TiO2@Ag / Ti-MOF functional material and preparation method thereof

Abstract

Photocatalytic sterilization technology is a technology that uses active substances generated by specific materials under light conditions to kill bacteria, viruses and other microorganisms. This technology mainly relies on the performance of photocatalytic materials, especially semiconductor materials such as titanium dioxide (TiO2). When the photocatalyst is irradiated by light of a specific wavelength, the electrons in the material transition from the valence band to the conduction band, forming electron-hole pairs. These electrons and holes have high chemical activity and can react with water or oxygen to generate free radicals with strong oxidizing ability, which can destroy the cell wall or cell membrane of microorganisms, causing the leakage of intracellular substances, thereby achieving the effect of sterilization. The present application aims to solve the problems of low light utilization rate and insufficient active sites of TiO2 photocatalytic materials, and proposes a TiO2@Ag / Ti-MOF functional material. The TiO2@Ag / Ti-MOF functional material is based on the Ti-MOF skeleton to construct Ag-MOF, realizing the controlled slow release of Ag ions and having a long-term effective sterilization effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of photocatalytic sterilization materials, in particular to a TiO2@Ag / Ti-MOF functional material and a preparation method thereof. BACKGROUND

[0002] Photocatalytic sterilization technology is a technology that converts light energy into chemical energy. When light is irradiated on a semiconductor photocatalytic material, if the energy of the irradiated light is greater than the excitation energy of the photocatalytic material, the electrons (e - ) in the valence band (VB) of the semiconductor photocatalytic material will be excited to the conduction band (CB) to form photoexcited electrons, while holes (h + ) are left in the valence band (VB). Subsequently, the photoelectron and hole pairs will migrate to the surface of the semiconductor photocatalytic material to participate in reduction and oxidation reactions. The active free radicals ROS (•OH, •O2 - , •HO2) generated by the reaction can make the bacteria lose activity by attacking biological macromolecules such as bacterial cell membranes, proteins and DNA, thereby killing bacterial pathogens.

[0003] As the earliest and most widely studied photocatalytic antibacterial material, TiO2 has a series of advantages such as strong photocatalytic sterilization activity, long antibacterial time, and high human affinity, and is an excellent sterilization material. As a kind of N-type semiconductor, TiO2 is a natural photocatalytic sterilization material. Studies have shown that under the irradiation of ultraviolet light, TiO2 will form ROS with strong oxidizing properties on its surface, which will spontaneously attack biological macromolecules such as bacterial phospholipids, proteins and nucleic acids, and the bacterial cell membrane, cytoplasm and organelles will be destroyed in turn, thereby achieving a persistent and efficient harmless treatment of bacteria. However, the low light utilization rate and insufficient active reaction sites of TiO2 photocatalytic material result in great energy waste, which limits the application of this kind of material. SUMMARY

[0004] Based on the above, in view of the problems of low light utilization rate and insufficient active reaction sites of TiO2 photocatalytic material, the present application provides a TiO2@Ag / Ti-MOF functional material and a preparation method thereof. The TiO2@Ag / Ti-MOF functional material is based on the Ti-MOF skeleton to construct Ag-MOF, realizing the controlled slow release of Ag ions and having a long-term effective sterilization effect.

[0005] One of the technical solutions of the present application is to provide a TiO2@Ag / Ti-MOF functional material, which has a core-shell structure, the core is TiO2, and the shell is a silver-substituted Ti-MOF structure. There is a tight interface between the core and the shell, which can efficiently capture photo-generated electrons generated after TiO2 irradiation, and the silver ions in the MOF are reduced to silver atoms, enhancing the sterilization performance.

[0006] The second technical solution of the present application provides a preparation method of TiO2@Ag / Ti-MOF functional material, which specifically comprises the following steps:

[0007] (1) preparing Ti-MOF with Ti vacancies by a microwave hydrothermal method;

[0008] (2) filling the Ti vacancies on the surface layer with silver ions to form a Ti vacancy-MOF@Ag / Ti-MOF structure;

[0009] (3) heating the Ti-MOF@Ag / Ti-MOF structure to form a TiO2@Ag / Ti-MOF structure.

[0010] Further, the Ti-MOF with Ti vacancies is prepared by the following method:

[0011] 1) preparing 2-amino terephthalic acid with a concentration of 0.2-0.3 mmol / mL in N, N-dimethyl imidazole (DMF) as solution A;

[0012] 2) dissolving tetrabutyl titanate in anhydrous methanol, mixing uniformly to obtain solution B; the volume ratio of tetrabutyl titanate to anhydrous methanol is 1: (22-28);

[0013] 3) mixing solution A and solution B according to a molar ratio of tetrabutyl titanate to 2-amino terephthalic acid of 1: (0.2-5); after mixing uniformly, transferring to a microwave oven, heating for 2 hours at a microwave power of 600 W, drying the precipitate to obtain Ti-MOF with Ti vacancies.

[0014] Further, the Ti vacancy-MOF@Ag / Ti-MOF structure is prepared by the following method: dispersing Ti-MOF with Ti vacancies in a silver ammonia solution, transferring to a sealed container, and filling the solution to more than 2 / 3 of the container volume; reacting at 80°C for 240-300 minutes to obtain a Ti vacancy-MOF@Ag / Ti-MOF structure.

[0015] Further, the concentration of the silver ammonia solution is 1-3 mol / L; the mass fraction of Ti-MOF with Ti vacancies in the solution is 14-35%.

[0016] Further, in step 3 of the preparation method of TiO2@Ag / Ti-MOF functional material, the heating of the Ti-MOF@Ag / Ti-MOF structure is transferring the Ti-MOF@Ag / Ti-MOF structure to a tube furnace, performing heat treatment at 200-300°C in an air environment to obtain a TiO2@Ag / Ti-MOF structure.

[0017] In the process of preparing Ti-MOF with Ti vacancies, a Ti-MOF with Ti vacancies is formed by using 2-amino terephthalate as a ligand, N, N-dimethyl imidazole as a solvent, and a microwave hydrothermal method, Ti 4+ The octahedral configuration of the Ti-based material utilizes multiple coordination sites to connect two unit fragments into a chain through oxygen atoms on the carboxyl groups, and the metal-ligand bonding and rigid framework exhibit good redox activity, good structural stability, and coordination diversity. The high-frequency electromagnetic energy of the microwave has penetration, which makes the molecules vibrate and rub, efficiently heats, reduces the activation energy barrier, and accelerates the crystallization speed, thereby reducing the sample grain size and improving the uniformity. Moreover, the microwave heating not only provides energy to accelerate the reaction, but also may promote the restructuring or instability of the structure due to the local high temperature and pressure environment, indirectly leading to the formation of Ti vacancies.

[0018] Subsequently, silver ions are used to fill the Ti vacancies on the surface layer, and this step is carried out in a sealed container. During the reaction, the vapor pressure in the solution increases, effectively promoting the diffusion and penetration of silver ions in the silver ammonia solution into the Ti-MOF. The high temperature and pressure environment at 80 ℃ can reduce the resistance of gas molecules in the MOF channel, making it easier for silver ions to enter and contact the vacancies, thereby filling the Ti vacancies on the surface layer. At the same time, the silver ions are reduced to silver atoms, which are then "fixed" on the titanium vacancies. This reduction process, combined with the ammonia complex in the silver ammonia solution, can effectively promote the deposition and stability of silver.

[0019] During the heating process of the Ti-MOF@Ag / Ti-MOF structure, the outer Ag / Ti-MOF maintains the original structure due to its good crystallinity, while the vacancies in the inner layer have defects and form TiO2 under hot air, ultimately forming a core-shell structure with Ag / Ti-MOF as the shell and TiO2 as the core.

[0020] The beneficial effects of the present application are that Ag-MOF is constructed based on the Ti-MOF framework, realizing the controlled release of Ag ions, and having a long-term effective sterilization effect. Further, a composite structure with Ag-MOF as the shell and TiO2 as the core is constructed, and there is a tight interface between the core and the shell, which can efficiently capture the photo-generated electrons generated by TiO2 under light irradiation, and the silver ions in the MOF are reduced to silver atoms, enhancing the sterilization performance. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 TEM images of Ti-MOF and Example 1;

[0022] Figure 2 EDS images of Example 1;

[0023] Figure 3 XRD spectra of Ti-MOF and Example 1;

[0024] Figure 4 FT-IR images of Ti-MOF and Example 1;

[0025] Figure 5 XPS spectra of Ti-MOF and Example 1 material of each element orbit;

[0026] Figure 6 Bactericidal effect diagram of TiO2, Ti-MOF, Ti-MOF@Ag / Ti-MOF and TiO2@Ag / Ti-MOF. DETAILED DESCRIPTION

[0027] The following examples are intended to further illustrate the present application and are not intended to limit the scope of the present application. Unless otherwise indicated, parts and percentages in the following examples are by weight.

[0028] The raw materials used in the present application are all conventional commercially available products unless otherwise specified; the methods used in the present application are all conventional methods in the art unless otherwise specified.

[0029] It should be noted that the described embodiments are merely a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0030] The terms used in the embodiments of the present application are merely for the purpose of describing the specific embodiments, and are not intended to limit the present application. The singular forms "a", "an" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0031] Example 1

[0032] 1) 2-amino terephthalic acid with a concentration of 0.2 mmol / mL in N, N-dimethylformamide (DMF) as solution A;

[0033] 2) Take tetrabutyl titanate dissolved in anhydrous methanol, mix uniformly to obtain solution B; the volume ratio of tetrabutyl titanate and anhydrous methanol is 1:22;

[0034] 3) According to the molar ratio of tetrabutyl titanate and 2-amino terephthalic acid 1:0.2, mix solution A and solution B; after mixing uniformly, transfer to a microwave oven, set the microwave power to 600W, and set the heating time to 2 hours; dry the precipitate to obtain Ti-MOF with Ti vacancies;

[0035] 4) Ti-vacancy Ti-MOF is dispersed in 1 mol / L silver ammonia solution, the mass fraction of Ti-vacancy Ti-MOF in the solution is 14%, the mixed solution is transferred to a sealed container, and the solution is filled to more than 2 / 3 of the volume of the container;

[0036] 5) reaction at 80℃ for 240 minutes to obtain Ti-vacancy-MOF@Ag / Ti-MOF structure;

[0037] 6) Ti-MOF@Ag / Ti-MOF is transferred to a tube furnace and heat treated at 200℃ in air to obtain TiO2@Ag / Ti-MOF structure.

[0038] The obtained product TiO2@Ag / Ti-MOF is then characterized.

[0039] Figure 1 a and Figure 1 b are TEM images of Ti-MOF and Ti-MOF@Ag / Ti-MOF materials, respectively. It can be observed that the Ti-MOF material has a solid structure inside and a smooth surface. Figure 1 c is a TEM image of TiO2@Ag / Ti-MOF composite material. Compared with Ti-MOF material, the smooth surface of TiO2@Ag / Ti-MOF composite material is converted into a relatively rough surface with fine crystalline particles, and the size is significantly reduced. Figure 1 d is an HRTEM image of TiO2@Ag / Ti-MOF. It is measured that TiO2@Ag / Ti-MOF has Ag nanoparticle lattice (200) crystal face, and the crystal face spacing is 2.05 Å.

[0040] Figure 2 d-g are EDS images of TiO2@Ag / Ti-MOF. Figures d-g represent the distribution of C, O, Ti and Ag, respectively, proving that C, O, Ti and Ag elements are uniformly distributed in TiO2@Ag / Ti-MOF functional material, wherein C, O and Ti elements are basic elements of Ti-MOF material, and Ag element is nano Ag particle loaded by microwave solvent thermal method.

[0041] According to Figure 3The XRD spectrum of TiO2@Ag / Ti-MOF composite material can be seen that compared with Ti-MOF, TiO2@Ag / Ti-MOF composite material retains the main peak of Ti-MOF at about 6.5° and the continuous peak near 20°, the peaks at 25.6°, 48.7°, 63.1° and 63.7° belong to the (101) crystal face, (200) crystal face, (213) crystal face and (204) crystal face of TiO2 rutile phase respectively, indicating that TiO2@Ag / Ti-MOF composite material exists TiO2 rutile phase, and at the same time retains a part of Ti-MOF crystal structure.

[0042] Figure 4 The FT-IR image of TiO2@Ag / Ti-MOF composite material shows that there is a certain organic skeleton component in the TiO2@Ag / Ti-MOF composite material. As shown in Figure 4 the absorption peaks at 3450 cm -1 and 1620 cm -1 in the spectrum of TiO2 material are caused by the stretching vibration of hydroxyl (-OH) and the bending vibration of H-O-H bond of water, which is due to the absorption of water by the material exposed to air. For Ti-MOF and TiO2@Ag / Ti-MOF, the wide absorption peak at 3400 cm -1 in the spectrum is caused by the stretching vibration of hydroxyl (-OH) and amino (-NH2) of water, the absorption peak at 2925 cm -1 is caused by the stretching vibration of C-H bond in aldehyde group (-CHO), the infrared absorption peaks at 1640 cm -1 and 1420 cm -1 are caused by the asymmetric and symmetric stretching vibration of O-C=O bond, and the absorption peak at 1080 cm -1 is caused by the vibration of C-O bond. From the above conclusion, it can be seen that there is an organic skeleton component in TiO2@Ag / Ti-MOF composite material, which proves the successful synthesis of TiO2@Ag / Ti-MOF material.

[0043] Figure 5 The XPS energy spectrum of each element orbit in Ti-MOF and TiO2@Ag / Ti-MOF materials is used to prove the structure of TiO2@Ag / Ti-MOF material and the change of each element type and coordination environment. Figure 5 a~d are the XPS energy spectrum of C 1s, O1s, N 1s and Ti 2p in Ti-MOF material, Figure 5 the high-resolution spectrum of C 1s in a can be fitted as four convolution peaks of 284.8 eV, 285.6 eV, 286.2 eV and 288.9 eV, which correspond to the peaks of C-C / C-H, C-N, C=C and O-C=C respectively. Figure 5The O 1s peak in b can be fitted into peaks with binding energies of 530.1 eV, 532.0 eV and 532.4 eV, which correspond to characteristic peaks of Ti-O, C=O and -OH hydroxyl groups, respectively. Figure 5 The N 1s peak in c can be distinguished into peaks with binding energies of 399.5 eV and 402.5 eV, which correspond to -NH2 and -NH += / -NH +- characteristic peaks, respectively. Figure 5 The peaks with binding energies of 458.8 eV and 464.5 eV in d belong to Ti 2p orbitals due to the spin splitting of electrons. Figure 5 f-i are C 1s, O 1s, N 1s, Ti 2p and Ag 3d XPS energy spectra in the TiO2@Ag / Ti-MOF material, respectively, compared with the peaks of the corresponding elements in the Ti-MOF material, Figure 5 In e, the characteristic peaks of C-C / C-H, C-N and C=C in the C 1s energy spectrum have binding energies of 284.6 eV, 285.0 eV and 285.9 eV, which decrease by 0.2 eV, 0.6 eV and 0.3 eV, respectively, and only the O-C=C binding energy increases slightly by 0.1 eV, which is 289.0 eV. Figure 5 In f, the characteristic peaks of Ti-O, C=O and -OH hydroxyl groups in the O 1s have binding energies of 529.9 eV, 530.5 eV and 532.0 eV, respectively, which decrease by 0.5 eV, 1.5 eV and 0.4 eV, respectively. Figure 5 In g, the characteristic peaks of -NH2 and -NH += / -NH +- in e, the characteristic peaks of -NH2 and -NH Figure 5 In h, the binding energies of Ti 2p orbitals are 459.0 eV and 464.8 eV, which increase by 0.2 eV and 0.3 eV, respectively. Figure 6 In i, the binding energy difference of Ag 3d orbitals is 6.0 eV, which proves that the elemental Ag nanoparticles are successfully loaded in the TiO2@Ag / Ti-MOF material.

[0044] In summary, it can be proved that the preparation method described in the present application can successfully synthesize a photocatalytic functional material with a core-shell structure of TiO2 as the core and Ag-substituted Ti-MOF as the shell.

[0045] In order to test the photocatalytic bactericidal performance of the prepared material, gram-negative bacillus E. coli was selected as the test strain, and photocatalytic bactericidal drugs (TiO2, Ti-MOF, Ti-MOF@Ag / Ti-MOF or TiO2@Ag / Ti-MOF) 50 μg / mL, E. coli liquid 107 The cfu / mL was observed after the mixed solution was cultured at 37 °C for 24 h after being irradiated for different times. The mixed solution without the photocatalytic drug was the blank control group. The photocatalytic sterilization results are shown in Table 1 ​ As shown in Table 1, under the light condition, the sterilization rates of pure TiO2 and pure Ti-MOF were only 14.3% and 2.7%, respectively, indicating that the pure Ti-MOF material almost had no sterilization capacity, and the photocatalytic sterilization efficiency of the pure TiO2 was low due to its excessively wide band gap and low utilization rate of photo-generated electrons and holes. The loaded nano-Ag particles acted as active sites, which could promote the adsorption and activation of O2, enrich electrons, and reduce the recombination rate of photo-generated electrons and holes. The sterilization efficiency of the Ti-MOF@Ag / Ti-MOF composite material was significantly improved compared with that of the pure TiO2 and pure Ti-MOF, reaching 59.6%. After the core-shell structure with TiO2 as the core was formed, the sterilization rate of the TiO2@Ag / Ti-MOF composite material was further improved compared with that of the Ti-MOF@Ag / Ti-MOF composite material, reaching more than 99.99%, because the overall impedance and the recombination rate of photo-generated electrons and holes were reduced, and the light energy could be more efficiently utilized. In summary, the prepared TiO2@Ag / Ti-MOF composite material still had considerable sterilization capacity at a very low sterilization concentration (50 μg / mL), and the photocatalytic production of active free radicals under light conditions was the main reason for the sterilization performance.

[0046] Example 2

[0047] 1) 2-Aminoterephthalic acid with a concentration of 0.3 mmol / mL in N, N-dimethylformamide (DMF) was prepared as solution A;

[0048] 2) Tetrabutyl titanate was dissolved in anhydrous methanol, and the mixture was uniformly mixed to obtain solution B; the volume ratio of tetrabutyl titanate to anhydrous methanol was 1:26;

[0049] 3) Solution A and solution B were mixed according to a molar ratio of tetrabutyl titanate to 2-aminoterephthalic acid of 1:3; after uniform mixing, the mixture was transferred to a microwave oven, the microwave power was set to 600 W, and the heating time was set to 2 hours; after the precipitate was dried, Ti-MOF with Ti vacancies was obtained;

[0050] 4) Ti-MOF with Ti vacancies was dispersed in a 2 mol / L silver ammine solution, and the mass fraction of Ti-MOF with Ti vacancies in the solution was 22%; the mixed solution was transferred to a sealed container, and the solution was filled to more than 2 / 3 of the volume of the container;

[0051] 5) The reaction was carried out at 80 °C for 300 minutes to obtain a Ti / vacancy-MOF@Ag / Ti-MOF structure;

[0052] 6) The Ti-MOF@Ag / Ti-MOF is transferred to a tube furnace and heat treated at 300 °C in an air environment to obtain a TiO2@Ag / Ti-MOF structure.

[0053] The characterization results of this example are the same as those of Example 1, which are core-shell materials with TiO2 as the core and Ag-substituted Ti-MOF as the shell.

[0054] Example 3

[0055] 1) 2-Aminoterephthalic acid with a concentration of 0.2 mmol / mL in N, N-dimethylimidazole (DMF) is prepared as solution A;

[0056] 2) Tetrabutyl titanate is dissolved in anhydrous methanol, mixed uniformly, and solution B is obtained; the volume ratio of tetrabutyl titanate to anhydrous methanol is 1:28;

[0057] 3) Solution A and solution B are mixed according to a molar ratio of tetrabutyl titanate to 2-aminoterephthalic acid of 1:5; after uniform mixing, the mixture is transferred to a microwave oven, the microwave power is set to 600 W, and the heating time is set to 2 hours; after the precipitate is dried, Ti-MOF with Ti vacancies is obtained;

[0058] 4) Ti-MOF with Ti vacancies is dispersed in a 3 mol / L silver-ammonia solution, and the mass fraction of Ti-MOF with Ti vacancies in the solution is 30%; the mixed solution is transferred to a sealed container, and the solution is filled to more than 2 / 3 of the container volume;

[0059] 5) The reaction is carried out at 80 °C for 260 minutes to obtain a Ti / vacancy-MOF@Ag / Ti-MOF structure;

[0060] 6) The Ti-MOF@Ag / Ti-MOF is transferred to a tube furnace and heat treated at 250 °C in an air environment to obtain a TiO2@Ag / Ti-MOF structure.

[0061] The characterization results of this example are the same as those of Example 1, which are core-shell materials with TiO2 as the core and Ag-substituted Ti-MOF as the shell.

[0062] Example 4

[0063] 1) 2-Aminoterephthalic acid with a concentration of 0.3 mmol / mL in N, N-dimethylimidazole (DMF) is prepared as solution A;

[0064] 2) Tetrabutyl titanate is dissolved in anhydrous methanol, mixed uniformly, and solution B is obtained; the volume ratio of tetrabutyl titanate to anhydrous methanol is 1:25;

[0065] 3) According to the molar ratio of tetrabutyl titanate and 2-amino terephthalic acid 1:2.5, mixed solution A and solution B; after uniform mixing, transfer to the microwave oven, set the microwave power to 600W, set the heating time to 2 hours, dry the precipitate to obtain Ti vacancy Ti-MOF;

[0066] 4) Disperse Ti vacancy Ti-MOF in 1.5 mol / L silver amine solution, the mass fraction of Ti vacancy Ti-MOF in the solution is 35%, transfer the mixed solution to a sealed container, and the solution is filled to more than 2 / 3 of the container volume;

[0067] 5) React at 80 ℃ for 300 minutes to obtain Ti / vacancy-MOF@Ag / Ti-MOF structure;

[0068] 6) Transfer Ti-MOF@Ag / Ti-MOF to a tube furnace, and perform heat treatment at 300 ℃ in an air environment to obtain TiO2@Ag / Ti-MOF structure.

[0069] The embodiment has the same characterization results as those of example 1, and is a core-shell material with TiO2 as the core and Ag-substituted Ti-MOF as the shell.

[0070] The above embodiments illustrate the structure, features and effects of the present application, and the above description is only the preferred embodiment of the present application. Any changes or modifications made in accordance with the concept of the present application, or equivalent embodiments with equivalent changes, shall be within the scope of the present application.

Claims

1. A method for preparing TiO2@Ag / Ti-MOF functional material, characterized in that, Comprising the following steps: (1) preparing Ti-MOF with Ti vacancies by microwave hydrothermal method; the Ti-MOF with Ti vacancies is prepared by the following method: 1) preparing 2-amino terephthalic acid with a concentration of 0.2-0.3 mmol / mL in N, N-dimethyl imidazole as solution A; 2) dissolving tetrabutyl titanate in anhydrous methanol to obtain solution B; the volume ratio of tetrabutyl titanate to anhydrous methanol is 1: (22-28); 3) mixing solution A and solution B according to a molar ratio of tetrabutyl titanate to 2-amino terephthalic acid of 1: (0.2-5); after uniform mixing, transferring to a microwave oven, microwave power 600 W, heating time 2 hours, drying the precipitate to obtain Ti-MOF with Ti vacancies; (2) filling the Ti vacancies on the surface layer with silver ions to form Ti vacancies-MOF@Ag / Ti-MOF structure; the Ti vacancies-MOF@Ag / Ti-MOF structure is prepared by dispersing Ti-MOF with Ti vacancies in silver ammonia solution, reacting at 80 ℃ for 240-300 minutes to obtain Ti vacancies-MOF@Ag / Ti-MOF structure; the concentration of silver ammonia solution is 1-3 mol / L; the mass fraction of Ti-MOF with Ti vacancies in the solution is 14-35%; (3) heating Ti-MOF@Ag / Ti-MOF structure to form TiO2@Ag / Ti-MOF structure; the heating method is heat treatment at 200-300 ℃ in a tube furnace in an air environment.

2. The TiO2@Ag / Ti-MOF functional material prepared by the method of claim 1, characterized in that, The material has a core-shell structure, the core is TiO2, and the shell is a silver-substituted Ti-MOF structure.

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