Preparation method of metal catalyst material and application thereof in controllable degradation of polysaccharide

Abstract

The application discloses a preparation method of a metal catalyst material and application of the metal catalyst material in controllable degradation of polysaccharides, and the preparation comprises the following steps: mixing and reacting a ligand material with a metal ion solution, solid-liquid separation, washing, and drying; grinding the dried solid into powder, and then high-temperature calcining to obtain a metal monatomic catalyst, namely the metal catalyst material; or uniformly mixing and grinding the obtained metal monatomic catalyst with a metal organic framework material, and then high-temperature calcining to obtain a composite metal catalyst material. The metal catalyst material prepared by the application can make up for the limitations of Fenton oxidation principle in degrading polysaccharides, such as large iron consumption, strong pollution, and difficult control, and can avoid the adverse effects caused by the corrosiveness of hydrogen peroxide in actual production and operation. Different molecular weight polysaccharides can be obtained by adjusting the proportion and dosage of the metal catalyst material, the method can prepare polysaccharides with different molecular weights, and the prepared polysaccharides have good uniformity.

Description

Technical Field

[0001] This invention pertains to metal catalyst materials for polysaccharide degradation, specifically relating to a method for preparing a metal catalyst material and its application in the controlled degradation of polysaccharides. Background Technology

[0002] Polysaccharides are a class of complex carbohydrates formed by the linkage of 10 or more identical or different monosaccharide molecules through glycosidic bonds. They are mixtures of biological macromolecules with varying degrees of polymerization and multiple hydroxyl groups, widely distributed in nature, and are important structural components and energy storage forms in organisms. Polysaccharides possess various biological activities, including anti-tumor activity, immune enhancement, blood sugar reduction, anti-aging, and anticoagulation, and have broad application prospects in medicine and food. However, the complexity and diversity of polysaccharides limit their applications. For example, the complex and diverse monosaccharide composition, linkage positions, degree of polymerization, and structure make it difficult to define the structure-activity relationship of polysaccharides. Undegraded polysaccharides have large molecular weights, large molecular volumes, and poor water solubility, which hinders their biological activity in vivo. Studies have shown that obtaining low molecular weight polysaccharides through degradation can improve the biological activity and bioavailability of polysaccharides.

[0003] Currently, most research focuses on hydrolyzing polysaccharides into a series of intermediate products, or ultimately into small molecules such as monosaccharides and oligosaccharide fragments, through chemical degradation (acid hydrolysis, alkaline hydrolysis), biodegradation, and physical degradation, to facilitate the widespread application of polysaccharides in bioactivity. However, these methods still have some limitations. For example, acid hydrolysis generally uses strong acidic reagents such as hydrochloric acid, sulfuric acid, nitric acid, and trifluoroacetic acid to catalyze the hydrolysis of polysaccharides, which can easily lead to desulfurization of polysaccharides with sulfate groups on the side chains; alkaline hydrolysis of polysaccharides can only hydrolyze monosaccharides sequentially, and cannot hydrolyze polysaccharides from the intermediate glycosidic bonds to obtain oligosaccharides or oligosaccharides, resulting in low efficiency, and the hydrolysis process may be accompanied by structural changes; enzymatic hydrolysis is a relatively mild method, using specific enzymes to break the target glycosidic bonds and hydrolyze the polysaccharide, but because enzymes are unstable and easily affected by the surrounding storage environment and reaction conditions, and how to remove enzymes from the hydrolysate after polysaccharide degradation is also a complex issue. The problems, coupled with the high cost of commercially available enzymes and their high specificity and lack of broad applicability, limit their application in polysaccharide degradation. Physical methods such as radiation and ultrasound are difficult to implement. Introducing the Fenton oxidation principle into polysaccharide degradation systems is an effective approach, but traditional Fenton oxidation requires extremely acidic or weakly alkaline conditions. Acidic conditions easily lead to desulfurization risks, and the hydrolysis products are generally complex and lack homogeneity. Dilute alkalis cause environmental pollution, and acidic or alkaline conditions can easily damage equipment. Furthermore, the Fenton system requires temperatures above 55°C for the catalytic reaction to proceed. Therefore, this method has certain drawbacks. Thus, an effective polysaccharide degradation method is needed that can improve the bioactivity and bioavailability of polysaccharides while overcoming the aforementioned problems. Summary of the Invention

[0004] Purpose of the invention: To address the problems existing in the degradation of polysaccharides using current technologies, this invention provides a method for preparing a metal catalyst material. The metal catalyst material prepared by this invention overcomes the limitations of traditional Fenton oxidation principles in the degradation of polysaccharides, such as large iron consumption, strong pollution, and difficulty in control, and avoids the adverse effects of high concentrations of hydrogen peroxide corrosiveness during actual production and operation.

[0005] This invention utilizes metal-organic frameworks (MOFs) as catalysts for in-situ photocatalytic conversion of water and oxygen into hydrogen peroxide. Subsequently, MOFs are coupled with a metal catalyst to stably and continuously generate hydroxyl radicals at low hydrogen peroxide concentrations. These hydroxyl radicals then attack glycosidic bonds and degrade polysaccharides. By controlling the type and amount of metal catalyst, a series of uniform low-molecular-weight sugar chains with different molecular weights can be obtained, achieving the goal of efficient photocatalytic degradation of polysaccharides. Furthermore, the materials and methods of this invention effectively prevent polysaccharide desulfurization, obtaining structurally clear and molecularly uniform low-molecular-weight polysaccharides while maintaining the natural structure of the polysaccharides. The materials can be reused, reducing production costs. Moreover, the antioxidant activity of the degradation products obtained by this invention is improved compared to the undegraded polysaccharides.

[0006] The present invention also provides the aforementioned metal catalyst material and its applications.

[0007] Technical solution: To achieve the above objectives, the present invention provides a method for preparing a metal catalyst material, comprising the following steps:

[0008] (1) The ligand material is mixed with the metal ion solution and stirred to react, then the solid and liquid are separated, washed and dried;

[0009] (2) After the dried solid is ground into powder, it is calcined at high temperature to obtain a metal single-atom catalyst, which is the metal catalyst material.

[0010] (3) Alternatively, the metal single-atom catalyst obtained in step (2) can be mixed evenly with the metal-organic framework material and ground, and then calcined at high temperature to obtain a composite metal catalyst material.

[0011] The ligand material in step (1) is a composite of melamine, cyanuric acid and ammonium carbonate, and the mass ratio of melamine, cyanuric acid and ammonium carbonate is 3.5:3.5:1.8-2.2.

[0012] In step (1), the metal ions contain iron ions, copper ions, and zinc ions; the total elemental mass ratio of the iron ions and the copper and zinc ions is 1:0.25-1, and the elemental mass ratio of the copper and zinc ions is 1:0.15-1; the mass ratio of the metal ions to the ligand material is 1:1.5-25; and the total added concentration of metal ions in the metal ion solution is 12-30 g / L.

[0013] Furthermore, the addition of ligand 1,10-o-phenanthroline (CAS: 66-71-7) during the preparation process facilitates more uniform dispersion of the metal source; at the same time, the addition of ligand phenanthroline and ammonium carbonate gives the prepared catalyst better activity for degrading polysaccharides, with a mass ratio of phenanthroline to ammonium carbonate of 0.3-0.8:1.8-2.2.

[0014] In step (1), the reaction temperature for mixing the ligand material with the metal ion solution is 27-140℃, the rotation speed is 300-1000rpm, and the reaction time is 1.5-14h.

[0015] In step (2), the calcination temperature is 350-600℃ and the time is 3-8h.

[0016] In step (3), the metal-organic framework material is any one of the traditional metal-organic framework materials UIO66 series; the mass ratio of the metal single-atom catalyst to the metal-organic framework material it is composited with is 1:0.4-2; the calcination temperature in step (3) is 200-400℃ and the time is 2-4h.

[0017] Preferably, the metal-organic framework material is Ce-uio66-NH2.

[0018] The metal catalyst material prepared by the preparation method of the present invention is a binary heterogeneous composite material combining a metal single-atom catalyst and a metal-organic framework material.

[0019] The application of the metal catalyst material described in this invention in the controlled degradation of polysaccharides.

[0020] The specific process of the application is as follows:

[0021] (a) Mix the high molecular weight polysaccharide solution and the buffer solution to obtain a mixed solution;

[0022] (b) Add a metal single-atom catalyst or metal catalyst material to the mixed solution, and perform a shaking reaction or a shaking reaction under photocatalytic conditions to obtain a reaction solution;

[0023] (c) The reaction solution is subjected to solid-liquid separation, and the resulting liquid is a solution containing the degraded polysaccharide; wherein, by adjusting the proportion and amount of the metal catalyst material, polysaccharides of different molecular weights can be obtained.

[0024] In step (a), the high molecular weight polysaccharide is any one or more of chondroitin sulfate, hyaluronic acid, heparin, heparan sulfate, xanthan gum, and guar gum; the mass of the metal catalyst material is 1.5-80% of the mass of the polysaccharide; and the solvent is acetate-sodium acetate buffer, Tris-HCl buffer, phosphate buffer, PBS buffer, HEPES buffer, or water.

[0025] In step (b), the oscillation reaction is carried out at a rotation speed of 100-300 rpm for 10-30 h. The conditions for the photocatalytic oscillation reaction include: a 150-300W xenon lamp light source, a wavelength of 320-780 nm, a rotation speed of 100-300 rpm, and a time of 2-12 h.

[0026] Preferably, polysaccharides of different molecular weights can be obtained by adjusting the proportion and amount of the metal catalyst material, specifically:

[0027] The proportions between ligands in a metal single-atom catalyst are adjusted during the preparation of the metal catalyst material; and / or the proportions between metals in a metal single-atom catalyst are adjusted during the preparation of the metal catalyst material; and / or the proportions of metal ions and ligands in a metal single-atom catalyst are adjusted during the preparation of the metal catalyst material; and / or the proportions of metal ions and ligands in a binary heterogeneous composite material combining a metal single-atom catalyst and a metal-organic framework material are adjusted during the preparation of the metal catalyst material.

[0028] Specifically, the solid-liquid separation during the degradation process of this invention can be any solid-liquid separation method disclosed in the prior art, such as centrifugation, filtration, or vacuum filtration. Preferably, in order to improve the solid-liquid separation effect and reduce the time required for solid-liquid separation, in a specific embodiment of this invention, the solid-liquid separation method is centrifugation. The centrifugation conditions can also be determined by those skilled in the art based on actual conditions. To achieve better centrifugation results, preferably, the centrifugation conditions include: a rotation speed of 6000-15000 rpm and a time of 1-45 min. Specifically, in step (3), the reaction solution is centrifuged, and the resulting supernatant is a solution containing polysaccharides.

[0029] Preferably, the polysaccharide is a natural high-molecular-weight polysaccharide. Specifically, the natural high-molecular-weight polysaccharide is chondroitin sulfate, hyaluronic acid, heparin, xanthan gum, and guar gum, etc., extracted from natural sources. These natural polysaccharides have very high molecular weights, poor water solubility, low bioavailability, and are difficult for the human body to absorb.

[0030] Preferably, the solvent is an acetate-sodium acetate buffer, Tris-HCl buffer, phosphate buffer, HEPES buffer, or water. The pH of the solvent is 4-8. More preferably, the solvent is an acetate-sodium acetate buffer. Using an acetate-sodium acetate buffer with a pH of 7 allows for a faster reaction rate and milder reaction conditions, reducing equipment corrosion and preventing environmental pollution.

[0031] Preferably, the mass of the metal catalyst material accounts for 1.5-80% of the mass of the polysaccharide. Specifically, the mass of the metal catalyst material can be 1.5%, 8%, 10%, 3%, 50%, 60%, 80% of the mass of the polysaccharide in step (1), or any value between the aforementioned values. Under this preferred embodiment, the molecular weight of the obtained polysaccharide can be effectively controlled, and the use of metal catalyst material can be reduced. From the perspective of further improving polysaccharide uniformity and saving costs, preferably, the mass of the metal catalyst material accounts for 2-64% of the mass of the polysaccharide. Specifically, the mass of the metal catalyst material can be 2%, 10%, 20%, 30%, 40%, 50%, 64% of the mass of the polysaccharide, or any value between the aforementioned values.

[0032] To further improve the uniformity of the polysaccharide, preferably, the photocatalytic oscillatory reaction conditions involving the binary heterocomposite material combining the metal single-atom catalyst and the metal-organic framework material include: a 300W xenon lamp light source, a wavelength of 320-780nm, a rotation speed of 100-300rpm, and a time of 2-12h. More preferably, the photocatalytic oscillatory reaction conditions include: a 300W xenon lamp light source, a wavelength of 320-780nm, a rotation speed of 100-200rpm, and a time of 4-8h.

[0033] This invention enables the production of metal catalysts with polysaccharide degradation activity by adjusting the ratio and amount of metal single-atom catalyst ligands and metal ions in the metal catalyst material, as well as the type and amount of metal-organic framework materials compounded with them. Applying this material to different polysaccharide degradation systems yields polysaccharides with lower molecular weights. Furthermore, the method can produce relatively homogeneous polysaccharides.

[0034] The method described above is relatively simple and easy to implement, and the molecular weight of the obtained polysaccharide can be controlled by using different types of metal catalyst materials.

[0035] In the method for synthesizing materials according to the present invention, solid-liquid separation can be any solid-liquid separation method disclosed in the prior art, such as centrifugation, filtration, or vacuum filtration. Preferably, in order to improve the solid-liquid separation effect and reduce the time required for solid-liquid separation, in a specific embodiment of the present invention, the solid-liquid separation method is centrifugation. The centrifugation conditions can also be determined by those skilled in the art based on actual conditions. To achieve better centrifugation results, preferably, the centrifugation conditions include: a rotation speed of 5000-12000 rpm and a time of 1-10 min.

[0036] Preferably, the ligand material in the metal single-atom catalyst is a composite of melamine, cyanuric acid and ammonium carbonate, which can further improve the stability and porosity of the metal single-atom catalyst framework, thereby ensuring the long-term stability of the metal catalyst material.

[0037] More preferably, the mass ratio of melamine to cyanuric acid is 1:1, and the mass ratio of melamine to ammonium carbonate is 3.5:1.8-2.2. Specifically, it can be 3.5:1.8, 3.5:1.9, 3.5:2, 3.5:2.2, or any value between the aforementioned values. More preferably, the mass ratio of melamine to ammonium carbonate in the metal single-atom catalyst is 3.5:1.9-3.5:2.1.

[0038] To further improve the catalytic effect of the metal single-atom catalyst, preferably, the metal ions contain iron ions, copper ions, and zinc ions. Preferably, the total concentration of metal ions in the metal single-atom catalyst is 12-30 g / L, and the total elemental mass ratio of iron ions to copper and zinc ions is 1:0.25-1, specifically 1:0.25, 1:0.5, 1:0.8, 1:1, or any value between the aforementioned values. More preferably, the mass ratio of iron ions to the total mass of copper and zinc ions in the metal single-atom catalyst is 1:0.35-1:0.6. Preferably, the elemental mass ratio of copper and zinc ions is 1:0.15-1, specifically 1:0.15, 1:0.4, 1:0.7, 1:1, or any value between the aforementioned values. More preferably, the elemental mass ratio of copper and zinc ions is 1:0.15-0.7. The mass ratio of metal ions to ligand material in the metal single-atom catalyst is 1:1.5-25, specifically 1:1.5, 1:3, 1:4, 1:6, 1:10, 1:15, 1:25, or any value between the aforementioned values. More preferably, the mass ratio of metal ions to ligand material in the metal single-atom catalyst is 1:10-20. Under this condition, the metal active sites can be uniformly dispersed, improving the atomic utilization and density of the active centers, and effectively enhancing the catalytic activity of the metal single-atom catalyst material.

[0039] Preferably, combining a photocatalyst-active metal-organic framework (MOF) of the uio66 series with a synthesized metal single-atom catalyst to form a binary heterogeneous composite material can enhance material stability, improve photoinduced electron-hole separation efficiency, and broaden the absorption spectrum. More preferably, the MOF material is selected as Ce-uio66-NH2. Preferably, the mass ratio of the metal single-atom catalyst to the MOF material composited with it is 1:0.4-2, specifically 1:0.4, 1:1.5, 1:2, or any value between the aforementioned values. More preferably, the mass ratio of the metal single-atom catalyst to the MOF material composited with it is 1:0.5-1.5.

[0040] In order to further improve the porosity and specific surface area of ​​the metal catalyst material, preferably, in the preparation method of the metal catalyst, the reaction is a high-temperature reaction in a tubular furnace and a stirred reaction. The stirring reaction conditions in step (1) of synthesizing the metal single-atom catalyst include: temperature of 27-140℃, rotation speed of 300-1000rpm, and time of 1.5-14h; the high-temperature reaction conditions in the tubular furnace for synthesizing the metal single-atom catalyst are: temperature of 350-600℃ and time of 3-8h; the high-temperature reaction conditions in the tubular furnace involved in compositing the metal single-atom catalyst with the metal-organic framework material into a binary heterogeneous composite material are: temperature of 200-400℃ and time of 2-4h. More preferably, the stirring reaction conditions for synthesizing the metal single-atom catalyst include: a temperature of 27-60℃, a rotation speed of 500-8000 rpm, and a time of 3-12 h; the high-temperature reaction conditions in the tube furnace for synthesizing the metal single-atom catalyst are: a temperature of 350-550℃ and a time of 6-8 h; and the high-temperature reaction conditions in the tube furnace for compositing the metal single-atom catalyst with the metal-organic framework material into a binary heterogeneous composite material are: a temperature of 200-350℃ and a time of 3-4 h.

[0041] Preferably, the method for combining the metal single-atom catalyst with UIO66 to form a binary heterogeneous composite material includes: mixing the metal single-atom catalyst and UIO66 at a mass ratio of 1:0.5-1.5 evenly, grinding them with a mortar or grinder for 0.5-1 h, and then placing the evenly mixed powder in a nitrogen atmosphere at 300-350°C for 3-4 h.

[0042] Preferably, the method for combining the metal single-atom catalyst with Ce-uio66 to form a binary heterogeneous composite material includes: mixing the metal single-atom catalyst and Ce-uio66 at a mass ratio of 1:0.5-1.5 evenly, grinding them with a mortar and pestle or a grinder for 0.5-1 h, and then placing the evenly mixed powder in a nitrogen atmosphere at 300-350°C for 3-4 h.

[0043] Preferably, the method for combining the metal single-atom catalyst with Ce-uio66-NH2 to form a binary heterogeneous composite material includes: mixing the metal single-atom catalyst and Ce-uio66-NH2 at a mass ratio of 1:0.5-1.5 evenly, grinding them with a mortar and pestle or a grinder for 0.5-1 h, and then placing the evenly mixed powder in a nitrogen atmosphere at 300-350°C for 3-4 h.

[0044] The polysaccharide is at least one of natural polysaccharides such as chondroitin sulfate, hyaluronic acid, heparin, xanthan gum, and guar gum. Low molecular weight polysaccharides of different molecular weights are obtained by adjusting the proportion and amount of metal single-atom catalyst in the metal catalyst.

[0045] The polysaccharides prepared by the above preferred embodiments have low and uniform molecular weights, and can significantly improve the accuracy of the molecular weight of the prepared polysaccharides.

[0046] According to a particularly preferred embodiment of the present invention, a method for degrading naturally derived high molecular weight polysaccharides to obtain low molecular weight polysaccharides of different molecular weights by preparing a metal catalyst material in the case of photocatalysis is provided, comprising the following steps:

[0047] (1) Mix the polysaccharide with an acetate-sodium acetate buffer solution at pH 7 to obtain a mixed solution;

[0048] (2) Add 1.5-80% by mass of metal catalyst material of polysaccharide in the mixed solution to the mixed solution and carry out photocatalytic reaction (300W xenon lamp light source, wavelength of 320-780nm, rotation speed of 100-300rpm, time of 2-12h) to obtain reaction solution;

[0049] (3) Centrifuge the reaction solution to obtain the supernatant, which is the solution containing the degraded polysaccharide;

[0050] The polysaccharide is at least one of natural polysaccharides such as chondroitin sulfate, hyaluronic acid, heparin, xanthan gum, and guar gum. Low molecular weight polysaccharides of different molecular weights are obtained by adjusting the proportion of the metal catalyst material.

[0051] Methods for adjusting the type of the metal catalyst material include:

[0052] In the preparation of metal single-atom catalyst materials, the ratio between the ligands of the metal single-atom catalyst is adjusted. The ligand material is a composite of melamine, cyanuric acid, and ammonium carbonate, with a mass ratio of melamine to cyanuric acid of 1:1 and a mass ratio of melamine to ammonium carbonate of 3.5:1.9-2.1. And / or, in the preparation of metal single-atom catalyst materials, the type and ratio of metals in the metal single-atom catalyst are adjusted. Based on iron, copper and zinc are added respectively to obtain three types of metal single-atom catalysts: monometallic Fe single-atom catalysts (mono-SACs), bimetallic Fe and Cu single-atom catalysts (bi-SACs), and trimetallic Fe, Cu, and Zn single-atom catalysts (tri-SACs). Comparison shows that tri-SACs have the best catalytic activity. Based on this, the metal ratio in the material is adjusted, and the total concentration of metal ions added in the metal single-atom catalyst is 12-30 g / L. L, wherein the total elemental mass ratio of the iron ions and the copper and zinc ions is 1:0.35-0.6, and the elemental mass ratio of the copper and zinc ions is 1:0.15-0.7; and / or the ratio of metal ions to ligands in the metal single-atom catalyst is adjusted during the preparation of the metal single-atom catalyst material, wherein the mass ratio of the metal ions to the ligand material is 1:1.5-20; and / or a metal-organic framework material is attached to the surface of the metal single-atom catalyst to construct a binary heterogeneous composite material, wherein the metal-organic framework material is of the uio66 series, including uio66, Ce-uio66, Ce-uio66-NH2, and other traditional metal-organic framework materials with photocatalytic properties; and / or the ratio of the metal single-atom catalyst and the metal-organic framework material is adjusted during the preparation of the binary heterogeneous composite material, wherein the mass ratio of the metal single-atom catalyst to the metal-organic framework material composited therewith is 1:0.5-1.5.

[0053] The polysaccharides prepared by the above preferred embodiments have low and uniform molecular weights, and can significantly improve the accuracy of the molecular weight and catalytic efficiency of the prepared polysaccharides.

[0054] This invention synthesizes metal catalysts by adjusting the ratio of metals and ligands and adding MOFs to form binary heterogeneous composite materials. These catalysts are then applied to polysaccharide degradation systems to degrade different types of polysaccharides, yielding various low-molecular-weight polysaccharides. Physiologically active polysaccharides can be obtained through simple centrifugation and alcohol precipitation dialysis. Furthermore, the synthesized metal catalysts are environmentally friendly, possess high specific surface area, are structurally stable, and can be reused. The reactions can proceed under relatively mild conditions, reducing corrosion and wear on equipment and lowering reaction costs. The materials and methods of this invention can prepare low-molecular-weight polysaccharides of different molecular weights, and the prepared polysaccharides exhibit good uniformity and activity.

[0055] This invention utilizes metal-organic frameworks (MOFs) as artificial photosynthetic catalysts in a neutral buffer solution under photocatalytic conditions to in-situ photocatalyze the conversion of water and oxygen into hydrogen peroxide. Subsequently, it is coupled with a metal single-atom catalyst to stably and continuously generate hydroxyl radicals from the hydrogen peroxide at low hydrogen peroxide concentrations. These hydroxyl radicals then attack glycosidic bonds and degrade polysaccharides. By controlling the type and amount of metal catalyst, a series of uniform low-molecular-weight sugar chains with different molecular weights can be obtained, achieving the goal of efficiently degrading polysaccharides through photocatalysis.

[0056] The metal catalyst prepared by this invention can effectively prevent polysaccharide desulfurization, maintain the natural structure of polysaccharides while obtaining low molecular weight polysaccharides with clear structures and uniform molecular weight; it enables material reuse; reduces production costs; and is environmentally friendly. No additional hydrogen peroxide is required. Traditional oxidation methods that add high concentrations of hydrogen peroxide can easily damage the polysaccharide structure and also pose safety risks. Furthermore, if only high concentrations of hydrogen peroxide are added for degradation, the reaction needs to be carried out at very high temperatures, resulting in low catalytic efficiency. This also leads to the loss of some functional groups from the polysaccharide chains. Traditional Fenton oxidation is carried out under extreme pH conditions and requires high concentrations of heavy metal Fe and Cu ions to catalyze the decomposition of hydrogen peroxide to generate hydroxyl radicals that attack polysaccharides, leading to polysaccharide degradation. The large amount of free metal ions can pollute the environment. However, the single-atom catalyst material in the composite material of this invention can fix metal ions. In addition, since only a small amount of metal source is added during synthesis, the metal active sites are uniformly dispersed, which can improve the atom utilization rate. Furthermore, compared with the traditional method, which uses heavy metal ions and is difficult to handle and prone to pollution, this material can be disposed of simply by centrifugation and filtration without causing environmental pollution.

[0057] The present invention provides a binary heterogeneous composite material combining a metal single-atom catalyst and a metal-organic framework material, which enables the degradation of polysaccharides through photocatalysis without the need for hydrogen peroxide, and reduces the reaction time.

[0058] The polysaccharides degraded in this invention are high molecular weight polysaccharides, characterized by high viscosity and low solubility. These properties limit their active expression. Excessively high molecular weight hinders their permeability to cell membranes, resulting in incomplete absorption and low bioavailability. Degrading high molecular weight polysaccharides to obtain low molecular weight polysaccharides increases their solubility, thus improving bioavailability. Furthermore, high molecular weight polysaccharides have complex structures and poor homogeneity, affecting their functional specificity and limiting further research into their structure-activity relationship. Secondly, high molecular weight polysaccharides exhibit strong hydrogen bonding within and between molecules. With increasing degradation, more hydrogen bonds are broken, exposing more hydroxyl groups, making them more susceptible to attack by hydroxyl free radicals. For chondroitin sulfate, its antioxidant effect mainly relies on two steps: firstly, the aldehyde carboxyl groups and sulfate groups on its backbone can bind with Fe... 2+ and Cu 2+ Chelation inhibits the generation of free radicals; secondly, free radicals can be eliminated by the hemiacetal hydroxyl groups at the reducing end of chondroitin sulfate. The smaller the molecular weight of the polysaccharide chain, the more hemiacetal hydroxyl groups it has at the reducing end for the same mass, and therefore it has better antioxidant activity.

[0059] Compared to conventional high molecular weight heparin, low molecular weight heparin has advantages such as better absorption after injection, longer half-life, higher bioavailability, and fewer adverse bleeding reactions. Its anticoagulant effect is roughly the same or better, but its antithrombotic effect is superior. Furthermore, compared to animal-derived heparin, low molecular weight heparin has higher safety, binds less to platelet factor 4 (PF4), and has a lower risk of HIT (heparin-induced thrombocytopenia). Degrading high molecular weight hyaluronic acid into low molecular weight hyaluronic acid can reduce its viscosity and lubricity, enhancing its permeability to cells. Molecular weight is an important parameter that significantly affects the activity of hyaluronic acid; different molecular weights of hyaluronic acid can even exhibit diametrically opposed activities. Low molecular weight hyaluronic acid promotes angiogenesis and wound healing. While high molecular weight hyaluronic acid cannot penetrate the epidermis into the dermis, low molecular weight hyaluronic acid can penetrate into the dermis, scavenging oxygen free radicals, protecting granulation tissue from oxygen free radical damage, and promoting wound healing. For xanthan gum and guar gum, polysaccharides with molecular weights ranging from several million to tens of millions, the primary significance of degradation lies in reducing their viscosity. Xanthan gum and guar gum are currently widely used in oil extraction processes. Xanthan gum is a highly efficient, high-quality, and environmentally friendly oil drilling mud additive with a wide range of applications. However, due to its regular helical structure and steric hindrance from its side chains, it exhibits strong resistance to temperature, acids, alkalis, and salts, remaining relatively stable within a pH range of 2-10. This significantly improves mud permeability and the ability to suspend solids, reducing drilling pressure, stabilizing the wellbore, and minimizing damage to oil reservoirs, thereby significantly improving the efficiency of drilling, well workover, and well completion operations. However, after extraction, these high-viscosity polysaccharides are difficult to process, and the costs of oil transportation and product purification are very high. Therefore, the degradation of these polysaccharides using the materials of this invention yields low-molecular-weight polysaccharides with significantly reduced viscosity, which is beneficial for subsequent processing. Furthermore, for high-molecular-weight polysaccharides, reduced molecular weight significantly improves solubility, making them easier for the human body to absorb.

[0060] This invention utilizes a specially prepared metal catalyst material to achieve universal degradation of polysaccharides without the need for hydrogen peroxide. It not only achieves efficient degradation of polysaccharides, but also significantly improves solubility and enhances biomembrane permeability after the molecular weight is reduced, making them easier for the human body to absorb. It can also be applied to various polysaccharide systems. The post-processing method is convenient, environmentally friendly, and the material can be repeatedly recycled.

[0061] In summary, the present invention utilizes a metal single-atom catalyst prepared from a specific trimetallic material as a metal catalyst material to achieve efficient degradation of polysaccharides, thereby reducing their molecular weight. However, this requires the addition of a certain amount of hydrogen peroxide solution. Furthermore, the metal catalyst material formed by combining specific metal-organic framework materials exhibits even more significant effects in degrading polysaccharides, with lower molecular weight, improved antioxidant activity, and avoids the need for the addition of hydrogen peroxide solution.

[0062] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0063] This invention utilizes specific trimetallic preparations of single-atom metal catalysts, or adjusts the metal-ligand ratio and adds MOFs to construct binary heterogeneous composite materials to synthesize metal catalyst materials. These metal catalyst materials are environmentally friendly, possess high specific surface area, exhibit structural stability, are reusable, and can proceed under relatively mild conditions, reducing corrosion and wear on equipment and lowering reaction costs. The metal catalysts prepared by this invention can produce degradable polysaccharides of different molecular weights, and the prepared polysaccharides exhibit good uniformity and activity.

[0064] The metal catalyst prepared in this invention can effectively prevent polysaccharide desulfurization during polysaccharide degradation, maintaining the natural structure of the polysaccharide while obtaining low molecular weight polysaccharides with clear structure and uniform molecular weight. It also enables material reuse, reducing production costs and is environmentally friendly. More importantly, it eliminates the need for additional hydrogen peroxide during degradation, avoiding the damage to the polysaccharide structure and potential safety issues associated with adding high concentrations of hydrogen peroxide in traditional oxidation methods.

[0065] The metal catalyst prepared in this invention uses a single-atom catalyst material to immobilize metal ions. Furthermore, the metal ion doping level is low during synthesis, and the active metal sites are uniformly dispersed, improving atom utilization. In addition, traditional heavy metal ions are difficult to handle and prone to contamination, while the material of this invention can be removed by centrifugation and filtration. Attached Figure Description

[0066] Figure 1 It is a structural diagram of polysaccharides, including chondroitin sulfate, heparin, hyaluronic acid, xanthan gum, and guar gum;

[0067] Figure 2 These are SEM images of tri-SACs;

[0068] Figure 3 These are TEM spectra of tri-SACs and tri-S-Ce-uio66-NH2;

[0069] Figure 4 This is a schematic diagram of the chondroitin sulfate degradation reaction catalyzed by tri-SACs;

[0070] Figure 5 This is a schematic diagram comparing the molecular weights of low molecular weight chondroitin sulfate CS3, CS2, and CS1 obtained by catalytic degradation of chondroitin sulfate by tri-SACs, bi-SACs, and mono-SACs with that of undegraded chondroitin sulfate CS0.

[0071] Figure 6 This is a schematic diagram comparing the molecular weights of low molecular weight chondroitin sulfate CS3, CS3*, CS-1, CS-2, and CS-3 obtained by catalytic degradation of chondroitin sulfate using tri-SACs (ordinary reaction), tri-SACs (photocatalysis), tri-S-uio66 (photocatalysis), tri-S-Ce-uio66 (photocatalysis), and tri-S-Ce-uio66-NH2 (photocatalysis).

[0072] Figure 7 These are comparative gel images showing the effects of tri-SACs on the degradation of chondroitin sulfate when using different buffer systems;

[0073] Figure 8 This is a comparison chart of the total antioxidant capacity of CS0, CS3, CS3*, CS-1, CS-2, and CS-3;

[0074] Figure 9 This is a comparison chart of the molecular weights of low molecular weight polysaccharides obtained by degrading chondroitin sulfate, hyaluronic acid, and heparin using tri-S-Ce-uio66-NH2.

[0075] Figure 10 This is a comparison chart of the molecular weights of low molecular weight polysaccharides obtained by degrading xanthan gum and guar gum using tri-S-Ce-uio66-NH2;

[0076] Figure 11 This is a schematic diagram comparing the molecular weights of chondroitin sulfate obtained after reusing tri-S-Ce-uio66-NH2 three times.

[0077] Figure 12 This is a comparison chart of the total antioxidant capacity of HA0 and HA1;

[0078] Figure 13 This is a comparison chart of the anticoagulant activities of HP0 and HP1;

[0079] Figure 14 This is a comparison chart of the total antioxidant capacity of CS0, CS1, CS2, and CS3;

[0080] Figure 15 The images are gel images verifying the effects of three tri-SACs on chondroitin sulfate degradation: simultaneous addition of phenanthroline and ammonium carbonate, no addition of phenanthroline and ammonium carbonate, and addition of only phenanthroline without ammonium carbonate.

[0081] Figure 16 This is a comparison of glucomannan strips after chondroitin sulfate was degraded using different amounts of tri-S-Ce-uio66-NH2. Detailed Implementation

[0082] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0083] Unless otherwise specified, all materials and reagents used in the embodiments of this invention are commercially available. Experimental methods not specifically described in the embodiments are generally performed under standard conditions or as recommended by the manufacturer.

[0084] In the following embodiments, the X-ray diffractometer was purchased from Rigaku Corporation, model Smartlab; the scanning electron microscope was purchased from Zeiss Corporation, model Sigma-300; the high-performance liquid chromatograph was purchased from Agilent Technologies, model Agilent 1260-LC; and the high-performance liquid chromatograph-18-angle laser light scattering system was purchased from Wyatt Corporation, model DAWN HELEOS II.

[0085] The polysaccharides in the examples are all commercially available, and their structures are as follows: Figure 1 As shown.

[0086] Example 1

[0087] 4.2132 g of ferric nitrate nonahydrate, 0.6330 g of copper nitrate trihydrate, 0.3807 g of zinc nitrate heptahydrate, and 0.5 g of 1,10-phenanthroline were dissolved in 40 mL of ultrapure water and stirred at 300 rpm for 20 min to obtain solution A. 3.5 g of melamine and 1 g of ammonium carbonate were dissolved in 120 mL of dimethyl sulfoxide to obtain solution B. 3.5 g of cyanuric acid and 1 g of ammonium carbonate were dissolved in 120 mL of dimethyl sulfoxide to obtain solution C. Under the conditions of 40℃ oil bath and 400 rpm, solution A was first slowly added dropwise to solution B and stirred for 45 min. Then, solution C was slowly added dropwise to the mixture of solutions A and B and stirred for another 45 min. After the reaction was completed, the precipitate was centrifuged at 6000 rpm for 7 min, and washed twice with water. After drying the precipitate, it was reacted in a tube furnace at 400 °C in a N2 atmosphere for 4 h to obtain tri-metallic single-atom catalyst materials tri-SACs.

[0088] After characterization, it was observed that the material prepared by this invention is a near-spherical micron-sized material with a diameter of about 6 micrometers. Figure 2 ), thermogravimetric results ( Figure 3 This indicates that the catalyst has good thermal stability.

[0089] Example 2

[0090] 0.42 g zirconium tetrachloride, 0.3 g terephthalic acid, and 6 mL acrylic acid were mixed and sonicated in 50 mL dimethylformamide (DMF) for 0.5 h. The mixture was then transferred to a Teflon reactor and reacted at 120 °C for 48 hours, followed by cooling to room temperature. The mixture was centrifuged at 8000 rpm for 5 min, washed twice with DMF and methanol respectively, and dried in a 100 °C oven for 12 h to obtain uio66.

[0091] 1g of the tri-SACs prepared in Example 1 was mixed with 0.5g of uio66 and ground evenly with a mortar and pestle or a grinder for 0.5h. The evenly mixed powder was then placed in an Ar atmosphere at 350℃ and reacted for 4h to obtain the metal catalyst material tri-S-uio66.

[0092] Example 3

[0093] 0.2 g of 1,4-phthalic acid was dissolved in 60 mL of DMF. The solution was heated to 100 °C, and 25 mL of 0.5 M cerium ammonium nitrate solution was slowly added. The mixture was stirred continuously for 0.5 h. The resulting mixture was centrifuged at 8000 rpm for 5 min to obtain a solid precipitate. The precipitate was washed twice with DMF and then twice with acetone. Finally, the powder was dried in an oven at 80 °C for 12 h to obtain Ce-uio66.

[0094] 1g of the tri-SACs prepared in Example 1 was mixed with 0.5g of Ce-uio66 and ground in a mortar or grinder for 0.5h. The mixed powder was then placed in an Ar atmosphere at 350℃ and reacted for 4h to obtain the metal catalyst material tri-S-Ce-uio66.

[0095] Example 4

[0096] Take 0.0816g of Ce-uio66 synthesized in Example 3 and 0.1811g of 2-aminoterephthalic acid and dissolve them in 25mL of methanol solution. Stir for 0.5h. Centrifuge the resulting mixture at 8000rpm for 5min to obtain a solid precipitate. Wash it twice with DMF and then twice with ethanol. Finally, dry the powder in an 80°C oven for 12h to obtain Ce-uio66-NH2.

[0097] 1g of the tri-SACs prepared in Example 1 was mixed with 0.5g of Ce-uio66-NH2 and ground in a mortar or grinder for 0.5h. The mixed powder was then placed in an Ar atmosphere at 350℃ and reacted for 4h to obtain the metal catalyst material tri-S-Ce-uio66-NH2.

[0098] Example 5

[0099] (1) Take 2.5 mL of acetate-sodium acetate buffer (100 mM) with pH 6 into a test tube, add 2 mL of 0.05 g / mL chondroitin sulfate and 2 mL of 30% hydrogen peroxide solution respectively, and mix the three together to obtain a mixed solution.

[0100] (2) Add 3.5 mL of an acetate-sodium acetate buffer solution (100 mM) containing 0.002 g / mL of the metal single-atom catalyst tri-SACs obtained in Example 1 at pH 6 to the solution, and shake at 42 °C and 150 rpm for 24 h to obtain the reaction solution. The reaction mechanism is described in [reference needed]. Figure 4 ;

[0101] (3) Centrifuge the reaction solution (8000 rpm, 10 min) and the resulting supernatant is a solution containing low molecular weight chondroitin sulfate.

[0102] The molecular weight of the obtained chondroitin sulfate was analyzed by high performance liquid chromatography-evaporative light scattering detector (HPLC-ELSD). The chromatographic column was a Shodex Ohpak SB-802.5HQ, the mobile phase was sodium nitrate, the flow rate was 0.6 mL / min, and the column temperature was 35 °C. The weight-average molecular weight of the obtained chondroitin sulfate polysaccharide CS3 was 4923 Da (see [reference]). Figure 5 , Figure 6 ).

[0103] Further, in step (2), the same method was used, with 1 mL of 30% hydrogen peroxide solution, a 300W xenon lamp light source, a wavelength of 320-780 nm, and a rotation speed of 150 rpm for 4 h of photocatalytic reaction. After centrifugation, the weight average molecular weight of CS3* was measured to be approximately 4892 Da.

[0104] Example 6

[0105] (1) Take 6.8 mL of acetate-sodium acetate buffer (100 mM) with pH 7 into a test tube, add 2 mL of 0.05 g / mL chondroitin sulfate, and mix them evenly to obtain a mixed solution;

[0106] (2) Add 1.2 mL of an acetate-sodium acetate buffer solution (100 mM) containing 0.002 g / mL of the metal catalyst material tri-S-uio66 obtained in Example 2 at pH 7 to the solution, and react for 4 h under photocatalytic conditions of 300 W xenon lamp light source, wavelength of 320-780 nm and rotation speed of 150 rpm to obtain the reaction solution;

[0107] (3) Centrifuge the reaction solution (8000 rpm, 10 min) and the resulting supernatant is a solution containing low molecular weight chondroitin sulfate.

[0108] The molecular weight of the obtained chondroitin sulfate was analyzed by high performance liquid chromatography-evaporative light scattering detector (HPLC-ELSD). The chromatographic column was a Shodex Ohpak SB-802.5HQ, the mobile phase was sodium nitrate, the flow rate was 0.6 mL / min, and the column temperature was 35 °C. The weight-average molecular weight of the obtained chondroitin sulfate polysaccharide CS-1 was 4720 Da (see [reference]). Figure 6 ).

[0109] Example 7

[0110] Low molecular weight chondroitin sulfate was prepared according to the method of Example 6, except that in step (2), 1.2 mL of the 0.002 g / mL metal catalyst material tri-S-Ce-uio66 prepared in Example 3 was added;

[0111] The molecular weight of the obtained chondroitin sulfate was analyzed by high-performance liquid chromatography with evaporative light scattering detector. The chromatographic column was a Shodex Ohpak SB-802.5HQ, the mobile phase was sodium nitrate, the flow rate was 0.6 mL / min, and the column temperature was 35℃. The weight-average molecular weight of the obtained chondroitin sulfate polysaccharide CS-2 was 4532 Da (see [link to chromatographic analysis]). Figure 6 ).

[0112] Example 8

[0113] Low molecular weight chondroitin sulfate was prepared according to the method of Example 6, except that in step (2), 1.2 mL of the 0.002 g / mL metal catalyst material tri-S-Ce-uio66-NH2 prepared in Example 4 was added;

[0114] The molecular weight of the obtained chondroitin sulfate was analyzed by high performance liquid chromatography-evaporative light scattering detector (HPLC-ELSD). The chromatographic column was a Shodex Ohpak SB-802.5HQ, the mobile phase was sodium nitrate, the flow rate was 0.6 mL / min, and the column temperature was 35 °C. The weight-average molecular weight of the obtained chondroitin sulfate polysaccharide CS-3 was 4408 Da (see [reference]). Figure 6 ).

[0115] As can be seen from Examples 5-8 above, the chondroitin sulfate polysaccharide obtained by Example 8 has the lowest weight-average molecular weight, effectively improved solubility, and is more easily absorbed by the human body.

[0116] Example 9

[0117] First, the metal single-atom catalyst tri-SACs from Example 1 were divided into four portions and incubated in HEPES buffer (100 mM), acetate-sodium acetate buffer (100 mM), Tris-HCl buffer (100 mM), and PBS buffer (100 mM) at pH 6, respectively. The buffers in the reaction system of Example 5 were replaced with the corresponding buffers mentioned in this example. Then, low molecular weight chondroitin sulfate was prepared according to the method of Example 5.

[0118] The obtained supernatant was subjected to a 22% sugar gum test. The final results are shown in [reference needed]. Figure 7 The distribution range of the bands proves that the acetate-sodium acetate buffer is the most suitable buffer for the degradation system.

[0119] Example 10

[0120] The three polysaccharides CS-1, CS-2, and CS-3 obtained in Examples 6, 7, and 8 were subjected to alcohol precipitation, dialysis, and lyophilization to obtain purified polysaccharides CS-1, CS-2, and CS-3. Total antioxidant capacity was tested by adding 20 μL of each of the three polysaccharide solutions (0.005 g / mL) to 180 μL of FRAP working solution, reacting at room temperature for 0.5 h, and measuring the absorbance at 593 nm. The total antioxidant capacity of CS-3 was taken as 100%. Under the same experimental and testing conditions, the total antioxidant capacity of the three polysaccharide solutions, undegraded chondroitin sulfate CS0, and polysaccharide CS3 prepared in Example 5 were compared. The results are shown in [link to results]. Figure 8 The polysaccharide obtained in Example 8 showed the best overall antioxidant effect. Therefore, tri-S-Ce-uio66-NH2 was used as the optimal catalyst in the degradation system of other polysaccharides.

[0121] Example 11

[0122] (1) Take 2.8 mL of acetate-sodium acetate buffer (100 mM) with pH 7 into a test tube, add 5 mL of 0.012 g / mL hyaluronic acid, and mix them evenly to obtain a mixed solution;

[0123] (2) Add 2.2 mL of 100 mM acetate-sodium acetate buffer solution (pH 7) containing 0.002 g / mL of tri-S-Ce-uio66-NH2 prepared in Example 4, and react for 5 h under photocatalytic conditions of 300 W xenon lamp light source, wavelength of 320-780 nm and rotation speed of 150 rpm to obtain reaction solution;

[0124] (3) Centrifuge the reaction solution (8000 rpm, 10 min) and the resulting supernatant is a solution containing low molecular weight hyaluronic acid.

[0125] The molecular weight of the obtained hyaluronic acid was analyzed by high-performance liquid chromatography with evaporative light scattering detector. The chromatographic column was a Shodex Ohpak SB-804HQ, the mobile phase was sodium nitrate, the flow rate was 0.6 mL / min, and the column temperature was 35℃. The average molecular weight of the obtained hyaluronic acid polysaccharide HA1 was 12.36 kDa, which was significantly lower than the original average molecular weight of hyaluronic acid HA0 (50 kDa) (see [link to relevant documentation]). Figure 9 Compared to high molecular weight hyaluronic acid, low molecular weight hyaluronic acid has lower viscosity, better skin permeability, stronger antioxidant activity, and stronger cell activity.

[0126] Example 12

[0127] (1) Take 5 mL of acetate-sodium acetate buffer (100 mM) with pH 7 into a test tube, add 2 mL of 0.05 g / mL heparin, and mix them thoroughly to obtain a mixed solution;

[0128] (2) Add 3 mL of 100 mM acetate-sodium acetate buffer solution (pH 7) containing 0.002 g / mL of tri-S-Ce-uio66-NH2 prepared in Example 4, and react for 4 h under photocatalytic conditions of 300 W xenon lamp light source, wavelength of 320-780 nm and rotation speed of 150 rpm to obtain reaction solution;

[0129] (3) Centrifuge the reaction solution (8000 rpm, 10 min) and the resulting supernatant is the solution containing low molecular weight heparin.

[0130] The molecular weight of the obtained heparin was analyzed by high-performance liquid chromatography with evaporative light scattering detector. The chromatographic column was a Shodex Ohpak SB-804HQ, the mobile phase was sodium nitrate, the flow rate was 0.6 mL / min, and the column temperature was 35 °C. The average molecular weight of the obtained heparin polysaccharide HP1 was 6823 Da, which was significantly lower than that of the original heparin HP0, which had an average molecular weight of 20 kDa (see [link to article]). Figure 9 ).

[0131] Example 13

[0132] (1) Soak 50 mg xanthan gum in 10 mL of ultrapure water, take 4.8 mL of 100 mM acetate-sodium acetate buffer solution with pH 7 in a test tube, add 3 mL of xanthan gum solution with a mass fraction of 0.5% and mix them evenly to obtain a mixed solution.

[0133] (2) Add 2.2 mL of 100 mM acetate-sodium acetate buffer solution (pH 7) containing 0.002 g / mL of tri-S-Ce-uio66-NH2 prepared in Example 4, and react for 5 h under photocatalytic conditions of 300 W xenon lamp light source, wavelength of 320-780 nm and rotation speed of 150 rpm to obtain reaction solution;

[0134] (3) Centrifuge the reaction solution (8000 rpm, 10 min) and the supernatant obtained is the degraded xanthan gum solution;

[0135] The molecular weight of the obtained heparin polysaccharide was analyzed by high-performance liquid chromatography-18-angle laser light scattering. The chromatographic column was a GelGuard gel column, the mobile phase was tetrahydrofuran, the flow rate was 1 mL / min, and the column temperature was 25℃. The average molecular weight of the obtained xanthan gum polysaccharide XG1 was 302.8 kDa, which was significantly lower than that of the original xanthan gum XG0 (average molecular weight 1500 kDa). A significant decrease in solution viscosity was also observed (see [link to relevant documentation]). Figure 10 ).

[0136] Example 14

[0137] (1) Soak 50 mg of guar gum in 10 mL of ultrapure water, take 4.8 mL of 100 mM acetate-sodium acetate buffer solution with pH 7 in a test tube, add 3 mL of xanthan gum solution with a mass fraction of 0.5% and mix them evenly to obtain a mixed solution.

[0138] (2) Add 2.2 mL of 0.002 g / mL tri-S-Ce-uio66-NH2 acetate-sodium acetate buffer (100 mM) with pH 7 prepared in Example 4 to the solution, and react for 5 h under photocatalytic conditions of 300 W xenon lamp light source, wavelength of 320-780 nm and rotation speed of 150 rpm to obtain reaction solution;

[0139] (3) The reaction solution is centrifuged (8000 rpm, 10 min) and the supernatant obtained is the degraded guar gum solution;

[0140] The molecular weight of the obtained heparin polysaccharide was analyzed by high-performance liquid chromatography-18-angle laser light scattering. The chromatographic column was a GelGuard gel column, the mobile phase was tetrahydrofuran, the flow rate was 1 mL / min, and the column temperature was 25℃. The average molecular weight of the obtained xanthan gum polysaccharide GG1 was 67.8 kDa, which was significantly lower than that of the original xanthan gum GG0 (average molecular weight 220 kDa), and the solution viscosity also decreased significantly (see [reference]). Figure 10 ).

[0141] Example 15

[0142] Low molecular weight chondroitin sulfate was prepared according to the method of Example 8, except that the precipitate after centrifugation in step (3) was recovered, washed three times with ultrapure water and dried, and the degradation reaction was repeated according to the reaction ratio of Example 8. This was repeated three times, and the material was used to cycle the degradation reaction 4 times to obtain 4 polysaccharides, which were named CS-3, 1-CS-3, 2-CS-3 and 3-CS-3 respectively.

[0143] The molecular weight of the obtained chondroitin sulfate was analyzed by high-performance liquid chromatography with evaporative light scattering detector. The chromatographic column was a Shodex Ohpak SB-802.5HQ, the mobile phase was sodium nitrate, the flow rate was 0.6 mL / min, and the column temperature was 35℃. The weight-average molecular weights of the obtained chondroitin sulfate polysaccharides were 4408 Da for CS-3, 4492 Da for 1-CS-3, 4984 Da for 2-CS-3, and 5009 Da for 3-CS-3 (see [reference missing]). Figure 11 The results showed that the material still had a good degradation effect after multiple cycles.

[0144] Example 16

[0145] The polysaccharide HA1 obtained in Example 11 was subjected to alcohol precipitation, dialysis, and lyophilization to obtain purified polysaccharide HA1. Its total antioxidant capacity was tested against undegraded HA0. 20 μL of a 0.005 g / mL polysaccharide solution was added to 180 μL of FRAP working solution, and the reaction was carried out at room temperature for 0.5 h. The absorbance at 593 nm was measured. The total antioxidant capacity of HA1 was taken as 100%, and the total antioxidant capacity of the two was compared. The results are shown in [link to results]. Figure 12 The total antioxidant capacity of HA1 was significantly improved.

[0146] Example 17

[0147] The polysaccharide HP1 obtained in Example 12 was subjected to alcohol precipitation, dialysis, and freeze-drying to obtain purified polysaccharide HA1, which was then subjected to anticoagulant activity testing with undegraded HAO.

[0148] 90 μL of plasma, 10 μL of polysaccharide sample, and 100 μL of APTT reagent were incubated at 37 °C. After stirring for 3 minutes, 100 μL of 2.5 × 10⁻⁶ ppm was added. –2 mol / L –1 CaCl2 was used to measure clotting time using an automated coagulation analyzer. Results are shown below. Figure 13 HP1 significantly enhances clotting time and greatly improves anticoagulant activity.

[0149] Comparative Example 1

[0150] 4.2132 g of ferric nitrate nonahydrate and 0.5 g of 1,10-o-phenanthroline were dissolved in 40 mL of ultrapure water and stirred at 300 rpm for 20 min to obtain solution A. 3.5 g of melamine and 1 g of ammonium carbonate were dissolved in 120 mL of dimethyl sulfoxide to obtain solution B. 3.5 g of cyanuric acid and 1 g of ammonium carbonate were dissolved in 120 mL of dimethyl sulfoxide to obtain solution C. Solution A was slowly added dropwise to solution B and stirred for 45 min. Then, solution C was slowly added dropwise to the mixture of solutions A and B and stirred for another 45 min. After the reaction was completed, the mixture was centrifuged at 6000 rpm for 7 min, the precipitate was recovered and washed twice with water, and the precipitate was dried. The mixture was then reacted in a tube furnace at 400 °C for 4 h under a N2 atmosphere to obtain the monometallic single-atom catalyst material mono-SACs.

[0151] (1) Take 2.5 mL of acetate-sodium acetate buffer (100 mM) with pH 6 into a test tube, add 2 mL of 0.05 g / mL chondroitin sulfate and 2 mL of 30% hydrogen peroxide solution respectively, and mix the three together to obtain a mixed solution.

[0152] (2) Add 3.5 mL of 0.02 g / mL of the metal single-atom catalyst mono-SACs obtained in Comparative Example 1 above to the solution, and shake at 42 °C and 150 rpm for 24 h to obtain the reaction solution;

[0153] (3) Centrifuge the reaction solution (8000 rpm, 10 min) and the resulting supernatant is a solution containing low molecular weight chondroitin sulfate.

[0154] The molecular weight of the obtained chondroitin sulfate was analyzed by high performance liquid chromatography-evaporative light scattering detector (HPLC-ELSD). The chromatographic column was a Shodex Ohpak SB-802.5HQ, the mobile phase was sodium nitrate, the flow rate was 0.6 mL / min, and the column temperature was 35 °C. The weight-average molecular weight of the obtained chondroitin sulfate polysaccharide CS1 was 8843 Da (see [reference]). Figure 5 ).

[0155] Comparative Example 2

[0156] Bimetallic single-atom catalyst materials bi-SACs were prepared according to the method of Comparative Example 1, except that 4.2132 g of ferric nitrate nonahydrate and 0.6330 g of copper nitrate trihydrate were added to 40 mL of ultrapure water.

[0157] Then, low molecular weight chondroitin sulfate was prepared according to the method of Comparative Example 1. The difference was that in step (2), 3.5 mL of the 0.02 g / mL metal single-atom catalyst bi-SACs prepared was added, and the solution volume was made up to 10 mL with acetic acid-sodium acetate buffer (100 mM) at pH 6.

[0158] The molecular weight of the obtained chondroitin sulfate was analyzed by high-performance liquid chromatography-evaporative light scattering detector (HPLC-ELSD). The chromatographic column was a Shodex Ohpak SB-802.5HQ, the mobile phase was sodium nitrate, the flow rate was 0.6 mL / min, and the column temperature was 35 °C. The weight-average molecular weight of the obtained chondroitin sulfate polysaccharide CS2 was 6592 Da (see [reference]). Figure 5 ).

[0159] Comparative Example 3

[0160] The three polysaccharides CS3, CS1, and CS2 obtained in Example 5 and Comparative Examples 1 and 2 were subjected to alcohol precipitation, dialysis, and lyophilization to obtain purified polysaccharides CS1, CS2, and CS3. Their total antioxidant capacity was tested against undegraded chondroitin sulfate CSO. 20 μL of a 0.005 g / mL polysaccharide solution was added to 180 μL of FRAP working solution, and the reaction was carried out at room temperature for 0.5 h. The absorbance at 593 nm was measured. The total antioxidant capacity of the three polysaccharide solutions was compared with CS3 as 100%. The results are shown in [link to results]. Figure 14 The polysaccharide obtained in Example 5 showed the best overall antioxidant effect, therefore it is believed that tri-SACs trimetallic doped materials have the best activity.

[0161] Comparative Example 4

[0162] 4.2132 g of ferric nitrate nonahydrate, 0.6330 g of copper nitrate trihydrate, and 0.3807 g of zinc nitrate heptahydrate were dissolved in 40 mL of ultrapure water and stirred at 300 rpm for 20 min to obtain solution A. 3.5 g of melamine was dissolved in 120 mL of dimethyl sulfoxide to obtain solution B, and 3.5 g of cyanuric acid was dissolved in 120 mL of dimethyl sulfoxide to obtain solution C. Under conditions of 40℃ oil bath and 400 rpm, solution A was first slowly added dropwise to solution B and stirred for 45 min. Then, solution C was slowly added dropwise to solution B and stirred for another 45 min. After the reaction was complete, the mixture was centrifuged at 6000 rpm for 7 min, the precipitate was recovered, and washed twice with water. The precipitate was dried and reacted in a tube furnace at 400℃ for 4 h under a N2 atmosphere to obtain the single-atom catalyst material tri-SACs-1 without the addition of phenanthroline and ammonium carbonate.

[0163] 4.2132 g of ferric nitrate nonahydrate, 0.6330 g of copper nitrate trihydrate, 0.3807 g of zinc nitrate heptahydrate, and 0.5 g of 1,10-phenanthroline were dissolved in 40 mL of ultrapure water and stirred at 300 rpm for 20 min to obtain solution A. 3.5 g of melamine was dissolved in 120 mL of dimethyl sulfoxide to obtain solution B, and 3.5 g of cyanuric acid was dissolved in 120 mL of dimethyl sulfoxide to obtain solution C. Under conditions of 40°C oil bath and 400 rpm, solution A was first slowly added dropwise to solution B and stirred for 15 min, then solution C was slowly added dropwise to solution B and stirred for another 45 min. After the reaction was complete, the mixture was centrifuged at 6000 rpm for 7 min, the precipitate was recovered, washed twice with water, dried, and then reacted in a tube furnace at 400°C under a N2 atmosphere for 4 h to obtain the single-atom catalyst material tri-SACs-2, which contains only phenanthroline and no ammonium carbonate.

[0164] The activities of tri-SACs with the addition of phenanthroline and ammonium carbonate, tri-SACs-1 without the addition of phenanthroline and ammonium carbonate, and tri-SACs-2 with the addition of only phenanthroline and no addition of ammonium carbonate were verified according to the following steps.

[0165] (1) Take 2.5 mL of acetate-sodium acetate buffer (100 mM) with pH 6 into three test tubes respectively, add 2 mL of 0.05 g / mL chondroitin sulfate and 2 mL of 30% hydrogen peroxide solution to the three test tubes respectively, and mix them evenly to obtain a mixed solution.

[0166] (2) Add 3.5 mL of 0.02 g / mL of the three tri-SACs obtained in Example 1 and this comparative example, which simultaneously added phenanthroline and ammonium carbonate, did not add phenanthroline and ammonium carbonate, and only added phenanthroline and ammonium carbonate, to the three test tubes above, and shake for 24 h at 42 °C and 150 rpm to obtain the reaction solution.

[0167] (3) The reaction solution was centrifuged (8000 rpm, 10 min). The supernatant obtained was the solution containing low molecular weight chondroitin sulfate. The supernatant was tested by passing it through a 22% glucose slurry. The results are shown in […]. Figure 15 The results show that, in preparing this metal single-atom catalyst, the ligands phenanthroline and ammonium carbonate must be added simultaneously to enable the prepared catalyst to have better polysaccharide degradation activity, narrower and more uniform bands, and lower molecular weight.

[0168] Comparative Example 5

[0169] (1) Take 6.8 mL of acetate-sodium acetate buffer (100 mM) with pH 7 into 5 test tubes, add 2 mL of 0.05 g / mL chondroitin sulfate to each tube, and mix them thoroughly to obtain a mixed solution.

[0170] (2) 1.2 mL of the metal catalyst material tri-S-Ce-uio66-NH2 obtained in Example 2 was added to the solution respectively at concentrations of 0.001 g / mL, 0.01 g / mL, 0.005 g / mL, 0.002 g / mL and 0.0015 g / mL. The reaction was carried out under photocatalytic conditions of 300 W xenon lamp light source, wavelength of 320-780 nm and rotation speed of 150 rpm for 2 h to obtain the reaction solution.

[0171] (3) The reaction solution was centrifuged (8000 rpm, 10 min). The supernatant obtained was the solution containing low molecular weight chondroitin sulfate. The supernatant was tested by passing it through a 22% glucose slurry. The results are shown in […]. Figure 16 .

[0172] The results showed that different amounts of catalyst resulted in different molecular weight ranges for the bands. Using an appropriate amount could yield the desired band, but if an excessive amount was added (for example, tri-S-Ce-uio66-NH2, more than 0.01 mg / ml, 1.2 mL, 2 h), it would degrade into disaccharide units.

Claims

1. A method for preparing a metal catalyst material, characterized in that, Includes the following steps: (1) The ligand material is mixed with the trimetallic ion solution and stirred to react, then the solid and liquid are separated, washed and dried; (2) After the dried solid is ground into powder, it is calcined at high temperature to obtain a metal single-atom catalyst, which is the metal catalyst material; (3) Alternatively, the metal single-atom catalyst obtained in step (2) can be mixed evenly with the metal-organic framework material and ground, and then calcined at high temperature to obtain a composite metal catalyst material; In step (1), the ligand material comprises a composite of melamine, cyanuric acid, and ammonium carbonate; the mass ratio of melamine, cyanuric acid, and ammonium carbonate is 3.5:3.5:1.8-2.2; during the preparation process, ligand material 1,10-phenanthroline is added, and the mass ratio of 1,10-phenanthroline to ammonium carbonate is 0.3-0.8:1.8-2.

2. The trimetallic ions mentioned in step (1) contain iron ions, copper ions and zinc ions; the total elemental mass ratio of the iron ions and the copper and zinc ions is 1:0.25-1, and the elemental mass ratio of the copper and zinc ions is 1:0.15-1; The metal-organic framework material mentioned in step (3) is uio66, Ce-uio66 or Ce-uio66-NH2.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the metal ions to the ligand material is 1:1.5-25; the total concentration of metal ions added in the metal ion solution is 12-30 g / L.

3. The preparation method according to claim 1, characterized in that, In step (1), the reaction temperature of the ligand material and the metal ion solution is 27-140℃, the rotation speed is 300-1000rpm, and the time is 1.5-14h.

4. The preparation method according to claim 1, characterized in that, In step (2), the calcination temperature is 350-600℃ and the time is 3-8h.

5. The preparation method according to claim 1, characterized in that, The mass ratio of the metal single-atom catalyst to the metal-organic framework material in step (3) is 1:0.4-2; the calcination temperature in step (3) is 200-400℃ and the time is 2-4h.

6. The application of a metal catalyst material prepared by the method described in claim 1 in the controlled degradation of polysaccharides; the specific process of the application is as follows: (a) Mix the high molecular weight polysaccharide solution and the buffer solution to obtain a mixed solution; (b) Add a metal catalyst material to the mixed solution and carry out a shaking reaction under photocatalytic conditions to obtain a reaction solution; (c) The reaction solution is subjected to solid-liquid separation, and the resulting liquid is a solution containing the degraded polysaccharide; wherein, By adjusting the amount of the metal catalyst material, polysaccharides of different molecular weights can be obtained; The high molecular weight polysaccharide is any one or more of chondroitin sulfate, hyaluronic acid, heparin, heparan sulfate, xanthan gum, and guar gum.

7. The application according to claim 6, characterized in that, In step (b), the oscillating reaction under photocatalytic conditions is carried out as follows: 150-300W xenon lamp light source, wavelength of 320-780nm, rotation speed of 100-300rpm, and time of 2-12h.

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