Ni-pt bimetallic covalent organic framework material, and preparation method and application thereof

Abstract

The application discloses a kind of Ni-Pt bimetallic covalent organic framework material and its preparation method and application, the preparation method includes the following steps: preparation covalent organic framework material ILCOF-1, with nickel salt is mixed, grinding, heat treatment, the obtained Ni-ILCOF-1 is mixed with platinum salt solution, adsorption, drop into NaBH4 solution and carry out in situ reduction, obtain Ni-Pt bimetallic covalent organic framework material.The Ni-Pt bimetallic covalent organic framework material prepared in the application has the advantages of large specific surface area, many bimetallic active sites, high visible light utilization rate, strong electron-proton coupling ability, high photocatalytic activity and excellent structural stability, as a kind of new photocatalyst with excellent performance, in the field such as photocatalytic production of hydrogen peroxide, water purification, has significant advantages, shows high reaction rate, high quantum efficiency and excellent light stability, and has wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of materials chemistry and catalyst preparation technology, specifically relating to a Ni-Pt bimetallic covalent organic framework material, its preparation method, and its application. Background Technology

[0002] Covalent organic frameworks (COFs) have shown significant potential in photocatalysis due to their ordered porous structure, tunable π-conjugated system, and good chemical stability. Although COFs can achieve high specific surface area and controllable light absorption through framework design to regulate band gap, the photogenerated electron-hole pairs in traditional COFs are still prone to nonradiative recombination, and the density of active sites is limited, making it difficult to meet the requirements of efficient photocatalytic conversion. Furthermore, existing COFs also suffer from poor crystallinity, poor stability, and a lack of conductive channels, making it difficult to provide an effective pathway for charge-proton transport.

[0003] To improve the photocatalytic efficiency of COFs, existing technologies propose strategies to load metal particles or single-atom metals onto COFs. There are two main preparation methods: one is to modify the COF with metal through impregnation or physical loading, but this method easily leads to metal agglomeration, framework destruction, and low interfacial coupling efficiency; the other is to add a metal precursor during the synthesis of COFs and modify the COF with metal during polymerization. The metal precursor used in this method interferes with COF crystallization, easily causing a decrease in the specific surface area and pore blockage of the COF. For example, existing technologies propose a method for preparing a Pt-Ni bimetallic doped CTF-1 composite material. Using the covalent triazine framework material CTF-1 as a raw material, methanol, a mixed solution of platinum salt and transition metal salt are added, stirred, and sodium borohydride is added for reaction. The mixture is then centrifuged, washed, and dried to obtain the Pt-Ni bimetallic doped CTF-1 composite material. However, in this preparation method, CTF-1 is used as a carrier, which has poor crystallinity, poor stability, and lacks conduction channels, making it difficult to provide an effective path for charge-proton transport. In addition, directly reacting platinum salts and transition metal salts with CTF-1 easily leads to metal agglomeration, framework destruction, and low interfacial coupling efficiency. In particular, platinum and nickel exist in the form of metal particles and cannot form a heterojunction electronic structure with CTF-1, making it impossible to achieve dynamic control of electron-proton and difficult to simultaneously take into account the bimetallic synergistic effect and carrier stability. That is, the prepared Pt-Ni bimetallic doped CTF-1 composite material still has defects such as small specific surface area, few active sites, low visible light absorption, poor metal dispersion, low interfacial charge transfer efficiency, poor stability, and poor photoelectrocatalytic performance. As a result, it is difficult to produce hydrogen peroxide efficiently under light conditions.

[0004] For the reasons stated above, this invention is proposed. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a Ni-Pt bimetallic covalent organic framework material with large specific surface area, many bimetallic active sites, high visible light utilization, strong electron-proton coupling ability, high photocatalytic activity and excellent structural stability, as well as its preparation method and application.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0007] A method for preparing a Ni-Pt bimetallic covalent organic framework material includes the following steps: S1. Preparation of covalent organic framework material ILCOF-1; S2. The covalent organic framework material ILCOF-1 obtained in step S1 is mixed with nickel salt, ground, and heat-treated to complete the in-situ metal coordination and anchoring of nickel, thus obtaining Ni-ILCOF-1. S3. Prepare a dispersion of Ni-ILCOF-1 obtained in step S2, add a platinum salt solution for adsorption, and add NaBH4 solution dropwise for in-situ reduction, so that platinum is anchored on Ni-ILCOF-1 to form a bimetallic synergistic structure, and obtain Ni-Pt bimetallic covalent organic framework material.

[0008] A further improvement to the above preparation method is that, in step S1, the preparation method of the covalent organic framework material ILCOF-1 includes the following steps: S1-1. Mix aromatic polyaldehyde monomers, amine monomers and mixed solvents, disperse by ultrasonication, and add acidic catalyst during ultrasonic dispersion to obtain a mixed solution; S1-2. The mixture obtained in step S1-1 is subjected to a freezing-vacuuming-nitrogen purging cycle to obtain a precursor solution; S1-3. The precursor solution obtained in step S1-2 is subjected to a solvothermal reaction to obtain the covalent organic framework material ILCOF-1.

[0009] The above-described preparation method is further improved in that the preparation method of the covalent organic framework material ILCOF-1 satisfies at least one of the following conditions; (1.1) In step S1-1, the molar ratio of the aromatic polyaldehyde monomer and the amine monomer is 1:1 to 2; (1.2) In step S1-1, the aromatic polyaldehyde monomer is TFPPy; the amine monomer is at least one of p-phenylenediamine, 4,4'-diaminobiphenyl, and 4,4'-diaminoazobenzene; (1.3) In step S1-1, the mixed solvent is a mixture of o-dichlorobenzene and n-butanol; the volume ratio of o-dichlorobenzene to n-butanol is 1:1; (1.4) In step S1-1, the process conditions for ultrasonic dispersion are: power of 150 W to 300 W, temperature ≤ 35 ℃, and time of 5 min to 20 min; (1.5) In step S1-1, the mass-to-volume ratio of the aromatic polyaldehyde monomer to the acidic catalyst is 40 mg: 200 μL; the acidic catalyst is an acetic acid solution; the concentration of the acetic acid solution is 6 M; (1.6) In step S1-2, the freezing-vacuuming-nitrogen filling cycle is performed at least 3 times; (1.7) In steps S1-3, the temperature of the solvothermal reaction is 100 ℃~150 ℃; the time of the solvothermal reaction is 48 h~96 h; (1.8) In step S1-3, after the solvothermal reaction is completed, the product is subjected to Soxhlet extraction or continuous flow washing with acetone, methanol and ethanol in sequence, and dried at a temperature of 60 ℃~100 ℃ for 8 h~24 h to obtain covalent organic framework material ILCOF-1.

[0010] In a further improvement to the above preparation method, in step S2, the mass ratio of the covalent organic framework material ILCOF-1 to the nickel salt is 2:0.5 to 2; the nickel salt is nickel acetylacetonate; the heating rate during the heat treatment is 2℃ / min to 5℃ / min; the heat treatment temperature is 20℃ to 200℃; and the heat treatment time is 2 h to 6 h.

[0011] In a further improvement to the above preparation method, in step S3, the dispersion is prepared by dispersing Ni-ILCOF-1 in water; the mass-to-volume ratio of Ni-ILCOF-1 to water is 20 mg:100 mL; the volume ratio of the dispersion to the platinum salt solution is 100:0.4; the platinum salt solution is a chloroplatinic acid solution; and the concentration of the chloroplatinic acid solution is 0.3 mg·mL. -1 ~1 mg·mL -1 The adsorption time is 0.5 h to 2 h; the volume ratio of the dispersion to the NaBH4 solution is 100:0.4; the concentration of the NaBH4 solution is 1 mg / mL to 2 mg / mL; and the in-situ reduction time is 2 h to 5 h.

[0012] As a general technical concept, the present invention also provides a Ni-Pt bimetallic covalent organic framework material, which is prepared by the above-described preparation method.

[0013] The aforementioned Ni-Pt bimetallic covalent organic framework material is further improved by comprising a covalent organic framework material ILCOF-1, a Ni semiconductor, and Pt species. The Ni semiconductor is distributed on the surface of the covalent organic framework ILCOF-1 through coordination fixation and thermo-solid phase embedding to form Ni-ILCOF-1. The Pt species are distributed on the surface of the Ni-ILCOF-1 in an atomic or sub-nanometer dispersed form. A portion of the Pt species is fixed in the local channel region of the covalent organic framework ILCOF-1 and is distributed hierarchically around the Ni semiconductor to form a heterojunction electronic structure. The Ni semiconductor is β-Ni(OH)2 and NiOOH. The Pt species is zero-valent platinum and platinum oxide.

[0014] In a further improvement of the aforementioned Ni-Pt bimetallic covalent organic framework material, the Ni content is 1.5 wt% to 2.0 wt%, and the Pt content is 0.8 wt% to 2 wt%.

[0015] As a general technical concept, the present invention also provides an application of the above-mentioned Ni-Pt bimetallic covalent organic framework material in the synthesis of H2O2.

[0016] As a general technical concept, the present invention also provides an application of the above-mentioned Ni-Pt bimetallic covalent organic framework material in the removal of odor substances from water.

[0017] Compared with the prior art, the advantages of the present invention are as follows: (1) In view of the shortcomings of existing COF-based photocatalysts, such as insufficient visible light absorption, limited active sites, poor metal dispersion, and low interfacial charge transfer efficiency, this invention creatively provides a method for preparing Ni-Pt bimetallic covalent organic framework materials. Using covalent organic framework material ILCOF-1 as the main framework, Ni is first introduced by solid-phase heat treatment, and then Pt is introduced by liquid-phase adsorption-chemical reduction. Through the stepwise construction of bimetals, the material forms a stable heterojunction electronic structure. Specifically, by introducing coordinateable organic monomers, Ni can form a Ni(OH)2 heterojunction with ILCOF-1 to achieve the construction of structurally stable Ni sites. Then, a mild chemical or photochemical reduction strategy is adopted to reduce a small amount of Pt precursor in situ in the framework channels and be stably anchored by the adjacent N / O sites to form Ni-Pt neighboring bimetallic sites. Compared with traditional single-metal or physical mixing methods, the Ni-Pt bimetallic covalent organic framework material prepared by the method of this invention can achieve high dispersion and strong interfacial charge coupling of the bimetals while maintaining the high specific surface area and regular order of ILCOF-1. It has a larger surface area, wider visible light absorption, higher electron-proton coupling efficiency, stronger interfacial polarization, and better structural stability in aquatic environments. This lays the foundation for its high activity and high durability in applications such as efficient in-situ H2O2 generation through photocatalysis. Specifically: (a) The introduced Ni sites (Ni(OH)2 and NiOOH) have reversible Ni 2+ / Ni 3+ Valence state transitions can promote proton-coupled electron transfer (PCET), thus Ni can establish electron regulation centers near the channels and framework, improving the ability to regulate the electron density distribution of ILCOF-1. Simultaneously, the introduced Pt sites (zero-valent platinum and platinum oxide) possess excellent electron trapping and catalytic capabilities, with zero-valent platinum (Pt) sites being particularly effective. 0 It exists in the form of platinum oxide (PtO) and Pt 0As an electron trapping site, PtO acts as a hole trapping site, which can directionally promote the separation of electrons and holes, rapidly capture photogenerated electrons, and improve reaction selectivity. Therefore, Pt exists in the form of highly dispersed nanoclusters, which can serve as strong electron trapping centers. It can synergistically construct charge migration pathways with Ni sites and form a stable heterojunction electronic structure. It can be seen that introducing Ni and Pt into the covalent organic framework material ILCOF-1 can form bimetallic synergistic sites in a localized range. This can significantly extend the light absorption boundary of the material, improve the photogenerated electron generation efficiency, enhance the interfacial electron-hole spatial separation capability, reduce the recombination rate, and prolong the carrier lifetime. Thus, the photocatalytic performance of Ni-Pt bimetallic covalent organic framework materials can be significantly improved by utilizing the bimetallic site heterojunction constructed by Ni / Pt synergistically. (b) By introducing Ni sites through thermosolid phase, the metal-framework interface becomes more robust while maintaining the high specific surface area and channel structure of ILCof-1. The subsequently introduced Pt sites promote stable dispersion of Pt sites, preventing large-scale aggregation and blockage of ILCof-1 channels, and improving interfacial charge transfer efficiency. This results in the Ni-Pt bimetallic covalent organic framework material of this invention possessing a bimetallic synergistic structure, maintaining high stability during illumination, exhibiting significant resistance to charge accumulation, and being more suitable for long-term cyclic use. Furthermore, in the Ni-Pt bimetallic covalent organic framework material prepared in this invention, Ni(OH)2 spontaneously generates protons during illumination and reacts with NiOOH. After the reaction ends and the light is turned off, it reverts to Ni(OH)2. This allows for the transfer of Ni through the... 2+ / Ni 3+ The reversible redox mechanism provides protons, enabling the Ni-Pt bimetallic covalent organic framework material of this invention to exhibit superior hydrogen peroxide production even in alkaline, proton-deficient conditions, thus overcoming the bottleneck of photocatalytic hydrogen peroxide production under alkaline water. Therefore, the Ni-Pt bimetallic covalent organic framework material prepared in this invention possesses advantages such as large specific surface area, numerous bimetallic active sites, high visible light utilization, strong electron-proton coupling ability, high photocatalytic activity, and excellent structural stability. As a novel photocatalyst with superior performance, it exhibits significant advantages in photocatalytic hydrogen peroxide production and water purification, demonstrating high reaction rates, high quantum efficiency, and excellent photostability, showing broad application prospects.

[0018] (2) The preparation method of the present invention has the advantages of mild and controllable preparation conditions, simple process steps, easy operation, readily available reaction equipment and raw materials, low energy consumption, high preparation efficiency and strong repeatability. Compared with traditional impregnation method, physical mixing method, etc., the Ni-Pt bimetallic covalent organic framework material prepared by the preparation method of the present invention has higher metal dispersion, better composite performance and stronger reusability, and is more suitable for industrial promotion and application.

[0019] (3) In the preparation method of the present invention, by optimizing the mass ratio of covalent organic framework material ILCOF-1 to nickel salt to 2:0.5-2, and the platinum loading, the photoelectric properties of the material can be significantly improved, such as: higher photocurrent response, lower interfacial charge impedance, stronger electron-hole separation capability, and better bimetallic synergistic effect. If the metal content is too low, the electronic regulation will be insufficient; if it is too high, the metal agglomeration will block the pores, resulting in a decrease in specific surface area and a reduction in active sites. Therefore, the ratio range of the present invention achieves the optimal performance balance.

[0020] (4) In the preparation method of the present invention, by optimizing the molar ratio of aromatic polyaldehyde monomers and amine monomers to 1:1 to 2, ILCOF-1 with higher crystallinity and more regular pores can be obtained, providing a stable framework for subsequent metal intercalation. If the molar ratio deviates too much, disordered polymers are easily generated, resulting in a significant reduction in performance.

[0021] (5) The bimetallic site covalent organic framework composite catalyst prepared by the present invention comprises ILCof-1 (the main framework) and supported / embedded Ni and Pt bimetals. The metals are uniformly, stably, and controllably positioned on the surface and inner pore regions of the framework without damaging the COF structure or causing pore blockage. More importantly, by using Ni with a content of 1.5 wt% to 2.0 wt% and Pt with a content of 0.8 wt% to 2 wt% in the Ni-Pt bimetallic covalent organic framework material, the COF structure is almost undamaged, the pores remain open, the number of active sites is significantly increased, and the charge migration path is continuous and efficient, thereby achieving a significant improvement in photocatalytic performance. Attached Figure Description

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0023] Figure 1 The powder XRD patterns are those of Ni-ILCOF-1, Pt-ILCOF-1, Ni-Pt-ILCOF-1 prepared in Example 1 of the present invention and ILCOF-1 prepared in Comparative Example 1.

[0024] Figure 2 The Fourier transform infrared (FT-IR) spectra of Ni-ILCOF-1, Pt-ILCOF-1, Ni-Pt-ILCOF-1 prepared in Example 1 of the present invention and ILCOF-1 prepared in Comparative Example 1 are shown.

[0025] Figure 3These are high-resolution XPS spectra of Ni-ILCOF-1, Pt-ILCOF-1, Ni-Pt-ILCOF-1 prepared in Example 1 of the present invention, and ILCOF-1 prepared in Comparative Example 1.

[0026] Figure 4 These are TEM images of Ni-Pt-ILCOF-1 prepared in Example 1 of the present invention and ILCOF-1 prepared in Comparative Example 1.

[0027] Figure 5 The image shows the photocatalytic hydrogen peroxide production effect of Ni-Pt-ILCOF-1, Ni-ILCOF-1, Pt-ILCOF-1 prepared in Example 1 of the present invention and ILCOF-1 prepared in Comparative Example 1 under light irradiation.

[0028] Figure 6 shows the photoluminescence (PL) spectra of Ni-Pt-ILCOF-1, Ni-ILCOF-1, Pt-ILCOF-1 prepared in Example 1 of the present invention and ILCOF-1 prepared in Comparative Example 1.

[0029] Figure 7 Electrochemical impedance spectroscopy (EIS) spectra of Ni-Pt-ILCOF-1, Ni-ILCOF-1, Pt-ILCOF-1 prepared in Example 1 of this invention, and ILCOF-1 prepared in Comparative Example 1.

[0030] Figure 8 The photocurrent response diagrams are for Ni-Pt-ILCOF-1, Ni-ILCOF-1, Pt-ILCOF-1 prepared in Example 1 of the present invention and ILCOF-1 prepared in Comparative Example 1.

[0031] Figure 9 shows the stability test diagram of the Ni-Pt bimetallic covalent organic framework material in Example 2 of the present invention under light irradiation to generate H2O2.

[0032] Figure 10 The image shows the removal effect of Ni-Pt bimetallic covalent organic framework material (Ni-Pt-ILCOF-1) on geosmin (GSM) and 2-methylisoborneol (2-MIB) in water in Example 3 of this invention. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0034] In the following embodiments of the present invention, unless otherwise specified, the materials and instruments used are commercially available, the equipment used is conventional equipment, and the data obtained are the average values ​​of more than three repeated experiments.

[0035] Example 1 A method for preparing a Ni-Pt bimetallic covalent organic framework material includes the following steps: (1) Preparation of ILCof-1 precursor: 40 mg of 1,3,6,8-tetra(4-formylphenyl)pyrene (TFPPy) and 14 mg of p-phenylenediamine (PDA) were weighed and added to a 10 mL sealed glass tube. Then, a mixed solvent of 1.2 mL of o-dichlorobenzene and 1.2 mL of n-butanol was added. The mixture was ultrasonically dispersed at 200 W and 25 °C for 10 min. Under continuous ultrasonication, 200 μL of 6 M glacial acetic acid was added dropwise, and ultrasonication was continued for 5 min. Three cycles of freezing-vacuuming-nitrogen purging were performed to obtain a homogeneous precursor solution. The reaction tube was then sealed and heated at 120 °C for 72 h. The product was washed sequentially with acetone, methanol, and ethanol, and then vacuum-dried at 80 °C for 12 h to obtain the covalent organic framework material ILCof-1.

[0036] (2) Preparation of Ni–ILCOF-1: 20 mg of covalent organic framework material ILCOF-1 and 10 mg of nickel acetylacetone (Ni(acac)2) were ground evenly and transferred into a crucible. The mixture was then heated to 160 °C for 4 h at a heating rate of 3 °C / min. After cooling, the mixture was washed with deionized water and dried under vacuum at 60 °C for 12 h to complete the in-situ metal coordination and anchoring of nickel, thus obtaining Ni-ILCOF-1.

[0037] (3) Preparation of Ni-Pt-ILCOF-1: 20 mg of Ni-ILCOF-1 was dispersed in 100 mL of deionized water and sonicated for 10 min. Then, 400 μL of H2PtCl6·6H2O solution (0.5 mg / mL) was added and stirred for 1 h. Subsequently, 400 μL of NaBH4 solution (1.5 mg / mL) was added dropwise for in-situ reduction reaction for 3 h. After centrifugation and washing, the material was vacuum dried at 80 °C for 12 h to anchor platinum on Ni-ILCOF-1 and form a bimetallic synergistic structure, thus obtaining the Ni-Pt bimetallic covalent organic framework material, namely Ni-Pt-ILCOF-1.

[0038] In this embodiment, the prepared Ni-Pt bimetallic covalent organic framework material Ni-Pt-ILCOF-1 includes a covalent organic framework ILCOF-1, a Ni semiconductor, and Pt species. Both the Ni semiconductor and Pt species are distributed on the surface and in the channels of the framework, achieving bimetallic synergy. Specifically, the Ni semiconductor is distributed on the surface of the covalent organic framework ILCOF-1 in a coordinated and thermo-solid phase embedding manner to form Ni-ILCOF-1. The Pt species are distributed on the surface of Ni-ILCOF-1 in an atomic or sub-nanometer dispersed form. Some Pt ​​species are fixed in the local channel region of the covalent organic framework ILCOF-1 and are distributed in stages around the Ni semiconductor to form a heterojunction electronic structure.

[0039] In this embodiment, the Ni semiconductor is β-Ni(OH)2 and NiOOH; the Pt species is zero-valent platinum and platinum oxide.

[0040] In this embodiment, the Ni-Pt bimetallic covalent organic framework material contains 1.82 wt% Ni and 1.11 wt% Pt.

[0041] Comparative Example 1 A method for preparing Pt-ILCOF-1 is the same as in Example 1, except that Pt metal is modified onto ILCOF-1. Specifically, 20 mg of ILCOF-1 is dispersed in 100 mL of deionized water, sonicated for 10 min, 400 μL of H2PtCl6·6H2O solution (0.5 mg / mL) is added, and the mixture is stirred for 1 h. Then, 400 μL of NaBH4 solution (1.5 mg / mL) is added dropwise for in-situ reduction reaction for 3 h. After centrifugation and washing, the mixture is vacuum dried at 80 °C for 12 h to obtain Pt-ILCOF-1.

[0042] Pt-ILCOF-1 comprises a covalent organic framework and Pt sites, distributed on the surface of the framework and in its pores.

[0043] XRD analysis Figure 1 The images show the powder XRD patterns of Ni-ILCOF-1, Pt-ILCOF-1, Ni-Pt-ILCOF-1 prepared in Example 1 of this invention, and ILCOF-1 prepared in Comparative Example 1. Figure 1As shown, ILCOF-1 exhibits a typical (100) crystal plane diffraction peak at 2θ = 3.6°, indicating that the two-dimensional covalent organic framework has been successfully constructed and possesses a well-ordered structure. In contrast, the Ni-ILCOF-1, Pt-ILCOF-1, and Ni-Pt-ILCOF-1 obtained in Example 1 all maintain the main diffraction peak positions and shapes of ILCOF-1, and no impurity diffraction peaks appear, indicating that the introduction of metal species has not destroyed the crystal structure or π-conjugated network of COF. At the same time, the diffraction peak intensities of the samples are basically consistent with those of pure ILCOF-1, indicating that the integrity of the framework and long-range order are maintained. In addition, both Ni-ILCOF-1 and Ni-Pt-ILCOF-1 samples show obvious diffraction peaks at 2θ = 19.3°, corresponding to the (001) crystal plane of β-Ni(OH)2 (PDF#14-0117), proving that the introduced Ni species are anchored in the COF in the form of Ni(OH)2. The PXRD pattern of Pt-ILCOF-1 was almost identical to that of ILCOF-1, and no diffraction signal of gold (Pt) was observed, indicating that Pt was atomically dispersed or formed ultra-small nanoclusters within the framework. In summary, the PXRD results show that the metal species were introduced into the COF matrix in a dispersed state, and this process did not disrupt the ordered structure or chemical stability of the covalent organic framework. Furthermore, the PXRD results indicate that a good crystal structure was maintained after the introduction of the metal, and the local peak shifts and intensity changes suggest that the stepwise integration of Ni and Pt triggered localized framework reconstruction.

[0044] FTIR analysis Figure 2 The Fourier transform infrared (FT-IR) spectra of Ni-ILCOF-1, Pt-ILCOF-1, Ni-Pt-ILCOF-1 prepared in Example 1 of this invention, and ILCOF-1 prepared in Comparative Example 1 are shown. Figure 2 As shown, all samples were at 1680 cm⁻¹ -1 The characteristic absorption peak at the C=N stretching vibration indicates that the imine-bonded COF framework remains stable after metal introduction, without breakage or rearrangement. This result further confirms the good chemical integrity of the COF, consistent with the PXRD findings. Additionally, Figure 2 The results show the vibrational peaks of C=N, CN, and aromatic ring framework. The slight shifts and intensity differences of the relevant characteristic peaks after the introduction of the metal illustrate the coordination effect and electronic structure regulation effect between the metal and the framework.

[0045] XPS Analysis Figure 3These are high-resolution XPS spectra of Ni-ILCOF-1, Pt-ILCOF-1, Ni-Pt-ILCOF-1 prepared in Example 1 of the present invention, and ILCOF-1 prepared in Comparative Example 1. Figure 3 The XPS full spectrum and C 1s high-resolution spectrum of Ni-Pt-ILCOF-1 are shown. Figure 3 The full spectrum indicates the presence of C, N, O, Ni, and Pt elements in the material, further confirming the successful introduction of the metal into the COF matrix. The C 1s peak fitting shows a typical C / C=C (sp) peak. 2 The presence of aromatic carbon and C=N (imine bond) signal peaks indicates that the π-conjugated network and framework structure remain intact and have not been disrupted by metal coordination. Furthermore, Figure 3 The study clearly reveals the Ni(II) / Ni(III) valence state transition and the electronic regulation effect of Pt, providing direct evidence for the "dynamic valence state regulation - enhanced electron-proton coupling" mechanism in this invention.

[0046] Furthermore, in this invention, in-situ XPS was used to monitor the valence state evolution of Ni-Pt-ILCOF-1 during photocatalysis. The results showed that under illumination, Ni... 3+ / Ni 2+ The ratio increased from 0.19 to 0.32, confirming the presence of reversible Ni in the reaction. 3+ / Ni 2+ The interconversion between the two suggests its role in dynamically regulating photogenerated holes. Meanwhile, the Pt 4f spectrum under illumination shows Pt... 0 The binding energy shifts negatively by 0.13 eV (electron enrichment), while Pt 2+ The binding energy shifts positively by 0.23 eV (hole enrichment), indicating that Pt exhibits bidirectional charge modulation. Therefore, in the Ni-Pt bimetallic covalent organic framework material prepared in this invention, Ni coexists as β-Ni(OH)₂ with a small amount of NiOOH heterojunction (under illumination, a dynamic cycle of 2,3 valences occurs), and Pt exists as Pt₂. 0 They coexist with PtO, both existing as heterojunction structures. In particular, those based on Ni... 3+ / Ni 2+ The dynamic cycle provides protons to alleviate the bottleneck of the sharp drop in hydrogen peroxide production under alkaline conditions, while the self-generated protons are combined with Pt 0 PtO enables efficient hydrogen peroxide production under alkaline conditions through the directional transport of electrons and holes.

[0047] TEM analysis Figure 4 These are TEM images of Ni-Pt-ILCOF-1 prepared in Example 1 of the present invention and ILCOF-1 prepared in Comparative Example 1. Figure 4In the diagram, a represents ILCOF-1, and b represents Ni-Pt-ILCOF-1. Figure 4 In the HRTEM, lattice fringes of approximately 0.229 nm were clearly observed, corresponding to the β-Ni(OH)2(101) crystal plane; simultaneously, fringes of approximately 0.231 nm and 0.210 nm were detected, attributed to ultrasmall Pt nanocrystals (<5 nm) and PtO, respectively. Furthermore, Figure 4 The results showed that no large metal particles were present in the sample, indicating that Pt was mainly loaded on COF in a highly dispersed form. In summary, TEM results jointly show that Ni and Pt are uniformly distributed and maintain a highly dispersed state, and the introduction of metals did not disrupt the morphology and structure of COF, providing a structural basis for subsequent bimetallic synergistic effects.

[0048] Investigating the application of Ni-Pt bimetallic covalent organic framework materials in the synthesis of H2O2 Two mg of each of the following materials prepared in Example 1 of this invention (Ni-Pt-ILCOF-1, Ni-ILCOF-1, Pt-ILCOF-1, and ILCOF-1 prepared in Comparative Example 1) were added to 100 mL of ultrapure water. The mixtures were reacted in the dark for 30 min with magnetic stirring at 400 r / min to reach adsorption-desorption equilibrium. Subsequently, photocatalytic hydrogen peroxide production was carried out under 405 nm LED illumination for 60 min. After the reaction was completed, the concentration of hydrogen peroxide in the water was measured, and the photocatalytic hydrogen peroxide production efficiency of different materials was calculated.

[0049] Figure 5 The images show the photocatalytic hydrogen peroxide production effects of Ni-Pt-ILCOF-1, Ni-ILCOF-1, Pt-ILCOF-1 prepared in Example 1 of this invention, and ILCOF-1 prepared in Comparative Example 1 under light irradiation. Figure 5 It can be seen that after 60 min of reaction, the H2O2 generation rate of Ni-Pt-ILCOF-1 reaches 8070 μmol. g -1 h -1 It was significantly higher than that of ILCof-1 (2030 μmol). g -1 h -1 Pt-ILCOF-1 (2900 μmol) g -1 h -1 ) and Ni-ILCOF-1 (6580 μmol) g -1 h-1 The results show that the Ni-Pt bimetallic covalent organic framework material prepared in this invention has superior photocatalytic performance and can efficiently synthesize hydrogen peroxide.

[0050] Based on the XRD, FTIR, XPS, TEM, and photocatalytic performance results described above, this invention successfully prepared a Ni-Pt bimetallic covalent organic framework material. The introduction of Ni and Pt not only improved the charge separation efficiency of ILCOF-1 but also enhanced its photocatalytic activity through interfacial synergy. In particular, Example 1 (Ni-Pt-ILCOF-1) exhibited the best structural stability and photocatalytic performance, demonstrating that the introduction of the Ni-Pt bimetallic sites can achieve optimal charge dynamic regulation and interfacial electron transfer.

[0051] The steady-state photoluminescence (PL) spectra of Ni-Pt-ILCOF-1, Ni-ILCOF-1, Pt-ILCOF-1 prepared in Example 1 of this invention and ILCOF-1 prepared in Comparative Example 1 were examined, and the results are as follows: Figure 6 As shown.

[0052] Figure 6 shows the photoluminescence (PL) spectra of Ni-Pt-ILCOF-1, Ni-ILCOF-1, Pt-ILCOF-1 prepared in Example 1 of this invention, and ILCOF-1 prepared in Comparative Example 1. As shown in Figure 6, ILCOF-1 exhibits a strong PL emission intensity, indicating that its photogenerated electron-hole recombination is relatively severe. In contrast, the PL intensity of Ni-ILCOF-1 and Pt-ILCOF-1 is significantly weakened, indicating that single-metal regulation can suppress recombination to a certain extent. In addition, Ni-Pt-ILCOF-1 has the lowest PL emission intensity, which is much lower than that of other samples. This result indicates that the bimetallic synergistic structure can suppress the recombination of photogenerated carriers to the greatest extent and improve the electron-hole separation efficiency, which is consistent with its superior photoelectric performance. This also shows that the stepwise introduction of Ni and Pt can significantly reduce the PL intensity, indicating that the carrier recombination rate is effectively suppressed, which is consistent with the enhanced electron-proton coupling effect induced by bimetals.

[0053] To verify the photogenerated carrier recombination behavior of the metal-covalent organic framework composite catalyst, the steady-state photoluminescence (PL) spectra of different samples were compared. Specifically, under the same conditions (excitation wavelength 365 nm, room temperature solid-state testing mode), the PL intensities of Ni-Pt-ILCOF-1, Ni-ILCOF-1, Pt-ILCOF-1 prepared in Example 1, and ILCOF-1 prepared in Comparative Example 1 were measured to evaluate their photogenerated electron-hole pair recombination efficiency.

[0054] Figure 7The images show the electrochemical impedance spectroscopy (EIS) spectra of Ni-Pt-ILCOF-1, Ni-ILCOF-1, Pt-ILCOF-1 prepared in Example 1 of this invention, and ILCOF-1 prepared in Comparative Example 1. Figure 7 It can be seen that ILCOF-1 has the largest Nyquist radius, while the radius of the metal covalent organic framework composite catalyst gradually decreases, with Ni-Pt-ILCOF-1 having the smallest radius. This indicates that it has the lowest charge transport resistance and the highest charge migration efficiency, further proving that the introduction of Ni and Pt strengthens the electron migration path and reduces interfacial polarization.

[0055] Figure 8 The images show the photocurrent response diagrams of Ni-Pt-ILCOF-1, Ni-ILCOF-1, Pt-ILCOF-1 prepared in Example 1 of this invention, and ILCOF-1 prepared in Comparative Example 1. Figure 8 It can be seen that ILCOF-1 has a low photoresponse intensity, while the photocurrent intensity of the metal covalent organic framework is significantly enhanced. Among them, Ni-Pt-ILCOF-1 shows the highest photocurrent density, indicating that the introduction of bimetallic active sites can improve the separation efficiency of electrons and holes.

[0056] Example 2 The application of a Ni-Pt bimetallic covalent organic framework material in the synthesis of H2O2 specifically involves using the Ni-Pt bimetallic covalent organic framework material prepared in Example 1 as a catalyst for the synthesis of H2O2, including the following steps: Five mg of the Ni-Pt bimetallic covalent organic framework material (Ni-Pt-ILCOF-1) prepared in Example 1 was weighed and dispersed in 10 mL of deionized water. The solution was then sonicated to obtain a homogeneous suspension. The resulting suspension was subsequently filtered and loaded onto the surface of a membrane material, and vacuum dried at 80 °C to ensure stable catalyst adhesion. Four identically prepared catalytic membranes were sequentially placed in a flow-through photoreactor, ensuring an effective illumination area of ​​10 × 10 cm. During the reaction, a flow rate of 4.2 mL / min was applied. -1 250 mL of deionized water was circulated through the system at a constant flow rate, completing one overall cycle in approximately 1 hour. During the light-induced reaction, 3 mL samples were periodically taken from the reactor outlet to monitor the concentration of H₂O₂ generated in the system.

[0057] Figure 9 shows the stability test diagram of the Ni-Pt bimetallic covalent organic framework material in Example 2 of the present invention under light irradiation to generate H2O2.

[0058] As shown in Figure 9, the flow-through system based on membrane-supported Ni-Pt-ILCOF-1 exhibits a stable and sustainable H2O2 generation capacity under continuous flow-through operation conditions. This indicates that the Ni-Pt-ILCOF-1 of this invention has good structural stability and photocatalytic durability in the flow-through photoreaction system, can be repeatedly used to synthesize H2O2, and the H2O2 generation rate is very high.

[0059] Example 3 An application of a Ni-Pt bimetallic covalent organic framework material in the removal of odor-causing substances from water specifically involves using the Ni-Pt bimetallic covalent organic framework material prepared in Example 1 as a catalyst to remove geosmin (GSM) and 2-methylisoborneol (2-MIB) from water, including the following steps: First, under visible light irradiation, the Ni-Pt bimetallic covalent organic framework material (Ni-Pt-ILCOF-1) prepared in Example 1 was dispersed in deionized water for photocatalytic reaction, and the H2O2 solution generated by photocatalysis was collected (the final concentration was adjusted to 12 mg·L⁻¹). -1 Subsequently, the H2O2 solution was used to degrade trace amounts of T&O odor pollutants (odor substances). The degradation experiments were conducted under simulated actual operating conditions. The concentration of each component was 100 ng·L⁻¹. -1 GSM and 2-MIB were added to 500L of deionized water, and the resulting treated aqueous solution was passed into a photochemical reactor. The photochemical reactor was a 1.7L stainless steel flow-through reactor with an internal reflective surface structure, equipped with a 65W low-pressure mercury lamp with a primary emission wavelength of 254nm. H2O2 (12 mg·L⁻¹) generated by the Ni-Pt-ILCOF-1 photocatalysis was introduced into the reaction system. -1 The UV irradiation reaction was initiated under dynamic flow conditions. At high flow rates (up to 700 mL / min), the reaction was carried out. -1 The reaction system was run under the following conditions, and samples were taken periodically during the reaction. Sodium thiosulfate was added immediately after each sample to quench the reaction and terminate it.

[0060] Figure 10 This image shows the removal efficiency of the Ni-Pt bimetallic covalent organic framework material (Ni-Pt-ILCOF-1) for geosmin (GSM) and 2-methylisoborneol (2-MIB) in water, as described in Example 3 of this invention. Figure 10It can be seen that, under the synergistic effect of H2O2 generated by Ni-Pt-ILCOF-1 and UV, the removal rates of GSM and 2-MIB both exceed 90%, which is significantly better than the treatment effect of traditional water treatment methods. Among them, the removal rate of GSM and 2-MIB by conventional processes is <20%, indicating that the Ni-Pt bimetallic covalent organic framework material of the present invention has practical application potential in the field of large-scale drinking water purification.

[0061] In summary, compared with conventional metal-modified or single-metal-site-loaded COF materials, the Ni-Pt bimetallic covalent organic framework material (Ni-Pt-ILCOF-1) constructed in this invention exhibits the following significant advantages: (a) In this invention, the covalent organic framework material ILCOF-1 is used as the main framework. By introducing Ni active sites on the surface and within the pores of the framework and anchoring ultradispersed Pt species in situ on the surface, a bimetallic synergistic center with a strong coupling interface is formed. The orbital interaction between Ni and Pt not only broadens the material's response range to visible light but also significantly improves the transition efficiency of photogenerated electrons. This structure significantly suppresses bulk recombination of photogenerated carriers and prolongs the lifetime of electron-hole pairs, enabling Ni-Pt-ILCOF-1 to exhibit higher reaction rates, stronger light absorption capacity, and lower energy loss in photocatalytic reactions, overcoming the key bottlenecks of traditional COFs such as insufficient charge separation efficiency and low visible light utilization.

[0062] (b) In this invention, Ni forms stable metal-ligand bonds with the N / O coordination environment in the COF framework, while Pt species are firmly fixed in the channels or surface sites in an atomically or sub-nanometer ultra-dispersed state, effectively avoiding the metal agglomeration, shedding, or channel blockage problems common in traditional metal-loaded COFs. In particular, the Ni-Pt bimetallic sites maintain a stable configuration under illumination, and are not prone to structural collapse or irreversible valence changes; in continuous operation or cyclic testing, Ni-Pt-ILCOF-1 still maintains high photocatalytic activity, demonstrating good reusability and durability.

[0063] (c) In this invention, by gradually introducing Ni and Pt bimetallic sites and utilizing the electronic conduction channels provided by the covalent organic framework, dynamic charge-proton balance of the material is achieved, giving the material high-density active centers, rapid electron-proton migration capability and stable metal valence state cycling. The resulting Ni-Pt bimetallic covalent organic framework material has excellent photoelectric separation capability, structural stability and catalytic performance, and can be used as a high-performance catalytic material with high application value and broad application prospects.

[0064] (d) In this invention, the porous structure and extended π-conjugated network of the covalent organic framework material ILCof-1 can promote efficient electron-hole migration, Ni 2+ / Ni 3+ The reversible redox reaction of Pt can provide an inherent proton relay. 0 / Pt 2+ The dual-channel electron-hole transport can extend the lifetime of photogenerated electrons. Therefore, under the combined action of ILCof-1, nickel semiconductor, and platinum species, Ni-Pt bimetallic covalent organic framework materials can achieve high efficiency in alkaline media for 2e electron transport. - The oxygen reduction reaction can produce H2O2, breaking through the bottleneck of photocatalytic hydrogen peroxide production under alkaline water.

[0065] Therefore, the Ni-Pt bimetallic covalent organic framework material prepared by this invention has the advantages of bimetallic synergistic and efficient electronic regulation, significantly improved visible light utilization, high active site utilization, excellent photocatalytic efficiency, strong cycle stability, and environmental friendliness. It can be widely used in photocatalytic hydrogen peroxide synthesis, water purification and other fields, and has high practical application value and broad industrialization prospects.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for preparing a Ni-Pt bimetallic covalent organic framework material, characterized in that, Includes the following steps: S1. Preparation of covalent organic framework material ILCOF-1; S2. The covalent organic framework material ILCOF-1 obtained in step S1 is mixed with nickel salt, ground, and heat-treated to complete the in-situ metal coordination and anchoring of nickel, thus obtaining Ni-ILCOF-1. S3. Prepare a dispersion of Ni-ILCOF-1 obtained in step S2, add a platinum salt solution for adsorption, and add NaBH4 solution dropwise for in-situ reduction, so that platinum is anchored on Ni-ILCOF-1 to form a bimetallic synergistic structure, and obtain Ni-Pt bimetallic covalent organic framework material.

2. The preparation method according to claim 1, characterized in that, In step S1, the preparation method of the covalent organic framework material ILCOF-1 includes the following steps: S1-1. Mix aromatic polyaldehyde monomers, amine monomers and mixed solvents, disperse by ultrasonication, add acidic catalyst during ultrasonic dispersion to obtain a mixed solution; S1-2. The mixture obtained in step S1-1 is subjected to a freezing-vacuuming-nitrogen filling cycle to obtain a precursor solution; S1-3. The precursor solution obtained in step S1-2 is subjected to a solvothermal reaction to obtain the covalent organic framework material ILCOF-1.

3. The preparation method according to claim 2, characterized in that, The preparation method of the covalent organic framework material ILCOF-1 satisfies at least one of the following conditions; (1.1) In step S1-1, the molar ratio of the aromatic polyaldehyde monomer and the amine monomer is 1:1 to 2; (1.2) In step S1-1, the aromatic polyaldehyde monomer is TFPPy; the amine monomer is at least one of p-phenylenediamine, 4,4'-diaminobiphenyl, and 4,4'-diaminoazobenzene; (1.3) In step S1-1, the mixed solvent is a mixture of o-dichlorobenzene and n-butanol; the volume ratio of o-dichlorobenzene to n-butanol is 1:1; (1.4) In step S1-1, the process conditions for ultrasonic dispersion are: power of 150 W to 300 W, temperature ≤ 35℃, and time of 5 min to 20 min; (1.5) In step S1-1, the mass-to-volume ratio of the aromatic polyaldehyde monomer to the acidic catalyst is 40 mg: 200 μL; the acidic catalyst is an acetic acid solution; the concentration of the acetic acid solution is 6 M; (1.6) In step S1-2, the freezing-vacuuming-nitrogen filling cycle is performed at least 3 times; (1.7) In steps S1-3, the temperature of the solvothermal reaction is 100 ℃~150 ℃; the time of the solvothermal reaction is 48 h~96 h; (1.8) In step S1-3, after the solvothermal reaction is completed, the product is subjected to Soxhlet extraction or continuous flow washing with acetone, methanol and ethanol in sequence, and dried at a temperature of 60 ℃~100 ℃ for 8 h~24 h to obtain covalent organic framework material ILCOF-1.

4. The preparation method according to any one of claims 1 to 3, characterized in that, In step S2, the mass ratio of the covalent organic framework material ILCOF-1 to the nickel salt is 2:0.5 to 2; the nickel salt is nickel acetylacetonate; the heating rate during the heat treatment is 2℃ / min to 5℃ / min; the heat treatment temperature is 20℃ to 200℃; and the heat treatment time is 2 h to 6 h.

5. The preparation method according to claim 4, characterized in that, In step S3, the dispersion is prepared by dispersing Ni-ILCOF-1 in water; the mass-to-volume ratio of Ni-ILCOF-1 to water is 20 mg:100 mL; the volume ratio of the dispersion to the platinum salt solution is 100:0.4; the platinum salt solution is a chloroplatinic acid solution; and the concentration of the chloroplatinic acid solution is 0.3 mg·mL. -1 ~1 mg·mL -1 The adsorption time is 0.5 h to 2 h; the volume ratio of the dispersion to the NaBH4 solution is 100:0.4; the concentration of the NaBH4 solution is 1 mg / mL to 2 mg / mL; and the in-situ reduction time is 2 h to 5 h.

6. A Ni-Pt bimetallic covalent organic framework material, characterized in that, It is prepared by any one of claims 1 to 5.

7. The Ni-Pt bimetallic covalent organic framework material according to claim 6, characterized in that, The Ni-Pt bimetallic covalent organic framework material comprises a covalent organic framework material ILCOF-1, a Ni semiconductor, and Pt species. The Ni semiconductor is distributed on the surface of the covalent organic framework ILCOF-1 through coordination fixation and thermo-solid phase embedding to form Ni-ILCOF-1. The Pt species are distributed on the surface of the Ni-ILCOF-1 in an atomic or sub-nanometer dispersed form. A portion of the Pt species is fixed in the local channel region of the covalent organic framework ILCOF-1 and is distributed hierarchically around the Ni semiconductor to form a heterojunction electronic structure. The Ni semiconductor is β-Ni(OH)2 and NiOOH. The Pt species is zero-valent platinum and platinum oxide.

8. The Ni-Pt bimetallic covalent organic framework material according to claim 7, characterized in that, The Ni-Pt bimetallic covalent organic framework material contains 1.5 wt% to 2.0 wt% Ni and 0.8 wt% to 2 wt% Pt.

9. The application of a Ni-Pt bimetallic covalent organic framework material as described in any one of claims 6 to 8 in the synthesis of H2O2.

10. The application of a Ni-Pt bimetallic covalent organic framework material as described in any one of claims 6 to 8 in the removal of odor substances from water.

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