A sulfur-coordinated Cu single-atom material and its preparation method and application

Abstract

The present invention discloses a sulfur-coordinated Cu single-atom material, its preparation method, and application. The preparation method comprises: dispersing the Cu single-atom material in water to form a Cu single-atom material dispersion, then reacting it with a thioctic acid solution under photocatalytic conditions for 4-8 hours under stirring to produce the sulfur-coordinated Cu single-atom material; wherein the photocatalytic conditions include: a wavelength of 254-579 nm and a power of 12-15 mW / cm 2 The sulfur-coordinated Cu single-atom material of the present invention is novel and has a simple preparation method. It greatly enhances the enzymatic activity of the single-atom material and achieves efficient and broad-spectrum antibacterial properties. Furthermore, the sulfur-coordinated Cu single-atom material has a high grafting rate and tight coordination, and can control the release of active ingredients by responding to pH changes in the environment. It also synergizes with multiple enzyme activities to achieve broad-spectrum, strong, and long-lasting antibacterial properties, and will have good application prospects in the field of fruit and vegetable preservation.

Description

Technical Field

[0001] The invention relates to a sulfur-coordinated Cu single-atom material and a preparation method and application thereof, belonging to the technical field of fruit and vegetable storage and preservation materials. Background Art

[0002] Against the backdrop of rapid technological advancements, the field of fruit and vegetable preservation technology is experiencing a diverse and innovative trend, encompassing a variety of advanced approaches, including microbial manipulation, radiation sterilization, vacuum packaging, thin-film technology, and biopreservatives. Numerous research and trials are underway to combat oxidative browning and mold in fruits and vegetables, including low-temperature storage, controlled atmosphere refrigeration, mild preheating, ultraviolet light irradiation, xanthan gum and cinnamic acid composite coatings, chitosan coatings, fumigation, melatonin application, and postharvest inoculation. Some of these preservation strategies face limitations in commercial application due to insufficient validation of their effectiveness or consumer acceptance. Therefore, the research and promotion of fruit and vegetable preservation technologies remains of profound theoretical and practical significance, playing a crucial role in enhancing market competitiveness, reducing food loss, ensuring food safety, and satisfying public demand for a healthier diet.

[0003] Lipoic acid, a multifunctional plant growth regulator, possesses significant antioxidant, anti-inflammatory, and antimicrobial properties, playing a key role in regulating plant growth and development. This substance profoundly impacts plant growth and development by neutralizing reactive oxygen free radicals, optimizing circadian rhythms, and regulating fruit ripening and aging. Currently, lipoic acid research primarily focuses on clinical medicine, with limited research on its application in fruit and vegetable preservation.

[0004] Single-atom materials, as an emerging class of nanoscale materials, are composed of individual atoms connected by specific chemical bonds. They exhibit unique atomic-level structures, exceptional chemical stability, and excellent physical properties. These materials, with their high degree of controllability, fine pore structures, and surface functionalization, have revolutionized materials science and nanotechnology. Cu single atoms, nanoscale catalysts composed of single copper atoms, exhibit high activity, stability, and controllability. They have applications in electrocatalysis, CO2 reduction, organic synthesis, and sensors. They are at the forefront of nanoscience and materials science, promising advancements in energy conversion and environmental protection. Due to their unique structure and properties, single-atom materials have shown tremendous potential for applications in environmental protection, drug delivery, and controlled molecular release, and have garnered extensive attention and research. Furthermore, the metal sites in single-atom materials can undergo coordination, a field worthy of further exploration. In Cu single-atom catalysts, copper atoms can form coordinated structures with support materials or surrounding ligand atoms through chemical bonds. This coordination can modulate the electronic state of the single-atom material, thereby influencing its catalytic activity, selectivity, and stability. However, there is little research on Cu single-atom materials in the fields of coordination modification and fruit and vegetable preservation, and it is worth further exploration.

[0005] Thin film technology demonstrates remarkable practicality in food preservation, offering significant convenience, cost-effectiveness, and safety. It effectively extends the shelf life of fruits and vegetables while preserving their original quality and freshness, fully satisfying consumers' demand for high-quality food. Chitosan, a natural high-molecular-weight polysaccharide derived from the shells of crustaceans, possesses extremely high biocompatibility and gelling properties. Thanks to its excellent transparency and superior mechanical properties, chitosan has found widespread application in the pharmaceutical and food industries. In recent years, chitosan has been widely used in the production of food wrap, which provides excellent protection, effectively preventing moisture and contamination, and significantly extending the shelf life of food. Furthermore, chitosan is biodegradable and has a minimal environmental impact. Furthermore, gelatin, a protein extracted from animal bones and skin, also exhibits excellent gelling properties and biocompatibility, making it widely used in the food, pharmaceutical, and cosmetic industries. With the advancement of science and technology, intelligent responsive controlled-release systems have become a hot topic of research. These systems can intelligently respond to external stimuli or environmental changes (such as pH, gas, temperature, and humidity) to release active substances at optimal times and conditions. These systems have enormous potential and are expected to trigger innovative breakthroughs and promote scientific and technological advancement in fields such as medicine, agriculture, and food. Summary of the Invention

[0006] The main purpose of the present invention is to provide a sulfur-coordinated Cu single-atom material and its preparation method and application, so as to overcome the deficiencies in the prior art.

[0007] To achieve the aforementioned object of the invention, the technical solutions adopted by the present invention include:

[0008] An embodiment of the present invention provides a method for preparing a sulfur-coordinated Cu single-atom material, which comprises:

[0009] Providing a Cu single-atom material; wherein the Cu single-atom material is prepared by reacting at least nitrogen-doped porous carbon with a copper source;

[0010] The Cu single-atom material is dispersed in water to form a Cu single-atom material dispersion, which is then reacted with a thioctic acid solution under photocatalytic conditions for 4 to 8 hours under stirring to obtain a sulfur-coordinated Cu single-atom material. The thioctic acid solution comprises thioctic acid and water, and the photocatalytic conditions include a wavelength of 254 to 579 nm and a power of 12 to 15 mW / cm 2 .

[0011] The embodiment of the present invention also provides a sulfur-coordinated Cu single-atom material prepared by the aforementioned preparation method.

[0012] The embodiments of the present invention also provide the use of the aforementioned sulfur-coordinated Cu single-atom material in the field of fruit and vegetable preservation.

[0013] The embodiment of the present invention further provides a composition for preserving fruits and vegetables, which comprises the aforementioned sulfur-coordinated Cu single-atom material, gelatin, chitosan, glycerol and acetic acid solution;

[0014] The mass ratio of gelatin, chitosan and glycerol is 50:1:15~10:1:3; the mass volume ratio of gelatin and acetic acid solution is 1g:20mL~1g:25mL, and the concentration of acetic acid solution is 1~2wt%; the mass ratio of chitosan and sulfur-coordinated Cu single atom material is 2:1~10:1.

[0015] The embodiment of the present invention further provides a method for preserving fruits and vegetables, which comprises:

[0016] Gelatin is dissolved in acetic acid solution, and then chitosan, glycerol, and the aforementioned sulfur-coordinated Cu single atom material are added, stirred, and ultrasonically treated to form a film-forming solution;

[0017] Furthermore, at least the film-forming solution is applied to the surface of the fruit or vegetable, dried, and then stored in an environment with a temperature of 20-30° C. and a humidity of 70-80%.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The sulfur-coordinated Cu single-atom material of the present invention is novel and has a simple preparation method. It can significantly enhance the enzyme activity of the single-atom material, achieve high-efficiency and broad-spectrum antibacterial properties of the single-atom material, and solve the problem of the single-atom and poor antibacterial properties of existing single-atom materials.

[0020] (2) The sulfur-coordinated Cu single-atom material of the present invention has a high grafting rate and close coordination;

[0021] (3) The sulfur-coordinated Cu single-atom material of the present invention can not only improve the antibacterial performance of the single-atom material, but also significantly compensate for the shortcomings of the single-atom material in antifungal performance;

[0022] (4) The sulfur-coordinated Cu single-atom material in the present invention can control the release of active ingredients by responding to pH changes in the environment, and synergize multiple enzyme activities to achieve broad-spectrum, strong, and long-lasting antibacterial properties, which will have good application prospects in the field of fruit and vegetable preservation. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 TEM image of Cu single atom prepared in Comparative Example 1 of the present invention;

[0025] Figure 2 TEM image of the sulfur-coordinated Cu single-atom material prepared in Example 1 of the present invention;

[0026] Figure 3 The infrared spectra of lipoic acid of the present invention, the Cu single atom prepared in Comparative Example 1, and the sulfur-coordinated Cu single atom material prepared in Example 1 are shown;

[0027] Figure 4 Graphs showing potential detection of the Cu single atom prepared in Comparative Example 1 and the sulfur-coordinated Cu single atom material prepared in Example 1 of the present invention;

[0028] Figure 5 XRD spectra of the Cu single atom prepared in Comparative Example 1 and the sulfur-coordinated Cu single atom material prepared in Example 1 of the present invention;

[0029] Figure 6 Graphs showing nitrogen adsorption of the Cu single atom prepared in Comparative Example 1 and the sulfur-coordinated Cu single atom material prepared in Example 1 of the present invention;

[0030] Figure 7 Specific surface area diagram of the Cu single atom prepared in Comparative Example 1 of the present invention and the sulfur-coordinated Cu single atom material prepared in Example 1;

[0031] Figure 8 Colony count diagram of Cu single atom and sulfur-coordinated Cu single atom materials prepared in Comparative Example 1 and Examples 1, 2, and 3 of the present invention;

[0032] Figure 9 This is a graph showing the Escherichia coli inhibition rate of the nitrogen-doped porous carbon of the present invention, the Cu single atom in Comparative Example 1, and the sulfur-coordinated Cu single atom materials prepared in Examples 1, 2, and 3;

[0033] Figure 10 This is a graph showing the Staphylococcus aureus inhibition rate of the nitrogen-doped porous carbon of the present invention, the Cu single atom of Comparative Example 1, and the sulfur-coordinated Cu single atom materials prepared in Examples 1, 2, and 3;

[0034] Figure 11 Graph showing the gray mold inhibition rate of the nitrogen-doped porous carbon of the present invention, the Cu single atom in Comparative Example 1, and the sulfur-coordinated Cu single atom materials prepared in Examples 1, 2, and 3;

[0035] Figure 12 Graphs showing the oxidase activity of the Cu single atom and sulfur-coordinated Cu single atom materials prepared in Comparative Example 1 and Examples 1, 2, and 3 of the present invention;

[0036] Figure 13 Glutathione oxidase activity diagram of the Cu single atom and sulfur-coordinated Cu single atom materials prepared in Comparative Example 1 and Examples 1, 2, and 3 of the present invention;

[0037] Figure 14 This is a graph of the alkaline phosphatase activity of the Cu single atom and sulfur-coordinated Cu single atom materials prepared in Comparative Example 1 and Examples 1, 2, and 3 of the present invention;

[0038] Figure 15 Graph showing the ultraviolet blocking performance of thin films made from the membrane solutions prepared in Comparative Example 2 and Example 1 of the present invention and the membrane solution containing sulfur-coordinated Cu single-atom material;

[0039] Figure 16 Graphs showing the water vapor transmission rates of thin films made from the membrane solutions prepared in Comparative Example 2 and Example 1 of the present invention and the membrane solution containing sulfur-coordinated Cu single-atom material;

[0040] Figure 17 Graph showing the 2,2-diphenyl-1-picrylhydrazyl removal rates of thin films made from the membrane solutions prepared in Comparative Example 2 and Example 1 of the present invention and the membrane solutions containing sulfur-coordinated Cu single-atom materials;

[0041] Figure 18Graph showing the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) clearance rates of thin films made from the membrane solutions prepared in Comparative Example 2 and Example 1 of the present invention and the membrane solution containing the sulfur-coordinated Cu single-atom material;

[0042] Figure 19 This is a graph showing the pH-responsive release performance of a thin film made from a membrane solution containing sulfur-coordinated Cu single-atom material prepared in Example 1 of the present invention;

[0043] Figure 20 This figure shows the effect of the membrane solution prepared in Comparative Example 2 and Example 1 of the present invention and the membrane solution containing sulfur-coordinated Cu single-atom material on the brightness of strawberries when applied to post-harvest preservation of strawberries;

[0044] Figure 21 This figure shows the effect of the membrane solution prepared in Comparative Example 2 and Example 1 of the present invention and the membrane solution containing sulfur-coordinated Cu single-atom material on the hardness of strawberries when applied to post-harvest preservation of strawberries;

[0045] Figure 22 Graph showing the effects of the membrane solutions prepared in Comparative Example 2 and Example 1 of the present invention and the membrane solution containing sulfur-coordinated Cu single-atom material on the total soluble solids in strawberries when applied to post-harvest preservation of strawberries;

[0046] Figure 23 This figure shows the effects of the membrane solutions prepared in Comparative Example 2 and Example 1 of the present invention and the membrane solution containing sulfur-coordinated Cu single-atom material on the total number of microorganisms in strawberries when applied to post-harvest preservation of strawberries. DETAILED DESCRIPTION

[0047] In view of the shortcomings of the prior art, the inventors of this case, after long-term research and extensive practice, have proposed the technical solution of the present invention. To facilitate understanding of this application, this application will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to facilitate a more thorough and comprehensive understanding of the disclosure of the present invention.

[0048] Specifically, as one aspect of the technical solution of the present invention, a method for preparing a sulfur-coordinated Cu single-atom material includes:

[0049] Providing a Cu single-atom material; wherein the Cu single-atom material is prepared by reacting at least nitrogen-doped porous carbon with a copper source;

[0050] The Cu single-atom material is dispersed in water to form a Cu single-atom material dispersion, which is then reacted with a thioctic acid solution under photocatalytic conditions for 4 to 8 hours under stirring to obtain a sulfur-coordinated Cu single-atom material. The thioctic acid solution comprises thioctic acid and water, and the photocatalytic conditions include a wavelength of 254 to 579 nm and a power of 12 to 15 mW / cm 2 .

[0051] In some embodiments, the preparation method further comprises: washing and drying after the stirring reaction is completed.

[0052] In some embodiments, the mass ratio of Cu single-atom material to water in the Cu single-atom material dispersion is 1:400 to 1:500.

[0053] In some embodiments, the concentration of the lipoic acid solution is 0.25-1.0 g / L.

[0054] In some embodiments, the preparation method specifically comprises:

[0055] (1) Providing a nitrogen-doped porous carbon precursor; wherein the nitrogen-doped porous carbon precursor comprises ZIF-8 and / or UiO-66;

[0056] (2) calcining the nitrogen-doped porous carbon precursor at 900-950° C. for 5-7 h in an inert atmosphere to obtain nitrogen-doped porous carbon;

[0057] (3) Dispersing nitrogen-doped porous carbon, a copper source, a cyanide-containing compound, and a polymer in a mixed solvent and performing ultrasonic treatment, respectively, and then mixing and fully stirring the obtained solutions, and then collecting crystals, washing, and drying to obtain a Cu single-atom material precursor; wherein the mixed solvent includes isopropyl alcohol and water; the cyanide-containing compound includes any one or more combinations of sodium dicyanamide, potassium dicyanamide, zinc dicyanamide, and sodium cyanide; the polymer includes any one or more combinations of melamine, ammeline, and polycyanamide;

[0058] (4) In an inert atmosphere, the Cu single-atom material precursor is calcined at 630-680° C. for 2-4 hours to obtain the Cu single-atom material.

[0059] Furthermore, the preparation method of ZIF-8 includes: dissolving zinc nitrate hexahydrate and 2-methylimidazole in methanol to form a zinc nitrate hexahydrate methanol solution and a 2-methylimidazole methanol solution, respectively, then mixing and fully stirring, and then collecting crystals, washing, and drying to obtain ZIF-8; wherein the mass volume ratio of zinc nitrate hexahydrate to methanol in the zinc nitrate hexahydrate methanol solution is 1g:45~55mL, and the mass volume ratio of 2-methylimidazole to methanol in the 2-methylimidazole methanol solution is 1g:20~30mL.

[0060] Furthermore, the preparation method of UiO-66 includes: dissolving zirconium tetrachloride and terephthalic acid in DMF to form a zirconium tetrachloride DMF solution and a terephthalic acid DMF solution respectively, then mixing and fully stirring, and then collecting crystals, washing, and drying to obtain UiO-66.

[0061] Furthermore, the mass ratio of the nitrogen-doped porous carbon, the copper source, the cyanide-containing compound and the polymer is 1:1:2:2 to 1:1:3:3.

[0062] Furthermore, the mass volume ratio of the nitrogen-doped porous carbon to the mixed solvent is 1 g:300 mL to 1 g:400 mL.

[0063] Furthermore, the volume ratio of isopropyl alcohol to water in the mixed solvent is 2:1 to 1:1.

[0064] Furthermore, the copper source includes any one or more combinations of copper nitrate trihydrate, copper chloride, copper sulfate, and copper acetate, but is not limited thereto.

[0065] Furthermore, the inert atmosphere includes an argon atmosphere, but is not limited thereto.

[0066] Furthermore, the ultrasonic treatment time in step (3) is 1 to 3 hours.

[0067] Furthermore, the stirring time in step (3) is 10 to 14 hours.

[0068] In some more specific embodiments, the method for preparing the sulfur-coordinated Cu single-atom material comprises:

[0069] (1) Zinc nitrate hexahydrate and 2-methylimidazole were dissolved in methanol respectively. After complete dissolution, the two solutions were mixed and stirred thoroughly. The crystals were collected and washed, and then dried in an oven at 80°C to obtain ZIF-8. The ZIF-8 powder was calcined at high temperature under an inert atmosphere, and the powder was collected after cooling to obtain nitrogen-doped porous carbon (denoted as: NPC). A certain amount of nitrogen-doped porous carbon, copper nitrate trihydrate, sodium dicyanamide and melamine powder were dissolved in a mixture of isopropanol and water respectively. After ultrasonication, the solutions were mixed and stirred thoroughly. The crystals were collected and washed, and then dried in an oven at 80°C to obtain a Cu single-atom material precursor. The precursor was then calcined at high temperature under an inert atmosphere, and the powder was collected after cooling to obtain a Cu single-atom material (denoted as: Cu-CN).

[0070] (2) A certain amount of the Cu single-atom material prepared in step (1) is dispersed in distilled water, and a certain amount of thioctic acid is dissolved in distilled water. The two are then mixed and fully stirred under photocatalytic conditions. The crystals are collected and washed, and then dried in an oven at 80°C to obtain sulfur-coordinated Cu single-atom material (denoted as: Cu-CNS).

[0071] Preferably, in step (1), zinc nitrate hexahydrate and 2-methylimidazole are dissolved in methanol respectively, and after complete dissolution, the two solutions are mixed and fully stirred, wherein the mass volume ratio of zinc nitrate hexahydrate to methanol is 1:45-55, and the mass volume ratio of 2-methylimidazole to methanol is 1:20-30, and the stirring time is 22-26 hours.

[0072] Preferably, the ZIF-8 powder is calcined at a high temperature under an inert atmosphere in step (1), wherein the inert atmosphere is argon, and the calcination conditions include: a heating rate of 4-6 °C / min, and maintaining at 900-950 °C for 5-7 hours.

[0073] Preferably, in step (1), a certain amount of nitrogen-doped porous carbon, copper nitrate trihydrate, sodium dicyandiamide and melamine powder are respectively dissolved in a mixture of isopropyl alcohol and water, and the solutions are mixed and fully stirred after ultrasonication, wherein the mass ratio of nitrogen-doped porous carbon, copper nitrate trihydrate, sodium dicyandiamide and melamine is 1:1:2:2~1:1:3:3, the volume ratio of isopropyl alcohol to water is 2:1~1:1, the mass volume ratio of nitrogen-doped porous carbon to the mixture of isopropyl alcohol and water is 1:300~1:400, the ultrasonication time is 1-3h, and the stirring time is 10-14h.

[0074] Preferably, the Cu single atom precursor is calcined at a high temperature in an inert atmosphere in step (1), wherein the inert atmosphere is argon, and the calcination conditions include: a heating rate of 2-4 °C / min, and maintaining at 630-680 °C for 2-4 h.

[0075] Preferably, in step (2), a certain amount of Cu atoms is dispersed in distilled water, and a certain amount of thioctic acid is dissolved in distilled water, and then the two are mixed and fully stirred under photocatalytic conditions, wherein the mass volume ratio of Cu atoms to distilled water is 1:400-1:500, the concentration of the thioctic acid aqueous solution is selected from any one of 0.25 g / L, 0.5 g / L, and 1 g / L, and the photocatalytic conditions include: a wavelength of 254-579 nm, a power of 12-15 mW / cm 2 , stirring time is 4-8h.

[0076] As another aspect of the technical solution of the present invention, it relates to a sulfur-coordinated Cu single-atom material prepared by the aforementioned preparation method.

[0077] As another aspect of the technical solution of the present invention, it also relates to the use of the aforementioned sulfur-coordinated Cu single-atom material in the field of fruit and vegetable preservation.

[0078] As another aspect of the technical solution of the present invention, it also relates to a composition for preserving fruits and vegetables, which comprises the aforementioned sulfur-coordinated Cu single-atom material, gelatin, chitosan, glycerol and acetic acid solution;

[0079] Among them, the mass ratio of the gelatin, chitosan and glycerol is 50:1:15~10:1:3; the mass volume ratio of the gelatin and the acetic acid solution is 1g:20mL~1g:25mL, and the concentration of the acetic acid solution is 1~2wt%; the mass ratio of the chitosan and the sulfur-coordinated Cu single-atom material is 2:1~10:1, for example, any one of 10:1, 5:1, 10:3, 5:2, and 2:1.

[0080] In some more specific implementation cases, the preparation method of the composition for preserving fruits and vegetables includes: dissolving a certain amount of gelatin in an acetic acid solution, then adding a certain amount of chitosan and glycerol, and then adding a certain amount of sulfur-coordinated Cu single-atom material, stirring evenly and then ultrasonically treating to obtain a composition, that is, a film-forming solution containing sulfur-coordinated Cu single-atom material.

[0081] As another aspect of the technical solution of the present invention, it also relates to a method for preserving fruits and vegetables, which comprises:

[0082] Gelatin is dissolved in acetic acid solution, and then chitosan, glycerol, and the aforementioned sulfur-coordinated Cu single atom material are added, stirred, and ultrasonically treated to form a film-forming solution;

[0083] Furthermore, at least the film-forming solution is applied to the surface of the fruit or vegetable, dried, and then stored in an environment with a temperature of 20-30° C. and a humidity of 70-80%.

[0084] In some more specific implementation cases, the mass ratio of gelatin, chitosan and glycerol is 50:1:15~10:1:3; the mass volume ratio of gelatin to acetic acid solution is 1g:20mL~1g:25mL, and the concentration of the acetic acid solution is 1~2wt%; the mass ratio of chitosan to sulfur-coordinated Cu single atom material is 2:1~10:1, for example, any one of 10:1, 5:1, 10:3, 5:2, and 2:1.

[0085] In some more specific implementation cases, the stirring time is 1 to 3 hours.

[0086] In some more specific implementation cases, the ultrasonic treatment time is 1 to 3 hours.

[0087] The present invention is further illustrated by the following examples. The present invention can be better understood according to the following examples. However, it will be readily understood by those skilled in the art that the specific material ratios, process conditions, and results described in the examples are merely illustrative of the present invention and should not, and do not, limit the present invention as described in detail in the claims.

[0088] Unless otherwise specified, the various raw materials, reaction equipment, testing equipment and testing methods used in the following examples are all well known in the art. The unit of mass-to-volume ratio used in this application is g:mL.

[0089] Example 1

[0090] This embodiment provides a method for preparing a sulfur-coordinated Cu single-atom material capable of high-efficiency and broad-spectrum antibacterial properties, which specifically includes the following steps:

[0091] (1) Zinc nitrate hexahydrate and 2-methylimidazole were dissolved in methanol (mass volume ratio of 1 g:50 mL and 1 g:20 mL, respectively). After complete dissolution, the two solutions were mixed and stirred for 24 hours. The crystals were collected, washed, and dried in an oven at 80°C to obtain ZIF-8. The ZIF-8 powder was calcined at high temperature under an argon atmosphere (calcination conditions included: heating rate 5°C / min, holding at 950°C for 5 hours), and the powder was collected after cooling to obtain nitrogen-doped porous carbon (NPC). A certain amount of nitrogen-doped porous carbon, copper nitrate trihydrate, sodium dicyanamide, and melamine powders were dissolved in a mixture of isopropanol and water (the mass ratio of nitrogen-doped porous carbon, copper nitrate trihydrate, sodium dicyanamide, and melamine was 1:1:2:2, the volume ratio of isopropanol and water was 2:1, and the mass-to-volume ratio of nitrogen-doped porous carbon to the isopropanol / water mixture was 1g:300mL). After ultrasonication for 2 hours, the solution was mixed and stirred for 12 hours. The crystals were collected, washed, and dried in an 80°C oven to obtain a Cu single-atom precursor. This precursor was then calcined at high temperature under an argon atmosphere (calcination conditions included a heating rate of 2°C / min and a hold time of 2 hours at 650°C). After cooling, the powder was collected to obtain the Cu single-atom material (Cu-CN).

[0092] (2) A certain amount of Cu single atom material in (1) was dispersed in distilled water (the mass volume ratio of Cu single atom to distilled water was 1:500), and a certain amount of thioctic acid was dissolved in distilled water (the concentration of thioctic acid aqueous solution was 1 g / L), and then the two were mixed and subjected to photocatalytic conditions (photocatalytic conditions were 365 nm, 12.5 mW / cm 2 ) was stirred for 8 h, and the crystals were collected, washed, and dried in an oven at 80 °C to obtain sulfur-coordinated Cu single-atom material (Cu-CNS).

[0093] (3) A certain amount of gelatin was dissolved in an acetic acid solution, followed by the addition of a certain amount of chitosan and glycerol, and then a certain amount of sulfur-coordinated Cu single-atom material (the mass ratio of gelatin, chitosan, and glycerol was 50:1:15, the mass volume ratio of gelatin to acetic acid solution was 1 g:20 mL, the concentration of acetic acid solution was 1 wt%, and the mass ratio of chitosan to sulfur-coordinated Cu single-atom material was 2:1). After stirring for 2 hours, the mixture was ultrasonically treated for 2 hours to obtain a membrane solution containing sulfur-coordinated Cu single-atom material. The harvested strawberries were then placed in the membrane solution and soaked for 5 minutes. After draining, the mixture was stored at 25°C and 75% relative humidity.

[0094] Comparative Example 1

[0095] Zinc nitrate hexahydrate and 2-methylimidazole were dissolved in methanol (mass-to-volume ratios of 1 g:50 mL and 1 g:20 mL, respectively). After complete dissolution, the two solutions were mixed and stirred for 24 hours. The crystals were collected, washed, and dried in an 80°C oven to obtain ZIF-8. The ZIF-8 powder was calcined at a high temperature under an argon atmosphere (calcination conditions included a heating rate of 5°C / min and a hold temperature of 950°C for 5 hours). After cooling, the powder was collected to obtain nitrogen-doped porous carbon (NPC). A certain amount of nitrogen-doped porous carbon, copper nitrate trihydrate, sodium dicyanamide, and melamine powders were dissolved in a mixture of isopropanol and water (the mass ratio of nitrogen-doped porous carbon, copper nitrate trihydrate, sodium dicyanamide, and melamine was 1:1:2:2, the volume ratio of isopropanol and water was 2:1, and the mass-to-volume ratio of nitrogen-doped porous carbon to the isopropanol / water mixture was 1g:300mL). After ultrasonication for 2 hours, the solution was mixed and stirred for 12 hours. The crystals were collected, washed, and dried in an 80°C oven to obtain a Cu single-atom precursor. This precursor was then calcined at high temperature under an argon atmosphere (calcination conditions included a heating rate of 2°C / min and a hold time of 2 hours at 650°C). After cooling, the powder was collected to obtain Cu single atoms (Cu-CN).

[0096] Comparative Example 2

[0097] A certain amount of gelatin was dissolved in an acetic acid solution, followed by the addition of chitosan and glycerol (the mass ratio of gelatin, chitosan, and glycerol was 50:1:15, the mass volume ratio of gelatin to acetic acid solution was 1g:20mL, and the acetic acid solution concentration was 1wt%). The mixture was stirred for 2 hours and then sonicated for 2 hours to produce a membrane solution. Harvested strawberries were then immersed in this membrane solution for 5 minutes, drained, and stored at 25°C and 75% relative humidity.

[0098] Performance characterization: Figure 1-Figure 7 TEM images of Cu single atoms and sulfur-coordinated Cu single atoms prepared in Comparative Example 1 and Example 1 ( Figure 1 is the TEM image of Comparative Example 1, Figure 2 TEM image of Example 1), infrared spectrum ( Figure 3 )、Potential detection( Figure 4 )、XRD spectrum( Figure 5 )、Nitrogen adsorption curve( Figure 6 ) and specific surface area ( Figure 7). In the TEM image, it can be seen that the morphology of Cu single atoms and sulfur-coordinated Cu single atoms remains consistent, without significant changes, and both show a regular and uniform dodecahedron morphology. Compared with Cu single atoms, the size of sulfur-coordinated Cu single atoms also hardly changes, proving that this coordination method does not affect its external morphology. In the infrared spectrum, it can be seen that the characteristic peak of disulfide bonds (520cm-1) is lost in the sulfur-coordinated Cu single atoms. -1 ), which produces a C-S bond (665 cm -1 ), indicating that when lipoic acid coordinates with Cu single atoms, the disulfide bond of lipoic acid is broken, and a Cu-S coordination bond is formed with the Cu single atom site, allowing the two to bind tightly. In the potential image, it can be seen that the potential of the sulfur-coordinated Cu single atom material has dropped significantly. In XRD, it can be seen that the crystal structures of Cu single atoms and sulfur-coordinated Cu single atom materials are very similar, indicating that the coordination of Cu single atoms with lipoic acid does not affect their structural integrity. In the nitrogen adsorption curve and specific surface area, it can be seen that Cu single atoms and sulfur-coordinated Cu single atom materials have microporous and mesoporous structures; after the Cu single atom is coordinated with lipoic acid, the specific surface area decreases, which means that this coordination occupies a small amount of pores, thereby reducing the available surface area for adsorption of gases or other molecules.

[0099] Figure 15-18 The graphs show the UV blocking performance, water vapor transmission rate, and antioxidant performance of the films made from the membrane solutions prepared in Comparative Example 2 and Example 1 and the membrane solutions containing sulfur-coordinated Cu single-atom materials, wherein: Figure 15 This is the UV blocking performance diagram. Figure 16 is the water vapor transmission rate diagram, Figure 17 is the scavenging rate graph of 2,2-diphenyl-1-picrylhydrazyl, Figure 18 The figure shows the scavenging rate of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid). It can be seen that the film made of sulfur-coordinated Cu single-atom material has better ultraviolet and water vapor barrier properties, and can better prevent water loss and the influence of ultraviolet rays. In addition, the film made of sulfur-coordinated Cu single-atom material has stronger free radical scavenging ability, indicating that it has stronger antioxidant performance.

[0100] Figure 19 The pH-responsive release performance of a film made from a membrane solution containing a sulfur-coordinated Cu single-atom material prepared in Example 1 shows significant differences in the amount of lipoic acid released by the film under different pH conditions. As the pH decreases, the release rate of lipoic acid increases significantly. This indicates that slightly acidic conditions significantly promote the release of lipoic acid, demonstrating that films made from sulfur-coordinated Cu single-atom materials have excellent pH-responsive performance.

[0101] Figure 20-23The membrane solution prepared in Comparative Example 2 and Example 1 and the membrane solution containing sulfur-coordinated Cu single-atom material are used for post-harvest preservation of strawberries, wherein: Figure 20 For the purpose of maintaining strawberry brightness after harvest ( L* ), Figure 21 This is the effect of strawberry hardness when applied to post-harvest strawberry preservation. Figure 22 This is a graph showing the effect of post-harvest preservation on the total soluble solids in strawberries. Figure 23 This figure shows the effect of the sulfur-coordinated Cu single-atom material on the total number of microorganisms in strawberries during post-harvest preservation. It can be seen that the sulfur-coordinated Cu single-atom material can significantly reduce the darkening of the color of strawberries during storage, inhibit the growth and reproduction of microorganisms, the decrease in hardness and the increase in total soluble solids, thereby effectively inhibiting the rotting and deterioration of strawberries.

[0102] Example 2

[0103] (1) Zinc nitrate hexahydrate and 2-methylimidazole were dissolved in methanol (mass volume ratio of 1 g:50 mL and 1 g:20 mL, respectively). After complete dissolution, the two solutions were mixed and stirred for 24 hours. The crystals were collected, washed, and dried in an oven at 80°C to obtain ZIF-8. The ZIF-8 powder was calcined at high temperature under an argon atmosphere (calcination conditions included: heating rate 5°C / min, holding at 950°C for 5 hours), and the powder was collected after cooling to obtain nitrogen-doped porous carbon (NPC). A certain amount of nitrogen-doped porous carbon, copper nitrate trihydrate, sodium dicyanamide, and melamine powders were dissolved in a mixture of isopropanol and water (the mass ratio of nitrogen-doped porous carbon, copper nitrate trihydrate, sodium dicyanamide, and melamine was 1:1:2:2, the volume ratio of isopropanol and water was 2:1, and the mass-to-volume ratio of nitrogen-doped porous carbon to the isopropanol / water mixture was 1g:300mL). After ultrasonication for 2 hours, the solution was mixed and stirred for 12 hours. The crystals were collected, washed, and dried in an 80°C oven to obtain a Cu single-atom precursor. This precursor was then calcined at high temperature under an argon atmosphere (calcination conditions included a heating rate of 2°C / min and a hold time of 2 hours at 650°C). After cooling, the powder was collected to obtain a Cu single-atom material (Cu-CN).

[0104] (2) A certain amount of Cu single atom material in (1) was dispersed in distilled water (the mass volume ratio of Cu single atom to distilled water was 1 g:500 mL), and a certain amount of thioctic acid was dissolved in distilled water (the concentration of thioctic acid aqueous solution was 0.25 g / L), and then the two were mixed and subjected to photocatalytic conditions (photocatalytic conditions were 365 nm, 12.5 mW / cm 2 ) was stirred for 4 h, and the crystals were collected, washed, and dried in an oven at 80 °C to obtain sulfur-coordinated Cu single-atom material (Cu-CNS).

[0105] (3) A certain amount of gelatin was dissolved in an acetic acid solution, followed by the addition of a certain amount of chitosan and glycerol, and then a certain amount of sulfur-coordinated Cu single-atom material (the mass ratio of gelatin, chitosan, and glycerol was 50:1:15, the mass volume ratio of gelatin to acetic acid solution was 1 g:20 mL, the concentration of acetic acid solution was 1 wt%, and the mass ratio of chitosan to sulfur-coordinated Cu single-atom material was 2:1). After stirring for 2 hours, the mixture was ultrasonically treated for 2 hours to obtain a membrane solution containing sulfur-coordinated Cu single-atom material. The harvested strawberries were then placed in the membrane solution and soaked for 5 minutes. After draining, the mixture was stored at 25°C and 75% relative humidity.

[0106] Example 3

[0107] (1) Zinc nitrate hexahydrate and 2-methylimidazole were dissolved in methanol (mass volume ratio of 1 g:50 mL and 1 g:20 mL, respectively). After complete dissolution, the two solutions were mixed and stirred for 24 hours. The crystals were collected, washed, and dried in an oven at 80°C to obtain ZIF-8. The ZIF-8 powder was calcined at high temperature under an argon atmosphere (calcination conditions included: heating rate 5°C / min, holding at 950°C for 5 hours), and the powder was collected after cooling to obtain nitrogen-doped porous carbon (NPC). A certain amount of nitrogen-doped porous carbon, copper nitrate trihydrate, sodium dicyanamide, and melamine powders were dissolved in a mixture of isopropanol and water (the mass ratio of nitrogen-doped porous carbon, copper nitrate trihydrate, sodium dicyanamide, and melamine was 1:1:2:2, the volume ratio of isopropanol and water was 2:1, and the mass-to-volume ratio of nitrogen-doped porous carbon to the isopropanol / water mixture was 1g:300mL). After ultrasonication for 2 hours, the solution was mixed and stirred for 12 hours. The crystals were collected, washed, and dried in an 80°C oven to obtain a Cu single-atom precursor. This precursor was then calcined at high temperature under an argon atmosphere (calcination conditions included a heating rate of 2°C / min and a hold time of 2 hours at 650°C). After cooling, the powder was collected to obtain the Cu single-atom material (Cu-CN).

[0108] (2) A certain amount of Cu single atom material in (1) was dispersed in distilled water (the mass volume ratio of Cu single atom to distilled water was 1 g:500 mL), and a certain amount of thioctic acid was dissolved in distilled water (the concentration of thioctic acid aqueous solution was 0.5 g / L), and then the two were mixed and subjected to photocatalytic conditions (photocatalytic conditions were 365 nm, 12.5 mW / cm 2 ) was stirred for 6 h, and the crystals were collected, washed, and dried in an oven at 80 °C to obtain sulfur-coordinated Cu single-atom material (Cu-CNS).

[0109] (3) A certain amount of gelatin was dissolved in an acetic acid solution, followed by the addition of a certain amount of chitosan and glycerol, and then a certain amount of sulfur-coordinated Cu single-atom material (the mass ratio of gelatin, chitosan, and glycerol was 50:1:15, the mass volume ratio of gelatin to acetic acid solution was 1 g:20 mL, the concentration of acetic acid solution was 1 wt%, and the mass ratio of chitosan to sulfur-coordinated Cu single-atom material was 2:1). After stirring for 2 hours, the mixture was ultrasonically treated for 2 hours to obtain a membrane solution containing sulfur-coordinated Cu single-atom material. The harvested strawberries were then placed in the membrane solution and soaked for 5 minutes. After draining, the mixture was stored at 25°C and 75% relative humidity.

[0110] Performance characterization: Figure 8 Colony counts for the Cu single-atom and sulfur-coordinated Cu single-atom materials prepared in Comparative Example 1 and Examples 1, 2, and 3 are shown. It can be seen that compared to the Cu single-atom materials, the sulfur-coordinated Cu single-atom materials are more effective in inhibiting the growth of Escherichia coli, Staphylococcus aureus, and Botrytis cinerea. The sulfur-coordinated Cu single-atom material in Example 1 exhibits the most significant inhibitory effect, achieving nearly 100% antibacterial activity. Furthermore, the sulfur-coordinated Cu single-atom material significantly improves the antibacterial properties of the single-atom materials while significantly compensating for their lack of antifungal properties.

[0111] Figures 9-11 The antibacterial rates of the Cu single atom and sulfur-coordinated Cu single atom materials prepared in Comparative Example 1 and Examples 1, 2, and 3 show that the sulfur-coordinated Cu single atom material prepared in Example 1 has the strongest inhibitory effect on the growth of Escherichia coli, Staphylococcus aureus, and Botrytis cinerea, reaching 99%, 100%, and 95%, respectively.

[0112] Figure 12-14 The enzymatic activities of the Cu single-atom and sulfur-coordinated Cu single-atom materials prepared in Comparative Example 1 and Examples 1, 2, and 3 are shown. The sulfur-coordinated Cu single-atom material prepared in Example 1 exhibits the strongest oxidase (using TMB as a probe), glutathione oxidase (using DTNB as a probe), and alkaline phosphatase (using 4-AAP as a probe) activities. Compared to Cu single-atom materials, the sulfur-coordinated Cu single-atom material significantly enhances the activity of multiple enzymes and synergizes these activities to achieve broad-spectrum, potent, and long-lasting antibacterial properties.

[0113] Example 4

[0114] (1) Zinc nitrate hexahydrate and 2-methylimidazole were dissolved in methanol (mass volume ratio of 1 g:45 mL and 1 g:30 mL, respectively). After complete dissolution, the two solutions were mixed and stirred for 24 hours. The crystals were collected, washed, and dried in an oven at 80°C to obtain ZIF-8. The ZIF-8 powder was calcined at high temperature under an argon atmosphere (calcination conditions included: heating rate 4°C / min, holding at 900°C for 6 hours), and the powder was collected after cooling to obtain nitrogen-doped porous carbon (NPC). A certain amount of nitrogen-doped porous carbon, copper nitrate trihydrate, sodium dicyanamide, and melamine powders were dissolved in a mixture of isopropanol and water (the mass ratio of nitrogen-doped porous carbon, copper nitrate trihydrate, sodium dicyanamide, and melamine was 1:1:3:3, the volume ratio of isopropanol and water was 1:1, and the mass-to-volume ratio of nitrogen-doped porous carbon to the isopropanol / water mixture was 1g:400mL). After ultrasonication for 3 hours, the solution was mixed and stirred for 10 hours. The crystals were collected, washed, and dried in an 80°C oven to obtain a Cu single-atom precursor. This precursor was then calcined at high temperature under an argon atmosphere (calcination conditions included a heating rate of 4°C / min and a hold temperature of 680°C for 3 hours). After cooling, the powder was collected to obtain the Cu single-atom material (Cu-CN).

[0115] (2) A certain amount of Cu single atom material in (1) was dispersed in distilled water (the mass volume ratio of Cu single atom to distilled water was 1 g:400 mL), and a certain amount of thioctic acid was dissolved in distilled water (the concentration of thioctic acid aqueous solution was 0.5 g / L), and then the two were mixed and subjected to photocatalytic conditions (photocatalytic conditions were 254 nm, 15 mW / cm 2 ) was stirred for 6 h, and the crystals were collected, washed, and dried in an oven at 80 °C to obtain sulfur-coordinated Cu single-atom material (Cu-CNS).

[0116] (3) A certain amount of gelatin was dissolved in an acetic acid solution, followed by the addition of a certain amount of chitosan and glycerol, and then a certain amount of sulfur-coordinated Cu single-atom material (the mass ratio of gelatin, chitosan, and glycerol was 10:1:3, the mass volume ratio of gelatin and acetic acid solution was 1 g:25 mL, the concentration of acetic acid solution was 2 wt%, and the mass ratio of chitosan and sulfur-coordinated Cu single-atom material was 10:1). After stirring for 2 hours, the mixture was ultrasonically treated for 2 hours to obtain a membrane solution containing sulfur-coordinated Cu single-atom material. The harvested strawberries were then placed in the membrane solution and soaked for 5 minutes. After draining, they were stored at 30°C and 80% relative humidity. Characterization showed that this embodiment exhibited excellent antibacterial and fresh-keeping effects.

[0117] Example 5

[0118] (1) Zirconium tetrachloride and terephthalic acid were dissolved in DMF (mass volume ratio of 1g:55mL and 1g:25mL, respectively). After complete dissolution, the two solutions were mixed and stirred for 24 hours. The crystals were collected, washed, and dried in an oven at 80°C to obtain UiO-66. The UiO-66 powder was calcined at high temperature under an argon atmosphere (calcination conditions included: heating rate 6°C / min, holding at 930°C for 7 hours), and the powder was collected after cooling to obtain nitrogen-doped porous carbon (NPC). A certain amount of nitrogen-doped porous carbon, copper nitrate trihydrate, sodium dicyanamide, and melamine powders were dissolved in a mixture of isopropanol and water (the mass ratio of nitrogen-doped porous carbon, copper nitrate trihydrate, sodium dicyanamide, and melamine was 1:1:2:2, the volume ratio of isopropanol and water was 2:1, and the mass-to-volume ratio of nitrogen-doped porous carbon to the isopropanol / water mixture was 1g:350mL). After ultrasonication for 2 hours, the solution was mixed and stirred for 12 hours. The crystals were collected, washed, and dried in an 80°C oven to obtain a Cu single-atom precursor. This precursor was then calcined at high temperature under an argon atmosphere (calcination conditions included a heating rate of 3°C / min and a hold temperature of 630°C for 4 hours). After cooling, the powder was collected to obtain the Cu single-atom material (Cu-CN).

[0119] (2) A certain amount of Cu single atom material in (1) was dispersed in distilled water (the mass volume ratio of Cu single atom to distilled water was 1 g:4500 mL), and a certain amount of thioctic acid was dissolved in distilled water (the concentration of thioctic acid aqueous solution was 0.5 g / L), and then the two were mixed and subjected to photocatalytic conditions (photocatalytic conditions were 579 nm, 14 mW / cm 2 ) was stirred for 6 h, and the crystals were collected, washed, and dried in an oven at 80 °C to obtain sulfur-coordinated Cu single-atom material (Cu-CNS).

[0120] (3) A certain amount of gelatin was dissolved in an acetic acid solution, followed by the addition of a certain amount of chitosan and glycerol, and then a certain amount of sulfur-coordinated Cu single-atom material (the mass ratio of gelatin, chitosan, and glycerol was 50:1:15, the mass volume ratio of gelatin and acetic acid solution was 1 g:23 mL, the concentration of acetic acid solution was 1.5 wt%, and the mass ratio of chitosan and sulfur-coordinated Cu single-atom material was 5:1). After stirring for 2 hours, the mixture was ultrasonically treated for 2 hours to obtain a membrane solution containing sulfur-coordinated Cu single-atom material. The harvested strawberries were then placed in the membrane solution and soaked for 5 minutes. After draining, they were stored at 25°C and 80% relative humidity. Characterization showed that this embodiment exhibited excellent antibacterial and fresh-keeping effects.

[0121] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments using other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0122] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. A method for preparing a sulfur-coordinated Cu single-atom material, characterized in that: include: Provide Cu single-atom materials; The Cu single-atom material is dispersed in water to form a Cu single-atom material dispersion, which is then reacted with a thioctic acid solution under photocatalytic conditions for 4 to 8 hours under stirring to obtain a sulfur-coordinated Cu single-atom material. The thioctic acid solution comprises thioctic acid and water, and the photocatalytic conditions include a wavelength of 254 to 579 nm and a power of 12 to 15 mW / cm 2 ; The method for preparing the Cu single-atom material comprises: (1) Providing a nitrogen-doped porous carbon precursor; wherein the nitrogen-doped porous carbon precursor comprises ZIF-8 and / or UiO-66; (2) calcining the nitrogen-doped porous carbon precursor at 900-950° C. for 5-7 h in an inert atmosphere to obtain nitrogen-doped porous carbon; (3) Dispersing nitrogen-doped porous carbon, a copper source, a cyanide-containing compound, and a polymer in a mixed solvent and performing ultrasonic treatment, respectively, and then mixing and fully stirring the obtained solutions, and then collecting crystals, washing, and drying to obtain a Cu single-atom material precursor; wherein the mixed solvent includes isopropyl alcohol and water; the cyanide-containing compound includes any one or more combinations of sodium dicyanamide, potassium dicyanamide, zinc dicyanamide, and sodium cyanide; the polymer includes any one or more combinations of melamine, ammeline, and polycyanamide; (4) In an inert atmosphere, the Cu single-atom material precursor is calcined at 630-680° C. for 2-4 hours to obtain the Cu single-atom material.

2. The preparation method according to claim 1, wherein: The mass ratio of Cu single-atom material to water in the Cu single-atom material dispersion is 1:400-1:500; and / or the concentration of the thioctic acid solution is 0.25-1.0 g / L.

3. The preparation method according to claim 1, wherein: The mass ratio of the nitrogen-doped porous carbon, the copper source, the cyanide-containing compound and the polymer is 1:1:2:2 to 1:1:3:3; And / or, the mass volume ratio of the nitrogen-doped porous carbon to the mixed solvent is 1 g:300 mL to 1 g:400 mL; And / or, the volume ratio of isopropyl alcohol to water in the mixed solvent is 2:1 to 1:

1.

4. The preparation method according to claim 1, wherein: The copper source includes any one or more combinations of copper nitrate trihydrate, copper chloride, copper sulfate, and copper acetate; and / or the inert atmosphere includes an argon atmosphere.

5. The preparation method according to claim 1, wherein: The ultrasonic treatment time in step (3) is 1 to 3 hours; and / or the stirring time in step (3) is 10 to 14 hours.

6. A sulfur-coordinated Cu single-atom material prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the sulfur-coordinated Cu single-atom material according to claim 6 in the field of fruit and vegetable preservation.

8. A composition for preserving fruits and vegetables, characterized in that: Comprising the sulfur-coordinated Cu single atom material according to claim 6, gelatin, chitosan, glycerol and acetic acid solution; The mass ratio of gelatin, chitosan and glycerol is 50:1:15~10:1:3; the mass volume ratio of gelatin and acetic acid solution is 1g:20mL~1g:25mL, and the concentration of acetic acid solution is 1~2wt%; the mass ratio of chitosan and sulfur-coordinated Cu single atom material is 2:1~10:

1.

9. A method for preserving fruits and vegetables, characterized in that: include: Dissolving gelatin in an acetic acid solution, then adding chitosan, glycerol, and the sulfur-coordinated Cu single-atom material according to claim 6, stirring, and ultrasonically treating to form a film-forming solution; Furthermore, at least the film-forming solution is applied to the surface of the fruit or vegetable, dried, and then stored in an environment with a temperature of 20-30° C. and a humidity of 70-80%.

10. The method for preserving fruits and vegetables according to claim 9, characterized in that: The mass ratio of the gelatin, chitosan and glycerol is 50:1:15~10:1:3; the mass volume ratio of the gelatin and the acetic acid solution is 1g:20mL~1g:25mL, and the concentration of the acetic acid solution is 1~2wt%; the mass ratio of the chitosan and the sulfur-coordinated Cu single-atom material is 2:1~10:

1.

11. The method for preserving fruits and vegetables according to claim 9, characterized in that: The stirring time is 1 to 3 hours; and / or the ultrasonic treatment time is 1 to 3 hours.

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