Catalytic applications of pickering emulsions stabilized by metal-organic framework-based composite materials MOF-74(Cu)@SiO2
Patent Information
- Application Number
- CN202611107549.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-24
- Publication Date
- 2026-10-27
AI Technical Summary
[0004]尽管MOF-74(Cu)具备优良的酸碱双功能催化活性，但难以构筑稳定的皮克灵乳液，严重制约其在两相串联催化中的实际应用
[0019]本发明的MOF-74(Cu)@SiO2稳定的皮克灵乳液中，MOF-74(Cu)中的Cu2+作为路易斯酸为第一步脱羧醛反应提供活性位点；而酚氧原子的碱性位点夺取丙二腈的活泼氢，生成高活性碳负离子催化第二步Knoevenagel缩合反应，从而协同催化一锅串联反应SiO2壳层表面分布着大量水化过程中原位生成的硅羟基，提供酸性活性位点催化脱缩醛反应。同时SiO2包覆结构显著增强材料骨架强度，也让皮克灵乳液体系具备更优异的稳定性能。反应式如下：
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Figure CN122974368A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of catalyst technology, specifically relating to the catalytic application of a Pickering emulsion stabilized by a metal-organic framework composite material MOF-74(Cu)@SiO2. Background Technology
[0002] Traditional catalysis is mostly homogeneous, which generally suffers from problems such as difficult catalyst recovery, significant environmental pollution, and poor cycle stability, making it difficult to meet the development needs of green catalysis and industrial applications. Therefore, the development of high-performance, recyclable heterogeneous solid catalytic materials has become a research hotspot in the field of catalysis. Metal-organic frameworks (MOFs) are porous crystalline materials formed by the coordination self-assembly of metal ions and organic ligands. With their unique advantages such as large specific surface area, tunable pore structure, and abundant active sites, they are widely used in heterogeneous catalysis. Among them, MOF-74(Cu) exhibits excellent bifunctional catalytic properties, and its structure contains a large number of coordinatingly unsaturated Cu atoms. 2+ Lewis acidic sites, along with abundant phenolic oxygen basic sites distributed on the surface of organic ligands, can simultaneously provide acidic activation sites and basic dehydrogenation sites, making them suitable for acid-base synergistic catalytic reactions and possessing great application potential in tandem catalytic systems.
[0003] One-pot tandem reactions and Pickering emulsion catalysis are both novel and highly efficient catalytic technologies that align with modern green chemistry principles. One-pot tandem reactions can complete multiple continuous reaction transformations in a single reaction system, eliminating the complex process of separating and purifying intermediate products, effectively simplifying the operation, reducing energy consumption and reagent loss, and achieving green and efficient reactions. Pickering emulsion catalysis, by replacing traditional organic surfactants with solid particles, can construct a stable micro-reaction interface at the water-oil interface, significantly increasing the contact area between the water and oil phases, optimizing mass transfer efficiency, and improving reaction selectivity. Deacetalization-Knoevenagel tandem reactions are typical acid-base synergistic reactions, highly dependent on the synergistic effect of the catalyst's dual acid-base active sites. Combining the advantages of the Pickering emulsion interface with one-pot tandem reactions can further improve the reaction efficiency and greenness of tandem catalysis.
[0004] Although MOF-74(Cu) possesses excellent bifunctional acid-base catalytic activity, it is difficult to construct stable Pickering emulsions, severely limiting its practical application in two-phase tandem catalysis. Therefore, this invention constructs a MOF-74(Cu)@SiO2 composite material by coating the surface of MOF-74(Cu) with a SiO2 shell. This utilizes the protective effect of silica to enhance the structural stability and interfacial dispersion performance of the material, achieving stable Pickering emulsion construction, while also fully preserving the acid-base bifunctional active centers of MOF-74(Cu), enabling efficient and recyclable one-pot tandem catalysis. Currently, research on using MOF-74(Cu)@SiO2 composite materials to construct Pickering emulsions and applying them to deacetalization-Knoevenagel tandem catalysis is still very limited, making this a significant research opportunity with important innovative value. Summary of the Invention
[0005] The purpose of this invention is to provide a catalyst MOF-74(Cu)@SiO2-stabilized Pickering emulsion with both acid-base bifunctional active sites for efficient catalysis of the Deacetalization-Knoevenagel one-pot reaction.
[0006] The technical solution adopted in this invention is:
[0007] A metal-organic framework composite material MOF-74(Cu)@SiO2, the preparation method of which includes the following steps:
[0008] 1) Disperse Cu(NO3)2 and 2,5-dihydroxyterephthalic acid in a mixed solvent of DMF and methanol, stir evenly, and carry out hydrothermal reaction in a reaction vessel. After the reaction is completed, cool naturally to room temperature, wash with DMF and methanol in sequence, and then dry under vacuum to obtain MOF-74(Cu) powder.
[0009] 2) The MOF-74(Cu) powder prepared in step 1) was dispersed in a mixed solvent of deionized water and anhydrous ethanol. CTAB was added and stirred. After heating to 323 K, ammonia was added. Then, an anhydrous ethanol solution of tetraethyl silicate was slowly added dropwise using a syringe pump while stirring continuously. After the reaction was completed, the powder was centrifuged, washed, and vacuum dried to obtain a solid powder. The solid powder was then dispersed in a hydrochloric acid ethanol solution and stirred to remove CTAB. Finally, the powder was centrifuged, washed, and vacuum dried to obtain an orange MOF-74(Cu)@SiO2 powder.
[0010] Furthermore, in the preparation method of the above-mentioned metal-organic framework composite material MOF-74(Cu)@SiO2, in step 1), the molar ratio of Cu(NO3)2 : 2,5-dihydroxyterephthalic acid = 2 : 1; in the mixed solvent of DMF and methanol, the volume ratio of DMF to methanol is 9 : 1.
[0011] Furthermore, in the preparation method of the above-mentioned metal-organic framework composite material MOF-74(Cu)@SiO2, in step 1), the stirring time is 1 min; the hydrothermal reaction conditions are: 393 K hydrothermal reaction for 24 h.
[0012] Furthermore, in step 2) of the preparation method of the above-mentioned metal-organic framework composite material MOF-74(Cu)@SiO2, the mass ratio of MOF-74(Cu):CTAB:tetraethyl silicate is 0.1:1.250:0.579; and the volume of ammonia water added is 0.5 mL.
[0013] Furthermore, in step 2) of the preparation method of the above-mentioned metal-organic framework composite material MOF-74(Cu)@SiO2, the anhydrous ethanol solution of tetraethyl silicate is prepared by adding 10 mL of anhydrous ethanol and 0.623 mL of tetraethyl silicate to a beaker and mixing them evenly; the concentration of the hydrochloric acid ethanol solution is 1 mol / L, and it is prepared by adding 83.33 mL of anhydrous ethanol and 16.67 mL of hydrochloric acid aqueous solution with a volume ratio of 1:1 to a beaker and mixing them evenly.
[0014] Furthermore, in the preparation method of the above-mentioned metal-organic framework composite material MOF-74(Cu)@SiO2, in step 2), the stirring conditions after adding CTAB are: stirring at 298 K for 1 h; when adding anhydrous ethanol solution of tetraethyl silicate, stirring is continued at 323 K for 6 h; and the stirring condition to remove CTAB is: stirring at 298 K for 24 h.
[0015] A Pickering emulsion stabilized by MOF-74(Cu)@SiO2 based on a metal-organic framework is prepared by the following steps: taking a metal-organic framework composite material MOF-74(Cu)@SiO2 as described in any one of claims 1-6, adding toluene and water, and then sonicating and shaking up and down to obtain a Pickering emulsion stabilized by MOF-74(Cu)@SiO2.
[0016] Furthermore, the preparation method of the above-mentioned metal-organic framework-based composite material MOF-74(Cu)@SiO2 stabilized Pickering emulsion is as follows: MOF-74(Cu)@SiO2: toluene: water = 35 mg : 1.67 mL : 3.33 mL; ultrasonic power is 100 W, ultrasonic time is 5 min, and up-and-down oscillation time is 5 min.
[0017] The above-mentioned application of a metal-organic framework-based composite material MOF-74(Cu)@SiO2 stabilized Pickering emulsion in the catalytic deacetalization-Knoevenagel one-pot reaction is as follows: benzaldehyde dimethyl acetal and the metal-organic framework-based composite material MOF-74(Cu)@SiO2 stabilized Pickering emulsion are reacted at 353 K for 2 h, malononitrile is added, and the reaction is continued for 2 h.
[0018] Furthermore, in the above application, the molar ratio is benzaldehyde dimethyl acetal : malononitrile = 1.0 : 1.5.
[0019] In the MOF-74(Cu)@SiO2 stabilized Pickering emulsion of the present invention, the Cu in MOF-74(Cu) 2+ As a Lewis acid, it provides an active site for the first step of the decarboxylation reaction; while the basic site of the phenolic oxygen atom abstracts the active hydrogen from malononitrile, generating a highly active carbanion to catalyze the second step of the Knoevenagel condensation reaction, thus synergistically catalyzing a one-pot tandem reaction. The SiO2 shell surface has a large number of silanol groups generated in situ during hydration, providing acidic active sites for catalyzing the deacetalization reaction. Simultaneously, the SiO2 coating structure significantly enhances the material's skeletal strength, also giving the Pickering emulsion system superior stability. The reaction formula is as follows:
[0020]
[0021] The beneficial effects of this invention are: this invention uses MOF-74(Cu) as the core component, with Cu as the metal center. 2+As a Lewis acid, it provides an active site for the first step of the decarboxylation reaction; while the basic site of the phenolic oxygen atom abstracts the active hydrogen from malononitrile, generating a highly active carbanion to catalyze the second step of the Knoevenagel condensation reaction, thus synergistically catalyzing a one-pot cascade reaction. This invention constructs a MOF-74(Cu)@SiO2 composite catalyst by coating SiO2 around the core of a MOF. The abundant silanol groups on the surface of the SiO2 shell serve as acidic sites for catalyzing the decarboxylation reaction, significantly improving the structural stability of the material itself and enhancing the stability of the Pickering emulsion system, thus constructing a Pickering emulsion with excellent stability and superior catalytic performance. Dispersing the prepared MOF-74(Cu)@SiO2 powder within the emulsion system can significantly increase the contact area between the reaction substrate and the catalytic material, effectively improving the overall catalytic reaction efficiency. After five cycles of catalytic testing, the catalyst still maintains high catalytic activity, exhibiting good structural stability and recyclability. Overall, MOF-74(Cu)@SiO2 exhibits excellent catalytic performance in the preparation of benzylidene malononitrile derivatives (BMDs) via the deacetalization-Knoevenagel reaction: under the same reaction conditions, the yield of the single MOF74(Cu) catalytic reaction was 72.45% after 3 h, while the yield of the composite MOF74(Cu)@SiO2 reached 92.56%, significantly improving the overall catalytic activity of the material. Attached Figure Description
[0022] Figure 1 This is an optical microscope image of a Pickering emulsion stabilized based on MOF-74(Cu)@SiO2.
[0023] Figure 2 This is the FT-IR image of MOF-74(Cu)@SiO2 prepared in this invention.
[0024] Figure 3 This is the XRD pattern of the MOF-74(Cu)@SiO2 material prepared in this invention.
[0025] Figure 4 This is a SEM image of MOF-74(Cu) prepared in this invention.
[0026] Figure 5 This is a SEM image of MOF-74(Cu)@SiO2 prepared in this invention.
[0027] Figure 6 This is a catalytic activity diagram of five cycles of catalytic reaction of the Pickering emulsion based on MOF-74(Cu)@SiO2 stabilized prepared in this invention. Detailed Implementation
[0028] Example 1: A Pickering emulsion stabilized by MOF-74(Cu)@SiO2 composite material based on a metal-organic framework.
[0029] (I) Preparation method
[0030] 1. Preparation of 1 mol / L hydrochloric acid in ethanol and anhydrous tetraethyl silicate in ethanol
[0031] 1 mol / L hydrochloric acid ethanol solution: Add 83.33 mL of anhydrous ethanol and 16.67 mL of hydrochloric acid aqueous solution with a volume ratio of 1:1 to a beaker, mix well and set aside.
[0032] Anhydrous ethanol solution of tetraethyl silicate: Add 10 mL of anhydrous ethanol and 0.623 mL of tetraethyl silicate to a beaker, mix well and set aside.
[0033] 2. Synthesis of MOF-74(Cu) raw material powder
[0034] Cu(NO3)2 (0.731 g, 3.03 mmol) and 2,5-dihydroxyterephthalic acid (0.299 g, 1.51 mmol) were poured into an 80 mL hydrothermal synthesis reactor. Then, 54 mL of N,N-dimethylformamide (DMF) and 6 mL of methanol were accurately pipetted into the reactor. The mixture was stirred at room temperature for 1 min, and no bubbles were observed in the reactor. The reactor was then placed in an oven at 393 K for 24 h. After the reaction was complete, the mixture was cooled to room temperature, washed three times with DMF and methanol, and then dried in a vacuum drying oven at 353 K for 12 h to obtain MOF-74(Cu) powder.
[0035] 3. Preparation of MOF-74(Cu)@SiO2 composite material
[0036] 100 mg of MOF-74(Cu) powder was accurately weighed and placed in a 250 mL three-necked flask. 100 mL of deionized water and 20 mL of anhydrous ethanol were added sequentially, followed by 1.25 g of cetyltrimethylammonium bromide (CTAB). The mixture was stirred continuously at room temperature for 1 h. After heating to 323 K, 0.5 mL of ammonia water was added dropwise. An anhydrous ethanol solution of tetraethyl silicate was then added dropwise at a low and uniform rate of 2 mL per hour using a syringe pump, with the reaction being stirred continuously for 6 h. The solid material was collected by centrifugation, washed three times with anhydrous ethanol, and then vacuum dried at 353 K for 24 h. The dried powder was immersed in a 1 mol / L hydrochloric acid-ethanol solution and stirred at room temperature for 24 h to remove CTAB. It was then centrifuged, washed again, and dried at a constant temperature to obtain pure MOF-74(Cu)@SiO2 orange powder.
[0037] 4. Preparation of Pickering emulsion stabilized by MOF-74(Cu)@SiO2
[0038] Add 1.67 mL of toluene and 3.33 mL of deionized water to 35 mg of MOF-74(Cu)@SiO2, sonicate at 100 W for 5 min, and then oscillate up and down for 5 min to obtain a Picklerin emulsion stabilized by MOF-74(Cu)@SiO2.
[0039] (II) Testing
[0040] Figure 1 This is an optical microscope image of a Pickering emulsion stabilized by MOF-74(Cu)@SiO2. It can be seen that the Pickering emulsion stabilized by MOF-74(Cu)@SiO2 exhibits a uniform droplet distribution and consistent particle size.
[0041] Figure 2 The image shows the FT-IR spectrum of MOF-74(Cu)@SiO2 material, indicating that the MOF-74(Cu)@SiO2 composite material was successfully synthesized.
[0042] Figure 3 The image shows the XRD pattern of MOF-74(Cu)@SiO2 material, indicating that the material has a well-preserved crystal structure and excellent crystallization performance during the preparation process.
[0043] Figure 4 , Figure 5 The images show SEM images of MOF-74(Cu) and MOF-74(Cu)@SiO2 materials, indicating that the MOF-74(Cu)@SiO2 composite material is intact and has no obvious agglomeration.
[0044] Example 2: Catalytic function of Pickering emulsion stabilized by MOF-74(Cu)@SiO2 material on the deacetalization-Knoevenagel reaction
[0045] Using the Pickering emulsion prepared in Example 1 as a catalytic system, a Deacetalization-Knoevenagel tandem catalytic experiment was carried out.
[0046] (a) Application Method
[0047] The Pickering emulsion based on MOF-74(Cu)@SiO2 stabilized prepared in Example 1 was transferred to a 10 mL three-necked flask, 1.0 mmol benzaldehyde dimethyl acetal was added, and the mixture was heated to 353 K and reacted at a constant temperature for 2 hours. Then, 1.5 mmol malononitrile was added, and the reaction was continued for another 2 hours to generate BMDs. The yield was detected by gas chromatography (GC) throughout the process.
[0048] During the reaction, the catalytic performance of MOF-74(Cu)@SiO2 Pickering emulsion on the one-pot reaction was detected by GC. As the reaction proceeded, the yield of the reaction gradually increased. When the reaction proceeded for 4 hours, the yield of BMDs had reached 99.9%.
[0049] (II) Reuse of Pickering emulsion based on MOF-74(Cu)@SiO2 stabilized
[0050] After the reaction is completed, the reaction mixture is centrifuged and filtered to separate MOF-74(Cu)@SiO2 from the reaction system; the filter cake is washed with anhydrous ethanol, filtered and dried to recover the MOF-74(Cu)@SiO2 material.
[0051] The specific operation of the cyclic experiment is as follows: Pickering emulsion is prepared again using the recovered MOF-74(Cu)@SiO2 material, and Deacetalization-Knoevenagel one-pot reaction is catalyzed.
[0052] Experimental results are as follows Figure 6 As shown in the figure, this is the activity change curve of the five-cycle catalytic reaction of the Pickering emulsion stabilized by MOF-74(Cu)@SiO2. After five cycles, the yield and conversion rate of the reaction were both higher than 95%, indicating that the activity of the catalyst MOF-74(Cu)@SiO2 did not decrease significantly, and the recovered catalyst could still stably form the Pickering emulsion. The results show that MOF-74(Cu)@SiO2 in this Pickering emulsion has excellent recyclability as a catalyst for the Deacetalization-Knoevenagel one-pot reaction.
Claims
1. A metal-organic framework composite material MOF-74(Cu)@SiO2, characterized in that, Its preparation method includes the following steps: 1) Disperse Cu(NO3)2 and 2,5-dihydroxyterephthalic acid in a mixed solvent of DMF and methanol, stir evenly, and carry out hydrothermal reaction in a reaction vessel. After the reaction is completed, cool naturally to room temperature, wash with DMF and methanol in sequence, and then dry under vacuum to obtain MOF-74(Cu) powder. 2) The MOF-74(Cu) powder prepared in step 1) was dispersed in a mixed solvent of deionized water and anhydrous ethanol. CTAB was added and stirred. After heating to 323 K, ammonia was added. Then, an anhydrous ethanol solution of tetraethyl silicate was slowly added dropwise using a syringe pump while stirring continuously. After the reaction was completed, the powder was centrifuged, washed, and vacuum dried to obtain a solid powder. The solid powder was then dispersed in a hydrochloric acid ethanol solution and stirred to remove CTAB. Finally, the powder was centrifuged, washed, and vacuum dried to obtain an orange MOF-74(Cu)@SiO2 powder.
2. The metal-organic framework composite material MOF-74(Cu)@SiO2 according to claim 1, characterized in that, In step 1), the molar ratio of Cu(NO3)2 : 2,5-dihydroxyterephthalic acid is 2 : 1; in the mixed solvent of DMF and methanol, the volume ratio of DMF to methanol is 9 :
1.
3. The metal-organic framework composite material MOF-74(Cu)@SiO2 according to claim 1, characterized in that, In step 1), the stirring time is 1 min; the hydrothermal reaction conditions are: 393 K hydrothermal reaction for 24 h.
4. The metal-organic framework composite material MOF-74(Cu)@SiO2 according to claim 1, characterized in that, In step 2), the mass ratio of MOF-74(Cu):CTAB:tetraethyl silicate is 0.1:1.250:0.579; the volume of ammonia added is 0.5 mL.
5. The metal-organic framework composite material MOF-74(Cu)@SiO2 according to claim 1, characterized in that, In step 2), the anhydrous ethanol solution of tetraethyl silicate is prepared by adding 10 mL of anhydrous ethanol and 0.623 mL of tetraethyl silicate to a beaker and mixing them thoroughly. The concentration of the hydrochloric acid ethanol solution is 1 mol / L, and it is prepared by adding 83.33 mL of anhydrous ethanol and 16.67 mL of hydrochloric acid aqueous solution with a volume ratio of 1:1 to a beaker and mixing them thoroughly.
6. The metal-organic framework composite material MOF-74(Cu)@SiO2 according to claim 1, characterized in that, In step 2), the stirring conditions after adding CTAB are: stirring at 298 K for 1 h; when adding anhydrous ethanol solution of tetraethyl silicate dropwise, stirring is continued at 323 K for 6 h; the stirring conditions for removing CTAB are: stirring at 298 K for 24 h.
7. A Pickering emulsion stabilized by MOF-74(Cu)@SiO2 composite material based on a metal-organic framework, characterized in that, The preparation method includes the following steps: take a metal-organic framework composite material MOF-74(Cu)@SiO2 as described in any one of claims 1-6, add toluene and water, sonicate and then vibrate up and down to obtain a Pickering emulsion based on MOF-74(Cu)@SiO2.
8. A Pickering emulsion based on a metal-organic framework composite material MOF-74(Cu)@SiO2 stabilized according to claim 7, characterized in that, MOF-74(Cu)@SiO2: Toluene: Water = 35 mg : 1.67 mL : 3.33 mL; Ultrasonic power was 100 W, ultrasonic time was 5 min, and up-and-down oscillation time was 5 min.
9. The application of the Pickering emulsion stabilized by MOF-74(Cu)@SiO2 based on a metal-organic framework as described in claim 7 in the catalytic deacetalization-Knoevenagel one-pot reaction, characterized in that, The method is as follows: Take benzaldehyde dimethyl acetal and a Pickering emulsion stabilized by MOF-74(Cu)@SiO2 based on a metal-organic framework, react at 353 K for 2 h, then add malononitrile and continue the reaction for 2 h.
10. The application according to claim 9, characterized in that, The molar ratio of benzaldehyde dimethyl acetal to malononitrile is 1.0 to 1.5.