A method for preparing and applying a composite material encapsulating guest molecules within a covalent organic framework.

Abstract

This invention belongs to the field of new materials technology, specifically relating to a method for preparing and applying a composite material encapsulating guest molecules within a covalent organic framework. The general chemical formula is PANa@COFs@Guest, where PANa is sodium polyacrylate, COFs are covalent organic frameworks, and Guest is a guest molecule (phosphoric acid, sulfuric acid, imidazole, etc.). The guest molecule is loaded into the pores of the COFs by grinding, and the sodium polyacrylate is coated onto the surface of the COFs through an in-situ reaction of acrylic acid monomers. This composite material encapsulating guest molecules within a covalent organic framework can be used in the field of proton conduction. The encapsulation of PANa effectively prevents the guest molecules from detaching from the pores of the COFs, making it a highly promising functional composite material.

Description

Technical Field

[0001] This invention belongs to the field of new materials technology, specifically relating to a method for preparing and applying a composite material that encapsulates guest molecules within a covalent organic framework. Background Technology

[0002] Covalent organic frameworks (COFs) are a class of crystalline porous materials with a periodic network structure, composed of organic structural units containing lightweight elements such as boron, carbon, nitrogen, and oxygen linked by reversible covalent bonds. This unique chemical and topological structure endows them with outstanding advantages such as high specific surface area, excellent thermal / chemical stability, and a highly modifiable framework. Thanks to these properties, and the ability to be precisely designed and synthesized at the molecular level, COFs have shown great potential in many cutting-edge fields such as proton conduction, gas adsorption / separation, heterogeneous catalysis, and optoelectronic functional materials, and are widely regarded as a highly promising functional porous material platform.

[0003] The structural units of COFs are interconnected by covalent bonds, which endows the COF framework with better thermal stability. However, when we fill the regular channels of COFs with guest molecules (such as proton donors crucial for proton conduction, such as phosphate and imidazole) to construct high-performance composite materials, a common and critical technical challenge emerges: under practical application conditions, especially during long-term operation or in liquid environments, guest molecules within the channels are highly prone to leakage or detachment. This phenomenon not only directly weakens the expected function of the composite material but also leads to rapid performance degradation, fundamentally restricting the long-term stable application of COF-based composite materials in fields such as high-performance proton exchange membranes and sensors. In recent years, many papers have reported synthetic methods and applications based on COFs to solve related problems. For example, Heping Ma, Bailing Liu, Bin Li, Liming Zhang, Yang-Guang Li, Hua-Qiao Tan, Hong-Ying Zang, Guangshan Zhu, J.Am. Chem. Soc. 2016, 138(18), pp 5897-5903 proposed a size matching strategy based on cationic COF (EB-COF: Br): by designing special pore sizes to precisely lock specific guest molecules (such as certain polymetallic oxide clusters), thereby ensuring high proton conduction while suppressing their leakage.

[0004] The aforementioned method relies heavily on a precise match between the inherent pore structure of the COFs and the size of the target guest molecules. No universally applicable and effective strategy for addressing guest molecule leakage has been reported. In other words, a general method for encapsulating guest molecules within a covalent organic framework is lacking. Summary of the Invention

[0005] In order to solve the technical problems in the background art, the present invention provides a composite material capable of encapsulating guest molecules within a covalent organic framework.

[0006] The technical solution of this invention to solve the above-mentioned technical problems is as follows: a composite material for encapsulating guest molecules within a covalent organic framework, with the general chemical formula PANa@COFs@Guest, wherein PANa is sodium polyacrylate, COFs is a covalent organic framework, and Guest is a guest molecule (phosphoric acid, sulfuric acid, imidazole, etc.).

[0007] The guest molecules are loaded into the pores of COFs by grinding, and the sodium polyacrylate is coated onto the surface of COFs by in-situ reaction of the monomer acrylic acid.

[0008] The beneficial effects of this invention are: the composite material of this invention that encapsulates guest molecules within a covalent organic framework can effectively prevent guest molecules encapsulated within the pores of COFs from falling off.

[0009] This invention also provides a method for preparing a composite material encapsulating guest molecules within a covalent organic framework, comprising the following steps:

[0010] A. Add 50 μL of 85% phosphoric acid to 50 mg of COF, grind for half an hour, and then vacuum dry at 120 °C to obtain phosphoric acid-loaded COFs (COFs@H3PO4). Next, mix 5 mg of ground ammonium persulfate with COFs@H3PO4 thoroughly.

[0011] B. Mix acrylic acid (3.6 mL) with deionized water (5 mL) to form solution 1; dissolve 2 g NaOH in 5 mL of deionized water to form solution 2. Add solution 2 dropwise to solution 1 in an ice-water bath while stirring, then add 2 mg of N,N'-methylenebisacrylamide.

[0012] C. Add the mixed solution (50 μL) from step B dropwise to the COFs@H3PO4 from step A, and mix thoroughly with a glass rod. Then, place the mixture in an oven at 65 °C for 2 hours to allow PANa to grow in situ on COFs@H3PO4. After the reaction is complete, wash the solid three times with deionized water to remove excess initiator, crosslinking agent, and NaOH, and then dry it in a vacuum drying oven at 65 °C for 2 hours to obtain the composite material PANa@COFs@H3PO4.

[0013] The beneficial effects of this invention are: the preparation method is simple, the reaction can proceed rapidly, and it saves energy and time. Furthermore, the method for preparing composite materials encapsulating guest molecules within a covalent organic framework according to this invention has high yield and saves costs.

[0014] This invention also provides an application of a composite material encapsulating guest molecules within a covalent organic framework in the field of proton conduction. The composite material encapsulating guest molecules within a covalent organic framework is used as a proton conducting material, and its proton transport performance is detected by an AC impedance meter.

[0015] The beneficial effect of this invention is that the composite material encapsulating guest molecules within a covalent organic framework can be applied to proton conduction. This makes the composite material encapsulating guest molecules within a covalent organic framework more functionally comprehensive. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the synthesis steps of the composite material PANa@COFs@Guest, which encapsulates guest molecules within a covalent organic framework, according to the present invention.

[0017] Figure 2 PXRD pattern of PANa@TpBz@H3PO4 composite material for encapsulating guest molecules within a covalent organic framework in this invention. The horizontal axis is angle and the vertical axis is intensity.

[0018] Figure 3 The infrared spectrum of PANa@TpBz@H3PO4, the composite material of encapsulating guest molecules within a covalent organic framework in this invention, is shown. The horizontal axis represents wavenumber and the vertical axis represents transmittance.

[0019] Figure 4 The comparison of phosphorus content in PANa@TpBz@H3PO4, the composite material for encapsulating guest molecules within a covalent organic framework according to the present invention, is shown on the horizontal axis as material name and the vertical axis as phosphorus content.

[0020] Figure 5 The dynamic leakage ratio of H3PO4 in PANa@TpBz@H3PO4, the composite material of PANa@TpBz@H3PO4 used in this invention to encapsulate guest molecules within a covalent organic framework, is shown on the x-axis as time and the y-axis as leakage rate.

[0021] Figure 6 The dynamic leakage ratio of H2SO4 in PANa@TpBz@H2SO4, the composite material of encapsulating guest molecules within a covalent organic framework of the present invention, is shown on the x-axis as time and the y-axis as leakage rate.

[0022] Figure 7 The dynamic leakage ratio of imidazole in PANa@TpBz@Imidazole, the composite material of encapsulating guest molecules within a covalent organic framework in this invention, is shown on the x-axis as time and the y-axis as leakage rate.

[0023] Figure 8 The humidity-dependent proton conductivity of the composite material PANa@TpBz@H3PO4, which encapsulates guest molecules within a covalent organic framework according to this invention, at 80 °C is shown on the x-axis as Z' and the y-axis as -Z''. Detailed Implementation

[0024] The principles and features of the present invention will be described in detail below with reference to implementation. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0025] Example 1

[0026] A method for preparing a composite material encapsulating guest molecules within a covalent organic framework, specifically comprising the following steps:

[0027] A. Add 50 μL of 85% phosphoric acid to TpBz (50 mg), grind for half an hour, and then vacuum dry at 120 °C to obtain phosphoric acid-loaded TpBz@H3PO4. Next, mix 5 mg of ground ammonium persulfate with TpBz@H3PO4 thoroughly.

[0028] B. Mix acrylic acid (3.6 mL) with deionized water (5 mL) to form solution 1; dissolve 2 g NaOH in 5 mL of deionized water to form solution 2. Add solution 2 dropwise to solution 1 in an ice-water bath while stirring, then add 2 mg of N,N'-methylenebisacrylamide.

[0029] C. Add the mixed solution (50 μL) from step B dropwise to the TpBz@H3PO4 from step A, and mix thoroughly with a glass rod. Then, place the mixture in an oven at 65 °C for 2 hours to allow PANa to grow in situ on TpBz@H3PO4. After the reaction is complete, wash the solid three times with deionized water to remove excess initiator, crosslinking agent, and NaOH, and then dry it in a vacuum drying oven at 65 °C for 2 hours to obtain the composite material PANa@TpBz@H3PO4.

[0030] like Figure 1As shown, H3PO4 was introduced as a proton donor into the pores of TpBz through mechanical grinding, completing the initial loading of guest molecules. Subsequently, an acrylic monomer solution was uniformly coated onto the H3PO4-loaded TpBz surface, and the reaction was carried out at a constant temperature of 65 °C for 2 hours to initiate in-situ polymerization of acrylic acid to generate PANa. After the reaction, the product was thoroughly washed with a large amount of deionized water to completely remove any unreacted H3PO4 and free monomers remaining on the surface, finally obtaining the PANa@TpBz@H3PO4 composite material.

[0031] like Figure 2 As shown, the PANa@TpBz@H3PO4 composite material encapsulating guest molecules within a covalent organic framework was analyzed by X-ray powder diffraction (PXRD). PXRD measurements were performed using Cu-K α (λ = 0.15406 nm) radiation on a Rigaku Ultima IV X-ray diffractometer. Figure 2 We can see that compared with the original TpBz, the intensity of the characteristic diffraction peaks of PANa@TpBz@H3PO4 has decreased, and the crystallinity has decreased to a certain extent. This phenomenon is mainly attributed to the filling effect of H3PO4 molecules in the pores and the interference of the surface PANa polymer coating on the original lattice regularity of TpBz. This shows that the guest molecules and polymers of the present invention have been successfully loaded into TpBz materials.

[0032] like Figure 3 As shown, the PANa@TpBz@H3PO4 composite material encapsulating guest molecules within a covalent organic framework was detected using Fourier transform infrared spectroscopy (FT-IR). The infrared measurement was performed using the KBr pellet method, and samples were collected from 4000 to 4000 cm⁻¹ on a Nicolet 330 FTIR spectrometer. -1 Infrared spectrum within the region. From Figure 3 As can be seen from the image, the FT-IR spectrum of the composite material PANa@TpBz@H3PO4 shows a peak at 988 cm⁻¹. -1 A distinct P=O characteristic stretching vibration peak was observed. The appearance of this characteristic peak directly confirms that the H3PO4 molecule has been successfully encapsulated inside the TpBz channel in this invention.

[0033] like Figure 4 As shown, the elemental composition of the PANa@TpBz@H3PO4 composite material encapsulating guest molecules within a covalent organic framework was quantitatively evaluated using inductively coupled plasma mass spectrometry (ICP-MS) and elemental analysis (EA). When the composite material PANa@TpBz@H3PO4 reached its maximum phosphate loading, the calculated theoretical phosphorus content was 10.49%. From... Figure 4As can be seen from the results, the actual phosphorus content measured by the experiment was 9.91%, and the corresponding calculated phosphoric acid retention rate was 92%, indicating that the present invention can effectively encapsulate H3PO4 guest molecules.

[0034] like Figure 5 As shown, the stability of the PANa@TpBz@H3PO4 composite material encapsulating guest molecules within a covalent organic framework was evaluated using a long-term immersion experiment. First, PANa@TpBz@H3PO4 composite material samples were immersed in 10 mL of deionized water and allowed to stand at a constant temperature for 3 days. The resulting suspension was then centrifuged, and the phosphorus (P) content in the supernatant was precisely analyzed using ICP-MS to calculate the H3PO4 leakage rate. Subsequently, the centrifuged composite material samples were re-immersed in 10 mL of fresh deionized water, and the above immersion-centrifugation-detection process was repeated for a total experimental time of 60 days. Figure 5 As can be seen, the PANa@TpBz@H3PO4 composite material exhibited an H3PO4 leakage rate of approximately 8% during the initial 30 days of the experiment. In the subsequent 30-day immersion experiment, the H3PO4 leakage rate of the composite material was less than 1% and tended to stabilize. This fully demonstrates that the PANa encapsulation strategy in this invention can effectively improve the stability of H3PO4 within the COFs channels.

[0035] like Figure 6 and Figure 7 As shown, the method for preparing guest molecules within the encapsulated covalent organic framework was used to encapsulate H2SO4 and imidazole guest molecules to evaluate the universality of this encapsulation strategy. Figure 6 and Figure 7 As can be seen, after a 30-day impregnation period, the retention rates of guest molecules (H2SO4 and imidazole) in PANa@TpBz@H2SO4 and PANa@TpBz@Imidazole were 84.91% and 84.02%, respectively. After an additional 30-day impregnation, the leakage rates of H2SO4 and imidazole were comparable to those of H3PO4, both remaining below 1%. These findings demonstrate the universality of the encapsulation strategy in this invention for guest molecules.

[0036] like Figure 8 As shown, the proton conduction performance of the PANa@TpBz@H3PO4 composite material encapsulating guest molecules within a covalent organic framework was tested using an AC impedance spectroscopy meter. From... Figure 8 As can be seen from the data, at 80 °C and 50% RH, the proton conductivity of PANa@TpBz@H3PO4 reaches 2.41 × 10⁻⁶. -2 S cm -1 When the temperature is increased to 80 °C and 95% RH, the proton conductivity increases to 5.69 × 10⁻⁶. -1 S cm-1 .

[0037] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A composite material for encapsulating guest molecules within a covalent organic framework, characterized in that: The general chemical formula is PANa@COFs@Guest, where PANa is sodium polyacrylate, COFs is a covalent organic framework, and Guest is a guest molecule (phosphoric acid, sulfuric acid, imidazole, etc.). The guest molecules are loaded into the pores of COFs by grinding, and the sodium polyacrylate is coated onto the surface of COFs by in-situ reaction of the monomer acrylic acid.

2. A method for preparing a composite material encapsulating guest molecules within a covalent organic framework as described in claim 1, characterized in that, Includes the following steps: A. Add 85% phosphoric acid (50 μL) to COF (50 mg), grind for half an hour, and then vacuum dry at 120 °C to obtain phosphoric acid-loaded COFs (COFs@H3PO4); then, mix 5 mg of ground ammonium persulfate with COFs@H3PO4 thoroughly. B. Mix acrylic acid (3.6 mL) with deionized water (5 mL) to form solution 1; dissolve 2 g NaOH in 5 mL of deionized water to form solution 2; add solution 2 dropwise to solution 1 in an ice-water bath while stirring, and then add 2 mg of N,N'-methylenebisacrylamide; C. Add the mixed solution (50 μL) from step B dropwise to the COFs@H3PO4 from step A and mix thoroughly with a glass rod. Then, place the mixture in an oven at 65 °C for 2 hours to allow PANa to grow in situ on COFs@H3PO4. After the reaction is complete, wash the solid three times with deionized water to remove excess initiator, crosslinking agent and NaOH, and then dry it in a vacuum drying oven at 65 °C for 2 hours to obtain the composite material PANa@COFs@H3PO4.

3. The method for preparing the composite material encapsulating guest molecules within a covalent organic framework according to claim 2, characterized in that, The guest molecules include small-volume molecules such as phosphoric acid, sulfuric acid, and imidazole.

4. The method for preparing the composite material encapsulating guest molecules within a covalent organic framework according to any one of claims 2 or 3, characterized in that, The sodium polyacrylate can coat the surface of COFs, effectively preventing guest molecules from falling out of the pores of COFs.

5. The application of a composite material encapsulating guest molecules within a covalent organic framework as described in claim 1 in the field of proton conduction, characterized in that, The composite material encapsulating guest molecules within a covalent organic framework is used as a proton-conducting material, and its proton transport performance is detected by an AC impedance meter.

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