Ti3C2 / Ti-MOF composite photocatalytic material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of photocatalytic materials, in particular to a Ti3C2 / Ti-MOF composite photocatalytic material as well as a preparation method and application thereof. Ti3C2 MXene is used as a metal titanium source, a Ti-N bond and a Ti-O-Ti bond are constructed in situ on an interface of Ti3C2 and an organic ligand through an oxygen-free solvothermal method, a rapid charge transfer channel is constructed, the carrier migration distance is remarkably shortened, and the electron-hole separation efficiency is improved; and meanwhile, the inherent metal conductivity and ultrathin two-dimensional structure of Ti3C2 are utilized to synergistically endow the material with high specific surface area, ordered mesopores and abundant reaction sites. The method is simple and convenient in process and environment-friendly, the prepared two-dimensional Ti-MOF shows excellent catalytic activity under visible light (lambda is larger than or equal to 420 nm), the CO generation rate can reach 469.77 micromol.g <-1 >. H <-1 >, and the CH4 generation rate can reach 271.65 micromol.g <-1 >. H <-1 >.

Description

Technical Field

[0001] This invention relates to the field of photocatalytic materials technology, specifically to a Ti3C2 / Ti-MOF composite photocatalytic material, its preparation method, and its application. Background Technology

[0002] Photocatalysis, as a green approach that utilizes clean solar energy to drive chemical reactions, has shown great potential in energy conversion and environmental remediation. Titanium-based metal-organic frameworks (MOFs), representing the third generation of photocatalytic materials, have attracted considerable attention due to their unique structural characteristics. They cleverly combine the inherent excellent photocatalytic activity of traditional titanium oxides such as titanium dioxide with the highly designable pore structure and surface chemical properties of MOF materials. This results in significant advantages in regulating electronic band structure, improving CO2 reduction efficiency, and optimizing surface and interface properties, powerfully propelling photocatalysis technology towards industrial applications.

[0003] However, existing photocatalytic materials, including titanium-based MOFs, still generally face key bottlenecks such as limited light absorption range (mainly concentrated in the ultraviolet region), high recombination rate of photogenerated carriers, and insufficient catalytic active sites, which severely restrict their practical application efficiency and large-scale development. To overcome these limitations, constructing heterostructures has been proven to be one of the most effective strategies for improving photocatalytic performance. Currently, common methods mainly utilize tetrabutyl titanate or titanium chloride as titanium sources, depositing titanium-based MOFs on the surface of two-dimensional MXene materials via hydrothermal reactions. However, such methods often result in only physical stacking or weak interactions between the titanium-based MOF and the MXene substrate, making it difficult to generate strong and tight chemical bonds in situ at the interface. This lack of interfacial connectivity greatly reduces the effective separation and cross-interfacial transport efficiency of photogenerated electron-hole pairs.

[0004] Therefore, it is urgent to develop new preparation strategies to achieve in-situ construction of strongly interacting interfacial chemical bonds between titanium-based MOFs and MXene, thereby significantly improving the photogenerated carrier separation efficiency of heterojunctions and laying the foundation for the development of high-performance photocatalysts. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a Ti3C2 / Ti-MOF composite photocatalytic material, its preparation method, and its application.

[0006] The first aspect of this invention provides a method for preparing a Ti3C2 / Ti-MOF composite photocatalytic material, comprising: Step 1: After ultrasonically dispersing the Ti3C2MXene material, mix it with H2TCPP under nitrogen protection; wherein the mass ratio of Ti3C2MXene material to H2TCPP is 0.8-1.5:1. Step 2: The mixture is subjected to an oxygen-free solvothermal reaction at a temperature of 120℃-160℃. Step 3: The reaction products are sequentially separated, washed, and dried to obtain Ti3C2 / Ti-MOF composite photocatalytic material.

[0007] This invention provides a Ti3C2 / Ti-MOF composite photocatalytic material, its preparation method, and its applications. The method uses Ti3C2MXene as the titanium source and employs an oxygen-free solvothermal method to construct Ti-N and Ti-O-Ti bonds in situ at the interface with organic ligands, forming a rapid charge transport channel. By precisely controlling key parameters such as the raw material ratio and reaction temperature, this strategy can significantly shorten the carrier migration distance and improve the electron-hole separation efficiency. Simultaneously, the inherent metallic conductivity of Ti3C2 and its ultrathin two-dimensional structure synergistically endow the composite material with a high specific surface area, ordered mesopores, and abundant reactive sites. This preparation process is simple and environmentally friendly, and the resulting two-dimensional Ti3C2 / Ti-MOF composite photocatalytic material exhibits excellent catalytic activity under visible light (λ≥420nm).

[0008] Furthermore, the Ti3C2MXene material was prepared using the following method: S1. Disperse the fluoride in an acidic solution; S2. Add Ti3AlC2 and etch under water bath conditions with stirring. The water bath temperature is 35℃-40℃ and the etching reaction time is 48h-60h. S3. Centrifuge and clean the reaction system until the pH value of the system reaches neutral. S4. Add deionized water and organic solvent to the product obtained in step S3, stir after deoxygenation with inert gas, and then centrifuge and wash. S5. Add the washed substrate to deionized water, introduce nitrogen gas, and then perform ultrasonic treatment for 6-8 hours. S6. After ultrasonic treatment, centrifugation was performed, and the suspension was retained to obtain Ti3C2MXene material.

[0009] In the preparation of Ti3C2MXene materials, it is necessary to strictly control the water bath temperature, etching reaction time, and ultrasonic time. In this embodiment, the ultrasonic time is controlled within a reasonable range, which enables the preparation of 2D ultrathin Ti3C2 nanosheets. This avoids the problem of excessively thick layer stacking that easily occurs in traditional etching, ensuring a large specific surface area and exposed active sites. Unexpectedly, it was found that both excessively short and excessively long ultrasonic times significantly reduce the photocatalytic activity of the subsequent composite material. At the same time, excessively high temperatures can lead to the destruction of the MXene interlayer structure, while excessively low temperatures result in incomplete etching (residual Al).

[0010] Meanwhile, the study found that strict control of etching temperature and etching reaction time can obtain a complete 2D layered structure, providing a stable growth template for MOF, resulting in excellent photocatalytic performance of the composite material.

[0011] Furthermore, during the reaction process, in step S2, the deposits on the inner liner wall are rinsed with hydrochloric acid solution or base liquid every 4 to 6 hours.

[0012] Furthermore, in step 1, the power density of ultrasonic dispersion is 150–500 W / L; the ultrasonic dispersion time is 8–15 min.

[0013] Furthermore, in step 1, the mass ratio of Ti3C2MXene material to H2TCPP is 1-1.2:1.

[0014] Furthermore, in step 2, the reaction temperature is 140℃-150℃, and the reaction time is more than 24 hours.

[0015] Furthermore, in step 2, the reaction time is 24h to 48h.

[0016] Furthermore, in step 3, the washing process involves centrifuging and washing with ethanol and ultrapure water 2-4 times each.

[0017] A second aspect of the present invention provides a Ti3C2 / Ti-MOF composite photocatalytic material prepared by the above-described preparation method.

[0018] The third aspect of the present invention provides the application of the Ti3C2 / Ti-MOF composite photocatalytic material prepared by the above-described preparation method or the above-described Ti3C2 / Ti-MOF composite photocatalytic material in the field of photocatalytic CO2 reduction.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a titanium-based MOF photocatalytic material based on two-dimensional Ti3C2MXene, its preparation method, and its applications. The method uses Ti3C2MXene as the titanium source and employs an oxygen-free solvothermal method to construct Ti-N and Ti-O-Ti bonds in situ at the interface with organic ligands, forming a rapid charge transport channel. By precisely controlling key parameters such as the raw material ratio and reaction temperature, this strategy can significantly shorten the carrier migration distance and improve the electron-hole separation efficiency. Simultaneously, the inherent metallic conductivity of Ti3C2 and its ultrathin two-dimensional structure synergistically endow the composite material with high specific surface area, ordered mesopores, and abundant reactive sites. This preparation process is simple and environmentally friendly. The resulting two-dimensional Ti3C2 / Ti-MOF composite photocatalytic material exhibits excellent catalytic activity under visible light (λ≥420nm), with a CO generation rate reaching 469.77 μmol·g.-1 ·h -1 The CH4 formation rate can reach 271.65 μmol·g -1 ·h -1 This provides an efficient technological pathway for the resource utilization of carbon dioxide and the achievement of carbon neutrality goals. Attached Figure Description

[0020] Figure 1 XRD pattern of the prepared sample.

[0021] Figure 2 The sample uses Ti3C2 as the metal precursor Ti-MOF ( Figure 2 a) Ti3C2 ( Figure 2 SEM image of b) in the image.

[0022] Figure 3 Ti-MOF with Ti3C2 as the metallic precursor ( Figure 3 a), Ti3C2MXene ( Figure 3 TEM image of sample b) in the image.

[0023] Figure 4 TEM-EDS mapping of Ti-MOF.

[0024] Figure 5 XPS spectra of Ti-MOF: total spectrum ( Figure 5 a) O 1s ( Figure 5 b) C 1s ( Figure 5 c) N1s ( Figure 5 d) and Ti 2p Figure 5 (e in the text).

[0025] Figure 6 Fourier transform infrared spectrum of Ti-MOF.

[0026] Figure 7 UV-Vis absorption spectrum of the sample ( Figure 7 a) and band gap width ( Figure 7 (b) in the middle.

[0027] Figure 8 Rates of photocatalytic reduction of carbon dioxide to CH4 and CO using three materials.

[0028] Figure 9 XRD patterns before and after the photocatalytic reaction. Figure 10 The photocurrent of the sample was shown. Figure 10 a) EIS ( Figure 10 b) and Efb ( Figure 10 Comparison of curve c) in the text. Figure 11 The photoluminescence spectrum of the sample. Detailed Implementation

[0029] The present invention will now be described in further detail with reference to specific embodiments. However, this should not be construed as limiting the scope of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0030] Unless otherwise specified, the use of terms such as "upper," "lower," "left," "right," "center," "inner," and "outer" to indicate orientation or positional relationships in the description of specific embodiments of the present invention is based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationship in which the product / equipment / device is typically placed during use. These terms are merely for the purpose of facilitating the description of the present invention or simplifying the description in specific embodiments, enabling those skilled in the art to quickly understand the solution, and do not indicate or imply that a particular device / component / element must have a specific orientation, or be constructed and operated in a specific positional relationship. Therefore, they should not be construed as limitations on the present invention.

[0031] Furthermore, the use of terms such as "horizontal," "vertical," "suspended," and "parallel" does not imply that the corresponding device / component / element must be absolutely horizontal, vertical, suspended, or parallel, but rather that it can be slightly tilted or have a deviation. For example, "horizontal" merely means that its direction is more horizontal relative to "vertical," not that the structure must be completely horizontal, but that it can be slightly tilted. Alternatively, it can be simplified to mean that the corresponding device / component / element, when set in a "horizontal," "vertical," "suspended," or "parallel" direction, can have an error / deviation of ±10% relative to the corresponding direction, more preferably within ±8%, more preferably within ±6%, more preferably within ±5%, and more preferably within ±4%. As long as the corresponding device / component / element is within the error / deviation range, it can still achieve its function in the present invention.

[0032] Furthermore, the use of terms such as "first," "second," and "third" in terminology is merely for distinguishing descriptions of identical or similar components and should not be interpreted as emphasizing or implying the relative importance of a particular component.

[0033] Furthermore, in the description of the embodiments of the present invention, "several", "more than", and "a number of" represent at least two. The number can be any number, such as 2, 3, 4, 5, 6, 7, 8, or 9, and can even exceed nine.

[0034] Furthermore, in the description of the technical solution of this invention, unless otherwise explicitly specified / limited / restricted, the terms "set up," "install," "connect," "link," "provided with," "laid out," and "arranged" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to common connection methods in the art, such as welding, riveting, bolting, and threaded connections. Such connections can be mechanical, electrical, or communication connections; they can be direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components.

[0035] The first aspect of this embodiment provides a method for preparing a Ti3C2 / Ti-MOF composite photocatalytic material, including: Step 1: After ultrasonically dispersing the Ti3C2MXene material, mix it with H2TCPP under nitrogen protection; wherein the mass ratio of Ti3C2MXene material to H2TCPP is 0.8-1.5:1. Step 2: The mixture is subjected to an oxygen-free solvothermal reaction at a temperature of 120℃-160℃. Step 3: The reaction products are sequentially separated, washed, and dried to obtain Ti3C2 / Ti-MOF composite photocatalytic material.

[0036] Using Ti3C2MXene as the titanium source, Ti-N and Ti-O-Ti bonds were constructed in situ at the interface between Ti3C2 and organic ligands via an oxygen-free solvothermal method, thereby constructing a fast charge transport channel, significantly shortening the carrier migration distance and improving the electron-hole separation efficiency. At the same time, the inherent metallic conductivity and ultrathin two-dimensional structure of Ti3C2 were utilized to synergistically endow the material with high specific surface area, ordered mesopores and abundant reaction sites.

[0037] Among them, the mass ratio of Ti3C2MXene to H2TCPP and the reaction temperature are key factors affecting the performance of composite photocatalytic materials. Studies have found that if the mass ratio of the two materials is too large or too small, or the reaction temperature is too high or too low, the catalytic performance will be significantly reduced.

[0038] Meanwhile, an unexpected key point needs to be raised during the preparation of the composite material. In this embodiment, the Ti3C2MXene material is first ultrasonically dispersed, then mixed with the organic ligand (H2TCPP), and finally subjected to a solvothermal reaction. Ultrasonic dispersion of Ti3C2MXene first avoids agglomeration, ensuring its uniform dispersion in the solution and providing a uniform metal source for MOF growth. If the ligand is mixed first and then Ti3C2MXene is dispersed, MXene agglomeration is likely to occur, resulting in uneven MOF growth (low local crystallinity) and ultimately reducing photocatalytic activity (such as decreased CO and CH4 yields).

[0039] In some embodiments, the Ti3C2MXene material is prepared using the following method. S1. Disperse the fluoride in an acidic solution; S2. Add Ti3AlC2 and etch under water bath conditions with stirring. The water bath temperature is 35℃-40℃ and the etching reaction time is 48h-60h. S3. Centrifuge and clean the reaction system until the pH value of the system reaches neutral. S4. Add deionized water and organic solvent to the product obtained in step S3, stir after deoxygenation with inert gas, and then centrifuge and wash. S5. Add the washed substrate to deionized water, introduce nitrogen gas, and then perform ultrasonic treatment for 6-8 hours. S6. After ultrasonic treatment, centrifugation was performed, and the suspension was retained to obtain Ti3C2MXene material.

[0040] In the preparation of Ti3C2MXene materials, it is necessary to strictly control the water bath temperature, etching reaction time, and ultrasonic time. In this embodiment, the ultrasonic time is controlled within a reasonable range, which enables the preparation of 2D ultrathin Ti3C2 nanosheets. This avoids the problem of excessively thick layer stacking that easily occurs in traditional etching, ensuring a large specific surface area and exposed active sites. Unexpectedly, it was found that both excessively short and excessively long ultrasonic times significantly reduce the photocatalytic activity of the subsequent composite material. At the same time, excessively high temperatures can lead to the destruction of the MXene interlayer structure, while excessively low temperatures result in incomplete etching (residual Al).

[0041] Meanwhile, the study found that strict control of etching temperature and etching reaction time can obtain a complete 2D layered structure, providing a stable growth template for MOF, resulting in excellent photocatalytic performance of the composite material.

[0042] In some embodiments, during the reaction process, in step S2, the deposits on the inner liner wall are rinsed with hydrochloric acid solution or a base solution every 4 to 6 hours. This ensures that the Al layer in Ti3AlC2 is uniformly etched, avoids localized residual Al impurities, and improves the purity of MXene.

[0043] In some embodiments, in step 1, the power density of ultrasonic dispersion is 150–500 W / L; the ultrasonic dispersion time is 8–15 min.

[0044] In some embodiments, in step 1, the mass ratio of Ti3C2MXene material to H2TCPP is 1-1.2:1. An excessively high ratio (excessive titanium source) will result in unreacted Ti. 3+Residual substances form impurity phase titanium dioxide, reducing the crystallinity of MOF; if the ratio is too low (excessive ligands), it will lead to insufficient metal sites and reduced active centers. The control range of the raw material ratio is a key factor in the preparation of composite materials to achieve high-performance catalysis in this embodiment.

[0045] In some embodiments, in step 2, the reaction temperature is 140℃-150℃, and the reaction time is 24 hours or more. Too low a temperature will lead to incomplete reaction and low MOF crystallinity (XRD peak broadening); too high a temperature will cause ligand decomposition, forming an amorphous structure. Reasonable control of the reaction temperature can obtain MOFs with high crystallinity and improve photocatalytic activity. Simultaneously, reasonable control of the reaction time can ensure complete MOF growth, good CO2 adsorption capacity, and low MOF particle aggregation. Preferably, in step 2, the reaction time is 24 hours to 48 hours.

[0046] In some embodiments, in step 3, the washing process involves centrifuging with ethanol and ultrapure water 2-4 times each. Centrifuging with ethanol and ultrapure water 2-4 times each can efficiently remove unreacted ligands and impurities.

[0047] The second aspect of this embodiment provides a Ti3C2 / Ti-MOF composite photocatalytic material prepared by the above-described preparation method.

[0048] The third aspect of this embodiment provides the application of the Ti3C2 / Ti-MOF composite photocatalytic material prepared by the above-described preparation method or the above-described Ti3C2 / Ti-MOF composite photocatalytic material in the field of photocatalytic CO2 reduction.

[0049] To more clearly explain the technical solutions of the above embodiments, the following embodiments are provided for further detailed explanation.

[0050] Example 1 Preparation of Ti3C2Mxene 2.0 g of LiF was placed in a polytetrafluoroethylene liner containing 40 ml of 6M hydrochloric acid solution and stirred continuously for 10 min. Then, 1 g of Ti3AlC2 was slowly added (ensuring the addition time exceeded 10 min), and the mixture was stirred in a water bath at 35°C for 48 h. Every 4–5 h, the black substance adhering to the walls was rinsed off with 2M hydrochloric acid solution or the substrate solution, followed by centrifugation at 8000 rpm until the pH reached neutral (first washing three times with 2 mol / L hydrochloric acid, then twice with deionized water). The treated substrate was transferred to an iodine flask, deionized water was added to a volume of approximately 150 ml, and then 10 ml of DMSO was added. The mixture was exposed to nitrogen for 30 min to remove oxygen. After stirring at medium speed at room temperature for 24 h, the mixture was washed twice by centrifugation with ethanol at 8000 rpm, followed by three centrifugation with deionized water. The substrate was then transferred back to the iodine flask, deionized water was added to a volume of approximately 150 ml, and the mixture was again exposed to nitrogen for 30 min. Subsequently, the material was subjected to ultrasonic treatment for 7 hours and then centrifuged continuously at 8000 rpm for 15 minutes. The substrate was retained to obtain Ti3C2MXene material.

[0051] Ti3C2 / Ti-MOF composite photocatalyst material Weigh 0.2 g of H2TCPP and place it in a polytetrafluoroethylene liner. Disperse the prepared Ti3C2MXene by sonication for 10 min, and add 0.2 g of the Ti3C2MXene to the liner (titanium source to organic ligand ratio 1:1). Place the rotor in the liner, purge with nitrogen for 20 min, seal with plastic wrap, and stir for 20 min. After stirring, remove the rotor and place it in a vacuum oven at 140℃ for 24 h. Cool to room temperature, centrifuge the product at 8000 rpm for 10 min, then wash twice with ethanol at 8000 rpm and twice with ultrapure water to obtain a dark purple substrate. Dry the substrate under vacuum at 60℃ for 12 h, and grind to obtain a dark purple crystalline powder.

[0052] Comparative Example 1 Using tetrabutyl titanate as the titanium source and H2TCPP as the organic ligand, 0.3 g of H2TCPP and 2.4 mL of tetrabutyl titanate were placed in a polytetrafluoroethylene liner containing 20 mL of ethanol and 20 mL of distilled water. After nitrogen protection (20 min), the mixture was stirred for 20 min to achieve uniform dispersion. The mixture was then sealed in a reactor and subjected to a solvothermal reaction in a vacuum oven at 140 °C for 24 h. The reaction product was separated by centrifugation (8000 rpm, 10 min), washed twice each with ethanol (8000 rpm, 5 min) and ultrapure water (8000 rpm, 5 min), and the resulting dark brown substrate was vacuum dried at 60 °C for 12 h. After grinding, a titanium-based MOF photocatalyst material was prepared using the tetrabutyl titanate precursor.

[0053] Comparative Example 2 Using titanium tetrachloride (TiCl4) as the titanium source and H2TCPP as the organic ligand, 0.1024 g of H2TCPP and 1.82 mL of TiCl4 were added to a polytetrafluoroethylene liner containing 20 mL of ethanol and 20 mL of distilled water. The mixture was then placed in a rotor and subjected to nitrogen protection (20 min), followed by stirring for 20 min to achieve uniform dispersion. The mixture was then sealed in a reactor and subjected to a solvothermal reaction in a vacuum oven at 140 °C for 24 h. The reaction product was separated by centrifugation (8000 rpm, 10 min), washed twice each with ethanol (8000 rpm, 5 min) and ultrapure water (8000 rpm, 5 min), and the resulting dark green substrate was vacuum dried at 60 °C for 12 h. After grinding, a titanium-based MOF photocatalyst material (dark green crystalline powder) was prepared from the TiCl4 precursor.

[0054] test The photocatalytic materials prepared in Example 1 and Comparative Examples 1-2 were subjected to material characterization tests and photocatalytic performance tests.

[0055] 1. Material characterization testing XRD Analysis: A Rigaku Ultima IV XRD system (Japan) was used with a Cu-Ka laser source (wavelength 0.154 nm), a tube current of 60 mA, and a tube voltage of 60 kV. The crystal phases and morphologies of Ti3C2MXene, MOFs with Ti3C2MXene precursors, MOFs with tetrabutyl titanate precursors, and MOFs with TiCl4 precursors were analyzed. The results showed that the titanium-based MOFs with Ti3C2MXene and tetrabutyl titanate precursors exhibited sharper peaks and better crystallinity. Furthermore, the titanium-based MOF with Ti3C2MXene precursors showed higher strength, fewer impurity peaks, and the strongest characteristic diffraction peaks. The test results are as follows: Figure 1 As shown.

[0056] SEM analysis: The microstructure and morphology of the catalyst were observed using a scanning electron microscope (JEOL JSM-6700F). Figure 2 As shown in -a, Ti-MOF prepared with Ti3C2MXene as a metal precursor retains its lamellar morphology. When the layered structure of MXene is not completely destroyed during MOF growth, thin lamellar MOFs attached to the substrate may be observed in SEM, with MOF nanoparticles interspersed between the layers, and MXene serving as a supporting template. Figure 2-bTi3C2MXene exhibits a typical multilayer crystal structure with obvious layered stacking, resembling the wrinkles of an accordion, indicating the successful synthesis of two-dimensional Ti3C2 nanosheets via etching. The sufficiently thin 2D MXene-based Ti-MOF provides a sufficiently large surface area to offer ample attack sites for protonated ligands, accelerating the reaction while maintaining the underlying 2D topology. This structure significantly enhances its photocatalytic performance.

[0057] TEM and TEM-EDS mapping analysis: such as Figure 3 As shown in -a, the morphology of Ti-MOF with Ti3C2 as the metal precursor is similar to that of Ti3C2MXene. The residual Ti3C2MXene sheets serve as a substrate, with MOF nanoparticles loaded on the surface. MXene encapsulation of Ti-MOF crystals can suppress the photocorrosion of Ti-O clusters, while the inherent antioxidant properties of MXene extend the lifespan of the composite material. Ti3C2MXene Figure 3 -b shows a TEM image of Ti3C2, which exhibits a well-dispersed two-dimensional sheet-like structure without aggregation. Figure 4 Elemental mapping was used to study the distribution of elements, further confirming the successful preparation of Ti-MOF materials. The mapping revealed the presence of C, Ti, N, and O, confirming the presence of these elements in the material. These results further confirm the successful synthesis of the photocatalyst.

[0058] XPS analysis: such as Figure 5 As shown in -a, characteristic peaks of Ti 2p, C 1s, N 1s, and O 1s can be found in 20% MTS, while no characteristic peaks of other elements are observed, indicating that the prepared catalyst contains Ti, C, N, and O elements and no other impurities have been introduced. Figure 5 As shown in -b, three characteristic peaks were observed in the O 1s of the Ti-MOF sample: 530.66 eV, 533.40 eV, and 535.93 eV. These peaks can be attributed to CO bonds, C-OH bonds, and water, indicating that Ti3C2MXene is connected to ligands. The high-resolution spectrum of C1s is shown in... Figure 5 As shown in -c, in Ti3C2, the C 1s spectrum shows four characteristic peaks: 281.44 eV, 284.80 eV, 286.58 eV, and 288.85 eV, which correspond to C-Ti, CC, CO, and CF bonds, respectively. Ti-MOF shows two peaks: 281.83 eV and 284.80 eV, which correspond to C-Ti and CC bonds, respectively. Figure 5-d shows an N1s peak, and Ti-MOF shows peaks of N-Ti bonds at 397.82 eV and NO bonds at 400.17 eV. The appearance of new N-Ti bonds in Ti-MOF significantly enhances electron transfer ability and improves photocatalytic activity. Figure 5 As shown in -e, the Ti 2p spectrum of Ti3C2 exhibits six peaks: 453.47 eV, 453.98 eV, 454.97 eV, 457.33 eV, 459.80 eV, and 460.66 eV, which correspond to Ti-C 2p3 / 2, Ti(Ⅱ) 2p3 / 2, Ti(Ⅲ) 2p3 / 2, Ti-C 2p1 / 2, Ti-O 2p3 / 2, and Ti(Ⅲ) 2p3 / 2, respectively. The Ti 2p spectrum of Ti-MOF exhibits four peaks at 454.8 eV, 458.4 eV, 461.3 eV, and 465.9 eV, corresponding to Ti-N 2p3 / 2, Ti-O 2p1 / 2, Ti-N 2p3 / 2, and Ti-O 2p1 / 2, respectively. The appearance of new Ti-N bonds is attributed to the combination of Ti3C2MXene with the N-coordinate bonds of the ligands, which can be further confirmed using infrared spectroscopy.

[0059] FT-IR analysis: such as Figure 6 As shown. At 3439 cm -1 The broad peak at 2969 cm⁻¹ is attributed to the stretching vibration of the carboxylic acid group (-COOH) or the OH stretching vibration of adsorbed water molecules; -1 The weak peak at 1719 cm⁻¹ may originate from the stretching vibration of the aromatic ring CH. The C=O stretching vibration of the carboxylic acid group is at 1719 cm⁻¹. -1 and 1675 cm -1 The presence of this location indicates the presence of some uncoordinated carboxylic acid groups and carboxylate structures coordinated to the metal. (1604 cm) -1 1549cm -1 and 1497 cm -1 The strong peak at 1549 and 1424 cm⁻¹ corresponds to the C=C stretching vibration of the benzene ring skeleton, while the peaks at 1549 and 1424 cm⁻¹ correspond to the C=C stretching vibration of the benzene ring skeleton. -1 These vibrations are attributed to the asymmetric and symmetric stretching vibrations of the carboxylate group, respectively, confirming that the carboxylate group is partially deprotonated and coordinated with the metal node. (1272 cm⁻¹) -1 and 1182 cm -1 The peak at 1107 cm⁻¹ represents the stretching vibration of CO in carboxylic acids. -1 It may originate from the CN stretching vibration of the porphyrin ring. 964 cm -1 The peak at 870 cm⁻¹ is related to the in-plane deformation vibration of the porphyrin ring. -1 802cm -1 and 764 cm -1The absorption peak at 641 cm⁻¹ corresponds to the out-of-plane bending vibration of the CH group in the para-substituted benzene ring, consistent with the structural characteristics of tetracarboxyphenylporphyrin. Furthermore, a new characteristic peak appears at 641 cm⁻¹. -1 The formation of new N-Ti bonds is attributed to the interaction between the organic ligand and Ti3C2. Low wavenumber region 563 cm⁻¹ -1 and 470 cm -1 The peak at the specified location is attributed to the Ti-O-Ti and Ti-C skeletal vibrations in Ti3C2MXene, indicating the successful recombination of MXene with the porphyrin-based MOF. In summary, the spectroscopic features confirm the coexistence of the carboxylic acid group, aromatic ring, porphyrin ring, and MXene skeleton, and reveal the coordination interaction between the carboxylic acid and the metal.

[0060] UV-Vis / DRS analysis: The UV-Vis diffuse reflectance curves of titanium-based MOF materials prepared based on three precursors—Ti3C2Mxene, tetrabutyl titanate, and TiCl4—are shown below. Figure 7 As shown. From Figure 7 It can be observed that all three materials exhibit significant absorption across the entire wavelength range, with the most pronounced absorption in the 300-750 nm range, indicating that they all possess visible light response and catalytic activity. The titanium-based MOF materials using Ti3C2Mxene and tetrabutyl titanate as precursors show significant similarity in the positions of their absorption peaks (approximately around 656 nm, 600 nm, 564 nm, 525 nm, and 394 nm), and their absorption intensities are all quite significant, suggesting a certain degree of structural similarity. In contrast, the titanium-based MOF material using TiCl4 as a precursor shows absorption peaks at 717 nm, 662 nm, and 500 nm. Compared to the former two, it has fewer absorption peaks, a wider absorption wavelength range, but relatively lower absorption intensity. Compared to traditional Ti-MOF materials derived from Ti, MXene-derived Ti-MOF materials exhibit significantly enhanced absorption intensity in the ultraviolet to visible light region (200-800 nm), and a redshift occurs at the absorption edge. This is because MXene possesses broad-spectrum absorption characteristics from ultraviolet to near-infrared, which are superimposed on the ultraviolet absorption characteristics of Ti-MOF. Furthermore, the terminal groups (—O, —F, —OH) on the MXene surface form charge-transfer complexes (such as TiO2, TiO2, and TiO2) with the Ti-O clusters in the Ti-MOF. 3+ / Ti 4+This introduces an intermediate energy level, narrowing the effective band gap. Furthermore, the terminal groups on the MXene surface affect the position of its Fermi level, thereby altering the bandgap matching with Ti-MOF. For example, -OH terminals can lower the interfacial barrier and improve the response to visible light. By incorporating the Kubelka-Munk function into the calculation of diffuse reflectance spectroscopy, the band gaps of the three titanium-based MOF materials using Ti3C2Mxene, tetrabutyl titanate, and TiCl4 as precursors were found to be approximately 1.8 eV, 1.55 eV, and 1.72 eV, respectively.

[0061] 2. Photocatalytic activity test Using a photocatalytic activity evaluation system (CEL-PAEM-D8), 4 ml of water and 1 ml of lactic acid were placed into the photocatalytic reactor, and 10 mg of the test material was added. The system was then assembled and connected to the reactor. A vacuum was applied for 30 minutes. A 300W xenon lamp was used to simulate sunlight, with stirring at 520 rpm. Cooling water was circulated to maintain the temperature at 6°C, and the current was adjusted to 15 amperes. The reaction system was then introduced into a gas chromatograph (GC-7920), and the gaseous products CO and CH4 were analyzed using a TCD detector. An automatic sampling system was used to take samples every 30 minutes, for a total of 9 samples. Figure 8 Analysis shows that the titanium-based MOF photocatalyst material using Ti3C2Mxene as a precursor achieved a CO production rate of 469.77 μmol·g⁻¹ within 4.5 hours. -1 ·h -1 The CH4 production rate was 271.65 μmol·g. -1 ·h -1 Among these materials, the titanium-based MOF photocatalyst with Ti3C2Mxene as the precursor exhibited the best performance in reducing carbon dioxide to produce CO and CH4, with the highest production rate, demonstrating the best CO2 reduction effect and higher photocatalytic activity. In comparison, the titanium-based MOF with tetrabutyl titanate as the precursor performed second best, while the titanium-based MOF with TiCl4 as the precursor performed the worst. To further investigate the chemical stability of the catalyst, X-ray diffraction patterns were used (…). Figure 9 The Ti-MOF after photocatalytic cycling was characterized. The diffraction pattern showed a slight decrease in the intensity of the diffraction peaks, but the lattice structure did not change significantly, indicating that the catalyst can still maintain its structural stability during photocatalytic cycling.

[0062] 3. Electrochemical testing Photocurrent measurement: A CHI 660e electrochemical workstation was used. The working electrode was prepared by dispersing 5 mg of photocatalyst in an ethanol-nanofiltration (Nafion) mixture (2 mL ethanol + 20 μL 0.25% Nafion). 50 μL of this suspension was then dropped onto a fluorine-doped tin oxide (FTO) substrate (2 × 3.5 cm). After infrared drying, the substrate was heat-treated in a tube furnace at 120 °C for 1 h under a nitrogen atmosphere. An electrochemical system was constructed using the prepared working electrode, a platinum counter electrode, and an Ag / AgCl reference electrode. The electrolyte was a 0.1 M Na₂SO₄ solution. The photocurrent was recorded under intermittent illumination with a 300 W xenon lamp simulating solar irradiation. The results showed that the titanium-based MOF material with Ti₃C₂MXene as the precursor exhibited significantly enhanced photocurrent density and improved photogenerated electron-hole pair separation efficiency.

[0063] Electrochemical impedance spectroscopy (EIS) testing: in the range of 0.01-10 5 Within the Hz frequency range, using an AC perturbation amplitude of 5mV and a mixed aqueous solution of 0.1M Na2S and 0.02M Na2SO3 as the electrolyte, the resistivity and electron transport efficiency of the material were tested. The titanium-based MOF material with Ti3C2Mxene as the precursor exhibited the smallest Nyquist radius, strong conductivity, and good separation of photogenerated holes and photogenerated electrons.

[0064] Mott-Schottky test: At 1000 Hz, the interface charge distribution is determined by measuring the change in space charge layer capacitance (CSC) with potential (V), thus identifying the semiconductor type. All three materials are n-type semiconductors, and their flat-band potentials are all lower than the reduction potentials of carbon dioxide to CO and CH4, indicating that they can all reduce carbon dioxide under visible light irradiation.

[0065] 4. PL test Photoluminescence spectroscopy: 657 nm was selected as the excitation wavelength, and a fluorescence spectrometer (Hitachi F-4600) was used to analyze the three materials. The titanium-based MOF material with Ti3C2MXene as the precursor exhibited the lowest fluorescence intensity, low recombination rates of photogenerated holes and electrons, and the best photocatalytic performance.

[0066] 5. Conclusion This patent successfully prepared a 2D Ti-MOF photocatalytic material using 2D Ti3C2MXene as a metal precursor. Ti3C2MXene was first obtained by chemical etching, then mixed with an organic ligand in a 1:1 ratio. Under nitrogen protection and with thorough stirring, the target material was synthesized via a solvothermal method at 140℃ for 24 hours. Subsequently, various characterization techniques were used to analyze the material's properties, and its photocatalytic performance was optimized through photocatalytic CO2 reduction experiments and electrochemical tests.

[0067] When irradiated with visible light (λ≥420nm), the photocatalytic reduction rate of this material to CO reaches 469.77 μmol. g -1 h -1 The CH4 rate was 271.65 μmol. g -1 h -1 The material exhibits excellent photocatalytic reduction efficiency of carbon dioxide. Characterization results show that the material has good crystallinity, a microstructure conducive to reaction, stable chemical bonds, and excellent light absorption performance. Furthermore, it demonstrates high efficiency in separating photogenerated electron-hole pairs, strong conductivity, and low recombination rate. The 2D Ti-MOF photocatalytic material is highly efficient and stable in the field of photocatalytic carbon dioxide reduction, providing new ideas for the development of photocatalytic materials and showing broad application prospects in environmental protection and energy conversion.

[0068] Ti-MOF@Ti3C2MXene composites prepared using tetrabutyl titanate as the titanium source exhibit weak interfacial bonding and carrier transport resistance. This invention innovatively uses Ti3C2MXene as a metal precursor to directly participate in the synthesis of Ti-MOF photocatalysts via a solvothermal method. This achieves the formation of Ti-N coordination bonds and Ti-O-Ti covalent bonds between Ti-MOF and Ti3C2, significantly improving interfacial electron transport efficiency.

[0069] The preparation of Ti-MOF / Ti3C2 composite materials using titanium tetrachloride (TiCl4) as the titanium source involves a physical mixing-in-situ growth method to load Ti-MOF onto the surface of pre-synthesized Ti3C2. However, this method suffers from weak interfacial bonding and carrier transport resistance. This invention innovatively uses Ti3C2MXene as a metal precursor to directly participate in the synthesis of Ti-MOF via a solvothermal method. This achieves the formation of Ti-N coordination bonds and Ti-O-Ti covalent bonds between Ti-MOF and Ti3C2, significantly improving interfacial electron transport efficiency.

[0070] Example 2 Example 2: Ti3C2MXene material prepared using the method of Example 1; Ti3C2 / Ti-MOF composite photocatalyst material Weigh 0.2 g of H2TCPP and place it in a polytetrafluoroethylene liner. Disperse the prepared Ti3C2MXene by sonication for 10 min, then add it to the liner (the mass ratio of Ti3C2MXene to H2TCPP is 0.8:1). Place the rotor in the liner, purge with nitrogen for 20 min, seal with plastic wrap, and stir for 20 min. After stirring, remove the rotor and place it in a vacuum oven at 120℃ for 36 h. Cool to room temperature, centrifuge the product at 8000 rpm for 10 min, then wash three times with ethanol at 8000 rpm and three times with ultrapure water to obtain a dark purple substrate. Dry the substrate under vacuum at 60℃ for 12 h, then grind to obtain a dark purple crystalline powder.

[0071] The composite photocatalytic material prepared in Example 2 was tested using the exact same testing procedure as in Example 1. The results showed that the CO generation rate of the composite photocatalytic material prepared in Example 2 reached 461.31 μmol·g⁻¹. -1 ·h -1 The CH4 formation rate can reach 229.66 μmol·g -1 ·h -1 .

[0072] Example 3 Example 3: Ti3C2MXene material prepared using the method of Example 1; Ti3C2 / Ti-MOF composite photocatalyst material Weigh 0.2 g of H2TCPP and place it in a polytetrafluoroethylene liner. Disperse the prepared Ti3C2MXene evenly by sonication for 10 min, then add it to the liner (the mass ratio of Ti3C2MXene to H2TCPP is 1.5:1). Place the rotor in the liner, purge with nitrogen for 20 min, seal with plastic wrap, and stir for 20 min. After stirring, remove the rotor and place it in a vacuum oven at 160℃ for 30 h. Cool to room temperature, centrifuge the product at 8000 rpm for 10 min, then wash four times with ethanol at 8000 rpm and four times with ultrapure water to obtain a dark purple substrate. Dry the substrate under vacuum at 60℃ for 12 h, and grind it to obtain a dark purple crystalline powder.

[0073] The composite photocatalytic material prepared in Example 3 was tested using the exact same testing procedure as in Example 1. The results showed that the CO generation rate of the composite photocatalytic material prepared in Example 3 reached 454.96 μmol·g⁻¹. -1 ·h -1 The CH4 formation rate can reach 230.43 μmol·g -1 ·h -1 .

[0074] Comparative Example 3 Comparative Example 3 uses the same raw materials and preparation process as Example 1 to prepare composite photocatalytic materials. The difference is that the mass ratio of Ti3C2MXene material to H2TCPP in Comparative Example 3 is controlled at 0.5:1, but the total mass of the two is the same as that in Example 1.

[0075] The composite photocatalytic material prepared in Comparative Example 3 was tested using the exact same testing procedure as in Example 1. The results showed that the CO generation rate of the composite photocatalytic material prepared in Comparative Example 3 reached 361.04 μmol·g⁻¹. -1 ·h -1 The CH4 formation rate can reach 227.53 μmol·g -1 ·h -1 .

[0076] Comparative Example 4 Comparative Example 4 uses the same raw materials and preparation process as Example 1 to prepare composite photocatalytic materials. The difference is that the mass ratio of Ti3C2MXene material to H2TCPP in Comparative Example 4 is controlled at 2:1, but the total mass of the two is the same as that in Example 1.

[0077] The composite photocatalytic material prepared in Comparative Example 4 was tested using the exact same testing procedure as in Example 1. The results showed that the CO generation rate of the composite photocatalytic material prepared in Comparative Example 4 reached 353.14 μmol·g⁻¹. -1 ·h -1 The CH4 formation rate can reach 228.70 μmol·g -1 ·h -1 .

[0078] Comparative Example 5 Comparative Example 5 uses the same raw materials and preparation process as Example 1 to prepare composite photocatalytic materials. The difference is that the oxygen-free solvothermal reaction temperature in Comparative Example 5 is controlled at 100°C, while the rest of the preparation method is consistent with that in Example 1.

[0079] The composite photocatalytic material prepared in Comparative Example 5 was tested using the exact same testing procedure as in Example 1. The results showed that the CO generation rate of the composite photocatalytic material prepared in Comparative Example 5 reached 355.75 μmol·g⁻¹. -1 ·h -1 The CH4 formation rate can reach 227.71 μmol·g -1 ·h -1 .

[0080] Comparative Example 6 Comparative Example 6 uses the same raw materials and preparation process as Example 1 to prepare composite photocatalytic materials. The difference is that the oxygen-free solvothermal reaction temperature of Comparative Example 6 is controlled at 200°C, while the rest of the preparation method is consistent with that of Example 1.

[0081] The composite photocatalytic material prepared in Comparative Example 6 was tested using the exact same testing procedure as in Example 1. The results showed that the CO generation rate of the composite photocatalytic material prepared in Comparative Example 6 reached 345.44 μmol·g⁻¹. -1 ·h -1 The CH4 formation rate can reach 228.01 μmol·g -1 ·h -1 .

[0082] Comparative Example 7 Comparative Example 7 uses the same raw materials as Example 1 to prepare composite photocatalytic materials. The difference is that the Ti3C2MXene material in Comparative Example 7 is not ultrasonically dispersed, but directly mixed and stirred with H2TCPP under nitrogen protection. The rest of the process and parameters are the same as those in Example 1.

[0083] The composite photocatalytic material prepared in Comparative Example 7 was tested using the exact same testing procedure as in Example 1. The results showed that the CO generation rate of the composite photocatalytic material prepared in Comparative Example 7 reached 346.17 μmol·g⁻¹. -1 ·h -1 The CH4 formation rate can reach 226.49 μmol·g -1 ·h -1 .

[0084] Comparative Example 8 Comparative Example 8 uses the same raw materials as Example 1 to prepare composite photocatalytic materials. The difference is that in Comparative Example 8, Ti3C2MXene material is first directly mixed and stirred with H2TCPP under nitrogen protection, and then ultrasonic dispersion is performed. The remaining process and parameters are the same as in Example 1.

[0085] The composite photocatalytic material prepared in Comparative Example 8 was tested using the exact same testing procedure as in Example 1. The results showed that the CO generation rate of the composite photocatalytic material prepared in Comparative Example 8 reached 346.18 μmol·g⁻¹. -1 ·h -1 The CH4 formation rate can reach 225.80 μmol·g -1 ·h -1 .

[0086] Comparative Example 9 Comparative Example 9 prepared composite photocatalytic materials using the same process.

[0087] The difference lies in the preparation process of Ti3C2MXene material. Compared with the preparation process of Ti3C2MXene material in Example 1, Comparative Example 9 changed the ultrasonic time, replacing the 7h ultrasonic time in Example 1 with a 5h ultrasonic time. The rest of the preparation process is the same as in Example 1.

[0088] The composite photocatalytic material prepared in Comparative Example 9 was tested using the exact same testing procedure as in Example 1. The results showed that the CO generation rate of the composite photocatalytic material prepared in Comparative Example 9 reached 369.15 μmol·g⁻¹. -1 ·h -1 The CH4 formation rate can reach 227.74 μmol·g -1 ·h -1 .

[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a Ti 3C 2 / Ti-MOF composite photocatalytic material, characterized in that, include: Step 1: The Ti3C2 MXene material, which serves as the titanium source, is ultrasonically dispersed and then mixed with H2TCPP under nitrogen protection; wherein the mass ratio of Ti3C2 MXene material to H2TCPP is 0.8-1.5:

1. Step 2: Place the mixture in a sealed reactor and carry out an oxygen-free solvothermal reaction at a temperature of 120℃-160℃. Step 3: The reaction products are sequentially separated, washed, and dried to obtain Ti3C2 / Ti-MOF composite photocatalytic material.

2. The production method according to claim 1, characterized by, Ti3C2 MXene material was prepared using the following method. S1. Disperse the fluoride in an acidic solution; S2. Add Ti3AlC2 and etch under water bath conditions with stirring. The water bath temperature is 35℃-40℃ and the etching reaction time is 48h-60h. S3. Centrifuge and clean the reaction system until the pH value of the system reaches neutral. S4. Add deionized water and organic solvent to the product obtained in step S3, stir after deoxygenation with inert gas, and then centrifuge and wash. S5. Add the washed substrate to deionized water, introduce nitrogen gas, and then sonicate for 6-8 hours. S6. After sonication, centrifuge and retain the suspension to obtain Ti3C2 MXene material.

3. The method of claim 2, wherein, During the reaction process, in step S2, the deposits on the inner lining wall are rinsed with hydrochloric acid solution or the acidic solution containing fluoride prepared in step S1 every 4 to 6 hours.

4. The preparation method according to claim 1, characterized in that, In step 1, the power density of ultrasonic dispersion is 150–500 W / L; the ultrasonic dispersion time is 8–15 min.

5. The preparation method according to claim 1, characterized in that, In step 1, the mass ratio of Ti3C2 MXene material to H2TCPP is 1-1.2:

1.

6. The preparation method according to claim 1, characterized in that, In step 2, the reaction temperature is 140℃-150℃ and the reaction time is more than 24 hours.

7. The preparation method according to claim 6, characterized in that, In step 2, the reaction time is 24h to 48h.

8. The preparation method according to claim 1, characterized in that, In step 3, the washing process involves centrifuging and washing with ethanol and ultrapure water 2-4 times each.

9. The Ti3C2 / Ti-MOF composite photocatalytic material prepared by the preparation method according to any one of claims 1-8.

10. The application of the Ti3C2 / Ti-MOF composite photocatalytic material prepared by the preparation method according to any one of claims 1-8 or the Ti3C2 / Ti-MOF composite photocatalytic material according to claim 9 in the field of photocatalytic CO2 reduction.

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