A method for preparing a fluorine-doped high-loading metal monatomic catalyst

Abstract

The application discloses a method for preparing a fluorine-doped high-load metal monatomic catalyst by using a polymer anchoring strategy, and belongs to the technical field of catalyst preparation. The method adopts a ball milling process, a large number of metal ions are anchored by sequentially introducing a fluorinated polymer precursor and a nitrogen source, and the target catalyst is obtained after one-step calcination. The synthesis route is short, the operation is convenient, the period is short, the cost is low, and the method is green and environment-friendly. The obtained material has high metal load and atomic dispersion characteristics, and a fluorine atom coordination structure is formed at the metal site, and the catalyst has excellent catalytic performance, and can be widely applied to the fields of environmental remediation, organic synthesis and energy catalysis. The application provides a new technical path for the structural design and controllable synthesis of high-load monatomic catalysts.

Description

Technical Field

[0001] This invention relates to a method for preparing catalysts, specifically to a method for preparing fluorine-doped, highly loaded metal single-atom catalysts using a polymer anchoring strategy. Background Technology

[0002] Single-atom catalysts (SACs) have attracted widespread attention in the field of catalysis due to their unique high atom utilization efficiency and flexible tunable electronic structure. Among the many SACs, the addition of axial ligands can alter the coordination environment and electronic structure of the central atom, providing new solutions for the fine-tuning of the SAC's electronic structure. Fluorine atoms, as a typical axial ligand, can change the electron distribution of the metal center and adjust the d-band center position; simultaneously, their strong electron-withdrawing effect can enhance the positive charge of the metal, optimize the adsorption strength of reaction intermediates, and improve catalytic activity. Furthermore, the axial coordination structure can further stabilize the single atom, prevent aggregation, and improve the cycling stability of the material.

[0003] However, preparing single-atom catalysts with high metal loading and axial coordination of fluorine atoms remains a significant challenge. Traditional methods such as high-temperature pyrolysis and wet chemical synthesis struggle to simultaneously achieve high-density, uniform dispersion of metal atoms on the support and precise construction of the fluorine-doped structure. While isolated single atoms can be obtained under low metal loading conditions, the overall catalytic activity is insufficient; conversely, increasing the loading level leads to the migration and aggregation of metal atoms into nanoparticles, resulting in the loss of single-atom catalytic characteristics. Furthermore, the pre-designed fluorine-doped structure is prone to dissociation during subsequent heat treatment and catalytic reactions, making it difficult to maintain stability.

[0004] To address the shortcomings of existing technologies, researchers have developed various single-atom stabilization modification strategies, among which polymer-assisted anchoring and regulation schemes offer unique advantages over other methods. Polymers rich in nitrogen and oxygen coordination atoms, such as polydopamine and polyethyleneimine, can interact strongly with metal precursors through molecular functional groups, binding the migration behavior of metal atoms during pyrolysis, which is beneficial for generating and stabilizing single-atom sites. However, how to accurately introduce fluorine ligands into metal atoms and supports while maintaining ligand stability, and construct N4-MF coordination structures with clear structures and excellent stability, while achieving high metal loading, remains a key technical challenge that urgently needs to be overcome in this field. Summary of the Invention

[0005] To address the problems of existing preparation techniques, this invention aims to provide a preparation method based on a polymer anchoring strategy to overcome the shortcomings of the prior art. This strategy can uniformly and densely anchor metal precursors onto the catalyst surface, and through controllable heat treatment technology, simultaneously obtain highly loaded single-atom materials and construct and stabilize the fluorine-doped structure of the metal sites, providing a new approach for the synthesis and design of high-performance single-atom catalysts.

[0006] A method for preparing fluorine-doped highly supported metal single-atom catalysts using a polymer anchoring strategy, characterized by comprising the following steps:

[0007] (1) Polylysine, heptafluorobutyric anhydride and triethylamine were dissolved in an organic solvent and dried to obtain fluorinated polylysine;

[0008] (2) Mix the fluorinated polylysine, nitrogen source, hydrogen peroxide and metal fluoride obtained in step (1) evenly, and transfer the above mixture into a ball mill jar for ball milling to obtain a polymer copolymer metal composite precursor.

[0009] (3) The polymer copolymer metal composite precursor obtained in step (2) is transferred to a ceramic boat and calcined at high temperature under inert gas protection in a tube furnace. It is then naturally cooled to room temperature to obtain a fluorine-doped high-load metal single-atom catalyst.

[0010] Preferably, the organic solvent in step (1) is one of methanol, ethanol, ethyl acetate, or dimethyl sulfoxide.

[0011] Preferably, the metal fluoride mentioned in step (2) is one of iron fluoride, copper fluoride, cobalt fluoride, chromium fluoride, nickel fluoride, aluminum fluoride, or zinc fluoride.

[0012] Preferably, the nitrogen source in step (2) is one of 3,4-dihydroxyphenylpropionic acid, dopamine hydrochloride, levodopa, catechol, dicyandiamide, polyethyleneimine, urea, melamine, triethylenediamine, ethylenediamine, polyacrylamide, or cyclohexylamine.

[0013] Preferably, the molar ratio of fluorinated polylysine, nitrogen source, hydrogen peroxide and metal fluoride in step (2) is 1:(0.5-2.5):(2-6):(1-3).

[0014] Preferably, the ball milling time in step (2) is 1-4 h, the rotation speed is 300-600 rpm, and the mass ratio of the ball milling beads to the mixed material used in the ball milling process is 1:25-1:100.

[0015] Preferably, the inert gas in step (3) is one or two of nitrogen, argon, or helium.

[0016] Preferably, the conditions in step (3) are to heat to 400-700 ℃ at a heating rate of 2-10 ℃ / min and hold at that temperature for 1-4 h.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. This invention involves ball milling and copolymerizing fluorinated polylysine, a nitrogen source, hydrogen peroxide, and a metal fluoride salt to anchor abundant metal ions, followed by a one-step calcination to form an in-situ fluorine coordination structure.

[0019] 2. The metal loading of the fluorine-doped high-load metal single-atom catalyst in this invention can reach 20.0 wt%, which is much higher than the metal content in traditional single-atom catalysts.

[0020] 3. The fluorine-doped high-load metal single-atom catalyst of this invention has a simple preparation process, simple reaction equipment, low production cost, high safety, and broad market prospects. Compared with undoped metal single-atom catalysts, this invention, through fluorine doping modification, can efficiently catalyze the removal of organic pollutants and has excellent cycle performance, effectively solving the technical pain points of traditional single-atom catalysts such as low loading, insufficient activity, easy deactivation, and poor stability. Attached Figure Description

[0021] Figure 1 XPS image of the fluorine-doped highly loaded metal single-atom catalyst prepared in Example 1; Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to the scope described.

[0023] Example 1:

[0024] (1) Weigh 2.00 g of polylysine, add 2.00 mL of heptafluorobutyric anhydride, 3.00 mL of triethylamine and 40.0 mL of methanol, stir thoroughly for 72 h, and finally dry to obtain fluorinated polylysine.

[0025] (2) Subsequently, 0.56 g of iron fluoride, 0.45 g of 3,4-dihydroxyphenylpropionic acid and 1.00 g of fluorinated polylysine were weighed, and 1 mL of hydrogen peroxide was measured. All were placed in a ball mill jar and milled at 400 rpm for 2 h. After the reaction was completed, the polymer precursor was transferred to a ceramic boat and heated to 500 ℃ at a heating rate of 5 ℃ / min in a tube furnace under argon protection and held for 2 h. After natural cooling to room temperature, a fluorine-doped high-load metal single-atom catalyst was obtained with an iron loading of 20.53 wt%. Figure 1 The XPS spectrum clearly shows the characteristic peaks of Fe and F elements in the catalyst.

[0026] The catalyst can activate hydrogen peroxide (1 mg / L) to remove 99.9% of a 20 mg / L contaminant solution within 6 minutes, and its performance does not decrease significantly after 30 cycles of use.

[0027] Example 2:

[0028] (1) Weigh 2.00 g of polylysine, add 2 mL of heptafluorobutyric anhydride, 3 mL of triethylamine and 40 mL of ethanol, stir thoroughly for 72 h, and finally dry to obtain fluorinated polylysine.

[0029] (2) Subsequently, 0.58 g of cobalt fluoride, 0.45 g of 3,4-dihydroxyphenylpropionic acid and 1.00 g of fluorinated polylysine were weighed, and 1 mL of hydrogen peroxide was measured. All were placed in a ball mill jar and milled at 400 rpm for 2 h. After the reaction was completed, the polymer precursor was transferred to a ceramic boat and heated to 550 ℃ at a heating rate of 6 ℃ / min in a tube furnace under argon protection and held for 3 h. After natural cooling to room temperature, a fluorine-doped high-load metal single-atom catalyst was obtained with a cobalt loading of 19.27 wt%.

[0030] The catalyst can activate hydrogen peroxide (1 mg / L) within 6 minutes to remove 98.5% of a 20 mg / L contaminant solution, and its performance does not decrease significantly after 30 cycles of use.

[0031] Example 3:

[0032] (1) Weigh 2.00 g of polylysine, add 2 mL of heptafluorobutyric anhydride, 3 mL of triethylamine and 40 mL of ethanol, stir thoroughly for 72 h, and finally dry to obtain fluorinated polylysine.

[0033] (2) Subsequently, 0.58 g of nickel fluoride, 0.47 g of dopamine hydrochloride and 1.00 g of fluorinated polylysine were weighed, and 1 mL of hydrogen peroxide was measured. All were placed in a ball mill jar and milled at 500 rpm for 1 h. After the reaction was completed, the polymer precursor was transferred to a ceramic boat and heated to 600 ℃ at a heating rate of 3 ℃ / min in a tube furnace under argon protection and held for 3 h. After natural cooling to room temperature, a fluorine-doped high-load metal single-atom catalyst was obtained with a nickel loading of 20.16 wt%.

[0034] The catalyst can activate hydrogen peroxide (1 mg / L) within 6 minutes to remove 95.6% of a 20 mg / L contaminant solution, and its performance does not decrease significantly after 30 cycles of use.

[0035] Example 4:

[0036] (1) Weigh 2.00 g of polylysine, add 2 mL of heptafluorobutyric anhydride, 3 mL of triethylamine and 40 mL of ethyl acetate, stir thoroughly for 72 h, and finally dry to obtain fluorinated polylysine.

[0037] (2) Subsequently, 0.61 g of chromium fluoride, 0.55 g of catechol and 1.00 g of fluorinated polylysine were weighed, and 1 mL of hydrogen peroxide was measured. All were placed in a ball mill jar and milled at 300 rpm for 3 h. After the reaction was completed, the polymer precursor was transferred to a ceramic boat and heated to 400 ℃ at a heating rate of 8 ℃ / min in a tube furnace under argon protection and held for 5 h. After natural cooling to room temperature, a fluorine-doped high-load metal single-atom catalyst was obtained with a chromium loading of 19.39 wt%.

[0038] The catalyst can activate hydrogen peroxide (1 mg / L) to remove 96.3% of a 20 mg / L contaminant solution within 6 minutes, and its performance does not decrease significantly after 30 cycles of use.

[0039] Example 5:

[0040] (1) Weigh 2.00 g of polylysine, add 2.00 mL of heptafluorobutyric anhydride, 3.00 mL of triethylamine and 40.0 mL of dimethyl sulfoxide, stir thoroughly for 72 h, and finally dry to obtain fluorinated polylysine.

[0041] (2) Subsequently, 0.64 g of copper fluoride, 0.71 g of urea, and 1.00 g of fluorinated polylysine were weighed, and 1 mL of hydrogen peroxide was measured. All of these were placed in a ball mill jar and milled at 500 rpm for 2 h. After the reaction was completed, the polymer precursor was transferred to a ceramic boat and heated to 600 ℃ at a heating rate of 2 ℃ / min in a tube furnace under argon protection and held for 3 h. The mixture was then allowed to cool naturally to room temperature to obtain a fluorine-doped high-load metal single-atom catalyst with a copper loading of 21.54 wt%.

[0042] The catalyst can activate hydrogen peroxide (1 mg / L) within 6 minutes to remove 98.6% of a 20 mg / L contaminant solution, and its performance does not decrease significantly after 30 cycles of use.

[0043] Example 6:

[0044] (1) Weigh 2.00 g of polylysine, add 2.00 mL of heptafluorobutyric anhydride, 3.00 mL of triethylamine and 40.0 mL of dimethyl sulfoxide, stir thoroughly for 72 h, and finally dry to obtain fluorinated polylysine.

[0045] (2) Subsequently, 0.51 g of aluminum fluoride, 0.71 g of urea, and 1.00 g of fluorinated polylysine were weighed, and 1 mL of hydrogen peroxide was measured. All of these were placed in a ball mill jar and milled at 500 rpm for 2 h. After the reaction was completed, the polymer precursor was transferred to a ceramic boat and heated to 600 ℃ at a heating rate of 2 ℃ / min in a tube furnace under argon protection and held for 3 h. The mixture was then naturally cooled to room temperature to obtain a fluorine-doped high-load metal single-atom catalyst with an aluminum loading of 19.65 wt%.

[0046] The catalyst can activate hydrogen peroxide (1 mg / L) to remove 92.2% of a 20 mg / L contaminant solution within 6 minutes, and its performance does not decrease significantly after 30 cycles of use.

[0047] Example 7:

[0048] (1) Weigh 2.00 g of polylysine, add 2.00 mL of heptafluorobutyric anhydride, 3.00 mL of triethylamine and 40.0 mL of dimethyl sulfoxide, stir thoroughly for 72 h, and finally dry to obtain fluorinated polylysine.

[0049] (2) Subsequently, 0.62 g of zinc fluoride, 0.71 g of urea, and 1.00 g of fluorinated polylysine were weighed, and 1 mL of hydrogen peroxide was measured. All of these were placed in a ball mill jar and milled at 500 rpm for 2 h. After the reaction was completed, the polymer precursor was transferred to a ceramic boat and heated to 600 ℃ at a heating rate of 2 ℃ / min in a tube furnace under argon protection and held for 3 h. The mixture was then naturally cooled to room temperature to obtain a fluorine-doped high-load metal single-atom catalyst with a zinc loading of 21.36 wt%.

[0050] The catalyst can activate hydrogen peroxide (1 mg / L) to remove 96.3% of a 20 mg / L contaminant solution within 6 minutes, and its performance does not decrease significantly after 30 cycles of use.

[0051] Comparative Example 1:

[0052] (1) Weigh 0.56 g of iron fluoride, 0.45 g of 3,4-dihydroxyphenylpropionic acid, and 1.00 g of polylysine, and measure 1 mL of hydrogen peroxide. Place them together in a ball mill jar and mill at 500 rpm for 2 h. After the reaction is complete, transfer the polymer precursor to a ceramic boat and heat it to 600 ℃ at a heating rate of 2 ℃ / min in a tube furnace under argon protection. Hold the temperature for 3 h and allow it to cool naturally to room temperature to obtain a fluorine-free, high-loaded metal single-atom catalyst. The iron loading is 15.4 wt%.

[0053] The catalyst can activate hydrogen peroxide (1 mg / L) to remove 64.7% of a 20 mg / L contaminant solution within 6 minutes.

[0054] Comparative Example 2:

[0055] (1) Weigh 2.00 g of polylysine, add 2.00 mL of heptafluorobutyric anhydride, 3.00 mL of triethylamine and 40.0 mL of methanol, stir thoroughly for 72 h, and finally dry to obtain fluorinated polylysine.

[0056] (2) Subsequently, 0.56 g of iron fluoride and 1.00 g of fluorinated polylysine were weighed, and 1 mL of hydrogen peroxide was measured. All were placed in a ball mill jar and milled at 400 rpm for 2 h. After the reaction was complete, the polymer precursor was transferred to a ceramic boat and heated to 500 ℃ at a rate of 5 ℃ / min under argon protection in a tube furnace and held for 2 h. The mixture was then naturally cooled to room temperature to obtain a highly loaded nanoparticle metal catalyst. Single-atom catalysts could not be successfully prepared. The iron loading was 20.6 wt%.

[0057] The catalyst can activate hydrogen peroxide (1 mg / L) to remove 45.9% of a 20 mg / L contaminant solution within 6 minutes.

Claims

1. A method for preparing a fluorine-doped, highly supported metal single-atom catalyst, characterized in that, Includes the following steps: (1) Polylysine, heptafluorobutyric anhydride and triethylamine were dissolved in an organic solvent and dried to obtain fluorinated polylysine; (2) The fluorinated polylysine obtained in step (1) is mixed evenly with a nitrogen source, hydrogen peroxide and metal fluoride, and the mixture is then transferred into a ball mill jar for ball milling to obtain a polymer copolymer metal composite precursor. (3) The polymer copolymer metal composite precursor obtained in step (2) is transferred to a ceramic boat and calcined at high temperature under inert gas protection in a tube furnace. It is then naturally cooled to room temperature to obtain a fluorine-doped high-load metal single-atom catalyst.

2. The method for preparing a fluorine-doped, highly supported metal single-atom catalyst according to claim 1, characterized in that, The organic solvent mentioned in step (1) is one of methanol, ethanol, ethyl acetate, or dimethyl sulfoxide.

3. The method for preparing a fluorine-doped, highly supported metal single-atom catalyst according to claim 1, characterized in that, The metal fluoride mentioned in step (2) is one of iron fluoride, copper fluoride, cobalt fluoride, chromium fluoride, nickel fluoride, aluminum fluoride, or zinc fluoride.

4. The method for preparing a fluorine-doped highly supported metal single-atom catalyst according to claim 1, characterized in that, The nitrogen source mentioned in step (2) is one of 3,4-dihydroxyphenylpropionic acid, dopamine hydrochloride, levodopa, catechol, dicyandiamide, polyethyleneimine, urea, melamine, triethylenediamine, ethylenediamine, polyacrylamide, or cyclohexylamine.

5. The method for preparing a fluorine-doped highly supported metal single-atom catalyst according to claim 1, characterized in that, The mass ratio of fluorinated polylysine, nitrogen source, hydrogen peroxide and metal fluoride mentioned in step (2) is 1:(0.5-2.5):(2-6):(1-3).

6. The method for preparing a fluorine-doped highly supported metal single-atom catalyst according to claim 1, characterized in that, The ball milling time in step (2) is 1-4 h and the rotation speed is 300-600 rpm; wherein, the mass ratio of the ball milling beads to the mixed material used in the ball milling process is 1:25-1:

100.

7. The method for preparing a fluorine-doped highly supported metal single-atom catalyst according to claim 1, characterized in that, The inert gas mentioned in step (3) is one or two of nitrogen, argon, or helium; the conditions are to heat to 400-700 ℃ at a heating rate of 2-10℃ / min and hold at that temperature for 1-4 h.

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