Pentagonal porphyrin-based covalent organic framework material as well as preparation method and application thereof

Abstract

The invention discloses a pentagonal porphyrinyl covalent organic framework material as well as a preparation method and application thereof. According to the material, 5, 10, 15, 20-tetra (4-aminophenyl) nickel porphyrin and N, N '-bis (4-formylphenyl)-N, N'-diphenyl benzidine are used as construction units, and a two-dimensional covalent organic framework structure with pentagonal pore topological characteristics is formed through a Schiff base condensation reaction. Ni-N4 coordination structures which are uniformly distributed in the material construct catalytic sites similar to a natural enzyme active center in a non-uniform pore microenvironment, and the material shows excellent and stable peroxidase-like catalytic activity. The preparation method of the material has the advantages of clear process steps and mild reaction conditions, and is suitable for stable and repeated preparation. A catechol inhibition type colorimetric sensing system constructed on the basis of the material has good analysis performance in the aspects of detection linear range, detection limit and the like and does not need to depend on large-scale instruments and equipment, and a detection result can be observed through naked eyes.

Description

Technical Field

[0001] This invention relates to the field of functional materials preparation and application technology, specifically to a pentagonal porphyrin-based covalent organic framework material and its preparation method, as well as the application of this material in colorimetric detection of catechols. Background Technology

[0002] Catechols (CC) are naturally occurring phenolic compounds widely distributed in food, aquatic environments, and biological systems. They play important roles in various redox biological processes and are often used as model substrates for studying oxidative stress responses and enzyme catalytic behavior. However, catechols are also typical environmental pollutants with significant toxicity and strong persistence in the environment. Studies have shown that long-term exposure to catechols, even at trace levels, can cause organ damage, DNA damage, and nervous system disorders, and is associated with potential carcinogenic risks. For these reasons, the International Agency for Research on Cancer (IARC), part of the World Health Organization (WHO), has classified catechols as Group 2B carcinogens. Therefore, establishing a sensitive and reliable method for detecting catechols is of great significance for environmental monitoring, food safety, and disease prevention.

[0003] Colorimetric analysis methods based on nanomaterials have attracted widespread attention in recent years due to their advantages such as ease of operation, low cost, intuitive results, and suitability for rapid on-site detection. Among these methods, the orderly introduction of porphyrin units into covalent organic frameworks (COFs) can construct crystalline network materials with regular pore structures and uniformly distributed active sites. These materials structurally mimic the configurational characteristics of the active sites of natural enzymes, and their catalytic performance can be modulated through framework design, thus showing promising applications in the field of sensing. Existing research shows that two-dimensional porphyrin-based COFs often employ highly symmetrical building blocks, forming triangular, square, or hexagonal pore structures. However, due to the high geometric symmetry of their overall structure and relatively uniform pore space, the tunable range of local microenvironments is limited, resulting in shortcomings in substrate enrichment capacity and multifunctional catalysis.

[0004] In contrast, pentagonal porphyrin-based COFs, due to their unique geometric configuration, can break the high symmetry constraints of traditional two-dimensional frameworks, forming a more compact and heterogeneous porous microenvironment within the framework. This is beneficial for enhancing the interaction between substrate molecules and catalytically active sites, thus potentially further improving the catalytic and sensing performance of the material. However, the controllable preparation of pentagonal building blocks remains challenging due to the difficulties in geometric matching and topological assembly. Therefore, developing a structurally controllable porphyrin-based COF with pentagonal pore characteristics and good catalytic performance, and applying it to the highly sensitive colorimetric detection of catechols, has significant research value and application implications. Summary of the Invention

[0005] To address the shortcomings of existing colorimetric detection methods in terms of tunability of the catalytic microenvironment and substrate enrichment capabilities, this invention provides a pentagonal porphyrin-based covalent organic framework material and its preparation method. Based on the peroxidase-like catalytic activity of this material, an inhibitory colorimetric sensing system for catechol detection is constructed.

[0006] To achieve the above objectives, the present invention adopts the following technical solution.

[0007] A method for preparing a pentagonal porphyrin-based covalent organic framework material, characterized by comprising the following steps: (1) 5,10,15,20-tetra(4-aminophenyl)porphyrin nickel and N,N′-bis(4-formylphenyl)-N,N′-diphenylbenzidine were used as reactants and dispersed in a mixed solvent to form a reaction system. After degassing and sealing, the reaction was carried out at 110-130 °C for 60-84 h. (2) After the reaction is complete, the product is separated, washed and dried to obtain the pentagonal porphyrin-based covalent organic framework material; The material is formed by the imine condensation reaction of the two monomers described above to create a two-dimensional structure with a pentagonal channel topology, and its repeating structural unit is shown in Equation 1: Formula 1.

[0008] The application of the aforementioned pentagonal porphyrin-based covalent organic framework material is characterized by: The pentagonal porphyrin-based covalent organic framework material is used in a colorimetric detection method based on the inhibition of its peroxidase-like activity by a target analyte, wherein the target analyte is catechol.

[0009] The pentagonal porphyrin-based covalent organic framework material is abbreviated as NiPor-BATA-COF.

[0010] Compared with the prior art, the present invention has the following beneficial effects:

[0011] (1) The preparation method of NiPor-BATA-COF provided by the present invention has clear process steps, mild reaction conditions, and simple post-processing, and has good operability and repeatability.

[0012] (2) The constructed pentagonal channel two-dimensional covalent organic framework structure breaks through the limitations of traditional two-dimensional COFs which are restricted by high symmetry structure to a certain extent, and realizes effective control of the pore microenvironment.

[0013] (3) The uniformly distributed Ni–N4 coordination structure in the NiPor-BATA-COF constructs a catalytic microenvironment similar to the active site of a natural enzyme in the spatially confined irregular pores, which is conducive to the enrichment of substrate molecules and their interaction with the active site, thus exhibiting excellent peroxidase-like activity.

[0014] (4) The catechol-inhibiting colorimetric sensing system constructed based on the NiPor-BATA-COF is superior to existing colorimetric detection methods in terms of detection linear range and detection limit. It does not rely on large instruments and equipment, and the detection results can be observed with the naked eye. It is easy to operate and has a low cost. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the synthesis of NiPor-BATA-COF and a schematic diagram of its principle for colorimetric detection of catechols.

[0016] Figure 2 This is a scanning electron microscope image of NiPor-BATA-COF.

[0017] Figure 3 This is a transmission electron microscope image of NiPor-BATA-COF.

[0018] Figure 4 This is the elemental analysis diagram of NiPor-BATA-COF.

[0019] Figure 5 This is the X-ray photoelectron spectrum of NiPor-BATA-COF.

[0020] Figure 6 This is the Fourier transform infrared spectrum of NiPor-BATA-COF.

[0021] Figure 7 It is the UV-Vis absorption spectrum of NiPor-BATA-COF peroxidase activity.

[0022] Figure 8 (A) UV-Vis absorption spectra of catechol at different concentrations and (B) linear relationship between absorbance at 652 nm and catechol concentration. Detailed Implementation

[0023] The specific embodiments of the present invention will now be clearly and completely described with reference to the accompanying drawings. It should be understood that the implementation of the present invention is not limited to the following embodiments, and those skilled in the art can make various modifications or substitutions without departing from the spirit and essence of the present invention.

[0024] Unless otherwise stated, the reagents, materials and experimental conditions used in the examples are standard conditions in the art or as recommended by the reagent supplier.

[0025] Example 1: Synthesis of NiPor-BATA-COF

[0026] like Figure 1 As shown, NiPor-BATA-COF is prepared via Schiff base condensation reaction, and the specific steps are as follows:

[0027] (1) 14.6 mg of 5,10,15,20-tetra(4-aminophenyl)porphyrin nickel and 24.0 mg of N,N'-bis(4-formylphenyl)-N,N'-diphenylbenzidine were dispersed in a heat-resistant glass tube containing 1.0 mL of 1,2-dichlorobenzene, 1.0 mL of n-butanol and 0.2 mL of acetic acid aqueous solution and sonicated for 20 min.

[0028] (2) The reaction system was subjected to three liquid nitrogen freezing-degassing cycles, and the tube was sealed under negative pressure. Then, the reaction was heated at 120 °C for 72 h.

[0029] (3) After the reaction is completed, the precipitate in the reaction system is collected, and the crude product is obtained by centrifugation. The precipitate is washed with acetone and tetrahydrofuran in sequence until the washing liquid is colorless. Then it is dried under vacuum at 80 °C for 12 h to obtain the target product NiPor-BATA-COF.

[0030] Example 2 Characterization of NiPor-BATA-COF

[0031] (1) such as Figure 2 and Figure 3 As shown, the scanning electron microscope and transmission electron microscope images of NiPor-BATA-COF reveal that the material exhibits a spherical aggregate structure composed of nanoparticles interconnected with each other, with an average diameter of approximately 800 nm.

[0032] (2) such as Figure 4 As shown, the elemental distribution results indicate that C, N, O, and Ni elements are uniformly distributed in NiPor-BATA-COF.

[0033] (3) such as Figure 5 As shown, the X-ray photoelectron spectra at 285.0, 400.1, 532.9 and 856.0 eV correspond to the characteristic peaks of C 1s, N 1s, O 1s and Ni 2p, respectively.

[0034] (4) such as Figure 6 As shown, in the Fourier transform infrared spectrum, 1626 cm⁻¹ −1The characteristic peak of C=N stretching vibration appears at 1692 cm⁻¹. −1 The characteristic peak intensity decreased significantly, indicating that the Schiff base structure was successfully formed. Furthermore, at 1001 cm⁻¹... −1 Ni–N related vibration peaks were observed at the location.

[0035] The above results indicate that NiPor-BATA-COF was successfully synthesized.

[0036] Example 3: Investigating the peroxidase-like activity of NiPor-BATA-COF

[0037] (1) Take 10 μL of NiPor-BATA-COF dispersion (2.0 mg·mL) −1 200 μL of TMB solution (5 mM) and 200 μL of H2O2 solution (8 mM) were added to an acetate-sodium acetate buffer (0.2 M, pH 4.0) and reacted at 35 °C for 25 min.

[0038] (2) such as Figure 7 As shown, under the coexistence of NiPor-BATA-COF and H2O2, TMB shows a significant absorption peak at 652 nm, and the system color changes from colorless to blue, indicating that NiPor-BATA-COF has peroxidase-like catalytic activity.

[0039] Example 4: Colorimetric Detection of Catechols Based on NiPor-BATA-COF

[0040] (1) Under the above optimal reaction conditions, different concentrations of catechol solutions and 10 μL of NiPor-BATA-COF (2.0 mg·mL⁻¹) were mixed. −1 200 μL of TMB (5 mM) and 200 μL of H2O2 (8 mM) were added to an acetate-sodium acetate buffer (0.2 M, pH 4.0) and reacted at 35 °C for 25 min.

[0041] (2) such as Figure 8 As shown, within the 0-350 μM range, the absorbance of the system at 652 nm gradually decreases with increasing catechol concentration. A good linear relationship is observed within the 2-300 μM range, with the linear regression equation being Y = −0.0023X + 0.7562, R0. 2 = 0.9977, detection limit is 0.16 μM.

[0042] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the scope of protection of the present invention in any way. Any equivalent substitutions, modifications, or variations made by those skilled in the art to the above embodiments without departing from the spirit and substance of the present invention shall fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing a pentagonal porphyrin-based covalent organic framework material, characterized in that, The method comprises the following steps: (1) dispersing 5,10,15,20-tetra(4-aminophenyl)porphyrin nickel and N,N'-bis(4-formylphenyl)-N,N'-diphenylbenzidine as reaction monomers in a mixed solvent to form a reaction system, degassing and sealing, and then reacting at 110-130 °C for 60-84 h; (2) after the reaction is completed, the obtained product is separated, washed and dried to obtain the pentagonal porphyrin-based covalent organic framework material; The material is formed by imine condensation reaction of the two monomers to have a two-dimensional structure with pentagonal channel topology, and the repeat structure unit is shown in formula 1: Formula 1.

2. Application of the pentagonal porphyrin-based covalent organic framework material according to claim 1, characterized in that: The pentagonal porphyrin-based covalent organic framework material is used in a colorimetric detection method based on the peroxidase-like activity of the material being inhibited by a target object, and the target object is catechol.

Images