Preparation method and application of novel cadmium-cobalt bimetal organic framework

Abstract

The invention discloses a preparation method and application of a novel cadmium-cobalt bimetal organic framework, and belongs to the technical field of synthesis of bimetal organic frameworks, the method comprises the following steps: S1, synthesizing a cadmium-cobalt bimetal organic framework; according to the present invention, the Cd-Co bimetallic organic frame CdCoBTCHx is synthesized, the Cd-Co bimetallic organic frame CdCoBTCHx has two oxidation states of Co (II) and Co (III), detection signals on cysteine and methionine are significantly enhanced, the Cd-Co bimetallic organic frame has good selectivity on sulfur-containing amino acids, and in addition, the Cd-Co bimetallic organic frame CdCoBTCHx can be used for identifying sulfur-containing amino acids, such that the Cd-Co bimetallic organic frame CdCoBTCHx can be used for identifying sulfur-containing amino acids, and the Cd-Co bimetallic organic frame CdCoBTCHx can be used for identifying sulfur-containing amino acids, such that the Cd-Co bimetallic organic frame CdCoBTCHx can be used for identifying sulfur-containing amino acids. The variable valence state of cobalt in CdCoBTCHx also promotes remarkable electron transfer in the recognition process, and the color of the solution is changed from colorless to yellow, so that a visual recognition effect is provided. Technical reference is provided for rapidly and visually detecting a sulfur-containing compound kit, and the method has important significance in the fields of biological medicine, food detection and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of the synthesis of bimetallic organic frameworks, and particularly relates to a preparation method and application of a novel cadmium-cobalt bimetallic organic framework. Background Art

[0002] Sulfur-containing amino acids play a crucial role in various metabolic processes. At the same time, they are also a type of amino acids that have a greater impact on food flavor during the heat treatment process. As the basic components of polypeptides and proteins, they are also biomarkers for predicting disease risks.

[0003] Metal-organic frameworks (MOFs) are a new type of porous crystalline material developed in the 1990s. They are usually formed by the self-assembly and mutual linkage of transition metal ions and multidentate organic ligands containing oxygen, nitrogen, etc. Mixed-metal MOF materials generally refer to MOFs constructed with two or more different metal ions. Since the inorganic metal sites of single-metal MOFs are limited and relatively single, if other metal systems are introduced, the types of metal sites can be increased and the arrangement patterns will also be more diverse. For example, ZnCo-ZIF-8 synthesized by incorporating Co into ZIF-8 can be prepared into a side-heated gas sensor element after calcination at 600 °C, showing good selectivity in acetone detection. Heterovalent bimetallic MOF materials are relatively rare. A typical example is the CPM-200 series, which is composed of trivalent In 3+ , Ga 3+ matched with divalent Mg 2+ , Mn 2+ and other metals to form heterometallic MOFs, showing excellent selective adsorption ability for CO 2 .

[0004] However, due to the different coordination rates and coordination modes of different metal ions under the same conditions, the self-assembly of bimetallic MOFs and the control of the final products still pose great challenges. Currently, there is a blank in the synthesis of cadmium-cobalt bimetallic organic frameworks, and cadmium-cobalt bimetallic organic frameworks have good effects in the recognition of sulfur-containing amino acids. Summary of the Invention

[0005] To solve the above problems, the present invention provides a preparation method and application of a novel cadmium-cobalt bimetallic organic framework, and the present invention is realized through the following technical solutions.

[0006] A preparation method of a novel cadmium-cobalt bimetallic organic framework, characterized by comprising the following steps:

[0007] S1, synthesis of the cadmium-cobalt bimetallic organic framework;

[0008] Dissolve Cd(NO 3 ) 2 ·4H2 O, Co(NO 3 ) 2 ·6H 2 O, Hx, and H 3 BTC are placed in DMF solvent in a ratio of 2:1:2:1, and after adjusting the pH with HNO 3 , it is sealed in a polytetrafluoroethylene autoclave and heated at a constant temperature, then cooled to room temperature, and filtered and washed to obtain light purple crystals of CdCoBTCHx;

[0009] where Hx is 6-hydroxypurine; H 3 BTC is 1,3,5-benzenetricarboxylic acid; DMF solvent is N,N-dimethylformamide solvent; CdCoBTCHx is a cadmium-cobalt bimetallic organic framework;

[0010] S2, property analysis of CdCoBTCHx crystals.

[0011] Preferably, in the step S1, the concentration of HNO 3 is 1 mol / L; the temperature of the constant-temperature heating is 140 °C and the time is 72 h; after the constant-temperature heating, the temperature of the polytetrafluoroethylene autoclave decreases at a rate of 5 °C / h until it cools to room temperature.

[0012] Preferably, in the step S2, the property analysis of the crystals includes Fourier transform infrared spectrometer analysis, single crystal X-ray diffraction analysis, X-ray powder diffractometer analysis, thermogravimetric analysis and X-ray photoelectron spectroscopy analysis.

[0013] Preferably, the Fourier transform infrared spectrometer analysis is used to determine whether CdCoBTCHx crystals are synthesized.

[0014] Preferably, the single crystal X-ray diffraction analysis is used to determine the single crystal structure of CdCoBTCHx.

[0015] Preferably, the X-ray powder diffractometer analysis is used to determine the purity of CdCoBTCHx.

[0016] Preferably, the thermogravimetric analysis is used to determine the thermal stability of CdCoBTCHx.

[0017] Preferably, the X-ray photoelectron spectroscopy analysis is used to determine the valence state of CdCoBTCHx.

[0018] An application of a cadmium-cobalt bimetallic organic framework, which is used for the recognition of sulfur-containing amino acids.

[0019] The beneficial effects of the present invention are as follows. The present invention synthesizes a cadmium-cobalt bimetallic organic framework CdCoBTCHx, which is prepared from 6-hydroxypurine, 1,3,5-benzenetricarboxylic acid, metal cadmium and cobalt ions. The presence of two oxidation states, Co(II) and Co(III), in CdCoBTCHx significantly enhances the detection signal for cysteine and methionine, showing good selectivity for sulfur-containing amino acids. The ultraviolet-visible absorption spectrum indicates that significant electron transfer occurs between the MOF and the guest molecule. In addition, the variable valence state of cobalt in CdCoBTCHx also promotes significant electron transfer during the recognition process, resulting in a color change of the solution from colorless to yellow, thus providing a visual recognition effect. It provides a technical reference for the realization of a rapid visual detection kit for sulfur-containing compounds and has important significance in the fields of biomedicine, food detection, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the present invention, the drawings required for use in the following description of the specific embodiments will be briefly introduced. Obviously, the drawings in the following description 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.

[0021] Figure 1 : FT-IR diagram of the synthesized product;

[0022] Figure 2 : Single crystal structure of CdCoBTCHx crystal;

[0023] Figure 3 : PXRD diagram of CdCoBTCHx crystal;

[0024] Figure 4 : TGA diagram of CdCoBTCHx crystal;

[0025] Figure 5 : XPS diagram of CdCoBTCHx crystal;

[0026] Figure 6 : UV-visible absorption spectrum change diagram after adding CdCoBTCHx to L-cysteine and L-methionine. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the 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 of 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 belong to the scope of protection of the present invention.

[0028] A preparation method of a novel cadmium-cobalt bimetallic organic framework, comprising the following steps:

[0029] S1, synthesis of the cadmium-cobalt bimetallic organic framework;

[0030] Put Cd(NO 3 ) 2 ·4H 2 O, Co(NO 3 ) 2 ·6H 2 O, Hx, and H 3 BTC in a ratio of 2:1:2:1 in a DMF solvent, adjust the pH by HNO 3 , seal in a polytetrafluoroethylene autoclave and heat at a constant temperature, then cool to room temperature, filter and wash to obtain light purple crystals of CdCoBTCHx;

[0031] where Hx is 6-hydroxypurine; H 3 BTC is 1,3,5-benzenetricarboxylic acid; the DMF solvent is N,N-dimethylformamide solvent; CdCoBTCHx is the cadmium-cobalt bimetallic organic framework.

[0032] The concentration of HNO 3 is 1 mol / L; the temperature of the constant temperature heating is 140 °C and the time is 72 h; after the constant temperature heating, the temperature of the polytetrafluoroethylene autoclave decreases at a rate of 5 °C / h until it cools to room temperature.

[0033] S2, property analysis of the CdCoBTCHx crystal.

[0034] The property analysis of the crystal includes Fourier transform infrared spectrometer analysis (FT-IR), single crystal X-ray diffraction analysis (SCXRD), X-ray powder diffraction analyzer analysis (PXRD), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy analysis (XPS).

[0035] Fourier transform infrared spectrometer analysis is used to determine whether the CdCoBTCHx crystal is synthesized. After filtering and drying the light purple crystals synthesized in step S1, they are tested and characterized by a Fourier transform infrared spectrometer. As Figure 1 shown, the abscissa is the wave number Wavenumbers and the ordinate is the transmittance Transmittance. It can be seen from Figure 1 that: the N-H stretching vibration peak on the 6-hydroxypurine ligand is at around 3132 cm -1 , 1614 cm -1 corresponds to the C=N characteristic absorption peak on the hydroxypurine ligand, 1562 cm -1 , 1439 cm -1 , 1375 cm -1Corresponding to the characteristic absorption peak of the benzene ring on BTC benzene ring, 1107 cm -1 The absorption at -1 corresponds to the C-O stretching vibration on the BTC ligand, 768 cm -1 and 725 cm -1 correspond to the bending vibration of the meta-substituent and C-H on the BTC benzene ring, indicating that CdCoBTCHx has been synthesized. CdCoBTCHx is the cadmium-cobalt bimetallic organic framework.

[0036] Single crystal X-ray diffraction analysis was used to determine the single crystal structure of CdCoBTCHx. Figure 2 In Figure 2 , a shows the asymmetric unit of the CdCoBTCHx crystal, b shows the metal coordination mode, c shows the three-dimensional framework formed along the b-axis direction, and d shows the one-dimensional pore channel of CdCoBTCHx highlighted by the internal view of the Connolly surface.

[0037] The results show that CdCoBTCHx crystallizes in the monoclinic system P2 1 / n space group. The asymmetric unit contains two metal centers (Cd1 / Co1 and Cd2), one 6-hydroxypurine, and one trimesic acid molecule. Among them, the Cd1 / Co1 metal center coordinates with 5 carboxylic acid O atoms from three BTCs, 1 pyrimidine N and 1 imidazole N atom from two Hxs respectively. The two symmetric Cd1 / Co1 metal centers are bridged by two carboxylic acid O atoms, resulting in all the benzene rings of trimesic acid being in the same plane. The Cd2 metal center is connected with 2 carboxylic acid O atoms on one BTC, the pyrimidine N of one Hx, the hydroxyl O atom outside the ring, and the imidazole N atom on another Hx in a pentacoordinated mode. It should be noted that the carboxylic acids on BTC coordinate with the metal in a bidentate coordination mode, and all the N and O atoms on Hx are occupied by the metal. The two independent metal centers are linked by Hx, thus forming a three-dimensional network structure and forming a one-dimensional pore channel of about along the b-axis direction.

[0038] X-ray powder diffractometer analysis was used to determine the purity of CdCoBTCHx. As Figure 3 shown, the CdCoBTCHx crystal was tested by an X-ray powder diffractometer and compared with the standard pattern simulated by the crystal structure. The results show that the diffraction peaks of the test pattern are basically consistent with the simulated pattern, indicating that the obtained crystal has a high quality and purity.

[0039] Thermogravimetric analysis was used to determine the thermal stability of the purity of CdCoBTCHx. As Figure 4 shown, CdCoBTCHx may cause the complete collapse of the structure only when heated above 420 degrees, indicating its high thermal stability.

[0040] X-ray photoelectron spectroscopy analysis was used to determine the valence states of CdCoBTCHx, as Figure 5 shown, Figure 5 where a is the full spectrum of CdCoBTCHx, and b is the high-resolution spectrogram.

[0041] Figure 5 a confirmed the presence of Co, Cd, N, C, and O in CdCoBTCHx; from Figure 5 b, it can be seen that the Co 2p3 / 2 peak is located at 780.48 eV, accompanied by satellite peaks at 784.98 and 788.48 eV, the Co2p1 / 2 peak is located at 796.28 eV, and the corresponding satellite peaks are at 800.98 and 803.88 eV. These binding energy characteristics indicate the oxidation states of Co(II) and Co(III), suggesting that the cobalt in CdCoBTCHx exists in a mixed valence state.

[0042] An application of a cadmium-cobalt bimetallic organic framework for the recognition of sulfur-containing amino acids.

[0043] 5 mg of CdCoBTCHx was respectively immersed in aqueous solutions (1.0 mM) of 20 common amino acids. The results showed that only the solutions of cysteine (Cys) and methionine (Met) showed a significant color change from colorless to yellow, while no obvious changes were observed for other amino acids.

[0044] CdCoBTCHx was respectively added to 0.001 mol / L of L-cysteine and L-methionine, and ultraviolet-visible absorption spectroscopy analysis was carried out. Figure 6 In a and b are the ultraviolet-visible absorption spectra change diagrams after adding CdCoBTCHx to L-cysteine and L-methionine respectively. The analysis shows that after adding CdCoBTCHx, new absorption peaks rapidly appear in the solutions of cysteine and methionine in the range of 260 - 375 nm, and the absorbance gradually increases over time, indicating an obvious electron transfer between CdCoBTCHx and these two amino acids. These preliminary results indicate that CdCoBTCHx shows high selectivity for sulfur-containing amino acids, and this phenomenon may be closely related to the role of its mixed valence metal sites.

[0045] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only the specific implementation manners. Obviously, many modifications and changes can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principle and practical application of the present invention, so that those skilled in the art in the relevant technical field can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A method for preparing a novel cadmium-cobalt bimetallic organic framework, characterized in that: The following steps are involved: S1, Synthesis of Cd-Co bimetallic organic framework; Cd(NO3)2·4H2O, Co(NO3)2·6H2O, Hx, and H3BTC were placed in a DMF solvent at a ratio of 2:1:2:1, the pH was adjusted with HNO3, and the mixture was sealed in a polytetrafluoroethylene autoclave and heated at a constant temperature, then cooled to room temperature, filtered and washed to obtain light purple crystals of CdCoBTCHx; Wherein Hx is 6-hydroxypurine; H3BTC is 1,3,5-benzenetricarboxylic acid; DMF solvent is N,N-dimethylformamide solvent; CdCoBTCHx is cadmium cobalt bimetallic organic framework; S2, Property analysis of CdCoBTCHx crystals.

2. The method for preparing a novel cadmium-cobalt bimetallic organic framework according to claim 1, characterized in that: In the step S1, the concentration of HNO3 is 1 mol / L; the temperature of the constant temperature heating is 140°C and the time is 72h; after the constant temperature heating, the temperature of the polytetrafluoroethylene high-pressure reactor decreases at a rate of 5°C / h until it is cooled to room temperature.

3. The method for preparing a novel cadmium-cobalt bimetallic organic framework according to claim 1, characterized in that: In the step S2, the property analysis of the crystal includes Fourier transform infrared spectrometer analysis, single crystal X-ray diffraction analysis, X-ray powder diffractometer analysis, thermogravimetric analysis and X-ray photoelectron spectroscopy analysis.

4. The method for preparing a novel cadmium-cobalt bimetallic organic framework according to claim 3, characterized in that: The Fourier transform infrared spectrometer analysis is used to determine whether CdCoBTCHx crystals are synthesized.

5. The method for preparing a novel cadmium-cobalt bimetallic organic framework according to claim 4, characterized in that: The single crystal X-ray diffraction analysis is used to determine the single crystal structure of CdCoBTCHx.

6. The method for preparing a novel cadmium-cobalt bimetallic organic framework according to claim 4, characterized in that: The X-ray powder diffractometer analysis was used to determine the purity of CdCoBTCHx.

7. The method for preparing a novel cadmium-cobalt bimetallic organic framework according to claim 4, characterized in that: The TGA analysis was used to determine the thermal stability of CdCoBTCHx.

8. The method for preparing a novel cadmium-cobalt bimetallic organic framework according to claim 4, characterized in that: The X-ray photoelectron spectroscopy analysis is used to determine the valence state of CdCoBTCHx.

9. The use of a cadmium-cobalt bimetallic organic framework prepared by the method for preparing a novel cadmium-cobalt bimetallic organic framework according to any one of claims 1 to 8, characterized in that: It is used to identify sulfur-containing amino acids.

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