CN113398968A

CN113398968A - MOF-derived TiO2Porous g-C3N4Composite photocatalyst and preparation method and application thereof

Info

Publication number: CN113398968A
Application number: CN202110567409.1A
Authority: CN
Inventors: 孙剑辉; 李冰宇; 张炳楠; 张雅楠; 张梦珂; 黄伟宏; 李昊倩; 冯精兰; 崔延瑞; 董淑英; 禹崇菲
Original assignee: Henan Normal University
Current assignee: Henan Normal University
Priority date: 2021-05-24
Filing date: 2021-05-24
Publication date: 2021-09-17
Anticipated expiration: 2041-05-24
Also published as: CN113398968B

Abstract

The invention belongs to the technical field of photocatalysts, and particularly relates to MOF (Metal organic framework) -derived TiO₂Porous g-C₃N₄A composite photocatalyst and a preparation method and application thereof. What is needed isThe MOF-derived TiO₂Porous g-C₃N₄The preparation method of the composite photocatalyst comprises the step of preparing MOF-derived TiO₂With a porous g-C₃N₄The precursors are mixed evenly, then calcined for 0.5 to 5 hours at the temperature of 450-600 ℃, and washed, filtered and dried in sequence after being cooled to obtain the MOF-derived TiO₂Porous g-C₃N₄A composite photocatalyst is provided. The invention synthesizes MOF-derived TiO by a simple mixed calcination method₂Porous g-C₃N₄The composite photocatalyst has the advantages of simple preparation method and appropriate reaction conditions, and is suitable for large-scale popularization.

Description

MOF-derived TiO2Porous g-C3N4Composite photocatalyst and preparation method and application thereof

Technical Field

The invention belongs to the technical field of photocatalysts, and particularly relates to MOF (Metal organic framework) -derived TiO₂Porous g-C₃N₄A composite photocatalyst and a preparation method and application thereof.

Background

Hydrogen having the highest calorific value among all chemical fuels is considered as an important potential energy source to solve the problems of environmental pollution and energy shortage. All techniques for generating hydrogen include hydrogen production by electrolysis of water, hydrogen production by cracking fossil energy, and hydrogen production by photolysis of water. Among them, photolysis of water to produce hydrogen is considered as a promising approach. Graphite phase carbon nitride (g-C)₃N₄) Is applied to the field of photocatalysis by Wang et al for the first time in 2009, but is easy to recombine due to photo-generated chargesSo as to be pure g-C₃N₄The photocatalytic performance of (b) is not ideal. And is an effective method by introducing a porous structure. In the method, green and environment-friendly NaCl is used as a template to synthesize porous g-C₃N₄The photocatalytic activity is effectively improved. In addition, it is a common method to construct a heterojunction with other materials.

TiO₂The photocatalyst is a semiconductor photocatalyst which is firstly applied to a water photolysis technology and has the advantages of high stability, no toxicity, low price and the like. But it can only respond to ultraviolet light which accounts for 5% of the solar spectrum, resulting in low utilization rate of sunlight. Therefore, this problem can be solved by semiconductor modification, element doping, and the like.

And NH₂MIL-125(Ti), a classic representative of the emerging materials Metal Organic Frameworks (MOFs), has been shown to be nitrogen-fixing, CO-fixing, because of its non-toxicity, stability in water/light and visible light response₂Reduction and the like. By reacting with NH₂TiO product produced by pyrolysis with-MIL-125 (Ti) as template₂The characteristics of some MOFs, such as the framework structure, pore volume and excellent electron transfer rate of the MOFs, can be selectively preserved.

In view of the above, there is provided a MOF-derived TiO₂Porous g-C₃N₄The composite photocatalyst is particularly important in the field of high-efficiency hydrogen production catalysis.

Disclosure of Invention

To overcome the problems of the prior art, the present invention provides a MOF-derived TiO₂Porous g-C₃N₄The composite photocatalyst has good photocatalytic activity, and the hydrogen production amount is continuous and stable in a visible light catalytic hydrogen production test.

The invention also provides a preparation method of the catalyst, which is simple, has proper reaction conditions and is suitable for large-scale popularization.

The invention also provides the application of the catalyst, which can be used for producing hydrogen by photocatalysis.

In order to achieve the purpose, the technical scheme of the invention is as follows:

MOF-derived TiO₂Porous g-C₃N₄Preparation method of composite photocatalyst, MOF-derived TiO₂With a porous g-C₃N₄The precursors are mixed evenly, then calcined for 0.5 to 5 hours at the temperature of 450-600 ℃, and washed, filtered and dried in sequence after being cooled to obtain the MOF-derived TiO₂Porous g-C₃N₄A composite photocatalyst is provided.

Preferably, the MOF-derived TiO₂Is NH₂-MIL-125（Ti）。

Preferably, the MOF-derived TiO₂The preparation method comprises the following steps: adding 2-amino terephthalic acid and tetrabutyl titanate into a mixed solvent of DMF and methanol, and uniformly mixing to obtain a mixed solution; carrying out hydrothermal reaction on the mixed solution, and then cooling, washing and drying to obtain powder; calcining the powder to obtain the catalyst.

Preferably, the porous g-C₃N₄The preparation method of the precursor comprises the following steps: dissolving dicyanodiamine in ethanol to obtain a solution A; dissolving NaCl in water to obtain solution B; and adding the solution B into the solution A under the stirring condition to generate a white precipitate, and then filtering and drying the white precipitate to obtain the compound.

Preferably, the MOF-derived TiO₂With a porous g-C₃N₄The mass ratio of the precursors is (2-10): 800-1000).

Preferably, drying is carried out at 55-65 ℃ for 4-20 h.

MOF-derived TiO prepared by the method₂Porous g-C₃N₄A composite photocatalyst is provided.

The MOF-derived TiO₂Porous g-C₃N₄The composite photocatalyst is applied to photocatalytic hydrogen production.

Compared with the prior art, the invention has the beneficial effects that:

1. the invention adopts MOF as a framework material, has the characteristics of high porosity, low density, large specific surface area and the like, and derived TiO₂Is a semiconductor material with high stability, and can selectively preserve some MOF characteristics, such asThe framework structure, pore volume, and excellent electron transfer rate of MOFs;

2. synthesis of MOF-derived TiO by simple Mixed calcination Process₂Porous g-C₃N₄The composite photocatalyst has simple preparation method and appropriate reaction conditions, and is suitable for large-scale popularization;

3. MOF-derived TiO prepared according to the invention₂Porous g-C₃N₄The photocatalyst has good photocatalytic activity, and the hydrogen production amount is continuous and stable in a visible light catalytic hydrogen production test;

4. the organic pollutant is used for replacing the sacrificial agent, so that the constraint of the sacrificial agent is eliminated, and the organic pollutant can be degraded while the hydrogen yield is stable in a visible light catalytic hydrogen production test.

Drawings

FIG. 1 shows the photocatalysts and MOF-derived TiO prepared in comparative example 1 and example 3₂An XRD pattern of (a);

FIG. 2 is a scanning electron micrograph of the photocatalyst prepared in comparative example 1 and example 3 and a transmission electron micrograph of the photocatalyst prepared in example 3;

FIG. 3 is a time-hydrogen production curve and a histogram of average hydrogen production for 5h of reaction for photocatalysts prepared in examples 1-4 and comparative examples 1-2;

FIG. 4 is a UV-VISIBLE absorption spectrum of an aqueous RhB solution before and after a photocatalytic test using the photocatalyst of example 3.

Detailed Description

The invention is further illustrated, but not limited, by the following examples and the accompanying drawings.

Example 1

This example MOF-derived TiO₂Porous g-C₃N₄The preparation method of the composite photocatalyst comprises the following steps:

(1) MOF-derived TiO₂Synthesis of (2)

①NH₂Preparation of MIL-125 (Ti): 0.54 g of 2-aminoterephthalic acid and 0.7 mL of tetrabutyltitanate are weighed into 20mL of a mixed solvent of DMF and methanol (volume ratio of DMF to methanol is 7: 3) under magnetic stirringMagnetically stirring for 30 min, reacting at 150 deg.C for 16 h in hydrothermal kettle, naturally cooling to room temperature, washing with 20ml DMF and 20ml methanol for 3 times, vacuum drying for 12h, collecting and grinding to obtain NH₂-MIL-125(Ti)；

② weighing NH in the step I₂placing-MIL-125 (Ti) into a quartz boat, calcining for 2h at 550 ℃, and cooling to obtain the catalyst.

(2) Porous g-C₃N₄Preparation of the precursor

Adding 1.125 g of dicyanodiamine into 125 mL of ethanol, and performing ultrasonic dispersion until the dicyanodiamine is completely dissolved to obtain a solution A; adding 7.8g of NaCl into 23mL of deionized water, and completely dissolving the NaCl under magnetic stirring to obtain a solution B;

dripping the solution B into the solution A dropwise under the condition of magnetic stirring to generate white precipitate in the process, then obtaining white solid by rotary evaporation, and collecting the white solid precipitate;

thirdly, putting the white solid precipitate into a vacuum drying oven, drying for 6 hours at 60 ℃, grinding and collecting the solid after drying, and finally obtaining the porous g-C₃N₄A precursor.

(3) MOF-derived TiO₂Porous g-C₃N₄Preparation of composite photocatalyst

Firstly, 4.5g of porous g-C₃N₄Precursor and 20 mg MOF-derived TiO₂Uniformly mixing and grinding, placing the white solid obtained after grinding into a quartz boat, calcining for 2h at 550 ℃, cooling, collecting a ground sample, and washing the sample with deionized water to remove redundant NaCl;

② filtering, drying for 12h in a vacuum drying oven at 60 ℃, finally grinding and collecting TO obtain the composite catalyst which is marked as 1-TO/PCN.

Testing the photocatalytic performance of the 1-TO/PCN composite photocatalyst:

an experiment of decomposing water with visible light TO produce hydrogen is respectively carried out in 100 ml of Triethanolamine (TEOA) aqueous solution (wherein the volume of the triethanolamine is 15ml, and the volume of the water is 85 ml) and 100 ml of rhodamine B (RhB) aqueous solution (wherein the concentration of the RhB is 5 mg/L), and the experiment is used for detecting the photocatalytic activity of the 1-TO/PCN composite photocatalyst.

20 mg of the catalyst prepared in this example was weighed, and 400. mu.L of chloroplatinic acid (7.72 mmol. multidot.L) was added^-1) As a cocatalyst, the reactor was evacuated to remove dissolved oxygen. After the reaction, samples were taken every hour under the irradiation of a 300W xenon lamp (420 nm filter), and online analysis was performed by a TCD detector of a gas chromatograph to obtain the amount of hydrogen produced.

The photocatalytic test shows that the average (per hour) hydrogen production is 1007.1 mu mol.h when the reaction is carried out for 5 hours continuously^-1·g^-1(aqueous TEOA solution) and 666.6. mu. mol. multidot. h^-1·g^-1(aqueous RhB solution).

Example 2

This example differs from example 1 in that: MOF-derived TiO in step (3)₂Porous g-C₃N₄The preparation method of the composite photocatalyst comprises the following specific processes:

preparation of MOF-derived TiO₂Porous g-C₃N₄Photocatalyst and process for producing the same

Firstly, 4.5g of porous g-C₃N₄Precursor and 30 mg MOF-derived TiO₂Uniformly mixing and grinding, placing the white solid obtained after grinding into a quartz boat, calcining for 2h at 550 ℃, cooling, collecting a ground sample, and washing the sample with deionized water to remove redundant NaCl;

② filtering, drying for 12h in a vacuum drying oven at 60 ℃, finally grinding and collecting TO obtain the composite catalyst which is recorded as 2-TO/PCN.

The photocatalytic performance test of the 2-TO/PCN composite photocatalyst has the same catalyst dosage and test method as those of example 1.

The photocatalytic test shows that the average (per hour) hydrogen production is 1898.9 mu mol.h when the reaction is carried out for 5 hours continuously^-1·g^-1(aqueous TEOA solution) and 1783.5. mu. mol. multidot.h^-1·g^-1(aqueous RhB solution).

Example 3

This example differs from example 1 in that: the first (3)TiO derived from step MOF₂Porous g-C₃N₄The preparation method of the composite photocatalyst comprises the following specific processes:

Firstly, 4.5g of porous g-C₃N₄Precursor and 40 mg MOF-derived TiO₂Uniformly mixing and grinding, placing the white solid obtained after grinding into a quartz boat, calcining for 2h at 550 ℃, cooling, collecting a ground sample, and washing the sample with deionized water to remove redundant NaCl;

② filtering, drying for 12h in a vacuum drying oven at 60 ℃, finally grinding and collecting TO obtain the composite catalyst which is marked as 3-TO/PCN.

The photocatalytic performance test of the 3-TO/PCN composite photocatalyst has the same catalyst dosage and test method as those of example 1.

The photocatalytic test shows that the average (per hour) hydrogen production is 2267.4 mu mol.h when the reaction is carried out for 5 hours continuously^-1·g^-1(aqueous TEOA solution) and 2137.3. mu. mol. multidot.h^-1·g^-1(aqueous RhB solution).

Example 4

Firstly, 4.5g of porous g-C₃N₄Precursor and 50 mg MOF-derived TiO₂Uniformly mixing and grinding, placing the white solid obtained after grinding into a quartz boat, calcining for 2h at 550 ℃, cooling, collecting a ground sample, and washing the sample with deionized water to remove redundant NaCl;

② filtering, drying for 12h in a vacuum drying oven at 60 ℃, finally grinding and collecting TO obtain the composite catalyst which is marked as 4-TO/PCN.

The photocatalytic performance of the 4-TO/PCN composite photocatalyst is tested, and the dosage and the testing method of the catalyst are the same as those of the example 1.

The photocatalytic test shows that the average (per hour) hydrogen production is 1885.8 mu mol.h when the reaction is carried out for 5 hours continuously^-1·g^-1(aqueous TEOA solution) and 1709.7. mu. mol. multidot.h^-1·g^-1(aqueous RhB solution).

Example 5

Firstly, 10 g of porous g-C₃N₄Precursor and 20 mg MOF-derived TiO₂Mixing and grinding uniformly, placing the white solid obtained after grinding into a quartz boat, calcining for 0.5 h at 600 ℃, cooling, collecting a ground sample, and washing the sample with deionized water to remove redundant NaCl;

② filtering, drying for 4h in a vacuum drying oven at 65 ℃, and finally grinding and collecting.

Example 6

Firstly, 2g of porous g-C₃N₄Precursor and 10 mg MOF-derived TiO₂Uniformly mixing and grinding, placing the white solid obtained after grinding into a quartz boat, calcining for 5 hours at 450 ℃, cooling, collecting a ground sample, and washing the sample with deionized water to remove redundant NaCl;

② filtering, drying for 20h in a vacuum drying oven at 55 ℃, and finally grinding and collecting.

Comparative example 1

Weighing 4.5g of porous g-C₃N₄The precursor (prepared in the same manner as in example 1) was calcined in a quartz boat at 550 ℃ for 2 hours,after cooling, collecting a ground sample, and washing the sample by using deionized water to remove redundant NaCl; then filtering, drying for 12h in a vacuum drying oven at 60 ℃, and finally grinding and collecting to obtain porous g-C₃N₄Photocatalyst (denoted as PCN).

The photocatalytic performance of the PCN photocatalyst was tested using the same catalyst and test method as in example 1.

The photocatalytic test shows that the average (per hour) hydrogen production is 748.8 mu mol.h when the reaction is carried out for 5 hours continuously^-1·g^-1(aqueous TEOA solution) and 445.6. mu. mol. multidot. h^-1·g^-1(aqueous RhB solution).

Comparative example 2

Weighing 4.5g of dicyandiamide, placing the dicyandiamide in a quartz boat, calcining the quartz boat for 2 hours at 550 ℃, cooling the quartz boat, collecting a ground sample, and obtaining blocky g-C₃N₄Photocatalyst (noted as BCN).

Testing the photocatalytic performance of the BCN photocatalyst:

a visible light decomposition water hydrogen production experiment was performed in 100 ml of an aqueous solution of Triethanolamine (TEOA) in which the volume of the triethanolamine was 15ml, to detect the photocatalytic activity of the BCN photocatalyst in an amount of 20 mg, and 400. mu.L of chloroplatinic acid (7.72 mmol. L.) was added^-1) As a cocatalyst. And (3) vacuumizing the reactor, removing dissolved oxygen, after the reaction starts, sampling once every hour under the irradiation of a 300W xenon lamp (420 nm filter), and performing online analysis by a TCD (thermal conductivity detector) of a gas chromatograph to obtain the hydrogen yield.

The photocatalytic test shows that the average (per hour) hydrogen production is 329.1 mu mol.h after 5 hours of continuous reaction^-1·g^-1(aqueous TEOA solution).

Photocatalyst (PCN) prepared in comparative example 1, photocatalyst (3-TO/PCN) prepared in example 3, and MOF-derived TiO₂The XRD pattern of (TO) is shown in FIG. 1. As can be seen from FIG. 1, the MOF-derived TiO₂Porous g-C₃N₄The composite photocatalyst has characteristic peaks of PCN and TO, and proves that MOF-derived TiO₂Successfully attached to g-C₃N₄The above.

The scanning electron micrograph of the Photocatalyst (PCN) prepared in comparative example 1, the photocatalyst (3-TO/PCN) prepared in example 3, and the transmission electron micrograph of the photocatalyst prepared in example 3 are shown in FIG. 2; wherein: in FIG. 2, a and b are SEM pictures of PCN and 3-TO/PCN, respectively, and c in FIG. 2 is TEM picture of 3-TO/PCN. As can be seen from FIG. 2, the photocatalyst of example 3 is subjected to MOF-derivatized TiO₂After mixed calcination, MOF-derived TiO was observed₂Successfully attached to g-C₃N₄The above.

The performance of the different photocatalysts prepared in examples 1-4 and comparative examples 1-2 was evaluated by a photolysis water hydrogen production experiment, and the results are shown in fig. 3; wherein: in FIG. 3, (a) and (b) are catalyst performances in an aqueous TEOA solution, specifically, (a) is a time-hydrogen production curve of the photocatalysts prepared in examples 1-4 and comparative examples 1-2, and (b) is a histogram of the average hydrogen production of the photocatalysts prepared in examples 1-4 and comparative examples 1-2 at reaction time 5 h; in fig. 3, (c) and (d) are catalyst performances in RhB aqueous solution, specifically, (c) is a time-hydrogen production curve of the photocatalysts prepared in examples 1 to 4 and comparative examples 1 to 2, and (d) is a histogram of average hydrogen production of the photocatalysts prepared in examples 1 to 4 and comparative examples 1 to 2 at reaction time 5 h. It should be noted that: the hydrogen production amounts in (a) and (c) in FIG. 3 refer to the cumulative hydrogen production amount, and the hydrogen production amounts in (b) and (d) refer to the average hydrogen production amount per hour for 5h with continuous hydrogen production (e.g., (b) is a value obtained by dividing the value at 5h in (a) by 5).

As can be seen from FIGS. 3 (a) and (b), six groups of catalysts showed different hydrogen-generating capacities, and the average hydrogen generation amount per hour was 2267.4. mu. mol. h after the optimum photocatalyst (3-TO/PCN) continued the catalytic reaction for 5 hours^-1·g^-16.8 times and 3 times of BCN and PCN, respectively. As can be seen from FIGS. 3 (c) and (d), the photocatalyst 3-TO/PCN also exhibited the best hydrogen generation ability in 5 mg/L RhB solution by using the organic contaminant (RhB) instead of the sacrificial agent (TEOA) (after 5 hours of continuous reaction, the average hydrogen generation amount per hour reached 2137.3. mu. mol. h)^-1·g^-1）。

Meanwhile, before and after the photocatalytic test using the photocatalyst of example 3, the ultraviolet-visible absorption spectrum of the RhB aqueous solution is shown in fig. 4. As can be seen from fig. 4, after the light hydrogen production test, the absorbance of the RhB solution is attenuated, which indicates that example 3 realizes purification of RhB wastewater while producing hydrogen.

Claims

1. MOF-derived TiO₂Porous g-C₃N₄The preparation method of the composite photocatalyst is characterized in that MOF-derived TiO is used₂With a porous g-C₃N₄The precursors are mixed evenly, then calcined for 0.5 to 5 hours at the temperature of 450-600 ℃, and washed, filtered and dried in sequence after being cooled to obtain the MOF-derived TiO₂Porous g-C₃N₄A composite photocatalyst is provided.

2. The MOF-derived TiO of claim 1₂Porous g-C₃N₄The preparation method of the composite photocatalyst is characterized in that MOF-derived TiO₂Is NH₂-MIL-125（Ti）。

3. The MOF-derived TiO of claim 2₂Porous g-C₃N₄A method for preparing a composite photocatalyst, characterized in that the MOF-derived TiO₂The preparation method comprises the following steps: adding 2-amino terephthalic acid and tetrabutyl titanate into a mixed solvent of DMF and methanol, and uniformly mixing to obtain a mixed solution; carrying out hydrothermal reaction on the mixed solution, and then cooling, washing and drying to obtain powder; calcining the powder to obtain the catalyst.

4. The MOF-derived TiO of claim 1₂Porous g-C₃N₄The preparation method of the composite photocatalyst is characterized in that the porous g-C₃N₄The preparation method of the precursor comprises the following steps: dissolving dicyanodiamine in ethanol to obtain a solution A; dissolving NaCl in water to obtain solution B; adding the solution B into the solution A under the condition of stirring to generateWhite precipitate, filtering and drying to obtain the product.

5. The MOF-derived TiO of claim 1₂Porous g-C₃N₄A method for preparing a composite photocatalyst, characterized in that the MOF-derived TiO₂With a porous g-C₃N₄The mass ratio of the precursors is (2-10): 800-1000).

6. The MOF-derived TiO of claim 1₂Porous g-C₃N₄The preparation method of the composite photocatalyst is characterized in that the composite photocatalyst is dried for 4-20 hours at the temperature of 55-65 ℃.

7. MOF-derived TiO prepared by the method of any one of claims 1 to 6₂Porous g-C₃N₄A composite photocatalyst is provided.

8. The MOF-derived TiO of claim 7₂Porous g-C₃N₄The composite photocatalyst is applied to photocatalytic hydrogen production.