阅读说明：本技术 一种基于氨基配位稳定的石墨相氮化碳-过渡金属基半导体复合光催化材料的制备方法 (Preparation method of graphite-phase carbon nitride-transition metal-based semiconductor composite photocatalytic material based on stable amino coordination ) 是由 靳军涛 刘洪� 安瑞 杨小兵 田禹 李代坤 于 2021-09-24 设计创作，主要内容包括：一种基于氨基配位稳定的石墨相氮化碳-过渡金属基半导体复合光催化材料的制备方法,属于光催化技术领域。本发明要解决现有通过简单热聚合法制备得到的石墨烯氮化碳比表面积小,水中分散性差,可见光响应弱,与过渡金属基半导体材料复合后过渡金属不稳定,易溶出的问题。方法：一、制备多孔石墨相氮化碳前驱体；二、制备多孔石墨相氮化碳；三、制备石墨相氮化碳分散液；四、过渡金属与多孔石墨相氮化碳混合；五、共沉淀。本发明用于基于氨基配位稳定的石墨相氮化碳-过渡金属基半导体复合光催化材料的制备。(A preparation method of a graphite phase carbon nitride-transition metal based semiconductor composite photocatalytic material based on stable amino coordination belongs to the technical field of photocatalysis. The invention aims to solve the problems that the graphene carbon nitride prepared by the simple thermal polymerization method has small specific surface area, poor dispersibility in water, weak visible light response, and unstable and easily-soluble transition metal after being compounded with a transition metal-based semiconductor material. The method comprises the following steps: firstly, preparing a porous graphite phase carbon nitride precursor; secondly, preparing porous graphite phase carbon nitride; thirdly, preparing graphite phase carbon nitride dispersion liquid; fourthly, mixing the transition metal with the porous graphite phase carbon nitride; fifthly, coprecipitation. The method is used for preparing the graphite phase carbon nitride-transition metal based semiconductor composite photocatalytic material based on stable amino coordination.)

1. A preparation method of a graphite phase carbon nitride-transition metal based semiconductor composite photocatalytic material based on stable amino coordination is characterized by comprising the following steps:

firstly, preparing a porous graphite phase carbon nitride precursor:

adding dicyandiamide into deionized water, completely dissolving the dicyandiamide under the water bath heating condition, carrying out hydrothermal reaction for 2-6 h at the temperature of 180-220 ℃, cooling to room temperature, centrifuging to remove the upper layer for dredging, collecting the lower layer solid matter, and finally carrying out freeze drying to obtain a porous graphite phase carbon nitride precursor;

secondly, preparing porous graphite phase carbon nitride:

polymerizing the porous graphite phase carbon nitride precursor for 1 to 4 hours under the conditions of nitrogen atmosphere and temperature of 500 to 600 ℃ to obtain porous graphite phase carbon nitride;

thirdly, preparing graphite phase carbon nitride dispersion liquid:

adding porous graphite phase carbon nitride into deionized water, and performing ultrasonic dispersion to obtain a porous graphite phase carbon nitride dispersion liquid;

fourthly, mixing the transition metal with the porous graphite phase carbon nitride:

adding a transition metal aqueous solution into the porous graphite phase carbon nitride dispersion liquid, and stirring until the transition metal aqueous solution and the porous graphite phase carbon nitride dispersion liquid are uniformly mixed to obtain a turbid liquid;

the mass ratio of the porous graphite phase carbon nitride in the porous graphite phase carbon nitride dispersion liquid to the transition metal ions in the transition metal aqueous solution is 1 (0.2-2);

fifthly, coprecipitation:

dropwise adding the anion solution into the suspension, stirring until the anion solution is uniformly mixed, then centrifugally collecting solid precipitate, and finally washing and drying to obtain the graphite-phase carbon nitride-transition metal-based semiconductor composite photocatalytic material based on stable amino coordination;

the anion in the anion solution is the anion coprecipitated with the transition metal; the quantity ratio of the transition metal ions in the suspension to the anion substances in the anion solution is 1 (1.05-1.60).

2. The preparation method of the graphite-phase carbon nitride-transition metal-based semiconductor composite photocatalytic material based on stable amino coordination according to claim 1, wherein the volume ratio of the mass of dicyandiamide to deionized water in the step one is 1g (5-10) mL.

3. The method for preparing the graphite-phase carbon nitride-transition metal-based semiconductor composite photocatalytic material based on amino coordination stabilization according to claim 1, wherein the graphite-phase carbon nitride-transition metal-based semiconductor composite photocatalytic material based on amino coordination stabilization is completely dissolved in the step one under the water bath heating condition at the temperature of 60 ℃ to 100 ℃.

4. The method for preparing the graphite-phase carbon nitride-transition metal-based semiconductor composite photocatalytic material based on amino coordination stability according to claim 1, wherein the centrifugation in the step one is specifically performed at a rotation speed of 2000rpm to 5000rpm for 5min to 15 min.

5. The method for preparing the graphite-phase carbon nitride-transition metal-based semiconductor composite photocatalytic material based on amino coordination stabilization according to claim 1, wherein the step one of freeze-drying is specifically freezing for 24h to 48h at a temperature of-30 ℃ to-50 ℃.

6. The method for preparing the graphite phase carbon nitride-transition metal based semiconductor composite photocatalytic material based on amino coordination stability as claimed in claim 1, wherein the ultrasonic dispersion in the third step is specifically dispersion for 5min to 30min under the condition that the power is 100 w to 150 w.

7. The method for preparing the graphite-phase carbon nitride-transition metal-based semiconductor composite photocatalytic material based on stable amino coordination according to claim 1, wherein the method comprises the fourth stepThe transition metal ion in the transition metal aqueous solution is Cu²⁺、A^g+Or Zn²⁺(ii) a The concentration of the transition metal in the transition metal aqueous solution in the fourth step is 0.05 mol/L-0.2 mol/L.

8. The method for preparing the graphite-phase carbonitride-transition metal-based semiconductor composite photocatalytic material based on amino coordination stabilization according to claim 1, wherein the anion in the anion solution in the fifth step is S^2-Or Br^-(ii) a And the concentration of the anions in the anion solution in the step five is 0.05 mol/L-0.2 mol/L.

9. The method for preparing the graphite-phase carbon nitride-transition metal-based semiconductor composite photocatalytic material based on amino coordination stability according to claim 1, wherein the centrifugation in the fifth step is specifically centrifugation for 5min to 15min at a rotation speed of 2000rpm to 5000rpm, and the centrifugation is repeated for 2 times to 5 times.

10. The method for preparing the graphite-phase carbon nitride-transition metal-based semiconductor composite photocatalytic material based on amino coordination stabilization according to claim 1, wherein the washing and drying in the fifth step is specifically washing with deionized water, and then vacuum drying at a temperature of 25-60 ℃ for 12-36 h.

Technical Field

The invention belongs to the technical field of photocatalysis.

Background

The content of various refractory organic pollutants such as dyes, medicines (intermediates) and the like in the industrial discharged wastewater is continuously increased, and the serious threat is caused to the environment and the human health. At present, methods such as adsorption, membrane separation, chemical oxidation and the like are applied to the treatment of the wastewater, wherein chemical oxidation reaction is widely concerned because refractory organic matters can be quickly removed by virtue of strong oxidation capacity. Photocatalysis is one of advanced oxidation, the reaction source driving force is sunlight, the degradation process is green, clean and less in pollution, and the photocatalysis has great application potential in the aspect of removing difficultly degraded organic matters.

Graphite-phase carbon nitride is one of the photocatalysts which have been recently developed, and is one of the hot spots of research because of its response to visible light (about 2.7eV) and chemical stability. More importantly, the composition elements of the substance are the most abundant carbon element and oxygen element on the earth, so that the substance becomes a very promising photocatalyst. However, the bulk carbon nitride obtained by direct calcination has the disadvantages of small specific surface area, poor dispersibility in water, weak visible light response (less than 460nm), and the like, and the development and application of the bulk carbon nitride are severely limited. The transition metal-based photocatalytic material and the graphene carbon nitride are added to form the composite semiconductor material, which is one of common ways for improving the photocatalytic performance of graphite-phase carbon nitride at present. The recombination between the two semiconductor materials can fully combine the advantages of the two on light absorption, and generally broaden the light absorption. In addition, the matched energy band relation can promote the transfer of e-and h +, so that the e-and h + are not easy to combine, and the service life is longer. However, the commonly used transition metal semiconductor materials such as AgBr, CdS, ZnO, etc. are unstable and easy to dissolve out heavy metal ions in the using process. The method not only greatly reduces the photocatalytic performance of the composite semiconductor photocatalyst, but also brings non-negligible secondary pollution due to the dissolved heavy metal ions. Therefore, the preparation of the composite photocatalyst of the transition metal-based semiconductor and the graphite-phase carbon nitride semiconductor with high catalytic activity and the improvement of the stability of the transition metal ions have great challenges.

Disclosure of Invention

The invention aims to solve the problems that the graphene carbon nitride prepared by the simple thermal polymerization method has small specific surface area, poor dispersibility in water, weak visible light response, and unstable and easily-soluble transition metal after being compounded with a transition metal-based semiconductor material. Further provides a preparation method of the graphite phase carbon nitride-transition metal based semiconductor composite photocatalytic material based on stable amino coordination.

A preparation method of a graphite phase carbon nitride-transition metal based semiconductor composite photocatalytic material based on stable amino coordination is carried out according to the following steps:

firstly, preparing a porous graphite phase carbon nitride precursor:

adding dicyandiamide into deionized water, completely dissolving the dicyandiamide under the water bath heating condition, carrying out hydrothermal reaction for 2-6 h at the temperature of 180-220 ℃, cooling to room temperature, centrifuging to remove the upper layer for dredging, collecting the lower layer solid matter, and finally carrying out freeze drying to obtain a porous graphite phase carbon nitride precursor;

secondly, preparing porous graphite phase carbon nitride:

polymerizing the porous graphite phase carbon nitride precursor for 1 to 4 hours under the conditions of nitrogen atmosphere and temperature of 500 to 600 ℃ to obtain porous graphite phase carbon nitride;

thirdly, preparing graphite phase carbon nitride dispersion liquid:

adding porous graphite phase carbon nitride into deionized water, and performing ultrasonic dispersion to obtain a porous graphite phase carbon nitride dispersion liquid;

fourthly, mixing the transition metal with the porous graphite phase carbon nitride:

adding a transition metal aqueous solution into the porous graphite phase carbon nitride dispersion liquid, and stirring until the transition metal aqueous solution and the porous graphite phase carbon nitride dispersion liquid are uniformly mixed to obtain a turbid liquid;

the mass ratio of the porous graphite phase carbon nitride in the porous graphite phase carbon nitride dispersion liquid to the transition metal ions in the transition metal aqueous solution is 1 (0.2-2);

fifthly, coprecipitation:

dropwise adding the anion solution into the suspension, stirring until the anion solution is uniformly mixed, then centrifugally collecting solid precipitate, and finally washing and drying to obtain the graphite-phase carbon nitride-transition metal-based semiconductor composite photocatalytic material based on stable amino coordination;

the anion in the anion solution is the anion coprecipitated with the transition metal; the quantity ratio of the transition metal ions in the suspension to the anion substances in the anion solution is 1 (1.05-1.60).

The invention has the beneficial effects that:

1. the specific surface area of the porous graphite phase carbon nitride prepared by the invention is 40m²And the graphene carbon nitride has good dispersibility in water, and the graphite-phase carbon nitride does not need to be subjected to complex stripping operations such as high temperature treatment, strong acid treatment and oxidation again, and can be directly added into water for short-time ultrasonic treatment to obtain the stable graphite-phase carbon nitride dispersion. Greatly simplifying the stripping and dispersing process of the graphene carbon nitride.

2. According to the invention, the transition metal semiconductor material and the porous graphite phase carbon nitride are compounded to form a heterojunction, the two semiconductor materials can be compounded to fully combine the advantages of the two semiconductor materials on light absorption, the light absorption range is widened, the visible light response is as high as 620nm, the transfer of e & lt + & gt and h & lt + & gt is effectively promoted, the compounding of e & lt + & gt and h & lt + & gt is reduced, and the photocatalytic degradation capability of the material is improved.

3. According to the invention, a large number of amino groups on the edge of the porous graphite-phase carbon nitride form coordinate bonds with the transition metal ions, so that the stability of the transition metal ions is improved. Effectively avoids the inactivation of the photocatalytic performance of the composite photocatalytic material, simultaneously reduces the risk of secondary pollutants caused by excessive metal dissolution, and Cd is obtained under the condition of pH 5²⁺The dissolution equilibrium concentration of (A) is only 0.07 mg/L.

4. The invention can obtain different types of transition metal-based semiconductor-graphite phase carbon nitride composite photocatalytic materials by adding different transition metal ions and dripping different anions for coprecipitation, and can control the proportion of the transition metal-based semiconductor and the graphite phase carbon nitride by controlling the addition amount of the transition metal ions.

The invention relates to a preparation method of a graphite phase carbon nitride-transition metal matrix semiconductor composite photocatalytic material based on stable amino coordination.

Drawings

FIG. 1 is a pictorial representation of 10mg of ordinary graphite phase carbon nitride prepared in a comparative experiment and 10mg of porous graphite phase carbon nitride prepared in step two of the example, a being the ordinary graphite phase carbon nitride prepared in the comparative experiment and b being the porous graphite phase carbon nitride prepared in step two of the example;

FIG. 2 is a graph of 20mg of conventional graphite-phase carbon nitride prepared in a comparative experiment and 20mg of porous graphite-phase carbon nitride prepared in the second example step, dispersed in 10mL of water, respectively, and sonicated for 3min, where a is the conventional graphite-phase carbon nitride prepared in the comparative experiment and b is the porous graphite-phase carbon nitride prepared in the second example step;

FIG. 3 is a SEM of plain graphite-phase carbon nitride prepared in a comparative experiment and porous graphite-phase carbon nitride prepared in step two of the example, where a is the plain graphite-phase carbon nitride prepared in the comparative experiment and b is the porous graphite-phase carbon nitride prepared in step two of the example;

FIG. 4 is an XRD pattern of a plain graphite phase carbon nitride prepared in a comparative experiment and a porous graphite phase carbon nitride prepared in the second example step a, a being the plain graphite phase carbon nitride prepared in the comparative experiment and b being the porous graphite phase carbon nitride prepared in the second example step b;

fig. 5 is a nitrogen adsorption-desorption isotherm diagram of the ordinary graphite-phase carbon nitride prepared in the comparative experiment and the porous graphite-phase carbon nitride prepared in the second example step, a being the ordinary graphite-phase carbon nitride prepared in the comparative experiment and b being the porous graphite-phase carbon nitride prepared in the second example step;

FIG. 6 is a graph showing the pore size distribution of the conventional graphite-phase carbon nitride prepared in the comparative experiment and the porous graphite-phase carbon nitride prepared in the second example, where a is the porous graphite-phase carbon nitride prepared in the second example, and b is the conventional graphite-phase carbon nitride prepared in the comparative experiment;

FIG. 7 is a fine spectrum of XPS N1s for porous graphite phase carbon nitride prepared in step two of the example;

FIG. 8 is an SEM image of a graphite-phase carbonitride-transition metal-based semiconductor composite photocatalytic material stabilized based on amino coordination prepared in the first example;

fig. 9 is an element mapping diagram of the graphite-phase carbon nitride-transition metal-based semiconductor composite photocatalytic material based on amino coordination stabilization prepared in the first embodiment, where a is an EDS total distribution diagram, b is a Cd element distribution diagram, C is an S element distribution diagram, d is a C element distribution diagram, and e is an N element distribution diagram;

FIG. 10 is a surface spectrum of a graphite-phase carbonitride-transition metal-based semiconductor composite photocatalytic material stabilized based on amino coordination prepared in example one;

fig. 11 is a visible-ultraviolet diffuse reflection spectrum, wherein 1 is porous graphite phase carbon nitride prepared in the second step of the example, 2 is a graphite phase carbon nitride-transition metal based semiconductor composite photocatalytic material based on amino group coordination stabilization prepared in the first step of the example, and 3 is CdS;

FIG. 12 is a Kubelka-Munk function graph, wherein 1 is porous graphite phase carbon nitride prepared in the second step of the example, 2 is a graphite phase carbon nitride-transition metal based semiconductor composite photocatalytic material based on amino coordination stabilization prepared in the first step of the example, and 3 is CdS;

FIG. 13 is a fluorescence spectrum of a porous graphite-phase carbon nitride prepared in example two, and b a graphite-phase carbon nitride-transition metal-based semiconductor composite photocatalytic material based on amino group coordination stabilization prepared in example one;

FIG. 14 is a tetracycline cyclic degradation test based on the graphite-phase carbonitride-transition metal-based semiconductor composite photocatalytic material stabilized by amino coordination prepared in example one;

FIG. 15 shows XPS Cd3d fine spectra of the amino group coordination-stabilized graphite-phase carbonitride-transition metal-based semiconductor composite photocatalytic material prepared in example one after being undegraded and being cyclically degraded for 5 times, wherein a is undegraded and b is cyclically degraded for 5 times;

fig. 16 is a graph showing the degradation test of different transition metal semiconductor-porous graphite phase carbon nitride composite photocatalytic materials on tetracycline, a is a comparison graph of the degradation test of tetracycline, b is a quasi-first order kinetic linear fit graph corresponding to a, 1 is porous graphite phase carbon nitride prepared in the second step of the example, 2 is CdS/carbon nitride composite prepared in the first example, 3 is AgBr/carbon nitride composite prepared in the third example, 4 is ZnS/carbon nitride composite prepared in the fourth example, and 5 is CuS/carbon nitride composite prepared in the fifth example.

Detailed Description

The first embodiment is as follows: the embodiment is a preparation method of a graphite phase carbon nitride-transition metal matrix semiconductor composite photocatalytic material based on stable amino coordination, which is carried out according to the following steps:

firstly, preparing a porous graphite phase carbon nitride precursor:

adding dicyandiamide into deionized water, completely dissolving the dicyandiamide under the water bath heating condition, carrying out hydrothermal reaction for 2-6 h at the temperature of 180-220 ℃, cooling to room temperature, centrifuging to remove the upper layer for dredging, collecting the lower layer solid matter, and finally carrying out freeze drying to obtain a porous graphite phase carbon nitride precursor;

secondly, preparing porous graphite phase carbon nitride:

polymerizing the porous graphite phase carbon nitride precursor for 1 to 4 hours under the conditions of nitrogen atmosphere and temperature of 500 to 600 ℃ to obtain porous graphite phase carbon nitride;

thirdly, preparing graphite phase carbon nitride dispersion liquid:

adding porous graphite phase carbon nitride into deionized water, and performing ultrasonic dispersion to obtain a porous graphite phase carbon nitride dispersion liquid;

fourthly, mixing the transition metal with the porous graphite phase carbon nitride:

adding a transition metal aqueous solution into the porous graphite phase carbon nitride dispersion liquid, and stirring until the transition metal aqueous solution and the porous graphite phase carbon nitride dispersion liquid are uniformly mixed to obtain a turbid liquid;

the mass ratio of the porous graphite phase carbon nitride in the porous graphite phase carbon nitride dispersion liquid to the transition metal ions in the transition metal aqueous solution is 1 (0.2-2);

fifthly, coprecipitation:

dropwise adding the anion solution into the suspension, stirring until the anion solution is uniformly mixed, then centrifugally collecting solid precipitate, and finally washing and drying to obtain the graphite-phase carbon nitride-transition metal-based semiconductor composite photocatalytic material based on stable amino coordination;

the anion in the anion solution is the anion coprecipitated with the transition metal; the quantity ratio of the transition metal ions in the suspension to the anion substances in the anion solution is 1 (1.05-1.60).

In the embodiment, the ratio of the graphite-phase carbon nitride to the multi-metal semiconductor in the composite photocatalytic material is controlled by controlling the addition amount of the transition metal.

The preparation method comprises the steps of preparing porous graphite phase carbon nitride by dicyandiamide pretreatment, fixing metal ions by coordination of amino groups at the edges of gaps of the porous graphite phase carbon nitride and transition metal ions, converting the transition metal ions into a transition metal-based semiconductor material by ion coprecipitation, and finally drying in vacuum to obtain the graphite phase carbon nitride-transition metal semiconductor composite photocatalytic material. The coordination bonds are formed between a large number of amino functional groups on the edges of the gaps on the porous graphite phase carbon nitride sheet layer and the transition metal-based semiconductor material, so that the transfer of e-and h + between the two semiconductor materials is facilitated, the photocatalytic activity of the composite semiconductor material is improved, and the stability of the transition metal is also improved.

The beneficial effects of the embodiment are as follows:

1. the specific surface area of the porous graphite phase carbon nitride prepared by the embodimentIs 40m²And the graphene carbon nitride has good dispersibility in water, and the graphite-phase carbon nitride does not need to be subjected to complex stripping operations such as high temperature treatment, strong acid treatment and oxidation again, and can be directly added into water for short-time ultrasonic treatment to obtain the stable graphite-phase carbon nitride dispersion. Greatly simplifying the stripping and dispersing process of the graphene carbon nitride.

2. According to the embodiment, the transition metal semiconductor material and the porous graphite phase carbon nitride are compounded to form a heterojunction, the two semiconductor materials can be compounded to fully combine the advantages of the two semiconductor materials on light absorption, the light absorption range is widened, the visible light response is as high as 620nm, the transfer of e & lt + & gt and h & lt + & gt is effectively promoted, the compounding of e & lt + & gt and h & lt + & gt is reduced, and the photocatalytic degradation capability of the materials is improved.

3. In the embodiment, a large amount of amino groups on the edge of the porous graphite-phase carbon nitride form coordination bonds with transition metal ions, so that the stability of the transition metal ions is improved. Effectively avoids the inactivation of the photocatalytic performance of the composite photocatalytic material, simultaneously reduces the risk of secondary pollutants caused by excessive metal dissolution, and Cd is obtained under the condition of pH 5²⁺The dissolution equilibrium concentration of (A) is only 0.07 mg/L.

4. In the embodiment, different transition metal ions can be added, different anions are added dropwise for coprecipitation to obtain different transition metal-based semiconductor-graphite phase carbon nitride composite photocatalytic materials, and the ratio of the transition metal-based semiconductor to the graphite phase carbon nitride can be controlled by controlling the addition amount of the transition metal ions.

The second embodiment is as follows: the first difference between the present embodiment and the specific embodiment is: the volume ratio of the mass of the dicyandiamide to the deionized water in the step one is 1g (5-10) mL. The rest is the same as the first embodiment.

The third concrete implementation mode: this embodiment is different from the first or second embodiment in that: in the first step, the raw materials are completely dissolved under the water bath heating condition with the temperature of 60-100 ℃. The other is the same as in the first or second embodiment.

The fourth concrete implementation mode: the difference between this embodiment mode and one of the first to third embodiment modes is: the centrifugation in the step one is specifically centrifugation for 5-15 min under the condition that the rotating speed is 2000-5000 rpm. The others are the same as the first to third embodiments.

The fifth concrete implementation mode: the difference between this embodiment and one of the first to fourth embodiments is: the freeze drying in the step one is to freeze for 24-48 h at-30 to-50 ℃. The rest is the same as the first to fourth embodiments.

The sixth specific implementation mode: the difference between this embodiment and one of the first to fifth embodiments is: the ultrasonic dispersion in the third step is specifically dispersion for 5-30 min under the condition that the power is 100-150 watts. The rest is the same as the first to fifth embodiments.

The seventh embodiment: the difference between this embodiment and one of the first to sixth embodiments is: the transition metal ion in the transition metal aqueous solution in the fourth step is Cu²⁺、A^g+Or Zn²⁺(ii) a The concentration of the transition metal in the transition metal aqueous solution in the fourth step is 0.05 mol/L-0.2 mol/L. The others are the same as the first to sixth embodiments.

The specific implementation mode is eight: the present embodiment differs from one of the first to seventh embodiments in that: the anion in the anion solution in the step five is S^2-Or Br^-(ii) a And the concentration of the anions in the anion solution in the step five is 0.05 mol/L-0.2 mol/L. The rest is the same as the first to seventh embodiments.

The specific implementation method nine: the present embodiment differs from the first to eighth embodiments in that: and the centrifugation in the step five is specifically to centrifuge for 5-15 min under the condition that the rotating speed is 2000-5000 rpm, and repeatedly centrifuge for 2-5 times. The other points are the same as those in the first to eighth embodiments.

The detailed implementation mode is ten: the present embodiment differs from one of the first to ninth embodiments in that: and the washing and drying in the step five specifically comprises the steps of washing with deionized water, and then drying for 12-36 h in vacuum at the temperature of 25-60 ℃. The other points are the same as those in the first to ninth embodiments.

The following examples were used to demonstrate the beneficial effects of the present invention:

the first embodiment is as follows:

a preparation method of a graphite phase carbon nitride-transition metal based semiconductor composite photocatalytic material based on stable amino coordination is carried out according to the following steps:

firstly, preparing a porous graphite phase carbon nitride precursor:

adding 20g of dicyandiamide into 160mL of deionized water, completely dissolving the dicyandiamide under the water bath heating condition, transferring the mixture into an autoclave, carrying out hydrothermal reaction for 4 hours at the temperature of 200 ℃, cooling the mixture to room temperature, centrifuging the mixture to remove upper layer sludge, collecting lower layer solid matter, and finally carrying out freeze drying to obtain a porous graphite phase carbon nitride precursor;

secondly, preparing porous graphite phase carbon nitride:

pouring the porous graphite phase carbon nitride precursor into a quartz square boat, covering a quartz glass cover, placing the quartz square boat in a tubular electric furnace, and polymerizing the porous graphite phase carbon nitride precursor for 2 hours under the conditions of nitrogen atmosphere and 550 ℃ to obtain porous graphite phase carbon nitride;

thirdly, preparing a graphite phase carbon nitride dispersion liquid:

adding 50mg of porous graphite phase carbon nitride into 100mL of deionized water, and performing ultrasonic dispersion to obtain a porous graphite phase carbon nitride dispersion liquid;

fourthly, mixing the transition metal with the porous graphite phase carbon nitride:

adding 3.46mL of 0.1mol/L transition metal aqueous solution into the porous graphite phase carbon nitride dispersion, and stirring for 1h at a stirring speed of 200rpm to obtain a suspension;

fifthly, coprecipitation:

dropwise adding 4mL of 0.1mol/L anion solution into the suspension, stirring for 3h at the stirring speed of 200rpm, then centrifugally collecting solid precipitate, and finally washing and drying to obtain the graphite-phase carbon nitride-transition metal-based semiconductor composite photocatalytic material based on stable amino coordination; abbreviated as CdS/carbon nitride composite.

The anion in the anion solution is the anion co-precipitated with the transition metal.

In the first step, the mixture is heated in a water bath at the temperature of 80 ℃ until the mixture is completely dissolved.

The centrifugation in the step one is specifically centrifugation for 10min under the condition that the rotating speed is 3000 rpm.

The step one, namely freezing for 24 hours at the temperature of-40 ℃.

The ultrasonic dispersion described in step three is specifically dispersion for 20min under the condition of 150 watts.

The transition metal in the transition metal aqueous solution in the fourth step is Cd (NO)₃)₂。

In the fifth step, the anion-containing substance in the anion solution is Na₂S。

And the centrifugation in the step five is specifically centrifugation for 10min under the condition that the rotating speed is 5000r/min, and the centrifugation is repeated for 3 times.

And the washing and drying in the step five are specifically washing by using deionized water, and then vacuum drying for 12 hours at the temperature of 40 ℃.

Example two: the difference between the present embodiment and the first embodiment is: in the fourth step, 6.9mL of transition metal aqueous solution with the concentration of 0.1mol/L is added into the porous graphite phase carbon nitride dispersion liquid; in the fifth step, 8.3mL of anion solution with the concentration of 0.1mol/L is dripped into the suspension; abbreviated as 2 CdS/carbon nitride composite. The rest is the same as the first embodiment.

Example three: the difference between the present embodiment and the first embodiment is: the transition metal in the transition metal aqueous solution in the fourth step is AgNO₃. The anion-containing substance in the anion solution in the step five is KBr; abbreviated to AgBr/carbon nitride composite. The rest is the same as the first embodiment.

Example four: the difference between the present embodiment and the first embodiment is: the transition metal in the transition metal aqueous solution in the fourth step is ZnCl₂. In the fifth step, the anion-containing substance in the anion solution is Na₂S; abbreviated as ZnS/nitrideA carbon composite material. The rest is the same as the first embodiment.

Example five: the difference between the present embodiment and the first embodiment is: the transition metal in the transition metal aqueous solution in the fourth step is CuCl₂. In the fifth step, the anion-containing substance in the anion solution is Na₂S; abbreviated as CuS/carbon nitride composite. The rest is the same as the first embodiment.

Comparative experiment: 5g dicyandiamide was poured into a quartz boat, covered with a quartz glass lid, and N was introduced₂And directly polymerizing for 2 hours at the temperature of 550 ℃ to obtain the common graphite phase carbon nitride.

FIG. 1 is a pictorial representation of 10mg of ordinary graphite phase carbon nitride prepared in a comparative experiment and 10mg of porous graphite phase carbon nitride prepared in step two of the example, a being the ordinary graphite phase carbon nitride prepared in the comparative experiment and b being the porous graphite phase carbon nitride prepared in step two of the example; as can be seen, the porous graphite phase carbon nitride is darker in color and much higher in volume than ordinary carbon nitride in equivalent mass.

FIG. 2 is a graph of 20mg of conventional graphite-phase carbon nitride prepared in a comparative experiment and 20mg of porous graphite-phase carbon nitride prepared in the second example step, dispersed in 10mL of water, respectively, and sonicated for 3min, where a is the conventional graphite-phase carbon nitride prepared in the comparative experiment and b is the porous graphite-phase carbon nitride prepared in the second example step; as can be seen from the figure, most of the particles are still precipitated at the bottom of the water after the common graphite phase carbon nitride is subjected to ultrasonic treatment, and the porous graphite phase carbon nitride is uniformly dispersed in the water after the ultrasonic treatment.

FIG. 3 is a SEM of plain graphite-phase carbon nitride prepared in a comparative experiment and porous graphite-phase carbon nitride prepared in step two of the example, where a is the plain graphite-phase carbon nitride prepared in the comparative experiment and b is the porous graphite-phase carbon nitride prepared in step two of the example; as can be seen from the figure, the common graphite phase carbon nitride is blocky and has larger particles; the porous graphite phase carbon nitride is in a porous fluffy form.

FIG. 4 is an XRD pattern of a plain graphite phase carbon nitride prepared in a comparative experiment and a porous graphite phase carbon nitride prepared in the second example step a, a being the plain graphite phase carbon nitride prepared in the comparative experiment and b being the porous graphite phase carbon nitride prepared in the second example step b; as can be seen from the figure, the porous graphite phase carbon nitride has a low crystallinity.

Fig. 5 is a nitrogen adsorption-desorption isotherm diagram of the ordinary graphite-phase carbon nitride prepared in the comparative experiment and the porous graphite-phase carbon nitride prepared in the second example step, a being the ordinary graphite-phase carbon nitride prepared in the comparative experiment and b being the porous graphite-phase carbon nitride prepared in the second example step; FIG. 6 is a graph showing the pore size distribution of the conventional graphite-phase carbon nitride prepared in the comparative experiment and the porous graphite-phase carbon nitride prepared in the second example, where a is the porous graphite-phase carbon nitride prepared in the second example, and b is the conventional graphite-phase carbon nitride prepared in the comparative experiment; as can be seen from the figure, the specific surface area of the porous graphite phase carbon nitride is 40m²(g) is 9m of common graphite phase carbon nitride²3.4 times of the amount of the acid anhydride in g. The average pore diameter of the porous graphite phase carbon nitride is 20nm, which is higher than that of the common graphite phase carbon nitride by 5 nm.

FIG. 7 is a fine spectrum of XPS N1s for porous graphite phase carbon nitride prepared in step two of the example; from XPS N1s fine spectra, a peak at 398.2eV corresponds to a nitrogen atom (C ═ N-C) of a 3-s triazine unit, a peak at 404.5eV is caused by pi-pi vibration of graphite-phase carbon nitride, and 400.0eV corresponds to nitrogen in an amino group (N-H), so that abundant amino groups can form coordinate bonds with transition metal ions, and the stability of the transition metal in the composite material is improved.

FIG. 8 is an SEM image of a graphite-phase carbonitride-transition metal-based semiconductor composite photocatalytic material stabilized based on amino coordination prepared in the first example; as can be seen from the figure, compared with porous graphite phase carbon nitride, the CdS semiconductor particles in the CdS and porous graphite phase carbon nitride composite photocatalytic material in the ratio of 1:1 are filled in the gaps of the porous carbon nitride.

Fig. 9 is an element mapping diagram of the graphite-phase carbon nitride-transition metal-based semiconductor composite photocatalytic material based on amino coordination stabilization prepared in the first embodiment, where a is an EDS total distribution diagram, b is a Cd element distribution diagram, C is an S element distribution diagram, d is a C element distribution diagram, and e is an N element distribution diagram; FIG. 10 is a surface spectrum of a graphite-phase carbonitride-transition metal-based semiconductor composite photocatalytic material stabilized based on amino coordination prepared in example one; as can be seen from the figure, 1:1 CdS and CdS in the porous graphite-phase carbon nitride composite photocatalytic material are uniformly distributed, the atomic ratio distribution of the four elements of C, N, Cd and S is 51.4%, 28.9%, 10.5% and 9.2%, and the CdS are matched with the design idea after being converted into mass.

Fig. 11 is a visible-ultraviolet diffuse reflection spectrum, wherein 1 is porous graphite phase carbon nitride prepared in the second step of the example, 2 is a graphite phase carbon nitride-transition metal based semiconductor composite photocatalytic material based on amino group coordination stabilization prepared in the first step of the example, and 3 is CdS; FIG. 12 is a Kubelka-Munk function graph, wherein 1 is porous graphite phase carbon nitride prepared in the second step of the example, 2 is a graphite phase carbon nitride-transition metal based semiconductor composite photocatalytic material based on amino coordination stabilization prepared in the first step of the example, and 3 is CdS; FIG. 13 is a fluorescence spectrum of a porous graphite-phase carbon nitride prepared in example two, and b a graphite-phase carbon nitride-transition metal-based semiconductor composite photocatalytic material based on amino group coordination stabilization prepared in example one; as can be seen from the figure, the single material and the composite material both have good response to visible light, the absorption edge of the porous graphite phase carbon nitride can reach 525nm, the absorption edge of the CdS can reach 600nm, and the light absorption of the CdS/carbon nitride composite material is red-shifted to be as high as 620nm compared with the two materials because the combination of the two materials enhances the light absorption. The fluorescence intensity of CdS/carbon nitride is obviously lower than that of porous carbon nitride, which shows that the photo-induced carrier recombination condition in the CdS/carbon nitride composite material is weaker than that of single porous carbon nitride, and the photo-induced carrier migration is facilitated due to the fit of energy bands between CdS and porous carbon nitride, so that the degradation effect of the CdS/carbon nitride composite material on pollutants is better.

TABLE 1 Cd ion leaching concentration of cadmium sulfide under different pH conditions and the graphite-phase carbon nitride-transition metal-based semiconductor composite photocatalytic material based on amino coordination stabilization prepared in example one

pH value	Material	Cd dissolution concentration (mg/L)
			3	CdS	10.35
5	CdS	2.21
			7	CdS	0.14
9	CdS	——
			3	CdS/carbon nitride	0.42
5	CdS/carbon nitride	0.07
			7	CdS/carbon nitride	——
9	CdS/carbon nitride	——

As shown in the table, in the cadmium sulfide-porous carbon nitride composite material, the edge amino group and Cd are bonded through the graphite phase carbon nitride²⁺Form coordinate bond and obviously reduce heavy metal Cd²⁺And (4) dissolving out. Cd at pH 5²⁺The dissolution equilibrium concentration of the compound is reduced from 2.21mg/L to 0.07mg/L, which is reduced by 97 percent.

FIG. 14 is a tetracycline cyclic degradation test based on the graphite-phase carbonitride-transition metal-based semiconductor composite photocatalytic material stabilized by amino coordination prepared in example one; as can be seen from the figure, the cadmium sulfide-porous carbon nitride composite photocatalytic material has high stability for photocatalytic degradation of tetracycline, and after being recycled for 5 times, the removal rate of the tetracycline is slightly reduced from 81.5% to 73.4%.

FIG. 15 shows XPS Cd3d fine spectra of the amino group coordination-stabilized graphite-phase carbonitride-transition metal-based semiconductor composite photocatalytic material prepared in example one after being undegraded and being cyclically degraded for 5 times, wherein a is undegraded and b is cyclically degraded for 5 times; as can be seen from the figure, Cd before and after cyclic degradation²⁺The position and the strength of the peak are not obviously different, which indicates that the valence state of Cd is not essentially changed in the use process, and the chemical property is stable.

Fig. 16 is a graph showing the degradation test of different transition metal semiconductor-porous graphite phase carbon nitride composite photocatalytic materials on tetracycline, a is a comparison graph of the degradation test of tetracycline, b is a quasi-first order kinetic linear fit graph corresponding to a, 1 is porous graphite phase carbon nitride prepared in a second step of the example, 2 is CdS/carbon nitride composite prepared in the first example, 3 is AgBr/carbon nitride composite prepared in the third example, 4 is ZnS/carbon nitride composite prepared in the fourth example, and 5 is CuS/carbon nitride composite prepared in the fifth example; it can be seen from the figure that the photocatalytic degradation capability of the transition metal semiconductor is significantly increased compared to that of the porous graphite phase carbon nitride after the transition metal semiconductor is compounded with the porous graphite phase carbon nitride. After 120min of illumination, the degradation rates of the CdS/carbon nitride composite material (line 2), the CuS/carbon nitride composite material (line 5), the AgBr/carbon nitride composite material (line 3), the ZnS/carbon nitride composite material (line 4) and tetracycline are 84.51%, 71.69%, 63.31% and 40.97% respectively, which are all higher than 34.09% of that of the single graphite phase carbon nitride.