Porphyrin functionalized carbon nanotube compound and preparation method thereof

Abstract

The invention provides a porphyrin functionalized carbon nanotube compound. Medium-tetra (4-carboxyphenyl) porphyrin is covalently connected to the surface of an aminated carbon nanotube through an amido bond to form the compound. Stable amido bond connection is formed through amino-carboxyl condensation, and the bond energy is obviously higher than that of an ester bond. The invention also provides a preparation method of the porphyrin functionalized carbon nanotube compound, which comprises the following steps: carrying out carboxyl activation treatment on the meso-tetra (4-carboxyl phenyl) porphyrin by adopting a catalytic system consisting of N, N '-dicyclohexylcarbodiimide and N-hydroxysuccinimide; the preparation method comprises the following steps: performing ultrasonic treatment on aminated carbon nanotubes in N, N-dimethylformamide, adding the aminated carbon nanotubes into an activated meso-tetra (4-carboxyphenyl) porphyrin solution prepared in the step 1, performing stirring reaction at room temperature, and performing suction filtration and freeze drying to obtain a target product, namely the porphyrin functionalized carbon nanotube compound. A mild room-temperature stirring process is adopted, so that the dependence of a solvothermal method on high-temperature and high-pressure equipment is completely avoided, and the production cost is remarkably reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of organic-inorganic functional composite materials, and relates to a porphyrin-functionalized carbon nanotube composite and a preparation method thereof. Background Art

[0002] As a class of organic molecules with a large π-conjugated structure, porphyrins exhibit important application values in the fields of photocatalysis, sensors, and electrochemistry due to their excellent optoelectronic properties. However, pure porphyrin materials generally suffer from problems such as low charge transfer efficiency and poor structural stability, which restrict their practical application performance. To address this technical bottleneck, researchers have attempted to composite porphyrins with carbon nanotubes (CNTs), taking advantage of the unique one-dimensional tubular structure, high conductivity, and large specific surface area of CNTs to construct efficient interfacial charge transfer channels. For example, a composite material of carbon nanotubes coated with a Sn-TCPP-Sn network polymer prepared by a solvothermal method, and a composite material formed by covalently binding cobalt porphyrin and carboxylated carbon nanotubes through an ester bond. These composite materials exhibit excellent performance in adsorption and catalytic oxidation activities. However, existing preparation methods generally have problems such as complex processes (e.g., the solvothermal method requires high temperature and high pressure), insufficient bonding stability (e.g., ester bonds are prone to hydrolysis), or the need to use metal catalysts. Summary of the Invention

[0003] The present invention provides a porphyrin-functionalized carbon nanotube composite, which solves the problem of poor structural stability of the composite in the prior art.

[0004] The present invention also provides a preparation method of a porphyrin-functionalized carbon nanotube composite, which solves the problems of complex process and poor stability in the prior art.

[0005] The technical solution of the present invention is realized as follows: A porphyrin-functionalized carbon nanotube composite is a composite formed by meso-tetrakis(4-carboxyphenyl)porphyrin covalently bonded to the surface of amino-functionalized carbon nanotubes through an amide bond. Through a covalent coupling strategy mediated by N,N'-dicyclohexylcarbodiimide and N-hydroxysuccinimide, the efficient and stable binding of meso-tetrakis(4-carboxyphenyl)porphyrin and amino-functionalized carbon nanotubes is achieved. The amide bond is formed by the directional condensation of carboxyl (-COOH) and amino (-NH2), which can precisely integrate the light-harvesting / catalytic properties of porphyrins with the high conductivity and mechanical strength of carbon nanotubes, thereby significantly improving the electrochemical activity and long-term cycling stability of the composite material. This invention provides an innovative material basis for the development of high-performance photocatalytic materials (such as CO2 reduction, water splitting), highly sensitive biosensors, and efficient energy storage devices (such as supercapacitors, battery electrodes), and has important scientific value and application prospects.

[0006] Furthermore, a complex is formed by the covalent bonding of meso-tetra(4-carboxyphenyl) porphyrin molecules through their carboxylic acid groups with the surface active sites of amino-functionalized carbon nanotubes. The four carboxylic acid groups on a single porphyrin molecule selectively interact with the four amino groups of 1 to 4 carbon nanotubes. Among them, the four amino groups come from 1 or 2 or 3 or 4 carbon nanotubes.

[0007] A method for preparing a porphyrin-functionalized carbon nanotube complex includes the following steps: Step 1, perform carboxyl activation treatment on meso-tetra(4-carboxyphenyl) porphyrin using a catalytic system composed of N,N'-dicyclohexylcarbodiimide and N-hydroxysuccinimide; Step 2, ultrasonicate the amino-functionalized carbon nanotubes in N,N-dimethylformamide, add them to the activated meso-tetra(4-carboxyphenyl) porphyrin solution prepared in Step 1, stir and react at room temperature, filter by suction, and freeze-dry to obtain the target product, the porphyrin-functionalized carbon nanotube complex.

[0008] Furthermore, the molar ratio of meso-tetra(4-carboxyphenyl) porphyrin, N,N'-dicyclohexylcarbodiimide, and N-hydroxysuccinimide is 1:(4 - 5):(4 - 5).

[0009] Furthermore, the mass ratio of meso-tetra(4-carboxyphenyl) porphyrin to the amino-functionalized carbon nanotubes is 97 - 210:700.

[0010] Furthermore, the mass of meso-tetra(4-carboxyphenyl) porphyrin is 21 mg, the mass of N,N'-dicyclohexylcarbodiimide is 26.4 mg, the mass of N-hydroxysuccinimide is 14.7 mg, and the amino-functionalized carbon nanotubes are amino-functionalized multi-walled carbon nanotubes with a mass of 70 mg.

[0011] Furthermore, in Step 1, dissolve N,N'-dicyclohexylcarbodiimide, N-hydroxysuccinimide, and meso-tetra(4-carboxyphenyl) porphyrin in a 10 mL N,N-dimethylformamide solvent system at room temperature, and react under the protection of an inert gas such as nitrogen or argon by reflux for 24 hours.

[0012] Furthermore, in Step 2, ultrasonically disperse the amino-functionalized carbon nanotubes in 5 mL of N,N-dimethylformamide solvent for 3 hours, add the dispersion to the activated meso-tetra(4-carboxyphenyl) porphyrin solution prepared in Step 1, and stir and react at room temperature for 72 hours.

[0013] Further, the specific process of suction filtration in Step 2 is as follows: First, solid-liquid separation is achieved through vacuum suction filtration, and then the obtained solid-phase product is washed with anhydrous methanol and subjected to vacuum suction filtration to completely remove the residual N,N-dimethylformamide. Then, the solid-phase product is washed twice with chloroform and the unreacted meso-tetrakis(4-carboxyphenyl)porphyrin is removed by vacuum suction filtration.

[0014] In the present invention, meso-tetrakis(4-carboxyphenyl)porphyrin is covalently bonded to the surface of amino-functionalized carbon nanotubes (CNT-NH2). The present invention covalently bonds meso-tetrakis(4-carboxyphenyl)porphyrin to the surface of CNT-NH2 through an amide reaction to prepare an organic-inorganic covalently functionalized nanocomposite material, rather than simply physically mixing these two different optical functional materials. The prepared material has very broad application prospects in the fields of electrochemistry, photocatalysis, and biosensing compared with traditional materials.

[0015] The beneficial effects of the present invention are as follows: A porphyrin-functionalized carbon nanotube composite of the present invention forms stable amide bonds through amino-carboxyl condensation, and the bond energy is significantly higher than that of ester bonds, fundamentally solving the stability problem of traditional connection methods in acidic and alkaline environments.

[0016] A preparation method of a porphyrin-functionalized carbon nanotube composite of the present invention, a preparation method of a porphyrin-carbon nanotube composite based on room-temperature amidation reaction. First, a mild room-temperature stirring process is adopted, completely avoiding the dependence on high-temperature and high-pressure equipment in the solvothermal method, and significantly reducing the production cost; the entire preparation process does not require metal catalysts or complex pre-modification steps, and the raw materials are all industrially available products, with high reaction selectivity and easy large-scale production. This innovative method provides a new technical route for the preparation of high-performance porphyrin-carbon nanotube composites and has broad application prospects in the fields of energy conversion, environmental governance, etc.

[0017] The present invention relates to a method for covalently connecting meso-tetrakis(4-carboxyphenyl)porphyrin to amino-functionalized carbon nanotubes through an amidation reaction. Based on the amidation reaction between carboxylic acid groups and amino groups, using N,N'-dicyclohexylcarbodiimide and N-hydroxysuccinimide as activators, the covalent modification of porphyrin molecules on the surface of carbon nanotubes is successfully realized, and a porphyrin-carbon nanotube composite is synthesized. The covalent connection of meso-tetrakis(4-carboxyphenyl)porphyrin and amino-functionalized carbon nanotubes through amide groups is confirmed by characterization means such as Fourier transform infrared spectroscopy, Raman spectroscopy, nuclear magnetic resonance spectroscopy, and ultraviolet absorption spectroscopy. This covalent binding strategy significantly improves the loading efficiency and stability of porphyrin molecules on the surface of carbon nanotubes. The present invention provides a new idea for designing efficient and stable porphyrin-carbon nanotube composites and has potential application value in the fields of electrochemistry, photocatalysis, and biosensing.

[0018] I. The key reagents used in the implementation process of the present invention, including materials such as meso-tetrakis(4-carboxyphenyl)porphyrin and amino-functionalized multi-walled carbon nanotubes, have significant advantages in terms of the material cost-benefit ratio compared with control materials such as amino porphyrin and carboxylated carbon nanotubes commonly used in conventional synthesis reactions. Specifically, the functionalized porphyrin derivatives and carbon nanotube materials selected in the present invention have a lower procurement cost per unit mass than traditional reagents on the premise of maintaining the same catalytic activity and structural stability.

[0019] II. The present invention obtains an amide-functionalized porphyrin-functionalized carbon nanotube composite TCPP-CNT through the covalent binding between carboxyl functional groups and amino functional groups. The dosage required for their combination is less, which is a method for realizing the efficient synthesis of this composite material.

[0020] III. When the composite prepared in the present invention is used as an electrode material, its composite structure can also optimize the specific capacity and cycle stability of the battery, showing broad potential for energy applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0022] Figure 1 It is the preparation flow chart of the TCPP-CNT composite prepared by the present invention; Figure 2 It is the Fourier transform infrared absorption spectra of TCPP, CNT-NH2, and TCPP-CNT; Figure 3 It is the ultraviolet-visible absorption spectra of TCPP, CNT-NH2, and TCPP-CNT; Figure 4 It is the Raman spectra of CNT-NH2 and TCPP-CNT; Figure 5 It is the nuclear magnetic resonance hydrogen spectrum of TCPP; Figure 6 It is the nuclear magnetic resonance hydrogen spectrum of TCPP-CNT; Figure 7 It is the scanning electron microscope image of TCPP-CNT; Figure 8 It is the structure diagram of the TCPP-CNT prepared by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0024] This embodiment provides a preparation method of a porphyrin-functionalized carbon nanotube composite TCPP-CNT: Weigh 21 mg of meso-tetrakis(4-carboxyphenyl)porphyrin (TCPP), 26.4 mg of N,N'-dicyclohexylcarbodiimide, and 14.7 mg of N-hydroxysuccinimide into a round-bottom flask, and then add 10 mL of N,N-dimethylformamide. Under an argon inert atmosphere, reflux for 24 hours; then weigh 70 mg of amino-functionalized carbon nanotubes CNT-NH2 and ultrasonicate in 5 mL of N,N-dimethylformamide for 3 hours, add it to the activated meso-tetrakis(4-carboxyphenyl)porphyrin solution, and stir and react at room temperature for 72 hours. Subsequently, solid-liquid separation is achieved by vacuum filtration. The obtained solid-phase product is washed with anhydrous methanol and vacuum filtered to completely remove the residual N,N-dimethylformamide. Then, the solid-phase product is washed twice with chloroform and the unreacted meso-tetrakis(4-carboxyphenyl)porphyrin is removed by vacuum filtration, and freeze-dried to obtain the composite TCPP-CNT. The meso-tetrakis(4-carboxyphenyl)porphyrin molecule forms a covalent bond with the surface active sites of the amino-functionalized carbon nanotubes through its carboxylic acid groups, and the four carboxyl groups on a single porphyrin molecule selectively interact with the four amino groups of 1 to 4 carbon nanotubes.

[0025] For the physicochemical characterization of this composite, Fourier transform infrared spectroscopy, ultraviolet-visible absorption spectroscopy, Raman spectroscopy, nuclear magnetic resonance spectroscopy, and SEM analysis are performed on this material.

[0026] Figure 1 It is the process flow chart for the preparation of the composite TCPP-CNT.

[0027] Figure 2 It is the Fourier transform infrared spectrum. The peaks of CNT-NH2 at 3628 cm -1 and 3437 cm -1 are attributed to the stretching vibration of free N-H. After amidation, these two peaks of TCPP-CNT disappear, and a broad peak appears at 3445 cm -1 indicating that the amino group (-NH2) participates in the reaction to form an amide bond (-CONH-), resulting in a decrease in free N-H. The new broad peak originates from the N-H stretching vibration of the amide bond (usually located at 3300-3500 cm -1), and broadened due to hydrogen bonding. The peak of meso - tetra(4 - carboxyphenyl)porphyrin at 1687 cm -1 is attributed to the stretching vibration frequency of C=O in the carboxyl group. This peak disappears in TCPP - CNT and a new peak appears at 1631 cm -1 , corresponding to the stretching vibration frequency of C=O of the amide bond (usually located at 1630 - 1680 cm -1 ), confirming that the carboxyl group reacts with the amino group to form an amide bond. The peak at 1592 cm -1 is the N - H bending vibration of the amide bond, further supporting the formation of the amide bond.

[0028] Figure 3 is the ultraviolet - visible absorption spectrum (UV - Vis). Among them, the meso - tetra(4 - carboxyphenyl)porphyrin molecule (TCPP) shows a typical Soret - band characteristic absorption peak at 419 nm, corresponding to the π - π electron transition of the porphyrin ring; at the same time, four Q - band absorption peaks are observed at 514, 549, 590, and 646 nm, reflecting the vibration fine structure of the porphyrin ring. After covalent modification, the ultraviolet - visible absorption spectrum of the TCPP - CNT complex shows significant changes: the Soret band undergoes a slight red - shift and is accompanied by obvious band broadening. This spectral change is mainly attributed to: (1) the covalent connection between TCPP and CNT - NH2, resulting in the redistribution of the electron cloud density of the porphyrin ring; (2) the charge - transfer interaction between TCPP and CNT - NH2. The Q - band absorption peaks also shift to 516, 555, 592, and 647 nm correspondingly, further confirming the existence of the intermolecular electron coupling effect. In line with the results of infrared spectroscopy analysis, the slight red - shift of the Soret band (instead of the large - scale shift caused by usual π - π stacking) combined with the infrared characteristic peak of the characteristic amide bond (1631 cm -1 ) proves that TCPP and CNT - NH2 are mainly combined by covalent bonding rather than physical adsorption.

[0029] Figure 4 is the Raman spectrum. The figure shows the functionalization of TCPP and CNT - NH2. The Raman spectrum of CNT - NH2 shows characteristic vibration peaks at 1339 cm -1 (D band) and 1569 cm -1 (G band), corresponding to the structural defects of the graphite lattice (sp³ - hybridized carbon) and the in - plane stretching vibration of sp² - hybridized carbon atoms respectively. And, the G' band at 2674 cm⁻¹ appears as the second - harmonic frequency peak of the D band, and its intensity ratio (I D / I G= 1.22) quantitatively reflects the defect density of carbon nanotubes. After functionalization with meso-tetrakis(4-carboxyphenyl)porphyrin, the Raman spectrum of the TCPP-CNT composite changes significantly: (1) The G band shifts to a higher wavenumber of 1572 cm -1 , indicating that the electron cloud density of the CNT changes due to covalent bonding; (2) The D band is slightly red-shifted to 1337 cm -1 , and at the same time, the I D / I G ratio decreases to 1.13, confirming that TCPP is covalently linked to CNT-NH2 through an amide bond, partially repairing the structural defects on the surface of the carbon nanotubes. These spectral changes clearly reveal the charge transfer interaction between TCPP and CNT-NH2: TCPP, as an electron donor, delocalizes its π electrons to the sp² carbon skeleton of the CNT (electron acceptor) through a covalent bond. This result is consistent with the red shift of the Soret band (420 nm) observed in the ultraviolet-visible absorption spectrum, jointly confirming the effective electron coupling effect in the covalently functionalized nanocomposite system.

[0030] Figure 5 And Figure 6 are nuclear magnetic resonance spectra. The present invention confirms the successful construction of the covalent bonding structure of meso-tetrakis(4-carboxyphenyl)porphyrin (TCPP) and amino-functionalized nanotubes (CNT-NH2) through nuclear magnetic resonance hydrogen spectrum (1H NMR) analysis. Specifically, the 1H NMR spectrum of TCPP shows a characteristic resonance peak of the carboxyl (-COOH) proton at a chemical shift of 9.76 ppm, and at the same time, the characteristic signals of the porphyrin ring and benzene ring protons can be seen. As Figure 5 shown, the chemical shift value of characteristic peak a at 9.76 ppm is attributed to the proton characteristic peak of the carboxylic acid group (-COOH). The chemical shift signals labeled from b to h correspond to the resonance peaks of the porphyrin macrocycle conjugated system and benzene ring aromatic protons. In this spectral analysis, the residual proton signals and water peak of the dimethyl sulfoxide (DMSO-d6) solvent are clearly attributed. In the 1H NMR spectrum of TCPP-CNT, the carboxyl proton signal at 9.76 ppm disappears, and a characteristic peak of the amide bond (-CONH-) proton appears at 8.56 ppm. After TCPP and CNT-NH2 combine to form a large-size complex or aggregate, the molecular motion is restricted, the transverse relaxation time is shortened, resulting in a significant broadening of the N-H signal, and finally it is submerged in the baseline noise. As Figure 6 shown, the chemical shift value of characteristic peak a at 8.56 ppm is attributed to the proton characteristic peak of the amide bond (-CONH-), and the characteristic peaks in the range of b to f are attributed to the characteristic absorption of the porphyrin macrocycle conjugated system and benzene ring aromatic protons. The residual proton signals of the dimethyl sulfoxide (DMSO-d6) solvent and the proton signals of the water peak are also marked in the spectrum.

[0031] The above spectroscopic changes indicate that the carboxyl group of TCPP forms a covalent bond with the amino group of CNT-NH2 through an amidation reaction, and the amino-functionalized carbon nanotubes provide electrons to the porphyrin ring through covalent bonds, resulting in an increase in the electron cloud density of the protons on the ring and an enhanced shielding effect. The 1H NMR analysis data provides conclusive evidence from two aspects: chemical shift changes and characteristic peak attribution, proving that TCPP and CNT-NH2 are covalently bound through an amide bond to form a TCPP-CNT complex. Figure 7 Figure 3 shows the scanning electron microscope image of TCPP-CNT. The complex formed by the covalent bonding of meso-tetrakis(4-carboxyphenyl)porphyrin (TCPP) and amino-functionalized carbon nanotubes (CNT-NH2) in the present invention has a complete tubular morphology structure of the carbon nanotubes without obvious changes, indicating that the covalent bonding reaction process has no significant impact on the bulk structure of the carbon nanotubes.

[0032] Figure 8 Figure 4 is the structural diagram of TCPP-CNT prepared in the present invention.

[0033] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A porphyrin-functionalized carbon nanotube composite, characterized in that: A complex formed by covalently linking meso-tetrakis(4-carboxyphenyl)porphyrin to the surface of amino-functionalized carbon nanotubes via amide bonds.

2. The porphyrin-functionalized carbon nanotube composite according to claim 1, wherein: A complex is formed by covalently bonding meso-tetrakis(4-carboxyphenyl)porphyrin molecules to the surface active sites of amino-functionalized carbon nanotubes through their carboxylic acid groups. The four carboxyl groups on a single porphyrin molecule selectively interact with the four amino groups of 1 to 4 carbon nanotubes.

3. A method for preparing the porphyrin-functionalized carbon nanotube composite as described in claim 1 or 2, characterized in that, It includes the following steps: Step 1: Use a catalytic system composed of N,N'-dicyclohexylcarbodiimide and N-hydroxysuccinimide to activate the carboxyl groups of meso-tetrakis(4-carboxyphenyl)porphyrin. Step 2: Ultrasonicate the amino-functionalized carbon nanotubes in N,N-dimethylformamide, add them to the activated meso-tetrakis(4-carboxyphenyl)porphyrin solution prepared in Step 1, stir and react at room temperature, filter by suction, and freeze-dry to obtain the target product, the porphyrin-functionalized carbon nanotube complex.

4. The preparation method of the porphyrin-functionalized carbon nanotube composite according to claim 2, characterized in that: The molar ratio of meso-tetrakis(4-carboxyphenyl)porphyrin, N,N'-dicyclohexylcarbodiimide, and N-hydroxysuccinimide is 1:(4 - 5):(4 - 5).

5. The preparation method of the porphyrin-functionalized carbon nanotube composite according to claim 2, characterized in that: The mass ratio of meso-tetrakis(4-carboxyphenyl)porphyrin to amino-functionalized carbon nanotubes is 97 - 210:

700.

6. The preparation method of the porphyrin-functionalized carbon nanotube composite according to claim 3, wherein: The mass of meso-tetrakis(4-carboxyphenyl)porphyrin is 21 mg, the mass of N,N'-dicyclohexylcarbodiimide is 26.4 mg, the mass of N-hydroxysuccinimide is 14.7 mg, and the amino-functionalized carbon nanotubes are amino-functionalized multi-walled carbon nanotubes with a mass of 70 mg.

7. The preparation method of the porphyrin-functionalized carbon nanotube composite according to claim 3, wherein: In Step 1, N,N'-dicyclohexylcarbodiimide, N-hydroxysuccinimide, and meso-tetrakis(4-carboxyphenyl)porphyrin are dissolved in a 10 mL N,N-dimethylformamide solvent system at room temperature and reacted under reflux for 24 hours under the protection of an inert gas such as nitrogen or argon.

8. The preparation method of the porphyrin-functionalized carbon nanotube composite according to claim 3, characterized in that: In Step 2, the amino-functionalized carbon nanotubes are ultrasonically dispersed in 5 mL of N,N-dimethylformamide solvent for 3 hours, and the dispersion is added to the activated meso-tetrakis(4-carboxyphenyl)porphyrin solution prepared in Step 1, and stirred and reacted at room temperature for 72 hours.

9. The preparation method of the porphyrin-functionalized carbon nanotube composite according to claim 3, characterized in that: The specific process of suction filtration in Step 2 is to first achieve solid-liquid separation by vacuum suction filtration, then wash the obtained solid-phase product with anhydrous methanol and perform vacuum suction filtration to completely remove the residual N,N-dimethylformamide, and then wash the solid-phase product twice with chloroform and remove the unreacted meso-tetrakis(4-carboxyphenyl)porphyrin by vacuum suction filtration.

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