NH2-UiO-66 / TiO2 nanocomposites, their preparation methods, and applications

Abstract

This invention belongs to the field of photocatalysis technology, specifically relating to NH2-UiO-66 / TiO2 nanocomposite materials, their preparation methods, and applications. The preparation method is as follows: Sulfated oxypeptide is dissolved in an alcohol solvent to obtain solution A. Glycerol and diethyl ether are added to solution A and stirred until homogeneous to obtain solution B. Solution B is transferred to a stainless steel pressure vessel and subjected to a hydrothermal reaction at 110–140°C. After filtration, washing, and drying, it is calcined at 550–650°C to obtain TiO2 nanotubes. TiO2 nanotubes, zirconium chloride, DMF, and concentrated hydrochloric acid are mixed homogeneously to obtain mixture C. A DMF solution of 2-aminobenzoic acid is added to mixture C and mixed homogeneously to obtain reaction solution D. The reaction solution is then heated to 60–90°C, centrifuged, and dried to obtain popcorn stick-shaped NH2-UiO-66 / TiO2. The nanocomposite material exhibits excellent activity in the photocatalytic oxidation of soot particles by NO2, with NO2 and soot particles mainly converted to N2 and CO2, respectively.

Description

Technical Field

[0001] This invention belongs to the field of photocatalysis technology, specifically relating to NH2-UiO-66 / TiO2 nanocomposite materials, their preparation methods, and applications. Background Technology

[0002] The photocatalytic activity of TiO2-based materials has been enhanced through various methods, such as altering morphology and structural composition, elemental doping, and junction fabrication. In morphology control studies, low-dimensional TiO2-based photocatalysts (including nanospheres, nanorods, nanosheets, and mesoporous structures) are advantageous for increasing surface area and reducing charge migration distance, thereby improving photocatalytic activity. However, this reduction in morphological dimension does not guarantee sufficient charge separation and transfer. Furthermore, doping TiO2 with different elements has improved the photocatalytic degradation performance of pollutants, although the doping process introduces structural impurities, reducing the stability of the photocatalyst.

[0003] Constructing heterojunctions between TiO2 and other materials is an effective way to promote charge separation and transfer, thereby improving photocatalytic performance. Various heterojunctions of TiO2 with inorganic semiconductors (including CoTiO3, Bi2O3, and LaFeO3) have been successfully constructed, improving photocatalytic pollutant removal efficiency. However, these materials still suffer from low surface area and limited charge separation capabilities. The combination of TiO2 and metal-organic frameworks (MOFs) may have potential advantages due to the synergistic effect between the two composite materials. Anatase TiO2 is active in the photocatalytic carbon oxidation of NO; ​​however, its performance is partially limited by its large band gap energy. NH2-UiO-66 exhibits excellent photocatalytic NO2 oxidation performance due to its NOx adsorption capacity and the generation of ligand-metal charge migration pathways. NH2-UiO-66 is a promising candidate material for forming junctions with TiO2 due to its stability, high surface area, and visible light absorption. Studies have found that nanocomposites of TiO2 nanofibers or nanosheets and NH2-UiO-66 particles are effective in photocatalytic CO2 conversion due to their high porosity and enhanced charge transfer at the heterojunction interface. Furthermore, the composite material formed by TiO2 particles on the surface of NH2-UiO-66 crystals, due to the uniform dispersion of TiO2, improves the photocatalytic removal efficiency of toluene and acetaldehyde and promotes photoinduced charge separation and transfer. While TiO2 possesses some ability to simultaneously remove soot particles and nitrogen oxides through photocatalysis, its catalytic effect remains unsatisfactory. Whether it is possible to synthesize NH2-UiO-66 with TiO2 to prepare photocatalytic materials with significantly improved photocatalytic activity for soot particles and nitrogen oxides, based on the excellent photocatalytic NO2 oxidation performance of NH2-UiO-66, remains a pressing issue to be addressed in this field. Summary of the Invention

[0004] This application describes the in-situ growth method for preparing heterojunctions containing NH2-UiO-66 particles loaded onto nanotubes assembled from TiO2 nanoplates. These heterojunctions possess suitable band structures for photocatalytic elimination of carbon particles and nitrogen dioxide. Under UV-Vis irradiation, compared to pristine TiO2, the obtained NH2-UiO-66 / TiO2 nanocomposite exhibits superior NO2 photocatalytic carbon oxidation (0.063 μmol·h⁻¹). -1 ·g -1 (99% N2 selectivity). Effective charge separation and migration were verified through various characterization techniques. This application utilizes the NH2-UiO-66 / TiO2 nanocomposite material for the photocatalytic removal of NO. x The conversion rate has been significantly improved.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A nanocomposite material of NH2-UiO-66 / TiO2, wherein the morphology of the material is as follows: NH2-UiO-66 agglomerated nanoparticles crystallize on the surface of TiO2 hollow nanotube nanoplates to form popcorn stick-shaped NH2-UiO-66 / TiO2 nanocomposite material.

[0007] Preferably, the diameter of the NH2-UiO-66 aggregated nanoparticles is 10-50 nm, the diameter of the TiO2 hollow nanotubes is 0.5-2.0 nm, the length is 4-7 nm, and the thickness of the nanoplate is 40-70 nm.

[0008] More preferably, the mass ratio of the NH2-UiO-66 nanoparticles to the TiO2 hollow nanotubes is 1:(2-9).

[0009] More preferably, the mass ratio of the NH2-UiO-66 nanoparticles to the TiO2 hollow nanotubes is 1:9, 1:4, or 1:2.3.

[0010] The preparation method of the above-mentioned NH2-UiO-66 / TiO2 nanocomposite material includes the following steps:

[0011] (1) Preparation of TiO2 nanotubes by hydrothermal method: Sulfated oxypeptide was dissolved in an alcohol solvent to obtain solution A. Glycerol and diethyl ether were added to solution A under vigorous stirring. The solution was allowed to stand at room temperature for 0.3-1 h to obtain solution B. Solution B was transferred to a stainless steel pressure vessel and subjected to hydrothermal reaction at 110-140℃. After the reaction was completed, the solution was filtered, washed, dried and calcined at 550-650℃ to obtain TiO2 nanotubes.

[0012] (2) The TiO2 nanotubes, zirconium chloride, DMF and concentrated hydrochloric acid described in step (1) are mixed evenly to obtain a mixed solution C. A DMF solution of 2-aminobenzoic acid is added to the mixed solution C and mixed evenly to obtain a reaction solution D. Then, the reaction is heated at 60-90℃ and centrifuged and dried to obtain the NH2-UiO-66 / TiO2.

[0013] Preferably, in step (1), the volume ratio of alcohol solvent, glycerol, and diethyl ether is 2:1:1; the alcohol solvent is selected from any one of methanol, ethanol, and isopropanol; the mass-volume ratio of sulfated oxypeptide to glycerol and diethyl ether is 1 / 9 g / mL.

[0014] The purpose of vigorous stirring in step (1) is to ensure thorough mixing.

[0015] Preferably, the hydrothermal reaction time in step (1) is 8-12 hours.

[0016] Preferably, the washing and drying steps in step (1) are: washing with deionized water and ethanol 5 times, and then drying at 60°C for 3 hours; and calcining for 3-6 hours in step (1).

[0017] Preferably, the concentrated hydrochloric acid in step (2) has a mass fraction of 37%, and the volume ratio of DMF to concentrated hydrochloric acid in reaction solution D is 15:1. The 37% concentrated hydrochloric acid serves to neutralize the alkaline components in the reaction solution and promote the formation of UiO-66.

[0018] Preferably, the ratio of TiO2 nanotubes, zirconium chloride and 2-aminobenzoic acid in step (2) is (0.17-0.5)g:0.54mmol:0.75mmol.

[0019] In this invention, ultrasonic mixing is preferred to obtain a uniformly mixed dispersion system or mixture.

[0020] Preferably, the heating reaction time in step (2) is 10 to 14 hours; the centrifugal drying step in step (2) is: centrifuged 3 times with methanol, and then dried at 60°C for 12 hours.

[0021] The above-mentioned application of NH2-UiO-66 / TiO2 in the photocatalytic reaction of NO2 and carbon particles shows that the photocatalytic reaction of NO2 and carbon can be carried out at room temperature and under full-spectrum irradiation. The NO2 conversion rate is 100%, and the catalytic products include CO2 and N2, with an N2 selectivity of more than 97%.

[0022] Preferably, when the mass fraction of NH2-UiO-66 in the NH2-UiO-66 / TiO2 composite material is 20%, the CO2 yield per unit mass of photocatalyst is 0.063 molg in an environment with soot particles and NO2 concentration of 500 ppm.-1 h -1 .

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] This invention successfully prepared popcorn stick-shaped NH2-UiO-66 / TiO2 nanocomposites using a simple solvothermal strategy. SEM and TEM characterization revealed that NH2-UiO-66 nanoparticles were uniformly dispersed on the surface of TiO2 nanoplatelets. Compared to pure TiO2, the prepared 2-NU / TiO2 nanocomposite exhibited superior activity in the photocatalytic oxidation of soot particles by NO2. NO2 and soot particles were mainly converted to N2 and CO2, respectively. The significantly enhanced performance was attributed to accelerated charge separation and transfer at the NU / TiO2 interface, visible light absorption, and NO2 reduction by the NH2-UiO-66 material. x The combined effect of adsorption capacities is evident. Multiple photoelectrochemical characterization techniques, including surface photovoltage spectroscopy, photoluminescence, transient photocurrent measurement, and electrochemical impedance spectroscopy, confirmed that the formation of the heterojunction enhances the charge separation and transfer efficiency of the composite material. This work provides a novel strategy for improving the photocatalytic removal of pollutants from TiO2 by using MOF materials as visible light sensitizers, charge separators, and pollutant adsorbents. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the preparation process of the NH2-UiO-66 / TiO2 nanocomposite material of the present invention.

[0026] Figure 2 The images show the structure and morphology of 2-NU / TiO2 in this embodiment of the invention, TiO2 in Comparative Example 1, and NH2-UiO-66 in Comparative Example 2, wherein: (a) is the XRD result of NH2-UiO-66 / TiO2 with different TiO2 doping amounts; (b) is the SEM image of NH2-UiO-66; (c) and (d) are both SEM images of TiO2 nanotubes; (e) and (f) are both SEM images of NH2-UiO-66 / TiO2; and (g) and (h) are both TEM images of NH2-UiO-66 / TiO2.

[0027] Figure 3 SEM images and EDS spectra of 2-NU / TiO2 in this embodiment of the invention: (a) SEM image; X-ray energy spectrum: O (b), Ti (c), Zr (d).

[0028] Figure 4The following are the photoelectric performance test diagrams of 2-NU / TiO2 of the present invention and TiO2 of Comparative Example 1, wherein: (a) ultraviolet diffuse reflectance, (b) optical bandgap diagram, (c) surface photovoltage spectrum, and (d) photoluminescence spectrum.

[0029] Figure 5 The valence band spectrum of NH2-UiO-66 of the present invention is shown in (a), and the valence band spectrum of NH2-UiO-66 and TiO2 is shown in (b).

[0030] Figure 6 The amount of CO2 generated during the reaction of photocatalytic carbon soot particles with 500 ppm NO2 using different catalytic materials of this invention. Detailed Implementation

[0031] The present invention will be further described below with reference to specific embodiments, and the advantages and features of the present invention will become clearer with the description. However, the embodiments are merely exemplary and do not constitute any limitation on the scope of the present invention. Those skilled in the art should understand that modifications or substitutions can be made to the details and form of the technical solutions of the present invention without departing from the spirit and scope of the present invention, but all such modifications and substitutions fall within the protection scope of the present invention.

[0032] Example

[0033] A method for preparing an NH2-UiO-66 / TiO2 nanocomposite material includes the following steps:

[0034] (1) Synthesis of TiO2: Nanoplate-assembled nanotubes were prepared via hydrothermal synthesis. Typically, 1 g of titanium oxysulfate was dissolved in 18 mL of ethanol under magnetic stirring and maintained for 30 min. Subsequently, 9 mL of glycerol and 9 mL of diethyl ether were added to the above solution under vigorous magnetic stirring, and the reaction was carried out at room temperature for half an hour. The white suspension was transferred to a 50 mL Teflon-lined stainless steel autoclave and maintained at 120 °C for 10 h. After the hydrothermal reaction, the white precipitate was filtered, washed five times with deionized water and ethanol, and then dried at 60 °C for 3 h. Finally, assembled TiO2 nanotubes were obtained by calcining the white powder at 600 °C for 4 h.

[0035] (2) Synthesis of popcorn stick-shaped NH2-UiO-66 / TiO2: NH2-UiO-66 was synthesized on TiO2 nanotubes using an in-situ growth strategy. 0.25 g of the synthesized TiO2 nanotubes, 0.54 mmol of zirconium chloride, 5 mL of DMF, and 1 mL of hydrochloric acid were mixed together in a round-bottom flask and sonicated for 20 min. Subsequently, 0.75 mmol of 2-aminobenzoic acid and 10 mL of DMF were added to the suspension, and the mixture was sonicated for 30 min, followed by heating at 80 °C for 12 h. After synthesis, the product was obtained and centrifuged three times with methanol, then dried at 60 °C for 12 h to obtain the NH2-UiO-66 / TiO2 nanocomposite material (where the mass fraction of NH2-UiO-66 was 20%).

[0036] The obtained NH2-UiO-66 / TiO2 nanocomposite material is as follows: Figure 2 As shown in (e), NH2-UiO-66 aggregated nanoparticles crystallize on the surface of a TiO2 hollow nanotube nanoplatelet, forming a popcorn stick shape; the diameter of the NH2-UiO-66 aggregated nanoparticles is 10-50 nm, the diameter of the TiO2 hollow nanotubes is 0.5-2.0 nm, the length is 4-7 nm, and the thickness of the nanoplatelet is 40-70 nm; the mass ratio of the NH2-UiO-66 nanoparticles to the TiO2 hollow nanotubes is 1:5.

[0037] Following the above method, hybrid photocatalysts with different proportions of TiO2 were prepared by changing the mass of TiO2 added: 10% NH2-UiO-66 / TiO2 (1-NU / TiO2) (0.5 g TiO2 nanotubes), 20% NH2-UiO-66 / TiO2 (2-NU / TiO2) (0.25 g TiO2 nanotubes), and 30% NH2-UiO-66 / TiO2 (3-NU / TiO2) (0.17 g TiO2 nanotubes).

[0038] Comparative Example 1

[0039] A method for synthesizing TiO2: Nanoplate-assembled nanotubes are prepared via hydrothermal synthesis. Typically, 1 g of titanium oxysulfate is dissolved in 18 mL of ethanol under magnetic stirring and maintained for 30 min. Subsequently, 9 mL of glycerol and 9 mL of diethyl ether are added to the above solution under vigorous magnetic stirring and stored at room temperature overnight. The white suspension is transferred to a 50 mL Teflon-lined stainless steel autoclave and maintained at 170 °C for 10 h. After the hydrothermal reaction, the white precipitate is filtered, washed five times with deionized water and ethanol, and then dried at 60 °C for 3 h. Finally, assembled TiO2 nanotubes are obtained by calcining the white powder at 600 °C for 4 h.

[0040] Comparative Example 2

[0041] A method for synthesizing NH2-UiO-66: 0.54 mmol zirconium chloride, 5 mL DMF, and 1 mL hydrochloric acid were added to a 100 mL round-bottom flask and sonicated for 20 minutes to obtain a clear solution. Then, 0.75 mmol 2-aminoterephthalic acid and 10 mL DMF were added, followed by sonication for 20 minutes and heating at 80 °C overnight. After cooling to room temperature, the solid product was recovered, washed three times with methanol by centrifugation, and dried at 60 °C for 12 hours. Finally, the sample was collected.

[0042] The materials obtained in the examples and comparative examples are characterized and analyzed below.

[0043] NH2-UiO-66 / TiO2 structural characterization

[0044] The formation of MOF and TiO2 crystalline phases in the 2-NU / TiO2 nanocomposite material was confirmed by X-ray diffraction (XRD), such as... Figure 2 As shown in (a), the anatase phase is considered the only phase in the TiO2 sample and is present in all prepared nanocomposites. NH2-UiO-66 exhibits characteristic peaks of MOF materials, as shown by XRD measurements, indicating that the presence of TiO2 in the composite does not alter the crystal structure of the MOF material. Similarly, the TiO2 crystal structure remains intact during the solvothermal synthesis of NH2-UiO-66. The nanocomposites clearly show the merging of the NH2-UiO-66 and anatase XRD patterns, and the intensity of the NH2-UiO-66 characteristic peak is consistent with its concentration, indicating the successful construction of NU-TiO2 nanocomposites without any structural alteration.

[0045] SEM and TEM can be used to study crystal structure and morphology, and have also confirmed the formation of NU-TiO2 nanocomposites. For example... Figure 2 As shown in (b), NH2-UiO-66 generated aggregated nanoparticles with a diameter of approximately 20 nm. Figure 2 (cd) Anatase TiO2 exhibits a hollow microtubule morphology composed of nanoplatelets approximately 500 nm thick, providing a large surface area and abundant surface active sites. For example... Figure 2 (ef) In the presence of synthesized TiO2, NH2-UiO-66 nanoparticles crystallize directly on the surface of TiO2 nanoplates to form popcorn stick-shaped NU / TiO2 composite materials. Figure 2 (gh) Transmission electron microscopy reveals that the NU / TiO2 nanocomposite material retains its hollow nanotube structure, with the lighter-colored edges consisting of NH2-UiO-66 nanoparticles. This also indicates the successful construction of the NU-TiO2 nanocomposite material.

[0046] NH2-UiO-66 particles are uniformly distributed on TiO2 nanoplatelets. For example... Figure 3 (bd) EDS spectra also validated this finding, showing a uniform distribution of O, Ti, and Zr atoms throughout the NU / TiO2 nanocomposite. The size of the MOF particles on the TiO2 surface was similar to that produced in the absence of anatase TiO2, indicating that the MOF growth process was unaffected by the presence of TiO2. Furthermore, the formation of NH2-UiO-66 particles did not alter the structure and morphology of the anatase TiO2. Figure 2 (e) Notably, no isolated MOF particles were found in the 2-NU / TiO2 nanocomposite compared to pure NH2-UiO-66. Transmission electron microscopy (TEM) measurements confirmed that the NU / TiO2 nanocomposite retained a hollow structure, such as... Figure 2 (g, h). In short, SEM and TEM measurements support the conclusion that popcorn stick-shaped NU / TiO2 nanocomposites were successfully prepared through the strong interaction between NH2-UiO-66 and TiO2.

[0047] Study on photoelectrochemical performance of NH2-UiO-66 / TiO2

[0048] The light absorption characteristics of 2-NU / TiO2 were studied by UV-vis diffuse reflectance spectroscopy. Figure 4 (a) Compared with the original TiO2, the 2-NU / TiO2 nanocomposite exhibits a wider visible light absorption. Figure 4 (b) The Tauc plots shown are derived from the UV-vis diffuse reflectance spectrum using the Kubelka Munk function, with anatase as the indirect semiconductor. The derived band gaps of TiO2 for the pristine TiO2 and the 2-NU / TiO2 nanocomposite are 3.2 eV, 2.83 eV, and 3.2 eV, respectively, which are similar to the values ​​in the literature. As expected, the 2-NU / TiO2 nanocomposite exhibits extended absorption in the visible light range similar to that of pristine TiO2, which is beneficial to photocatalysis due to the improved solar energy utilization. Surface photovoltage spectroscopy (SPV) data of the synthesized materials are shown below. Figure 4 As shown in (c), SPV measurements of 2-NU / TiO2 revealed a significant increase in surface voltage compared to pristine TiO2, indicating higher charge transfer efficiency on the NU / TiO2 surface. The improved charge separation and transfer in NU / TiO2 were also examined by photoluminescence (PL) emission measurements. Figure 4(d) Compared with pure TiO2, the 2-NU / TiO2 spectrum exhibits significant photoluminescence quenching at an excitation wavelength of 358 nm. This result indicates that the inherently rapid recombination of photoinduced electron-hole pairs is effectively suppressed due to the formation of heterojunction interfaces in the 2-NU / TiO2 nanocomposite, which in turn enhances the photocatalytic activity of the material.

[0049] In addition, such as Figure 5 (a) The band gap of NH2-UiO-66 was determined to be 2.75 eV. Figure 5 (b) It can be seen that the valence band edges of the synthesized NH2-UiO-66 and TiO2, as determined by XPS, are 2.57 eV and 3.16 eV, respectively. Based on this and the band gap derived from UV-Vis spectroscopy, the conduction band positions of the two materials can be calculated. The conduction band position of TiO2 is -0.04 eV, and that of NH2-UiO-66 is -0.18 eV.

[0050] Study on the photocatalytic mechanism of NH2-UiO-66 / TiO2

[0051] The photocatalytic performance was tested using the following experimental steps:

[0052] (1) Photocatalytic nitrogen dioxide conversion performance test:

[0053] First, 25 mg of sample and 5 mg of soot particles were dispersed in 4 ml of isopropanol. Then, the suspension was drop-coated onto an 8 cm diameter quartz glass substrate. After air-drying, it was dried overnight in an oven at 60°C. The quartz glass was then placed in an O-ring-sealed photoreactor and illuminated with a 500 W xenon lamp (CEAuLight) at 254.7 mW / cm². 2 NO2 (2% of He) was fed into the reactor from a gas cylinder via a mass flow controller (Sevenstar) under top illumination at high light intensity without a cutoff filter. After the reaction, water was removed from the gas stream using a gas cooler with a dew point of 3°C for analyzer protection. Products were detected by UV detectors (CubicRuyi Gasboard 3000UV) for NO and NO2 and NDIR detectors (CubicRuyi Gasboard 3000PLUS) for CO and CO2. CO2 was removed from the gas stream via a soda-lime filter before monitoring N2O using a Geotech G200 analyzer to avoid its influence on N2O detection. N2 selectivity after the photocatalytic reaction was calculated based on nitrogen atom balance.

[0054] (2) Photoelectrochemical performance testing:

[0055] TiO2 and NH2-UiO-66 / TiO2 were used as photoanodes. The photoanodes were prepared as follows: 4 mg of TiO2 and NH2-UiO-66 / TiO2 were dispersed separately in 4 mL of ethanol solution, and then dispersed onto FTO glass (1 cm² area) using a pipette. 2 Then air dry naturally.

[0056] The photocatalytic activity of the synthesized photocatalyst was evaluated by performing photocatalytic carbon oxidation with NO2 in batch mode at room temperature and under full-spectrum irradiation. In a typical procedure, a quartz liner containing carbon and a photocatalyst layer was placed in the photoreactor. The reactor was sealed using two O-rings and a quartz glass plate. After purging the photoreactor with pure N2 (99.999%), NO2 contained in a carrier gas (N2) at 150 mL / min was introduced into the photoreactor without illumination. Subsequently, a batch mode reaction was carried out by closing the gas inlet and outlet and then irradiating. The gaseous products of the reaction were recorded using a gas analyzer after determination. Figure 6 Table 1 shows the COx formation during photocatalytic carbon oxidation with NO2 in the presence of 500 ppm NO2 over an 8-hour reaction time. Carbon oxidation with NO2 in the presence of a thermal catalyst is typically carried out at high temperatures (≥250 °C), producing nitric oxide as the main nitrogen-containing gaseous product. Notably, the reaction of carbon with NO2 can occur on the surface of NU / TiO2 under room temperature light irradiation.

[0057] Table 1. Photocatalytic CO2 production by NH2-UiO-66 / TiO2 and TiO2 x Generation amount

[0058]

[0059] No COx products were detected in experiments conducted with carbon particles under illumination without a photocatalyst, or in experiments conducted under dark conditions with both a photocatalyst and carbon particles. Figure 6 As shown, compared with pristine TiO2, NU / TiO2 nanomaterials exhibit superior photocatalytic performance in the carbon oxidation of NO2. CO2 generation on the NU / TiO2 surface increases with the content of NH2-UiO-66. However, when the concentration of NH2-UiO-66 reaches 30%, possibly due to the coverage of the TiO2 active sites, the CO2 generation rate actually decreases (19.3 μmol CO2 generated in half an hour). The highest CO2 generation rate is observed in the presence of 2-NU / TiO2, producing 25.2 μmol CO2 (generation rate of 0.063 mol / g). -1 h -1This is 3.9 times (6.5 μmol) the amount of CO2 generated by the pure TiO2 catalytic reaction, as shown in Table 2. Since the MOF sample has no photocatalytic activity for this reaction, there should be no synergistic effect between NH2-UiO-66 and TiO2. Characterization by photocurrent testing and electrochemical impedance spectroscopy indicates that the improved photocatalytic activity can be attributed to enhanced photogenerated charge separation and transfer at the interface between TiO2 and NH2-UiO-66. Furthermore, compared to pure TiO2, using NU / TiO2 as a photocatalyst effectively improved the NO2 to N2 conversion rate (Table 2), consistent with the CO2 generation data. The selectivity for the main byproduct N2O was effectively reduced from 33% to below 5% (Table 2). Notably, the high N2 selectivity of NU / TiO2 for NO conversion exceeds most reported photocatalytic NO removal rates in the presence of various materials, as shown in Table 2.

[0060] Table 2. Selectivity of photocatalytic products of NU / TiO2, TiO2, and NH2-UiO-66

[0061]

[0062] The band arrangement of 2-NU / TiO2 and the possible photogenerated electron-hole separation process constitute a double charge transfer mechanism. Through the formation of a junction between NH2-UiO-66 and TiO2, 2-NU / TiO2 exhibits visible light utilization and significantly improved charge transfer efficiency. Under thermal conditions, the oxidation of carbon with NO2 typically proceeds via the reaction in Formula I:

[0063] NO2 + C → NO + CO2 (Equation I)

[0064] In the presence of a photocatalyst, this would be a different situation, although the photocatalytic reaction of carbon and NO2 has not been previously reported. Even under dark conditions, NO2 adsorbed on the TiO2 surface will still react with the TiO2. 4+ Highly active NO is generated on top + Species. However, in the absence of light, CO did not form in the presence of carbon particles, NO2, and 2-NU / TiO2. x Therefore, NO generated under dark conditions + The activity for oxidizing carbon particles is insufficient. Under light irradiation, carbon particles are mainly oxidized to CO2, and NO2 is mainly converted to N2. In the presence of 2-NU / TiO2, more CO2 and less N2O are produced during the reaction, while NH2-UiO-66 does not show photocatalytic activity.

[0065] Based on the above discussion, two possible mechanisms for NO2 photocatalytic carbon oxidation in 2-NU / TiO2 nanocomposites can be proposed: (1) the Z-scheme charge separation and transfer process; and (2) the double charge transfer process. In the proposed Z-scheme mechanism, photogenerated electrons continuously move to the conduction band of NH2-UiO-66. However, products without CO2 or nitrogen are formed in the presence of NH2-UiO-66. In the double charge transfer mechanism, photogenerated holes in TiO2 migrate to the valence band of NH2-UiO-66, while photogenerated electrons in NH2-UiO-66 move to the conduction band of TiO2. Ultimately, photogenerated electrons and holes accumulate in the conduction band of TiO2 and the valence band of NH2-UiO-66, respectively, thereby greatly improving space charge separation. Enhanced charge separation can lead to the formation of NO + Further activation of the substance allows it to oxidize carbon particles. Furthermore, the high concentration of photogenerated electrons in the conduction band of TiO2 can reduce the formation of the byproduct N2O during the reaction.

Claims

1. The application of an NH2-UiO-66 / TiO2 nanocomposite material in the photocatalytic reaction of NO2 and carbon particles, characterized in that, The morphology of the material is as follows: NH2-UiO-66 aggregated nanoparticles crystallize on the surface of TiO2 hollow nanotube nanoplates to form popcorn stick-shaped NH2-UiO-66 / TiO2 nanocomposite materials. The NH2-UiO-66 aggregated nanoparticles have a diameter of 10-50 nm, the TiO2 hollow nanotubes have a diameter of 0.5-2.0 nm and a length of 4-7 nm, and the nanoplates have a thickness of 40-70 nm; the mass ratio of the NH2-UiO-66 nanoparticles to the TiO2 hollow nanotubes is 1:(2-9).

2. The application of the NH2-UiO-66 / TiO2 nanocomposite material according to claim 1 in the photocatalytic reaction of NO2 and carbon particles, characterized in that, The NH2-UiO-66 / TiO2 nanocomposite material was subjected to photocatalytic reaction of NO2 and carbon under room temperature and full-spectrum irradiation. The NO2 conversion rate was 100%, and the catalytic products included CO2 and N2, with an N2 selectivity greater than 97%.

3. The application of the NH2-UiO-66 / TiO2 nanocomposite material according to claim 1 in the photocatalytic reaction of NO2 and carbon particles, characterized in that, The mass ratio of NH2-UiO-66 nanoparticles to TiO2 hollow nanotubes is 1:9, 1:4, or 1:2.

3.

4. The application of the NH2-UiO-66 / TiO2 nanocomposite material according to any one of claims 1-3 in the photocatalytic reaction of NO2 and carbon particles, characterized in that, The preparation method of the NH2-UiO-66 / TiO2 nanocomposite material includes the following steps: (1) Preparation of TiO2 nanotubes by hydrothermal method: Titanium oxysulfate was dissolved in an alcohol solvent to obtain solution A. Glycerol and diethyl ether were added to solution A under vigorous stirring. The solution was allowed to stand at room temperature for 0.3-1h to obtain solution B. Solution B was transferred to a stainless steel pressure vessel and subjected to hydrothermal reaction at 110-140℃. After the reaction was completed, the solution was filtered, washed, dried and calcined at 550-650℃ to obtain TiO2 nanotubes. (2) The TiO2 nanotubes, zirconium chloride, DMF and concentrated hydrochloric acid described in step (1) are mixed evenly to obtain a mixed solution C. A DMF solution of 2-aminobenzoic acid is added to the mixed solution C and mixed evenly to obtain a reaction solution D. Then, the reaction is heated at 60-90 °C and centrifuged and dried to obtain the NH2-UiO-66 / TiO2.

5. The application of the NH2-UiO-66 / TiO2 nanocomposite material according to claim 4 in the photocatalytic reaction of NO2 and carbon particles, characterized in that, In step (1), the volume ratio of alcohol solvent, glycerol, and diethyl ether is 2:1:1; the alcohol solvent is selected from any one of methanol, ethanol, and isopropanol; the mass-volume ratio of titanium sulfate to glycerol and diethyl ether is 1 / 9 g / mL.

6. The application of the NH2-UiO-66 / TiO2 nanocomposite material according to claim 4 in the photocatalytic reaction of NO2 and carbon particles, characterized in that, The hydrothermal reaction time in step (1) is 8-12 h.

7. The application of the NH2-UiO-66 / TiO2 nanocomposite material according to claim 4 in the photocatalytic reaction of NO2 and carbon particles, characterized in that, The washing and drying steps described in step (1) are as follows: wash with deionized water and ethanol 5 times, and then dry at 60°C for 3 h; calcination in step (1) is performed for 3-6 h.

8. The application of the NH2-UiO-66 / TiO2 nanocomposite material according to claim 4 in the photocatalytic reaction of NO2 and carbon particles, characterized in that, The mass fraction of the concentrated hydrochloric acid in step (2) is 37%, and the volume ratio of DMF to concentrated hydrochloric acid in reaction solution D is 15:1; the ratio of the amount of TiO2 nanotubes, zirconium chloride and 2-aminobenzoic acid in step (2) is (0.17~0.5)g:0.54mmol:0.75mmol.

9. The application of the NH2-UiO-66 / TiO2 nanocomposite material according to claim 4 in the photocatalytic reaction of NO2 and carbon particles, characterized in that, The heating reaction time in step (2) is 10~14h; the centrifugal drying step in step (2) is: centrifuge with methanol 3 times, and then dry at 60℃ for 12h.

10. The application of the NH2-UiO-66 / TiO2 nanocomposite material according to claim 1 in the photocatalytic reaction of NO2 and carbon particles, characterized in that, When the mass fraction of NH2-UiO-66 in the NH2-UiO-66 / TiO2 composite material is 20%, in an environment with carbon soot particles and NO2 concentration of 500 ppm, the CO2 yield per unit mass of photocatalyst NH2-UiO-66 / TiO2 per unit time is 0.063 molg. -1 h -1 .

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