A porous noble metal core-shell catalyst material, a preparation method and applications thereof

Abstract

The application discloses a kind of porous noble metal core-shell catalyst materials, preparation method and its application, the core-shell catalyst is the microsphere of whole forming core-shell structure, adjustable control through type porous channel is successfully constructed in shell phase, the structure effectively connects the active site of core phase with external reaction system, constructs the efficient mass transfer path of reactant molecule direct active site, reduces mass transfer resistance;At the same time, crosslinked shell can effectively inhibit the migration, agglomeration or loss of noble metal nanoparticles, thereby simultaneously improving the activity and structural stability of catalyst.The porous core-shell catalyst developed by the application exhibits significant advantages in catalytic activity, structure controllability and mass transfer efficiency, and is suitable for various heterogeneous catalytic reactions, and has wide application prospects in fine chemical industry, environmental catalysis and energy conversion.

Description

Technical Field

[0001] This invention relates to the field of functional materials and catalysts, specifically to a porous noble metal core-shell catalyst material, its preparation method, and its application. Background Technology

[0002] Noble metal catalysts, particularly those represented by palladium (Pd) and platinum (Pt), play a crucial role in key fields such as energy and chemical engineering, fine synthesis, and environmental pollution control due to their high catalytic activity, excellent selectivity, and relatively mild reaction conditions. However, the scarcity and high cost of precious metal resources, coupled with the tendency for their nanoscale active centers to aggregate and be lost during reactions, leading to a sharp decline in catalytic activity and stability, severely restrict their large-scale industrial application.

[0003] Core-shell catalysts, as advanced functional materials, effectively inhibit the migration, aggregation, and loss of active components by loading the active components into the core and providing physical protection through the outer shell, thereby significantly improving material stability. However, traditional core-shell catalysts still have significant limitations in their material structure. The shell is usually a dense, non-porous structure, which, while providing some protection, severely hinders the diffusion of reactants and products. At the same time, limitations in the preparation process lead to poor particle size uniformity of the catalyst, and the core-shell size is difficult to control precisely, resulting in insufficient material uniformity and regularity. Ultimately, this leads to high mass transfer resistance inside the catalyst and low utilization of active sites.

[0004] Therefore, developing a new material that can simultaneously achieve precise construction of the core-shell structure and porous shell is crucial for developing a new generation of catalysts with both high stability and high intrinsic activity. Summary of the Invention

[0005] The main objective of this invention is to provide a porous noble metal core-shell catalyst material, its preparation method, and its application. This core-shell catalyst material achieves an integrated construction of a porous channel penetrating the shell and a regular core-shell structure, thereby solving the problems of low mass transfer efficiency and / or poor stability caused by the compactness of the shell and irregular structure of traditional core-shell catalysts.

[0006] To achieve the above objectives, one aspect of the present invention provides a porous noble metal core-shell catalyst, characterized in that the catalyst is an integrally formed core-shell structured microsphere; the core phase of the microsphere comprises a hydrophilic polymer matrix loaded with noble metal nanoparticles, and the shell phase of the microsphere comprises a cross-linked hydrophilic polymer network layer that completely covers the core phase. The shell phase contains a continuous porous channel that extends through its thickness. This porous channel spatially connects the core phase and the external environment of the microspheres, thereby providing a directional and repeatable mass transfer path for reactants and products inside and outside the core-shell structure while maintaining the integrity of the shell phase structure.

[0007] Specifically, the catalyst is structurally a monolithically formed core-shell microsphere. Its core phase mainly comprises a hydrophilic polymer matrix loaded with noble metal nanoparticles, while the shell phase mainly comprises a cross-linked hydrophilic polymer network that completely encapsulates the core phase. Simultaneously, by constructing a pervasive porous channel structure in the shell layer to connect the core phase with the external environment of the core-shell catalyst, a highly efficient mass transfer pathway is built for reactants in the external environment to directly reach the catalytic active sites. This effectively solves the mass transfer limitation problem of traditional core-shell catalyst materials, significantly improving the diffusion efficiency of reactants and products and the accessibility of active sites.

[0008] Alternatively, in conjunction with any of the above aspects, in another implementation of this aspect, the continuous porous channel is formed by adding a pore-forming agent before the shell crosslinking and curing, and removing the pore-forming agent after curing.

[0009] Alternatively, in conjunction with any of the above aspects, in another implementation of this aspect, the pore-forming agent is selected from at least one of polyvinylpyrrolidone, polyethylene glycol, and polyvinyl alcohol.

[0010] Alternatively, in conjunction with any of the above aspects, in another implementation of this aspect, the noble metal nanoparticles include Pd and / or Pt, and the noble metal nanoparticles exist in a dispersed state in the core phase.

[0011] Optionally, in combination with any of the above aspects, in another implementation of this aspect, the particle size of the noble metal nanoparticles is 1-20 nm; Alternatively, in conjunction with any of the above aspects, in another implementation of this aspect, the hydrophilic polymer network layer comprises polyethylene glycol diacrylate, and / or the hydrophilic polymer matrix comprises dextran.

[0012] Specifically, the polyethylene glycol diacrylate is preferably at least one of PEGDA-200, PEGDA-400, PEGDA-575, and PEGDA-600; the dextran is preferably at least one of Dextran-20000, Dextran-40000, Dextran-70000, and Dextran-500000.

[0013] Optionally, in conjunction with any of the above aspects, in another implementation of this aspect, the diameter of the core-shell structured microspheres is 10-500 μm, wherein the diameter of the core phase is 8-400 μm. As another aspect of the present invention, a method for preparing a porous noble metal core-shell catalyst is provided, comprising the following steps: (1) Preparation of noble metal nanoparticles; (2) Prepare a shell-phase polymer solution R1 containing a photoinitiator and a pore-forming agent, and stably disperse the noble metal nanoparticles in step (1) in a core-phase polymer solution R2, and select dimethyl silicone oil containing a surfactant as a continuous phase solution R3. (3) The shell-phase polymer solution R1, the core-phase polymer solution R2 and the continuous phase solution R3 are injected into the microfluidic chip for mixing. After being sheared by the continuous phase solution R3, the shell-phase polymer solution R1 and the core-phase polymer solution R2 form a core-shell microsphere with the core-phase polymer solution R2 wrapped by the shell-phase polymer solution R1. The core-shell microspheres are collected at the reaction outlet. (4) Irradiate the core-shell microspheres with blue light to induce cross-linking and curing of the shell layer, and collect the cured core-shell microspheres; (5) The solidified core-shell microspheres are washed repeatedly with deionized water to selectively remove the pore-forming agent from the solidified shell layer, thereby forming a continuous porous channel in situ through its thickness in the shell layer, and obtaining the porous noble metal core-shell catalyst.

[0014] Alternatively, in combination with any of the above aspects, in another implementation of this aspect, in step (1), the noble metal nanoparticles are prepared by a liquid-liquid segmented flow microfluidic system.

[0015] Alternatively, in combination with any of the above aspects, in another implementation of this aspect, the shell-phase polymer solution R1 and the core-phase polymer solution R2 constitute a two-aqueous-phase system. When the concentrations of the two incompatible polymers in the aqueous solvent exceed a threshold, liquid-liquid phase separation occurs inside the continuous phase solution R3, spontaneously forming the core-shell microspheres.

[0016] Specifically, in step (3), two-phase fluid shearing is used to generate microspheres with uniform size, controllable structure, and good monodispersity. Furthermore, this is combined with the principle of aqueous two-phase system (ATPS) phase separation. By utilizing the inherent thermodynamic instability of the system, phase separation is induced inside the microfluidically generated microspheres, which can realize the spontaneous enrichment of active components in a specific phase region. Thus, the self-assembly of the core-shell structure is completed in one step, simplifying the traditional multi-step loading process.

[0017] Optionally, in conjunction with any of the above aspects, in another implementation of this aspect, in step (2), the shell-phase polymer solution R1 has a mass concentration of 1-60 wt% for the shell-phase polymer, a mass concentration of 0.1-2 wt% for the photoinitiator, and a mass-volume concentration of 0.1-5 wt% for the pore-forming agent; the core-phase polymer solution R2 has a mass concentration of 1-40 wt% for the core-phase polymer, and a mass concentration of 0.1-1.0 wt% for the noble metal nanoparticles;

[0018] Optionally, in combination with any of the above aspects, in another implementation of this aspect, in step (3), the flow rate of the shell phase polymer solution R1 is 1-20 μL / min; the flow rate of the core phase polymer solution R2 is 1-10 μL / min; and the flow rate of the continuous phase solution R3 is 30-120 μL / min.

[0019] Optionally, in combination with any of the above aspects, in another implementation of this aspect, step (4) further includes, after initiating the cross-linking and curing of the shell layer: allowing the mixture containing the core-shell microspheres and the continuous phase solution R3 to stand and separate into layers, separating the continuous phase solution R3 for recycling, and collecting the cured core-shell microspheres.

[0020] Optionally, in conjunction with any of the above aspects, in another implementation of this aspect, prior to step (5), the preparation method further includes: The solidified core-shell microspheres were collected by washing with a mixture of n-hexane and ethyl acetate, followed by demulsification and removal of dimethyl silicone oil. The microspheres were collected after washing until they formed clusters.

[0021] As another aspect of the present invention, an application of the porous noble metal core-shell catalyst according to any of the above aspects in the hydrogenation reduction reaction of aromatic compounds is provided.

[0022] Alternatively, in conjunction with any of the above aspects, in another implementation of this aspect, the aromatic compound is p-nitrophenol, and the catalyst exhibits high activity and excellent stability in the hydrogenation reduction reaction of p-nitrophenol, verifying the advantages of the porous noble metal core-shell catalyst material of the present invention.

[0023] In summary, the porous noble metal core-shell catalyst provided by this invention offers a new solution for achieving high-performance core-shell catalyst materials with precise and controllable structure.

[0024] Compared with the prior art, the present invention has the following beneficial effects: (1) The porous noble metal core-shell catalyst provided by the present invention effectively solves the mass transfer limitation problem of traditional core-shell materials by constructing tunable through porous channels in the shell layer, and significantly improves the diffusion efficiency of reactants and products and the accessibility of active sites.

[0025] (2) The integrally formed core-shell structure and shell cross-linking network provide a stable three-dimensional network confinement environment for noble metal nanoparticles, which greatly inhibits the migration and aggregation of noble metal nanoparticles. The catalyst has excellent structural stability and recyclability.

[0026] (3) The catalyst provided by the present invention is prepared by microfluidic technology, thus having good core-shell size uniformity and structural regularity, which improves the problem of poor batch consistency of traditional core-shell catalysts and ensures the high reproducibility and reliability of the catalyst performance in application.

[0027] The above summary provides a simplified overview of some concepts, which will be further described in detail in the following specific embodiments. The above summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to help determine the scope of the claimed subject matter. The claimed subject matter is not limited to embodiments that address any or all the shortcomings pointed out in the background art.

[0028] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by means of embodiments thereof. Attached Figure Description

[0029] The accompanying drawings, incorporated in and forming part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without any creative effort. These drawings and textual descriptions are not intended to limit the scope of the concept of this application in any way, but rather to illustrate the concepts of this application to those skilled in the art by referring to specific embodiments.

[0030] Figure 1 This is a schematic diagram of the microfluidic preparation process of the porous noble metal core-shell catalyst provided in Example 1 of the present invention; Figure 2 This is an optical microscope image of Pd / Dextran@PEGDA-3 prepared in Example 3 of this invention; Figure 3These are SEM images of Pd / Dextran@PEGDA prepared in Examples 1-3 and Comparative Example 1 of this invention; Figure 4 This is a performance comparison chart of the core-shell catalyst products prepared in various embodiments and comparative examples of the present invention in the catalytic hydrogenation of p-nitrophenol. Figure 5 This is the real-time UV absorption spectrum of Pd / Dextran@PEGDA-3 prepared in Example 3 of this invention in the application of catalytic hydrogenation reduction of p-nitrophenol; Figure 6 This is a cycle stability test diagram of Pd / Dextran@PEGDA-3 prepared in Example 3 of the present invention in the application of p-nitrophenol catalytic hydrogenation reduction reaction. Detailed Implementation

[0031] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0032] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. It should be further understood that, as used herein, the singular forms "a," "an," and "the" are intended to also include the plural forms, unless the context indicates otherwise. Furthermore, the terms "or," "and / or," "including at least one of the following," etc., as used herein, can be interpreted as inclusive, or mean any one or any combination thereof. Exceptions to this definition only arise when combinations of elements, functions, steps, or operations are inherently mutually exclusive in some manner.

[0033] It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit the scope of this application. Unless otherwise specified, the materials, reagents, etc., used in the following embodiments are commercially available. Experimental methods not specifically described in the embodiments are generally performed under conventional conditions or as recommended by the manufacturer. Example

[0034] (1) Take 10 ml of deionized water, add 0.03 g of palladium chloride, 0.05 g of polyvinylpyrrolidone (PVP, K60, molecular weight about 360,000), and 0.04 g of potassium bromide (KBr), and sonicate at 60 °C for 1 h to obtain a uniformly dispersed Pd precursor solution; take another 10 ml of deionized water, add 0.06 g of sodium borohydride and 0.05 g of PVP, and sonicate at room temperature for 1 h to obtain a uniformly dispersed metal reducing agent solution; prepare dimethyl silicone oil containing 5 wt% surfactant, and sonicate at room temperature for 1 h to obtain a continuous phase solution.

[0035] (2) The Pd precursor solution was loaded into syringe No. 1 (flow rate set to 20 μL / min), the metal reducing agent solution was loaded into syringe No. 2 (flow rate set to 20 μL / min), and dimethyl silicone oil containing 5 wt% surfactant was loaded into syringe No. 3 (flow rate set to 120 μL / min) as the continuous phase. The syringes and the microfluidic chip were connected by a PE tube. The phases were pumped into the Y-type mixing unit of the microfluidic chip by an injection pump for mixing. After oil phase shearing, water-in-oil (W / O) microspheres were formed as tiny single chambers for reaction. A cooling device was set at the reaction outlet to collect the products and quench the reaction.

[0036] The microfluidic chip has the following specifications: (150*150 μm, h=75 μm).

[0037] (3) After standing and separating the layers, separate the upper layer of silicone oil and add an equal volume of n-hexane and ethyl acetate mixed solvent to the lower layer of aqueous phase to demulsify until the microspheres are in clusters, which proves that they are clean; finally, wash the remaining impurities with deionized water.

[0038] (4) The washing product was dried at 80 °C for 12 h to obtain the Pd nanoparticles.

[0039] (5) Take 5.0 g of deionized water, add 5.0 g of polyethylene glycol diacrylate (PEGDA-575), 0.05 g of pore-forming agent PVP, and 0.1 g of photoinitiator phenyl (2,4,6-trimethylbenzoyl) lithium phosphate, and sonicate at 60 °C in the dark for 1 h to obtain a uniformly dispersed shell phase polymer solution (R1); take another 5.0 g of deionized water, add 5 mg of Pd nanoparticles prepared in step (4) and 0.5 g of dextran (Dextran-500000), and sonicate at room temperature for 1 h to obtain a uniformly dispersed core phase polymer solution (R2).

[0040] (6) For example Figure 1As shown, R1 solution was placed in syringes 1 and 2 (flow rate set to 4 μL / min) in the dark, R2 solution was placed in syringe 3 (flow rate set to 3 μL / min), and dimethyl silicone oil containing 5 wt% surfactant was placed in syringe 4 (flow rate set to 40 μL / min). The syringes and microfluidic chip were connected using PE tubing, and the phases were pumped into the microfluidic chip for mixing using an injection pump. After shearing by the oil phase, water-in-oil (W / O) microspheres were formed, and the microspheres were collected at the reaction outlet.

[0041] (7) Irradiate the core-shell microspheres with blue light for 100 s to induce PEGDA crosslinking and curing.

[0042] (8) Allow to stand and separate the layers to separate the dimethyl silicone oil. Wash the crude product with a mixture of n-hexane and ethyl acetate to demulsify until the microspheres are in clusters, indicating that it is clean. Finally, wash the residual pore-forming agent PVP with deionized water multiple times to obtain the porous Pd / Dextran@PEGDA-1 core-shell catalyst. Example

[0043] (1) Take 4.0 g of deionized water, add 6.0 g of PEGDA-575, 0.1 g of pore-forming agent PVP, and 0.1 g of photoinitiator phenyl (2,4,6-trimethylbenzoyl) lithium phosphate, and sonicate at 60 °C in the dark for 1 h to obtain a uniformly dispersed shell-phase polymer solution (R1); take another 5.0 g of deionized water, add 5 mg of Pd nanoparticles prepared in Example 1 and 0.75 g of Dextran-200000, and sonicate at room temperature for 1 h to obtain a uniformly dispersed core-phase polymer solution (R2).

[0044] (2) Following the same steps and process parameters as in Example 1 (6) to (8), a porous Pd / Dextran@PEGDA-2 core-shell catalyst was obtained. Example

[0045] (1) Take 6.0 g of deionized water, add 4.0 g of PEGDA-575, 0.15 g of pore-forming agent PVP, and 0.1 g of photoinitiator phenyl (2,4,6-trimethylbenzoyl) lithium phosphate, and sonicate at 60 °C in the dark for 1 h to obtain a uniformly dispersed shell-phase polymer solution (R1); take another 5.0 g of deionized water, add 5 mg of Pd nanoparticles prepared in Example 1 and 1.0 g of Dextran-70000, and sonicate at room temperature for 1 h to obtain a uniformly dispersed core-phase polymer solution (R2).

[0046] (2) Following the same steps and process parameters as in Example 1 (6) to (8), a porous Pd / Dextran@PEGDA-3 core-shell catalyst was obtained. Example

[0047] (1) Take 10 ml of deionized water, add 0.08 g of chloroplatinic acid, 0.05 g of PVP and 0.04 g of potassium bromide (KBr), and sonicate at 60℃ for 1 h to obtain a uniformly dispersed Pt precursor solution; take another 10 ml of deionized water, add 0.06 g of sodium borohydride and 0.05 g of PVP, and sonicate at room temperature for 1 h to obtain a uniformly dispersed metal reducing agent solution; prepare dimethyl silicone oil containing 5 wt% surfactant, and sonicate at room temperature for 1 h to obtain a continuous phase solution.

[0048] (2) The Pt precursor solution is loaded into syringe No. 1 (flow rate set to 20 μL / min), the metal reducing agent solution is loaded into syringe No. 2 (flow rate set to 20 μL / min), and dimethyl silicone oil containing 5 wt% surfactant is loaded into syringe No. 3 (flow rate set to 120 μL / min) as the continuous phase. The syringes and the microfluidic chip are connected by a PE tube. The phases are pumped into the Y-type mixing unit of the microfluidic chip by an injection pump for mixing. After oil phase shearing, water-in-oil (W / O) microspheres are formed as tiny single chambers for reaction. A cooling device is set at the reaction outlet to collect the product and quench the reaction.

[0049] (3) The Pt nanoparticles were obtained by following the same steps and process parameters as in Example 1 (3) to (4).

[0050] (4) Take 6.0 g of deionized water, add 4.0 g of PEGDA-575, 0.15 g of pore-forming agent PVP, and 0.1 g of photoinitiator phenyl (2,4,6-trimethylbenzoyl) lithium phosphate, and sonicate at 60 °C in the dark for 1 h to obtain a uniformly dispersed shell phase polymer solution (R1); take another 5.0 g of deionized water, add 5 mg of Pt nanoparticles prepared in step (3) and 1.0 g of Dextran-70000, and sonicate at room temperature for 1 h to obtain a uniformly dispersed core phase polymer solution (R2).

[0051] (5) Following the same steps and process parameters as in Example 1 (6) to (8), a porous Pt / Dextran@PEGDA-1 core-shell catalyst was obtained.

[0052] Comparative Example 1 In this embodiment, unlike in Example 3, no pore-forming agent PVP was added to the shell-phase polymer solution. The remaining production steps and process parameters were the same as in Example 3, resulting in a Pd / Dextran@PEGDA-4 core-shell catalyst (without porous structure in the shell phase).

[0053] Comparative Example 2 In this embodiment, unlike in Example 4, no pore-forming agent PVP was added to the shell-phase polymer solution. The remaining production steps and process parameters were the same as in Example 4, resulting in a Pt / Dextran@PEGDA-2 core-shell catalyst (without porous structure in the shell phase).

[0054] Testing and Characterization The products obtained from the various embodiments and comparative examples were characterized in the following three ways: (1) Microscopic images of the core-shell catalysts prepared in each example were taken, and the optical micrograph of the core-shell catalyst prepared in Example 3 is shown below. Figure 2 As shown.

[0055] (2) The Pd / Dextran@PEGDA core-shell catalysts prepared in Examples 1-3 and Comparative Example 1 were characterized by SEM. The scanning electron microscope images are shown below. Figure 3 As shown.

[0056] (3) The hydrogenation reduction performance of the core-shell catalysts prepared in each embodiment was tested for p-nitrophenol (4-NP). Test method: First, 3 ml of 1 mM 4-NP was added to a 5 ml cuvette, then 0.05 g of the core-shell catalyst was added, and finally 300 μL of 100 mM sodium borohydride aqueous solution was added to carry out the catalytic reaction. The catalytic reaction was carried out at room temperature, and the concentration of 4-NP in the liquid before and after catalysis was recorded using a UV-Vis spectrophotometer. The conversion efficiency of 4-NP was calculated using the following formula: Where C1 is the 4-NP concentration before the reaction, and C2 is the 4-NP concentration after the reaction.

[0057] Optical micrograph of the Pd / Dextran@PEGDA-3 core-shell catalyst prepared in Example 3, as shown in the image. Figure 2 As shown, uniformly sized and regularly shaped core-shell microspheres are visible within the field of view, with an outer shell size of approximately 90 μm and a core size of approximately 45 μm. Due to the inherent thermodynamic instability of the aqueous two-phase system, thermodynamically driven phase separation spontaneously occurs inside the microspheres, causing Pd nanoparticles and hydrophilic dextran to co-enrich and self-assemble into a dense core, while PEGDA forms a shell encapsulating the outer layer.

[0058] Figure 3Scanning electron microscopy (SEM) images were used to compare the morphology of Pd / Dextran@PEGDA prepared in Examples 1-3 and Comparative Example 1 under different amounts of pore-forming agent. As the amount of pore-forming agent gradually increased (corresponding to Pd / Dextran@PEGDA-1 to Pd / Dextran@PEGDA-3), the shell structure of the catalyst showed a gradual trend of increasing pore density with increasing pore-forming agent content. In stark contrast, the shell surface of the product of Comparative Example 1 (Pd / Dextran@PEGDA-4) without added pore-forming agent was smooth and dense, with almost no pore structure.

[0059] The catalysts obtained in each embodiment were used in the 4-NP hydrogenation reduction reaction to test their catalytic performance, such as... Figure 4 As shown, the products of Examples 1, 2, and 3 (corresponding to Pd / Dextran@PEGDA-1 to Pd / Dextran@PEGDA-3) exhibited significantly improved catalytic efficiency with increasing PVP (porphopolymer) content. Pd / Dextran@PEGDA-3 showed the best performance, achieving near-complete conversion (conversion ≈ 100%) within approximately 10 minutes, while the product of Comparative Example 1, Pd / Dextran@PEGDA-4 (without PVP), showed a lower conversion rate within the same timeframe. Similarly, the product of Example 4, Pt / Dextran@PEGDA-1, and the product of Comparative Example 2, Pt / Dextran@PEGDA-2, also showed the same trend.

[0060] This trend and Figure 3 The observed trends in shell pore density are highly consistent, indicating that adjusting the content of shell-phase pore-forming agent can effectively regulate the pore structure of the catalyst shell, thereby enhancing the accessibility of active sites and reaction mass transfer efficiency, and ultimately achieving targeted optimization of catalytic performance.

[0061] The real-time UV-Vis absorption spectrum of the Pd / Dextran@PEGDA-3 catalyst prepared in Example 3 during the 4-NP catalytic hydrogenation reduction reaction is shown below. Figure 5 As shown, the intensity of the characteristic absorption peak at 400 nm, attributed to 4-NP, exhibits a continuous and rapid decreasing trend with reaction time from 0 min to 10 min, and essentially returns to baseline at the end of the reaction, indicating that 4-NP molecules are efficiently and almost completely converted in a short time. The high catalytic efficiency of this catalyst stems from its porous core-shell structure. The through-shell channels significantly reduce mass transfer resistance, ensuring rapid transport of reactants to the Pd active sites within the core phase.

[0062] like Figure 6As shown, the Pd / Dextran@PEGDA-3 prepared in Example 3 still exhibited high activity after seven cycles. Its high activity and durability are attributed to its porous core-shell structure. Pd nanoparticles exist in a highly dispersed state within the Dextran core phase, while the porous channel network constructed within the PEGDA shell ensures efficient mass transfer between reactants and products while maintaining the overall structural integrity of the shell phase, thus maintaining high accessibility to active sites over a long period.

[0063] In summary, the porous noble metal core-shell catalyst provided by this invention successfully achieves synergistic optimization of catalytic efficiency and long-term stability, providing a new solution for developing high-performance, long-life heterogeneous catalyst materials, and showing broad application prospects in fine chemicals, energy conversion and environmental catalysis.

[0064] The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0065] In this application, the same or similar terms, concepts, technical solutions and / or application scenario descriptions are generally described in detail only when they appear for the first time. When they appear again, they are generally not repeated for the sake of brevity. When understanding the technical solutions and other contents of this application, the same or similar terms, concepts, technical solutions and / or application scenario descriptions that are not described in detail later can be referred to their previous relevant detailed descriptions.

[0066] In this application, the descriptions of the various embodiments have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0067] The technical features of the present application can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of the present application.

[0068] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A porous noble metal core-shell catalyst, characterized in that, The catalyst is an integrally formed core-shell structured microsphere; the core phase of the microsphere includes a hydrophilic polymer matrix loaded with noble metal nanoparticles, and the shell phase of the microsphere includes a cross-linked hydrophilic polymer network layer that completely covers the core phase. The shell phase contains a continuous porous channel that extends through its thickness. This porous channel spatially connects the core phase and the external environment of the microspheres, thereby providing a directional and repeatable mass transfer path for reactants and products inside and outside the core-shell structure while maintaining the integrity of the shell phase structure.

2. The porous noble metal core-shell catalyst according to claim 1, characterized in that, The continuous porous channels are formed by adding a pore-forming agent before the shell crosslinking and curing, and removing the pore-forming agent after curing.

3. The porous noble metal core-shell catalyst according to claim 2, characterized in that, The pore-forming agent is selected from at least one of polyvinylpyrrolidone, polyethylene glycol, and polyvinyl alcohol.

4. The porous noble metal core-shell catalyst according to claim 1, characterized in that, The noble metal nanoparticles include Pd and / or Pt, and the noble metal nanoparticles exist in a dispersed state in the core phase.

5. The porous noble metal core-shell catalyst according to any one of claims 1-4, characterized in that, The particle size of the noble metal nanoparticles is 1-20 nm.

6. The porous noble metal core-shell catalyst according to any one of claims 1-4, characterized in that, The hydrophilic polymer network layer comprises polyethylene glycol diacrylate, and / or the hydrophilic polymer matrix comprises dextran.

7. The porous noble metal core-shell catalyst according to claim 1, characterized in that, The core-shell structured microspheres have a diameter of 10-500 μm, wherein the core phase has a diameter of 8-400 μm.

8. A method for preparing a porous noble metal core-shell catalyst, characterized in that, Includes the following steps: (1) Preparation of noble metal nanoparticles; (2) Prepare a shell-phase polymer solution R1 containing a photoinitiator and a pore-forming agent, and stably disperse the noble metal nanoparticles in step (1) in a core-phase polymer solution R2, and select dimethyl silicone oil containing a surfactant as a continuous phase solution R3. (3) The shell-phase polymer solution R1, the core-phase polymer solution R2 and the continuous phase solution R3 are injected into the microfluidic chip for mixing. After being sheared by the continuous phase solution R3, the shell-phase polymer solution R1 and the core-phase polymer solution R2 form a core-shell microsphere with the core-phase polymer solution R2 wrapped by the shell-phase polymer solution R1. The core-shell microspheres are collected at the reaction outlet. (4) Irradiate the core-shell microspheres with blue light to induce cross-linking and curing of the shell layer, and collect the cured core-shell microspheres; (5) The solidified core-shell microspheres are washed repeatedly with deionized water to selectively remove the pore-forming agent from the solidified shell layer, thereby forming a continuous porous channel in situ through its thickness in the shell layer, and obtaining the porous noble metal core-shell catalyst.

9. The preparation method according to claim 8, characterized in that, The shell-phase polymer solution R1 and the core-phase polymer solution R2 constitute a two-aqueous-phase system. When the concentrations of the two incompatible polymers in the aqueous solvent exceed a threshold, liquid-liquid phase separation occurs inside the continuous phase solution R3, spontaneously forming the core-shell microspheres.

10. The preparation method according to claim 9, characterized in that, In step (2), the shell-phase polymer solution R1 has a mass concentration of 1-60 wt% for the shell-phase polymer, a mass concentration of 0.1-2 wt% for the photoinitiator, and a mass-volume concentration of 0.1-5 wt% for the pore-forming agent; the core-phase polymer solution R2 has a mass concentration of 1-40 wt% for the core-phase polymer, and a mass concentration of 0.1-1.0 wt% for the noble metal nanoparticles; 11. The preparation method according to claim 8, characterized in that, In step (3), the flow rate of the shell phase polymer solution R1 is 1-20 μL / min; the flow rate of the core phase polymer solution R2 is 1-10 μL / min; and the flow rate of the continuous phase solution R3 is 30-120 μL / min.

12. The application of a porous noble metal core-shell catalyst as described in any one of claims 1-7 in the hydrogenation reduction reaction of aromatic compounds.

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