A method for regulating the performance of a supported catalyst using a metal monatomic doped polymer coating

Abstract

This invention discloses a method for regulating the performance of supported catalysts using a polymer coating doped with metal single atoms, belonging to the field of catalyst technology. This method uses a polymer coating as a "bridge," anchoring atomically dispersed metal promoters through its abundant surface coordinating groups to construct an "active metal / support@polymer-metal single atom" composite structure. The metal single atoms are then used to regulate the metal-support interaction between the active metal and the support, achieving precise optimization of catalyst performance. This invention uses polymers such as polydopamine and polypyrrole, which can be grown in situ on various supports such as SiO2, BiOBr, and CuO. The metal promoters are atomically dispersed species such as Cu, Fe, Co, and Ni, and the active metals are noble metal nanoparticles such as Pt, Pd, and Ru. The prepared catalyst exhibits high selectivity, high stability, and versatility. The process is mild and simple to operate, and it can be widely applied to heterogeneous catalytic reactions such as selective hydrogenation, providing a new strategy for the design and modification of supported catalysts.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and more specifically to a method for regulating the performance of supported catalysts using a metal single-atom doped polymer coating. Background Technology

[0002] Supported noble metal catalysts are among the most widely used catalyst systems in heterogeneous catalytic reactions, playing an irreplaceable role in important chemical processes such as hydrogenation, oxidation, and reforming. However, traditional oxide supports (such as SiO2, Al2O3, TiO2, CeO2, etc.) or carbon materials have simple structures and lack effective active center control sites on their surfaces, making it difficult to precisely regulate the electronic state and geometry of the metal active centers. This often leads to poor selectivity in complex reaction systems.

[0003] Metal promoters, as a type of co-catalyst, refer to substances present in a catalyst that themselves lack catalytic activity or have very low activity, but can alter some of the catalyst's physical or chemical properties. The effects of metal promoters on reactive active sites generally include increasing stability, improving selectivity, and increasing reactivity. Transition metals (such as Fe, Co, Ni, Cu, etc.), alkali metals (such as Na, K, etc.), and other noble metals can all serve as metal promoters. Introducing metal promoters to regulate the metal-support interaction of supported noble metal catalysts and improve reaction selectivity is a common and effective method. However, how to stably introduce metal promoters into the catalyst system in an atomically dispersed form and achieve precise synergy with the active sites, enabling them to effectively regulate the strength and properties of the metal-support interaction, remains a current technical challenge.

[0004] Functionalized polymers such as polydopamine and polyvinylpyrrolidone are often used as coatings to coat nanomaterials.

[0005] Polydopamine, a polymer inspired by mussel adhesive proteins, possesses excellent adhesion properties and can self-polymerize on various substrate surfaces to form stable coatings. Polydopamine molecules contain abundant catechol hydroxyl and amino functional groups, which exhibit strong coordination capabilities for metal ions, enabling them to anchor and form stable coordination structures. Studies have shown that the two oxygen atoms in the catechol units and the nitrogen atom on the imine bond in polydopamine can coordinate with metal ions, achieving stable anchoring. Based on this property, polydopamine holds promise as a "bridge" connecting supports and metal promoters, enabling precise control over the performance of supported catalysts.

[0006] Furthermore, polydopamine exhibits exceptional adaptability, enabling it to be coated onto various nanomaterial surfaces, including oxides (SiO2, TiO2, CeO2, CuO, etc.), two-dimensional materials (BiOBr, etc.), molecular sieves (SBA-15, HY, etc.), and metal-organic frameworks (COF-300, etc.). This facilitates the development of diverse catalyst systems. More importantly, polydopamine coatings can provide abundant metal coordination sites for catalysts while preserving the original properties of the substrate material (such as magnetic, photoelectric, and porosity), thus achieving functional modification.

[0007] Therefore, utilizing the strong adhesion of polymers to supports and their chelating ability to metal sites to construct polymer coatings doped with single metal atoms, combining the dual functions of single-atom metal additives and polymers, may be an effective method for designing highly efficient catalysts. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention aims to provide a method for regulating the performance of supported catalysts using a metal single-atom doped polymer coating. By introducing a polymer coating containing atomically dispersed metal promoters between the catalyst support and active metal nanoparticles, the abundant coordinating groups in the polymer coating anchor the metal promoters. The metal promoters regulate the metal-support interaction between the active center and the support, thereby achieving effective regulation of the catalyst's catalytic performance.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: a method for regulating the performance of a supported catalyst using a metal single-atom doped polymer coating, comprising the following steps: (1) A polymer coating is formed on the surface of the substrate material to obtain a substrate@polymer composite material; (2) The substrate@polymer composite material obtained in step (1) is mixed with a metal salt solution to coordinate the metal ions with the coordination groups in the polymer coating. The metal ions are anchored on the polymer coating in the form of single atoms to obtain the substrate@polymer-M composite material, where M is an atomically dispersed metal additive. (3) The substrate@polymer-M composite material obtained in step (2) is mixed with an active metal precursor solution, and active metal nanoparticles are loaded on the surface of the material by impregnation reduction method to obtain M' / substrate@polymer-M catalyst, wherein M' is active metal nanoparticles.

[0010] Preferably, the substrate material in step (1) is selected from at least one of SiO2, BiOBr, CeO2, CuO, COF-300, SBA-15, and HY molecular sieve.

[0011] Preferably, the polymer coating in step (1) is a polydopamine coating, and its preparation method includes: dispersing the substrate material in a Tris-HCl buffer solution with a pH of 8.0-9.0, adding dopamine hydrochloride, the mass ratio of the substrate material to dopamine hydrochloride being 1:1-1:3, stirring and reacting at 20-30 °C for 20-30 hours, washing and drying to obtain the substrate@polydopamine composite material.

[0012] Preferably, the metal salt in step (2) is at least one of FeCl3, CoCl2, NiCl2, and CuCl2, with a concentration of 0.01-0.1 mol / L, and the mass-to-volume ratio of the substrate@polymer composite material to the metal salt solution is 1 g: 50-200 mL. The coordination reaction is carried out at 20-30 °C for 2-6 hours.

[0013] Preferably, the active metal precursor in step (3) is at least one of H2PtCl6, Na2PdCl4, and RuCl3, with a concentration of 0.01-0.05 mol / L; the reducing agent is an aqueous solution of sodium borohydride with a concentration of 0.5-2.0 mmol / L, and the molar ratio of the reducing agent to the active metal precursor is 5:1-20:1.

[0014] Preferably, the impregnation reduction method in step (3) includes: dispersing the substrate@polymer-M composite material in a solvent, adding an active metal precursor solution, stirring for 2-4 hours, then adding a reducing agent solution, continuing to stir in an ice-water bath for 1-3 hours, washing and drying to obtain the M' / substrate@polymer-M catalyst.

[0015] The present invention also provides an M' / substrate@polymer-M catalyst prepared by the above method.

[0016] Preferably, in the catalyst, the metal auxiliary M is dispersed in the polymer coating in the form of single atoms, forming a coordination structure with the N and O atoms in the polymer coating.

[0017] Preferably, in the catalyst, there is an electron transfer between the metal promoter M and the active metal M', where some electrons of M' are transferred to M, causing the valence state of M' to increase and the valence state of M to decrease. Beneficial effects

[0018] This invention creatively proposes a universal method for regulating the performance of supported catalysts using a metal single-atom doped polymer coating. By introducing a polymer coating containing atomically dispersed metal promoters between the catalyst support and the active metal nanoparticles, the abundant coordinating groups in the polymer coating anchor the metal promoters. The metal promoters regulate the metal-support interaction between the active center and the support, thereby achieving precise regulation of the catalyst's catalytic performance.

[0019] The method of this invention is universal and flexible, allowing for the preparation of various catalysts suitable for different reaction systems by freely changing the combination of substrate materials, polymer coatings, metal additives, and active metals. This invention has been successfully extended to the synthesis of catalysts with various substrate materials and polymer coatings, and the successful synthesis of these catalysts has been confirmed by TEM, XRD, FT-IR, and other methods.

[0020] The method of this invention is simple and easy to implement, with mild reaction conditions and no need for harsh conditions such as high temperature and high pressure, which is conducive to large-scale promotion and application, and provides new ideas and strategies for the design of supported catalysts. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the preparation process of Pt / SiO2@PDA-M catalyst.

[0022] Figure 2 This is a TEM image of the Pt / SiO2@PDA-Cu catalyst.

[0023] Figure 3 This is a TEM image of the Pt / SiO2@PDA-Fe catalyst.

[0024] Figure 4 This is a TEM image of the Pt / SiO2@PDA-Co catalyst.

[0025] Figure 5 This is a TEM image of the Pt / SiO2@PDA-Ni catalyst.

[0026] Figure 6 The image shows the XRD pattern of the Pt / SiO2@PDA-M series catalysts.

[0027] Figure 7 The image shows the FT-IR spectrum of the Pt / SiO2@PDA-M series catalysts. Specific implementation examples

[0028] The present invention will be further described below with reference to specific embodiments and comparative examples, but the scope of protection of the present invention is not limited thereto.

[0029] Example 1: Synthesis of Pt / SiO2@PDA-Cu.

[0030] Synthesis of SiO2 Add 40 mL of ammonia and 345 mL of anhydrous ethanol to a 1 L round-bottom flask and stir at 600 rpm for 5 min. Slowly add 15 mL of tetraethyl orthosilicate and continue stirring for 20 min. After the reaction is complete, centrifuge at 8000 rpm to collect the white precipitate, wash twice alternately with deionized water and anhydrous ethanol, and dry under vacuum at 60 °C overnight to obtain SiO2 nanoparticles.

[0031] Synthesis of SiO2@PDA 100 mg of the prepared SiO2 microspheres were dispersed in 20 mL of Tris-HCl buffer solution (pH = 8.5, 10 mmol / L) and ultrasonically dispersed until homogeneous. 200 mg of dopamine hydrochloride was added, and the mixture was stirred at room temperature for 24 h. After the reaction was complete, the brown precipitate was collected by centrifugation at 8000 rpm, washed twice alternately with deionized water and anhydrous ethanol, and then vacuum-dried overnight at 60 °C to obtain the SiO2@PDA core-shell material.

[0032] Synthesis of Pt / SiO2@PDA 100 mg SiO2@PDA was dissolved in 18 mL of methanol and ultrasonically dispersed. Then, 27 μL of H2PtCl6 aqueous solution (0.1926 g / mL) was added, and the mixture was ultrasonicated for another 20 min followed by stirring for 2 h. Next, 2 mL of fresh sodium borohydride aqueous solution (0.81 mM) was added under ice-water bath and vigorous stirring, and stirring was continued for another 2 h. After centrifugation at 8000 rpm, the sample was washed twice with methanol and water, and then vacuum-dried overnight at 60 °C. Finally, the sample was collected in a sealed glass bottle for further processing.

[0033] Synthesis of Pt / SiO2@PDA-Cu 100 mg Pt / SiO2@PDA was dissolved in 20 mL of methanol, ultrasonically dispersed, and 0.0625 mL of CuCl2 methanol solution (32 mg / mL) was added. The mixture was stirred at room temperature for 3 h, centrifuged at 8000 rpm, washed twice with methanol and water respectively, and vacuum dried overnight at 60 °C. The sample was then collected and placed in a sealed glass bottle for later use.

[0034] Example 2: Synthesis of Pt / SiO2@PDA-Fe Dissolve 100 mg Pt / SiO2@PDA in 20 mL of methanol, sonicate to disperse evenly, add 0.0625 mL of FeCl3 methanol solution (41 mg / mL), stir at room temperature for 3 h, centrifuge at 8000 rpm, wash twice with methanol and water respectively, vacuum dry at 60 ℃ overnight, collect the sample and place it in a sealed glass bottle for later use.

[0035] Example 3: Synthesis of Pt / SiO2@PDA-Co 100 mg Pt / SiO2 @PDA was dissolved in 20 mL of methanol, ultrasonically dispersed, and 0.0625 mL of CoCl2 methanol solution (33 mg / mL) was added. The mixture was stirred at room temperature for 3 h, centrifuged at 8000 rpm, washed twice with methanol and water respectively, and vacuum dried at 60 ℃ overnight. The sample was then collected and placed in a sealed glass bottle for later use.

[0036] Example 4: Synthesis of Pt / SiO2@PDA-Ni 100 mg Pt / SiO2@PDA was dissolved in 20 mL of methanol, ultrasonically dispersed, and 0.0625 mL of NiCl2 methanol solution (34 mg / mL) was added. The mixture was stirred at room temperature for 3 h, centrifuged at 8000 rpm, washed twice with methanol and water respectively, and vacuum dried overnight at 60 °C. The sample was then collected and placed in a sealed glass bottle for later use.

[0037] Example 5: Selective hydrogenation of 4-nitrostyrene The catalyst (10 mg), 4-nitrostyrene (60 mg), and ethanol (8 mL) were placed in a glass bottle and sonicated for 10 min to form a homogeneous suspension. Then, 2 mL of deionized water containing 40 mg of ammonia borane was added to the mixture. The mixture was stirred at 25 °C. During the reaction, small amounts of solution were periodically taken out and centrifuged to collect the supernatant. The samples (phenylacetylene, 4-nitrostyrene) were analyzed using an Agilent gas chromatograph (GC7820A). For specific catalytic comparisons, see [link to relevant documentation].

[0038] Comparative Example 1: Preparation of Pt / SiO2 catalyst 100 mg SiO2 was dissolved in 18 mL of methanol and ultrasonically dispersed. Then, 27 μL of H2PtCl6 aqueous solution (0.1926 g / mL) was added, and the mixture was ultrasonicated for another 20 min followed by stirring for 2 h. Next, 2 mL of fresh sodium borohydride aqueous solution (0.81 mM) was added under ice-water bath and vigorous stirring, and stirring was continued for another 2 h. After centrifugation at 8000 rpm, the sample was washed twice with methanol and water, and then vacuum-dried overnight at 60 °C. Finally, the sample was collected in a sealed glass bottle for further processing.

[0039] Comparison of catalytic performance of hydrogenation of nitrostyrene to aminostyrene catalyst Reaction time (min) Conversion rate (%) Selectivity (%) Yield (%) <![CDATA[Pt / SiO2@PDA-Cu]]> 45 100 100 100 <![CDATA[Pt / SiO2@PDA-Co]]> 45 100 87 87 <![CDATA[Pt / SiO2@PDA-Fe]]> 45 100 81 81 <![CDATA[Pt / SiO2@PDA-Ni]]> 45 100 89 89 <![CDATA[Pt / SiO2]]> 45 100 35 35 <![CDATA[Pt / SiO2@PDA]]> 45 100 73 73 <![CDATA[Pt / SiO2@PDA-Cu]]> 360 100 100 100

Claims

1. A method for regulating the performance of a supported catalyst using a metal single-atom doped polymer coating, characterized in that... The catalyst structure includes a support, metal nanoparticle active centers, metal single-atom promoters, and a polymer coating.

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