Hollow fiber-based cobalt coordination polymers and composites thereof, methods of preparation, and applications

Abstract

The application discloses a kind of hollow fiber base cobalt coordination polymer (Co-CP) and its composite material, preparation method and application, specifically related to the structure regulation of this material and the application of its composite material.The Co-CP is synthesized, which is mixed with polyacrylonitrile (PAN) to prepare outer layer spinning solution, with paraffin oil as inner layer spinning solution, to obtain fiber base Co-CP-1 with core-shell structure by coaxial electrospinning;After core removal treatment with petroleum ether, fiber base Co-CP-2 with hollow structure is prepared.Subsequently, using in-situ growth technology, indium sulfide is constructed in-situ on fiber base Co-CP-2 with hollow structure to obtain hollow fiber base In2S3@Co-CP-2 composite material.Due to the unique hollow structure and heterojunction interface of In2S3@Co-CP-2, it has high charge separation capacity and excellent chemical stability, realizing efficient application in photocatalytic synthesis of hydrogen peroxide.

Description

Technical Field

[0001] This invention belongs to the field of inorganic-organic hybrid materials technology, specifically relating to the preparation method and application of cobalt coordination polymers (Co-CP) and their composite materials. Technical Background

[0002] In recent years, with the development of clean energy and the continuous advancement of the environmental governance industry, photoresponsive coordination polymers (CPs) have attracted widespread attention and are considered highly promising photocatalytic materials. Due to the tunable and controllable fabrication of CPs, they possess a large specific surface area and abundant active sites, enabling the generation of photogenerated charge carriers during photocatalysis, demonstrating significant advantages in the field of heterogeneous catalysis. However, traditional bulk or powdered CPs exhibit significant grain agglomeration in their microstructure. Disordered particle stacking easily leads to internal pore collapse and blockage, causing structural collapse and deactivation of unsaturated coordination active sites during photocatalysis. This hinders the interfacial migration and transport of photogenerated electron-hole pairs, thus affecting light energy utilization and catalytic reaction efficiency. Simultaneously, CPs have weak absorption of visible light, affecting their charge transport efficiency and photoelectric conversion performance under visible light.

[0003] To achieve highly efficient photocatalysis by photocatalysts (CPs) under visible light, CPs are combined with inorganic semiconductors to construct CP-based composite materials. This leverages the synergistic effect of both materials, improving photocorrosion of the inorganic semiconductors and the rapid closing of photogenerated electron-hole pairs. Furthermore, it modulates the light absorption range of CPs, enabling efficient photocatalysis under visible light. Simultaneously, to construct uniformly dispersed CPs composite materials, CPs are combined with electrospinning technology. By controlling the spinning process, uniformly and continuously dispersed CPs-based fiber composite materials are prepared, providing a high inorganic semiconductor loading platform and facilitating the synthesis of excellent photocatalytic composite materials. Currently, preparing catalysts (CPs) into fiber-based materials has become an effective strategy to improve their application performance. However, existing studies mostly use solid electrospun fibers, which are prone to encapsulation and aggregation of active components, resulting in few effective reaction sites. Furthermore, it is difficult to construct highly efficient conductive interfaces and heterogeneous structures, leading to severe recombination of photogenerated carriers and poor mass transfer, light utilization efficiency, and cycle stability (ACS Omega, 2026, 5, 6954~6985; Journal of Materials Science & Technology, 2023, 150, 114–123). Solid fiber supports are also prone to catalyst shedding and aggregation, preventing internal active materials from contacting reactants and resulting in low photocatalytic efficiency. They are also susceptible to membrane blockage, matrix photoaging, high electron-hole recombination rates, and the potential for secondary pollution from powdered catalysts, limiting their practical application (Catalysts, 2023, 4, 758; Nature Reviews Methods Primers, 2024, 4, 1).

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] To address the challenges of existing fiber-supported systems that primarily utilize solid fiber carriers, resulting in CPs only adhering to the fiber surface, limited loading capacity, lack of internal fluid channels, and difficulty in synergistically leveraging the structural advantages of both the carrier and catalytic material, this invention provides a method for preparing Co-CP, hollow fiber-based Co-CP, and their indium sulfide composites, as well as the application of this composite material in the photocatalytic preparation of hydrogen peroxide. This invention proposes constructing a hollow fiber-based CP composite material and, through electrospinning technology and in-situ synthesis strategies, modulating its photocatalytic performance, thus solving the problems of CPs, inorganic semiconductors, and solid fibers affecting photocatalytic performance.

[0006] This invention constructs CPs into a hollow fiber structure, which not only further expands the specific surface area and exposes more active sites, but also accelerates charge migration and improves light absorption efficiency through hollow channels, while facilitating recycling and reuse. Furthermore, by combining it with inorganic semiconductors to construct a heterojunction, the material's band structure can be effectively optimized, the light absorption range can be broadened, and charge recombination can be suppressed, providing a new approach to improving the performance of coordination polymer photocatalytic materials.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] This invention selects (3,5-dicarboxyphenyl chloroacetamide)(H2ctpa) as an organic ligand, and performs solvothermal self-assembly with o-phenanthroline (Phen) and cobalt ions to synthesize crystalline Co-CP[Co(ctpa)(Phen)]. n The obtained Co-CP was then mixed with PAN polymer to prepare a spinning precursor solution, and a core-shell structured fiber precursor Co-CP-1 was prepared by coaxial electrospinning. Subsequently, after soaking in petroleum ether combined with ultrasonic-assisted core removal, washing with ethanol, and drying, a hollow fiber-based cobalt coordination polymer Co-CP-2 with regular morphology and stable structure was obtained. Finally, using hollow fiber Co-CP-2 as a carrier, indium chloride tetrahydrate and thioacetamide were introduced in situ to construct a heterojunction structure, ultimately obtaining an In2S3@Co-CP-2 composite catalytic material with excellent photocatalytic performance. The specific steps include:

[0009] (1) Preparation of cobalt coordination polymer Co-CP;

[0010] (2) Add the Co-CP and PAN obtained in step (1) into N,N-dimethylformamide DMF, heat and stir until the raw materials are completely dissolved and evenly dispersed to form a uniform and stable spinning solution;

[0011] (3) Using a coaxial electrospinning device, the spinning solution prepared in step (2) is used as the outer layer fluid and paraffin oil is used as the inner layer fluid. The flow rate of the outer layer and the inner layer solution and the spinning voltage are controlled to carry out spinning. After spinning is completed, the obtained fiber membrane is placed at room temperature to air dry naturally to obtain the core-shell structure fiber precursor Co-CP-1.

[0012] (4) The core-shell structure fiber precursor Co-CP-1 was immersed in petroleum ether for core removal treatment. Ultrasonic assistance was applied to the immersion process to fully dissolve and remove the paraffin oil core layer inside the fiber. After the core removal treatment was completed, the fiber was washed with ethanol to remove residual solvent and impurities on the surface. The washed fiber was dried to obtain a hollow fiber-based cobalt coordination polymer Co-CP-2 with complete structure, regular morphology and interconnected internal channels. This hollow structure can effectively increase the specific surface area of ​​the material, optimize the transport path of substrate and oxygen, improve the utilization rate of active sites, and facilitate the recovery and reuse of catalyst.

[0013] Furthermore, the preparation method of the cobalt coordination polymer Co-CP in step (1) includes the following steps:

[0014] a. Co(OAc)2·4H2O is added to a mixed solution of deionized water (H2O), acetonitrile (CH3CN), and ethanol (EtOH), and stirred at room temperature to obtain reaction system a. The volume ratio of CH3CN, EtOH, and H2O is (4-6):(2-3):(2-3), preferably 4:2:2.

[0015] b. Add H2cpta (3,5-dicarboxyphenyl chloroacetamide) and Phen (1,10-phenanthroline) to the reaction system a in step (1) respectively, and stir to obtain reaction system b. The molar ratio of Co(OAc)2·4H2O, Phen and H2cpta is (0.04-0.08):(0.1-0.2):(0.04-0.08), preferably 0.04:0.1:0.04.

[0016] c. Place reaction system b in a transparent glass vial and react in an oven at 80-85℃ for 10-12 h, then cool to room temperature at a rate of 5-10℃ / h to obtain clustered red crystals; wash and dry successively with distilled water and acetonitrile to obtain Co-CP, with the molecular formula [Co(ctpa)(Phen)]. n , n=∞.

[0017] Furthermore, the mass fraction of Co-CP in the spinning solution is 1%-30%, which can be selected as 1%, 5%, 10%, 20%, or 30%, with 7 mL of DMF added for every 650 mg of PAN; preferably, the mass fraction of Co-CP in the spinning solution is 10%, at which ratio the spinning solution has the best filamentation properties, and the resulting fibers are uniform in thickness and have good load dispersion, which is beneficial for subsequent hollow structure formation.

[0018] Furthermore, in step (3), the inner and outer specifications of the coaxial electrospinning needle are 13 G and 18 G, the flow rates of the outer and inner solutions are 0.9-1.2 ml / h and 0.3-0.5 ml / h, respectively, the voltage is 18-20 kV, and the needle is air-dried at room temperature for 2-4 hours after spinning.

[0019] Further, in step (4), the core-shell structure fiber precursor Co-CP-1 is soaked in petroleum ether and sonicated for 2-4 h, washed with ethanol 3-5 times, and then air-dried at room temperature to obtain hollow fiber-based cobalt coordination polymer Co-CP-2.

[0020] The present invention also provides a hollow fiber-based cobalt coordination polymer Co-CP-2 prepared by the preparation method described above. The Co-CP, Co-CP-1 and hollow spun fiber Co-CP-2 prepared by the preparation method of the present invention retain their fibrous structure before and after core removal.

[0021] This invention also provides a method for preparing an indium sulfide composite hollow fiber-based cobalt coordination polymer material. The hollow fiber-based cobalt coordination polymer Co-CP-2 is added to an ethanol solution of InCl3·4H2O, followed by the addition of thioacetamide. The mixture is then sealed and reacted in an oven. After the reaction is completed, the mixture is cooled, centrifuged, and washed with distilled water to obtain the indium sulfide composite hollow fiber-based cobalt coordination polymer material In2S3@Co-CP-2.

[0022] Furthermore, the mass ratio of Co-CP-2, InCl3·4H2O, and thioacetamide is 0.05:(0.006-0.035):(0.002-0.009), preferably 0.05:0.024:0.006, the reaction temperature is 150-160℃, and the reaction time is 10-12 h.

[0023] The present invention also provides an indium sulfide composite hollow fiber-based cobalt coordination polymer material In2S3@Co-CP-2 prepared by the preparation method, wherein the indium sulfide composite hollow fiber-based cobalt coordination polymer material In2S3@Co-CP-2 maintains the hollow structure of the hollow fiber-based cobalt coordination polymer Co-CP-2.

[0024] This invention also provides the application of indium sulfide composite hollow fiber-based cobalt coordination polymer material In2S3@Co-CP-2 in the photocatalytic preparation of hydrogen peroxide. This material is a heterogeneous catalyst with excellent catalytic activity and is easy to recover. It can efficiently prepare hydrogen peroxide under visible light.

[0025] The application of the In2S3@Co-CP-2 catalytic material prepared by the above method in the photocatalytic preparation of hydrogen peroxide includes the following steps:

[0026] Purified water and benzyl alcohol were mixed as the reaction substrate, and 10 mg of In2S3@Co-CP-2 catalyst was added. The mixture was purged with oxygen for 10 min, stirred in the dark for 1 h, and then stirred under visible light for 1.5 h to complete the reaction. The highest yield of hydrogen peroxide was 70.8 mmol / g, as determined by UV-Vis spectrophotometry.

[0027] The beneficial effects of this invention are:

[0028] 1. The preparation process of this invention is mild and easy to operate. By combining solvothermal reaction with coaxial electrospinning technology, it not only effectively solves the problems of poor dispersibility and inconvenient recovery of traditional coordination polymers, but also significantly improves the utilization rate of active sites by relying on the hollow spinning structure, making the reaction mass transfer more efficient. At the same time, it is driven by visible light, practicing the concept of green energy saving. It can achieve high recovery of catalyst without complex equipment, greatly reducing production and application costs, and taking into account both environmental protection and practicality.

[0029] 2. This invention successfully prepared hollow spun fibers Co-CP-2 with complete structure and interconnected channels by precisely controlling the spinning process and core removal technology. The hollow structure can effectively expand the reaction contact area, accelerate the full combination of substrate and catalyst, and reduce the waste of active sites. Compared with traditional powdered catalysts, hollow spinning has better dispersibility and can more fully exert the catalytic effect, significantly improving reaction efficiency and product yield, and solving the technical pain points of insufficient exposure of active sites and poor mass transfer in traditional materials.

[0030] 3. The hollow spun material prepared by this invention can not only stably maintain its structural integrity, but also, through in-situ loading of indium sulfide, produce In2S3@Co-CP-2 composite hollow fiber catalytic material. Compared with the original crystalline powder Co-CP, the unique hollow fiber structure in In2S3@Co-CP-2 has interconnected internal channels and good fiber morphology dispersion, thereby further optimizing the catalytic performance, making the photocatalytic reaction more efficient, and realizing convenient recovery and reuse of the catalyst. This reduces the application cost, expands the application scenarios of hollow fiber materials, and enhances the overall practical value. It provides a better technical path and support for the photocatalytic preparation of hydrogen peroxide, and is both environmentally friendly and practical. Attached Figure Description

[0031] Figure 1 This is a structural diagram of the H2ctpa and Phen ligands used in material preparation.

[0032] Figure 2 This is a crystal unit structure diagram of the Co-CP material prepared in Example 1.

[0033] Figure 3 This is a thermogravimetric analysis diagram of the Co-CP material prepared in Example 1.

[0034] Figure 4 This is a SEM image of Co-CP-1, a core-shell structured fiber precursor with a mass fraction of 1%.

[0035] Figure 5 This is a SEM image of Co-CP-1, a core-shell structured fiber precursor with a mass fraction of 5%.

[0036] Figure 6 This is a SEM image of Co-CP-1, a core-shell structured fiber precursor with a mass fraction of 10%.

[0037] Figure 7 This is a SEM image of Co-CP-1, a core-shell structured fiber precursor with a mass fraction of 20%.

[0038] Figure 8 This is a SEM image of Co-CP-1, a core-shell structured fiber precursor with a mass fraction of 30%.

[0039] Figure 9 This is a comparison of powder XRD patterns of the Co-CP material prepared in Example 1 and the Cd-CP-2 material prepared in Example 7.

[0040] Figure 10 Yes, the SEM image of Cd-CP-2 obtained in Example 7.

[0041] Figure 11 Yes, this is a cross-sectional SEM image of Cd-CP-2 obtained in Example 7.

[0042] Figure 12 This is a SEM image of In2S3@Co-CP-2a (Co-CP-3a) with an In2S3 mass fraction of 7% in Example 8.

[0043] Figure 13 This is a SEM image of In2S3@Co-CP-2b (Co-CP-3b) with an In2S3 mass fraction of 11% in Example 9.

[0044] Figure 14 This is a SEM image of In2S3@Co-CP-2c (Co-CP-3c) with an In2S3 mass fraction of 18% in Example 10.

[0045] Figure 15 This is a SEM image of In2S3@Co-CP-2d (Co-CP-3d) with an In2S3 mass fraction of 24% in Example 11.

[0046] Figure 16 This is the UV-Vis absorption spectrum of the hydrogen peroxide standard solution and the corresponding absorbance-concentration standard curve.

[0047] Figure 17 This is a yield diagram of hydrogen peroxide produced by the reaction of the composite material In2S3@Co-CP-2c (Co-CP-3c) under different catalytic conditions in Example 12.

[0048] Figure 18 This is a yield graph of hydrogen peroxide produced by the catalytic reaction of water with the composite materials In2S3@Co-CP-2a (Co-CP-3a), In2S3@Co-CP-2b (Co-CP-3b), In2S3@Co-CP-2c (Co-CP-3c), and In2S3@Co-CP-2d (Co-CP-3d) in Example 13.

[0049] Figure 19 This is a yield graph of hydrogen peroxide produced from water using Co-CP, Co-CP-2c, and In2S3 catalysis in Example 14.

[0050] Figure 20 This is a cyclic experimental test diagram of the In2S3@Co-CP-2c (Co-CP-3c) composite catalyst.

[0051] Figure 21 This is a SEM image of the In2S3@Co-CP-2c (Co-CP-3c) composite catalyst after a cycle experiment.

[0052] Figure 22 This is a cross-sectional SEM image of the In2S3@Co-CP-2c (Co-CP-3c) composite catalyst after a cycle experiment. Detailed Implementation

[0053] The following examples further illustrate the above-described content of the present invention, but it should not be construed as limiting the scope of the subject matter of the present invention to the following examples. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention.

[0054] Example 1

[0055] Preparation of red cluster-like crystalline Co-CP materials:

[0056] (1) 9.96 mg (0.04 mmol) Co(OAc)2·4H2O was added to a mixed solution consisting of 2 ml deionized water, 4 ml acetonitrile and 2 ml ethanol. The mixture was stirred magnetically at room temperature to obtain reaction system a.

[0057] (2) Mix 10.3 mg (0.04 mmol) H2ctpa and 19.8 mg (0.1 mmol) Phen ( Figure 1Add the 1 to the reaction system a in step (1) and stir until homogeneous to obtain reaction system b.

[0058] (3) The above reaction system b was placed in a 10 mL transparent glass vial, sealed, and placed in an 80 ℃ oven for 12 h. After the reaction was completed, it was naturally cooled to room temperature to obtain red cluster crystals. The crystals were washed with distilled water and dried to obtain the target product, cobalt coordination polymer Co-CP ( Figure 2-3 Weigh and calculate the yield as 75% (based on Co(OAc)2·4H2O).

[0059] The crystallographic parameters of Co-CP are detailed in the table below:

[0060]

[0061] Example 2

[0062] Preparation of a 1% (w / w) core-shell structured fiber precursor Co-CP-1:

[0063] (1) Mix 7.88 mg Co-CP with 650 mg PAN and stir at room temperature for 20 min to ensure thorough mixing;

[0064] (2) Add 7 mL of DMF to the above mixture, heat at 60°C and stir for 2 h to form a homogeneous and stable spinning solution;

[0065] (3) Select coaxial electrospinning needles with inner and outer specifications of 18 G and 13 G, use the prepared spinning solution as the outer layer fluid and paraffin oil as the inner layer fluid; control the outer layer flow rate to 0.9 mL / h and the inner layer flow rate to 0.3 mL / h, set the spinning voltage to 20kV, and complete the electrospinning; place the obtained fibers in room temperature to air dry naturally, and obtain a 1% (w / w) core-shell structure fiber precursor Co-CP-1 ( Figure 4 ).

[0066] Example 3

[0067] Preparation of a 5% (w / w) core-shell structured fiber precursor Co-CP-1:

[0068] (1) Mix 41.1 mg Co-CP with 650 mg PAN and stir at room temperature for 20 min to ensure thorough mixing;

[0069] (2) Add 7 mL of DMF to the above mixture, heat at 60°C and stir for 2 h to form a homogeneous and stable spinning solution;

[0070] (3) Select coaxial electrospinning needles with inner and outer specifications of 18 G and 13 G, use the prepared spinning solution as the outer layer fluid and paraffin oil as the inner layer fluid; control the outer layer flow rate to 0.9 mL / h and the inner layer flow rate to 0.3 mL / h, set the spinning voltage to 20kV, and complete the electrospinning; place the obtained fibers in room temperature to air dry naturally, and obtain a 5% mass fraction core-shell structure fiber precursor Co-CP-1 ( Figure 5 ).

[0071] Example 4

[0072] Preparation of a 10% (w / w) core-shell structured fiber precursor Co-CP-1:

[0073] (1) Mix 86.7 mg Co-CP with 650 mg PAN and stir at room temperature for 20 min to ensure thorough mixing;

[0074] (2) Add 7 mL of DMF to the above mixture, heat at 60°C and stir for 2 h to form a homogeneous and stable spinning solution;

[0075] (3) Select coaxial electrospinning needles with inner and outer specifications of 18 G and 13 G, use the prepared spinning solution as the outer layer fluid and paraffin oil as the inner layer fluid; control the outer layer flow rate to 0.9 mL / h and the inner layer flow rate to 0.3 mL / h, set the spinning voltage to 20kV, and complete the electrospinning; place the obtained fibers in room temperature to air dry naturally, and obtain a 10% mass fraction core-shell structure fiber precursor Co-CP-1 ( Figure 6 ).

[0076] Example 5

[0077] Preparation of Co-CP-1, a core-shell structured fiber precursor with a mass fraction of 20%:

[0078] (1) Mix 195 mg Co-CP with 650 mg PAN and stir at room temperature for 20 min to ensure thorough mixing;

[0079] (2) Add 7 mL of DMF to the above mixture, heat at 60°C and stir for 2 h to form a homogeneous and stable spinning solution;

[0080] (3) Select coaxial electrospinning needles with inner and outer specifications of 18 G and 13 G, use the prepared spinning solution as the outer layer fluid and paraffin oil as the inner layer fluid; control the outer layer flow rate to 0.9 mL / h and the inner layer flow rate to 0.3 mL / h, set the spinning voltage to 20 kV, and complete the electrospinning; place the obtained fibers in room temperature to air dry naturally, and obtain a core-shell structured fiber precursor Co-CP-1 with a mass fraction of 20%. Figure 7).

[0081] Example 6

[0082] Preparation of Co-CP-1, a core-shell structured fiber precursor with a mass fraction of 30%:

[0083] (1) Mix 334.3 mg Co-CP with 650 mg PAN and stir at room temperature for 20 min to ensure thorough mixing;

[0084] (2) Add 7 mL of DMF to the above mixture, heat at 60°C and stir for 2 h to form a homogeneous and stable spinning solution;

[0085] (3) Select coaxial electrospinning needles with inner and outer specifications of 18 G and 13 G, use the prepared spinning solution as the outer layer fluid and paraffin oil as the inner layer fluid; control the outer layer flow rate to 0.9 mL / h and the inner layer flow rate to 0.3 mL / h, set the spinning voltage to 20kV, and complete the electrospinning; place the obtained fibers in room temperature to air dry naturally, and obtain a core-shell structured fiber precursor Co-CP-1 with a mass fraction of 30%. Figure 8 ).

[0086] The process for selecting the decoupling solvent in this invention is as follows:

[0087] To optimize the core removal effect and obtain a complete hollow structure, this invention first screened and explored the core removal solvents. Common solvents such as ethanol, deionized water, and acetonitrile were used to soak Co-CP-1 separately in an attempt to remove the internal paraffin oil core layer. Actual tests showed that these solvents had extremely poor solubility for paraffin oil and could not effectively dissolve the core layer, making it difficult to form a complete hollow structure and failing to meet the requirements of subsequent applications.

[0088] Furthermore, after determining the decoking solvent, the present invention set up a control experiment to optimize the decoking auxiliary method. Only petroleum ether was used for simple soaking (without ultrasonic auxiliary treatment). After static decoking, it was observed that the removal efficiency of the paraffin oil core layer was low and the residual amount was large. Moreover, long-term soaking easily caused the fiber morphology to collapse and the structure to break, affecting the integrity and stability of the hollow fiber.

[0089] Furthermore, after multiple sets of condition exploration and verification, the optimal core removal process conditions were determined to be: Soaking Co-CP-1 in petroleum ether and then ultrasonically treating it for 2 hours can fully and rapidly dissolve and remove the internal paraffin oil core layer without damaging the fiber structure; after core removal, washing with ethanol three times removes residual petroleum ether and trace impurities from the fiber surface, followed by natural air drying at room temperature to obtain a hollow fiber-based cobalt coordination polymer Co-CP-2 with a well-formed structure and uniform morphology. Figure 10 and Figure 11 ).

[0090] Example 7

[0091] Preparation of fiber-based Co-CP-2:

[0092] After determining the optimal core-removal method, the core-shell structured fiber precursor Co-CP-1 prepared in Example 4 was immersed in petroleum ether for core-removal treatment. Ultrasonic assistance was applied during the immersion process, and the core-removal treatment lasted for 2 hours to fully dissolve and remove the paraffin oil core layer inside the fiber. After the core-removal treatment, the fiber was washed three times with ethanol to remove residual solvent and impurities from the surface. The washed fiber was then dried to obtain a hollow fiber-based cobalt coordination polymer Co-CP-2 with a complete structure and regular morphology. Figure 10 and Figure 11 ).

[0093] Figure 9 This is a comparison of the XRD patterns of the Co-CP material prepared in Example 1 and the Cd-CP-2 material prepared in Example 7. From... Figure 9 It can be concluded that the XRD patterns of Co-CP and Co-CP-2 materials are completely identical except for the PAN peak, further demonstrating that the hollow spinning process did not disrupt the internal structure of the crystal.

[0094] Example 8

[0095] Preparation of In2S3@Co-CP-2a fiber-based composite material with an indium sulfide loading of 7%:

[0096] (1) Weigh 0.006 g of InCl3·4H2O and add it to a 20 mL reactor, and add 10 mL of EtOH. Stir at room temperature for 10-30 min.

[0097] (2) Weigh 0.05 g of the Co-CP-2 material from Example 7 and add it to the solution in (1).

[0098] (3) Dissolve 0.002 g of thioacetamide in 2 mL of H2O and add it dropwise into the glass bottle in (2).

[0099] (4) After sealing the above reaction system, place it in an oven at 150 °C for 12 h.

[0100] (5) Cool to room temperature, centrifuge, and wash repeatedly with H2O and EtOH 3-5 times to obtain In2S3@Co-CP-2a composite catalyst with an In2S3 content of 7%, named Co-CP-3a. Figure 12 ).

[0101] Example 9

[0102] Preparation of In2S3@Co-CP-2b fiber-based composite material with an indium sulfide loading of 11%:

[0103] (1) Weigh 0.012 g of InCl3·4H2O and add it to a 20 mL reactor, and add 10 mL of EtOH. Stir at room temperature for 10-30 min.

[0104] (2) Weigh 0.05 g of the Co-CP-2 material from Example 7 and add it to the solution in (1).

[0105] (3) Dissolve 0.003 g of thioacetamide in 2 mL of H2O and add it dropwise into the glass bottle in (2).

[0106] (4) After sealing the above reaction system, place it in an oven at 150°C for 12 h.

[0107] (5) Cool to room temperature, centrifuge, and wash repeatedly with H2O and EtOH 3-5 times to obtain In2S3@Co-CP-2b composite catalyst with an In2S3 content of 11%, named Co-CP-3b. Figure 13 ).

[0108] Example 10

[0109] Preparation of In2S3@Co-CP-2c fiber-based composite material with an indium sulfide loading of 18%:

[0110] (1) Weigh 0.024 g of InCl3·4H2O and add it to a 20 mL reactor, and add 10 mL of EtOH. Stir at room temperature for 10-30 min.

[0111] (2) Weigh 0.05 g of the Co-CP-2 material from Example 7 and add it to the solution in (1).

[0112] (3) Dissolve 0.006 g of thioacetamide in 2 mL of H2O and add it dropwise into the glass bottle in (2).

[0113] (4) After sealing the above reaction system, place it in an oven at 150°C for 12 h.

[0114] (5) Cool to room temperature, centrifuge, and wash repeatedly with H2O and EtOH 3-5 times to obtain In2S3@Co-CP-2c composite catalyst with an In2S3 content of 18%, named Co-CP-3c. Figure 14 ).

[0115] Example 11

[0116] Preparation of In2S3@Co-CP-2d fiber-based composite material with an indium sulfide loading of 24%:

[0117] (1) Weigh 0.035 g of InCl3·4H2O and add it to a 20 mL reactor, and add 10 mL of EtOH. Stir at room temperature for 10-30 min.

[0118] (2) Weigh 0.05 g of the Co-CP-2 material from Example 7 and add it to the solution in (1).

[0119] (3) Dissolve 0.009 g of thioacetamide in 2 mL of H2O and add it dropwise into the glass bottle in (2).

[0120] (4) After sealing the above reaction system, place it in an oven at 150°C for 12 h.

[0121] (5) Cool to room temperature, centrifuge, and wash repeatedly with H2O and EtOH 3-5 times to obtain In2S3@Co-CP-2d composite catalyst with In2S3 content of 24%, named Co-CP-3d. Figure 15 ).

[0122] Example 12

[0123] The catalytic material In2S3@Co-CP-2c prepared in Example 10 was used to conduct photocatalytic hydrogen peroxide preparation experiments in different reaction solvent systems. The specific steps are as follows:

[0124] (1) Prepare five different reaction substrate systems in a round-bottom flask: add 10 mL of purified water (H2O) to the first group; add 5 mL of purified water and 5 mL of methanol solution (MeOH) to the second group; add 5 mL of purified water and 5 mL of ethanol solution (EtOH) to the third group; add 5 mL of purified water and 5 mL of isopropanol solution (IPA) to the fourth group; and add 5 mL of purified water and 5 mL of benzyl alcohol solution (BA) to the fifth group.

[0125] (2) Add 0.01 g of the composite material Co-CP-3c as a catalyst to each of the above reaction systems and stir to make the catalyst evenly dispersed in the reaction solution.

[0126] (3) Seal each reaction system and introduce high-purity oxygen into the liquid surface for 10 min to replace the air in the system; then stir magnetically for 1 h at room temperature and in the dark to allow the catalyst and the reaction system to reach adsorption-desorption equilibrium.

[0127] (4) After stirring, turn on the xenon lamp as a simulated light source and irradiate the reaction for 1.5 h under continuous magnetic stirring; keep the temperature of each group of systems consistent during the reaction.

[0128] (5) After the reaction is completed, the reaction solutions of each group are centrifuged (5000 r / min, centrifugation time 5 min), and the supernatant is filtered through a 0.22 μm filter membrane and the filtrate is collected.

[0129] (6) Take 5 mL of filtrate, add 2 mL of titanium sulfate colorimetric solution, then add 13 mL of deionized water to make up to volume, mix thoroughly, and let stand for color development; use a UV-Vis spectrophotometer to measure the absorbance of each group of colorimetric solutions at 400 nm, and then... Figure 16 The hydrogen peroxide standard curve shown is used to calculate the amount of hydrogen peroxide generated in the reaction system, and the hydrogen peroxide yield per unit mass of catalyst (unit: mmol / g) is calculated. The test results for the different solvent systems are as follows... Figure 17 As shown, the yields of the catalyst In2S3@Co-CP-2c in different systems were: 6.6 mmol / g in the H2O system, 13.6 mmol / g in the MeOH system, 20.4 mmol / g in the EtOH system, 28.5 mmol / g in the IPA system, and 70.8 mmol / g in the BA system.

[0130] Example 13

[0131] Furthermore, using the catalytic materials In2S3@Co-CP-2a, In2S3@Co-CP-2b, and In2S3@Co-CP-2d prepared in Examples 8, 9, and 11 respectively as research objects, comparative experiments on the photocatalytic preparation of hydrogen peroxide were carried out in the optimal benzyl alcohol-water mixed solvent system. The specific steps are as follows:

[0132] (1) Add 5 mL of purified water and 5 mL of benzyl alcohol solution to each of the three round-bottom flasks to prepare the same reaction substrate system.

[0133] (2) Add 0.01 g of the corresponding catalytic material to the three round-bottom flasks: Co-CP-3a (prepared in Example 8) to the first group, Co-CP-3b (prepared in Example 9) to the second group, and Co-CP-3d (prepared in Example 11) to the third group, all of which are used as photocatalysts.

[0134] (3) After sealing the three reaction systems, oxygen was continuously introduced into each system for 10 min. The system was then magnetically stirred for 1 h in the dark at room temperature, and then the xenon lamp was turned on for visible light irradiation. The reaction was then magnetically stirred for 1.5 h.

[0135] (4) After the reaction was completed, the three systems were centrifuged and filtered respectively; 5 mL of filtrate was taken from each system, 2 mL of titanium sulfate solution was added, and then 13 mL of purified water was added. After color development with titanium sulfate, the solution was brought to volume; the ultraviolet absorption curves of each mixed solution were measured, and the results were determined according to... Figure 16 The hydrogen peroxide yield was calculated using the fitted equation, and the test results for all systems were as follows. Figure 18 As shown, under the same reaction conditions, the hydrogen peroxide yields of the four catalytic materials exhibited significant differences: Co-CP-3c had the highest yield, reaching 70.8 mmol / g; Co-CP-3d was second, with a yield of 55.3 mmol / g; Co-CP-3b had a yield of 49.3 mmol / g; and Co-CP-3a had the lowest yield, at 44.3 mmol / g. These results demonstrate that the series of catalytic materials prepared in this invention all possess excellent photocatalytic performance for hydrogen peroxide production, and that the composition and structure of the materials significantly influence the catalytic activity. Among these materials, Co-CP-3c prepared in Example 10 exhibited the best catalytic activity, providing an optimal solution for subsequent large-scale applications.

[0136] Example 14

[0137] Co-CP prepared in Example 1, Co-CP-2 prepared in Example 7, and pure-phase In2S3 were used as catalytic materials to conduct a comparative experiment on the photocatalytic preparation of hydrogen peroxide under the same conditions. The preparation method of pure-phase In2S3 was as follows: Indium chloride tetrahydrate ethanol solution was added to a container, followed by the addition of thioacetamide in a molar ratio of 1:1. The system was sealed and placed in an oven at 150°C for 12 h. After cooling to room temperature, the In2S3 catalytic material was obtained by filtration and drying.

[0138] (1) Add 5 mL of purified water and 5 mL of benzyl alcohol solution to each of the three round-bottom flasks; (2) Add 0.01 g of Co-CP, Co-CP-2 and self-made In2S3 as catalysts to the three reaction systems respectively; (3) Seal each reaction system, introduce oxygen for 10 min, stir magnetically in the dark at room temperature for 1 h, then irradiate with a xenon lamp and continue to stir magnetically for 1.5 h; (4) After the reaction is completed, centrifuge and filter each reaction solution, take 5 mL of filtrate, add 2 mL of titanium sulfate solution, add 13 mL of purified water, and make up to volume after titanium sulfate color development; determine the ultraviolet absorption curve of the mixed solution, calculate the hydrogen peroxide yield according to the fitting equation, and the test results of the three samples are as follows. Figure 19 As shown. By Figure 19It was found that under the same reaction conditions, the yield of hydrogen peroxide catalyzed by Co-CP was only 0.4 mmol / g; the modified Co-CP-2 showed improved activity, with a hydrogen peroxide yield of 4.3 mmol / g; and the pure indium sulfide material produced 35.3 mmol / g of hydrogen peroxide. Co-CP exhibited a fast recombination rate between photogenerated electrons and holes, resulting in a low number of effective charge carriers participating in oxygen reduction and thus a low hydrogen peroxide production efficiency. Modification to obtain Co-CP-2 slightly improved charge separation, but the improvement in activity was limited. Although the band structure of pure indium sulfide matched the reaction potential for oxygen reduction to hydrogen peroxide, making its catalytic activity superior to the two cobalt-based coordination polymers, it still suffered from problems such as excessively fast charge-hole separation efficiency, poor stability, and unstable products. The above comparison of the single-component performance results demonstrates the feasibility of constructing a heterojunction catalyst by combining cobalt-based coordination polymers and indium sulfide. This effectively improves visible light utilization, achieves efficient oxygen reduction, and is less likely to cause decomposition of the product hydrogen peroxide. The catalytic performance is superior to that of single-component catalysts. Therefore, the formation of a heterojunction interface between the two can optimize charge separation and transport efficiency, improve the kinetics of the interfacial oxygen reduction reaction, suppress the side decomposition of hydrogen peroxide, and thus achieve superior photocatalytic hydrogen peroxide production performance.

[0139] Example 15

[0140] The steps for the photocatalytic preparation of hydrogen peroxide using the recycled catalyst In2S3@Co-CP-2c are as follows:

[0141] (1) The composite material In2S3@Co-CP-2c separated by centrifugation in Example 12 was added again as a catalyst to a reaction system containing 5 mL of pure water and 5 mL of benzyl alcohol.

[0142] (2) Introduce oxygen into the reaction system (1) for 10 min, stir magnetically for 1 h in the dark, and then place it under a xenon lamp at room temperature for 1.5 h to complete the catalytic reaction.

[0143] (3) After the reaction is complete, the catalyst is recovered by centrifugation. Take 5 mL of the supernatant and add 2 mL of titanium sulfate solution and 13 mL of pure water in sequence. After mixing and color development, measure its ultraviolet-visible absorption spectrum and calculate the hydrogen peroxide yield according to the standard curve fitting equation.

[0144] (4) The composite material In2S3@Co-CP-2c obtained by centrifugation was used as a catalyst to continue repeating the catalytic experiment under the same conditions as in Example 12.

[0145] (5) The catalyst is recycled multiple times using the above method. After each cycle, the hydrogen peroxide yield is measured using the above steps to verify its cycle stability. Figure 20 ).

[0146] The above embodiments describe the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are only illustrative of the principles of the present invention. Various changes and modifications can be made to the present invention without departing from the scope of the principles of the present invention, and all such changes and modifications fall within the protection scope of the present invention.

Claims

1. A method for preparing a hollow fiber-based cobalt coordination polymer, characterized in that... Includes the following steps: (1) Preparation of cobalt coordination polymer Co-CP; (2) Add the Co-CP and PAN obtained in step (1) into N,N-dimethylformamide DMF, heat and stir until a uniform and stable spinning solution is formed; (3) Using a coaxial electrospinning device, the spinning solution prepared in step (2) is used as the outer layer fluid and paraffin oil is used as the inner layer fluid. The flow rate of the outer layer and the inner layer solution and the spinning voltage are controlled to carry out spinning. After spinning is completed, the obtained fiber membrane is placed at room temperature to air dry naturally to obtain the core-shell structure fiber precursor Co-CP-1. (4) The core-shell structure fiber precursor Co-CP-1 was soaked in petroleum ether for core removal treatment. Ultrasonic assistance was applied to the soaking process to fully dissolve and remove the paraffin oil core layer inside the fiber. After the core removal treatment was completed, the fiber was washed with ethanol to remove residual solvent and impurities on the surface. The washed fiber was dried to obtain hollow fiber-based cobalt coordination polymer Co-CP-2 with complete structure and regular morphology.

2. The method for preparing the hollow fiber-based cobalt coordination polymer according to claim 1, characterized in that, Step (1) The preparation method of cobalt coordination polymer Co-CP includes the following steps: a. Co(OAc)2·4H2O is added to a mixed solution of deionized water (H2O), acetonitrile (CH3CN), and ethanol (EtOH), and stirred at room temperature to obtain reaction system a. The volume ratio of CH3CN, EtOH, and H2O is (4-6):(2-3):(2-3). b. Add H2cpta (3,5-dicarboxyphenyl chloroacetamide) and Phen (1,10-phenanthroline) to reaction system a in step (1) respectively, and stir to obtain reaction system b. The molar ratio of Co(OAc)2·4H2O, Phen and H2cpta is (0.04-0.08):(0.1-0.2):(0.04-0.08). c. Place reaction system b in a transparent glass vial and react in an oven at 80-85℃ for 10-12 h, then cool to room temperature at a rate of 5-10℃ / h to obtain clustered red crystals; wash and dry successively with distilled water and acetonitrile to obtain Co-CP, with the molecular formula [Co(ctpa)(Phen)]. n , n=∞.

3. The method for preparing the hollow fiber-based cobalt coordination polymer according to claim 1, characterized in that, In step (2), the mass fraction of Co-CP in the spinning solution is 1%-30%, and 7 mL of DMF is added for every 650 mg PAN.

4. The method for preparing the hollow fiber-based cobalt coordination polymer according to claim 1, characterized in that, In step (3), the coaxial electrospinning needle has inner and outer specifications of 13 G and 18 G, the flow rates of the outer and inner solutions are 0.9-1.2 ml / h and 0.3-0.5 ml / h, respectively, the voltage is 18-20 kV, and the needle is air-dried at room temperature for 2-4 hours after spinning.

5. The method for preparing the hollow fiber-based cobalt coordination polymer according to claim 1, characterized in that, In step (4), the core-shell structure fiber precursor Co-CP-1 is soaked in petroleum ether and sonicated for 2-4 h, washed with ethanol 3-5 times, and then air-dried at room temperature to obtain hollow fiber-based cobalt coordination polymer Co-CP-2.

6. The hollow fiber-based cobalt coordination polymer Co-CP-2 prepared by any one of claims 1-5, characterized in that, The fibrous structure is preserved before and after core removal.

7. A method for preparing an indium sulfide composite hollow fiber-based cobalt coordination polymer material, characterized in that, The hollow fiber-based cobalt coordination polymer Co-CP-2 described in claim 6 was added to an ethanol solution of InCl3·4H2O, followed by the addition of thioacetamide. The mixture was then sealed and reacted in an oven. After the reaction was completed, the mixture was cooled, centrifuged, and washed with distilled water to obtain the indium sulfide composite hollow fiber-based cobalt coordination polymer material In2S3@Co-CP-2.

8. The preparation method according to claim 7, characterized in that, The mass ratio of Co-CP-2, InCl3·4H2O, and thioacetamide is 0.05:(0.006-0.035):(0.002-0.009), the reaction temperature is 150-160℃, and the reaction time is 10-12 h.

9. The indium sulfide composite hollow fiber-based cobalt coordination polymer material In2S3@Co-CP-2 prepared by the preparation method of claim 7 or 8, characterized in that, Maintain the hollow structure of the hollow fiber-based cobalt coordination polymer Co-CP-2.

10. The application of In2S3@Co-CP-2 as a catalytic material according to claim 9 in the photocatalytic preparation of hydrogen peroxide, characterized in that, Using purified water and benzyl alcohol as substrates, In2S3@Co-CP-2 was added, oxygen was introduced for 10 minutes, and the mixture was stirred in the dark for 1 hour. Then, it was stirred under visible light for 1.5 hours to complete the catalysis.

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