3D porous carbon loaded SnS2 modified Ca-Al-LDH material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of functional materials, in particular to a 3D porous carbon loaded SnS2 modified Ca-Al-LDH material as well as a preparation method and application thereof. The invention provides a 3D porous carbon loaded SnS2 modified Ca-Al-LDH (layered double hydroxide) material as well as a preparation method and application thereof. SnS2 is selected as a light response type catalyst to modify a Ca-Al-LDH material, the composite material capable of being used for glucose isomerization in a photo-thermal catalysis system is prepared, the composite material is used for efficiently catalyzing glucose isomerization at low temperature to generate fructose, the composite material can be recycled, and the problems that a single Ca-Al-LDH material is poor in selectivity and low in conversion rate can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of functional materials, and in particular to a 3D porous carbon-loaded SnS2-modified Ca-Al-LDH material and a preparation method and application thereof. Background Art

[0002] Glucose is the most abundant and cheapest hexose in nature, and its isomerization to fructose is one of the most important reactions in biomass valorization. Fructose is an intermediate for many key platform chemicals and can be converted into downstream products such as 5-hydroxymethylfurfural (HMF), dimethyl succinate, 2,5-diformylfuran, and levulinic acid. Currently, research on the isomerization of glucose to fructose is primarily divided into two categories: homogeneous and heterogeneous catalytic systems. Homogeneous catalytic systems have garnered extensive research attention since their first description in the late 19th century. Homogeneous catalytic systems involve the substrate and catalyst in the same phase. While homogeneous catalysts exhibit good dispersion, reactions proceed more easily. However, these systems present challenges such as difficult product separation and low catalyst reusability. Compared to homogeneous catalytic systems, solid catalysts in heterogeneous catalytic systems offer excellent recyclability.

[0003] Layered Double Hydroxide (LDH) is a layered double hydroxide with the general formula [Mg 1- x Al x (OH)2] x+ (Ax / n n- )·mH2O. Due to the hydrolysis of its surface hydroxyl groups and weakly acidic anions, hydrotalcite is alkaline in aqueous solution and is widely used in various base-catalyzed reaction systems, such as the isomerization of glucose to fructose. However, the low selectivity of single hydrotalcite materials for fructose results in low fructose yields, necessitating modification to improve selectivity and conversion efficiency. Summary of the Invention

[0004] The present invention provides a 3D porous carbon-supported SnS2-modified Ca-Al-LDH material, its preparation method, and application. The present invention selects SnS2 as a light-responsive catalyst to modify the Ca-Al-LDH material, producing a composite material that can be used for glucose isomerization in a photothermal catalytic system. This composite material is used to efficiently catalyze glucose isomerization to produce fructose at low temperatures. The recyclable composite material addresses the poor selectivity and low conversion rate of single Ca-Al-LDH materials.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a 3D porous carbon-supported SnS2-modified Ca-Al-LDH material, comprising:

[0007] S1. A tin source, citric acid, terephthaloyl chloride, and 3D porous carbon were mixed in ethanol, followed by the addition of thioacetamide and further mixing, followed by hydrothermal treatment to obtain a 3D porous carbon-loaded SnS2 composite with oxygen vacancies.

[0008] S2. A calcium source and an aluminum source are mixed in water to obtain a mixed solution A. The composite material of 3D porous carbon loaded with SnS2 with oxygen vacancies in S1 is added to the mixed solution A, and the mixture is mixed again to obtain a mixed solution B. The pH of the mixed solution B is then adjusted to 9.0-11.0 with an alkaline solution and then hydrothermally heated again to obtain a 3D porous carbon loaded SnS2 modified Ca-Al-LDH material.

[0009] Both single SnS2 materials and single Ca-Al-LDH materials have a lamellar structure and are prone to agglomeration. To address this problem, the applicant screened a variety of carriers and ultimately selected 3D porous carbon as the matrix material. Its large pore structure not only helps increase the specific surface area of the composite material and increase the active sites in contact with glucose, but also disperses the SnS2 material and Ca-Al-LDH material, allowing the two materials to achieve a 1+1>2 effect, avoiding agglomeration and exposing more active sites in a dispersed manner, which can directly contact glucose and significantly improve conversion efficiency.

[0010] By modifying with SnS2, the light response range of Ca-Al-LDH can be enhanced, and the absorption and utilization of visible light by the composite material can be improved. SnS2 material is first loaded on the 3D porous carbon by a stepwise hydrothermal method, and then the Ca-Al-LDH material is loaded, thereby realizing layered loading on the 3D porous carbon. Among them, the pore structure of the 3D porous carbon is utilized to make the SnS2 nanosheets grow dispersedly on the 3D porous carbon, and the Ca-Al-LDH grows evenly on the surface of the 3D porous carbon, which can further improve the stability and dispersion of the composite material; and oxygen vacancies are formed on the surface of the composite material, which is beneficial to electron transport under light, forming Lewis acidity, and synergistically promoting the glucose isomerization process.

[0011] On this basis, the applicant also screened the preparation method of SnS2. Although SnS2 is a photocatalytic material rich in Lewis acid, most researchers would think of using a photocatalytic material rich in Lewis acid to modify the photocatalytic material rich in Lewis acid. The Ca-Al-LDH material with alkalinity is used, but the applicant has chosen SnS2 containing oxygen vacancies. Firstly, oxygen vacancies can accelerate electron transfer under light and show Lewis acidity, thereby enriching the Lewis acid level in SnS2; oxygen vacancies can synergize with the original Lewis acid sites in SnS2 to improve the yield and selectivity of fructose. Secondly, the multi-layered Lewis acid can react with The base combines better to achieve efficient coordination of acid and base sites, jointly promoting the efficiency of glucose isomerization to fructose, and can reduce the temperature during isomerization, greatly reducing the cost of fructose production.

[0012] Preferably, in S1, the tin source is a tin salt.

[0013] More preferably, the tin salt is tin tetrachloride.

[0014] Preferably, in S1, the hydrothermal temperature is 170-200° C., and the hydrothermal time is 10-14 h; in S2, the hydrothermal temperature is 100-120° C., and the hydrothermal time is 10-14 h.

[0015] Preferably, in S1, the preparation method of 3D porous carbon is: glucose and sodium carbonate are mixed in water and frozen for more than 12 hours, and then freeze-dried to obtain a dry powder; in an inert atmosphere, the dry powder is calcined at 700-800°C for 2-3 hours to obtain 3D porous carbon.

[0016] More preferably, the inert atmosphere is a nitrogen atmosphere.

[0017] More preferably, the heating rate during calcination is 5-10°C / min.

[0018] More preferably, the dried powder is calcined at 700-800° C. for 2-3 h, and then washed with 1 M hydrochloric acid and deionized water for more than three times to obtain 3D porous carbon.

[0019] Carbonizing glucose, which self-assembles on the multi-scale salt sodium carbonate, can produce a three-dimensional (3D) porous carbon network. Compared to organic synthetic materials, the abundant biomass glucose feedstock has more sustainable application value. The synthesized 3D porous carbon network has a large specific surface area, providing abundant deposition sites and conductive substrates for active materials.

[0020] Preferably, in S1, the composite material of 3D porous carbon loaded with SnS2 with oxygen vacancies includes a 3D porous carbon matrix and SnS2 nanosheets with oxygen vacancies loaded on the 3D porous carbon matrix, and the mass ratio of SnS2 with oxygen vacancies to 3D porous carbon is (0.5~2.5):1.

[0021] Further preferably, the mass ratio of SnS2 with oxygen vacancies and 3D porous carbon is (1.5-1.8):1.

[0022] Preferably, in S2, the pH of the mixed solution B is adjusted to 9.95-10.05 with an alkaline solution.

[0023] Preferably, in the S2, the molar ratio between the calcium in the calcium source and the aluminum in the aluminum source is (1 to 4):1; the 3D porous carbon-loaded SnS2-modified Ca-Al-LDH material includes a 3D porous carbon matrix and SnS2 nanosheets with oxygen vacancies and Ca-Al-LDH materials layered on the 3D porous carbon matrix, and the mass ratio of the SnS2 material with oxygen vacancies and the Ca-Al-LDH material is (0.004 to 0.02):1.

[0024] Further preferably, the molar ratio between the calcium in the calcium source and the aluminum in the aluminum source is 4:1.

[0025] Further preferably, the mass ratio of SnS2 material with oxygen vacancies and Ca-Al-LDH material is (0.01-0.015):1.

[0026] The applicant selected a special mass ratio of SnS2 with oxygen vacancies and 3D porous carbon, and a special mass ratio of SnS2 material with oxygen vacancies and Ca-Al-LDH material to control the relative amount of SnS2 nanosheets and Ca-Al-LDH material, control the coordination degree of acid and base sites, and achieve the effect of 1+1>2.

[0027] Preferably, in S2, the alkali solution is sodium hydroxide solution and / or sodium carbonate solution.

[0028] More preferably, the alkali solution is 1M sodium hydroxide solution.

[0029] Preferably, in S2, the calcium source is a calcium salt. More preferably, the calcium salt is calcium chloride.

[0030] Preferably, in S2, the aluminum source is an aluminum salt. More preferably, the aluminum salt is aluminum chloride.

[0031] The present invention also provides a 3D porous carbon loaded SnS2 modified Ca-Al-LDH material, which includes a 3D porous carbon matrix and SnS2 nanosheets with oxygen vacancies and a Ca-Al-LDH material layered on the 3D porous carbon matrix; based on the weight of the 3D porous carbon loaded SnS2 modified Ca-Al-LDH material, the weight of the Ca-Al-LDH material is 97.0 to 98.0 wt%, and the weight of the SnS2 material with oxygen vacancies is 1.0 to 1.5 wt%.

[0032] Preferably, the 3D porous carbon-supported SnS2-modified Ca-Al-LDH material is a 3D mesoporous structure with CO bonds and a specific surface area of 160 to 170 m 2 / g.

[0033] The present invention also provides the application of 3D porous carbon-loaded SnS2-modified Ca-Al-LDH material in the photothermal isomerization of glucose to fructose.

[0034] Preferably, the photothermal isomerization conditions of glucose are: temperature 70-90° C., visible light irradiation, and normal pressure.

[0035] By layering Ca-Al-LDH and SnS2 nanosheets of different sizes on 3D porous carbon, a 3D porous carbon-loaded SnS2-modified Ca-Al-LDH material was synthesized. This material can isomerize glucose into fructose. The main principle is that SnS2 nanosheets have Lewis acid sites and oxygen vacancies. Oxygen vacancies can accelerate electron transfer under light and show Lewis acidity, so there are actually two forms of Lewis acid in SnS2 nanosheets. In addition, Ca-Al-LDH material is a saturated Alkaline materials can help the highly selective isomerization of open-ring glucose to fructose. Under the synergistic effect of alkali and two forms of Lewis acid, 3D porous carbon-loaded SnS2-modified Ca-Al-LDH material can realize the photothermal isomerization of glucose to fructose at low temperature.

[0036] Therefore, the present invention has the following beneficial effects:

[0037] (1) The present invention uses 3D porous carbon as a matrix, and loads Ca-Al-LDH and SnS2 nanosheets of different sizes on it in layers to synthesize 3D porous carbon-loaded SnS2-modified Ca-Al-LDH materials; the acidic sites of the SnS2 nanosheets and the alkaline sites of the Ca-Al-LDH material are combined to achieve a synergistic increase in the fructose conversion efficiency.

[0038] (2) The present invention utilizes a specific preparation method to prepare SnS2 nanosheets containing oxygen vacancies. Oxygen vacancies can accelerate electron transfer under light and exhibit Lewis acidity, which synergistically interacts with the original Lewis acid sites in the SnS2 nanosheets to improve the yield and selectivity of fructose.

[0039] (3) When the present invention composites Ca-Al-LDH and SnS2 nanosheets, Ca-Al-LDH and SnS2 nanosheets are loaded onto 3D porous carbon layers by hydrothermal treatment twice, so that the distribution of Ca-Al-LDH and SnS2 nanosheets on the 3D porous carbon is as follows: SnS2 nanosheets grow dispersedly on the 3D porous carbon, while Ca-Al-LDH grows uniformly on the surface of the 3D porous carbon. This distribution not only helps improve the stability and dispersion of the composite material, but also forms oxygen vacancies on the surface of the composite material, which is beneficial to electron transport under light, forming Lewis acidity and synergistically promoting the glucose isomerization process.

[0040] (4) The 3D porous carbon matrix of the present invention helps to disperse Ca-Al-LDH and SnS2 nanosheets, preventing them from agglomerating. It exposes more active sites in a dispersed manner, allowing them to directly contact with glucose, thereby significantly improving the conversion efficiency.

[0041] (5) The 3D porous carbon-loaded SnS2-modified Ca-Al-LDH material provided by the present invention can be recycled, and the conversion efficiency has not been significantly reduced.

[0042] (6) The 3D porous carbon-loaded SnS2-modified Ca-Al-LDH material provided by the present invention can realize glucose isomerization to fructose at low temperature. At 80°C and normal pressure, under visible light irradiation, the optimal fructose yield is 53.9% and the selectivity is 92.7%. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is the scanning electron microscopy image of Ca4Al1-LDH;

[0044] Figure 2 Ca4Al1-LDH@SS 0.75 -Scanning electron microscope image of TPC;

[0045] Figure 3 Ca4Al1-LDH and Ca4Al1-LDH@SS 0.75 -TPC specific surface area comparison chart;

[0046] Figure 4 FT-IR comparison chart of different catalytic materials;

[0047] Figure 5 XRD comparison diagram of different catalytic materials;

[0048] Figure 6 Ca4Al1-LDH@SS 0.75 -TPC glucose isomerization fructose performance comparison chart, where a is the effect of temperature, b is the effect of reaction time, c is the effect of different catalyst dosages, and d is the cycle diagram;

[0049] Figure 7 is the reaction mechanism diagram;

[0050] Figure 8 SnS2 and Ca4Al1-LDH@SS 0.75 - EPR diagram of TPC;

[0051] Figure 9 Comparative data of calcium aluminum hydrotalcite with different ratios under dark / light conditions, where a is Ca1Al1-LDH, b is Ca2Al1-LDH, c is Ca3Al1-LDH, and d is Ca4Al1-LDH;

[0052] Figure 10 Ca4Al1-LDH@SS 0.75 -B basicity comparison chart of TPC and Ca4Al1-LDH;

[0053] Figure 11 Ca4Al1-LDH@SS 0.75 -TPC and SS 0.75 - Comparison chart of BL acidity of TPC. DETAILED DESCRIPTION

[0054] The present invention will be further described below with reference to specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below generally represent only a portion of the present invention, rather than all of the embodiments. Therefore, all other embodiments derived by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0055] [Example]

[0056] Example 1

[0057] S1.0.625 g glucose and 10 g sodium carbonate were mixed in 20 mL deionized water and frozen for 12 h, followed by freeze-drying to obtain a dry powder; in a nitrogen atmosphere, the temperature was raised to 800 °C at a heating rate of 5 °C / min and kept warm for 3 h. The dry powder was calcined to obtain a black-gray powder, which was then washed three times with 1 M hydrochloric acid and deionized water to obtain 3D porous carbon, denoted as TPC.

[0058] S2.0.75mmol SnCl4·5H2O, 0.75mmol monohydrated citric acid and 83.5mg TPC were placed in 40mL ethanol and ultrasonically dispersed for 30min. 3.75mmol terephthaloyl chloride was added to the above mixed solution and ultrasonically dispersed for another 30min. The mixed solution was placed in a hydrothermal reactor and reacted at 180℃ for 12h. After the reaction, it was centrifuged and the separated powder was washed with ethanol and deionized water until the pH of the residual liquid reached neutral. The powder after washing was vacuum dried at 60℃ to constant weight to obtain a 3D porous carbon-loaded SnS2 composite material with oxygen vacancies, which was recorded as SS 0.75 -TPC.

[0059] S3.26.7mmol CaCl2·2H2O and 6.7mmol AlCl3·6H2O were added to 16mL deionized water and mixed with ultrasound to obtain mixed solution A. All the SS obtained in S2 were 0.75 -TPC was added to the mixed solution A and ultrasonically mixed again. Then, the pH of the mixed solution A was adjusted to 10.0±0.05 with 1M sodium hydroxide solution to obtain a mixed solution B. The mixed solution B was transferred to a hydrothermal reactor and reacted at 110°C for 12 hours. After the reaction, it was centrifuged and the separated powder was washed with deionized water until the pH of the residual liquid reached neutral. After washing, the powder was vacuum dried at 60°C to constant weight to obtain a 3D porous carbon-loaded SnS2-modified Ca-Al-LDH material, recorded as Ca4Al1-LDH@SS 0.75 -TPC. Among them, Ca4Al1-LDH@SS 0.75 -TPC, the SnS2 content is 1.34wt%, and the Ca4Al1-LDH content is 97.85wt%.

[0060] Comparative Example 1

[0061] 0.625 g of glucose and 10 g of sodium carbonate were mixed in 20 mL of deionized water and frozen for 12 h, followed by freeze-drying to obtain a dry powder; in a nitrogen atmosphere, the temperature was raised to 800 °C at a heating rate of 5 °C / min and kept for 3 h. The dry powder was calcined to obtain a black-gray powder, which was then washed three times with 1 M hydrochloric acid and deionized water to obtain 3D porous carbon, recorded as TPC.

[0062] Comparative Example 2

[0063] S1.0.625 g glucose and 10 g sodium carbonate were mixed in 20 mL deionized water and frozen for 12 h, followed by freeze-drying to obtain a dry powder; in a nitrogen atmosphere, the temperature was raised to 800 °C at a heating rate of 5 °C / min and kept warm for 3 h. The dry powder was calcined to obtain a black-gray powder, which was then washed three times with 1 M hydrochloric acid and deionized water to obtain 3D porous carbon, denoted as TPC.

[0064] S2.0.75mmol SnCl4·5H2O, 0.75mmol monohydrated citric acid and 83.5mg TPC were placed in 40mL ethanol and ultrasonically dispersed for 30min. 3.75mmol terephthaloyl chloride was added to the above mixed solution and ultrasonically dispersed for another 30min. The mixed solution was placed in a hydrothermal reactor and reacted at 180℃ for 12h. After the reaction, it was centrifuged and the separated powder was washed with ethanol and deionized water until the pH of the residual liquid reached neutral. The powder after washing was vacuum dried at 60℃ to constant weight to obtain a 3D porous carbon-loaded SnS2 composite material with oxygen vacancies, which was recorded as SS 0.75 -TPC.

[0065] Comparative Example 3

[0066] This comparative example is basically the same as comparative example 2, except that the amount of SnCl4·5H2O used is 0.25 mmol, recorded as SS 0.25 -TPC.

[0067] Comparative Example 4

[0068] This comparative example is basically the same as comparative example 2, except that the amount of SnCl4·5H2O used is 0.50 mmol, recorded as SS 0.50 -TPC.

[0069] Comparative Example 5

[0070] This comparative example is basically the same as comparative example 2, except that the amount of SnCl4·5H2O used is 1.00 mmol, recorded as SS 1.00 -TPC.

[0071] Comparative Example 6

[0072] 26.7mmol CaCl2·2H2O and 6.7mmol AlCl3·6H2O were added to 16mL deionized water and ultrasonically mixed to obtain a mixed solution A. The pH of the mixed solution A was then adjusted to 10.0±0.05 with 1M sodium hydroxide solution to obtain a white mixed solution. The white mixed solution was transferred to a hydrothermal reactor and reacted at 110°C for 12 hours. After the reaction, it was centrifuged and the separated powder was washed with deionized water until the pH of the residual liquid reached neutral. The powder after washing was vacuum dried at 60°C to constant weight (a total of 10g powder was obtained), and a 3D porous carbon-loaded SnS2-modified Ca-Al-LDH material was obtained, which was recorded as Ca4Al1-LDH.

[0073] Comparative Example 7

[0074] This comparative example is basically the same as comparative example 6, except that the amount of AlCl3·6H2O remains unchanged, the molar ratio of CaCl2·2H2O and AlCl3·6H2O is 3:1, and is recorded as Ca3Al1-LDH.

[0075] Comparative Example 8

[0076] This comparative example is basically the same as comparative example 6, except that the amount of AlCl3·6H2O remains unchanged, the molar ratio of CaCl2·2H2O and AlCl3·6H2O is 2:1, and is recorded as Ca2Al1-LDH.

[0077] Comparative Example 9

[0078] This comparative example is basically the same as comparative example 6, except that the amount of AlCl3·6H2O remains unchanged, the molar ratio of CaCl2·2H2O and AlCl3·6H2O is 1:1, and is recorded as Ca1Al1-LDH.

[0079] Comparative Example 10

[0080] 0.75 mmol of SnCl4·5H2O and 0.75 mmol of citric acid monohydrate were placed in 40 mL of ethanol and ultrasonically dispersed for 30 minutes. 3.75 mmol of terephthaloyl chloride was added to the mixed solution and ultrasonically dispersed for another 30 minutes. The mixture was placed in a hydrothermal reactor at 180°C for 12 hours. After the reaction, it was centrifuged and the resulting powder was washed with ethanol and deionized water until the pH of the residual solution reached neutral. The washed powder was vacuum-dried at 60°C to constant weight to obtain a SnS2 composite material with oxygen vacancies, designated as SnS2.

[0081]

Performance test

[0082] Test method: Using a 300W xenon lamp as the light source and glucose as the initial raw material, a photothermal catalytic conversion experiment was carried out under visible light radiation and a certain temperature. The specific steps are as follows: 100mg of glucose was weighed and added to 15.0mL of deionized water, 30.0mg to 60.0mg of catalyst (the catalyst material obtained in Example 1 and Comparative Examples 1 to 11) was added, and the reaction system was ultrasonically dispersed. During the reaction, the temperature was set at 30℃ to 120℃, the reaction time was 1 to 3h, and the stirring speed was 300rpm·min -1 After the reaction is completed, the resulting mixed solution is immediately collected and cooled in an ice-water bath, and the supernatant obtained after filtration is analyzed for products using high performance liquid chromatography (HPLC).

[0083] 1. Condition screening

[0084] ①Influence of acidic sites

[0085] The temperatures were set at 30°C, 80°C, 90°C, 100°C, 110°C, and 120°C, respectively. The light source was controlled to be on or off. The catalyst dosage was 50.0 mg, and the reaction time was 2 hours. The catalytic materials obtained in Comparative Examples 2 to 5 were tested under the same conditions as described in the "Test Method" above. The results are shown in Table 1 below.

[0086] Table 1. SSx-TPC conversion effects under different conditions

[0087]

[0088] From Table 1, we can see that under dark conditions, when the temperature is ≤80℃, SSx-TPC does not show an isomerization effect. This may be because the isomerization process of glucose at the Lewis acid site requires a higher reaction temperature to overcome the activation energy barrier. When the temperature rises to 90℃, fructose begins to form, and the glucose conversion rate is slightly higher than that at 80℃. As the temperature continues to rise, the fructose yield increases significantly between 100℃ and 110℃, but stabilizes after reaching 110℃. Among all the prepared materials, SSx-TPC 0.75 -TPC has the best fructose yield. 0.75 -TPC fructose yield is 27.0%. When the SnS2 loading is low, the active sites are insufficient, resulting in a low glucose conversion rate. However, when the SnS2 content is increased to 0.75 mmol, the number of Lewis acid sites also increases, thereby promoting the isomerization of glucose to fructose. Under light, the fructose yield and glucose conversion rate are higher than the yield and glucose conversion rate under dark conditions at the same temperature. This may be due to the presence of oxygen vacancies in the loaded SnS2. Under light, the oxygen vacancies can activate the aldehyde group of glucose and promote the isomerization process. Under light, as the reaction temperature increases, the two forms of Lewis acid sites synergistically promote the improvement of glucose conversion rate. However, at too high a temperature, the formation of other glucose conversion byproducts (such as humus) was observed. These byproducts are deposited on the catalyst surface, hindering the conversion of glucose.

[0089] ②Influence of basic sites

[0090] The base conditions of the four ratios of Ca-Al-LDH materials obtained in Comparative Examples 6 to 9 were identified by acid-base titration. The results are shown in Table 2 below.

[0091] Table 2. Comparison of CaAl-LDH basicity at different Ca-Al ratios

[0092]

[0093] The temperature was set at 70-110°C, the catalyst dosage was 50.0 mg, and the reaction time was 2 h. The Ca-Al-LDH materials obtained in Comparative Examples 6-9 were tested according to the above-mentioned "Test Method". The results are as follows: Figure 9 shown.

[0094] From Table 2, we can see that the basic sites increase with the increase of Ca content. The Ca-Al ratio increases from 1:1 (115 μmol / g) to 4:1 (938 μmol / g). Figure 9 The catalytic performance of the four materials under the same conditions shows that as the Ca content in Ca-Al-LDH increases, the glucose conversion rate also increases, indicating that the basic site plays a key role in the glucose isomerization process. Among them, Ca4Al1-LDH has the best fructose yield at 90-100℃; at 100℃, under light conditions, the fructose yield is 42.3%. Combining the results of "① The influence of acidic sites" and "② The influence of basic sites", it can be roughly determined that when SS 0.75 When -TPC is combined with Ca4Al1-LDH, a composite material with moderate acid-base sites can be obtained, which can achieve efficient isomerization of glucose to fructose.

[0095] 2. Structural Characterization

[0096] The Ca4Al1-LDH@SS obtained in Example 1 0.75 -TPC, TPC obtained in Comparative Example 1, SS obtained in Comparative Example 2 0.75 -TPC, Ca4Al1-LDH obtained in Comparative Example 6, and SnS2 obtained in Comparative Example 10 were characterized.

[0097] Figure 1 and Figure 2 Ca4Al1-LDH@SS 0.75 -TPC and Ca4Al1-LDH SEM results show that SnS2 is deposited on the 3D porous carbon through hydrothermal reaction. The secondary hydrothermal reaction enables Ca-Al-LDH to grow dispersedly on the outer surface of the 3D porous carbon. After the hydrothermal reaction, the carbon skeleton is not obviously damaged.

[0098] Figure 3 Ca4Al1-LDH@SS 0.75 -TPC and Ca4Al1-LDH BET results show that Ca4Al1-LDH@SS 0.75 -TPC and Ca4Al1-LDH BET spectra show a type IV isotherm pattern, indicating that the material has a rich mesoporous structure. 0.75The specific surface areas of -TPC and Ca4Al1-LDH are 41.812 m 2 / g and 168.700m 2 / g. This data proves that the composite SS 0.75 After TPC, the specific surface area of the composite material is significantly increased. The large specific surface area can provide more contact sites for subsequent reaction substrates, providing favorable conditions for isomerization reactions.

[0099] Figure 4 Ca4Al1-LDH@SS 0.75 -Infrared results of TPC, Ca4Al1-LDH, TPC and SnS2. Among them, 3630cm -1 The peak at 3475 cm is the vibration of hydroxyl groups in the Ca-Al-LDH layer. -1 The appearance of the peak at 1621 cm can be attributed to the stretching motion of lattice water molecules, which proves the successful preparation of hydrotalcite. -1 The peak at can be attributed to the HOH bending vibration of interlayer water molecules. 2- The asymmetric stretching vibration of 1460 cm -1 and 875cm -1 At 500~800cm -1 The appearance of the peaks in the range of 1098 cm-1 can be attributed to the vibration of the metal oxygen bond. It should be noted that in the FT-IR spectrum of the Ca4Al1-LDH@SS0.75-TPC composite, the peak at 1098 cm-1 was observed. -1 A new peak appears at , which can be attributed to the CO bond stretching vibration. This indicates that after SnS2 and Ca-Al-LDH are dispersed on the 3D porous carbon, more CO bonds are exposed. In the composite material, CO3 2- The vibration band intensity of is reduced, indicating that some SnS2 nanoparticles are also embedded in the Ca4Al1-LDH layers.

[0100] Figure 5 Ca4Al1-LDH@SS 0.75 -XRD results of TPC, Ca4Al1-LDH, TPC and SnS2. Figure 5 The characteristic peaks of Ca4Al1-LDH appear at 11.3°, 18.2°, 22.7°, 26.1° and 31.1°, corresponding to the typical crystal planes (006), (012), (0012), (1010) and (110), respectively. 0.75In the -TPC, the typical crystal phases (012), (0012) and (110) of hydrotalcite still exist, which confirms the successful preparation of hydrotalcite composite materials and their successful loading on 3D porous carbon. In addition, in Ca4Al1-LDH and Ca4Al1-LDH@SS 0.75 -TPC has typical crystal faces of calcium carbonate, as shown by the diamond marks in the figure. On the one hand, this is due to the 2- The addition of ions may be due to the partial formation of calcium carbonate due to the contact of the composite material with CO2 in the air. The characteristic peaks of SnS2 appear at 15.0°, 28.1°, 32.1°, 41.8°, 49.9°, 52.4° and 60.6°, corresponding to the typical crystal planes (001), (100), (101), (102), (110), (111) and (201) (JCPDS No. 23-0677). Due to the relatively low content of SnS2 or the partial loading of SnS2 onto the inner surface of the three-dimensional porous carbon, in the sample Ca4Al1-LDH@SS 0.75 In -TPC, only the (110) plane at 49.9° can be shown in XRD. The characteristic peak at 26.3° of TPC material comes from the (002) plane of high-purity carbon material (JCPDS No. 26-1079).

[0101] Figure 8 SnS2 and Ca4Al1-LDH@SS 0.75 -TPC EPR vacancy map shows that vacancy signals clearly appear in SnS2. After SnS2 is composited with Ca4Al1-LDH and TPC, the vacancies are attenuated but still retained.

[0102] 3. Glucose isomerization to fructose

[0103] The temperature was set at 70℃, 80℃, and 90℃, the catalyst dosage was 30.0mg, 40.0mg, 50.0mg, and 60.0mg, and the reaction time was 1h, 2h, and 3h. The Ca4Al1-LDH@SS obtained in Example 1 was tested according to the above-mentioned "test method". 0.75 -TPC, SS obtained in Comparative Example 2 0.75 -TPC, the Ca4Al1-LDH obtained in Example 6 was tested, and the results are as follows Figure 6 shown.

[0104] like Figure 6As shown in (a), at 70°C, the fructose yield exceeds 40%. When the temperature exceeds 80°C, the fructose yield no longer increases, and changing the temperature no longer promotes the fructose yield in the system. This is likely because at higher temperatures (>80°C), fructose further degrades, producing byproducts such as formic acid, acetic acid, and lactic acid. Therefore, higher reaction temperatures favor glucose conversion, but fructose yield and selectivity do not increase accordingly.

[0105] like Figure 6 As shown in (b), with a 300W xenon lamp as the light source, a fructose yield of 44.5% can be obtained after a reaction of 1 hour at 80°C. Further extending the reaction time, the fructose yield reaches a maximum value (53.9%) when the system reaction time is 2 hours. After further extending the reaction time, the fructose yield decreases. This may be due to the existence of carbon balance. Excessive extension of the reaction time leads to fructose degradation and reduces the catalytic selectivity. Ca4Al1-LDH@SS 0.75 -TPC has the best fructose yield of 53.9% under the conditions of catalyst dosage 50.0mg, 80℃, reaction time 2h and light irradiation; compared with the best fructose yield of Ca4Al1-LDH (42.3% (100℃) and SS under the same conditions, the best fructose yield of SS-TPC is 53.9% under the conditions of catalyst dosage 50.0mg, 80℃, reaction time 2h and light irradiation 0.75 The optimal fructose yield of -TPC was 27.9% (120°C), a significant improvement. In addition to the increased fructose yield, it is also noteworthy that the reaction temperature dropped from 120°C to 80°C, significantly reducing the reliance on high temperatures and shifting the entire reaction to a low-temperature-dominated state.

[0106] At the same temperature of 80℃, the catalyst dosage was 50.0mg, the reaction time was 2h, and the light conditions were as follows: Ca4Al1-LDH@SS 0.75 The fructose yield of -TPC was 53.9%, that of Ca4Al1-LDH was 37.7%, and that of SS 0.75 -TPC fructose yield is 0.7%. From this data, it can be shown that the Ca4Al1-LDH@SS obtained by the present invention 0.75 -TPC has significant advantages.

[0107] Figure 6(c) The effect of different catalyst dosages on the isomerization efficiency was discussed. With increasing catalyst dosage, the fructose yield showed a clear upward trend. At a dosage of 30 mg, the system produced nearly 20% fructose, and the fructose yield reached its highest level at 50 mg. Increasing the catalyst dosage to 60 mg further improved the glucose conversion, but the isomerization efficiency to fructose decreased. This may be related to the number of active sites in the reaction system. With increasing catalyst dosage, the number of active sites in the composite material increased, glucose isomerized and further reacted to form derivatives, thereby increasing glucose conversion. Consequently, the fructose yield decreased.

[0108] from Figure 6 (d) It can be seen that Ca4Al1-LDH@SS 0.75 After being recycled five times, the fructose yield of -TPC can still reach about 50.0%, showing good reusability.

[0109] Figure 10 Ca4Al1-LDH and SS 0.75 -B Alkalinity comparison chart before and after TPC combination. It can be seen that below 300℃ is weak alkalinity, and 300-500℃ is medium-strong alkalinity, both of which are conducive to glucose isomerization.

[0110] Figure 11 For SS 0.75 -TPC and Ca4Al1-LDH@SS 0.75 -TPC BL acidity comparison. It can be seen that Ca4Al1-LDH@SS 0.75 -TPC composite materials compared to single SS 0.75 -TPC, its L acidity is increased.

[0111] In the present invention, the principle of glucose isomerization to fructose is as follows:

[0112] Pathway one, based on the LdB-AvE mechanism, begins with glucose ring opening and catalyst activation. Upon contact with water, the surface of the Ca-Al-LDH@SS-TPC becomes hydrated. Subsequently, the water molecules dissociate, resulting in a negatively charged hydroxylated surface on the catalyst, which facilitates the deprotonation process. The negatively charged catalyst surface extracts the hydrogen at the C2 position from glucose, generating an enediol intermediate. The hydrogen atom of the hydroxyl group attached to the C2 position is transferred to the oxygen atom at the C1 position, forming a hydroxyl group at the C1 position of the glucose molecule. Electron transfer, rearrangement, and proton binding occur, leading to the generation of fructose from the enediol intermediate.

[0113] Pathway 2 is based on Lewis acid conversion. The carbonyl group of glucose aldehyde and the hydroxyl group of alcohol are simultaneously coordinated to the Lewis acid site of the material, polarizing the carbonyl group and promoting the transfer of hydride from C2 to C1. At the same time, under light conditions, Ca-Al-LDH and SnS2 have the ability to transfer electrons to 3D porous carbon. The oxygen vacancies in the base and the abundant positive charges in SnS2 facilitate the ring-opening process of glucose, where the oxygen vacancies and the abundant Lewis acid sites in SnS2 synergistically Basic sites enable the isomerization of glucose to fructose.

Claims

1. A method for preparing 3D porous carbon-supported SnS2-modified Ca-Al-LDH material, characterized in that: include: S1. A tin source, citric acid, terephthaloyl chloride, and 3D porous carbon were mixed in ethanol, followed by the addition of thioacetamide and further mixing, followed by hydrothermal treatment to obtain a 3D porous carbon-loaded SnS2 composite with oxygen vacancies. S2. A calcium source and an aluminum source are mixed in water to obtain a mixed solution A. The composite material of 3D porous carbon loaded with SnS2 with oxygen vacancies in S1 is added to the mixed solution A, and the mixture is mixed again to obtain a mixed solution B. The pH of the mixed solution B is then adjusted to 9.0-11.0 with an alkaline solution and then hydrothermally heated again to obtain a 3D porous carbon loaded SnS2 modified Ca-Al-LDH material.

2. The preparation method according to claim 1, wherein In the S1, the hydrothermal temperature is 170-200° C., and the hydrothermal time is 10-14 h; in the S2, the hydrothermal temperature is 100-120° C., and the hydrothermal time is 10-14 h.

3. The preparation method according to claim 1, wherein In S1, the preparation method of 3D porous carbon is: glucose and sodium carbonate are mixed in water and then frozen for more than 12 hours, and then freeze-dried to obtain a dry powder; in an inert atmosphere, the dry powder is calcined at 700-800° C. for 2-3 hours to obtain 3D porous carbon.

4. The preparation method according to claim 1, wherein In S1, the composite material of 3D porous carbon loaded with SnS2 with oxygen vacancies includes a 3D porous carbon matrix and SnS2 nanosheets with oxygen vacancies loaded on the 3D porous carbon matrix, and the mass ratio of SnS2 with oxygen vacancies to 3D porous carbon is (0.5~2.5):

1.

5. The preparation method according to claim 1 or 4, characterized in that In the S2, the molar ratio between the calcium in the calcium source and the aluminum in the aluminum source is (1 to 4):1; the 3D porous carbon-loaded SnS2-modified Ca-Al-LDH material includes a 3D porous carbon matrix and SnS2 nanosheets with oxygen vacancies and Ca-Al-LDH materials layered on the 3D porous carbon matrix, and the mass ratio of the SnS2 material with oxygen vacancies and the Ca-Al-LDH material is (0.004 to 0.02):

1.

6. The preparation method according to claim 1, wherein In the S2, the alkali solution is sodium hydroxide solution and / or sodium carbonate solution.

7. The 3D porous carbon-supported SnS2-modified Ca-Al-LDH material prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The 3D porous carbon loaded SnS2 modified Ca-Al-LDH material includes a 3D porous carbon matrix and SnS2 nanosheets with oxygen vacancies and Ca-Al-LDH materials layered on the 3D porous carbon matrix; based on the weight of the 3D porous carbon loaded SnS2 modified Ca-Al-LDH material, the weight of the Ca-Al-LDH material is 97.0 to 98.0 wt%, and the weight of the SnS2 material with oxygen vacancies is 1.0 to 1.5 wt%.

8. The 3D porous carbon-supported SnS2-modified Ca-Al-LDH material according to claim 7, wherein: The 3D porous carbon-loaded SnS2-modified Ca-Al-LDH material has a 3D mesoporous structure with CO bonds and a specific surface area of 160 to 170 m 2 / g.

9. Use of the 3D porous carbon-loaded SnS2-modified Ca-Al-LDH material prepared by the preparation method as described in any one of claims 1 to 6 or the 3D porous carbon-loaded SnS2-modified Ca-Al-LDH material as described in any one of claims 7 to 8 in the photothermal isomerization of glucose to fructose.

10. The use according to claim 9, characterized in that The photothermal isomerization conditions of glucose are: temperature 70-90° C., visible light irradiation, and normal pressure.

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