Application of amino-functionalized rare earth cluster-based MOFs materials as catalyst in catalytic deacetalization-knoevenagel condensation reaction

Abstract

This invention belongs to the field of catalyst technology, specifically relating to the application of amino-functionalized rare earth cluster-based MOFs as catalysts in the catalytic deacetalization-Knoevenagel condensation reaction. The application method is as follows: Activated amino-functionalized rare earth cluster-based MOFs material Yb-BPDC-(NH2)2 or Dy-BPDC-(NH2)2 is placed in a reaction tube, followed by the sequential addition of the reaction substrates benzaldehyde dimethyl acetal and malononitrile. Acetonitrile is used as the solvent medium, and deionized water is added as a reaction promoter. Under continuous mechanical stirring and nitrogen protection, the reaction mixture is placed in an 80°C constant temperature oil bath for 12 hours. The amino-functionalized rare earth cluster-based MOFs material prepared by this invention exhibits excellent catalytic performance and can efficiently catalyze the deacetalization-Knoevenagel condensation reaction.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to the application of amino-functionalized rare earth cluster-based MOFs as catalysts in the catalytic deacetalization-Knoevenagel condensation reaction. Background Technology

[0002] In the field of chemistry today, the development of efficient, green, and sustainable catalytic reaction systems has always been a goal pursued by researchers. As a green and efficient synthetic strategy, tandem reactions have attracted much attention from researchers due to their atom economy and simple steps. Among many organic transformation reactions, the deacetal-Knoevenagel condensation reaction has become one of the current hot topics in organic chemistry research due to its important role in the preparation of pharmaceutical intermediates and the synthesis of fine chemicals. This reaction system achieves efficient construction from simple substrates to complex molecules through continuous multi-step transformations, showing good industrial application potential. However, traditional catalytic systems often have many problems, such as difficult catalyst recovery, harsh reaction conditions, low selectivity, and environmental unfriendliness, which limit the large-scale application of materials in industrial production. According to previous reports, some MOFs are high-performance catalysts for tandem reactions. For example, Han Zhengbo's research group previously reported an fcu-based MOF, denoted as Yb-BDC-NH2, which is an excellent catalyst for the one-pot tandem deacetylation-Knoevenagel condensation reaction for the synthesis of benzylidene malononitrile. Huang et al. successfully synthesized three-dimensional Mn-MOF using a solvothermal method. This material exhibits good thermal and chemical stability and good catalytic performance in the Knoevenagel condensation reaction.

[0003] Metal-organic frameworks (MOFs), as a novel type of heterogeneous porous crystalline material, have attracted widespread attention in the field of catalysis in recent years due to their unique properties, such as extremely high specific surface area, tunable pore structure, abundant active sites, and good chemical stability. These characteristics of MOFs make them ideal catalyst supports or even catalysts directly. Their topology, pore size, and chemical composition can be rationally designed to achieve confinement effects within functionalized pores containing catalytic sites that operate with high selectivity. This provides new ideas and methods for solving problems in traditional catalytic systems. Rare earth elements, due to their unique electronic structure and rich coordination chemistry, have exhibited excellent performance in catalysis. Introducing rare earth elements into MOFs to construct rare earth cluster-based MOFs (RE-MOFs) not only fully utilizes the catalytic activity of rare earth elements but also leverages the structural advantages of MOFs to achieve precise control of catalytic reactions. Rare earth cluster-based MOFs (RE-MOFs) are a special type of MOF with lanthanide metal ion centers. Due to their numerous empty f-electron orbitals, they are excellent Lewis acid sites. Some amino-forming organic ligand molecules have been shown to be Lewis bases. Furthermore, MOFs based on polynuclear rare earth (RE) clusters exhibit high stability and good catalytic activity, and have been applied in various fields. RE clusters assembled with multifunctional organic ligands can be used as an efficient strategy for designing MOFs with specific functions. Currently, several MOFs based on polynuclear RE clusters have been reported with significant catalytic activity.

[0004] The application of rare earth cluster-based MOF materials in the deacetalization-Knoevenagel condensation reaction is still in the stage of continuous exploration and development. Therefore, in-depth investigation of the catalytic performance of rare earth cluster-based MOF materials in this reaction and revealing the underlying catalytic mechanism are of great scientific significance and practical application value for developing new and efficient catalytic systems and promoting further development in related fields. Summary of the Invention

[0005] The purpose of this invention is to use amino-functionalized rare earth cluster-based MOFs materials as a substrate to prepare a series of rare earth cluster-based MOFs materials containing amino ligands and different types of rare earth nitrates.

[0006] The technical solution adopted in this invention is:

[0007] Application of amino-functionalized rare earth cluster-based MOFs as catalysts in the catalytic deacetalization-Knoevenagel condensation reaction.

[0008] Furthermore, in the above applications, the rare earth clusters in the amino-functionalized rare earth cluster-based MOFs material act as Lewis acidic catalytic sites to catalyze the deacetalization reaction, thereby catalyzing the deprotection process of benzaldehyde dimethyl acetal to generate benzaldehyde; at the same time, the amino groups in the amino-functionalized rare earth cluster-based MOFs material provide a Brønsted alkaline environment to catalyze the Knoevenagel condensation reaction of benzaldehyde and malononitrile.

[0009] Furthermore, the above application is carried out in the following way: using a reaction catalytic tube as a reaction device, benzaldehyde dimethyl acetal and malononitrile are taken, activated amino-functionalized rare earth cluster-based MOFs material is used as a catalyst, acetonitrile is used as a solvent medium, and deionized water is used as a reaction aid, and the reaction is carried out in a constant temperature oil bath.

[0010] Furthermore, in the above application method, the amino-functionalized rare earth cluster-based MOFs material is subjected to 80... o Activation under vacuum for 24 h.

[0011] Furthermore, in the above application method, the amount of the activated amino-functionalized rare earth cluster-based MOFs material is 50 mg, the amount of benzaldehyde dimethyl acetal is 2 mmol, and the amount of malononitrile is 2.1 mmol.

[0012] Furthermore, in the above application method, the amount of acetonitrile used is 2 mL, and the amount of deionized water used is 50 μL.

[0013] Furthermore, the above application method involves reacting the sample in an 80°C constant temperature oil bath for 12 hours.

[0014] Furthermore, in any of the above applications, the amino-functionalized rare earth cluster-based MOFs material is Yb-BPDC-(NH2)2, Dy-BPDC-(NH2)2, Eu-BPDC-(NH2)2, Tb-BPDC-(NH2)2, Y-BPDC-(NH2)2, Gd-BPDC-(NH2)2, or Sm-BPDC-(NH2)2.

[0015] Preferably, the amino-functionalized rare earth cluster-based MOFs material is Yb-BPDC-(NH2)2 or Dy-BPDC-(NH2)2.

[0016] Furthermore, in the above-mentioned application, the preparation method of the amino-functionalized rare earth cluster-based MOFs material includes the following steps: dissolving a mixture of 0.018 mmol H2BPDC-(NH2)2 and 0.018 mmol RE(NO3)3·6H2O in a mixed solvent of 1.5 mL DMF and 0.5 mL H2O, stirring at room temperature in a 5 mL heat-resistant glass bottle until completely dissolved, placing the glass bottle in a preheated 378 K forced-air oven for 12 hours, and after the reaction is complete, slowly cooling the bottle to room temperature at a cooling rate of 5 Kh. -1 The synthesized sample was repeatedly washed and purified with DMF, filtered at room temperature, and air-dried naturally; the RE(NO3)3·6H2O was Yb(NO3)3·6H2O, Dy(NO3)3·6H2O, Eu(NO3)3·6H2O, Tb(NO3)3·6H2O, Y(NO3)3·6H2O, Gd(NO3)3·6H2O, or Sm(NO3)3·6H2O.

[0017] The beneficial effects of this invention are:

[0018] 1. This invention provides a novel three-dimensional RE-MOF material, which not only possesses a unique pore and channel structure, but is also named RE-MOF: Yb-BPDC-(NH2)2, Dy-BPDC-(NH2)2, Eu-BPDC-(NH2)2, Tb-BPDC-(NH2)2, Y-BPDC-(NH2)2, Gd-BPDC-(NH2)2, Sm-BPDC-(NH2)2, etc. (where H2BPDC-(NH2)2 represents 2,2'-diaminobiphenyl-4,4'-dicarboxylic acid). These RE-MOF materials not only exhibit the potential as excellent Lewis acid catalysts, but their selected organic ligand—2,2'-diaminobiphenyl-4,4'-dicarboxylic acid (H2BPDC-(NH2)2)—can also efficiently self-assemble with RE(III) ions under hydrothermal conditions due to its unique two carboxyl group structure, forming a stable three-dimensional MOF structure. Furthermore, the amino groups on the ligands endow these RE-MOFs materials with Lewis base properties, thereby further broadening their application prospects in the field of catalysis.

[0019] 2. The amino-functionalized rare earth cluster-based MOFs material prepared in this invention achieves 80 oHighly efficient catalysis of the deacetalization-Knoevenagel condensation reaction under C conditions. The experimental results will provide new ideas and methods for the design and synthesis of rare earth MOFs and their functionalized modified materials, as well as their application in catalytic organic conversion. The raw materials used in this invention are readily available, the synthesis process is green and environmentally friendly, and the operation is simple, thus possessing good market economic value and broad application prospects. Attached Figure Description

[0020] Figure 1 This is a schematic diagram illustrating the synthesis of the 2,2'-diaminobiphenyl-4,4'-dicarboxylic acid ligand of the present invention.

[0021] Figure 2 This is the 1H NMR spectrum of H2BPDC-(NH2)2 of this invention. 1 H NMR).

[0022] Figure 3 These are optical microscope images of the amino-functionalized rare earth cluster-based MOFs materials of the present invention, wherein (a) is Yb-BPDC-(NH2)2 and (b) is Dy-BPDC-(NH2)2.

[0023] Figure 4 This is the PXRD diffraction pattern of the amino-functionalized rare earth cluster-based MOFs material of the present invention, wherein, from top to bottom, they are Y-BPDC-(NH2)2, Dy-BPDC-(NH2)2, Eu-BPDC-(NH2)2, Tb-BPDC-(NH2)2, Gd-BPDC-(NH2)2, Sm-BPDC-(NH2)2, Yb-BPDC-(NH2)2, and UiO-67.

[0024] Figure 5 The images show the FT-IR spectra of the amino-functionalized rare earth cluster-based MOFs materials of this invention, wherein, from top to bottom, they are Dy-BPDC-(NH2)2, Y-BPDC-(NH2)2, Tb-BPDC-(NH2)2, Eu-BPDC-(NH2)2, Sm-BPDC-(NH2)2, Gd-BPDC-(NH2)2, and H2-BPDC-(NH2)2.

[0025] Figure 6 The thermogravimetric analysis diagrams of the amino-functionalized rare earth cluster-based MOFs materials of the present invention are shown, where (a) is Yb-BPDC-(NH2)2 and (b) is Dy-BPDC-(NH2)2.

[0026] Figure 7 The chemical stability of the amino-functionalized rare earth cluster-based MOFs material of the present invention is shown in (a) as Yb-BPDC-(NH2)2 and (b) as Dy-BPDC-(NH2)2.

[0027] Figure 8 These are the CO2 adsorption isotherm curves and pore size analysis diagrams of the amino-functionalized rare earth cluster-based MOFs materials of the present invention at 195 K, wherein (a) is Yb-BPDC-(NH2)2 and (b) is Dy-BPDC-(NH2)2.

[0028] Figure 9 This is a diagram illustrating the synthesis process and catalytic mechanism of the condensation reaction of RE-BPDC-(NH2)2 according to the present invention.

[0029] Figure 10 This is a schematic diagram of the catalytic deacetalization-Knoevenagel condensation reaction of the amino-functionalized rare earth cluster-based MOFs material of this invention.

[0030] Figure 11 This is a leaching experiment diagram of the amino-functionalized rare earth cluster-based MOFs material of the present invention catalyzing the deacetalization-Knoevenagel condensation reaction, wherein (a) is Yb-BPDC-(NH2)2 and (b) is Dy-BPDC-(NH2)2.

[0031] Figure 12 This is a schematic diagram comparing the cycle performance of the amino-functionalized rare earth cluster-based MOFs material as a catalyst of the present invention, wherein (a) is Yb-BPDC-(NH2)2 and (b) is Dy-BPDC-(NH2)2.

[0032] Figure 13 These are the powder diffraction pattern (a) and infrared spectrum (b) of Yb-BPDC-(NH2)2 of the present invention.

[0033] Figure 14 These are the powder diffraction pattern (a) and infrared spectrum (b) of Dy-BPDC-(NH2)2 of the present invention. Detailed Implementation

[0034] Example 1: Amino-functionalized rare earth cluster-based MOF materials

[0035] (a) The preparation method is as follows:

[0036] 1. Preparation of the organic ligand 2,2'-diaminobiphenyl-4,4'-dicarboxylic acid (H2BPDC-(NH2)2).

[0037] The reaction formula is as follows Figure 1 .

[0038] 1) Preparation of dimethyl 2,2'-dinitrobiphenyl-4,4'-dicarboxylate

[0039] First, weigh 5 g (20 mmol, 1 eq) of dimethyl 4,4'-biphenyl dicarboxylate and dissolve it completely in 25 mL of 95% sulfuric acid. Then, under the influence of an ice-water bath at 0°C and a magnetic stirrer, slowly add a mixed solution containing 65% nitric acid (2 mL, 40 mmol, 2.3 eq) and 95% sulfuric acid (0.75 mL) dropwise over 45 minutes. After the addition is complete, continue stirring the reaction system at room temperature for another 5 minutes. Next, pour the reaction solution obtained in the above steps into 100 mL of ice water, at which point a paste-like white precipitate will form. Dissolve this precipitate in ethyl acetate. Then, wash the resulting organic phase sequentially: first with distilled water (30 mL each time, 3 times), then with saturated sodium bicarbonate solution (NaHCO3, 30 mL each time, 2 times), and finally with saturated sodium chloride solution (NaCl, 30 mL each time, 2 times). After washing, the organic phase was dried with anhydrous magnesium sulfate (MgSO4) and allowed to stand for 12 hours. Finally, the solvent in the organic phase was removed by rotary evaporation. 25 mL of acetonitrile was added to the remaining solution, followed by filtration to remove unreacted reagents. The product at this point is named dimethyl 2,2'-dinitrobiphenyl-4,4'-dicarboxylate, with the chemical formula C2. 16 H 12 N₂O₈, with a relative molecular mass of 360.28 g / mol. The yield of this step is approximately 96%. 1 H NMR (300 MHz, CDCl3) δ 8,90 (d, J = 1.6 Hz, 1H), 8,36 (dd, J = 8.0, 1.7 Hz, 1H), 7,40 (d, J = 8.0 Hz, 1H), 4,02 (s, 3H).

[0040] 2) Preparation of 2,2'-diaminobiphenyl-4,4'-dicarboxylic acid (H2BPDC-(NH2)2)

[0041] The intermediate product was reduced to 2,2'-diaminobiphenyl-4,4'-dicarboxylic acid. The intermediate product (5.03 g, 20 mmol, 1 eq) was dissolved in 205 mL of 37% hydrochloric acid. Then, stannous chloride dihydrate (26.50 g, 120 mmol, 7 eq) was slowly added under magnetic stirring. After the addition was complete, the solution was heated to 70 °C and reacted overnight. After cooling, the solid and liquid were separated by vacuum filtration. The obtained solid was washed with distilled water (250 mL). The slightly yellow product was dried under vacuum in an oven at 40 °C. The chemical formula of the product is C0. 14 H 12N₂O₈, with a molar mass of 272.26 g / mol. The yield of this step is approximately 82%. 1 H NMR (DMSO-d) 6 , 300 MHz) δ 7.74 (d, J=1.5 Hz, 1H), 7.56 (dd, J=7.9, 1.6 Hz, 1H), 7.32 (d, J=7.9 Hz, 1H) ( Figure 2 ).

[0042] 2. A series of amino-functionalized rare earth cluster-based MOFs materials RE-BPDC-(NH2)2 (Yb-BPDC-(NH2)2, Dy-BPDC-(NH2)2, Eu-BPDC-(NH2)2, Tb-BPDC-(NH2)2, Y-BPDC-(NH2)2, Gd-BPDC-(NH2)2, Sm-BPDC-(NH2)2) were prepared.

[0043] 1) Synthesis of Yb-BPDC-(NH2)2

[0044] A mixture of H₂BPDC-(NH₂)₂ (5.0 mg, 0.018 mmol) and Yb(NO₃)₃·6H₂O (8.575 mg, 0.018 mmol) was dissolved in a mixed solvent of 1.5 mL DMF and 0.5 mL H₂O in a 5 mL heat-resistant glass vial and stirred at room temperature until completely dissolved. The vial was then placed in a preheated 378 K oven for 12 hours. After the reaction was complete, the vial was slowly cooled (at a rate of 5 Kh). -1 After reaching room temperature, the synthesized sample was repeatedly washed and purified with DMF, filtered at room temperature, and air-dried to obtain pale yellow regular hexagonal prism crystals. The crystal yield was 74%.

[0045] 2) Synthesis of Dy-BPDC-(NH2)2

[0046] The synthesis of the complex Dy-BPDC-(NH2)2 was similar to that of Yb-BPDC-(NH2)2, except that Dy(NO3)3·6H2O (8.38 mg, 0.018 mmol) was used instead of Yb(NO3)3·6H2O (8.575 mg, 0.018 mmol), yielding pale yellow, regular hexagonal plate-like crystals. The crystal yield was 78%.

[0047] 3) Synthesis of Eu-BPDC-(NH2)2

[0048] The synthesis method of the complex Eu-BPDC-(NH2)2 is similar to that of Yb-BPDC-(NH2)2, except that Eu(NO3)3·6H2O (8.187 mg, 0.018 mmol) is used instead of Yb(NO3)3·6H2O (8.575 mg, 0.018 mmol), and pale yellow regular hexagonal plate-like crystals are also obtained.

[0049] 4) Synthesis of Tb-BPDC-(NH2)2

[0050] The synthesis method of the complex Tb-BPDC-(NH2)2 is similar to that of Yb-BPDC-(NH2)2, except that Tb(NO3)3·6H2O (8.314 mg, 0.018 mmol) is used instead of Yb(NO3)3·6H2O (8.575 mg, 0.018 mmol), and pale yellow regular hexagonal plate-like crystals are also obtained.

[0051] 5) Synthesis of Y-BPDC-(NH2)2

[0052] The synthesis method of the complex Y-BPDC-(NH2)2 is similar to that of Yb-BPDC-(NH2)2, except that Y(NO3)3·6H2O (7.031 mg, 0.018 mmol) is used instead of Yb(NO3)3·6H2O (8.575 mg, 0.018 mmol), and pale yellow regular hexagonal plate-like crystals are also obtained.

[0053] 6) Synthesis of Gd-BPDC-(NH2)2

[0054] The synthesis method of the complex Gd-BPDC-(NH2)2 is similar to that of Yb-BPDC-(NH2)2, except that Gd(NO3)3·6H2O (8.284 mg, 0.018 mmol) is used instead of Yb(NO3)3·6H2O (8.575 mg, 0.018 mmol), and pale yellow regular hexagonal plate-like crystals are also obtained.

[0055] 7) Synthesis of Sm-BPDC-(NH2)2

[0056] The synthesis method of the complex Sm-BPDC-(NH2)2 is similar to that of Yb-BPDC-(NH2)2, except that Sm(NO3)3·6H2O (8.157 mg, 0.018 mmol) is used instead of Yb(NO3)3·6H2O (8.575 mg, 0.018 mmol), and pale yellow regular hexagonal plate-like crystals are also obtained.

[0057] The structure of the amino-functionalized rare earth cluster-based MOFs material synthesized in this invention is shown in the figure.

[0058] The test was conducted using an X-ray diffractometer, and the results are as follows: Figure 4 As shown. In Figure 4 The PXRD diffraction pattern of the rare earth cluster-based MOFs material of the present invention can be observed. From top to bottom, they are Y-BPDC-(NH2)2, Dy-BPDC-(NH2)2, Eu-BPDC-(NH2)2, Tb-BPDC-(NH2)2, Gd-BPDC-(NH2)2, Sm-BPDC-(NH2)2, Yb-BPDC-(NH2)2, and UiO-67.

[0059] The test was conducted using a Fourier transform infrared spectrometer, and the results are as follows: Figure 5 As shown. FT-IR spectral analysis indicates that, from Figure 5 It can be observed at 750 cm -1 and 832 cm -1 The absorption peak at 1256 cm⁻¹ is due to the bending vibration of the CH bond on the benzene ring. -1 There is a stretching vibration peak of CN bond at 1526 cm⁻¹. -1 1487 cm -1 The absorption peak at 1608 cm⁻¹ is due to the stretching vibration of C=C on the benzene ring skeleton, while the bending vibration peak of NH is observed at 1608 cm⁻¹. -1 At 1760 cm⁻¹, the characteristic peak of C=O is shown. -1 The formation of metal-ligand bonds alters the electron cloud distribution and vibrational frequencies of the chemical bonds in the ligands, leading to a shift in the peak positions in the FT-IR spectrum. FT-IR spectroscopy confirms the feasibility of synthesizing amino-functionalized rare-earth cluster-based MOFs materials using a solvothermal method.

[0060] like Figure 6 As shown, the thermogravimetric analysis (TGA) plots illustrate the relationship between the mass and temperature of the two synthesized materials, Yb-BPDC-(NH2)2 and Dy-BPDC-(NH2)2, measured under programmed temperature control. The plots reveal two significant mass loss phases. The first phase occurs around 100-150℃, corresponding to the loss of adsorbed water at the crystal lattice surface. Specifically, Yb-BPDC-(NH2)2 experiences a mass loss of 15.2% in this phase, while Dy-BPDC-(NH2)2 experiences a loss of 12.8%. The second phase occurs in the 500-600℃ range, due to the gradual collapse of the framework.

[0061] like Figure 7As shown, the chemical stability of the two synthesized materials, Yb-BPDC-(NH2)2 and Dy-BPDC-(NH2)2, was tested. Both materials were immersed in acetone, methanol, dichloromethane, ethanol, and acetonitrile, respectively, for 24 h, then separated and dried. PXRD analysis revealed that the structures of both materials remained unchanged after treatment with different organic solvents, demonstrating excellent chemical stability.

[0062] like Figure 8 The figure shows the measurement results of CO2 adsorption-desorption at 195 K, yielding the CO2 adsorption-desorption isotherm. As the relative pressure (P / P0) gradually increases from 0, the adsorption capacity (n / cm³) increases. 3 The specific surface area (STP) of the adsorption capacity continuously increases. In the low relative pressure region, the increase in adsorption is relatively slow, at which point CO2 molecules are mainly adsorbed on the active sites on the inner surface of the material, which is monolayer adsorption. As the relative pressure further increases, the rate of increase in adsorption accelerates, indicating that in addition to monolayer adsorption, multilayer adsorption and condensation phenomena begin to appear in the pores of the material. From the overall curve, the adsorption capacity still increases to a certain extent under higher relative pressure, indicating that Yb-BPDC-(NH2)2 and Dy-BPDC-(NH2)2 have a certain adsorption capacity for CO2. Through relevant calculations (such as using the BET method and Brunauer-Emmett-Teller theory), the specific surface areas of materials Yb-BPDC-(NH2)2 and Dy-BPDC-(NH2)2 can be obtained from the adsorption isotherm data as 227.23 m². 2 ·g -1 and 245.91 m 2 ·g -1 .

[0063] Example 2: Deacetalization-Knoevenagel condensation reaction catalyzed by amino-functionalized rare earth cluster-based MOFs (RE-MOFs)

[0064] The amino-functionalized RE-MOFs prepared in Example 1 were used as catalysts to catalyze the Deacetalization-Knoevenagel condensation reaction.

[0065] The method is as follows:

[0066] First, the obtained amino-functionalized RE-MOFs were subjected to 80°C. oVacuum activation for 24 h. First, 50 mg of activated amino-functionalized RE-MOF catalyst was loaded into a 10 mL reaction catalytic tube, followed by the reaction substrates benzaldehyde dimethyl acetal (2 mmol) and malononitrile (2.1 mmol), using 2 mL acetonitrile as the solvent and 50 μL of deionized water as a reaction promoter. The reaction mixture was placed in an 80°C constant temperature oil bath for 12 hours under continuous mechanical stirring and nitrogen protection. After this reaction, the catalyst was separated by centrifugation. The product (trans-3-phenyl-2-propenonitrile) was detected by gas chromatography (GC), and the conversion and yield were calculated based on the peak position and peak area. The centrifuged catalyst solid was washed three times with DMF, then slowly dried at room temperature, and finally the sample was collected for subsequent cyclic catalytic experiments. The results are shown in Tables 1-4. Figures 9-14 As shown.

[0067] Table 1 One-pot tandem catalytic reaction of rare earth cluster-based isomorphic RE-BPDC-(NH2)2 in this invention

[0068] Entry MOF m (mg) Conv.of a(%) Yield of b(%) Yield of c(%) 1 Dy-BPDC-(NH2)2 60 88.55 8.68 79.87 2 <![CDATA[Dy-BPDC-(NH2)2]]> 40 84.40 9.07 75.33 3 <![CDATA[Dy-BPDC-(NH2)2]]> 50 98.96 4.68 94.28 4 <![CDATA[Eu-BPDC-(NH2)2]]> 50 98.80 5.26 92.74 5 <![CDATA[Tb-BPDC-(NH2)2]]> 50 94.88 5.04 89.83 6 <![CDATA[Y-BPDC-(NH2)2]]> 50 98.72 2.15 96.57 7 <![CDATA[Gd-BPDC-(NH2)2]]> 50 97.34 3.28 94.06 8 <![CDATA[Sm-BPDC-(NH2)2]]> 50 98.54 5.45 93.09 9 No catalyst 0 0 trace trace 10 Second recycle 50 98.64 4.97 93.67 11 Third recycle 50 98.03 5.73 92.30 12 Fourth recycle 50 97.75 5.89 91.86

[0069] Reaction conditions: benzaldehyde dimethyl acetal (2 mmol), malononitrile (2.1 mmol), acetonitrile (2 mL), distilled water (50 µL); reaction temperature: 80℃; reaction time: 16 h.

[0070] Table 2. Investigation of the one-pot series catalytic reaction temperature of Dy-BPDC-(NH2)2 in this invention

[0071] Entry T(℃) Conv.of a(%) Yield of b(%) Yield of c(%) 1 60 74.09 8.04 66.05 2 70 79.92 7.96 71.96 3 80 98.96 4.68 94.28

[0072] Reaction conditions: benzaldehyde dimethyl acetal (2 mmol), malononitrile (2.1 mmol), acetonitrile (2 mL), distilled water (50 µL), Dy-BPDC-(NH2)2 dosage (50 mg); reaction time: 16 h.

[0073] Table 3. Catalyst Quantity Study for One-Pot Series Catalytic Reaction of Yb-BPDC-(NH2)2 in this Invention

[0074] Entry m (mg) Conv.of a(%) Yield of b(%) Yield of c(%) 1 40 80.66 3.72 76.94 2 50 99.79 0.35 99.45 3 60 82.23 4.42 77.81

[0075] Reaction conditions: benzaldehyde dimethyl acetal (2 mmol), malononitrile (2.1 mmol), acetonitrile (2 mL), distilled water (50 µL), Yb-BPDC-(NH2)2 dosage (40, 50, 60 mg); reaction temperature: 80 ℃; reaction time: 16 h.

[0076] Table 4. Investigation of the one-pot series catalytic reaction temperature of Yb-BPDC-(NH2)2 in this invention.

[0077] Entry T(℃) Conv.of a(%) Yield of b(%) Yield of c(%) 1 60 79.17 18.6 60.57 2 70 89.96 10.34 79.62 3 80 99.79 0.35 99.45

[0078] Reaction conditions: benzaldehyde dimethyl acetal (2 mmol), malononitrile (2.1 mmol), acetonitrile (2 mL), distilled water (50 µL), Yb-BPDC-(NH2)2 dosage (50 mg); reaction time: 16 h.

[0079] A blank control experiment was first conducted (see Table 1, item 9), and the results showed that the yield of the final product c was trace. This result indicates that the reaction requires a catalyst to improve the yield. Therefore, a synthesized rare earth cluster-based metal-organic framework was added as a catalyst for catalytic experiments. The experimental results are shown in Table 1. After 16 h of reaction, the yields of product c catalyzed by the isomorphic complexes Dy-BPDC-(NH2)2, Tb-BPDC-(NH2)2, Gd-BPDC-(NH2)2, Eu-BPDC-(NH2)2, Sm-BPDC-(NH2)2, and Y-BPDC-(NH2)2 were 94.28%, 89.83%, 94.06%, 92.74%, 93.09%, and 96.57%, respectively. Therefore, the catalytic activity of Dy-BPDC-(NH2)2 was selected as a representative example of isomorphic MOFs for further study to seek the optimal reaction conditions.

[0080] This experiment used an amino-functionalized Dy-BPDC-(NH2)2 complex as a model catalyst to systematically investigate the effects of changes in reaction parameters on the deacetal-Knoevenagel tandem reaction. The experimental data showed that the catalytic efficiency was not simply linearly related to the catalyst loading. When the catalyst loading was increased to 60 mg, the yield of the target product decreased to 79.87% (see Table 1, item 1); conversely, when reduced to 40 mg, the conversion efficiency decreased to 75.33% (see Table 1, item 2). Temperature effect studies showed that within the range of 60-80 °C, the reaction yield significantly increased with increasing temperature, achieving yields of 66.05%, 71.96%, and 94.28% at 60 °C, 70 °C, and 80 °C (see Table 2, items 1, 2, and 3), respectively, confirming that appropriately increasing the reaction temperature is beneficial for promoting this tandem conversion process. Therefore, the most suitable reaction parameters for the deacetalization of Knoevenagel catalyzed by Dy-BPDC-(NH2)2 were determined to be: a reaction temperature of 80 degrees Celsius and a dosage of 50 mg. To verify the necessity of catalyst addition, a blank control test was set up in this process. Without the addition of any catalytic components, the yield of c was only trace (see Table 1, item 9). The results fully demonstrate that: (1) the energy barrier of this tandem reaction is high under the condition of no catalyst addition, and it is difficult to proceed spontaneously; (2) the addition of the designed Dy-BPDC-(NH2)2 catalyst can significantly reduce the activation energy of the reaction process and effectively promote the synergistic process of the deacetalization-Knoevenagel condensation reaction.

[0081] Similarly, similar catalytic experiments were conducted on the Yb-BPDC-(NH2)2 catalyst. During the experiments, it was observed that the catalytic efficiency did not have a simple linear relationship with the catalyst loading. When the catalyst loading was increased to 60 mg, the yield of the target product decreased to 77.81% (see Table 3, item 3); conversely, when it was reduced to 40 mg, the conversion efficiency decreased to 76.94% (see Table 3, item 1). Temperature effect studies showed that within the range of 60-80 °C, the reaction yield significantly increased with increasing temperature, achieving yields of 60.57%, 79.62%, and 99.45% at 60 °C, 70 °C, and 80 °C (see Table 4, items 1, 2, and 3), respectively. Therefore, the optimal reaction parameters for the catalytic deacetalization of Knoevenagel using Yb-BPDC-(NH2)2 as the catalyst were determined to be: a reaction temperature of 80 °C and a loading of 50 mg.

[0082] Figure 10It visually presents the synergistic effect of "rare earth cluster catalytic sites + amino functional sites" in MOF materials, as well as the reaction advantage of "one-step tandem, no need to separate intermediates", clearly demonstrating the transformation pathway of reactants → intermediates → products and the action mode of the catalytic host.

[0083] like Figure 11 As shown, the significant difference between the two sets of data intuitively demonstrates that the catalytic activity of MOFs materials originates from the "rare earth cluster catalytic sites + amino functional sites" on their solid surface, rather than from the inactive components leaching into the solution to exert their effect. This further verifies that the MOFs material is a heterogeneous catalyst with the basis for recycling.

[0084] like Figure 12 As shown, using Yb-BPDC-(NH2)2 and Dy-BPDC-(NH2)2 as catalysts, at 80 o The recyclability of the catalyst under nitrogen protection and with acetonitrile as the solvent was investigated. After the reaction was complete, the remaining catalyst was recovered by centrifugation, washed multiple times with MeOH, and dried at 80°C. o After vacuum activation for 24 hours, the next cycle of experiments was conducted. Figure 12 As shown, after three rounds of cyclic experiments, the catalytic activity of the prepared Yb-BPDC-(NH2)2 and Dy-BPDC-(NH2)2 was almost completely preserved. PXRD spectroscopy analysis revealed that the structures of both materials remained unchanged. Figure 13 and Figure 14 Cyclic experiments have confirmed that Yb-BPDC-(NH2)2 and Dy-BPDC-(NH2)2 materials have excellent cycling performance and stability.

[0085] The possible mechanism of this reaction is as follows: Figure 9 As shown, in the research system of this invention, the rare earth clusters in Yb-BPDC-(NH2)2 and Dy-BPDC-(NH2)2 can act as Lewis acidic catalytic sites to catalyze the deacetalization reaction, thereby catalyzing the deprotection process of benzaldehyde dimethyl acetal to generate benzaldehyde. Simultaneously, the amino groups (-NH2) in the material provide a Brønsted alkaline environment that can catalyze the Knoevenagel condensation reaction between the generated benzaldehyde and malononitrile (CH2(CN)2). The amino group acts as a nucleophile, attacking the carbonyl group, releasing water in the process, and subsequently forming an imine intermediate. Subsequently, the malononitrile reacts with this imine intermediate to finally generate the final product, while releasing an alkali (NH2). Figure 9Therefore, Yb-BPDC-(NH2)2 and Dy-BPDC-(NH2)2, as special catalysts, possess both acidic and basic catalytic sites. The rare earth metal clusters contain a large number of unsaturated Yb and Dy metal sites, which can function as Lewis acid sites.

Claims

1. Application of amino-functionalized rare earth cluster-based MOFs as catalysts in the catalytic deacetalization-Knoevenagel condensation reaction.

2. The application according to claim 1, characterized in that, The rare earth clusters in the amino-functionalized rare earth cluster-based MOFs material act as Lewis acidic catalytic sites to catalyze the deacetalization reaction, thereby catalyzing the deprotection process of benzaldehyde dimethyl acetal to generate benzaldehyde. At the same time, the amino groups in the amino-functionalized rare earth cluster-based MOFs material provide a Brønsted alkaline environment to catalyze the Knoevenagel condensation reaction of benzaldehyde and malononitrile.

3. The application according to claim 2, characterized in that, The method is as follows: using a reaction catalytic tube as the reaction device, benzaldehyde dimethyl acetal and malononitrile are taken, activated amino-functionalized rare earth cluster MOFs material is used as the catalyst, acetonitrile is used as the solvent medium, and deionized water is used as the reaction aid. The reaction is carried out in a constant temperature oil bath.

4. The application according to claim 3, characterized in that, The amino-functionalized rare earth cluster-based MOFs material was developed at 80... o Activation under vacuum for 24 h.

5. The application according to claim 3, characterized in that, The activated amino-functionalized rare earth cluster-based MOFs material was used in an amount of 50 mg, benzaldehyde dimethyl acetal in an amount of 2 mmol, and malononitrile in an amount of 2.1 mmol.

6. The application according to claim 3, characterized in that, The amount of acetonitrile used is 2 mL, and the amount of deionized water used is 50 μL.

7. The application according to claim 3, characterized in that, The reaction was carried out in a constant temperature oil bath at 80℃ for 12 hours.

8. The application according to any one of claims 1-7, characterized in that, The amino-functionalized rare earth cluster-based MOFs materials are Yb-BPDC-(NH2)2, Dy-BPDC-(NH2)2, Eu-BPDC-(NH2)2, Tb-BPDC-(NH2)2, Y-BPDC-(NH2)2, Gd-BPDC-(NH2)2 or Sm-BPDC-(NH2)2.

9. The application according to claim 8, characterized in that, The amino-functionalized rare earth cluster-based MOFs material is Yb-BPDC-(NH2)2 or Dy-BPDC-(NH2)2.

10. The application according to claim 8, characterized in that, The preparation method of the amino-functionalized rare earth cluster-based MOFs material includes the following steps: A mixture of 0.018 mmol H2BPDC-(NH2)2 and 0.018 mmol RE(NO3)3·6H2O is dissolved in a mixed solvent of 1.5 mL DMF and 0.5 mL H2O. The solution is stirred at room temperature in a 5 mL heat-resistant glass vial until completely dissolved. This vial is then placed in a preheated 378 K oven for 12 hours. After the reaction is complete, the vial is slowly cooled to room temperature at a cooling rate of 5 Kh. -1 The synthesized sample was repeatedly washed and purified with DMF, filtered at room temperature, and air-dried naturally; the RE(NO3)3·6H2O was Yb(NO3)3·6H2O, Dy(NO3)3·6H2O, Eu(NO3)3·6H2O, Tb(NO3)3·6H2O, Y(NO3)3·6H2O, Gd(NO3)3·6H2O, or Sm(NO3)3·6H2O.

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