Synthesis method of trivalent rhodium covalent organic framework catalyst

Abstract

The invention discloses a synthesis method of a trivalent rhodium covalent organic framework catalyst. The method comprises the following steps: uniformly mixing 1, 3, 6, 8-tetra-(p-aminophenyl)-pyrene and 2, 2 '-bipyridine-5, 5'-dicarboxaldehyde in an organic solvent, and sequentially carrying out an acetic acid catalyzed Schiff base condensation reaction, an oxidative cyclization reaction and a trivalent rhodium metallization process to finally obtain the trivalent rhodium covalent organic framework. A pi-conjugated system extended based on the covalent organic framework has a trivalent rhodium active center with good chemical stability, thermal stability and atomic-level dispersion, and the covalent organic framework can be used for thermally driven or optically driven trivalent rhodium catalytic region selective C (sp2)-H bond functionalization. And effective cyclic utilization of trivalent rhodium in regioselectivity C (sp2)-H bond functionalization is realized.

Description

Technical Field

[0001] The invention discloses a method for synthesizing a trivalent rhodium covalent organic framework catalyst, and relates to the technical field of organic functional material synthesis. Background Art

[0002] Over the past few decades, Rh(III)-catalyzed C(sp 2 )-H bond functionalization has made significant progress in the field of organic synthetic chemistry. The reaction can efficiently construct complex organic molecules, while having excellent atom economy and step economy (JC Lewis, RGBergman and JA Elman, Acc. Chem. Res., 2008, 41, 1013-1025). However, the use of Rh (III) catalysts under homogeneous reaction conditions usually leads to heavy metal residues, and these catalysts are difficult to recover by simple post-treatment (JB Zimmerman, PT A Nastas, HC Erythropel and W. Leitner, Science, 2020, 367, 397-400). In addition, the catalytic activity of Rh (III) catalysts is highly dependent on coordination ligands, but the synthesis of these ligands is usually complicated and costly (B. Ye and N. Cramer, Acc. Chem. Res., 2015, 48, 1308-1318).

[0003] Covalent organic frameworks (COFs), as a new type of porous organic polymer, stand out for their high crystallinity, periodic structure, adjustability and excellent stability (CS Diercks and OMYaghi, Science, 2017, 355, eaal1585). So far, COFs have been widely used in various chemical-related fields, especially in heterogeneous catalytic organic transformations (J. Wang and S. Zhuang, Coord. Chem. Rev., 2019, 400, 213046). According to their different working modes, the main roles of COFs in heterogeneous catalytic organic transformations can be divided into the following types: (1) using the acidity and alkalinity of pre-installed functional groups to catalyze the reaction as a heterogeneous Lewis acid or Lewis base catalyst (Q. Fang, S. Gu, J. Zheng, Z. Zhuang, S. Qiu and Y. Yan, Angew. Chem. Int. Ed., 2014, 53, 2878-2882); (2) through physical or chemical interactions, as a heterogeneous carrier to highly disperse metals or other catalytic sites in the reaction system (S.-Y. Ding, J. Gao, Q. Wang, Y. Zhang, W.-G. Song, C.-Y. Su and W. Wang, J. Am. Chem. Soc., 2011, 133, 19816-19822), thereby catalyzing the reaction; (3) using the extended π-conjugated system to absorb visible light and drive the reaction through energy transfer (ET) or single electron transfer (SET) (H. Wang, H. Wang, Z. Wang, L. Tang, G. Zeng, P. Xu, M. Chen, T. Xiong, C. Zhou, X. Li, D. Huang, Y. Zhu, Z. Wang and J. Tang, Chem. Soc. Rev., 2020, 49, 4135-4165); (4) by introducing chiral organic units, asymmetric catalytic active sites are formed, thereby driving stereoselective reactions (X. Wang, X. Han, J. Zhang, X. Wu, Y. Liu and Y.Cui, J.Am.Chem.Soc., 2016, 138, 12332-12335). These modes of action demonstrate four different application strategies of COF in heterogeneous catalytic organic reactions. Based on these strategies, the participation of COF can enable various organic transformations that are usually carried out under homogeneous conditions to be achieved under heterogeneous conditions, and the reaction efficiency can be maintained. More importantly, COF is almost insoluble in any organic solvent and can be easily separated by simple filtration or centrifugation to achieve excellent recyclability and reaction sustainability.

[0004] In summary, the application of COF catalysts in organic transformations may be the most ideal path to achieve green chemistry. However, COF catalysts still face the following challenges in practical applications. First, imine-linked COFs are often used to catalyze organic transformations, but the stability of the C=N bond is poor in a strong acid environment, which makes it difficult to meet practical needs. Secondly, for metal covalent organic frameworks (MCOFs), the main method to fix the metal center is through the coordination of the metal with the organic monomer. Although replacing the coordination bond with a covalent bond can significantly enhance the stability of the material, in some reactions that rely on precise coordination, such as transition metal-catalyzed selective CH bond functionalization, excessive stability may limit the controllability of the catalytic center, affect the effective interaction with the substrate, and thus reduce the reaction efficiency. In addition, in existing studies, most COF catalysts are only used for a single type of reaction, and their universality and tolerance in different reaction types have not been fully explored.

[0005] Therefore, the development of a Rh(III) covalent organic framework catalyst with excellent thermal stability, chemical stability and multifunctionality can achieve sustainable thermal-driven or visible-light-driven Rh(III)-catalyzed C(sp 2 )-H bond functionalization, which is of great significance for promoting the development of materials chemistry and organic synthetic chemistry. Summary of the invention

[0006] The invention discloses a synthesis method of a trivalent rhodium covalent organic framework (RhCOF-SYNU-1) to obtain a covalent organic framework with an extended π-conjugated system, excellent stability and atomic-level dispersed trivalent rhodium active centers;

[0007] The present invention is achieved through the following technical solutions:

[0008] A method for synthesizing a trivalent rhodium covalent organic framework catalyst comprises:

[0009] The Schiff base condensation reaction of 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene and 2,2'-bipyridine-5,5'-dicarboxaldehyde was carried out;

[0010] The product obtained by the Schiff base condensation reaction is subjected to an oxidative cyclization reaction with p-trifluoromethylphenylacetylene;

[0011] The product obtained by the oxidative cyclization reaction is then metallated with [Cp*RhCl2]2 to finally obtain a trivalent rhodium covalent organic framework catalyst;

[0012]

[0013] Wherein, R is p-trifluoromethylphenyl.

[0014] Preferably, it is prepared by the following steps:

[0015] Step 1: In a 10 mL ampoule, 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene represented by formula (Ⅰ) and 2,2'-bipyridine-5,5'-dicarboxaldehyde represented by formula (Ⅱ) are mixed uniformly in an organic solvent; the uniformly mixed mixture in the ampoule is then ultrasonically treated and then acetic acid is added; the reaction is carried out under the catalysis of acetic acid, and the reaction mixture is degassed; after the ampoule is sealed, it is allowed to stand in an oven at 120° C. for 72 hours; the solid obtained by the reaction is washed with tetrahydrofuran and acetone respectively and then vacuum dried at 80° C. to obtain orange powder Bpy-COF;

[0016] Step 2: Add Bpy-COF, tetrachlorobenzoquinone, p-trifluoromethylphenylacetylene, boron trifluoride etherate and toluene into a 25 mL Schlenk tube; seal the Schlenk tube and react in an argon environment. After the reaction is completed, add a saturated NaHCO3 solution to quench the reaction, filter and separate the solid residue, and wash with N,N-dimethylformamide, water and methanol respectively; the obtained solid is vacuum dried at 80°C to obtain a brown powder Q-COF;

[0017] Step 3: Add Q-COF, [Cp*RhCl2]2 and methanol to a 25 mL Schlenk tube; seal the Schlenk tube and react in an argon environment. After the reaction is completed, filter and separate the precipitate, wash it with methanol and dichloromethane respectively, and then dry the obtained solid in vacuum at 60°C to obtain a dark red powder RhCOF-SYNU-1.

[0018] Preferably, the molar ratio of 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene to 2,2'-bipyridine-5,5'-dicarbaldehyde is 1:(0.5-2).

[0019] Preferably, the organic solvent in step 1 is 1,4-dioxane and mesitylene, and the volume ratio thereof is 1:(0.5-1).

[0020] Preferably, the amount of acetic acid used in step 1 is 3 to 10 times the molar amount of 2,2'-bipyridine-5,5'-dicarbaldehyde.

[0021] Preferably, the molar ratio of the theoretical imine bond of Bpy-COF to p-trifluoromethylphenylacetylene, tetrachlorobenzoquinone, and boron trifluoride etherate is 1:(1-1.5):1.2:(0.5-1).

[0022] Preferably, the theoretical molar ratio of bipyridine to [Cp*RhCl2]2 of Q-COF is 1:(0.5-1).

[0023] Preferably, the reaction temperature involved in steps 1-3 is 70-120°C.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] Based on a reasonable molecular design, this method uses organic small molecule monomers to sequentially carry out acetic acid-catalyzed Schiff base condensation reaction, oxidative cyclization reaction and trivalent rhodium metallization process, and successfully prepares a covalent organic framework with extended π-conjugated system, excellent stability and atomic-level dispersed trivalent rhodium active center. This covalent organic framework can be used for heat-driven or light-driven trivalent rhodium catalytic regioselective C(sp 2 )-H bond functionalization reaction to achieve regioselective C(sp 2 Efficient recycling in )-H bond functionalization.

[0026] The trivalent rhodium covalent organic framework catalyst synthesized by the present invention has high crystallinity, good stability, an extended π-conjugated system and trivalent rhodium active centers dispersed at the atomic level, and can be used to catalyze regioselective C(sp 2 )-H bond functionalization reaction to achieve rapid recovery and reuse of trivalent rhodium.

[0027] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 is a powder X-ray (PXRD) pattern of RhCOF-SYNU-1 synthesized in the present invention;

[0031] Figure 2 is a Fourier transform infrared spectrum (FT-IR) of RhCOF-SYNU-1 synthesized in the present invention;

[0032] Figure 3 is a thermogravimetric analysis (TGA) curve of RhCOF-SYNU-1 synthesized in the present invention;

[0033] Figure 4 The solid nuclear magnetic resonance spectrum (ssNMR) of RhCOF-SYNU-1 synthesized in the present invention;

[0034] Figure 5 This is a scanning transmission electron microscope (STEM) image of RhCOF-SYNU-1 synthesized in the present invention;

[0035] Figure 6 This is an ultraviolet visible diffuse reflectance spectrum (UV-Vis) of RhCOF-SYNU-1 synthesized in the present invention. DETAILED DESCRIPTION

[0036] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are merely examples of methods consistent with some aspects of the present invention as detailed in the appended claims.

[0037] Example 1: Preparation of trivalent rhodium covalent organic framework catalyst

[0038] The preparation method of trivalent rhodium covalent organic framework catalyst comprises the following specific steps:

[0039] (1) In a 10 mL glass ampoule, 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene (85 mg, 0.15 mmol) and 2,2'-bipyridine-5,5'-dicarboxaldehyde (64 mg, 0.3 mmol) were mixed in an organic solvent of 1,4-dioxane (1.5 mL) and mesitylene (1.5 mL). After the mixture in the ampoule was ultrasonically treated for 30 minutes, 0.5 mL of 3M acetic acid aqueous solution was added and the reaction mixture was degassed. After the ampoule was sealed, it was placed in an oven at 120°C for 72 hours. After the reaction was completed, the precipitate was separated by filtration and washed with tetrahydrofuran (3×20 mL) and acetone (3×20 mL). The obtained powder was vacuum dried at 80°C for 12 hours to obtain orange powder Bpy-COF (135 mg).

[0040] (2) Add Bpy-COF (24 mg) prepared in step (1) and tetrachlorobenzoquinone (0.05 mmol, 12 mg) to a 25 mL Schlenk tube, and then add trifluoromethylphenylacetylene (0.12 mmol, 20 mg), boron trifluoride etherate (0.1 mmol, 14 mg) and toluene (5 mL). The Schlenk tube was sealed and reacted at 110 ° C for 72 h in an argon environment. After cooling to room temperature, the reaction was quenched with saturated NaHCO3. The solid residue was separated by filtration and washed with N, N-dimethylformamide (3×10 mL), water (3×10 mL) and methanol (3×10 mL), respectively. Then, the obtained solid was vacuum dried at 80 ° C for 12 h to obtain a brown powder Q-COF (39 mg).

[0041] (3) Q-COF (41 mg) prepared in step (2) and [Cp*RhCl2]2 (0.2 mmol, 12 mg) were added to a 25 mL Schlenk tube, followed by methanol (5 mL). The mixture was stirred at 70 °C for 24 h in an argon environment. After the reaction was completed, the precipitate was separated by filtration and washed with methanol (3 × 10 mL) and dichloromethane (3 × 10 mL), respectively. The resulting solid was then vacuum dried at 60 °C for 12 h to obtain a dark red powder RhCOF-SYNU-1 (43 mg).

[0042] Example 2: Structural Characterization of Covalent Organic Framework Material RhCOF-SYNU-1

[0043] 1. PXRD spectrum

[0044] like Figure 1 The powder X-ray diffraction (PXRD) spectrum of the covalent organic framework material RhCOF-SYNU-1 was collected on a powder X-ray diffractometer (Cu Kα radiation source, Ultima IV, Rigaku, Japan). The spectrum scanning range is 1.5° to 40°, and the scanning speed is 4° / min. In the above spectrum, the sharp diffraction peaks at 3.16°, 4.58°, 6.38°, 9.74°, 12.98°and 23.86° are respectively attributed to the (110) crystal plane, (020) crystal plane, (220) crystal plane, (330) crystal plane, (440) crystal plane and (001) crystal plane. The above spectrum results show that the covalent organic framework has a high degree of crystallinity.

[0045] 2. FT-IR spectrum

[0046] like Figure 2The Fourier transform infrared (FT-IR) spectrum of the covalent organic framework material RhCOF-SYNU-1 was acquired on a Fourier transform infrared spectrometer (Bruker IFS). The spectrum scanning range was 400 cm -1 -4000cm -1 , the scanning speed is 66v / s. -1 The stretching vibration peak of the quinoline ring in RhCOF-SYNU-1 appears at 1325 cm -1 The above spectrum results confirm the successful synthesis of the covalent organic framework.

[0047] 3.TGA spectrum

[0048] like Figure 3 The thermogravimetric analysis (TGA) spectrum of the covalent organic framework material RhCOF-SYNU-1 was acquired on a thermogravimetric analyzer (STA449 F5 / QMS 403D). The scanning range of the spectrum was 30℃~800℃, and the scanning speed was 10℃ / min. The spectrum showed that the thermal decomposition temperature of the material was higher than 350℃, proving that the covalent organic framework has excellent thermal stability.

[0049] 4. 13 C CP / MAS NMR spectrum

[0050] like Figure 4 , the solid phase of the covalent organic framework RhCOF-SYNU-1 ( 13 The C CP / MAS NMR spectrum was acquired on a solid NMR spectrometer (Bruker AvanceⅢ400MHz). The spectrum shows that the carbon signal attributed to C=N disappears clearly at δ=156.9ppm, proving the successful conversion of the imine bond. The two signals generated at δ=98.1ppm and δ=9.2ppm in RhCOF-SYNU-1 are respectively attributed to the C directly connected to Rh and the methyl C on the Cp* ring. The above results indicate the successful synthesis of the covalent organic framework and the successful loading of Rh(III).

[0051] 5. STEM images

[0052] like Figure 5 The scanning transmission electron microscope (STEM) image of the covalent organic framework RhCOF-SYNU-1 was captured on a microscope (JEOL 2100FCS) at an accelerating voltage of 200 kV. In this image, it can be clearly observed that the trivalent rhodium active centers are uniformly dispersed in the covalent organic framework at the atomic level.

[0053] 6.UV-Vis spectrum

[0054] like Figure 6 The UV-Vis diffuse reflectance spectrum (UV-Vis) of the covalent organic framework RhCOF-SYNU-1 was acquired using a Hitachi (UH4150) spectrophotometer. The spectrum scan range was 200-800nm, and the scanning speed was v=200nm / min. The spectrum showed that the material had a high absorbance in the visible light region of 400-600nm.

[0055] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The specification and examples are to be considered exemplary only, and the true scope and spirit of the present invention are indicated by the following claims.

[0056] It should be understood that the present invention is not limited to what has been described above and that various modifications and changes may be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for synthesizing a trivalent rhodium covalent organic framework catalyst, characterized in that: include: The Schiff base condensation reaction of 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene and 2,2'-bipyridine-5,5'-dicarboxaldehyde was carried out; The product obtained by the Schiff base condensation reaction is subjected to an oxidative cyclization reaction with p-trifluoromethylphenylacetylene; The product obtained by the oxidative cyclization reaction is then metallated with [Cp*RhCl2]2 to finally obtain a trivalent rhodium covalent organic framework catalyst; Wherein, R is p-trifluoromethylphenyl.

2. A method for synthesizing a trivalent rhodium covalent organic framework catalyst according to claim 1, characterized in that, Prepared by the following steps: Step 1: In a 10 mL ampoule, 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene represented by formula (Ⅰ) and 2,2'-bipyridine-5,5'-dicarboxaldehyde represented by formula (Ⅱ) are mixed uniformly in an organic solvent; the uniformly mixed mixture in the ampoule is then ultrasonically treated and then acetic acid is added; the mixture is reacted under the catalysis of acetic acid, and the reaction mixture is degassed; after the ampoule is sealed, it is allowed to stand in an oven at 120° C. for 72 hours; the solid obtained by the reaction is washed with tetrahydrofuran and acetone respectively and then vacuum dried at 80° C. to obtain orange powder Bpy-COF; Step 2: Add Bpy-COF, tetrachlorobenzoquinone, p-trifluoromethylphenylacetylene, boron trifluoride etherate and toluene into a 25 mL Schlenk tube; seal the Schlenk tube and react in an argon environment. After the reaction is completed, add a saturated NaHCO3 solution to quench the reaction, filter and separate the solid residue, and wash with N,N-dimethylformamide, water and methanol respectively; the obtained solid is vacuum dried at 80°C to obtain a brown powder Q-COF; Step 3: Add Q-COF, [Cp*RhCl2]2 and methanol to a 25 mL Schlenk tube; seal the Schlenk tube and react in an argon environment. After the reaction is completed, filter and separate the precipitate, wash it with methanol and dichloromethane respectively, and then dry the obtained solid in vacuum at 60°C to obtain a dark red powder RhCOF-SYNU-1.

3. A method for synthesizing a trivalent rhodium covalent organic framework catalyst according to claim 2, characterized in that: The molar ratio of the 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene to the 2,2'-bipyridine-5,5'-dicarbaldehyde is 1:(0.5-2).

4. A method for synthesizing a trivalent rhodium covalent organic framework catalyst according to claim 2, characterized in that: The organic solvent in step 1 is 1,4-dioxane and mesitylene, and the volume ratio thereof is 1:(0.5-1).

5. A method for synthesizing a trivalent rhodium covalent organic framework catalyst according to claim 2, characterized in that: The amount of acetic acid used in step 1 is 3 to 10 times the molar amount of 2,2'-bipyridine-5,5'-dicarbaldehyde.

6. A method for synthesizing a trivalent rhodium covalent organic framework catalyst according to claim 2, characterized in that: The molar ratio of the theoretical imine bond of Bpy-COF to trifluoromethylphenylacetylene, tetrachlorobenzoquinone, and boron trifluoride etherate is 1:(1-1.5):1.2:(0.5-1).

7. A method for synthesizing a trivalent rhodium covalent organic framework catalyst according to claim 2, characterized in that: The theoretical molar ratio of bipyridine to [Cp*RhCl2]2 of Q-COF is 1:(0.5~1).

8. A method for synthesizing a trivalent rhodium covalent organic framework catalyst according to claim 2, characterized in that: The reaction temperature involved in steps 1-3 is 70 to 120°C.

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