HM-UiO-66 (at) CTF / MFC aerogel as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of photocatalytic material preparation, and particularly relates to HM-UiO-66 (at) CTF / MFC aerogel and a preparation method and application thereof.The preparation method comprises the following steps that zirconium tetrachloride and 2-aminoterephthalic acid are added into an N, N-dimethylformamide solution of lauryl sodium sulfate, and stirring reaction is conducted; the preparation method comprises the following steps: dissolving sodium dodecyl sulfate in deionized water, then standing at 70-90 DEG C for 5-20 hours, then washing a solid product, removing the sodium dodecyl sulfate in the product, and drying to obtain HM-UiO-66-NH2; the preparation method comprises the following steps: placing HM-UiO-66-NH2 in an inert atmosphere, mixing the HM-UiO-66-NH2 with a chloroform solution of 4-cyanobenzoyl chloride, carrying out a stirring reaction, dropwise adding triethylamine into the mixture, and continuously carrying out a stirring reaction to obtain HM-UiO-66-CN; the preparation method comprises the following steps: mixing HM-UiO-66-CN with 4, 4 '-biphenyl formonitrile, and adding trifluoromethanesulfonic acid into the mixture to prepare HM-UiO-66 (at) CTF-2; and uniformly mixing the aqueous dispersion of the HM-UiO-66 (at) CTF-2 and the aqueous dispersion of the microfibrillated cellulose according to a ratio, and carrying out freeze-drying, so as to obtain the HM-UiO-66 (at) CTF / MFC aerogel. When the aerogel is used as a photocatalyst, the aerogel has good light absorption performance, good VOCs adsorption performance and good photocatalytic degradation efficiency.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic material preparation technology, specifically relating to an HM-UiO-66@CTF / MFC aerogel, its preparation method, and its application. Background Technology

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] UiO-66 is a zirconium-based metal-organic framework adsorbent. It is a three-dimensional network crystal structure formed by the self-assembly of zirconium ions and terephthalic acid ligands through coordination bonds. It maintains structural stability even under harsh conditions (such as strong acids, strong bases, and polar solvents). Therefore, UiO-66-based adsorbents are widely used in the treatment of dyes and heavy metal ions.

[0004] However, the pore structure of UiO-66 reveals two distinct cage types within its internal framework: octahedral cages with a diameter of 11 Å and tetrahedral cages with a diameter of 8 Å, connected by triangular channels with a diameter of 6 Å. The presence of these mixed cages results in strong molecular size selectivity during adsorption in UiO-66. Large molecules struggle to enter its pores, while small molecules easily accumulate in the channels, leading to reduced adsorption performance. Furthermore, UiO-66's insufficient light absorption and tendency for carrier recombination limit its applications in photocatalysis. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide an HM-UiO-66@CTF / MFC aerogel, its preparation method, and its application.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing HM-UiO-66@CTF / MFC aerogel, comprising the following steps: Zirconium tetrachloride and 2-aminoterephthalic acid were added to a sodium dodecyl sulfate N,N-dimethylformamide solution and stirred at 30-40°C for 5-15 h. The mixture was then allowed to stand at 70-90°C for 5-20 h. The solid product was then washed to remove sodium dodecyl sulfate and dried to obtain HM-UiO-66-NH2. HM-UiO-66-NH2 was placed in an inert atmosphere and mixed with a chloroform solution of 4-cyanobenzoyl chloride. The mixture was stirred at 20-30°C for 0.1-1.5 h. Triethylamine was added dropwise and the mixture was stirred for another 5-15 h to obtain HM-UiO-66-CN. HM-UiO-66-CN was mixed with 4,4'-biphenylnitrile, and trifluoromethanesulfonic acid was added to prepare HM-UiO-66@CTF-2. The aqueous dispersion of HM-UiO-66@CTF-2 and the aqueous dispersion of microfibrillated cellulose were mixed evenly in a certain proportion and then freeze-dried to obtain HM-UiO-66@CTF / MFC aerogel.

[0008] Secondly, the present invention provides an HM-UiO-66@CTF / MFC aerogel, which is prepared by the aforementioned preparation method.

[0009] Thirdly, the present invention provides the application of the HM-UiO-66@CTF / MFC aerogel as a photocatalyst.

[0010] The beneficial effects achieved by one or more embodiments of the present invention described above are as follows: The HM-UiO-66@CTF / MFC aerogel of this invention utilizes sodium dodecyl sulfate to create pores during the synthesis of UiO-66, followed by microwave treatment to in-situ load CTF-2 onto the UiO-66 surface, and then freeze-drying with microfibrillated cellulose to prepare an aerogel material with adsorption and efficient degradation of VOCs. The loading of CTF-2 introduces triazine structural units, improving the material's light absorption performance and expanding its light absorption range. The stable conjugated structure between C and N atoms can undergo π-π interactions with benzene compounds in VOCs, improving the adsorption performance for VOCs (taking toluene as an example).

[0011] Simultaneously, the expanded pores of UiO-66 expose buried active sites, preventing stacking structures during CTF-2 synthesis and greatly exposing catalytic sites. The triazine ring in CTF-2 has high electronegativity, and this electron-rich property allows it to form a heterostructure with UiO-66, promoting the separation of photoinduced electrons and holes, which is beneficial for the generation of active free radicals and improves the photocatalytic degradation efficiency of VOCs.

[0012] The HM-UiO-66@CTF / MFC aerogel of this invention provides a new strategy for studying the design and structure-activity relationship of novel porous aerogel composites for efficient VOCs removal, and further promotes the application of novel porous aerogel composites in the field of photocatalytic VOCs treatment. Attached Figure Description

[0013] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0014] Figure 1This is a schematic diagram of the preparation process of HM-UiO-66@CTF / MFC aerogel according to an embodiment of the present invention; Figure 2 In the image, (a) is the SEM characterization image of UiO-66-NH2, (b) is the SEM characterization image of HM-UiO-66-NH2, (c) is the TEM characterization image of UiO-66-NH2, and (d) is the TEM characterization image of HM-UiO-66-NH2. Figure 3 These are the nitrogen isothermal adsorption curves of UiO-66-NH2 and HM-UiO-66-NH2 in embodiments of the present invention; Figure 4 In the image, (a) is the SEM characterization image of CTF-2, (b) is the SEM characterization image of HM-UiO-66@CTF-2, (c) is the TEM characterization image of CTF-2, and (d) is the TEM characterization image of HM-UiO-66@CTF-2. Figure 5 In the image, (a) is the SEM image of sample 1, (b) is the SEM image of sample 2, (c) is the SEM image of sample 3, and (d) is the SEM image of sample 4; (e) is the TEM image of sample 1, (f) is the TEM image of sample 2, (g) is the TEM image of sample 3, and (h) is the TEM image of sample 4. Figure 6 In the image, (a) shows the XRD patterns of UiO-66-NH2, HM-UiO-66-NH2, and samples 1, 2, 3, and 4; (b) shows the XRD pattern of CTF-2; (c) shows the FT-IR spectra of HM-UiO-66-CN, HM-UiO-66-NH2, samples 1, 2, 3, 4, and CTF-2; and (d) shows the FT-IR comparative analysis of UiO-66-NH2, HM-UiO-66-NH2, and sample 4. Figure 7 In the image, (a) is the HRTEM image of HM-UiO-66@CTF-2; (b) is a magnified HRTEM image of HM-UiO-66@CTF-2; and (c) is the nitrogen isotherm adsorption curves of samples 1, 2, 3, and 4. Figure 8 In the image, (a) UV-Vis diffuse reflectance absorption spectra and (b) activity tests for VOCs removal of CTF-2, HM-UiO-66-NH2, and samples 1, 2, 3, and 4 are shown. Infrared spectra of samples before and after the VOCs removal activity test are shown: (c) Sample 1, (d) Sample 2, (e) Sample 3, and (f) Sample 4. Figure 9In the image, (a) SEM image and (c) magnified SEM image of microfibrillated cellulose aerogel; (b) SEM image and (d) magnified SEM image of HUCMA; (e) physical image of HUCMA; (f) infrared spectra of HM-UiO-66@CTF-2, microfibrillated cellulose aerogel and HUCMA. Figure 10 In the image, (a) the activity test of HM-UiO-66@CTF-2 and HUCMA for VOCs removal; (b) the cycle stability test of HUCMA; (c) GC-MS chromatograms of gases before and after VOCs adsorption and degradation by HUCMA; (d) GC-MS mass spectrum of gases before VOCs adsorption and degradation by HUCMA; and (e) GC-MS mass spectrum of gases after VOCs adsorption and degradation by HUCMA. Figure 11 In the image, (a) transient photoluminescence spectra of HM-UiO-66-NH2, CTF-2 and HM-UiO-66@CTF-2; (b) fluorescence lifetime spectrum of HM-UiO-66-NH2; (c) fluorescence lifetime spectrum of CTF-2; and (d) fluorescence lifetime spectrum of HM-UiO-66@CTF-2. Detailed Implementation

[0015] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0016] To address the technical problems mentioned in the background art, the present invention provides a method for preparing HM-UiO-66@CTF / MFC aerogel, comprising the following steps: Zirconium tetrachloride and 2-aminoterephthalic acid were added to a sodium dodecyl sulfate N,N-dimethylformamide solution and stirred at 30-40°C for 5-15 h. The mixture was then allowed to stand at 70-90°C for 5-20 h. The solid product was then washed to remove sodium dodecyl sulfate and dried to obtain HM-UiO-66-NH2. HM-UiO-66-NH2 was placed in an inert atmosphere and mixed with a chloroform solution of 4-cyanobenzoyl chloride. The mixture was stirred at 20-30°C for 0.1-1.5 h. Triethylamine was added dropwise and the mixture was stirred for another 5-15 h to obtain HM-UiO-66-CN. HM-UiO-66-CN was mixed with 4,4'-biphenylnitrile, and trifluoromethanesulfonic acid was added to prepare HM-UiO-66@CTF-2. The aqueous dispersion of HM-UiO-66@CTF-2 and the aqueous dispersion of microfibrillated cellulose were mixed evenly in a certain proportion and then freeze-dried to obtain HM-UiO-66@CTF / MFC aerogel.

[0017] Zirconium tetrachloride (ZrCl4) provides Zr 4+ The metal center and 2-aminoterephthalic acid (NH2-BDC) serve as organic ligands, and the two self-assemble through coordination bonds to form a three-dimensional network crystal structure. The reaction is stirred at 30-40℃ for 5-15 hours to ensure that the metal ions and ligands are fully mixed and to initially form MOF crystal nuclei. The reaction is then allowed to stand at 70-90℃ for 5-20 hours to promote crystal growth and structural stability, ultimately forming a UiO-66 framework with octahedral / tetrahedral cages.

[0018] SDS, acting as a surfactant, forms micelles in N,N-dimethylformamide (DMF), regulating the pore structure of the MOF through steric hindrance and avoiding the molecular stacking problem caused by the narrow pores of the original UiO-66. Washing with anhydrous ethanol or a hot DMF solution for 20-40 hours can effectively remove residual SDS from the pores, preventing pore blockage or impact on subsequent catalytic activity.

[0019] The expanded porous structure (a spherical structure with a rough surface and porous interior) exposes more buried catalytic sites, avoiding stacking during subsequent CTF-2 loading.

[0020] Placing HM-UiO-66-NH2 in an inert atmosphere (such as nitrogen) can prevent the amino group from being oxidized by oxygen in the air, ensuring the activity of the reaction site. The acyl chloride group in 4-cyanobenzoyl chloride undergoes a nucleophilic substitution reaction with the amino group on the surface of HM-UiO-66-NH2 to form an amide bond, while simultaneously introducing a cyano functional group.

[0021] First, the mixture is stirred at a low temperature of 20-30℃ to ensure that 4-cyanobenzoyl chloride is uniformly dispersed in chloroform and initially contacts the amino group on the surface of HM-UiO-66-NH2, avoiding agglomeration caused by excessively high local concentrations. After adding triethylamine, the reaction time is extended to ensure complete conversion of the amino group, ultimately generating HM-UiO-66-CN with cyano groups grafted onto its surface. Triethylamine acts as an acid-binding agent, neutralizing the HCl generated in the reaction and shifting the equilibrium towards the product.

[0022] The cyano groups grafted onto the surface of HM-UiO-66-CN and 4,4'-biphenyl nitrile (containing -CN) serve as reactants. Under the catalysis of trifluoromethanesulfonic acid (a strong protic acid), a trimerization reaction occurs, forming a triazine ring (a six-membered heterocycle containing three nitrogen atoms) to construct the CTF-2 framework. The sp2 hybridization and conjugated structure of the N atoms in the triazine ring endow the material with semiconductor properties and π-π interaction sites.

[0023] The cyano groups on the surface of HM-UiO-66-CN act as anchor sites, participating in the trimerization reaction simultaneously with the cyano groups of 4,4'-biphenylcarbamate, allowing CTF-2 to grow directly on the surface of HM-UiO-66, forming a core-shell structure. TEM characterization shows that HM-UiO-66@CTF-2 has a porous spherical morphology where HM-UiO-66 is encapsulated by CTF-2 sheets, verifying the in-situ growth process.

[0024] Trifluoromethanesulfonic acid, as a superacid, undergoes protonation of its cyano group to enhance its reactivity and promote the thermodynamic process of trimeric cyclization, while avoiding the introduction of metallic impurities. The triazine ring of CTF-2 exhibits strong electronegativity, forming a heterojunction with UiO-66 to promote photogenerated electron-hole separation; the C, N conjugated structure can adsorb VOCs (such as toluene) through π-π interactions, enhancing the material's adsorption-photocatalytic synergistic performance.

[0025] The generated HM-UiO-66@CTF-2 was freeze-dried with microfibrillated cellulose (MFC) to form an aerogel, solving the problem of difficult recycling of powder materials while retaining high specific surface area and porous structure. As the matrix material of the aerogel, MFC forms a three-dimensional network structure through the freeze-drying process, fixing HM-UiO-66@CTF-2 particles in the fiber skeleton, giving the material a macroscopic morphology and certain mechanical strength. The addition of MFC creates a loose porous structure inside the aerogel, preventing the agglomeration of HM-UiO-66@CTF-2 powder.

[0026] MFC itself has abundant hydroxyl groups and a porous structure, which can capture VOCs molecules through physical adsorption. It can also work synergistically with the π-π interaction of CTF-2 and the pore adsorption of UiO-66 to further improve the adsorption capacity of the material for VOCs.

[0027] In some embodiments, the concentration of sodium dodecyl sulfate in the N,N-dimethylformamide solution is 0.01-0.1 g / ml, preferably 0.03-0.07 g / ml.

[0028] SDS, as an anionic surfactant, can self-assemble into micellar structures in N,N-dimethylformamide (DMF). This alters the crystal growth process of UiO-66 through steric hindrance, inducing the formation of larger pores and a rougher surface. SDS participates in MOF synthesis through physical adsorption and can be effectively removed by washing with anhydrous ethanol or a hot DMF solution, preventing residual surfactant from clogging pores or affecting subsequent catalytic activity.

[0029] After pore enlargement, HM-UiO-66-NH2 forms a spherical structure with a rough surface and porous interior, exposing more buried Zr. 4+Active sites are provided to prevent sheet stacking due to space constraints during subsequent in-situ growth of CTF-2, ensuring that catalytic sites are fully exposed.

[0030] SDS is a common surfactant that is inexpensive and readily available. Its pore-forming process does not require complex equipment and can be achieved through simple stirring and washing, making it suitable for large-scale preparation.

[0031] In some embodiments, when preparing HM-UiO-66-NH2, the concentration of zirconium tetrachloride in the reaction system is 0.1-0.3 mol / L; the concentration of 2-aminoterephthalic acid is 0.05-0.2 mol / L.

[0032] Preferably, when preparing HM-UiO-66-NH2, the reaction is first stirred at 32-37℃ for 7-12 hours; then it is allowed to stand at 75-85℃ for 5-15 hours.

[0033] In some embodiments, the solid product is washed sequentially with anhydrous ethanol or N,N-dimethylformamide hot solution, N,N-dimethylformamide hot solution and anhydrous ethanol, each wash lasting 20-40 hours, to remove sodium dodecyl sulfate from the product.

[0034] In some embodiments, the method further includes washing HM-UiO-66-CN with chloroform, and after washing, drying it under vacuum at 20-30°C to obtain the final product.

[0035] The cyano and amide bonds grafted onto the surface of HM-UiO-66-CN are prone to decomposition or structural rearrangement at high temperatures. Low-temperature drying can prevent the destruction of functional groups, ensuring the activity of the trimerization sites in the subsequent reaction with 4,4'-biphenylnitrile. A vacuum environment lowers the boiling point of solvents (such as chloroform), allowing the solvent to evaporate rapidly at low temperatures and preventing pore collapse caused by high temperatures. Low-temperature conditions reduce the risk of oxidation of active sites on the material surface, while the vacuum environment prevents particle agglomeration caused by the adsorption of moisture from the air, maintaining the dispersibility of HM-UiO-66-CN.

[0036] In some embodiments, the mass ratio of HM-UiO-66-NH2, 4-cyanobenzoyl chloride, and triethylamine is 60-100:80-100:60-80.

[0037] In some embodiments, the mass ratio of HM-UiO-66-CN, 4,4'-biphenylnitrile, and trifluoromethanesulfonic acid is 1:3-12.

[0038] In some embodiments, when preparing HM-UiO-66@CTF-2, the raw materials are mixed and placed in a tube, cooled in an inert atmosphere, and then vacuumed and sealed. Place the tube in water to melt the mixture. If bubbles appear, continue to evacuate to ensure a vacuum environment. Then it is subjected to microwave heating reaction, with a heating power of 200-250W and a heating time of 1-5h; After the reaction is complete, the product is cooled in liquid nitrogen, washed with ammonia, anhydrous ethanol and tetrahydrofuran to remove impurities, and then dried to obtain the final product.

[0039] In some embodiments, the mass ratio of HM-UiO-66@CTF-2 to microfibrillated cellulose is 1:8-12.

[0040] Secondly, the present invention provides an HM-UiO-66@CTF / MFC aerogel, which is prepared by the aforementioned preparation method.

[0041] Thirdly, the present invention provides the application of the HM-UiO-66@CTF / MFC aerogel as a photocatalyst.

[0042] The present invention will be further described below with reference to the embodiments.

[0043] The raw materials used in the following examples: 4,4'-Biphenylcarboxynitrile was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. 4-Cyanobenzyl chloride, triethylamine, and trifluoromethanesulfonic acid were purchased from Beijing Bailingwei Technology Co., Ltd. Sodium dodecyl sulfate, ammonia, acetone, chloroform, tetrahydrofuran (THF), and N,N-dimethylformamide (DMF) were all purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai). Zirconium tetrachloride was purchased from Tianjin Xiens Biochemical Technology Co., Ltd. Microfibrillated cellulose was purchased from Guilin Qihong Technology Co., Ltd. All purchased chemical reagents were analytical grade and had not undergone further purification.

[0044] Example 1 Preparation method of HM-UiO-66@CTF / MFC aerogel, such as Figure 1 As shown: (1) Synthesis of HM-UiO-66-NH2: 2 g of sodium dodecyl sulfate was added to 40 mL of N,N-dimethylformamide, sonicated for 15 min, and stirred until dissolved. 6 mmol of zirconium tetrachloride and 3.5 mmol of 2-aminoterephthalic acid were added to the solution, and the mixture was stirred in an oil bath at 35 °C for 10 h. The solution was then placed in an oven at 80 °C without stirring overnight (12 h). The supernatant was filtered off, and the product was washed sequentially for 36 h with anhydrous ethanol / N,N-dimethylformamide hot solution, N,N-dimethylformamide hot solution, and anhydrous ethanol to remove sodium dodecyl sulfate. Finally, the product was dried in an oven at 110 °C to obtain HM-UiO-66-NH2.

[0045] The synthesis method of UiO-66-NH2 does not involve the addition of sodium dodecyl sulfate, and the remaining steps are consistent with the synthesis method of HM-UiO-66-NH2.

[0046] (2) Synthesis of HM-UiO-66@CTF-2: 80 mg of HM-UiO-66-NH2 was placed in a 25 mL round-bottom flask and purged with high-purity nitrogen under vacuum. 94 mg of 4-cyanobenzoyl chloride was weighed and added to 10 mL of chloroform, stirred thoroughly, and injected into the round-bottom flask. After stirring at 25 °C for 1 h, 100 μL of triethylamine was added dropwise to the solution in the round-bottom flask, and stirring was continued for another 10 h. The solution in the round-bottom flask was then removed, centrifuged at 8000 rpm, washed three times with chloroform, and dried under vacuum at 25 °C to obtain the product HM-UiO-66-CN.

[0047] 23.36 mg of product HM-UiO-66-CN was mixed with 94.3 mg of 4,4'-biphenylacetonitrile, and 88 μL (1 mmol) of trifluoromethanesulfonic acid was added. The remaining steps were the same as those for the synthesis of CTF-2 below, to obtain the final product HM-UiO-66@CTF-2.

[0048] Microwave-assisted synthesis of CTF-2: 102 mg (0.5 mmol) of 4,4'-biphenylnitrile and 88 μL (1 mmol) of trifluoromethanesulfonic acid were added to a Pyrex glass tube. The tube was cooled in a liquid nitrogen atmosphere, and the gas in the tube was evacuated using a vacuum pump. The tube was then sealed, and the contents were placed in a beaker containing water to melt the contents. Bubbles were observed appearing in the tube. The tube was then cooled again in liquid nitrogen, and the above process was repeated until no more bubbles appeared in the tube to ensure a vacuum environment. Afterward, the tube was microwaved in a microwave oven (Panasonic, model NN-GF33K) at 220W for 3 hours.

[0049] After the reaction, the sample was cooled in liquid nitrogen to reduce the pressure inside the Pyrex glass tube. Once cooled, the glass tube was opened and the sample removed. The microwaved sample was washed and centrifuged at least three times sequentially with 2 M ammonia solution, anhydrous ethanol, acetone, and tetrahydrofuran to remove impurities. After vacuum drying at 120 °C for 24 h, a yellow-green CTF-2 powder was obtained, with a yield close to 83%.

[0050] (3) Preparation of HM-UiO-66@CTF / MFC aerogel (HUCMA): 5 g of 2% microfibrillated cellulose (MFC) was added to 2 mL of ultrapure water and stirred to obtain an MFC suspension. 50 mg of HM-UiO-66@CTF-2 was dispersed in 3 mL of ultrapure water. The two dispersions were mixed, stirred at room temperature for 1 h, and then lyophilized to obtain HM-UiO-66@CTF / MFC aerogel (HUCMA). The entire preparation process of HUCMA is as follows: Figure 1 As shown.

[0051] Electrochemical testing: Electrochemical tests were conducted in a 150 mL single-layer optical quartz window electrolytic cell, with 100 mL of 3M KCl aqueous solution added as the electrolyte. A standard three-electrode system was used, with a platinum sheet electrode as the counter electrode and Ag / AgCl as the reference electrode. Electrochemical curves were recorded using a Shanghai Chenhua electrochemical workstation (CHI 660E).

[0052] 10 mg of sample was dispersed in 1000 μL of anhydrous ethanol, and 20 μL of naphthol was added as a film-forming agent. The mixture was sonicated for 15 min to prepare a homogeneous suspension of various materials. 50 μL of the suspension was uniformly drop-coated onto the conductive surface of a 1 cm × 3 cm rectangular ITO glass slide and allowed to evaporate and dry at room temperature to prepare the working electrode. Transient photocurrent measurement was performed using a 300 W xenon lamp equipped with a 435 nm cutoff filter as the light source. The material on the working electrode was illuminated by the lamp, and the photocurrent signal was obtained by recording the IT curve. During the test, a photoelectric switch was used to switch the light source on and off at fixed intervals, and the current values ​​were recorded. The Mott-Schottky experiment was conducted at frequencies of 500, 7500, and 1000 Hz. The calculated potential of NHE was converted to the potential of Ag / AgCl using the following formula, where E0Ag / AgCl = 0.199 V: E NHE =E Ag / AgCl + E 0 Ag / AgCl ………… (1); Photocatalytic performance test: The prepared material was used as a photocatalyst to perform adsorption-photocatalytic degradation experiments on toluene in simulated VOCs. The specific operation was as follows: 20 mg of the material was placed in a 2 L quartz round-bottom flask, a certain amount of toluene was injected into the flask, and the flask was sealed with a rubber stopper. Dark adsorption was performed for a period of time, and after equilibrium was reached, a 435 nm lamp source was turned on to test the photocatalytic degradation. From the start of dark adsorption, 1 mL of gas from the flask was extracted using a gas microsyringe at regular intervals and injected into a gas chromatograph for VOC content analysis.

[0053] To evaluate the material's adsorption photocatalytic performance for toluene in simulated VOCs, we calculated its adsorption photocatalytic degradation efficiency using equations: η = (1-C t / C0)×100%……(2); In the above equation, η (%) represents the adsorption photocatalytic degradation efficiency, and C0 and C t (mg / cm) 3 ) represent the initial concentration of volatile organic pollutants and the concentration of volatile organic pollutants at time t (min), respectively.

[0054] Cyclic stability test: After the adsorption-photocatalytic performance test, 20 mg of material was removed from the quartz round-bottom flask, placed in a centrifuge tube, and sealed with sealing film for storage. The quartz round-bottom flask was washed and dried in a 60 °C oven. The material was then placed back into a 2 L quartz round-bottom flask, and an equal amount of volatile organic pollutants was injected into the flask. The flask was sealed with a rubber stopper, and the adsorption-photocatalytic degradation performance test was conducted under the same conditions. This cycle was repeated for a total of 5 consecutive adsorption-photocatalytic degradation tests to evaluate the recyclability and cycle stability of the material.

[0055] Structural advantages: The molecular size of various VOCs is usually measured by kinetic diameter (equivalent diameter of gas molecules in motion), ranging from approximately 0.3 nm (3 Å) to 1.2 nm (12 Å). To avoid excessive VOC molecules accumulating and clogging adsorption and active sites within the pores of UiO-66-NH2, we added a surfactant (sodium dodecyl sulfate) to create pores during the synthesis of UiO-66-NH2, thus controlling its porosity to obtain HM-UiO-66-NH2. SEM and TEM measurements were performed, such as... Figure 2 As shown, UiO-66-NH2 is a solid spherical structure with a smooth surface and no obvious pores, while HM-UiO-66-NH2 is a spherical structure with a rough surface and many pores inside. The size of both is about 100-200 nm.

[0056] BET tests were performed on UiO-66-NH2 and HM-UiO-66-NH2. The results (as shown in Table 1) indicate that UiO-66-NH2 has an average pore size of 5.88 nm and a specific surface area of ​​342.63 m². 2 ·g -1 The average pore size of HM-UiO-66-NH2 increased to 7.05 nm, and the specific surface area was 397.16 m². 2 ·g -1 The pore volume increases. The nitrogen isotherm adsorption curves for both were obtained from nitrogen isotherm adsorption / desorption experiments. Figure 3 All of them conform to the Type IV adsorption isotherm model, that is, the characteristic curve of mesoporous adsorbent materials. Therefore, HM-UiO-66-NH2 with pore expansion, larger pore size and larger specific surface area was successfully prepared by using sodium dodecyl sulfate to create pores during the synthesis process.

[0057] Table 1. Pore structure characterization parameters of UiO-66-NH2 and HM-UiO-66-NH2

[0058] To improve the light absorption capacity and electron-hole separation efficiency of HM-UiO-66-NH2, CTF-2 was synthesized in situ on its surface using microwave assistance, yielding HM-UiO-66@CTF-2. Morphological characterization of the sample was performed; SEM images showed that CTF-2 exhibited a two-dimensional layered structure (e.g., ...). Figure 4 As shown in Figure a), there is severe stacking between layers. HM-UiO-66@CTF-2 is a spherical structure encapsulated by layers (as shown in Figure a). Figure 4 As shown in b). TEM characterization allows for a more intuitive observation of the layered structure of CTF-2 (e.g., ...). Figure 4 As shown in c), HM-UiO-66@CTF-2 is a porous spherical structure with a diameter of approximately 400 nm encapsulated by sheets (as shown in c). Figure 4 As shown in d), the morphology of this sheet is consistent with that of CTF-2 under TEM. Therefore, it can be preliminarily concluded that CTF-2 was successfully loaded on the surface of porous UiO-66 (HM-UiO-66) under microwave-assisted conditions, but its synthesis ratio still needs to be further adjusted.

[0059] Table 2. Reaction parameters for preparing HM-UiO-66@CTF-2 at different synthesis ratios.

[0060] Based on the experimental parameters in Table 2, HM-UiO-66@CTF-2 samples with different molar ratios of HM-UiO-66-CN and 4,4'-biphenylcarbamate were prepared. The HM-UiO-66@CTF-2 samples prepared with different reactant molar ratios were numbered 1, 2, 3, and 4, respectively. The prepared samples were characterized by morphology and subjected to SEM analysis (e.g., ...). Figure 5 ad) and the corresponding TEM test (e.g. Figure 5 The results showed that as the amount of CTF-2 monomer (4,4'-biphenylnitrile) added to the reaction raw materials increased, CTF-2 plate-like particles of about 50 nm appeared on the surface of HM-UiO-66 in sample 1, the number of CTF-2 plate-like particles on the surface of HM-UiO-66 increased in sample 2, the layered structure of CTF-2 plates began to appear on the surface of HM-UiO-66 in sample 3, and the number of CTF-2 plates increased in sample 4, which began to coat HM-UiO-66.

[0061] Perform XRD tests on the samples (e.g.) Figure 6 As shown in Figure ab), the strong characteristic peaks of HM-UiO-66-NH2 at 7.3° and 8.5° correspond to the (111) and (200) crystal planes of the material, respectively. This result is consistent with UiO-66-NH2, indicating that they have the same crystal structure. The XRD peaks of samples 1, 2, 3, and 4 are shifted to the left, indicating that their lattice constant and interplanar spacing are larger. This is due to lattice expansion, which is related to the in-situ growth of CTF-2 on HM-UiO-66. Infrared characterization shows that the characteristic absorption peaks of CTF-2 (such as those shown in Figure ab) appear in samples 1, 2, 3, and 4. Figure 6 (as shown in c), which are located at 2220 cm. -1 The characteristic absorption peaks of the -CN bond at 750-1500 cm⁻¹ -1 The characteristic peaks of the three triazine bonds are visible at 661 cm⁻¹. -1 A redshift of the characteristic absorption peak of Zr-O bonds was observed at [value missing], presumably due to bonding formed by CTF-2 growth on its surface. Sample 4 showed absorption peaks at 1653, 1583, 1386, and 769 cm⁻¹. 1 Peaks at such locations (e.g.) Figure 6 The peaks (as shown in d) are attributed to the tensile vibration peak of C=O, the asymmetric vibration peak of C=O, the vibration peak of aromatic CCC, and the bending vibration peak of aromatic CH2 in UiO-66, respectively. This conclusion is consistent with the XRD spectral analysis results. In summary, HM-UiO-66@CTF-2 has been successfully prepared.

[0062] like Figure 7As shown in Figure ab, the HRTEM image clearly shows the lattice fringes of HM-UiO-66 and CTF-2 within HM-UiO-66@CTF-2, as well as the heterostructure boundary between them. This demonstrates the formation of a heterostructure between HM-UiO-66 and CTF-2 within HM-UiO-66@CTF-2, and indicates that HM-UiO-66@CTF-2 possesses good crystallinity. Nitrogen isothermal adsorption-desorption tests were performed on the sample. The nitrogen isothermal adsorption curve (…) Figure 7 As shown in c), samples 1, 2, 3, and 4 all conform to Type V adsorption isotherms. At lower P / P0, the shape of the Type V isotherm is very similar to that of Type III, which is due to the relatively weak interaction between the adsorbent material and the adsorbed gas. At higher relative pressures, there is an inflection point, which is caused by clusters of molecules filling the channels, indicating that CTF-2 also grows within the channels of HM-UiO-66@CTF-2.

[0063] Next, the VOCs removal performance of HM-UiO-66@CTF-2 was investigated. First, the UV-Vis diffuse reflectance absorption spectrum of the sample was measured. The results showed ( Figure 8 In section a), beyond 424 nm, the absorption intensity of HM-UiO-66-NH2 for visible light decreases linearly, while the prepared HM-UiO-66@CTF-2 materials (samples 1, 2, 3, and 4) and CTF-2 still exhibit significant absorption intensity in the visible light region. Therefore, using visible light at 435 nm (greater than 428 nm), the materials were subjected to a concentration of 1000 mg / m². 3 Photocatalytic adsorption degradation activity of toluene was tested. The test results showed that ( Figure 8 In section b), the adsorption capacity for VOCs (taking toluene as an example) is: 4 > 3 > HM-UiO-66-NH2 > 2 > 1 > CTF-2. The removal capacity for VOCs (taking toluene as an example) is: 4 > 3 > CTF-2 > 2 > 1 > HM-UiO-66-NH2. In summary, HM-UiO-66-NH2 exhibits the best adsorption performance, but it has almost no photocatalytic activity. CTF-2 shows the fastest photocatalytic removal rate of VOCs after illumination, but its adsorption performance is poor.

[0064] For the prepared HM-UiO-66@CTF-2 material, the adsorption and photocatalytic performance showed an increasing trend with the increase of the 4,4'-biphenylcarbamate monomer. Infrared characterization tests were performed on the material before and after the VOCs removal activity test, and the results showed (…). Figure 8HM-UiO-66@CTF-2 exhibits good stability, with no significant structural changes before and after the reaction. Therefore, HM-UiO-66@CTF-2 can remove VOCs through excellent adsorption performance and photocatalytic synergy, while maintaining structural stability during the VOCs removal process.

[0065] In VOCs removal applications, the recyclability of materials is a key factor determining their practical application value. To address the difficulty of recycling powdered materials in VOCs removal applications, based on the experimental results of the above materials' VOCs removal activity tests, sample No. 4, which showed the best removal effect, was mixed with microfibrillated cellulose and directly freeze-dried to obtain HM-UiO-66@CTF-2 / MFC aerogel (HUCMA). SEM observations revealed... Figure 9 The surface of the microfibrillated cellulose aerogel is smooth, and its internal structure is compact. However, due to the addition of HM-UiO-66@CTF-2, larger pores were formed during the freeze-drying process, resulting in a looser internal structure for HUCMA. Figure 9 The image shown is of HUCMA, which is lightweight and slightly elastic. Infrared spectrum ( Figure 9 In the middle f), HUCMA showed characteristic peaks of both HM-UiO-66@CTF-2 and microfibrillated cellulose aerogel, confirming the successful preparation of HUCMA.

[0066] Performance advantages: The removal capacity of HUCMA for VOCs (using toluene as an example) was further investigated. Test results ( Figure 10 As shown in Figure a), the adsorption performance of HUCMA increased from 45% to 57% compared to HM-UiO-66@CTF-2. This was achieved after five cycles of testing (e.g., ...). Figure 10 As shown in Figure b), the U@C / MFC aerogel still exhibits high adsorption and degradation activity for toluene and good stability. To investigate whether other byproducts are generated after the reaction, 4% 1,4-butanediol was used as the absorbent to collect the gases before and after the reaction. The gas components before and after the reaction were analyzed by gas chromatography-mass spectrometry (GC-MS). Figure 10 (Ce). The results showed that only the concentration of toluene decreased after the reaction, and no other byproducts other than toluene were detected. In summary, HUCMA has excellent VOCs removal capabilities, and its good stability ensures a long service life in VOCs removal applications.

[0067] Next, we will investigate the reaction mechanism of HUCMA in the adsorption and degradation of VOCs. First, we will characterize the sample by photoluminescence spectroscopy. Figure 11As can be seen from Figure a, HM-UiO-66@CTF-2 has the largest peak area in the PL spectrum, indicating its highest quantum yield. This is attributed to the introduction of triazine structural units by loading CTF-2, thereby improving the material's light utilization efficiency. Subsequently, fluorescence lifetime tests were performed on the material, such as... Figure 11 As shown in Figure bd, the fluorescence lifetime of HM-UiO-66@CTF-2 falls between that of HM-UiO-66 and CTF-2, indicating that the presence of HM-UiO-66 effectively reduces the electron-hole recombination rate of the material. Analysis of the heterojunction interface captured by HRTEM suggests that the effective reduction in the electron-hole recombination rate of HM-UiO-66@CTF-2 may be due to interfacial charge transfer within the heterojunction.

[0068] Mechanism studies revealed that the possible reaction mechanism for VOCs removal by HUCMA is as follows: HUCMA photocatalytically oxidizes and degrades toluene in VOCs into carbon dioxide and water through simple visible light irradiation. HM-UiO-66 and microfibrillated cellulose play the main adsorption roles, while the loading of CTF-2 introduces triazine structural units. The stable conjugated structure between C and N atoms can undergo π-π interactions with benzene compounds in VOCs, improving the material's selective adsorption of VOCs (taking toluene as an example). The high adsorption capacity of the material enriches VOCs on HM-UiO-66@CTF-2. When HM-UiO-66@CTF-2 is irradiated with visible light, electron-hole pairs are separated. Photogenerated electrons are transferred from CTF-2 to HM-UiO-66, where oxygen reduction occurs, generating superoxide radicals. Some of the photogenerated holes oxidize water in the air to produce hydroxyl radicals, while others directly oxidize VOCs. Superoxide radicals, hydroxyl radicals, and photogenerated holes are all active substances for oxidizing and degrading VOCs, thus achieving highly efficient removal of VOCs.

[0069] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing HM-UiO-66@CTF / MFC aerogel, characterized in that: Includes the following steps: Zirconium tetrachloride and 2-aminoterephthalic acid were added to a sodium dodecyl sulfate N,N-dimethylformamide solution and stirred at 30-40°C for 5-15 h. The mixture was then allowed to stand at 70-90°C for 5-20 h. The solid product was then washed to remove sodium dodecyl sulfate and dried to obtain HM-UiO-66-NH2. HM-UiO-66-NH2 was placed in an inert atmosphere and mixed with a chloroform solution of 4-cyanobenzoyl chloride. The mixture was stirred at 20-30°C for 0.1-1.5 h. Triethylamine was added dropwise and the mixture was stirred for another 5-15 h to obtain HM-UiO-66-CN. HM-UiO-66-CN was mixed with 4,4'-biphenylnitrile, and trifluoromethanesulfonic acid was added to prepare HM-UiO-66@CTF-2. The aqueous dispersion of HM-UiO-66@CTF-2 and the aqueous dispersion of microfibrillated cellulose were mixed evenly in a certain proportion and then freeze-dried to obtain HM-UiO-66@CTF / MFC aerogel.

2. The preparation method of HM-UiO-66@CTF / MFC aerogel according to claim 1, characterized in that: In the N,N-dimethylformamide solution of sodium dodecyl sulfate, the concentration of sodium dodecyl sulfate is 0.01-0.1 g / ml, preferably 0.03-0.07 g / ml.

3. The preparation method of HM-UiO-66@CTF / MFC aerogel according to claim 1, characterized in that: When preparing HM-UiO-66-NH2, the concentration of zirconium tetrachloride in the reaction system is 0.1-0.3 mol / L; the concentration of 2-aminoterephthalic acid is 0.05-0.2 mol / L. Preferably, when preparing HM-UiO-66-NH2, the reaction is first stirred at 32-37℃ for 7-12 hours; then it is allowed to stand at 75-85℃ for 5-15 hours.

4. The preparation method of HM-UiO-66@CTF / MFC aerogel according to claim 1, characterized in that: The solid product was washed sequentially with anhydrous ethanol or N,N-dimethylformamide hot solution, N,N-dimethylformamide hot solution and anhydrous ethanol, for 20-40 hours each time, to remove sodium dodecyl sulfate from the product.

5. The method for preparing HM-UiO-66@CTF / MFC aerogel according to claim 1, characterized in that: It also includes the step of washing HM-UiO-66-CN with chloroform. After washing, it is vacuum dried at 20-30℃ to obtain the product. Alternatively, the mass ratio of HM-UiO-66-NH2, 4-cyanobenzoyl chloride, and triethylamine is 60-100:80-100:60-80.

6. The method for preparing HM-UiO-66@CTF / MFC aerogel according to claim 1, characterized in that: To prepare HM-UiO-66@CTF-2, the raw materials were mixed and placed in a tube, which was then cooled in an inert atmosphere, and then vacuumed and sealed. Place the tube in water to melt the mixture. If bubbles appear, continue to evacuate to ensure a vacuum environment. Then it is subjected to microwave heating reaction, with a heating power of 200-250W and a heating time of 1-5h; After the reaction is complete, the product is cooled in liquid nitrogen, washed with ammonia, anhydrous ethanol and tetrahydrofuran to remove impurities, and then dried to obtain the final product.

7. The method for preparing HM-UiO-66@CTF / MFC aerogel according to claim 1, characterized in that: The mass ratio of HM-UiO-66-CN, 4,4'-biphenylnitrile, and trifluoromethanesulfonic acid is 1:3-12.

8. The method for preparing HM-UiO-66@CTF / MFC aerogel according to claim 1, characterized in that: The mass ratio of HM-UiO-66@CTF-2 to microfibrillated cellulose is 1:8-12.

9. An HM-UiO-66@CTF / MFC aerogel, characterized in that: It is prepared by any one of the preparation methods described in claims 1-8.

10. The application of the HM-UiO-66@CTF / MFC aerogel according to claim 9 as a photocatalyst.

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