centrifuged at a speed of 10,000 r / min to retain the solid substrate.

[0085] 3. The solid substrate was washed once with water and once with anhydrous ethanol, centrifuged at 10,000 r / min, washed alternately with water and anhydrous ethanol three times, and then dried in a vacuum drying oven at 40°C to obtain the obtained MOFs catalyst of 1.6 to 1.7 g.

[0086] 4 mL of a 10 g / L glucose aqueous solution was placed in a 10 mL microreactor lined with polytetrafluoroethylene, 0.05 g of MOFs catalyst was added to the glucose aqueous solution, and the microreactor was placed in an oil bath at 120°C to heat and catalyze the isomerization of glucose to obtain mannose and fructose.

[0087] Example 6

[0088] The preparation method of the Mo-doped multi-metal MOFs catalyst of this embodiment comprises the following steps:

[0089] 1. Dissolve 1.2 g of 2-aminoterephthalic acid, 0.90 g of ammonium molybdate tetrahydrate, and 1.6 g of aluminum chloride hexahydrate in 90 mL of N,N-dimethylformamide, and stir at 600 rpm for 1 h with magnetic stirring to obtain a mixed solution.

[0090] 2. The mixed solution was added to a microreactor lined with polytetrafluoroethylene, heated at 120°C in a vacuum drying oven for 72 hours, and centrifuged at a speed of 10,000 r / min to retain the solid substrate.

[0091] 3. The solid substrate was washed once with water and once with anhydrous ethanol, centrifuged at 10,000 r / min, washed alternately with water and anhydrous ethanol three times, and then dried in a vacuum drying oven at 40°C to obtain the obtained MOFs catalyst of 1.6 to 1.7 g.

[0092] 4 mL of 8 g / L glucose aqueous solution was placed in a 10 mL microreactor lined with polytetrafluoroethylene, 0.05 g of MOFs catalyst was added to the glucose aqueous solution, and the microreactor was placed in an oil bath at 120°C to heat and catalyze the isomerization of glucose to obtain mannose and fructose.

Claims

1. A method for preparing a Mo-doped multi-metal MOFs catalyst, characterized in that: The following steps are involved: 1) dissolving a basic ligand, a molybdenum salt, and an aluminum salt in a solvent to obtain a mixed solution; 2) heating and centrifuging the mixed solution to obtain a solid substrate; 3) washing and drying the solid substrate; The mass ratio of the basic ligand, molybdenum salt, and aluminum salt is 1.1-1.2:0.8-1.0:1.5-1.6; the mass of the molybdenum salt in each 1 mL of solvent is 0.008-0.01 g; the temperature of heating the mixed solution in step 2) is 120-140°C and the heating time is 12-72 h; the basic ligand is 2-aminoterephthalic acid; The Mo-doped multi-metal MOFs catalyst is used in catalyzing glucose isomerization to produce fructose, mannose and psicose.

2. The method for preparing a Mo-doped multi-metal MOFs catalyst according to claim 1, wherein: The solvent is N,N-dimethylformamide.

3. The method for preparing Mo-doped multi-metal MOFs catalyst according to claim 1, characterized in that: The molybdenum salt is ammonium molybdate tetrahydrate, and the aluminum salt is aluminum chloride hexahydrate.

4. The method for preparing a Mo-doped multi-metal MOFs catalyst according to claim 1, wherein: In step 3), the solid substrate is washed alternately with water or ethanol for 3 to 4 times; the drying temperature is 40 to 90°C.

5. The method for preparing Mo-doped multi-metal MOFs catalyst according to claim 1, characterized in that: Step 2) The centrifugal speed is 10000-12000 r / min.

6. A Mo-doped multimetallic MOFs catalyst, characterized in that: The catalyst is prepared by the method for preparing the Mo-doped multi-metal MOFs catalyst as claimed in claim 1.

7. Use of the Mo-doped multi-metal MOFs catalyst according to claim 6, characterized in that: The MOFs catalyst is added to an aqueous solution of glucose, and heated to catalyze glucose isomerization to obtain mannose, fructose and psicose.

8. The use of the Mo-doped multi-metal MOFs catalyst according to claim 7, characterized in that: The concentration of the glucose aqueous solution is 8 to 10 g / L; the added mass of the MOFs catalyst is 0.01 to 0.0125 g per mL of the glucose aqueous solution; and the temperature of the heating catalysis is 100 to 130°C.

Images