Preparation method of metal nanocluster confinement covalent organic framework composite material

Abstract

The invention belongs to the technical field of nano composite materials, and discloses a preparation method of a metal nanocluster confinement covalent organic framework composite.The method comprises the steps that firstly, a nanosecond pulse laser liquid phase is adopted for ablating a metal target material, secondary laser irradiation is conducted on obtained dispersion liquid at low temperature, and a metal nanocluster colloidal solution is prepared; and then, adding an aldehyde precursor and an amine precursor of a covalent organic framework into the colloidal solution, and carrying out mixing, standing polymerization reaction, washing and drying to obtain the final composite material. According to the method, an exogenous chemical reducing agent does not need to be used, and synchronous and uniform confinement packaging of the metal nanoclusters in the covalent organic framework pore channel generation process is achieved through an in-situ polymerization strategy. The prepared composite material has high dispersibility and high activity of the metal cluster and structural integrity and confinement stability of a carrier material, and has a good application prospect in the field of heterogeneous catalysis.

Description

Technical Field

[0001] This application belongs to the field of nanocomposite materials technology, specifically relating to a method for preparing a metal nanocluster confined covalent organic framework composite material. Background Technology

[0002] Covalent organic frameworks (COFs) are a class of crystalline porous polymers formed by light elements linked by strong covalent bonds. They possess well-defined pore structures, high specific surface areas, excellent structural tunability, and chemical stability, showing significant potential in heterogeneous catalysis, adsorption separation, and energy storage. In particular, their regular nanopores provide an ideal support for loading active catalytic species and achieving spatial confinement.

[0003] Metal nanoclusters, typically referring to aggregates of metal atoms smaller than 2 nanometers, often exhibit superior activity in heterogeneous catalysis compared to traditional nanoparticles due to their extremely high atomic utilization, unique electronic structure, and abundant active sites. However, the extremely high surface energy of metal nanoclusters makes them prone to migration and aggregation during preparation and application, leading to decreased activity or even deactivation, thus limiting their practical application. Stably encapsulating metal nanoclusters within the pores of COFs, utilizing the rigid pore walls of COFs for physical confinement, is an effective strategy to suppress aggregation and improve catalytic stability and recyclability.

[0004] Currently, the mainstream method for preparing metal species / COF composites is the "post-adsorption-reduction" strategy. This involves first synthesizing complete COF crystals, then impregnating and adsorbing a metal precursor (usually a metal salt) into the pores of the COF, and finally converting the metal ions into zero-valent metal nanoparticles through chemical or thermal reduction. However, the subsequent introduction of chemical reducing agents (such as sodium borohydride or hydrazine hydrate) may damage the chemical bonds (such as imine bonds) of the COF framework, affecting its crystallinity and structural integrity. Secondly, the impregnation process offers limited control over the distribution of the metal precursor within the pores, and during the subsequent reduction process, metal atoms easily migrate and aggregate outside the pores or at the pore openings, resulting in uneven metal particle size and dispersed distribution, making it difficult to achieve uniform, site-specific confinement of metal clusters within the bulk pores of the COF. Furthermore, this method is cumbersome, and the controllability of metal loading and cluster size is poor.

[0005] Therefore, there is an urgent need in this field to develop a method for preparing metal nanoclusters that can be uniformly and stably confined within the pores of COFs without damaging the COFs framework structure. Summary of the Invention

[0006] To address the shortcomings of existing technologies, such as reliance on chemical reducing agents, uneven metal distribution, and easy damage to the COF framework, this application provides a method for preparing metal nanocluster confined covalent organic framework composite materials. By directly mixing a laser-prepared metal nanocluster colloidal solution with a COF precursor and performing in-situ polymerization, the metal clusters are synchronously and uniformly encapsulated during the COF channel formation process, thereby avoiding the use of exogenous reducing agents and obtaining a composite material with highly dispersed metals and a complete structure.

[0007] To achieve the above technical objectives, this application specifically adopts the following technical solution: In one aspect of this application, a method for preparing a metal nanocluster confined covalent organic framework composite material is provided, comprising the following steps: S1. Preparation of metal nanocluster colloidal solution: A metal target placed in a solvent is bombarded with a first nanosecond pulsed laser to obtain a metal nanocluster mother liquor; subsequently, the metal nanocluster mother liquor is irradiated a second time with a second nanosecond pulsed laser at an ambient temperature of -20 to 10°C to obtain a metal nanocluster colloidal solution; wherein, the wavelength of the first nanosecond pulsed laser is 1064 nm and the flux is 1~2 Jpulse. -1 cm -2 The flux of the second nanosecond pulsed laser is 0.1~2 Jpulse. -1 cm -2 ; S2. Preparation of in-situ confined composite material: The aldehyde precursor and amine precursor of the covalent organic framework are added to the colloidal solution of the metal nanoclusters and mixed to form a reaction system. The static polymerization reaction is carried out at 120°C. After the reaction is completed, the obtained solid product is washed and dried to obtain the metal nanocluster confined covalent organic framework composite material.

[0008] In one embodiment, the time for the first nanosecond pulse laser to bombard the metal target is 1 to 20 minutes; the time for the second irradiation is 1 to 10 minutes.

[0009] In one embodiment, the solvent is selected from water, n-butanol, ethanol, dimethyl sulfoxide, N,N-dimethylformamide, and dioxane.

[0010] In one embodiment, the metal element of the metal target is selected from at least one of Pt, Pd, Au, Fe, Co and Ni.

[0011] In one embodiment, the amounts of the aldehyde precursor and the amine precursor are such that the ratio of the total molar number of aldehyde groups to the total molar number of amino groups is 1:1.

[0012] In one embodiment, the aldehyde precursor is selected from one of trialdehyde phloroglucinol, 2-hydroxy-1,3,5-benzyltricarboxaldehyde, and 2,4-dihydroxy-1,3,5-pyromellitic tricarboxaldehyde.

[0013] In one embodiment, the amine precursor is selected from p-phenylenediamine, o-phenylenediamine, m-phenylenediamine, o-toluenediamine, 2,5-diaminobenzonitrile, 2,5-diaminop-benzonitrile, 2-fluoro-1,4-phenylenediamine, 2-chloro-1,4-p-phenylenediamine, 2-bromo-1,4-diaminobenzene, 2-iodo-1,4-phenylenediamine, 2,5-dimethyl-1,4-phenylenediamine, 2-chloro-5-methyl-1,4-phenylenediamine, 2,5-dichlorop-phenylenediamine, 2,5-dichlorop-phenylenediamine, 2, 5-Difluoro-p-phenylenediamine, 2,5-dibromo-p-phenylenediamine, 2,5-diaminophenyl-1,4-diphenol, 1,4-diamino-2,5-divinylbenzene, 2,6-diynyl-p-phenylenediamine, 3,4-difluoro-o-phenylenediamine, 2,3-diaminofluorobenzene, 5-bromo-3-fluoro-1,2-phenylenediamine, 1,2-diamino-3,5-difluorobenzene, 4-bromo-3-fluoro-1,2-phenylenediamine, 3,4,5,6-tetrafluorophenyl-1,2-diamine, 3, 4,5-Trifluoro-1,2-diaminobenzene, 4-chloro-6-fluoro-o-phenylenediamine, 5-chloro-3-methyl-1,2-phenylenediamine, 5-bromo-3,4-dimethylphenyl-1,2-diamine, 4-bromo-3-toluene-1,2-diamine, 3,4-dimethyl-o-phenylenediamine, 3,5-dimethyl-1,2-phenylenediamine, 5-bromo-3-methylphenyl-1,2-diamine, 2,3-diaminotoluene, 2,4-diaminofluorobenzene, 4,6-difluorobenzene-1,3 One of the following: 2,4,5-trifluoro-1,3-phenylenediamine, 4-bromo-6-fluorophenyl-1,3-diamine, 2-chloro-4-fluoro-1,3-phenylenediamine, 2-fluoro-4-bromo-1,3-phenylenediamine, 2,4-diaminotoluene, 2,6-diaminotoluene, 2,4,6-trimethyl-1,3-phenylenediamine, 2,4-dimethylphenyl-1,3-diamine, 2,4-dimethyl-1,5-phenylenediamine, and 2-methoxyphenyl-1,4-diamine.

[0014] In one embodiment, the metal nanocluster content in the mother liquor is 0.1-50 mg / mL.

[0015] In one embodiment, an acidic catalyst and a boiling point organic solvent are added to the reaction system as crystallization regulators, wherein the acidic catalyst is a 6 M aqueous solution of acetic acid, and the high-boiling point organic solvent is mesitylene or o-dichlorobenzene.

[0016] In another aspect of this application, a metal nanocluster confined covalent organic framework composite material prepared by the above preparation method is provided.

[0017] In one embodiment, the metal nanoclusters are no larger than 2 nm in size and are uniformly dispersed within the pores of the covalent organic framework.

[0018] In another aspect of this application, the application of the metal nanocluster confined covalent organic framework composite material in heterogeneous catalytic reactions is provided.

[0019] The beneficial effects of this application are as follows: 1. This application uses laser liquid phase ablation and secondary irradiation technology to directly prepare metal nanocluster colloids, avoiding the potential damage to sensitive chemical bonds (such as imine bonds) in the COFs framework caused by the metal salt reduction step in traditional processes, thus ensuring the crystallization integrity and structural stability of the composite material.

[0020] 2. By directly mixing and in-situ polymerizing pre-synthesized metal nanoclusters with COFs monomers, the metal clusters were simultaneously encapsulated during the COFs pore growth process. This ensured that the metal species were effectively confined inside the pores and evenly distributed, inhibiting migration and aggregation during subsequent processing and use, and improving the catalytic stability of the material.

[0021] The method has a simple process flow, does not require the introduction of surfactants or additional reducing agents, produces high-purity products, and is applicable to the composite preparation of various metals and COFs with different topological structures, making it highly versatile.

[0022] 4. In the prepared composite material, the metal nanoclusters are confined in the regular channels of COFs in a state of small size and high dispersion. This unique "bulk confinement" structure is conducive to exposing more active sites, and can achieve high activity and high durability simultaneously in heterogeneous catalytic reactions. Attached Figure Description

[0023] Figure 1 This is a high-resolution transmission electron microscope (HRTEM) image of the Pt@COF1 Pt nanocluster confined COF composite material prepared in Example 1 of this application; Figure 2 XPS and ATR-FTIR spectra of Pt@COF1 prepared in Example 1 of this application; wherein, a is the X-ray photoelectron spectrum (XPS) of Pt@COF1, and b is the Fourier transform infrared spectrum (ATR-FTIR) of Pt@COF1 prepared in Example 1 and COF1 prepared in Comparative Example 1. Figure 3 Powder X-ray diffraction (PXRD) spectra of Pt@COF1 prepared in Example 1 of this application and COF1 prepared in Comparative Example 1. Detailed Implementation

[0024] The technical solution of this application will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are only some embodiments of this application, not all embodiments, and are only used to illustrate this application, and should not be regarded as limiting the scope of this application. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] This application first utilizes nanosecond pulsed laser liquid-phase ablation and low-temperature secondary irradiation techniques to directly prepare a highly dispersed, ligand-free stable colloidal solution of metal nanoclusters. Subsequently, this colloidal solution is used as a reaction medium and directly mixed with aldehyde and amine precursors of covalent organic frameworks (COFs). During the subsequent thermotropic polymerization reaction, the COF framework simultaneously forms and grows its pores, capturing and encapsulating the pre-dispersed metal nanoclusters in situ within its internal pores. This application avoids the use of exogenous reducing agents and chemical damage to the COF framework, ensuring that metal species are stably confined within the bulk pores of the COFs in a uniform and highly dispersed state, thereby simultaneously achieving efficient utilization and long-term stability of the metal catalytic sites.

[0026] In one specific embodiment, a method for preparing a metal nanocluster confined covalent organic framework composite material is provided, comprising the following steps: S1. Preparation of colloidal solutions of metal nanoclusters Phase 1: Preparation of the mother liquor for metal nanoclusters Pulsed laser liquid-phase ablation was employed. A selected high-purity metal target was immersed in 2-10 mL of solvent. The solvent needed to effectively disperse the laser ablation products and serve as a reaction medium for subsequent covalent organic framework synthesis. A nanosecond pulsed laser with an output wavelength of 1064 nm was used to focus the laser beam onto the surface of the metal target immersed in the solvent. The laser flux was controlled at 1-2 Jpulses. -1 cm -2 At this energy density, the laser pulse acts on the target surface, generating a high-temperature, high-pressure plasma plume. This causes the metal material to be ablated, stripped, and released into the solvent, where it rapidly condenses to form an initial dispersion of metal nanoparticles. Continuous bombardment for 1-20 minutes yields a dispersion with a metal nanocluster content of approximately 0.1-50 mg / mL, i.e., the metal nanocluster mother liquor. The selection of laser flux is crucial: too low a flux may result in insufficient ablation efficiency and low product concentration; too high a flux may easily generate excessively large particles.

[0027] Phase Two: Fine-tuning and Stabilization of Colloidal Solutions To obtain metal nanoclusters with more uniform size, more stable dispersion, and suitability for subsequent composite processes, the mother liquor obtained in the first stage needs to undergo a second laser irradiation treatment. The mother liquor is then transferred to a temperature-controlled device, and the temperature of the treatment environment is set and maintained within a low temperature range of -20 to 10°C. Under this low-temperature environment, a flux of 0.1–2 Jpulse is used. -1 cm -2 The second nanosecond pulsed laser beam directly irradiates the mother liquor containing the metal nanoclusters for 1-10 minutes. The low-temperature environment effectively suppresses the localized thermal effects generated when the laser acts on the nanoparticles already formed in the liquid, preventing excessive particle growth or maturation. A suitable secondary laser flux can "modify" or "fragment" larger or irregularly shaped particles in the mother liquor, while simultaneously promoting the formation of small clusters and enhancing their colloidal stability in the solvent, ultimately yielding a stable colloidal solution containing well-dispersed metal species primarily in the form of nanoclusters.

[0028] S2. Preparation of in-situ confined composite materials Pre-weighed precursors for the synthesis of covalent organic frameworks, including aldehyde and amine precursors, are directly added to the colloidal solution of metal nanoclusters prepared in step S1. After addition, the mixture is sonicated for 10-20 minutes to ensure that the solid precursors are fully dissolved and uniformly dispersed in the colloidal solution, forming a homogeneous mixed reaction system. In this system, metal nanoclusters, aldehyde monomers, amine monomers, and solvent molecules are mixed together.

[0029] The homogeneous reaction system was transferred to a pressure-resistant sealed container, which was then placed in a constant-temperature oven at 120°C for static reaction. This temperature is sufficient to drive an efficient condensation reaction between the aldehyde and amino groups, while maintaining the liquid state of the solvent to facilitate slow crystal growth. The reaction time is typically set to 72 hours to ensure complete reaction and formation of a well-crystallized COF framework. During the thermotropic polymerization and crystallization process, the two-dimensional or three-dimensional network of COFs, using precursor molecules as nodes, gradually grows, extends, and eventually assembles into crystals with regular nanopores in the solution. The metal nanoclusters, originally uniformly dispersed in the solution, are captured by the gradually growing and extending organic network during the formation of the COF framework and the construction of pores, thus being confined within the newly formed COF pores, achieving "in-situ confinement."

[0030] After the reaction, the mixture was allowed to cool naturally to room temperature. A solid precipitate formed in the container. The precipitate was collected and washed to remove unreacted monomers, catalysts, solvent molecules, and other possible physically adsorbed impurities. The washing process involved alternating washing with multiple solvents, typically in the following order: first, washing with N,N-dimethylformamide (DMF) to dissolve and remove most organic impurities; followed by washing with tetrahydrofuran (THF), acetone, and ethanol in sequence. Each solvent was typically used 2-4 times, and the entire process involved at least three alternating washes to ensure thorough washing. Finally, the washed solid product was placed in a vacuum drying oven and dried at 80°C for 10-14 hours to remove residual solvents, yielding the final product—a metal nanocluster confined covalent organic framework composite material. The resulting material was in powder form, with the metal nanoclusters encapsulated in a highly dispersed state within the bulk channels of the COFs.

[0031] In some embodiments, the solvent used in preparing the colloidal solution of metal nanoclusters not only serves as the medium for laser ablation, but its properties also directly affect the subsequent in-situ synthesis of COFs. The solvent system selected in this application is one of water, n-butanol, ethanol, dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), and dioxane. The solvent meets two basic conditions: first, it can effectively disperse the metal species generated by laser ablation to form a relatively stable colloid; second, its polarity and boiling point must match the solubility of the selected COF precursor and the polymerization reaction conditions (120°C). For example, a mixture of dioxane and mesitylene is often used for the solvothermal synthesis of borate ester or imine bond COFs; DMF and DMSO have good solubility for most organic monomers and are common reaction media. In specific implementations, the solvent can be selected according to the literature conventions for the synthesis of the target COFs and the properties of the metal target.

[0032] In some embodiments, the method of this application has metal universality. The metal target refers to the source material used for laser ablation, and its metal element is selected from at least one of platinum (Pt), palladium (Pd), gold (Au), iron (Fe), cobalt (Co), and nickel (Ni). These metals are all important catalytically active components. Preparing them into nanoclusters and confining them within the channels of COFs aims to improve their performance in multiphase catalytic reactions such as hydrogenation, oxidation, and coupling. Using high-purity corresponding metal foils or bulk materials as the target material ensures the purity of the metal nanoclusters in the colloidal solution and avoids the introduction of anionic impurities. Different metals may have slightly different ablation efficiencies under the same laser parameters due to differences in their physical properties (such as melting point and thermal conductivity), but by fine-tuning the bombardment time (1-20 min), a suitable concentration of mother liquor can be obtained.

[0033] In some embodiments, the stoichiometry of the aldehyde and amine precursors is crucial in determining whether a well-structured COF framework can be formed. In this application, the ratio of the total molar number of aldehyde groups (-CHO) in the aldehyde precursor to the total molar number of amino groups (-NH2) in the amine precursor is 1:1. This stoichiometric ratio originates from the fundamental reaction principle of COF formation—the Schiff base condensation reaction. In this reaction, one aldehyde group reacts with one amino group, losing one molecule of water to form an imine bond (-C=N-). Theoretically, only when the aldehyde and amino groups react in equal molar amounts can all functional groups react completely, maximizing the formation of an extended covalent network, thereby obtaining a COF support with high crystallinity and a complete porous structure. If the ratio is unbalanced, for example, with an excess of aldehyde or amine groups, a large number of unreacted functional groups will remain, which may not only hinder the formation of a long-range ordered crystal structure and reduce the crystallinity of the material, but the residual groups may also interfere with the stable confinement of metal nanoclusters.

[0034] In some embodiments, the aldehyde precursor is selected from one of trialdehyde phloroglucinol, 2-hydroxy-1,3,5-benzyltricarboxaldehyde, and 2,4-dihydroxy-1,3,5-pyromellitic tricarboxaldehyde.

[0035] In some embodiments, the amine precursor is selected from p-phenylenediamine, o-phenylenediamine, m-phenylenediamine, o-toluenediamine, 2,5-diaminobenzonitrile, 2,5-diaminop-benzonitrile, 2-fluoro-1,4-phenylenediamine, 2-chloro-1,4-p-phenylenediamine, 2-bromo-1,4-diaminobenzene, 2-iodo-1,4-phenylenediamine, 2,5-dimethyl-1,4-phenylenediamine, 2-chloro-5-methyl-1,4-phenylenediamine, 2,5-dichlorop-phenylenediamine, 2, 5-Difluoro-p-phenylenediamine, 2,5-dibromo-p-phenylenediamine, 2,5-diaminophenyl-1,4-diphenol, 1,4-diamino-2,5-divinylbenzene, 2,6-diynyl-p-phenylenediamine, 3,4-difluoro-o-phenylenediamine, 2,3-diaminofluorobenzene, 5-bromo-3-fluoro-1,2-phenylenediamine, 1,2-diamino-3,5-difluorobenzene, 4-bromo-3-fluoro-1,2-phenylenediamine, 3,4,5,6-tetrafluorophenyl-1,2-diamine, 3, 4,5-Trifluoro-1,2-diaminobenzene, 4-chloro-6-fluoro-o-phenylenediamine, 5-chloro-3-methyl-1,2-phenylenediamine, 5-bromo-3,4-dimethylphenyl-1,2-diamine, 4-bromo-3-toluene-1,2-diamine, 3,4-dimethyl-o-phenylenediamine, 3,5-dimethyl-1,2-phenylenediamine, 5-bromo-3-methylphenyl-1,2-diamine, 2,3-diaminotoluene, 2,4-diaminofluorobenzene, 4,6-difluorobenzene-1,3 One of the following: 2,4,5-trifluoro-1,3-phenylenediamine, 4-bromo-6-fluorophenyl-1,3-diamine, 2-chloro-4-fluoro-1,3-phenylenediamine, 2-fluoro-4-bromo-1,3-phenylenediamine, 2,4-diaminotoluene, 2,6-diaminotoluene, 2,4,6-trimethyl-1,3-phenylenediamine, 2,4-dimethylphenyl-1,3-diamine, 2,4-dimethyl-1,5-phenylenediamine, and 2-methoxyphenyl-1,4-diamine.

[0036] In some embodiments, to promote the dehydration of the condensation reaction and the formation of crystalline COFs, a small amount of acidic catalyst and a certain amount of high-boiling-point organic solvent can be added to the reaction system as crystallization regulators. Subsequently, the container is subjected to a "freezing-pumping-thawing" cycle to remove dissolved oxygen, and finally sealed under vacuum. The acidic catalyst can be a 6 M aqueous solution of acetic acid, and the high-boiling-point organic solvent can be mesitylene or o-dichlorobenzene.

[0037] The present application will be further described in detail below with reference to specific embodiments.

[0038] In Examples 1-4, the metal nanoclusters were Pt, Pd, Au or Ni, the amine precursor was 2,5-diaminobenzonitrile, the aldehyde precursor was trialdehyde phloroglucinol, and the synthesized COF was COF1.

[0039] Example 1: Preparation of Pt@COF1 1) A wavelength of 1064 nm and a laser flux of 1.2 Jpulse were used. -1 cm -2 Nanosecond pulsed laser light was used to bombard a Pt foil placed in 3 mL of dioxane for 10 min to obtain a dioxane mother liquor containing Pt nanoclusters; then, the ambient temperature was set to 0 °C, and the obtained dioxane mother liquor was subjected to a 1.4 Jpulse laser. -1 cm -2 A dioxane colloidal solution containing Pt nanoclusters was obtained by secondary bombardment with a pulsed laser for 2 min. 2) 12.60 mg of 2,5-diaminobenzonitrile and 11.98 mg of trialdehyde phloroglucinol were directly added to an ampoule containing 2 mL of dioxane colloidal solution of Pt nanoclusters. Then, 2 mL of mesitylene and 0.2 mL of glacial acetic acid (6M) were added. After sonication for 15 min, the mixture was subjected to three cycles of freezing-pumping-thawing and flame sealing. The sealed ampoule was then allowed to stand at 120 °C for 72 h. The resulting precipitate was washed three times alternately with N,N-dimethylformamide, tetrahydrofuran, acetone, and ethanol. The resulting powder was vacuum dried at 80 °C for 12 h to obtain the Pt nanocluster confined COF1 composite material.

[0040] Figure 1 This is a high-resolution transmission electron microscope (HRTEM) image of the Pt nanocluster confined COF1 composite material (Pt@COF1) prepared in Example 1. Figure 1 It is known that the Pt@COF1 composite material synthesized in this application does not contain non-uniform Pt, the Pt species are uniformly distributed, and the size is almost all ≤1nm.

[0041] Example 2: Preparation of Pd@COF1 1) A wavelength of 1064 nm and a laser flux of 1.0 Jpulse were used. -1 cm -2 A nanosecond pulsed laser was used to bombard a Pd foil placed in 3 mL of N,N-dimethylformamide for 10 min to obtain an N,N-dimethylformamide mother liquor containing Pd nanoclusters; then, the ambient temperature was set to -15℃, and the obtained mother liquor was subjected to a 1.4 Jpulse laser. -1 cm -2 A colloidal solution of N,N-dimethylformamide containing Pd nanoclusters was obtained by secondary bombardment with pulsed laser for 2 min. 2) 12.60 mg of 2,5-diaminobenzonitrile and 11.98 mg of trialdehyde phloroglucinol were directly added to an ampoule containing 2 mL of N,N-dimethylformamide colloidal solution with Pd nanoclusters. Then 0.2 mL of glacial acetic acid (6M) was added. After sonication for 15 min, the mixture was subjected to three cycles of freezing-pumping-thawing and flame sealing. The sealed ampoule was then allowed to stand at 120 °C for 72 h. The resulting precipitate was washed three times alternately with tetrahydrofuran, acetone, and ethanol. The resulting powder was then vacuum dried at 80 °C for 12 h to obtain the Pd nanocluster confined COF1 composite material.

[0042] Example 3: Preparation of Au@COF1 1) A wavelength of 1064 nm and a laser flux of 1.2 Jpulse were used. -1 cm -2 Nanosecond pulsed laser light was used to bombard Au foil placed in 3 mL of n-butanol for 10 min to obtain a n-butanol mother liquor containing Au nanoclusters; then, the ambient temperature was set to -20℃, and the obtained mother liquor was subjected to a 1.4 Jpulse laser. -1 cm -2 A n-butanol colloidal solution containing Au nanoclusters was obtained by secondary bombardment with a pulsed laser for 2 min. 2) 12.60 mg of 2,5-diaminobenzonitrile and 11.98 mg of trialdehyde phloroglucinol were directly added to an ampoule containing an Au nanocluster in n-butanol colloidal solution. Then, 2 mL of o-dichlorobenzene and 0.2 mL of glacial acetic acid (6M) were added. After sonication for 15 min, the mixture was subjected to three cycles of freezing-pumping-thawing and flame sealing. The sealed ampoule was then allowed to stand at 120 °C for 72 h. The resulting precipitate was washed three times alternately with N,N-dimethylformamide, tetrahydrofuran, acetone, and ethanol. The resulting powder was then vacuum dried at 80 °C for 12 h to obtain the Au nanocluster confined COF1 composite material.

[0043] Example 4: Preparation of Ni@COF1 1) A wavelength of 1064 nm and a laser flux of 1.0 Jpulse were used. -1 cm -2 A nanosecond pulsed laser was used to bombard a Ni foil placed in 3 mL of n-butanol for 10 min to obtain a n-butanol mother liquor containing Ni nanoclusters; then, the ambient temperature was set to -20℃, and the obtained mother liquor was subjected to a 1.4 Jpulse laser. -1 cm -2 A n-butanol colloidal solution containing Ni nanoclusters was obtained by secondary bombardment with a pulsed laser for 2 min. 2) 12.60 mg of 2,5-diaminobenzonitrile and 11.98 mg of trialdehyde phloroglucinol were directly added to an ampoule containing a butanol colloidal solution of Ni nanoclusters. Then, 2 mL of o-dichlorobenzene and 0.2 mL of glacial acetic acid (6M) were added. After sonication for 15 min, the mixture was subjected to three cycles of freezing-pumping-thawing and flame sealing. The sealed ampoule was then allowed to stand at 120 °C for 72 h. The resulting precipitate was washed three times alternately with N,N-dimethylformamide, tetrahydrofuran, acetone, and ethanol. The resulting powder was vacuum dried at 80 °C for 12 h to obtain the Ni nanocluster confined COF1 composite material.

[0044] In Examples 5-6, the metal nanoclusters were Co or Ni, the amine precursor was p-phenylenediamine, the aldehyde precursor was trialdehyde phloroglucinol, and the synthesized COF was COF2.

[0045] Example 5: Preparation of Co@COF2 1) A wavelength of 1064nm and a laser flux of 1.0Jpulse were used. -1 cm -2 Nanosecond pulsed laser light was used to bombard Co foil placed in 3 mL of n-butanol for 2 min to obtain a n-butanol mother liquor containing Co nanoclusters; then the ambient temperature was set to -20℃, and the obtained mother liquor was subjected to a 1.4 J pulsed laser. -1 cm -2 A n-butanol colloidal solution containing Co nanoclusters was obtained by secondary bombardment with a pulsed laser for 2 minutes. 2) 9.73 mg of p-phenylenediamine and 12.60 mg of trialdehyde phloroglucinol were directly added to an ampoule containing a butanol colloidal solution of Co nanoclusters. Then, 2 mL of o-dichlorobenzene and 0.2 mL of glacial acetic acid (6 M) were added. After sonication for 15 min, the mixture was subjected to three cycles of freezing-pumping-thawing and flame sealing. The sealed ampoule was then allowed to stand at 120 °C for 72 h. The resulting precipitate was washed three times alternately with N,N-dimethylformamide, tetrahydrofuran, acetone, and ethanol. The resulting powder was then vacuum dried at 80 °C for 12 h to obtain the Co nanocluster confined COF2 composite material.

[0046] Example 6: Preparation of Ni@COF2 1) A wavelength of 1064nm and a laser flux of 1.0Jpulse were used. -1 cm -2 A nanosecond pulsed laser was used to bombard a Ni foil placed in 3 mL of dimethyl sulfoxide for 2 min to obtain a dimethyl sulfoxide mother liquor containing Ni nanoclusters; then, the ambient temperature was set to -10℃, and the obtained mother liquor was subjected to a 1.4 J pulsed laser. -1 cm -2A dimethyl sulfoxide colloidal solution containing Ni nanoclusters was obtained by secondary bombardment with a pulsed laser for 2 minutes. 2) 9.73 mg p-phenylenediamine and 12.60 mg trialdehyde phloroglucinol were ultrasonically dispersed in 2 mL of dimethyl sulfoxide colloidal solution containing Ni nanoclusters in an ampoule. After ultrasonication for 15 min, the mixture was subjected to three cycles of freezing-pumping-thawing and flame sealing. The sealed ampoule was then allowed to stand at 120 °C for 72 h. The resulting precipitate was washed three times alternately with N,N-dimethylformamide, tetrahydrofuran, acetone, and ethanol. The resulting powder was vacuum dried at 80 °C for 12 h to obtain the Ni nanocluster confined COF2 composite material.

[0047] In Examples 7-8, the metal nanoclusters were Au or Fe, the selected amine precursor was dichloro-p-phenylenediamine, the aldehyde precursor was trialdehyde-resorcinol, and the synthesized COF was COF3.

[0048] Example 7 Preparation of Au@COF3 1) A wavelength of 1064nm and a laser flux of 1.0Jpulse were used. -1 cm -2 A nanosecond pulsed laser was used to bombard Au foil placed in 3 mL of dimethyl sulfoxide for 2 min to obtain a dimethyl sulfoxide mother liquor containing Au nanoclusters; then the ambient temperature was set to -10℃, and the obtained mother liquor was subjected to a 1.4 J pulsed laser. -1 cm -2 A dimethyl sulfoxide colloidal solution containing Au nanoclusters was obtained by secondary bombardment with a pulsed laser for 10 min. 2) 15.93 mg of dichloro-p-phenylenediamine and 12.60 mg of m-phenyltriformaldehyde were ultrasonically dispersed in 2 mL of dimethyl sulfoxide colloidal solution containing Au nanoclusters in an ampoule. After ultrasonication for 15 min, the mixture was subjected to three cycles of freezing-pumping-thawing and flame sealing. The sealed ampoule was then allowed to stand at 120 °C for 72 h. The resulting precipitate was washed three times alternately with N,N-dimethylformamide, tetrahydrofuran, acetone, and ethanol. The resulting powder was vacuum dried at 80 °C for 12 h to obtain Au nanocluster confined COF3 composite material.

[0049] Example 8: Preparation of Fe@COF3 1) A wavelength of 1064nm and a laser flux of 1.6Jpulse were used. -1 cm -2 A nanosecond pulsed laser was used to bombard Ru foil placed in 3 mL of dimethyl sulfoxide for 2 min to obtain a dimethyl sulfoxide mother liquor containing Fe nanoclusters; then the ambient temperature was set to -10℃, and the obtained mother liquor was subjected to a 1.4 J pulsed laser. -1 cm -2A dimethyl sulfoxide colloidal solution containing Fe nanoclusters was obtained by secondary bombardment with a pulsed laser for 10 min. 2) 15.93 mg dichloro-p-phenylenediamine and 12.60 mg m-phenyltriformaldehyde were ultrasonically dispersed in 2 mL of dimethyl sulfoxide colloidal solution containing Fe nanoclusters in an ampoule. After ultrasonication for 15 min, the mixture was subjected to three cycles of freezing-pumping-thawing and flame sealing. The sealed ampoule was then allowed to stand at 120 °C for 72 h. The resulting precipitate was then washed three times alternately with N,N-dimethylformamide, tetrahydrofuran, acetone, and ethanol. The resulting powder was vacuum dried at 80 °C for 12 h to obtain the Fe nanocluster confined COF3 composite material.

[0050] In Examples 9-12, the metal nanoclusters were Pt, Pd, Au or Ni, the amine precursor was m-phenylenediamine, the aldehyde precursor was trialdehyde phloroglucinol, and the synthesized COF was COF4.

[0051] Example 9: Preparation of Pt@COF4 1) A wavelength of 1064nm and a laser flux of 1.0Jpulse were used. -1 cm -2 A nanosecond pulsed laser was used to bombard a Pt foil placed in 3 mL of dimethyl sulfoxide for 2 min to obtain a dimethyl sulfoxide mother liquor containing Pt nanoclusters; then, the ambient temperature was set to -10℃, and the obtained mother liquor was subjected to a 1.4 J pulsed laser. -1 cm -2 A dimethyl sulfoxide colloidal solution containing Pt nanoclusters was obtained by secondary bombardment with a pulsed laser for 10 min. 2) 9.73 mg m-phenylenediamine and 12.60 mg trialdehyde phloroglucinol were ultrasonically dispersed in 2 mL of dimethyl sulfoxide colloidal solution containing Ag nanoclusters in an ampoule. After ultrasonication for 15 min, the mixture was subjected to three cycles of freezing-pumping-thawing and flame sealing. The sealed ampoule was then allowed to stand at 120 °C for 72 h. The resulting precipitate was then washed three times alternately with N,N-dimethylformamide, tetrahydrofuran, acetone, and ethanol. The resulting powder was vacuum dried at 80 °C for 12 h to obtain the Pt nanocluster confined COF4 composite material.

[0052] Example 10: Preparation of Pd@COF4 1) A wavelength of 1064nm and a laser flux of 1.0Jpulse were used. -1 cm -2 A nanosecond pulsed laser was used to bombard a Pd foil placed in 3 mL of dimethyl sulfoxide for 2 min to obtain a dimethyl sulfoxide mother liquor containing Er nanoclusters; then the ambient temperature was set to -10℃, and the obtained mother liquor was subjected to a 1.4 J pulsed laser. -1 cm -2A dimethyl sulfoxide colloidal solution containing Pd nanoclusters was obtained by secondary bombardment with a pulsed laser for 10 min. 2) 9.73 mg m-phenylenediamine and 12.60 mg trialdehyde phloroglucinol were ultrasonically dispersed in 2 mL of dimethyl sulfoxide colloidal solution containing Pd nanoclusters in an ampoule. After ultrasonication for 15 min, the mixture was subjected to three cycles of freezing-pumping-thawing and flame sealing. The sealed ampoule was then allowed to stand at 120 °C for 72 h. The resulting precipitate was then washed three times alternately with N,N-dimethylformamide, tetrahydrofuran, acetone, and ethanol. The resulting powder was vacuum dried at 80 °C for 12 h to obtain the Pd nanocluster confined COF4 composite material.

[0053] Example 11 Preparation of Au@COF4 1) A wavelength of 1064nm and a laser flux of 1.0Jpulse were used. -1 cm -2 A nanosecond pulsed laser was used to bombard Au foil placed in 3 mL of dimethyl sulfoxide for 2 min to obtain a dimethyl sulfoxide mother liquor containing Au nanoclusters; then the ambient temperature was set to -10℃, and the obtained mother liquor was subjected to a 1.4 J pulsed laser. -1 cm -2 A dimethyl sulfoxide colloidal solution containing Au nanoclusters was obtained by secondary bombardment with a pulsed laser for 10 min. 2) 9.73 mg m-phenylenediamine and 12.60 mg trialdehyde phloroglucinol were ultrasonically dispersed in 2 mL of dimethyl sulfoxide colloidal solution containing Au nanoclusters in an ampoule. After ultrasonication for 15 min, the mixture was subjected to three cycles of freezing-pumping-thawing and flame sealing. The sealed ampoule was then allowed to stand at 120 °C for 72 h. The resulting precipitate was then washed three times alternately with N,N-dimethylformamide, tetrahydrofuran, acetone, and ethanol. The resulting powder was vacuum dried at 80 °C for 12 h to obtain Au nanocluster confined COF4 composite material.

[0054] Example 12 Preparation of Ni@COF4 1) A wavelength of 1064nm and a laser flux of 1.0Jpulse were used. -1 cm -2 A nanosecond pulsed laser was used to bombard a Ni foil placed in 3 mL of dimethyl sulfoxide for 2 min to obtain a dimethyl sulfoxide mother liquor containing Ni nanoclusters; then, the ambient temperature was set to -10℃, and the obtained mother liquor was subjected to a 1.4 J pulsed laser. -1 cm -2 A dimethyl sulfoxide colloidal solution containing Ni nanoclusters was obtained by secondary bombardment with a pulsed laser for 10 min. 2) 9.73 mg m-phenylenediamine and 12.60 mg trialdehyde phloroglucinol were ultrasonically dispersed in 2 mL of dimethyl sulfoxide colloidal solution containing Ni nanoclusters in an ampoule. After ultrasonication for 15 min, the mixture was subjected to three cycles of freezing-pumping-thawing and flame sealing. The sealed ampoule was then allowed to stand at 120 °C for 72 h. The resulting precipitate was then washed three times alternately with N,N-dimethylformamide, tetrahydrofuran, acetone, and ethanol. The resulting powder was vacuum dried at 80 °C for 12 h to obtain the Ni nanocluster confined COF4 composite material.

[0055] Preparation of pure COF1 (Comparative Example 1) 12.60 mg of 2,5-diaminobenzonitrile and 11.98 mg of trialdehyde phloroglucinol were added to an ampoule containing 2 mL of dioxane and 2 mL of mesitylene solution. Then, 0.2 mL of 6 M glacial acetic acid was added. After sonication for 15 min, the mixture was subjected to three cycles of freezing-pumping-thawing, followed by flame sealing. The sealed ampoule was then allowed to stand at 120 °C for 72 h. The resulting precipitate was washed three times alternately with N,N-dimethylformamide, tetrahydrofuran, acetone, and ethanol, and then dried under vacuum at 80 °C for 12 h to obtain COF1 material.

[0056] Figure 2 (a) The X-ray near-edge absorption structure (XANES) spectrum shows that the white line intensity of the Pt@COF1 sample is between Pt0 and Pt2+, indicating that the Pt species in Pt@COF1 is an intermediate oxidation state between Pt0 and Pt2+. Meanwhile, the observed low-intensity Pt-O coordination bonds ( Figure 2 (b) also demonstrates the existence of this oxidation state. Figure 2 (b) The extended X-ray absorption fine structure (EXAFS) Fourier transform spectra of Pt@COF1 and the reference are shown. The main peak at 1.85 Å in the Pt@COF1 spectrum corresponds to the Pt-O / N coordination bond between the Pt nanoclusters and the COF framework, accompanied by trace amounts of metallic Pt-Pt bonds (2.2 Å).

[0057] Figure 3 The X-ray powder diffraction (XRD) spectra of Pt@COF1 prepared in Example 1 and COF1 prepared in Comparative Example 1 are shown. The comparison shows that the preparation method of in-situ implantation of metal nanoclusters into COF material provided in this application has no effect on the crystallinity of COF, and the obtained nanocluster confined COF composite material has excellent crystallinity and ordered structure.

[0058] Comparative Example 2: Preparation of Pure COF2 11.35 mg of p-phenylenediamine and 11.34 mg of m-phenyltriformaldehyde were added to an ampoule containing 2 mL of dimethyl sulfoxide solution, followed by 0.2 mL of 6 M glacial acetic acid. After sonication for 15 min, the mixture was subjected to three cycles of freezing-pumping-thawing, followed by flame sealing. The sealed ampoule was then allowed to stand at 120 °C for 72 h. The resulting precipitate was washed three times alternately with N,N-dimethylformamide, tetrahydrofuran, acetone, and ethanol, and then vacuum dried at 80 °C for 12 h to obtain COF2 material.

[0059] Preparation of pure COF3 (Comparative Example 3) 15.93 mg of dichloro-p-phenylenediamine and 9.73 mg of m-phenyltriformaldehyde were added to an ampoule containing 2 mL of dimethyl sulfoxide solution, followed by 0.2 mL of 6 M glacial acetic acid. After sonication for 15 min, the mixture was subjected to three cycles of freezing-pumping-thawing, followed by flame sealing. The sealed ampoule was then allowed to stand at 120 °C for 72 h. The resulting precipitate was washed three times alternately with N,N-dimethylformamide, tetrahydrofuran, acetone, and ethanol, and then vacuum dried at 80 °C for 12 h to obtain COF3 material.

[0060] Preparation of pure COF4 (Comparative Example 4) 16.58 mg of benzidine and 9.73 mg of m-phenyltriformaldehyde were added to an ampoule containing 2 mL of dimethyl sulfoxide solution, followed by 0.2 mL of 6 M glacial acetic acid. After sonication for 15 min, the mixture was subjected to three cycles of freezing-pumping-thawing, followed by flame sealing. The sealed ampoule was then allowed to stand at 120 °C for 72 h. The resulting precipitate was washed three times alternately with N,N-dimethylformamide, tetrahydrofuran, acetone, and ethanol, and then dried under vacuum at 80 °C for 12 h to obtain COF4 material.

[0061] Therefore, the metal nanoclusters confined COFs material prepared in this application exhibits high purity, is free of impurity ions, and has good crystallinity. The nanoclusters are highly uniformly distributed within the COFs channels, potentially offering the advantage of balancing catalytic activity and stability in heterogeneous catalysis. Furthermore, the preparation method provided in this application is simple, universal, and easy to implement, demonstrating promising potential applications in the field of heterogeneous catalysis.

[0062] Although the embodiments of this application have been described above in conjunction with the accompanying drawings, this application is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, not restrictive. Those skilled in the art can make many other forms based on the guidance of this specification and without departing from the scope of protection of the claims of this application, and these are all within the scope of protection of this application.

Claims

1. A method for preparing a metal nanocluster confined covalent organic framework composite material, characterized in that, Includes the following steps: S1. A metal target placed in a solvent is bombarded with a first nanosecond pulsed laser to obtain a metal nanocluster mother liquor; subsequently, the metal nanocluster mother liquor is irradiated a second time with a second nanosecond pulsed laser at an ambient temperature of -20 to 10°C to obtain a metal nanocluster colloidal solution; wherein, the wavelength of the first nanosecond pulsed laser is 1064 nm and the flux is 1~2 Jpulse. -1 cm -2 The flux of the second nanosecond pulsed laser is 0.1~2 Jpulse. -1 cm -2 ; S2. The aldehyde precursor and amine precursor of the covalent organic framework are added to the colloidal solution of the metal nanoclusters to form a reaction system. The system is subjected to static polymerization at 120°C. After the reaction is completed, the resulting solid product is washed and dried to obtain the metal nanocluster confined covalent organic framework composite material.

2. The preparation method according to claim 1, characterized in that, The time for the first nanosecond pulse laser to bombard the metal target is 1~20 min; the time for the second irradiation is 1~10 min.

3. The preparation method according to claim 1, characterized in that, The solvent is selected from one of water, n-butanol, ethanol, dimethyl sulfoxide, N,N-dimethylformamide, and dioxane.

4. The preparation method according to claim 1, characterized in that, The metal target material is selected from at least one of Pt, Pd, Au, Fe, Co and Ni.

5. The preparation method according to claim 1, characterized in that, The amounts of the aldehyde precursor and the amine precursor are such that the ratio of the total molar number of aldehyde groups to the total molar number of amino groups is 1:

1.

6. The preparation method according to claim 1, characterized in that, The aldehyde precursor is selected from one of trialdehyde phloroglucinol, 2-hydroxy-1,3,5-benzyltricarboxaldehyde, and 2,4-dihydroxy-1,3,5-pyromellitic tricarboxaldehyde.

7. The preparation method according to claim 1, characterized in that, The amine precursor is selected from p-phenylenediamine, o-phenylenediamine, m-phenylenediamine, o-toluenediamine, 2,5-diaminobenzonitrile, 2,5-diaminop-benzonitrile, 2-fluoro-1,4-phenylenediamine, 2-chloro-1,4-p-phenylenediamine, 2-bromo-1,4-diaminobenzene, 2-iodo-1,4-phenylenediamine, 2,5-dimethyl-1,4-phenylenediamine, 2-chloro-5-methyl-1,4-phenylenediamine, 2,5-dichlorop-phenylenediamine, and 2,5-difluorop-phenylenediamine. Diamine, 2,5-dibromo-p-phenylenediamine, 2,5-diaminophenyl-1,4-diphenol, 1,4-diamino-2,5-divinylbenzene, 2,6-diynyl-p-phenylenediamine, 3,4-difluoro-o-phenylenediamine, 2,3-diaminofluorobenzene, 5-bromo-3-fluoro-1,2-phenylenediamine, 1,2-diamino-3,5-difluorobenzene, 4-bromo-3-fluoro-1,2-phenylenediamine, 3,4,5,6-tetrafluorobenzene-1,2-diamine, 3,4,5- Trifluoro-1,2-diaminobenzene, 4-chloro-6-fluoro-o-phenylenediamine, 5-chloro-3-methyl-1,2-phenylenediamine, 5-bromo-3,4-dimethylphenyl-1,2-diamine, 4-bromo-3-toluene-1,2-diamine, 3,4-dimethyl-o-phenylenediamine, 3,5-dimethyl-1,2-phenylenediamine, 5-bromo-3-methylphenyl-1,2-diamine, 2,3-diaminotoluene, 2,4-diaminofluorobenzene, 4,6-difluorobenzene-1,3-di One of the following: amine, 2,4,5-trifluoro-1,3-phenylenediamine, 4-bromo-6-fluorophenyl-1,3-diamine, 2-chloro-4-fluoro-1,3-phenylenediamine, 2-fluoro-4-bromo-1,3-phenylenediamine, 2,4-diaminotoluene, 2,6-diaminotoluene, 2,4,6-trimethyl-1,3-phenylenediamine, 2,4-dimethylphenyl-1,3-diamine, 2,4-dimethyl-1,5-phenylenediamine, and 2-methoxyphenyl-1,4-diamine.

8. The preparation method according to claim 1, characterized in that, The metal nanoclusters in the mother liquor contain 0.1-50 mg / mL of metal nanoclusters.

9. The preparation method according to claim 1, characterized in that, An acidic catalyst and a boiling point organic solvent are added to the reaction system as crystallization regulators. The acidic catalyst is a 6 M aqueous solution of acetic acid, and the high-boiling point organic solvent is mesitylene or o-dichlorobenzene.

10. The metal nanocluster confined covalent organic framework composite material prepared by the preparation method according to any one of claims 1-9.

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