Preparation method and application of F-g-C3N4@COF367 photoelectric composite material

Abstract

The application relates to the technical field of photoelectric functional materials and sensors, and discloses a preparation method and application of a F-g-C3N4@COF367 photoelectric composite material, which comprises the following steps: S1. preparing F-g-C3N4; S2. dissolving 5,10,15,20-tetra(4-aminophenyl)-21H,23H-porphyrin, 2,4,6-trimethylbenzaldehyde and 4,4'-biphenyldimethylaldehyde in a mixed solvent of mesitylene, acetic acid and ethanol to obtain a COF367 precursor solution; and S3. adding F-g-C3N4 into the COF367 precursor solution, and heating to react, so as to obtain the F-g-C3N4@COF367 photoelectric composite material. The photoelectric material of the F-g-C3N4 and the COF367 is constructed, the light absorption capacity of the composite material is enhanced, the carrier separation efficiency is improved, and the composite material is successfully applied to high-sensitivity detection of PFOA.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic functional materials and sensor technology, and in particular to a method for preparing Fg-C3N4@COF367 optoelectronic composite material and its application. Background Technology

[0002] With industrial development, perfluorooctanoic acid (PFOA) in water bodies has become a serious environmental pollutant due to its persistent degradation and bioaccumulation, necessitating the development of highly sensitive and selective detection methods. Photoelectrochemical (PEC) sensing technology has attracted significant attention due to its low background signal and fast response.

[0003] In the field of optoelectronic sensing technology, graphitic carbon nitride (g-C3N4), as a non-metallic semiconductor material, possesses good chemical stability and visible light response. However, pure g-C3N4 suffers from problems such as small specific surface area, high photogenerated electron-hole recombination rate, and limited light absorption range. Although fluorination modification (Fg-C3N4) can introduce CF bonds and enhance the adsorption of fluorine-containing organic compounds through fluorine-fluorine interactions and hydrogen bonding, its photocurrent response remains weak, and its carrier separation efficiency is low.

[0004] Covalent organic frameworks (COFs), particularly porphyrin-based COF367, possess regular pore structures and excellent light absorption properties. However, no method has been reported in the prior art for preparing optoelectronic composite materials by combining Fg-C3N4 with COF367, and how to construct a tight heterojunction through interface engineering to achieve efficient charge separation remains a technical challenge that is difficult for those skilled in the art to solve. Summary of the Invention

[0005] Purpose of the invention: To address the problems existing in the prior art, this invention provides a method for preparing Fg-C3N4@COF367 optoelectronic composite material and its application. By constructing a heterojunction optoelectronic material composed of Fg-C3N4 and COF367, the light absorption capacity of the composite material is enhanced, its carrier separation efficiency is improved, and the composite material is successfully applied to the high-sensitivity detection of PFOA.

[0006] Technical solution: In a first aspect, the present invention provides a method for preparing Fg-C3N4@COF367 optoelectronic composite material, comprising the following steps: S1. Preparation of Fg-C3N4: Melamine and ammonium fluoride were simultaneously dissolved in ultrapure water and stirred vigorously to make them homogeneous. The mixed solution was recrystallized to obtain a white solid. The white solid was tempered at high temperature in air for a period of time, cooled, centrifuged, washed, and vacuum dried to obtain Fg-C3N4. S2. Preparation of COF367 precursor solution: 5,10,15,20-tetra(4-aminophenyl)-21H,23H-porphyrin, 2,4,6-trimethylbenzaldehyde and 4,4'-biphenyldicarboxaldehyde were dissolved in a mixed solvent of mesitylene, acetic acid and ethanol, and stirred until homogeneous to obtain COF367 precursor solution; S3. In-situ synthesis of composite material: Fg-C3N4 was added to the COF367 precursor solution, sealed and heated to react, and after cooling, centrifugation, washing and vacuum drying, Fg-C3N4@COF367 optoelectronic composite material was obtained.

[0007] Furthermore, in S1, the molar ratio is 1.6-1.8:1.

[0008] Furthermore, in S1, the specific conditions for the high-temperature tempering are: a temperature of 500-550℃ and a time of 2-4 hours.

[0009] Preferably, in S1, the amount of ultrapure water used is 85-100 mL.

[0010] Preferably, in S1, the specific conditions for centrifugation are: first centrifuge at 3500 rpm for 10 min, then centrifuge at 8500 rpm for 10 min.

[0011] Preferably, in S1, the detergent used for washing is anhydrous ethanol.

[0012] Further, in S2, the molar ratio of 5,10,15,20-tetra(4-aminobenzene)-21H,23H-porphyrin, 2,4,6-trimethylbenzaldehyde and 4,4'-biphenyldicarboxaldehyde is 1:75-80:2.

[0013] Further, in S2, the volume ratio of mesitylene, acetic acid, and ethanol is 1:1:0.2-0.4.

[0014] Preferably, in S2, the specific conditions for centrifugation are: first centrifuge at 2000 rpm for 10 min, then centrifuge at 10000 rpm for 10 min.

[0015] Preferably, in S2, the detergent used for washing is N,N-dimethylformamide.

[0016] Furthermore, in S3, the specific conditions for the heating reaction are: a reaction temperature of 110-120℃ and a reaction time of 22-26h.

[0017] Furthermore, in S3, the amount of Fg-C3N4 added is 20-40 mg.

[0018] In a second aspect, the present invention provides an Fg-C3N4@COF367 optoelectronic composite material prepared by any of the methods described above, wherein the composite material is a Type-I transcontinental heterojunction band structure formed by Fg-C3N4 and COF367.

[0019] Thirdly, the present invention provides an application of the Fg-C3N4@COF367 optoelectronic composite material prepared by any of the methods described above, wherein the composite material is used for optoelectronic sensing detection of perfluorooctanoic acid.

[0020] Further, the detection method includes: dispersing the Fg-C3N4@COF367 optoelectronic composite material in ethanol, then spot-coating it onto a glassy carbon electrode to obtain a modified glassy carbon electrode; then spot-coating the perfluorooctanoic acid solution to be tested onto the surface of the modified glassy carbon electrode, and performing photocurrent detection in an electrolyte containing 0.05M NaSO4 and 0.1M ascorbic acid.

[0021] Explanation of the principle: The Fg-C3N4@COF 367 optoelectronic composite material prepared in this invention significantly improves the optoelectronic performance of the material through the synergistic effect of structure, electron and charge separation. Fg-C3N4 has a larger specific surface area, optimized electronic structure and hydrogen bonding sites, which can promote the separation of photogenerated carriers and enhance the adsorption capacity for substrates; COF 367, as a two-dimensional covalent organic framework material, has a regular pore structure, good electron transport performance and abundant amino active sites, which can not only provide a stable loading substrate for Fg-C3N4 and expand the contact area between the two, but also construct an efficient electron transport channel. Under illumination, both Fg-C3N4 and COF-367 absorb photons to generate photogenerated electron-hole pairs. Due to the matching of their band structures, photogenerated electrons rapidly transfer from the conduction band of Fg-C3N4 to the conduction band of COF-367, while holes remain in the valence band of Fg-C3N4, resulting in space charge separation. At the same time, the amino group of COF-367 forms hydrogen bonds with the fluorine atoms of Fg-C3N4, further accelerating electron transfer, effectively suppressing the recombination of photogenerated electron-hole pairs, improving carrier utilization, and ultimately significantly enhancing the photocurrent.

[0022] Beneficial effects: Compared with the prior art, the specific beneficial effects of this invention are as follows: 1. Excellent photoelectric performance: The Fg-C3N4 and COF367 constructed in this invention form a Type-I transcontinental heterojunction band structure (Fg-C3N4 conduction band -0.98 eV, valence band 1.8 eV; COF367 conduction band -0.38 eV, valence band 1.41 eV). This structure effectively promotes the separation and transfer of photogenerated electron-hole pairs, effectively reduces the photogenerated carrier recombination rate, and enhances photoelectric performance. Tests show that the photocurrent intensity of the composite material is approximately four times higher than that of pure Fg-C3N4, significantly improving the signal-to-noise ratio of the sensor.

[0023] 2. Strong interfacial stability: The in-situ synthesis strategy allows the imine bond (-C=N-) of COF367 to undergo a condensation reaction with the amino (-NH2) or hydroxyl (-OH) groups on the surface of Fg-C3N4, forming C=NC or CN covalent bonds. This ensures strong chemical bonding and uniform dispersion between Fg-C3N4 and COF367, which significantly improves the mechanical stability and recyclability of the material and avoids the performance degradation problems commonly found in sensing applications.

[0024] 3. Environmental friendliness and practicality: The preparation method provided by this invention uses a mild solvent system (such as ethanol and methylbenzene), avoiding the use of toxic reagents and conforming to the principles of green chemistry. A composite material with good photoelectric properties is synthesized through a simple solvothermal method; the preparation process is simple and has low risk.

[0025] 4. Excellent detection performance: The composite material prepared by this invention has a large specific surface area, which increases the contact area with the substrate. It can specifically adsorb perfluorooctanoic acid through FF action, thereby enhancing the detection effect of the prepared Fg-C3N4@COF 367 composite material on PFOA. Attached Figure Description

[0026] Figure 1 SEM image of the composite material Fg-C3N4@COF 367 prepared in this invention; Figure 2 The graph shows the photoelectric performance verification results of (A) Fg-C3N4 and (B) Fg-C3N4@COF 367 prepared in this invention. Figure 3 The ultraviolet-visible absorption spectra of (A) Fg-C3N4, (B) COF 367, and (C) Fg-C3N4@COF 367 prepared in this invention are shown. Figure 4 The image shows the band structure of the Fg-C3N4@COF 367 optoelectronic composite material prepared in this invention. Figure 5The photocurrent response spectra of different concentrations of PFOA were detected for the Fg-C3N4@COF 367 optoelectronic composite material prepared in this invention. Detailed Implementation

[0027] The present invention will now be described in detail with reference to the embodiments.

[0028] The chemical reagents used in the embodiments of this invention were sourced from: melamine (purchased from Sinopharm Group), ammonium fluoride (purchased from West Asia Reagent), 5,10,15,20-tetra(4-aminobenzene)-21H,23H-porphyrin, 2,4,6-trimethylbenzaldehyde, 4,4'-biphenyldicarboxaldehyde, mesitylene, anhydrous ethanol, glacial acetic acid, and N,N-dimethylformamide (all purchased from Aladdin).

[0029] Implementation method 1: Preparation of Fg-C3N4@COF367 composite material 1. Preparation of Fg-C3N4: 4g of melamine and 0.67g of ammonium fluoride were dissolved together in 85mL of ultrapure water and stirred vigorously for 2h to make them homogeneous. The mixture was then recrystallized to obtain a white solid. The white solid was placed in a crucible and placed in a muffle furnace and tempered in air at 550ºC for 4h. After cooling to room temperature, the reaction mixture was centrifuged at 3500rpm for 10min and then centrifuged at 8500rpm for 10min to collect Fg-C3N4. The mixture was washed with anhydrous ethanol and dried under vacuum to obtain a yellow solid.

[0030] 2. Preparation of Fg-C3N4@COF367: 27 mg H2TAPP (5,10,15,20-tetra(4-aminophenyl)-21H,23H-porphyrin), 472 mg TBA (2,4,6-trimethylbenzaldehyde), and 16.8 mg BPDA (4,4'-biphenyldicarboxaldehyde) were dissolved in a mixture of 10 mL mesitylene, 0.3 mL acetic acid, and 10 mL ethanol. The mixture was stirred at room temperature, and 30 mg Fg-C3N4 powder was added during stirring. After stirring for another 30 minutes, the mixture was sealed and heated at 120 °C for 24 hours. After cooling to room temperature, the reaction mixture was centrifuged at 2000 rpm for 10 minutes, and then Fg-C3N4@COF 367 was collected by high-speed centrifugation at 10000 rpm for 10 minutes. The mixture was washed with DMF (N,N-dimethylformamide) and dried under vacuum to obtain a powder. Implementation Method 2:

[0031] This embodiment is largely the same as Embodiment 1, except that 20 mg of Fg-C3N4 powder is used in this embodiment. Implementation Method 3:

[0032] This embodiment is largely the same as Embodiment 1, except that 40 mg of Fg-C3N4 powder is used in this embodiment. Implementation Method 4:

[0033] Construction and Testing of PFOA Photoelectrochemical Sensors 1. Electrode modification: Take 5 mg of the Fg-C3N4@COF367 composite material prepared in Example 1 and ultrasonically disperse it in ethanol to obtain a dispersion; take 5 μL of the dispersion and drop it onto the surface of the pretreated glassy carbon electrode, and let it air dry naturally; then spot the PFOA solution to be detected onto the glassy carbon electrode, and after drying, wash it with ultrapure water to remove excess ions on the surface to obtain the modified glassy carbon electrode.

[0034] 2. Electrochemical testing: A three-electrode system was constructed using a modified glassy carbon electrode as the working electrode, a platinum wire as the counter electrode, and Ag / AgCl as the reference electrode.

[0035] 3. Detection process: In an electrolyte containing 10 mL of 0.05 M Na2SO4 and 10 mL of 0.1 M ascorbic acid (AA), an IT (current-time) test was performed under ultraviolet light.

[0036] 4. Performance and Analysis: When PFOA is spot-coated onto the modified glassy carbon electrode, PFOA molecules adsorb onto the surface of the Fg-C3N4@COF367 composite material through fluorine-fluorine interactions, hindering electron transfer and resulting in a significant decrease in photocurrent signal. Quantitative detection is achieved by observing the linear relationship between the decrease in photocurrent and the PFOA concentration.

[0037] Figure 1 The image shows a SEM image of Fg-C3N4@COF367. The image shows that Fg-C3N4 has a lamellar morphology and spherical COF367 on the surface of the lamellars, which confirms that the composite material was successfully prepared.

[0038] Figure 2 The results indicate that the cathode photocurrent of Fg-C3N4@COF367 is about 4 times stronger than that of pure Fg-C3N4, further demonstrating that the Fg-C3N4@COF367 composite material has better photoelectric properties.

[0039] Figure 3 , Figure 4 The successful synthesis of Fg-C3N4 and Fg-C3N4@COF367 heterojunctions can be seen.

[0040] Figure 5These are the IT curves for different concentrations of PFOA, where a represents no PFOA, and b to e represent PFOA concentrations gradually decreasing from high to low. As can be seen from the graph, the higher the PFOA concentration, the smaller the current.

[0041] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing an Fg-C3N4@COF367 optoelectronic composite material, characterized in that, Includes the following steps: S1. Preparation of Fg-C3N4: Melamine and ammonium fluoride were simultaneously dissolved in ultrapure water and stirred vigorously to make them homogeneous. The mixed solution was recrystallized to obtain a white solid. The white solid was tempered at high temperature in air for a period of time, cooled, centrifuged, washed, and vacuum dried to obtain Fg-C3N4. S2. Preparation of COF367 precursor solution: 5,10,15,20-tetra(4-aminophenyl)-21H,23H-porphyrin, 2,4,6-trimethylbenzaldehyde and 4,4'-biphenyldicarboxaldehyde were dissolved in a mixed solvent of mesitylene, acetic acid and ethanol, and stirred until homogeneous to obtain COF367 precursor solution; S3. In-situ synthesis of composite material: Fg-C3N4 was added to the COF367 precursor solution, sealed and heated to react, and then cooled, centrifuged, washed and vacuum dried to obtain Fg-C3N4@COF367 optoelectronic composite material.

2. The preparation method of the Fg-C3N4@COF367 optoelectronic composite material according to claim 1, characterized in that: In S1, the molar ratio of melamine to ammonium fluoride is 1.6-1.8:

1.

3. The preparation method of the Fg-C3N4@COF367 optoelectronic composite material according to claim 1, characterized in that: In S1, the specific conditions for high-temperature tempering are: temperature of 500-550℃ and time of 2-4h.

4. The preparation method of the Fg-C3N4@COF367 optoelectronic composite material according to claim 1, characterized in that: In S2, the molar ratio of 5,10,15,20-tetra(4-aminobenzene)-21H,23H-porphyrin, 2,4,6-trimethylbenzaldehyde and 4,4'-biphenyldicarboxaldehyde is 1:75-80:

2.

5. The preparation method of the Fg-C3N4@COF367 optoelectronic composite material according to claim 1, characterized in that: In S2, the volume ratio of mesitylene, acetic acid, and ethanol is 1:1:0.2-0.

4.

6. The preparation method of the Fg-C3N4@COF367 optoelectronic composite material according to claim 1, characterized in that: In S3, the specific conditions for the heating reaction are: the reaction temperature is 110-120℃ and the reaction time is 22-26h.

7. The preparation method of the Fg-C3N4@COF367 optoelectronic composite material according to claim 1, characterized in that: In S3, the amount of Fg-C3N4 added is 20-40 mg.

8. An Fg-C3N4@COF367 optoelectronic composite material prepared by the method according to any one of claims 1-7, characterized in that: The composite material is a Type-I transcontinental heterojunction band structure formed by Fg-C3N4 and COF367.

9. The application of the Fg-C3N4@COF367 optoelectronic composite material according to claim 8, characterized in that: The composite material is used for photoelectric sensing detection of perfluorooctanoic acid (PFOA).

10. The application of the Fg-C3N4@COF367 optoelectronic composite material according to claim 9, characterized in that, The detection method includes: dispersing the Fg-C3N4@COF367 photoelectric composite material in ethanol, then spot-coating it onto a glassy carbon electrode to obtain a modified glassy carbon electrode; then spot-coating the perfluorooctanoic acid solution to be tested onto the surface of the modified glassy carbon electrode, and performing photocurrent detection in an electrolyte containing 0.05M NaSO4 and 0.1 M ascorbic acid.

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