A cobalt transition metal coordination polymer and its preparation method and application

Abstract

The present invention discloses a cobalt transition metal coordination polymer and its preparation method and application, belonging to the technical field of metal organic complex material photocatalyst. The chemical formula of the cobalt transition metal coordination polymer is: [Co(L)(2,2-biby)·2H2O] n , wherein L is 2-(3-carboxyphenyl)-6-carboxybenzimidazole; 2,2-biby is 2,2'-bipyridine; n represents the degree of polymerization, which is a positive integer; and the cobalt transition metal coordination polymer belongs to the orthorhombic system and the P212121 space group. The present invention adopts the above-mentioned cobalt transition metal coordination polymer and its preparation method and application. The cobalt transition metal coordination polymer can be used as a photocatalyst, has good photocatalytic performance, and can be used as a potential photocatalyst to catalyze the degradation of organic pollutants in water.

Description

Technical Field

[0001] The present invention relates to the technical field of metal organic complex material photocatalysts, and in particular to a cobalt transition metal coordination polymer and a preparation method and application thereof. Background Art

[0002] With the rapid development of industry worldwide, the large amount of high-concentration dye wastewater discharged from industries such as pharmaceuticals and printing that does not meet standards has become one of the main sources of water pollution. Due to the relatively stable structure of dyes and the continuous increase in emissions, the treatment of dye wastewater has always been a huge challenge facing mankind. Currently, technologies including adsorption, separation, chemical oxidation, flocculation, and photocatalytic degradation are used to effectively remove dyes from wastewater, but they have disadvantages such as complex and tedious pre-treatment and high costs. As an emerging technology that has developed rapidly in recent years, photocatalytic degradation has received widespread attention worldwide in the removal of pollutants from wastewater because it can utilize sustainable and inexhaustible solar energy and can promote reactions under mild conditions. Semiconductor photocatalysts can be directly driven by light and are considered to be an ideal technology for treating environmental pollution.

[0003] Metal-organic complexes (CPs) have significant advantages, including large surface area, high stability, and easy modification of structure and properties. They have potential applications in various fields, including heterogeneous catalysis, gas storage and separation, and sensing. Recent studies have shown that certain CPs exhibit excellent semiconductor properties under ultraviolet or visible light irradiation. Compared with traditional inorganic semiconductors, CPs possess the following significant advantages: open metal active sites, unsaturated metal coordination centers, and tunable organic linker photoelectric properties. This suggests that CPs can be used as photocatalysts for the photocatalytic degradation of dye wastewater. Summary of the Invention

[0004] The present invention aims to provide a cobalt transition metal coordination polymer and its preparation method and application. The cobalt transition metal coordination polymer can be used as a photocatalyst, has good photocatalytic performance, and can be used as a potential photocatalyst to catalytically degrade organic pollutants in water.

[0005] To achieve the above object, the present invention provides a cobalt transition metal coordination polymer, the chemical formula of which is: [Co(L)(2,2-biby)·2H2O] n ;

[0006] Wherein, L is 2-(3-carboxyphenyl)-6-carboxybenzimidazole; 2,2-biby is 2,2'-bipyridine; n represents the degree of polymerization, which is a positive integer; and the cobalt transition metal coordination polymer belongs to the orthorhombic crystal system and the P212121 space group.

[0007] Preferably, the basic structural unit of the cobalt transition metal coordination polymer includes a metal Co 2+ , 1 coordinated 2-(3-carboxyphenyl)-6-carboxybenzimidazole, 1 coordinated 2,2'-bipyridine, and 2 coordinated water molecules; 2-(3-carboxyphenyl)-6-carboxybenzimidazole adopts a monodentate coordination mode with the metal Co through the carboxyl groups at both ends 2+ Coordination, 2,2'-bipyridine and metal Co 2+ The water molecules adopt a monodentate coordination mode to coordinate with the metal Co 2+ coordination.

[0008] Preferably, 1 metal Co 2+ Denoted as Co1, it forms a six-coordinated distorted octahedral configuration with the two coordinated oxygen atoms O2 and O3A of two 2-(3-carboxyphenyl)-6-carboxybenzimidazoles, the two coordinated nitrogen atoms N1 and N2 of one 2,2'-bipyridine, and the two coordinated water molecules O1W and O2W; O3A, O2, N1 and N2 occupy the four equatorial vertices of the distorted octahedral configuration, and O1W and O2W occupy the two vertex positions of the distorted octahedral configuration; the bond length of Co-O in the distorted octahedral configuration is The bond length of Co-N is The bond angle of O-Co-O is 85.25(9)~171.61(10)°, and the bond angle of O-Co-N is 90.36(10)~173.28(10)°.

[0009] Preferably, the adjacent metal Co 2+ By connecting with 2-(3-carboxyphenyl)-6-carboxybenzimidazole ligands, a 1D chain structure is formed, and the 1D chain structure is expanded into a three-dimensional network structure through weak interaction forces.

[0010] Preferably, the weak interaction force is one or more of π-π stacking, OH...O hydrogen bonding, OH...N hydrogen bonding and CH...O hydrogen bonding.

[0011] The present invention also provides a method for preparing a cobalt transition metal coordination polymer, which is characterized by comprising the following steps:

[0012] S1. Dissolve 2-(3-carboxyphenyl)-6-carboxybenzimidazole, 2,2'-bipyridine and Co(NO3)2·4H2O in deionized water and acetonitrile, and stir in a sealed container at room temperature.

[0013] S2. Add NaOH to adjust pH to 5-7 and continue stirring for 25-35 minutes;

[0014] S3, transferring the obtained suspension to a polytetrafluoroethylene reactor, covering it with an inner cover and placing it in a high-pressure stainless steel reactor, heating the high-pressure reactor in a programmable temperature-controlled oven and keeping it warm for incubation;

[0015] S4, the reaction solution was heated at 3-7℃·h -1 The cobalt transition metal coordination polymer is obtained by cooling the mixture to room temperature at a rate of

[0016] Preferably, the molar ratio of 2-(3-carboxyphenyl)-6-carboxybenzimidazole, 2,2'-bipyridine and Co(NO3)2·4H2O in S1 is 1:0.5:1-1:3:4, and the sealed stirring time is 25-35 min.

[0017] Preferably, the high-pressure reactor in S3 is heated to 100-140° C. and the heat preservation and incubation time is 36-72 hours.

[0018] The present invention also provides an application of a cobalt transition metal coordination polymer, wherein the cobalt transition metal coordination polymer described above is applied to photocatalytic degradation of organic pollutants in water.

[0019] Therefore, the present invention adopts the above-mentioned cobalt transition metal coordination polymer and its preparation method and application, which has the following beneficial effects:

[0020] 1. The cobalt transition metal coordination polymer prepared by the present invention can maintain stability within 200°C.

[0021] 2. The cobalt transition metal coordination polymer prepared by the present invention can be used as a photocatalyst to degrade organic pollutants in water. Under ultraviolet light irradiation, the photocatalytic degradation rate of erythrosine B is 93.5% within 20 minutes, the photocatalytic degradation rate of amaranth is 38.1%, and the photocatalytic degradation rate of naphthol green is 36.1%.

[0022] 3. The cobalt transition metal coordination polymer photocatalyst prepared by the present invention has a high reuse rate for degrading organic pollutants.

[0023] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a diagram of the coordination environment of a cobalt complex of a cobalt transition metal coordination polymer and its preparation method and application examples of the present invention;

[0025] Figure 2 It is a cobalt transition metal coordination polymer and its preparation method and application embodiment of the present invention, and the cobalt complex 1D chain structure;

[0026] Figure 3This is a thermogravimetric analysis diagram of a cobalt transition metal coordination polymer and its preparation method and the cobalt complex of Application Example 1 of the present invention;

[0027] Figure 4 This is an X-ray powder diffraction pattern obtained through experimental testing and computer simulation of a cobalt transition metal coordination polymer and its preparation method and application example 1 of the present invention;

[0028] Figure 5 This is an infrared spectrum of a cobalt transition metal coordination polymer and its preparation method and application example 1 of the present invention;

[0029] Figure 6 This is a cobalt transition metal coordination polymer of the present invention, its preparation method and application example 1, and an ultraviolet spectrum of the photocatalytic degradation of naphthol green;

[0030] Figure 7 This is a UV spectrum of a cobalt transition metal coordination polymer and its preparation method and application example 1 of the present invention on the photocatalytic degradation of amaranth;

[0031] Figure 8 This is a UV spectrum of a cobalt transition metal coordination polymer and its preparation method and application example 1 of the present invention for photocatalytic degradation of erythrosine B;

[0032] Figure 9 This is a bar graph showing the catalytic degradation of different organic dyes (erythrosine B, amaranth, and naphthol green) by a cobalt transition metal coordination polymer and its preparation method and application example 1 of the present invention;

[0033] Figure 10 This is a cobalt transition metal coordination polymer of the present invention, its preparation method and application Example 1 tests the catalytic mechanism (TBA, BQ and AO) of erythrosine B.

[0034] Figure 11 This is a comparison chart of the cobalt transition metal coordination polymer and its preparation method of the present invention and Application Example 1 on the catalytic degradation of erythrosine B under different capture agents (TBA, BQ and AO);

[0035] Figure 12 This is a diagram showing the kinetic test results of catalytic degradation of erythrosine B by different capture agents (TBA, BQ and AO) in Example 1 of a cobalt transition metal coordination polymer and its preparation method and application according to the present invention;

[0036] Figure 13 This is a graph showing the test results of the repeated use of a cobalt transition metal coordination polymer and its preparation method and application example 1 of the present invention for catalytic degradation of erythrosine B. DETAILED DESCRIPTION

[0037] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0038] Unless otherwise defined, technical or scientific terms used in the present invention shall have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0039] Example

[0040] The present invention provides a cobalt transition metal coordination polymer, the chemical formula of the cobalt transition metal coordination polymer is: [Co(L)(2,2-biby)·2H2O] n ; Wherein, L is 2-(3-carboxyphenyl)-6-carboxybenzimidazole; 2,2-biby is 2,2'-bipyridine; n represents the degree of polymerization, which is a positive integer; the cobalt transition metal coordination polymer belongs to the orthorhombic crystal system and the P212121 space group.

[0041] The basic structural unit of cobalt transition metal coordination polymers consists of a metal Co 2+ , 1 coordinated 2-(3-carboxyphenyl)-6-carboxybenzimidazole, 1 coordinated 2,2'-bipyridine, and 2 coordinated water molecules; 2-(3-carboxyphenyl)-6-carboxybenzimidazole adopts a monodentate coordination mode with the metal Co through the carboxyl groups at both ends 2+ Coordination, 2,2'-bipyridine and metal Co 2+ The water molecules adopt a monodentate coordination mode to coordinate with the metal Co 2+ coordination.

[0042] 1 metal Co 2+ Denoted as Co1, it forms a six-coordinated distorted octahedral configuration with the two coordinated oxygen atoms O2 and O3A of two 2-(3-carboxyphenyl)-6-carboxybenzimidazoles, the two coordinated nitrogen atoms N1 and N2 of one 2,2'-bipyridine, and the two coordinated water molecules O1W and O2W; O3A, O2, N1 and N2 occupy the four equatorial vertices of the distorted octahedral configuration, and O1W and O2W occupy the two vertex positions of the distorted octahedral configuration; the bond length of Co-O in the distorted octahedral configuration is The bond length of Co-N is The bond angle of O-Co-O is 85.25(9)~171.61(10)°, and the bond angle of O-Co-N is 90.36(10)~173.28(10)°.

[0043] Adjacent metal Co 2+By connecting with 2-(3-carboxyphenyl)-6-carboxybenzimidazole ligands to form a 1D chain structure, the 1D chain structure is expanded into a three-dimensional network structure through weak interaction forces. The weak interaction forces are one or more of π-π stacking, OH...O hydrogen bonds, OH...N hydrogen bonds and CH...O hydrogen bonds.

[0044] Three-dimensional network structures provide greater mechanical strength and stability. Compared to single 1D chain structures, they are more resistant to external forces. Furthermore, they enable the material to maintain its structural integrity at high temperatures, making it less susceptible to decomposition or phase transitions. Three-dimensional network structures typically have a high specific surface area, which enables the material to exhibit excellent performance in catalysis, adsorption, and gas storage. A larger specific surface area means more active sites, thereby improving the material's reaction efficiency and adsorption capacity.

[0045] The three-dimensional network structure can stabilize the coordination environment through weak interactions, reducing the impact of external conditions on the material, which helps improve the material's stability in various chemical environments. The three-dimensional network structure can provide more active sites, and these active sites can be controlled by weak interactions. This leads to higher activity and selectivity in catalytic reactions.

[0046] The present invention also provides a method for preparing a cobalt transition metal coordination polymer, which is characterized by comprising the following steps:

[0047] S1. Dissolve 2-(3-carboxyphenyl)-6-carboxybenzimidazole, 2,2'-bipyridine, and Co(NO3)2·4H2O in deionized water and acetonitrile at a molar ratio of 1:1.5:2 and stir in a sealed container at room temperature for 25-35 minutes. The use of 2-(3-carboxyphenyl)-6-carboxybenzimidazole, 2,2'-bipyridine, and Co(NO3)2·4H2O to prepare cobalt transition metal coordination polymers not only provides structural diversity and controllability but also enhances the stability, porosity, and specific surface area of ​​the materials.

[0048] S2. Add NaOH to adjust pH to 5-7 and continue stirring for 25-35 minutes;

[0049] S3. Transfer the obtained suspension to a polytetrafluoroethylene reactor, cover it with an inner cover and place it in a high-pressure stainless steel reactor. Heat the high-pressure reactor to 100-140° C. in a programmable temperature-controlled oven and incubate at this temperature for 36-72 hours.

[0050] S4, the reaction solution was heated at 3-7℃·h -1 The cobalt transition metal coordination polymer is obtained by cooling the mixture to room temperature at a rate of

[0051] Example 1

[0052] A cobalt transition metal coordination polymer having the chemical formula [Co(L)(2,2-biby)·2H2O] n , obtained by the following steps:

[0053] 0.01 mol of 2-(3-carboxyphenyl)-6-carboxybenzimidazole L, 0.015 mol of 2,2'-bipyridine, 0.02 mol of Co(NO3)2·4H2O were mixed evenly with 5 mL of deionized water and 5 mL of acetonitrile, sealed and stirred at room temperature for 30 minutes, the pH was adjusted to 5 with 0.5 mol / L NaOH, and stirred for another 30 minutes. The resulting suspension was transferred to a polytetrafluoroethylene reactor (25 mL), covered with an inner lid and placed in a high-pressure stainless steel reactor. The high-pressure reactor was heated to 140°C in a programmable temperature-controlled oven and kept warm for 72 hours. The reaction solution was then heated at 5°C·h -1 The mixture was cooled to room temperature at a rate of 100 to obtain a cobalt transition metal coordination polymer.

[0054] Example 2

[0055] A cobalt transition metal coordination polymer having the chemical formula [Co(L)(2,2-biby)·2H2O] n , obtained by the following steps:

[0056] 0.02 mol of 2-(3-carboxyphenyl)-6-carboxybenzimidazole L, 0.03 mol of 2,2'-bipyridine, 0.04 mol of Co(NO3)2·4H2O were mixed evenly with 10 mL of deionized water and 10 mL of acetonitrile, sealed and stirred at room temperature for 30 min, adjusted to pH 6 with 0.5 mol / L NaOH, and stirred for another 30 min. The resulting suspension was transferred to a polytetrafluoroethylene reactor (25 mL), covered with an inner lid and placed in a high-pressure stainless steel reactor. The high-pressure reactor was heated to 140°C in a programmable temperature-controlled oven and kept warm for 72 hours. The reaction solution was then heated at 5°C·h -1 The mixture was cooled to room temperature at a rate of 100 to obtain a cobalt transition metal coordination polymer.

[0057] Example 3

[0058] A cobalt transition metal coordination polymer having the chemical formula [Co(L)(2,2-biby)·2H2O] n , obtained by the following steps:

[0059] 0.2 mol of 2-(3-carboxyphenyl)-6-carboxybenzimidazole L, 0.3 mol of 2,2-biby, 0.4 mol of Co(NO3)2·4H2O were mixed evenly with 50 mL of deionized water and 50 mL of acetonitrile, sealed and stirred at room temperature for 30 min, adjusted to pH 7 with 0.5 mol / L NaOH, and stirred for another 30 min. The resulting suspension was transferred to a polytetrafluoroethylene reactor (150 mL), covered with an inner lid and placed in a high-pressure stainless steel reactor. The high-pressure reactor was heated to 140°C in a programmable temperature-controlled oven and kept warm for 72 hours. The reaction solution was then heated at 5°C·h -1 The mixture was cooled to room temperature at a rate of 100 to obtain a cobalt transition metal coordination polymer.

[0060] The cobalt transition metal coordination polymer prepared in Example 1 was characterized to obtain the crystallographic parameters shown in Table 1, and the partial bond length and bond angle data shown in Table 2. The elemental analysis of the complex yielded theoretical values ​​of C: 56.45, H: 3.76, and N: 10.54 (derived from CCDC: 2384213), and experimental values ​​of C: 55.75, H: 3.43, and N: 10.15.

[0061] Table 1 Crystallographic parameters of the complexes

[0062]

[0063] *R=∑(F o –F c ) / ∑(F o ); **wR2={∑[w(F o 2 –F c 2 ) 2 ] / ∑(F o 2 ) 2} 1 / 2 .

[0064] Table 2 Some bond lengths of complexes and bond angle (°)

[0065]

[0066] Symmetric code: A:x,1+y,z.

[0067] The cobalt metal organic coordination polymer prepared in Example 1 was tested (the following experiments are all based on the cobalt metal organic coordination polymer in Example 1). The asymmetric environment diagram is shown in FIG. Figure 1 As shown by Figure 1 It can be seen that the cobalt metal organic coordination polymer has the advantages of high coordination number, multi-center coordination, asymmetric environment and multifunctionality. Its 1D chain structure is as follows Figure 2 As shown in the figure, it can be seen that the 1D chain structure of the cobalt metal organic coordination polymer has the advantages of high stability, good conductivity, high specific surface area, adjustable pore structure and easy synthesis.

[0068] The cobalt transition metal coordination polymer prepared in Example 1 was subjected to thermogravimetric analysis. Figure 3 The thermogravimetric curve of the polymer is shown in Figure 2: Thermogravimetric analysis of a cobalt transition metal coordination polymer sample under nitrogen conditions reveals a slight weight loss between 201.6 and 251.9°C, attributed to the weight loss of coordinated water molecules. When the temperature rises above 342.6°C, the organic ligands in the cobalt transition metal coordination polymer begin to decompose, causing the overall molecular framework to collapse and ultimately decompose into metal oxides.

[0069] Figure 4 The experimental and computer-simulated X-ray powder diffraction patterns of the cobalt transition metal coordination polymer prepared in Example 1 were compared. The theoretical simulated powder XRD pattern of the sample and the experimental data test pattern showed that the peak shapes and positions of the theoretical data and experimental data were consistent within the 2θ range of 5-50°. Furthermore, the peaks were consistent with the elemental analysis results of the sample, indicating that the synthesized complex sample was phase-pure.

[0070] Figure 5 This is the infrared spectrum test chart of the cobalt transition metal coordination polymer prepared in Example 1. -1 The broad absorption peak at 1601 cm is the absorption peak of OH in the coordinated water in the coordination polymer. -1 The absorption peak at 1562 cm is the C=O double bond stretching vibration of the carboxylate in 2-(3-carboxyphenyl)-6-carboxybenzimidazole. -1 The absorption peak that appears near is the stretching vibration of the C=N double bond on the auxiliary 2,2'-bipyridine ring, 1386cm -1 The peaks at 796 and 718 cm are for the bending vibration of COC, and the peaks for the out-of-plane bending vibration of CH are located at 796 and 718 cm, respectively. -1 nearby.

[0071] The photocatalytic properties of the cobalt transition metal coordination polymer prepared in Example 1 were examined to determine its potential as a photocatalyst for the degradation of organic pollutants in water. The photocatalytic degradation of organic dyes was performed as follows: 25 mg of the sample was finely ground and added to an aqueous solution of Naphthol Green B, Amaranth, or Erythrosine B, stirring until adsorption-desorption equilibrium was achieved. The mixed solution was then stirred under a UV Hg lamp, with 5 mL of the solution removed every 5 minutes.

[0072] The aqueous solutions of organic dyes naphthol green B, amaranth or algae red B were selected to explore the photocatalytic activity of cobalt transition metal coordination polymer samples. Figure 6 、 Figure 7 and Figure 8 These are the photocatalytic UV spectra of cobalt transition coordination polymer on aqueous solutions of naphthol green B, amaranth and algae red B. Under ultraviolet light, the UV absorption peaks of these three dyes were significantly weakened with time. The results show that the catalyst has strong photocatalytic degradation ability for naphthol green B, amaranth and algae red B, especially algae red B.

[0073] like Figure 9 As shown, according to the solution concentration C / C0 calculation (C is the absorption peak intensity at a certain time, C0 is the absorption peak intensity of the initial concentration), the photocatalytic degradation rate of cobalt transition metal coordination polymer for erythrocyanine B is 93.5% (the self-degradation rate of erythrocyanine B is 45.1%); the photocatalytic degradation rate of cobalt transition metal coordination polymer for amaranth red is 38.1%; the photocatalytic degradation rate of cobalt transition metal coordination polymer for naphthol green is 36.1%; the results show that cobalt transition metal coordination polymer has good photocatalytic degradation effect on the three dyes, especially for erythrocyanine B.

[0074] The catalytic mechanism of cobalt transition metal coordination polymer in algae red B was also tested. Tertiary butyl alcohol (TBA), a scavenger of ·OH, ammonium oxalate (AO), and ·O2 were added to the photocatalytic reaction system. - The capture agent benzoquinone (BQ)

[0075] like Figure 10 and Figure 11 As shown in the figure, according to the solution concentration C / C0, the degradation rate of erythrocyanine B is 93.5% without the addition of three capture agents, 87.5% with the addition of TBA, 90.1% with the addition of AO, and 49.3% with the addition of BQ. By comparing the data in the presence of different capture agents, it is concluded that the photodegradation of erythrocyanine B is caused by·O2 - Free radical dominated.

[0076] like Figure 12 As shown, the kinetic study test shows that with Ln(C0 / C) as the ordinate and the reaction time t as the abscissa, the linear coefficient of the function graph obtained is 0.9962, which indicates that the degradation reaction of cobalt transition metal coordination polymer to algae red B conforms to the kinetic first-order reaction characteristics, and the rate constant of the degradation reaction within 20 minutes is 0.1303min -1 .

[0077] The catalyst reusability test was carried out on the cobalt transition metal coordination polymer, such as Figure 13After the degradation reaction, the cobalt transition metal coordination polymer was centrifuged, washed, and dried before being used in the next erythrocyanine B degradation reaction. The experimental results showed that after four cycles of use, the catalytic activity of the cobalt transition metal coordination polymer had not significantly degraded, indicating the high reusability of the cobalt transition metal coordination polymer.

[0078] In summary, the cobalt metal organic complex prepared by the present invention achieved a photocatalytic degradation rate of 93.5% for erythrocyanine B within 20 minutes (the self-degradation rate of blank erythrocyanine B was 45.1%); a photocatalytic degradation rate of 38.1% for amaranth; and a photocatalytic degradation rate of 36.1% for naphthol green. A comparison of the photocatalytic degradation of organic dyes by cobalt metal organic complexes revealed that the cobalt metal organic complex catalyst exhibited the best photocatalytic degradation performance for erythrocyanine B, suggesting its potential as a photocatalyst for the degradation of organic pollutants in water.

[0079] Therefore, the present invention adopts the above-mentioned cobalt transition metal coordination polymer and its preparation method and application. The cobalt transition metal coordination polymer has good photocatalytic performance and can be used as a potential photocatalyst to catalyze the degradation of organic pollutants in water.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A cobalt transition metal coordination polymer, characterized in that: The chemical formula of cobalt transition metal coordination polymer is: [Co(L)(2,2-biby)·2H2O] n ; Wherein, L is 2-(3-carboxyphenyl)-6-carboxybenzimidazole; 2,2-biby is 2,2'-bipyridine; n represents the degree of polymerization, which is a positive integer; the cobalt transition metal coordination polymer belongs to the orthorhombic system and the P212121 space group; The basic structural unit of cobalt transition metal coordination polymers consists of a metal Co 2+ , 1 coordinated 2-(3-carboxyphenyl)-6-carboxybenzimidazole, 1 coordinated 2,2'-bipyridine, and 2 coordinated water molecules; 2-(3-carboxyphenyl)-6-carboxybenzimidazole adopts a monodentate coordination mode with the metal Co through the carboxyl groups at both ends 2+ Coordination, 2,2'-bipyridine and metal Co 2+ The water molecules adopt a monodentate coordination mode to coordinate with the metal Co 2+ coordination; 1 metal Co 2+ It is denoted as Co1, and forms a hexacoordinated distorted octahedral configuration with the two coordinated oxygen atoms O2 and O3A of two 2-(3-carboxyphenyl)-6-carboxybenzimidazoles, the two coordinated nitrogen atoms N1 and N2 of one 2,2'-bipyridine, and the two coordinated water molecules O1W and O2W. O3A, O2, N1, and N2 occupy the four equatorial vertices of the distorted octahedral configuration, and O1W and O2W occupy the two vertex positions of the distorted octahedral configuration. The bond length of Co-O in the distorted octahedral configuration is 2.088(2)~ The bond length of Co-N is The bond angles of O-Co-O are 85.25(9) to 171.61(10)°, and the bond angles of O-Co-N are 90.36(10) to 173.28(10)°; Adjacent metal Co 2+ By connecting with 2-(3-carboxyphenyl)-6-carboxybenzimidazole ligands, a 1D chain structure is formed, and the 1D chain structure is expanded into a three-dimensional network structure through weak interaction forces.

2. The cobalt transition metal coordination polymer according to claim 1, characterized in that: The weak interaction force is one or more of π-π stacking, OH…O hydrogen bond, OH…N hydrogen bond and CH…O hydrogen bond.

3. A method for preparing the cobalt transition metal coordination polymer according to claim 1, characterized in that: The following steps are involved: S1. Dissolve 2-(3-carboxyphenyl)-6-carboxybenzimidazole, 2,2'-bipyridine and Co(NO3)2·4H2O in deionized water and acetonitrile, and stir in a sealed container at room temperature. S2. Add NaOH to adjust pH to 5-7 and continue stirring for 25-35 minutes; S3, transferring the obtained suspension to a polytetrafluoroethylene reactor, covering it with an inner cover and placing it in a high-pressure stainless steel reactor, heating the high-pressure reactor in a programmable temperature-controlled oven and keeping it warm for incubation; S4. Cooling the reaction solution to room temperature at a rate of 3-7°C / h to obtain a cobalt transition metal coordination polymer.

4. The method for preparing a cobalt transition metal coordination polymer according to claim 3, wherein: The molar ratio of 2-(3-carboxyphenyl)-6-carboxybenzimidazole, 2,2'-bipyridine and Co(NO3)2·4H2O in S1 is 1:0.5:1-1:3:4, and the sealed stirring time is 25-35 minutes.

5. The method for preparing a cobalt transition metal coordination polymer according to claim 3, wherein: The high-pressure reactor in S3 is heated to 100-140°C and the heat preservation and incubation time is 36-72 hours.

6. An application of a cobalt transition metal coordination polymer, characterized in that: The cobalt transition metal coordination polymer according to claim 1 is used for photocatalytic degradation of organic pollutants in water.

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