In-situ prepared CDs-loaded NH2-MIL-125 photocatalyst: research on synthesis and NO degradation application of CDs-loaded NH2-MIL-125 photocatalyst

Abstract

The invention discloses a CDs-loaded NH2-MIL-125 photocatalyst prepared in situ, and relates to research on synthesis and NO degradation application of the CDs-loaded NH2-MIL-125 photocatalyst, belonging to the field of photocatalysis. The invention develops a novel composite photocatalytic material, porous NH2-MIL-125 is used as a template, uniformly dispersed carbon nanodots (CDs) are generated in situ in holes of NH2-MIL-125 through glucose, and CDs and NH2-MIL-125 photocatalytic materials with different concentrations of glucose are obtained by adjusting the concentration of glucose. The composite photocatalyst is applied to photocatalytic degradation of NO, the NO removal efficiency can be greatly improved, good stability is achieved, the potential is achieved in the aspect of treating the NO pollution problem in the environment, and the achievement of the research provides a new thought and method for development of the photocatalytic technology and treatment of environmental pollutants.

Description

Technical Field

[0001] The invention relates to the field of photocatalysis, and in particular to a study on the synthesis and application of in-situ prepared CDs-loaded NH2-MIL-125 photocatalyst for NO degradation. Background Art

[0002] my country's main energy source is coal, which produces greenhouse gases such as sulfur dioxide, hydrogen sulfide, nitric oxide and carbon dioxide during combustion. Photocatalytic technology is an efficient and environmentally friendly purification technology that uses light as activation energy. Research on photocatalytic solar energy conversion and utilization is of great significance to optimizing my country's energy structure. Nitrogen oxides (NO x ) is an important precursor of secondary organic aerosols and an emerging atmospheric ozone pollutant. It is one of the more serious atmospheric pollutants and can cause acid rain and global warming. In high-temperature combustion and industrial production, NO x The emissions are mainly NO and NO2, of which NO accounts for about 95%. x When conducting research on NO, NO is often taken as the main research object. Taking effective management and technical measures to strengthen the control of NO is an important way to improve air quality.

[0003] Metal organic frameworks (MOFs) are composed of organic ligands and metal ions or clusters. They have unique characteristics, such as ordered pore structures and extremely large specific surface areas, and are widely used in the field of photocatalysis. NH2-MIL-125 is a common MOF with visible light response, but its photocatalytic activity is still limited by weak visible light response and difficulty in separating photogenerated electron-hole pairs. Therefore, introducing other functional materials into the pores of MOFs to enhance their photocatalytic performance is one of the many feasible strategies to improve photocatalytic performance. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing an in-situ prepared CDs-loaded NH2-MIL-125 photocatalyst. The method is simple and convenient, and the in-situ prepared CDs@NH2-MIL-125 photocatalyst has high catalytic activity.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0006] The method for preparing the in-situ prepared CDs-loaded NH2-MIL-125 photocatalyst comprises the following steps:

[0007] (1) Using 2-aminoterephthalic acid and titanium isopropoxide as raw materials, the intermediate NH2-MIL-125 photocatalyst was prepared by a hydrothermal method;

[0008] (2) The intermediate NH2-MIL-125 was added to glucose solutions of different concentrations, and after stirring and high-temperature calcination, the in-situ prepared CDs@NH2-MIL-125 photocatalyst was obtained.

[0009] Wherein, in the step (1), the molar ratio of 2-aminoterephthalic acid to titanium isopropoxide is (1.63:1).

[0010] Wherein, in the step (1), anhydrous methanol and anhydrous N,N-dimethylformamide are used as solvents, and after being fully dissolved, the mixture is transferred into a reaction kettle and subjected to hydrothermal reaction at 110 degrees Celsius for 72 hours.

[0011] Wherein, in step (2), the concentrations of the glucose solution are: 1, 5, 10, 20, and 30 mM, respectively.

[0012] Wherein, in the step (2), the stirring time is 6 hours and the temperature is room temperature.

[0013] Wherein, in the step (2), the high temperature calcination temperature is 240 degrees Celsius and the time is 2 hours.

[0014] The present invention also provides the application of the in-situ prepared CDs-loaded NH2-MIL-125 photocatalyst, and the prepared CDs@NH2-MIL-125 photocatalyst is used for photocatalytic NO removal.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] 1. The preparation method of the in-situ prepared CDs-loaded NH2-MIL-125 photocatalyst provided by the present invention is to use the metal organic framework NH2-MIL-125 as a template, disperse it in a glucose solution and stir it at room temperature, and then calcine it at high temperature to obtain a CDs@NH2-MIL-125 photocatalyst in which carbon nanodots are uniformly distributed in the pores of MOFs. CDs have an upconversion effect and a photosensitization effect. Encapsulating them in the pores of NH2-MIL-125 can prolong the life of the photogenerated electron-hole pairs, thereby having an excellent photocatalytic NO removal effect.

[0017] 2. Compared with the original NH2-MIL-125, the efficiency of photocatalytic degradation of NO by CDs@NH2-MIL-125 increased by 2.15 times within 30 minutes under visible light irradiation, while the production of toxic gas NO2 was inhibited. After five cycles, the activity of the catalyst was almost unaffected.

[0018] 3. The present invention is simple to operate, has mild conditions, and has low equipment requirements. It is an environmentally friendly and simple preparation method. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 These are the XRD spectra of NH2-MIL-125, CDs@NH2-MIL-125 (1mM), CDs@NH2-MIL-125 (5mM), CDs@NH2-MIL-125 (10mM), CDs@NH2-MIL-125 (20mM) and CDs@NH2-MIL-125 (30mM) of Examples 1-6 of the present invention.

[0020] Figure 2 It is the FT-IR spectra of NH2-MIL-125, CDs@NH2-MIL-125 (1mM), CDs@NH2-MIL-125 (5mM), CDs@NH2-MIL-125 (10mM), CDs@NH2-MIL-125 (20mM) and CDs@NH2-MIL-125 (30mM) of Examples 1-6 of the present invention.

[0021] Figure 3 It is the EDX point scanning spectrum of the surface of NH2-MIL-125 and CDs@NH2-MIL-125 (10mM) of Examples 1 and 4 of the present invention.

[0022] Figure 4 It is the N1s XPS spectra of NH2-MIL-125 and CDs@NH2-MIL-125 of Examples 1 and 4 of the present invention.

[0023] Figure 5 It is the C1s XPS spectra of NH2-MIL-125 and CDs@NH2-MIL-125 of Examples 1 and 4 of the present invention.

[0024] Figure 6 This is a graph of photocatalytic NO removal by NH2-MIL-125, CDs@NH2-MIL-125 (1mM), CDs@NH2-MIL-125 (5mM), CDs@NH2-MIL-125 (10mM), CDs@NH2-MIL-125 (20mM) and CDs@NH2-MIL-125 (30mM) of Examples 1-6 of the present invention. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0026] Embodiment 1:

[0027] The preparation method of NH2-MIL-125 comprises the following steps:

[0028] (1) 2-aminoterephthalic acid (1.086 g) was dissolved in 20 mL of a mixed solution of anhydrous N,N-dimethylformamide and anhydrous methanol (v=1:1). The mixture was then stirred for 20 minutes, and tetrabutyl titanate (0.52 mL) was added thereto. After heat treatment at 150°C for 20 hours in a stainless steel autoclave, the mixture was allowed to cool to room temperature.

[0029] (2) washing the solid obtained by filtration in (1) by centrifugation with DMF and methanol for 3-4 times respectively;

[0030] (3) The solid obtained in (2) is dried under vacuum to obtain NH2-MIL-125.

[0031] Embodiment 2:

[0032] The synthesis of CDs@NH2-MIL-125 (1 mM) photocatalyst includes the following steps:

[0033] (1) The NH2-MIL-125 synthesized in Example 1 was dispersed in a glucose solution with a concentration of 1 mM and stirred at room temperature for 6 hours.

[0034] (2) washing the solid obtained by filtration in (1) several times by centrifugation with distilled water and anhydrous ethanol;

[0035] (3) drying the solid obtained in (2) under vacuum at 80°C to obtain CDs@NH2-MIL-125;

[0036] (4) The solid obtained in (3) was transferred to a tube furnace and calcined at 240 °C in a nitrogen flow for 2 h to obtain CDs@NH2-MIL-125 (1 mM).

[0037] Embodiment 3:

[0038] The synthesis of CDs@NH2-MIL-125 (5 mM) photocatalyst includes the following steps:

[0039] (1) The NH2-MIL-125 synthesized in Example 1 was dispersed in a 5 mM glucose solution and stirred at room temperature for 6 hours.

[0040] (2) washing the solid obtained by filtration in (1) several times by centrifugation with distilled water and anhydrous ethanol;

[0041] (3) drying the solid obtained in (2) under vacuum at 80°C to obtain CDs@NH2-MIL-125;

[0042] (4) The solid obtained in (3) was transferred to a tube furnace and calcined at 240 °C in a nitrogen flow for 2 h to obtain CDs@NH2-MIL-125 (5 mM).

[0043] Embodiment 4:

[0044] The synthesis of CDs@NH2-MIL-125 (10 mM) photocatalyst includes the following steps:

[0045] (1) The NH2-MIL-125 synthesized in Example 1 was dispersed in a 10 mM glucose solution and stirred at room temperature for 6 hours.

[0046] (2) washing the solid obtained by filtration in (1) several times by centrifugation with distilled water and anhydrous ethanol;

[0047] (3) drying the solid obtained in (2) under vacuum at 80°C to obtain CDs@NH2-MIL-125;

[0048] (4) The solid obtained in (3) was transferred to a tube furnace and calcined at 240 °C in a nitrogen flow for 2 h to obtain CDs@NH2-MIL-125 (10 mM).

[0049] Embodiment 5:

[0050] The synthesis of CDs@NH2-MIL-125 (20 mM) photocatalyst includes the following steps:

[0051] (1) The NH2-MIL-125 synthesized in Example 1 was dispersed in a 20 mM glucose solution and stirred at room temperature for 6 hours.

[0052] (2) washing the solid obtained by filtration in (1) several times by centrifugation with distilled water and anhydrous ethanol respectively;

[0053] (3) drying the solid obtained in (2) under vacuum at 80°C to obtain CDs@NH2-MIL-125;

[0054] (4) The solid obtained in (3) was transferred to a tube furnace and calcined at 240 °C in a nitrogen flow for 2 h to obtain CDs@NH2-MIL-125 (20 mM).

[0055] Embodiment 6:

[0056] The synthesis of CDs@NH2-MIL-125 (30 mM) photocatalyst includes the following steps:

[0057] (1) The NH2-MIL-125 synthesized in Example 1 was dispersed in a 30 mM glucose solution and stirred at room temperature for 6 hours.

[0058] (2) washing the solid obtained by filtration in (1) several times by centrifugation with distilled water and anhydrous ethanol;

[0059] (3) drying the solid obtained in (2) under vacuum at 80°C to obtain CDs@NH2-MIL-125;

[0060] (4) The solid obtained in (3) was transferred to a tube furnace and calcined at 240 °C in a nitrogen flow for 2 h to obtain CDs@NH2-MIL-125 (30 mM).

[0061] NH2-MIL-125, CDs@NH2-MIL-125 (1 mM), and CDs@NH2-MIL-125 (1 mM) obtained in Examples 1-6 were mixed with

[0062] (5mM), CDs@NH2-MIL-125(10mM), CDs@NH2-MIL-125(20mM) and CDs@NH2-MIL-125(30mM) materials were analyzed and tested. The XRD spectra of the prepared materials are shown in Figure 1 As shown, the FT-IR spectrum (Fourier transform infrared spectrometer) is as follows Figure 2 As shown, the EDX point scan of the CDs@NH2-MIL-125 (10 mM) surface is as follows Figure 3 As shown, the N 1s XPS spectra of NH2-MIL-125 and CDs@NH2-MIL-125 (10 mM) materials are shown in Figure 4 As shown in the figure, and the C1s XPS spectrum is as follows Figure 5 Combining XRD and FT-IR, it can be confirmed that the crystal structure of NH2-MIL-125 is not destroyed after doping with CDs particles, and the C content of CDs@NH2-MIL-125 is high. XPS shows the changes in the corresponding peaks of CN bonds and CC bonds after the introduction of CDs.

[0063] Embodiment 7:

[0064] Photocatalytic NO performance test

[0065] 200 mg of the photocatalytic materials of NH2-MIL-125, CDs@NH2-MIL-125 (1 mM), CDs@NH2-MIL-125 (5 mM), CDs@NH2-MIL-125 (10 mM), CDs@NH2-MIL-125 (20 mM) and CDs@NH2-MIL-125 (30 mM) obtained in Examples 1 to 6 were weighed and dispersed in a certain amount of anhydrous ethanol, ultrasonicated for 30 min, and then transferred to be evenly distributed on a culture dish with a diameter of 12 cm, and placed in an oven to dry to remove the solvent. After cooling to room temperature, the culture dish was placed in a NO reactor, and a 150 W halogen lamp was installed above the reactor, and a 420 nm ultraviolet filter was installed. Secondly, by setting the flow rate of NO gas (24 mL / min) and air (2.4 L / min), the initial concentration of the pollutant gas was stabilized at 500 ppb, and the relative humidity was maintained at 50%. Finally, use NO x The concentrations of NO and nitrogen dioxide in the reactor were observed in real time by an analyzer (Thermo Environmental Instruments, Model 42c-TL).

[0066] The NO removal rates of the materials prepared in Examples 1 to 6 are shown in Table 1.

[0067] Example Removal rate (%) Example 1 24.6 Example 2 32.3 Example 3 47.1 Example 4 53.8 Example 5 51.2 Example 6 52.4

[0068] See also Figure 6 , Example 1 exhibits a low NO removal rate, while Example 4 has a maximum NO removal rate of 53.8%, which is 2.15 times that of Example 1. The excellent performance can be attributed to the fact that the in-situ formed CDs can be uniformly dispersed in the pores of NH2-MIL-125, making it easier to contact the central metal cluster, thereby promoting the transfer of photogenerated charge carriers to the central metal cluster. In addition, -NH2 can interact with -OH / -COOH on the surface of CDs through chemical bonding forces (such as hydrogen bonds), which can bring CDs close to the central metal cluster to improve the efficiency of the upconversion or photosensitivity of CDs, which is beneficial to the improvement of photocatalytic performance.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the technical solution. Those skilled in the art should understand that those modifications or equivalent substitutions of the technical solution of the present invention that do not depart from the purpose and scope of the technical solution should be included in the scope of the claims of the present invention.

Claims

1. A method for preparing an in-situ prepared CDs-loaded NH2-MIL-125 photocatalyst, characterized in that: The steps include: (1) Using 2-aminoterephthalic acid and titanium isopropoxide as raw materials, the intermediate NH2-MIL-125 photocatalyst was prepared by a hydrothermal method; (2) The intermediate NH2-MIL-125 was added into glucose solutions of different concentrations, and after stirring and high-temperature calcination, the in-situ prepared CDs-loaded NH2-MIL-125 photocatalyst was obtained.

2. The method for preparing the in-situ prepared CDs-loaded NH2-MIL-125 photocatalyst according to claim 1, characterized in that: In the step (1), the molar ratio of 2-aminoterephthalic acid to titanium isopropoxide is 1.63:

1.

3. The method for preparing the in-situ prepared CDs-loaded NH2-MIL-125 photocatalyst according to claim 1, characterized in that: In the step (1), anhydrous methanol and anhydrous N,N-dimethylformamide are used as solvents, and after being fully dissolved, the mixture is transferred into a reaction kettle and subjected to hydrothermal reaction at 110 degrees Celsius for 72 hours.

4. The method for preparing the in-situ prepared CDs-loaded NH2-MIL-125 photocatalyst according to claim 1, characterized in that: In the step (2), the concentrations of the glucose solution are respectively: 1, 5, 10, 20, and 30 mM.

5. The method for preparing the in-situ prepared CDs-loaded NH2-MIL-125 photocatalyst according to claim 1, characterized in that: In the step (2), the stirring time is 6 hours and the temperature is room temperature.

6. The method for preparing the in-situ prepared CDs-loaded NH2-MIL-125 photocatalyst according to claim 1, characterized in that: In the step (2), the high temperature calcination temperature is 240 degrees Celsius and the time is 2 hours.

7. Application of the in-situ prepared CDs-loaded NH2-MIL-125 photocatalyst, characterized in that: The in-situ prepared CDs-loaded NH2-MIL-125 photocatalyst prepared by any preparation method of claims 1-6 is used for photocatalytic removal of NO.

Images