Preparation method and application of nanosheet layered urotropine-zinc / cobalt MOFs catalyst
A nanosheet-layered hexamethylenetetramine-zinc/cobalt MOF catalyst was prepared by post-synthesis. By utilizing the coordination effect of cobalt ions with the nanosheet-layered hexamethylenetetramine-zinc MOF, the selectivity and efficiency problems of catalysts in the β-alkylation reaction of aromatic primary alcohols to secondary alcohols were solved, and high-efficiency catalytic performance was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-18
- Publication Date
- 2026-03-17
AI Technical Summary
Existing technologies lack sufficient catalyst selectivity and efficiency in the β-alkylation reaction of aromatic primary alcohols and secondary alcohols, making it difficult to meet the requirements for high-efficiency conversion.
A nanosheet-layered hexamethylenetetramine-zinc/cobalt MOF catalyst was prepared by a post-synthesis method. By introducing cobalt ions into the nanosheet-layered hexamethylenetetramine-zinc MOF, stable nanosheet-layered hexamethylenetetramine-zinc/cobalt MOFs were formed by utilizing the coordination effect of tertiary amine functional groups.
It significantly improves the catalytic activity and selectivity of the β-alkylation reaction of aromatic primary alcohols and secondary alcohols, provides a basis for the application of efficient catalysts, and lays the foundation for the application of multi-metal MOF catalysts in organic industrial reactions.
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Figure CN117943124B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of functional materials and catalysts, specifically relating to a method for preparing a post-synthetic nanosheet layered hexamethylenetetramine-zinc / cobalt MOF catalyst for the β-alkylation reaction of aromatic primary alcohols and secondary alcohols, and its application. Background Technology
[0002] Primary-secondary alcohol β-alkylation is an organic chemical reaction involving the conversion of a primary alcohol (first-order alcohol) into a secondary alcohol (second-order alcohol). This conversion is achieved through alkylation at the primary alcohol molecule. Typically, alkylation involves introducing an alkyl group (such as methyl, ethyl, etc.) into an organic molecule to alter its chemical properties or increase its stereochemical diversity. In primary-secondary alcohol β-alkylation, the alkyl group is introduced into the β-position of the primary alcohol molecule, immediately adjacent to the hydroxyl group. This reaction can be carried out using various methods, the most common being the use of electrophilic alkylating agents (such as haloalkanes, alkenes, etc.). In the reaction, the electrophilic alkylating agent undergoes a substitution reaction with the primary alcohol, introducing the alkyl group into the β-position to generate the secondary alcohol product. Primary-secondary alcohol β-alkylation is an important organic synthetic reaction that can be used to synthesize various organic compounds, such as pharmaceuticals, fragrances, and natural products. The selectivity and efficiency of this reaction are often influenced by the electronic and steric effects of the alkyl group, thus requiring careful design of reaction conditions and selection of appropriate reagents to achieve the desired product conversion.
[0003] Metal-organic frameworks (MOFs) are crystalline materials formed by coordination bonds between metal ions or clusters and organic linkers. MOFs typically possess highly tunable pore structures and surface functionalities, thus holding broad application potential in catalysis. Multimetal MOF catalysts refer to MOF materials containing two or more metal ions or clusters. These catalysts exhibit advantages in terms of higher activity, selectivity, and stability compared to single-metal catalysts because the interactions between multiple metals can synergistically promote catalytic reactions. The synthesis of multimetal MOF catalysts mainly includes two approaches: precursor synthesis and post-synthesis. Precursor synthesis involves reacting metal ions or clusters with organic linkers in solution to generate MOFs. This method typically requires precise control of reaction conditions and precursor ratios to ensure the synthesis of multimetal MOFs. Post-synthesis methods, on the other hand, form multimetal MOFs by modifying already synthesized single-metal MOF catalysts. This method can be achieved through metal ion exchange or doping. This approach allows for flexible adjustment of the composition and performance of multimetal MOF catalysts. Multimetallic MOF catalysts have demonstrated excellent catalytic activity in many fields, such as organic synthesis, gas separation, and energy conversion. Their research is of great significance for advancing catalysis science and its applications in the field of sustainable development. Summary of the Invention
[0004] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.
[0005] In view of the problems existing in the above and / or prior art, the present invention is proposed.
[0006] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing nanosheet layered hexamethylenetetramine-zinc / cobalt MOFs by post-synthetic synthesis of aromatic primary alcohol-secondary alcohol β-alkylation reaction.
[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for preparing nanosheet-like layered hexamethylenetetramine-zinc / cobalt MOFs by post-synthetic reaction of aromatic primary alcohols-secondary alcohols β-alkylation, characterized in that it includes:
[0008] Hexamethylenetetramine was dissolved in chloroform and then poured into a solution of zinc nitrate hexahydrate that had been dissolved in methanol. After stirring the mixture, nanosheet-like hexamethylenetetramine-zinc MOFs were obtained.
[0009] A methanol solution of cobalt acetate tetrahydrate was added dropwise to a methanol solution of nanosheet layered hexamethylenetetramine-zinc MOFs, and the mixture was stirred continuously. The resulting product was dried to obtain nanosheet layered hexamethylenetetramine-zinc / cobalt MOFs.
[0010] In a preferred embodiment of the preparation method described in this invention, the preparation of the nanosheet layered hexamethylenetetramine-zinc MOFs involves 8.0 mmol of hexamethylenetetramine, 1.6 mmol of zinc nitrate hexahydrate, 20 ml of chloroform, and 20 ml of methanol.
[0011] In a preferred embodiment of the preparation method described in this invention, the magnetic stirring time for the preparation of the nanosheet layered hexamethylenetetramine-zinc MOFs is 12 h at a speed of 400 r / min.
[0012] In a preferred embodiment of the preparation method described in this invention, the cobalt acetate tetrahydrate in the methanol solution contains 60 mg of cobalt acetate tetrahydrate and 5 ml of methanol solution; the nanosheet layered hexamethylenetetramine-zinc MOFs in the methanol solution contains 260 mg of nanosheet layered hexamethylenetetramine-zinc MOFs and 50 ml of methanol solution.
[0013] As a preferred embodiment of the preparation method described in this invention, the reaction temperature in the preparation of the nanosheet layered hexamethylenetetramine-zinc / cobalt MOFs is 40°C; the drying temperature in the preparation of the nanosheet layered hexamethylenetetramine-zinc / cobalt MOFs is 105°C, and the drying time is 12 h.
[0014] As a preferred embodiment of the preparation method described in this invention, the application of the catalyst product in the β-alkylation of aromatic primary alcohols to secondary alcohols is as follows:
[0015] The nanosheet-layered hexamethylenetetramine-zinc / cobalt MOF catalyst, potassium tert-butoxide, secondary alcohol, primary alcohol, and toluene were placed in a 35 ml Schlenk reaction tube. After the conversion of the raw materials reached 100% by GC, the reaction mixture was cooled to room temperature, and then the solvent was removed by rotary evaporation. The product was purified by column chromatography with silica gel as the stationary phase and petroleum ether / dichloromethane in a volume ratio of 1:1 as the mobile phase. The product was then dissolved in deuterated chloroform for nuclear magnetic resonance analysis.
[0016] As a preferred embodiment of the preparation method described in this invention, the nanosheet layered hexamethylenetetramine-zinc / cobalt MOFs catalyst contains 0.01 mmol of zinc, 0.02 mmol of cobalt, 1.4 mmol of potassium tert-butoxide, 2.0 mmol of secondary alcohol, 2.0 mmol of primary alcohol, and 5 ml of toluene.
[0017] As a preferred embodiment of the preparation method described in this invention, the nanosheet layered hexamethylenetetramine-zinc / cobalt MOFs catalyst is reacted in an air atmosphere at a temperature of 110°C during the β-alkylation reaction of aromatic primary alcohols and secondary alcohols.
[0018] Another objective of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a product obtained by post-synthetic nanosheet layered hexamethylenetetramine-zinc / cobalt MOFs catalyst in the β-alkylation reaction of aromatic primary alcohols and secondary alcohols.
[0019] Another objective of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a post-synthetic nanosheet layered hexamethylenetetramine-zinc / cobalt MOFs catalyst for the β-alkylation reaction of aromatic primary alcohols and secondary alcohols, and to apply the product obtained in functional materials and catalysts.
[0020] Beneficial effects of this invention:
[0021] (1) This invention synthesizes nanosheet-layered hexamethylenetetramine-zinc / cobalt MOFs catalysts after the β-alkylation reaction of aromatic primary alcohols and secondary alcohols. This method is carried out after the synthesis of nanosheet-layered hexamethylenetetramine-zinc MOFs, and utilizes the empty orbital coordination ability of nitrogen atoms of tertiary amine functional groups in nanosheet-layered hexamethylenetetramine-zinc MOFs with the transition metal Co. 2+ Ion interaction was used to prepare structurally stable nanosheet layered hexamethylenetetramine-zinc / cobalt MOFs for the β-alkylation reaction of aromatic primary alcohols and secondary alcohols.
[0022] (2) The nanosheet layered hexamethylenetetramine-zinc / cobalt MOFs prepared by coordination in this invention can not only significantly improve the catalytic activity and selectivity of the β-alkylation reaction of primary and secondary alcohols, but also help to further deepen the understanding of the post-synthetic MOF catalyst method.
[0023] (3) This invention will lay the foundation for the application of highly efficient post-synthesized MOFs catalysts in organic industrial reactions and is of great significance for the development of multi-metal MOFs catalysts with wide applications. Attached Figure Description
[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:
[0025] Figure 1 This is a diagram of the nanosheet layered hexamethylenetetramine-zinc single crystal structure of Example 1.
[0026] Figure 2 Example 1: Nanosheet layered hexamethylenetetramine-zinc / cobalt MOFs N 1s XPS characterization.
[0027] Figure 3 The scan images of nanosheet-layered hexamethylenetetramine-zinc / cobalt MOFs in Example 1 at different magnifications (a is 1 μm, b is 200 nm).
[0028] Figure 4 Transmission images of nanosheet-layered hexamethylenetetramine-zinc / cobalt MOFs in Example 1 at different magnifications (a is 100 nm, b is 10 nm).
[0029] Figure 5 The following is a performance comparison diagram between Example 1 and Comparative Examples 1-4: (1) without catalyst, (2) nanosheet layered hexamethylenetetramine-zinc MOFs, and (3) nanosheet layered hexamethylenetetramine-zinc impregnated with Co. 2+ MOFs(4) are nanosheet-layered hexamethylenetetramine-zinc coordinated Co 2+ MOFs, (5) are urotropine-zinc acetate coordinated Co 2+ MOFs. Detailed Implementation
[0030] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.
[0031] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.
[0032] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.
[0033] Unless otherwise specified, all raw materials and reagents used in the embodiments of this invention were purchased from Aladdin Reagents.
[0034] Example 1
[0035] a. Preparation of nanosheet layered hexamethylenetetramine-zinc MOFs:
[0036] Urotropin-zinc MOFs were synthesized by solvent diffusion.
[0037] First, hexamethylenetetramine (12.0 mmol) was dissolved in chloroform (20 ml), and then poured into a solution of zinc nitrate hexahydrate (Zn(OAC)₂·2H₂O) (2.1 mmol) already dissolved in methanol (20 ml). The mixture was then stirred for 24 h to obtain nanosheet-like hexamethylenetetramine-zinc MOFs.
[0038] b. Preparation of nanosheet layered hexamethylenetetrahydrate (H2O) zinc / cobalt MOFs: A methanol solution of cobalt acetate tetrahydrate (Co(OAC)2·4H2O) (5 ml, 60 mg) was added dropwise to a methanol solution of nanosheet layered hexamethylenetetrahydrate (H2O) zinc / cobalt MOFs (50 ml, 260 mg) while stirring continuously. The resulting product was dried at 105 °C for 12 h to obtain nanosheet layered hexamethylenetetrahydrate (H2O) zinc / cobalt MOFs.
[0039] Example 2
[0040] Catalytic performance of nanosheet-layered hexamethylenetetramine-zinc / cobalt MOFs in the β-alkylation reaction of aromatic primary and secondary alcohols:
[0041] Nanosheet layered hexamethylenetetramine-zinc / cobalt MOF catalyst (0.01 mmol, 0.02 mmol), potassium tert-butoxide (t-BuOK) (1.4 mmol), secondary alcohol (2.0 mmol), primary alcohol (2.0 mmol), and toluene (5 ml) were placed in a 35 ml Schlenk reaction tube and reacted in air at 110 °C. After the reaction was complete (the conversion of the starting material was 100% as determined by GC), the reaction mixture was cooled to room temperature, and the solvent was removed by rotary evaporation. Purification was performed by column chromatography with silica gel as the stationary phase and petroleum ether / dichloromethane at a volume ratio of 1:1 as the mobile phase. The obtained product was dissolved in deuterated chloroform (CDCl3) for NMR analysis.
[0042] Depend on Figure 1 As can be seen from the data on hexamethylenetetramine-zinc crystals, each symmetric unit contains one zinc ion, six coordinated water molecules, and six hexamethylenetetramine molecules linked by NH…O hydrogen bonds. The uncoordinated imine functional groups in hexamethylenetetramine can further interact with Co… 2+ Ions undergo coordination to form hexamethylenetetramine-zinc / cobalt MOF catalysts.
[0043] Depend on Figure 2 It can be seen from the N1s XPS characterization of the layered hexamethylenetetramine-zinc / cobalt MOFs that the binding energy at 399.4 eV is attributed to the uncoordinated imine functional group in hexamethylenetetramine and the Co in Co(OAC)2·4H2O. 2+CN-Co chemical bonds formed by ionic interactions. The successful synthesis of hexamethylenetetramine-zinc / cobalt MOF can be directly confirmed by N1s XPS characterization.
[0044] Depend on Figure 3 As can be seen from the scan images at different magnifications, the hexamethylenetetramine-zinc / cobalt MOFs prepared based on coordination interactions exhibit a nanosheet-like structure. This nanosheet-like structure has a large specific surface area, which is beneficial for improving adsorption and catalytic activity.
[0045] Depend on Figure 4 As can be seen from the transmission images of hexamethylenetetramine-zinc / cobalt MOFs at different magnifications, hexamethylenetetramine-zinc / cobalt MOFs are formed by very thin nanosheets. This is beneficial to enhancing the mass transfer capacity of the reactants 1-phenylethanol or benzyl alcohol in the primary-secondary alcohol β-alkylation reaction, thereby improving the catalytic conversion rate and selectivity.
[0046] Comparative Example 1
[0047] The difference from Example 1 is that no catalyst was added during the catalytic performance test.
[0048] Comparative Example 2
[0049] The difference from Example 1 is that the nanosheet layered hexamethylenetetramine-zinc MOFs were used as catalysts to test the β-alkylation reaction of aromatic primary alcohols to secondary alcohols, which is consistent with the process of the nanosheet layered hexamethylenetetramine-zinc / cobalt MOFs in the β-alkylation reaction of aromatic primary alcohols to secondary alcohols.
[0050] Comparative Example 3
[0051] A nanosheet-layered hexamethylenetetramine-zinc / cobalt MOF catalyst was prepared using a conventional impregnation method. The preparation process involved an impregnation method: a methanol solution (6 ml, 60 mg) of cobalt acetate tetrahydrate (Co(OAC)₂·4H₂O) was impregnated three times onto 260 mg of nanosheet-layered hexamethylenetetramine-zinc MOF solid powder. After each impregnation, the powder was dried at 105 °C for 1 h, and then the next impregnation process was repeated. After three impregnations, the resulting product was dried at 105 °C for 12 h to obtain the nanosheet-layered hexamethylenetetramine-zinc / cobalt MOFs prepared by the conventional impregnation method.
[0052] Comparative Example 4
[0053] Urotropine-zinc acetate MOFs were prepared using zinc acetate dihydrate (Zn(OAC)2·2H2O) as the zinc source;
[0054] a. First, dissolve urotropine (25.0 mmol) in chloroform (30 ml), then pour it into a solution of zinc acetate dihydrate (4.1 mmol) already dissolved in methanol (40 ml). The mixture is then stirred for 24 hours to obtain urotropine-zinc acetate MOFs.
[0055] b. Preparation of urotropine-zinc acetate / cobalt MOFs: A methanol solution of cobalt acetate tetrahydrate (Co(OAC)₂·4H₂O) (10 ml, 60 mg) was added dropwise to a methanol solution of urotropine-zinc acetate / cobalt MOFs (50 ml, 260 mg) while stirring continuously. The resulting product was dried at 105 °C for 12 h to obtain urotropine-zinc acetate / cobalt MOFs.
[0056] Depend on Figure 5 As can be seen from the catalyst performance structure, Comparative Example 1, without adding a catalyst or using only hexamethylenetetramine-zinc MOFs as a catalyst, did not show any catalytic performance in the entire reaction, indicating that cobalt ions are the active center of the primary-secondary alcohol β-alkylation reaction. Examples 1 and Comparative Examples 2-3 show that the 1-phenylethanol conversion of the primary-secondary alcohol β-alkylation reaction catalyzed by the post-synthesis method using hexamethylenetetramine-zinc / cobalt MOFs is 97%, and the selectivity of the product 1,3-diphenylprop-1-ol is 99%, significantly higher than the 41% 1-phenylethanol conversion and 75% 1,3-diphenylprop-1-ol selectivity of hexamethylenetetramine-zinc / cobalt MOFs prepared by the traditional impregnation method. The crystal structure in Comparative Example 4 is different from that in Example 1; the crystal structure of Example 1 is a single crystal, and as can be seen from the figure, the performance of Example 1 is better. The above catalytic performance results show that the hexamethylenetetramine-zinc / cobalt MOFs prepared by the post-synthetic coordination method can efficiently catalyze the β-alkylation reaction of primary alcohols and secondary alcohols, which provides a reference for the application of post-synthetic MOF catalysts in organic industrial reactions.
[0057] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.
Claims
1. A method for preparing a nanosheet layered urotropine-zinc / cobalt MOFs catalyst, characterized by: Comprising, The methanol solution of the nano-sheet layered urotropine-zinc MOFs is prepared by dissolving urotropine in chloroform, then pouring the solution into the methanol solution of zinc nitrate hexahydrate, and then stirring the mixed solution to obtain the nano-sheet layered urotropine-zinc MOFs; The methanol solution of the nano-sheet layered urotropine-zinc / cobalt MOFs is prepared by adding the methanol solution of cobalt acetate tetrahydrate into the methanol solution of the nano-sheet layered urotropine-zinc MOFs, and continuously stirring the obtained product to obtain the nano-sheet layered urotropine-zinc / cobalt MOFs after drying; In the preparation of the nano-sheet layered urotropine-zinc MOFs, urotropine is 12.0 mmol, zinc nitrate hexahydrate is 2.1 mmol, chloroform is 20 ml, and methanol is 20 ml; In the preparation of the nano-sheet layered urotropine-zinc MOFs, the stirring time is 12 h, and the stirring speed is 400 r / min; In the preparation of the nano-sheet layered urotropine-zinc / cobalt MOFs, the reaction temperature is 40℃; in the preparation of the nano-sheet layered urotropine-zinc / cobalt MOFs, the drying temperature is 80℃, and the drying time is 12 h.
2. The production method according to claim 1, characterized by: In the methanol solution of the cobalt acetate tetrahydrate, the cobalt acetate tetrahydrate is 180 mg, and the methanol solution is 5 ml; in the methanol solution of the nano-sheet layered urotropine-zinc MOFs, the nano-sheet layered urotropine-zinc MOFs is 260 mg, and the methanol solution is 50 ml.
3. The nano-sheet layered urotropine-zinc / cobalt MOFs catalyst prepared by the preparation method of claims 1-2.
4. The application of the nano-sheet layered urotropine-zinc / cobalt MOFs catalyst in the β-alkylation of aromatic primary alcohol-secondary alcohol, according to claim 3.
5. The use according to claim 4, characterized in that: Comprising, The nano-sheet layered urotropine-zinc / cobalt MOFs catalyst, potassium tert-butoxide, secondary alcohol, primary alcohol, and toluene are mixed, and after the raw material conversion rate reaches 100%, the reaction mixture is cooled to room temperature, then rotary evaporation is carried out at 60℃ and 100 r / min, followed by vacuum distillation, and purification is carried out by column chromatography, the stationary phase is silica gel, and the mobile phase is petroleum ether / dichloromethane with a volume ratio of 1:1, after obtaining the product, it is dissolved in deuterated chloroform for nuclear magnetic resonance analysis.
6. The use according to claim 4, wherein: The nano-sheet layered urotropine-zinc / cobalt MOFs catalyst in the β-alkylation of aromatic primary alcohol-secondary alcohol is carried out in an air atmosphere at a temperature of 110℃.