Metal-based substance with core-shell structure as well as preparation method and application of metal-based substance

Abstract

The invention belongs to the field of inorganic materials, and particularly relates to a metal-based substance with a core-shell structure and a preparation method and application thereof. According to the invention, salicylaldehyde and TAPT are adopted as raw materials to carry out amine-aldehyde condensation reaction and metal salt is added to obtain a metal-SOF precursor, and then the metal-based substance with the core-shell structure is prepared through pyrolysis. The metal-based substance with the core-shell structure can be used as a catalyst for a reverse water gas shift reaction of carbon dioxide, and has relatively high CO2 conversion rate and CO selectivity.

Description

Technical Field

[0001] This invention belongs to the field of inorganic materials, specifically relating to a metal-based material with a core-shell structure, its preparation method, and its application. Background Technology

[0002] The reverse water-gas shift (RWGS) reaction, which involves the hydrogenation of CO2 to produce carbon monoxide (CO), is of great significance. CO is not only an important component of the syngas system but also a key feedstock for the production of clean fuels and high-value-added chemicals through Fischer-Tropsch synthesis (FTS). In particular, combined with green hydrogen produced from renewable energy sources, RWGS provides a highly promising route for clean energy conversion and carbon resource utilization.

[0003] However, the CO2 hydrogenation reaction network is complex, and CO formation is often accompanied by the production of methane (CH4) as a byproduct. Although CH4 has certain utilization value, its separation process is energy-intensive. Therefore, how to effectively control the product selectivity is a core scientific problem in catalyst design. Existing research shows that CO2 hydrogenation is a structure-sensitive reaction, and the crystal structure, particle size effect, metal-support interaction, and intrinsic properties of the active metal all significantly affect the product distribution.

[0004] Currently, noble metals (such as Pt-based catalysts) have made significant progress in improving CO selectivity, but their high cost limits their large-scale application. In contrast, the non-noble metal cobalt (Co) has attracted much attention due to its excellent CO dissociation and C–C coupling capabilities. However, traditional Co-based catalysts (such as Co / ZrO2, Co / TiO2, and Co / CeO2) typically exhibit high CH4 selectivity, which to some extent restricts their application in highly selective RWGS reactions.

[0005] It is worth noting that the RWGS reaction is an endothermic process, and CO2 conversion at low temperatures is subject to both thermodynamic and kinetic limitations. Both theoretical and experimental results show that active metal clusters can effectively dissociate H2, while oxygen vacancies contribute to CO2 activation. Therefore, constructing specific metal-oxygen vacancy synergistic active sites in the catalyst is considered an effective strategy to enhance the activity of low-temperature RWGS. Against this backdrop, this invention designs and prepares a core-shell structured M@MOx-C catalyst using a metal-salophen organic framework (metal-SOF, i.e., M-SOF) as a precursor. Summary of the Invention

[0006] The first technical problem to be solved by this invention is to provide a method for preparing a metal-based material with a core-shell structure. This method includes the following steps: [The method involves...] The metal-SOF precursor is obtained by amine-aldehyde condensation with 1,3,5-tris(4-aminophenyl)triazine, followed by the addition of a metal salt. The metal-SOF precursor is then pyrolyzed under a hydrogen atmosphere. R1, R2, R3, and R4 are each independently H or C. 1-4 alkyl.

[0007] Preferably, in the above method, R1, R2, R3 and R4 are all H.

[0008] Preferably, in the above method, R1, R2, R3 and R4 are each independently selected from H, methyl, ethyl, n-propyl, isopropyl and tert-butyl.

[0009] Preferably, in the above method, The molar ratio with 1,3,5-tris(4-aminophenyl)triazine (TAPT) is 0.2:1 to 6:1. Preferably, it is 3:1.

[0010] Preferably, in the above method, the temperature of the amine-aldehyde condensation reaction is room temperature (25°C) to 120°C. The time of the amine-aldehyde condensation reaction is 0.5-2 hours.

[0011] Preferably, in the above method, the solvent used in the amine-aldehyde condensation reaction is at least one selected from N,N-dimethylformamide, mesitylene, 1,4-dioxane, o-dichlorobenzene, or n-butanol. N,N-dimethylformamide is preferred.

[0012] Specifically, in the above method, the metal salt is an acetate of a metal. The metal is selected from one or more of cobalt, nickel, iron, and manganese. For example, the cobalt is Co(OAc)₂·4H₂O. The nickel is Ni(OAc)₂·4H₂O. The iron is Fe(OAc)₂·4H₂O. The manganese is Mn(OAc)₂·4H₂O. Cobalt is preferred.

[0013] Preferably, in the above method, the amount of metal salt added is 0.5-5 times the molar amount of TAPT. Preferably, it is 1.5 times. This is calculated based on the molar amount of the metal in the metal salt.

[0014] Specifically, in the above method, the reaction temperature after adding the metal salt is 90-150℃, and the reaction time is 12-36 hours.

[0015] Preferably, in the above method, the amine-aldehyde condensation reaction is carried out under an inert atmosphere, such as a nitrogen atmosphere.

[0016] Preferably, in the above method, the reaction after adding the metal salt is carried out under an inert atmosphere, such as a nitrogen atmosphere.

[0017] Specifically, in the above method, the pyrolysis temperature is 500-600℃, and the pyrolysis time is 1-10 hours.

[0018] The second technical problem to be solved by the present invention is to provide a metal-based material with a core-shell structure prepared by the above preparation method.

[0019] Furthermore, the present invention provides a Co-based material with a core-shell structure prepared by the above preparation method.

[0020] The third technical problem to be solved by the present invention is to provide the use of the above-mentioned metal-based or Co-based materials with core-shell structure as catalysts in the carbon dioxide reverse water gas shift reaction.

[0021] Beneficial effects of this invention:

[0022] This invention utilizes a metal-SOF organic framework with a unique coordination structure as a precursor, which promotes the formation of a surface shell oxide layer. High-temperature pyrolysis of this precursor in a hydrogen atmosphere achieves coupling between high-defect sites (metal oxide layer) and the core-shell structure. These two elements synergistically catalyze the dissociation and adsorption of CO2 and H2 reactants. By employing this core-shell structure as a catalyst, this invention provides reaction sites at the interface between the metal core and metal oxide shell in the countercurrent gas reaction. Furthermore, the CO product migrates to the saturated metal sites in the shell, promoting its desorption, thereby achieving high selectivity for CO and high countercurrent gas efficiency.

[0023] Furthermore, this invention prepares a unique core-shell structure Co@CoO from a Co-salophen (Co-SOF) organic framework precursor. x -C catalyst. In-situ characterization shows that CoO x The shell undergoes dynamic reconstruction during the reaction, enhancing CO2 adsorption and activation, while the metallic Co core promotes hydrogen spillover. CoO x The strong synergistic effect between the shell and the Co core enables highly efficient RWGS catalytic performance at 500 ppm. o Under C conditions, it exhibited 254 mmol CO·g cat ‒1 ·h ‒1 The generation rate and near 100% selectivity indicate that Co@CoO x -C is a robust and efficient CO2 conversion catalyst, highlighting the potential of SOF-derived defect-rich core-shell structures in designing next-generation heterogeneous catalysts suitable for a variety of reaction processes, including RWGS and Fischer-Tropsch synthesis. Attached Figure Description

[0024] Figure 1 Co@CoOx A schematic diagram illustrating the mechanism of the preparation processes of -C and Co-C;

[0025] Figure 2 Structural characterization of the catalyst, wherein a) Co@CoO x XRD patterns of -C and Co-C; b) Co@CoO x Raman spectra of -C and Co-C;

[0026] X-ray diffraction (XRD) pattern shows Co@CoO x -C exhibits good crystallinity, and its structure completely corresponds to that of cubic metallic Co (PDF#15-0806), and it grows along the (111), (200), and (220) crystal planes. Figure 2 a). Furthermore, the characteristic peaks in the Raman spectrum correspond to the Eo of the Co-O bond. g F 2g and A 1g Pattern related ( Figure 2 b). A 1g and F 1 2g The frequency bands can be respectively attributed to Co 3+ -O 2- and Co 2+ -O 2- The vibration. E g and F 2 2g The bands are respectively assigned to CoO6 octahedral sites and CoO4 tetrahedral sites in the Co3O4 lattice. Compared with the Co-O bonds on the Co-C surface excited by Raman laser, Co@CoO x -C of A 1g Peak (690 to 678 cm) -1 ) and E g Peak (479 to 470 cm) -1 The redshift and significant decrease in intensity indicate that Co@CoO x -C contains certain oxygen vacancies, exhibiting characteristics of disorder and incomplete coordination.

[0027] Figure 3 Co@CoO x Surface atomic structure analysis of -C catalyst, a) from Co@CoO x -C HAADF-TEM image of pseudo-color image; b) Co@CoO x -C HAADF-STEM image; c) Co@CoO x d) High-resolution TEM image of C; EDX images of C, N, Co and O.

[0028] Characterization of Co@CoO3 using high-resolution transmission electron microscopy (HRTEM) x Morphology and microstructure of -C catalysts. Figure 3 The HRTEM image in a shows Co@CoO x -C catalysts exhibit a core-shell structure. For example... Figure 3 As shown in b, Co@CoO x HRTEM images of -C show that it has a face-centered cubic (fcc) structure, and the d-interval value of 0.202 nm matches well with the atomic configuration of Co along the {111} plane. However, its surface region has lattice fringe spacings of Co3O4 {311} plane (d = 0.244 nm), Co3O4 {220} plane (d = 0.285 nm), and Co3O4 {222} plane (d = 0.226 nm), indicating that CoO x The atomic arrangement characteristics of Co@CoO. x -High-resolution elemental mapping analysis was performed on C to confirm the atomic distribution within the catalyst. Elemental mapping using electron energy loss spectroscopy (EELS) revealed the composition of Co@CoO. x -C nanoparticle chemical distribution ( Figure 3 c, d). For example... Figure 3 As shown in c and d, Co, C, and N elements are uniformly distributed, while O element is enriched near the particle surface, with a thickness of approximately 2.6–4 nm. These observations clearly confirm that the catalyst forms a distinct Co@CoO group. x The core-shell structure.

[0029] Figure 4 Electronic state and coordination structure analysis; Co@CoO x XPS spectra of -C and Co-C a) Co 2p and b) O 1s; c) Co@CoO x -C, Co foil, and the Co K-edge XANES spectra of the control samples CoO and Co2O3; d) Co@CoO x - Fourier transform k3-weighted EXAFS spectra of C, Co foil, and control samples CoO and Co2O3; e) Co@CoO x The fitted curve of the Co K-side k3 weighted Fourier transform EXAFS spectrum of -C, with the inset showing the corresponding Co@CoO x -C structure schematic model; blue spheres represent cobalt atoms; f) Co@CoO x g) Wavelet transform image of Co K edge of -C, g) Wavelet transform image of Co K edge of Co foil, and h) Wavelet transform image of Co K edge of contrast sample Co2O3;

[0030] Co@CoOx Electronic structure characterization and analysis of -C

[0031] Through Co@CoO x X-ray photoelectron spectroscopy (XPS) was used to characterize -C in detail, providing atomic structure and quantitative elemental analysis. For example... Figure 4 As shown in figure a, there are two peaks at 780.02±0.6 eV and 781.8±0.6 eV in the high-resolution Co 2p spectrum, which are attributed to CoO, respectively. x Co 3+ and Co 2+ Ionic configuration. The binding energy of metallic Co is 778.0 ± 0.6 eV, Co 2p 3 / 2 Peak and Co 2p 1 / 2 The energy difference between the peaks is approximately 15 eV. These two smaller peaks are ~786.60 eV and ~803.32 eV, respectively, and are Co@CoO₂ x -C of Co 0 The satellite vibration peak. It is worth noting that Co@CoO x -C's surface is mainly composed of abundant Co. 2+ and Co 3+ Species and a small amount of metal Co 0 Composition. However, under high-energy X-ray irradiation, high-valence Co was also observed on the surface of metallic Co. 2+ and Co 3+ The corresponding signal may be due to surface oxidation or excitation-induced effects. For Co@CoO x -C O1s XPS spectrum ( Figure 4 b), at 529.9 eV, lattice oxygen (O) was observed. L The peak value is typically attributed to the metal oxide state of oxygen, i.e., oxygen reacts with Co to form a stable oxide (CoO). x This result is consistent with the conclusions reached by HRTEM. On the other hand, the peaks observed at 532.1 eV and 533.9 eV are attributed to oxygen vacancies (O₂, O₂, O₃ ... v ) and hydrogen and oxygen (O OH The characteristic peak of ) is shown. In the semi-quantitative analysis of O 1s XPS, the peak area ratio of the oxygen vacancy peak Co@CoOx (73.2%) is higher than that of Co (63.6%), indicating that Co@CoO x -C surfaces contain more oxygen defects.

[0032] To further explore Co@CoO xThe coordination environment of the Co site in -C was analyzed, and X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra of the Co K edge were collected. The normalized XANES curves of the Co@CoO edge were used to examine the Co@CoO coordination environment. x -C is almost the same as Co foil ( Figure 4 c). The Fourier transform (FT) and fitting parameters of the Co K-side EXAFS spectrum reveal the Co@CoO x A prominent peak of -C at 2.17 Å is attributed to the Co-Co coordination structure ( Figure 4 de). like Figure 4 As shown in fh, compared with Co foil and Co2O3, Co@CoO x -C is only at about 2.2 Å -1 The highest strength is found at this location, which corresponds to the Co-Co bond, further proving the existence of Co@CoO. x -C is composed of Co atom clusters, with an ultrathin layer of amorphous CoO on the surface. x The results are consistent with the XPS results above.

[0033] Figure 5 Evaluation of carbon dioxide reduction catalytic performance; a) Co@CoO x CO2 conversion rates of -C and Co-C at different temperatures and b) Co@CoO x -C and Co-C CO selectivity at different temperatures; c) Co@CoO x -C and Co-C under different WHSVs (CO2:H2=1:3), 400 o CO2 conversion rate at C; d) Co@CoO x CO2 hydrogenation cycle stability of -C (WHSV = 300,000 mlg) cat -1 h -1 Temperature range: 200-500 o C); e) CO yield comparison: Co@CoO x -C and recently reported advanced catalysts: Catalysts: (In2O3), (Ni-P-8.7), (Ni@S-1-red), (Ni / C-In2O3), (3%Co-NC), (Pd1-FeO) x SAC), (10Ni-5In-CeO), (Ni-0.15In-CeO2), (CuZr-5), (Ni-in-Cu) and (Pt cluster / PN-CeO2);

[0034] Co@CoO x Performance of -C in RWGS

[0035] Co@CoO was evaluated x Catalytic efficiency of CO2 hydrogenation in RWGS reaction with -C and Co-C at various weight space-time velocities (WHSV) in a fixed-bed reactor. Figure 5 ab shows the temperature-dependent CO2 conversion of the catalyst of this invention. The Co-C catalyst exhibits poor catalytic activity at 400°C. o The conversion rate at time C was only 0.9%, and at 500 o C is 2%, while Co@CoO x -C catalyst at 500 o At C, at 60000 mL g cat -1 h -1 It exhibited a high CO2 conversion rate of 28.9% at WHSV (CO2 conversion rate refers to the percentage of converted CO2 relative to the initial CO2), which is 14 times that of Co-C catalysts. Furthermore, Co@CoO... x The -C catalyst maintained nearly 100% CO selectivity (CO selectivity refers to the ratio of CO yield to total product yield) at all test temperatures. Co@CoO was tested. x -C and Co-C are catalysts for different WHSVs in the RWGS reaction ( Figure 5 c). Co@CoO under different WHSV conditions x The CO2 conversion rate of -C exceeded that of Co-C, especially under extremely high WHSV conditions (WHSV = 300,000 ml g). cat -1 h -1 Co-C catalyst at 400 o The CO2 conversion rate at C is only 0.4%, while Co@CoO x The CO2 conversion rate of the -C catalyst is 5.9%, which is more than 10 times that of the Co-C catalyst.

[0036] To verify Co@CoO x The high-temperature stability of -C was tested through cycling tests within a high-temperature range. For example... Figure 5 As shown in d, Co@CoO x -C at 300,000 ml g cat -1 h -1 At high WHSV, the CO yield did not decrease in five consecutive cycles, demonstrating its excellent reusability at high temperatures. Figure 5This paper summarizes and compares the catalytic performance of various catalysts reported in the literature for RWGS reactions, including Co-based catalysts, supported non-noble metal catalysts, and supported noble metal catalysts. In comparison, Co@CoO x The CO yield of -C is approximately 254 mmol g. cat -1 h -1 It is even higher than some precious metal-based catalysts.

[0037] Figure 6 SEM images of the Co-SOF precursor at different scales in Example 1;

[0038] Figure 7 TEM images of the Co-SOF precursor at different scales in Example 1; Figure 6 Scanning electron microscope (SEM) and Figure 7 Transmission electron microscopy (TEM) imaging revealed that Co-SOF is composed of stacked nanosheets.

[0039] Figure 8 SEM images of Ni-SOF at different scales in Example 1; Scanning electron microscopy (SEM) imaging shows that Ni-SOF is composed of irregularly stacked small particles.

[0040] Figure 9 SEM images of Fe-SOF at different scales in Example 1; Scanning electron microscopy (SEM) imaging shows that the morphology of Fe-SOF is similar to that of Ni-SOF, consisting of irregularly stacked small particles.

[0041] Figure 10 Co in Example 1 0.2 Mn 0.8 - SOF SEM images at different scales;

[0042] Figure 11 Co in Example 1 0.4 Mn 0.6 -SEM images of SOF at different scales; Scanning electron microscopy (SEM) imaging shows Co at different Co / Mn ratios. x Mn y -SOFs have similar morphologies, both exhibiting a blocky structure composed of small particles and stacked flakes.

[0043] Figure 12 Co-SOF and Co in Example 1 0.2 Mn 0.8 -SOF, Co 0.4 Mn 0.6XRD spectra of Co-SOF, Ni-SOF, and Fe-SOF; XRD spectra show that Co-SOF and Co... 0.2 Mn 0.8 -SOF, Co 0.4 Mn 0.6 -SOF, Ni-SOF, and Fe-SOF all exhibited good crystallinity, indicating the successful synthesis of a series of ordered metal framework polymers and demonstrating the versatility of the synthesis method.

[0044] Figure 13 Co@CoO in Example 1 x -C SEM images at different scales;

[0045] Figure 14 Co@CoO in Example 1 x -C TEM images at different scales; Figure 13 Scanning electron microscope (SEM) and Figure 14 Transmission electron microscopy (TEM) imaging shows that Co@CoO x -C exhibits a distinct core-shell structure in its particle morphology. This geometric structure is of significant value for catalytic applications, effectively exposing internal active sites while simultaneously realizing the synergistic effect of the core-shell structure within RWGS.

[0046] Figure 15 TEM image of Co-C in the control group of Example 1;

[0047] Figure 16 Mapping image of Co-C in the control group of Example 1; transmission electron microscopy (TEM) imaging and energy-dispersive X-ray spectroscopy (EDS) analysis showed that the Co-C catalyst was composed of nanoparticles. Figure 15 Nitrogen, oxygen, and cobalt elements are evenly distributed. Figure 16 ).

[0048] Figure 17 Evaluation of the catalytic performance of carbon dioxide reduction: Co-SOF was annealed at high temperature in an H2 atmosphere, and different annealing temperatures and times were explored. The samples were named according to the annealing temperature and time; for example, 500H2-1H refers to Co-SOF annealed at 500℃ for 1 hour in an H2 atmosphere. The following data were used to evaluate the CO2 conversion and CO selectivity of three materials annealed at 500℃: a) CO2 conversion rate and b) CO selectivity. The following data were used to evaluate the CO2 conversion and d) CO selectivity of three materials annealed at 600℃. Figure 17The temperature-dependent CO2 conversion of the catalysts of this invention is shown. It can be seen that after annealing Co-SOF at 500℃, all three catalysts exhibited high CO selectivity at high temperatures and high CO2 conversion rates at low temperatures. In contrast, after annealing Co-SOF at 600℃, its CO selectivity significantly improved. Furthermore, after annealing for 6 hours and 10 hours, the CO selectivity was close to 100% at 200-500℃. In addition, after annealing Co-SOF at 600℃ for different times, its CO2 conversion rate at high temperatures showed a significant improvement. This indicates that high-temperature annealing of Co-SOF under a H2 atmosphere can prepare CO2 reduction active catalysts. Detailed Implementation

[0049] The present invention firstly (e.g., salicylaldehyde) and 1,3,5-tris(4-aminophenyl)triazine (TAPT) undergo an amine-aldehyde condensation reaction in an organic solvent to form an ordered intermediate; subsequently, a metal salt (e.g., acetate, metals such as Co, Fe, Ni, Mn) is added under high temperature conditions of 90-150℃ to form an extended coordination polymer M-SOF (e.g., Co-SOF) with M-N2O2 (M represents a metal, e.g., Co-N2O2) nodes; then, the precursor is pyrolyzed in a hydrogen atmosphere at 500-600℃ to obtain a unique defective M@MO through a hydrogen-rich high-reducing atmosphere. x -C (e.g., Co@CoO) x -C) Core-shell structured catalyst; during pyrolysis, highly coordinated metals (e.g., Co) are gradually reduced, forming a core-shell structure with metal (e.g., Co) inside and defect-type MO on the surface. x (e.g., CoO) x ) has a unique structure.

[0050] This invention, through in-situ characterization and theoretical calculations, reveals that in the defect-rich Co@CoOx core-shell structure, the metallic Co core can promote efficient hydrogen overflow, while the metastable CoO... x The shell effectively adsorbs and activates CO2. The synergistic effect between the core and shell significantly enhances the reverse water-gas shift (RWGS) reaction activity, achieving 254 mmol g. cat -1 h -1 The system exhibits high CO yield and near 100% CO selectivity. Further mechanistic studies revealed that the system follows a redox pathway, thus explaining its excellent selectivity and stability under high-temperature conditions.

[0051] All chemicals and solvents used in the embodiments of this invention were purchased from commercial sources.

[0052] Example 1

[0053] Synthesis of Co-SOF: TAPT (212.4 mg, 0.6 mmol) and salicylaldehyde (188 μL, 1.8 mmol) were dissolved in 20 mL of DMF. After stirring for 30 minutes under nitrogen protection, Co(OAc)₂·4H₂O (224 mg, 0.9 mmol) was added to the solution. The mixture was stirred continuously at 100 °C for 24 hours under nitrogen protection. After cooling to room temperature, the precipitate was collected by centrifugation, thoroughly washed with DMF, ethanol, and water, and freeze-dried to obtain a red powder.

[0054] This method for synthesizing metal-SOF is versatile. Under the same conditions, other samples with different metal centers (Ni-SOF, Fe-SOF, and Co) were synthesized by adding corresponding metal salts (e.g., Ni(OAc)₂·4H₂O, Fe(OAc)₂·4H₂O, and different proportions of Co(OAc)₂·4H₂O and Mn(OAc)₂·4H₂O). x Mn y -SOF).

[0055] Ni-SOF, Fe-SOF, Co x Mn y -SOF: The synthesis method is similar, except that the corresponding metal salt is used instead of Co(OAc)2·4H2O.

[0056] Co 0.2 Mn 0.8 -SOF: The molar ratio of reactants Co(OAc)₂·4H₂O to Mn(OAc)₂·4H₂O was controlled at 0.2:0.8. The reaction process involved dissolving TAPT (212.4 mg, 0.6 mmol) and salicylaldehyde (188 μL, 1.8 mmol) in 20 mL of DMF. After stirring under nitrogen protection for 30 minutes, Co(OAc)₂·4H₂O (44.835 mg, 0.18 mmol) and Mn(OAc)₂·4H₂O (176.4648 mg, 0.72 mmol) were added to the solution. The mixture was stirred continuously at 100°C for 24 hours under nitrogen protection. After cooling to room temperature, the precipitate was collected by centrifugation, thoroughly washed with DMF, ethanol, and water, and then freeze-dried.

[0057] Co 0.4 Mn 0.6-SOF: The molar ratio of reactants Co(OAc)₂·4H₂O to Mn(OAc)₂·4H₂O was controlled at 0.4:0.6. The reaction process involved dissolving TAPT (212.4 mg, 0.6 mmol) and salicylaldehyde (188 μL, 1.8 mmol) in 20 mL of DMF. After stirring under nitrogen protection for 30 minutes, Co(OAc)₂·4H₂O (89.67 mg, 0.36 mmol) and Mn(OAc)₂·4H₂O (132.35 mg, 0.54 mmol) were added to the solution. The mixture was stirred continuously at 100°C for 24 hours under nitrogen protection. After cooling to room temperature, the precipitate was collected by centrifugation, thoroughly washed with DMF, ethanol, and water, and then freeze-dried.

[0058] Co@CoO x Synthesis of -C: The final experimental sample, named Co@CoO, was obtained by carbonizing the Co-SOF precursor at 600 °C for 6 hours in an H2 atmosphere. x -C.

[0059] Synthesis of Co-C: The obtained Co-SOF precursor was subjected to an Ar atmosphere at 600°C. o Carbonized at C for 6 hours. The carbonized sample served as the final control sample and was named Co-C.

[0060] Material characterization

[0061] Scanning electron microscopy (SEM) images were obtained using a Hitachi Regulus 8220 (Japan) at 5 kV and a collection angle of 48 mrad. SEM samples were prepared by directly attaching catalyst powder to a conductive carbon binder on an aluminum sample holder. Transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) were performed on a Talos F200X S / TEM microscope (FEI Ltd., USA) with a maximum convergence angle ≥100 mrad, a 4k×4k Ceta CMOS camera at 200 kV, coupled with a Thermo Scientific Super-X™ patented integrated EDS system featuring four independent silicon drift detectors (SDDs) and a solid angle of 0.9 srad. HRTEM images were analyzed using GMS free software. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADFSTEM) was performed at 300 kV on a dual-corrected Thermo Fisher Scientific Spectroscopy 300 microscope with a cold field emission gun. The microscope was equipped with Super-X windowless EDS (4-quadrant SDD EDS detection; solid angle >0.7 srad) for elemental mapping. TEM, HRTEM, and AC-HAADF-STEM samples were prepared by ultrasonically dispersing catalyst powder in ethanol and then drop-coating it onto an ultrathin copper grid. Crystal structures were analyzed by X-ray diffraction (XRD, DX-2700BH, Haoyuan Instruments, China) at 40 kV using a multi-purpose X-ray diffractometer with copper radiation. A hemispherical 180° X-ray photoelectron spectroscopy system with a 128-channel detector was used on the K-Alpha™+ X-ray photoelectron spectroscopy system (Thermo Scientific). o X-ray photoelectron spectroscopy (XPS) measurements were performed using a bifocal analyzer and monochromatic Al Kα irradiation. XPS results were analyzed using the software "Avantage" and "Smart background" to calculate high-resolution C 1s, N 1s, O 1s, and Co 2p spectra for atomic and weight ratios. For peak fitting, a singlet was used for the 1s orbital and a doublet for the 2p orbital.

Claims

1. A method for preparing a metal-based material with a core-shell structure, characterized in that: Includes the following steps: Will The metal-SOF precursor is obtained by amine-aldehyde condensation with 1,3,5-tris(4-aminophenyl)triazine, followed by the addition of a metal salt. The metal-SOF precursor is then pyrolyzed under a hydrogen atmosphere. R1, R2, R3, and R4 are each independently H or C. 1-4 alkyl.

2. The method according to claim 1, characterized in that: R1, R2, R3, and R4 are all H.

3. The method according to claim 1 or 2, characterized in that: The molar ratio of the triazine to 1,3,5-tris(4-aminophenyl)triazine is 0.2:1 to 6:1; preferably 3:

1.

4. The method according to any one of claims 1-3, characterized in that: The temperature of the amine-aldehyde condensation reaction is room temperature - 120°C; the time of the amine-aldehyde condensation reaction is 0.5-2 h; further, the solvent used in the amine-aldehyde condensation reaction is at least one of N,N-dimethylformamide, mesitylene, 1,4-dioxane, o-dichlorobenzene or n-butanol; preferably N,N-dimethylformamide.

5. The method according to any one of claims 1-4, characterized in that: The metal salt is an acetate of a metal; the metal is selected from one or more of cobalt, nickel, iron and manganese; preferably cobalt; preferably, the amount of the metal salt added is 0.5-5 times the molar amount of TAPT; more preferably 1.5 times.

6. The method according to any one of claims 1-5, characterized in that: The reaction temperature after adding the metal salt is 90-150℃; the reaction time is 12-36h.

7. The method according to any one of claims 1-6, characterized in that: The pyrolysis temperature is 500-600℃; the pyrolysis time is 1-10h.

8. A metal-based material with a core-shell structure prepared by the preparation method according to any one of claims 1-7.

9. The metal-based material with a core-shell structure according to claim 8, characterized in that: The metal is Co.

10. The use of the metal-based material with a core-shell structure as described in claim 8 or the Co-based material with a core-shell structure as described in claim 9 as a catalyst in the carbon dioxide reverse water gas shift reaction.

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