CN113413921B - ZIF-8 type composite photocatalyst and preparation method thereof - Google Patents

ZIF-8 type composite photocatalyst and preparation method thereof Download PDF

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CN113413921B
CN113413921B CN202110870968.XA CN202110870968A CN113413921B CN 113413921 B CN113413921 B CN 113413921B CN 202110870968 A CN202110870968 A CN 202110870968A CN 113413921 B CN113413921 B CN 113413921B
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cqd
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composite photocatalyst
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CN113413921A (en
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强涛涛
王少婷
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Shaanxi University of Science and Technology
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    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/16—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes
    • B01J31/18—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes containing nitrogen, phosphorus, arsenic or antimony as complexing atoms, e.g. in pyridine ligands, or in resonance therewith, e.g. in isocyanide ligands C=N-R or as complexed central atoms
    • B01J31/1805—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes containing nitrogen, phosphorus, arsenic or antimony as complexing atoms, e.g. in pyridine ligands, or in resonance therewith, e.g. in isocyanide ligands C=N-R or as complexed central atoms the ligands containing nitrogen
    • B01J31/181—Cyclic ligands, including e.g. non-condensed polycyclic ligands, comprising at least one complexing nitrogen atom as ring member, e.g. pyridine
    • B01J31/1815—Cyclic ligands, including e.g. non-condensed polycyclic ligands, comprising at least one complexing nitrogen atom as ring member, e.g. pyridine with more than one complexing nitrogen atom, e.g. bipyridyl, 2-aminopyridine
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    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/26—Catalysts comprising hydrides, coordination complexes or organic compounds containing in addition, inorganic metal compounds not provided for in groups B01J31/02 - B01J31/24
    • B01J31/28—Catalysts comprising hydrides, coordination complexes or organic compounds containing in addition, inorganic metal compounds not provided for in groups B01J31/02 - B01J31/24 of the platinum group metals, iron group metals or copper
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    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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    • C02F1/00—Treatment of water, waste water, or sewage
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    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B01J2531/20—Complexes comprising metals of Group II (IIA or IIB) as the central metal
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    • C02F2101/10—Inorganic compounds
    • C02F2101/20—Heavy metals or heavy metal compounds
    • C02F2101/22—Chromium or chromium compounds, e.g. chromates
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2305/00—Use of specific compounds during water treatment
    • C02F2305/10—Photocatalysts
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Abstract

The invention discloses a ZIF-8 type composite photocatalyst and a preparation method thereof, belonging to the technical field of material science. The preparation method comprises the steps of using a biomass material as a raw material, firstly preparing biomass N-CQD by a hydrothermal method, then preparing the biomass N-CQD and a metal organic framework material ZIF-8 into N-CQD/ZIF-8 by an in-situ synthesis method, and finally preparing Cu by a reduction precipitation method 2 O is introduced into N-CQD/ZIF-8 to prepare the ZIF-8 type composite photocatalyst. The ZIF-8 type composite photocatalyst prepared by the preparation method effectively improves the stability of the photocatalytic performance of the existing ZIF-8 type composite photocatalyst.

Description

ZIF-8 type composite photocatalyst and preparation method thereof
Technical Field
The invention belongs to the technical field of material science, and relates to a ZIF-8 type composite photocatalyst and a preparation method thereof.
Background
Hexavalent chromium (Cr (VI)) generated in industrial wastewater of leather industry, textile production, printing and dyeing and the like is mainly chromate (-CrO) 4 ) And dichromate (-Cr) 2 O 7 ) In the form of a "triple effect", inhalation by humans can be carcinogenic, difficult to biodegrade and can cause serious environmental pollution.
The technology for semiconductor photocatalytic reduction of Cr (VI) under the irradiation of visible light not only has the advantages of environmental protection, low energy consumption, high reaction efficiency, difficult generation of secondary pollution and the like, but also has obvious advantages in the degradation aspect of other organic pollutants. Therefore, the semiconductor photocatalytic reduction technology of Cr (VI) is widely considered as a promising treatment method of heavy metal chromium ions.
Among many catalysts, metal organic framework Materials (MOFs) are porous materials formed by self-assembly of metal ions and organic ligands, and are widely applied to the field of photocatalysis due to high specific surface area, tailorable structure, abundant catalytic active sites and the like, but most of MOFs still have the problems of poor stability, rapid recombination of photo-generated electron-hole pairs and the like.
Nitrogen-doped carbon quantum dots (N-CQD) serving as a novel fluorescent carbon nano material have the excellent performances of environmental protection, easiness in modification, low preparation cost and the like, and have the unique advantage of high photoproduction electron transfer rate, and the amino doping can greatly improve the utilization efficiency of visible light, so that the N-CQD is used for improving the photocatalytic performance of MOFs, but researches show that the stability of the N-CQD/ZIF-8 still needs to be improved.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide the ZIF-8 type composite photocatalyst and the preparation method thereof, and the stability of the photocatalytic performance of the ZIF-8 type composite photocatalyst is improved.
In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:
the invention discloses a preparation method of a ZIF-8 type composite photocatalyst, which utilizes a biomass material as a raw material, firstly adopts a hydrothermal method to prepare biomass N-CQD, then adopts an in-situ synthesis method to prepare the biomass N-CQD and a metal organic framework material ZIF-8 into N-CQD/ZIF-8, and finally adopts a reductive precipitation method to prepare Cu 2 O is introduced into the N-CQD/ZIF-8 to prepare the ZIF-8 type composite photocatalyst.
Preferably, the method specifically comprises the following steps:
crushing and drying a biomass material to obtain biomass powder, and carrying out hydrothermal reaction on the biomass powder and urea to obtain biomass N-CQD; respectively and uniformly dispersing the obtained biomass N-CQD in two solutions to respectively obtain a solution A and a solution B, and respectively dissolving a metal zinc-based precursor and an imidazole ligand in the solution A or the solution B to obtain a reaction solution A and a reaction solution B; reacting the obtained reaction liquid A and the reaction liquid B based on an in-situ synthesis method to obtain a solid precipitate, and purifying and drying the obtained solid precipitate to obtain N-CQD/ZIF-8; dissolving a metal copper salt and N-CQD/ZIF-8 in water to prepare a metal copper salt/N-CQD/ZIF-8 solution; dissolving another copper salt with equal mass in water to prepare a copper salt solution; and (2) dripping the obtained metal copper salt solution into the obtained metal copper salt/N-CQD/ZIF-8 solution, continuously adding a sulfonate dispersant, an alkaline substance and a reducing agent to perform a reduction precipitation reaction at normal temperature, centrifuging after the reaction is finished to obtain a solid product, washing and drying the obtained solid product to obtain the ZIF-8 type composite photocatalyst.
Further preferably, the mass ratio of the biomass powder to the urea is 1g (0.1-0.4 g);
when preparing solution A or solution B, the solution is CH 3 The dosage ratio of the biomass N-CQD to the solvent in the OH solution is 0.001-0.003g.
More preferably, the mass ratio of the biomass N-CQD, the metal zinc-based precursor and the imidazole ligand is 0.001-0.003g.
Further preferably, the metallic copper salt is cupric chloride dihydrate or cuprous sulfate;
the sulfonate dispersant is sodium dodecyl benzene sulfonate, alpha-olefin sulfonate or 2-hydroxy ethyl sodium sulfonate.
Further preferably, the alkaline substance is NaOH or KOH;
the reducing agent is ascorbic acid or glucose.
Further preferably, when preparing the solution of the metal copper salt/N-CQD/ZIF-8, the mass ratio of the metal copper salt to the N-CQD/ZIF-8 is 0.1-0.2g;
the feeding ratio of the metallic copper salt to the sulfonate dispersant, the alkaline substance to the reducing agent is 0.1-0.2g.
Preferably, the reaction temperature of the hydrothermal reaction is 100-200 ℃, and the reaction time is 12-24 h;
the reaction temperature of the in-situ synthesis method is 10-35 ℃;
the reaction temperature of the reduction precipitation method is 10-35 ℃.
Preferably, the biomass material is walnut shells, chestnut shells or mangosteen shells.
The invention discloses a ZIF-8 type composite photocatalyst prepared by adopting the preparation method.
Compared with the prior art, the invention has the following beneficial effects:
the invention discloses a preparation method of a ZIF-8 type composite photocatalyst, which introduces N-CQD and Cu 2 The heterostructure constructed by O promotes the qualitative movement of a photon-generated carrier, inhibits the rapid recombination of a photon-generated electron-hole pair, effectively improves the visible light absorption capacity of the ZIF-8, and combines the advantages of designability and controllability of a metal organic framework material ZIF-8The preparation method has the advantages of short process flow, low energy consumption and cheap and easily-obtained raw materials, can improve the photocatalysis of MOFs, and effectively solves the problem of unstable photocatalysis performance of the conventional ZIF-8 composite photocatalyst.
The invention also discloses a ZIF-8 type composite photocatalyst prepared by the preparation method, which is prepared by adding Cu 2 O is introduced into N-CQD/ZIF-8 to prepare three-dimensional Cu 2 O/N-CQD/ZIF-8 composite photocatalyst prepared by using Cu 2 O as a relatively stable P-type semiconductor, in combination with N-CQD and Cu 2 And O, the photoresponse range of the ZIF-8 is effectively widened, and the defects of unstable N-CQD/ZIF-8 photocatalytic performance and the like are effectively relieved. In the specific embodiment of the invention, related experiments show that hexavalent chromium (Cr (VI)) is used as a degradation target product of the ZIF-8 composite photocatalyst, and the photocatalytic performance of the hexavalent chromium (Cr (VI)) is remarkably improved.
Drawings
FIG. 1 is an infrared spectrum of a ZIF-8 type composite photocatalyst in example 1;
FIG. 2 is a chart showing an ultraviolet-visible diffuse reflectance spectrum of the ZIF-8 type composite photocatalyst of example 1;
FIG. 3 is a fluorescence spectrum of a ZIF-8 type composite photocatalyst in example 1;
FIG. 4 is a graph showing the comparison of the performances of the ZIF-8 type composite photocatalyst, the N-CQD/ZIF-8 composite material and ZIF-8 photocatalytic reduction of Cr (VI) in example 1.
Detailed Description
In order to make those skilled in the art better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, shall fall within the protection scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
The invention discloses a preparation method of a ZIF-8 type composite photocatalyst, which is prepared from N-CQD, a metal organic framework material ZIF-8 and a P type semiconductor Cu 2 And (C) O. By introducing N-CQD and Cu 2 And O, the photoresponse range of the ZIF-8 is effectively widened, and the photocatalytic performance of the ZIF-8 is obviously improved.
The method specifically comprises the following steps:
the method comprises the following steps: preparation of biomass nitrogen-doped carbon quantum dots (N-CQD)
And (3) placing the waste biomass material in an oven for drying, beating the waste biomass material into small blocks, crushing the small blocks by using a crusher, placing the small blocks in a sample bag for drying for later use, and obtaining biomass powder. The method comprises the steps of taking biomass powder and urea as raw materials, carrying out hydrothermal reaction for 12-24 h at the reaction temperature of 100-200 ℃ to obtain nitrogen-doped carbon quantum dots (N-CQD), namely the biomass N-CQD. Wherein the mass ratio of the biomass powder to the urea is 1g (0.1-0.4 g); the biomass material is walnut shell, chestnut shell or mangosteen shell.
Preferably, the reaction conditions of the biomass nitrogen-doped carbon quantum dots (N-CQD) are as follows: m (walnut shells): m (urea) =1g, temperature is 180 ℃, reaction time is 18h.
Preferably, the reaction conditions of the biomass nitrogen-doped carbon quantum dots (N-CQD) are as follows: m (chestnut shell): m (urea) =1g, temperature 150 ℃, reaction time 16h.
Preferably, the reaction conditions of the biomass nitrogen-doped carbon quantum dots (N-CQD) are as follows: m (mangosteen shell) =: m (urea) =1g, temperature 130 ℃, reaction time 24h.
Step two: preparation of nitrogen-doped carbon quantum dot (N-CQD)/metal organic framework material ZIF-8
Respectively dissolving 0.001-0.003 g of biomass N-CQD in 200-300 mL of methanol (CH) 3 OH) solution, marking as solution A and solution B, after completely dissolving by ultrasonic, respectively dissolving 2.5-5 g of metal zinc-based precursor and 4.1g of imidazole ligand in the solution A and the solution B to obtain reaction liquid A and reaction liquid B, and continuously reacting the obtained reaction liquid A and reaction liquid B for 30min at room temperature (10-35 ℃) by adopting an in-situ synthesis method to obtain solid precipitate; purifying and drying the obtained solid precipitate to obtain N-CQD/ZIF-8. Wherein the zinc-based precursor is zinc nitrate hexahydrate ((Zn (NO) 3 ) 2 ·6H 2 O), and the imidazole ligand is 2-methylimidazole. The operation of purifying the solid precipitate comprises: the obtained solid precipitate is treated with CH at the temperature of between 20 and 35 DEG C 3 Soaking in OH solution for 12-24 hr.
Step three: cuprous oxide (Cu) 2 Preparation of O)/nitrogen-doped carbon quantum dot (N-CQD)/metal organic framework material ZIF-8
Taking a metal copper salt and N-CQD/ZIF-8 as raw materials, wherein 0.1-0.2 g of the metal copper salt and 0.5-1 g N-CQD/ZIF-8 are dissolved in 100mL of water to prepare a metal copper salt/N-CQD/ZIF-8 solution, stirring for 30min at normal temperature, dissolving the metal copper salt with the same mass (0.1-0.2 g) in 100mL of water to prepare a metal copper salt solution, fully stirring, dropwise adding the 1-5 mL of the metal copper salt solution, sequentially adding a sulfonate dispersant and an alkaline substance, stirring for 30min at 10-35 ℃, adding a reducing agent, continuously stirring for 1h at 10-35 ℃ for reduction precipitation reaction, centrifugally washing, and drying in a vacuum drying box to obtain Cu 2 The O/N-CQD/ZIF-8 composite photocatalyst is the ZIF-8 composite photocatalyst. The copper salt in the third step is copper chloride dihydrate (CuCl) 2 ·2H 2 O) or cuprous sulphate (Cu) 2 SO 4 ) One of (1); the sulfonate dispersant is Sodium Dodecyl Benzene Sulfonate (SDBS), alpha-olefin sulfonate (AOS) or sodium 2-hydroxyethyl sulfonate (SHES)One of (a) or (b); the alkaline substance is one of NaOH or KOH; the reducing agent is one of ascorbic acid or glucose. Wherein; the drying temperature is 60-80 ℃; the drying time is 10-20 h.
The invention will be further illustrated with reference to specific examples:
example 1
The method comprises the following steps: preparation of biomass nitrogen-doped carbon quantum dots (N-CQD)
The method comprises the steps of placing the walnut shells made of the waste biomass materials into an oven, drying, beating into small blocks, crushing by using a crusher, placing in a sample bag, and drying for later use. Weighing 1.0g of walnut shell and 0.2g of urea, and fully dissolving the walnut shell and the urea in 50mL of deionized water and uniformly stirring. And continuously carrying out hydrothermal reaction at 180 ℃ for 18h, carrying out purification operations such as centrifugation and dialysis, and carrying out freeze drying to obtain the purified biomass N-CQD.
Step two: preparation of nitrogen-doped carbon quantum dot (N-CQD)/metal organic framework material ZIF-8
Respectively weighing 0.0015g of biomass N-CQD with equal mass, and respectively dissolving in 300mL of CH 3 OH and 250mL CH 3 In the OH solution, marked as solution A and solution B, after being subjected to ultrasonic treatment for 30min, zinc nitrate hexahydrate ((Zn (NO) 3 ) 2 ·6H 2 O) and 2-methylimidazole in the mass ratio of 3.7g 3 OH solution is soaked for 24 hours) and dried to obtain the N-CQD/ZIF-8.
Step three: cuprous oxide (Cu) 2 Preparation of O)/nitrogen-doped carbon quantum dot (N-CQD)/metal organic framework material ZIF-8
0.17g of CuCl was weighed 2 ·2H 2 Dissolving O and 0.5g N-CQD/ZIF-8 catalyst in 100mL water, stirring at room temperature for 30min, and dropwise adding CuCl 2 ·2H 2 O solution (0.17 g CuCl) 2 ·2H 2 Dissolving O in 100mL of water), sequentially adding 1g of SDBS and 0.8g of NaOH, stirring at normal temperature for 30min, then adding 0.8g of ascorbic acid, stirring at 35 ℃ for 1h, centrifuging, washing, and drying in a vacuum drying oven at 60 ℃ for 12h to obtain Cu 2 O/N-CQD/ZIF-8 ternary composite photocatalyst, namely ZIF-8 type composite photocatalyst.
Example 2
The method comprises the following steps: preparation of biomass nitrogen-doped carbon quantum dots (N-CQD)
The method comprises the steps of placing the walnut shells made of the waste biomass materials into an oven, drying, beating into small blocks, crushing by using a crusher, placing in a sample bag, and drying for later use. Weighing 1.0g of walnut shell and 0.2g of urea, and fully dissolving the walnut shell and the urea in 50mL of deionized water and uniformly stirring. And continuously carrying out hydrothermal reaction at 180 ℃ for 18h, carrying out purification operations such as centrifugation and dialysis, and carrying out freeze drying to obtain the purified N-CQD.
Step two: preparation of nitrogen-doped carbon quantum dot (N-CQD)/metal organic framework material ZIF-8
Respectively weighing 0.0015g of biomass N-CQD with equal mass to be dissolved in 300mL of CH 3 OH and 250mL CH 3 In the OH solution, marked as solution A and solution B, after being subjected to ultrasonic treatment for 30min, zinc nitrate hexahydrate ((Zn (NO) 3 ) 2 ·6H 2 O) and 2-methylimidazole are dissolved in the solution A and the solution B respectively according to the mass ratio of 2.5g to 4.1g, the in-situ synthesis reaction is continuously carried out for 30min at the temperature of 10 ℃, and the obtained solid precipitate is purified (the obtained solid precipitate is treated by CH at the temperature of 35℃) 3 OH solution is soaked for 12 h) and dried to obtain N-CQD/ZIF-8.
Step three: cuprous oxide (Cu) 2 Preparation of O)/nitrogen-doped carbon quantum dot (N-CQD)/metal organic framework material ZIF-8
0.17g of CuCl was weighed 2 ·2H 2 Dissolving O and 0.5g N-CQD/ZIF-8 catalyst in 100mL water, stirring at room temperature for 30min, and dropwise adding CuCl 2 ·2H 2 O solution (0.17 g CuCl) 2 ·2H 2 Dissolving O in 100mL of water), sequentially adding 1g of SDBS and 0.8g of NaOH, stirring at normal temperature for 30min, then adding 0.8g of ascorbic acid, stirring at 10 ℃ for 1h, centrifuging, washing, and drying in a vacuum drying oven at 60 ℃ for 12h to obtain Cu 2 An O/N-CQD/ZIF-8 ternary composite photocatalyst, namely a ZIF-8 type composite photocatalyst.
Example 3
The method comprises the following steps: preparation of biomass nitrogen-doped carbon quantum dots (N-CQD)
The method comprises the steps of placing the walnut shells made of the waste biomass materials into an oven, drying, beating into small blocks, crushing by using a crusher, placing in a sample bag, and drying for later use. Weighing 1.0g of walnut shell and 0.2g of urea, and fully dissolving the walnut shell and the urea in 50mL of deionized water and uniformly stirring. Continuously carrying out hydrothermal reaction at 180 ℃ for 18h, carrying out purification operations such as centrifugation and dialysis, and carrying out freeze drying to obtain the purified N-CQD.
Step two: preparation of nitrogen-doped carbon quantum dot (N-CQD)/metal organic framework material ZIF-8
Respectively weighing 0.0015g of biomass N-CQD with equal mass, and respectively dissolving in 300mL of CH 3 OH and 250mL CH 3 In the OH solution, marked as solution A and solution B, after being subjected to ultrasonic treatment for 30min, zinc nitrate hexahydrate ((Zn (NO) 3 ) 2 ·6H 2 O) and 2-methylimidazole are respectively dissolved in the solution A and the solution B according to the mass ratio of 5g to 4.1g, the in-situ synthesis reaction is continuously carried out for 30min at the temperature of 35 ℃, and the obtained solid precipitate is purified (the obtained solid precipitate is treated by CH at the temperature of 25 ℃ by using CH) 3 OH solution is soaked for 18 h) and dried to obtain N-CQD/ZIF-8.
Step three: cuprous oxide (Cu) 2 Preparation of O)/nitrogen-doped carbon quantum dot (N-CQD)/metal organic framework material ZIF-8
0.17g of CuCl was weighed 2 ·2H 2 Dissolving O and 0.5g N-CQD/ZIF-8 catalyst in 100mL water, stirring at room temperature for 30min, and dropwise adding CuCl 2 ·2H 2 O solution (0.17 g CuCl) 2 ·2H 2 Dissolving O in 100mL of water), sequentially adding 1g of SDBS and 0.8g of NaOH, stirring at normal temperature for 30min, then adding 0.8g of ascorbic acid, stirring at 15 ℃ for 1h, centrifuging, washing, and drying in a vacuum drying oven at 60 ℃ for 12h to obtain Cu 2 The O/N-CQD/ZIF-8 ternary composite photocatalyst is a ZIF-8 type composite photocatalyst.
Example 4
The method comprises the following steps: preparation of biomass nitrogen-doped carbon quantum dots (N-CQD)
And (3) placing the waste biomass material plate chestnut shells in an oven for drying, then beating the chestnut shells into small blocks, crushing the small blocks by using a crusher, and placing the small blocks in a sample bag for drying for later use. Weighing 1.0g of chestnut shell and 0.1g of urea, and fully dissolving the chestnut shell and the urea in 50mL of deionized water and uniformly stirring. And (3) continuously carrying out hydrothermal reaction for 16h at 150 ℃, and carrying out purification operations such as centrifugation, dialysis and the like, and freeze-drying to obtain the purified N-CQD.
Step two: preparation of nitrogen-doped carbon quantum dot (N-CQD)/metal organic framework material ZIF-8
Respectively weighing 0.0015g of biomass N-CQD with equal mass, and respectively dissolving in 300mL of CH 3 OH and 250mL CH 3 In the OH solution, marked as solution A and solution B, after being subjected to ultrasonic treatment for 30min, zinc nitrate hexahydrate ((Zn (NO) 3 ) 2 ·6H 2 O) and 2-methylimidazole are dissolved in the solution A and the solution B respectively according to the mass ratio of 3.7g to 4.1g, the in-situ synthesis reaction is continuously carried out for 30min at the temperature of 20 ℃, and the obtained solid precipitate is purified (the obtained solid precipitate is treated by CH at the temperature of 30 ℃ by using CH) 3 OH solution is soaked for 14 h) and dried to obtain N-CQD/ZIF-8.
Step three: cuprous oxide (Cu) 2 Preparation of O)/nitrogen-doped carbon quantum dot (N-CQD)/metal organic framework material ZIF-8
0.17g of CuCl was weighed 2 ·2H 2 Dissolving O and 0.5g N-CQD/ZIF-8 catalyst in 100mL water, stirring at room temperature for 30min, and dropwise adding CuCl 2 ·2H 2 O solution (0.17 g CuCl) 2 ·2H 2 O is dissolved in 100mL of water), 1g of SDBS and 0.8g of NaOH are sequentially added and stirred for 30min at normal temperature, then 0.8g of ascorbic acid is added, the mixture is stirred for 1h at 20 ℃, then centrifugal washing is carried out, and the mixture is dried for 12h in a vacuum drying oven at 60 ℃ to obtain Cu 2 An O/N-CQD/ZIF-8 ternary composite photocatalyst, namely a ZIF-8 type composite photocatalyst.
Example 5
The method comprises the following steps: preparation of biomass nitrogen-doped carbon quantum dots (N-CQD)
And (3) placing the waste biomass material mangosteen shells into an oven for drying, then beating the waste biomass material mangosteen shells into small blocks, crushing the small blocks by using a crusher, and placing the crushed small blocks into a sample bag for drying for later use. 1.0g of mangosteen shell and 0.4g of urea are weighed and fully dissolved in 50mL of deionized water to be uniformly stirred. And continuously carrying out hydrothermal reaction at 130 ℃ for 24h, carrying out purification operations such as centrifugation and dialysis, and carrying out freeze drying to obtain the purified N-CQD.
Step two: preparation of nitrogen-doped carbon quantum dot (N-CQD)/metal organic framework material ZIF-8
Respectively weighing 0.0015g of biomass N-CQD with equal massDissolved in 300mL CH 3 OH and 250mL CH 3 In the OH solution, marked as solution A and solution B, after being subjected to ultrasonic treatment for 30min, zinc nitrate hexahydrate ((Zn (NO) 3 ) 2 ·6H 2 O) and 2-methylimidazole are dissolved in the solution A and the solution B respectively according to the mass ratio of 3.7g to 4.1g, the in-situ synthesis reaction is continuously carried out for 30min at the temperature of 20 ℃, and the obtained solid precipitate is purified (the obtained solid precipitate is treated by CH at the temperature of 30 ℃ by using CH) 3 OH solution is soaked for 20 h) and dried to obtain N-CQD/ZIF-8.
Step three: cuprous oxide (Cu) 2 Preparation of O)/nitrogen-doped carbon quantum dot (N-CQD)/metal organic framework material ZIF-8
0.2g of CuCl is weighed out 2 ·2H 2 Dissolving O and 0.5g N-CQD/ZIF-8 catalyst in 100mL water, stirring at room temperature for 30min, and dropwise adding CuCl 2 ·2H 2 O solution (0.2 g CuCl) 2 ·2H 2 O is dissolved in 100mL of water), 1g of SDBS and 0.8g of NaOH are sequentially added and stirred for 30min at normal temperature, then 0.8g of ascorbic acid is added, the mixture is stirred for 1h at 25 ℃, then centrifugal washing is carried out, and the mixture is dried for 12h in a vacuum drying oven at 60 ℃ to obtain Cu 2 The O/N-CQD/ZIF-8 ternary composite photocatalyst is a ZIF-8 type composite photocatalyst.
Example 6
The method comprises the following steps: preparation of biomass nitrogen-doped carbon quantum dots (N-CQD)
And (3) placing the waste biomass material mangosteen shells in an oven for drying, then beating the waste biomass material mangosteen shells into small blocks, crushing the small blocks by using a crusher, and placing the small blocks in a sample bag for drying for later use. 1.0g of mangosteen shell and 0.3g of urea are weighed and fully dissolved in 50mL of deionized water to be uniformly stirred. Continuously carrying out hydrothermal reaction at 130 ℃ for 24h, carrying out purification operations such as centrifugation and dialysis, and carrying out freeze drying to obtain the purified N-CQD.
Step two: preparation of nitrogen-doped carbon quantum dot (N-CQD)/metal organic framework material ZIF-8
Respectively weighing 0.001g of biomass N-CQD with equal mass, and respectively dissolving in 200mL of CH 3 OH and 300mL CH 3 In the OH solution, marked as solution A and solution B, after being subjected to ultrasonic treatment for 30min, zinc nitrate hexahydrate ((Zn (NO) 3 ) 2 ·6H 2 O) and 2-methylimidazole are dissolved in the solutions A and B according to the mass ratio of 4.1gIn situ synthesis reaction was carried out continuously at 18 ℃ for 30min, and purification was carried out (solid precipitate obtained was purified with CH at 20 ℃) 3 OH solution is soaked for 24 hours) and dried to obtain the N-CQD/ZIF-8.
Step three: cuprous oxide (Cu) 2 Preparation of O)/nitrogen-doped carbon quantum dot (N-CQD)/metal organic framework material ZIF-8
0.1g of CuCl is weighed out 2 ·2H 2 Dissolving O and 1gN-CQD/ZIF-8 catalyst in 100mL water, stirring at normal temperature for 30min, and dropwise adding CuCl 2 ·2H 2 O solution (0.1 g CuCl) 2 ·2H 2 O dissolved in 100mL of water), adding 1g of alpha-olefin sulfonate (AOS) and 0.8g of KOH in sequence, stirring for 30min at normal temperature, adding 0.8g of glucose, stirring for 1h at 35 ℃, centrifuging, washing, and drying for 20h in a vacuum drying oven at 70 ℃ to obtain Cu 2 An O/N-CQD/ZIF-8 ternary composite photocatalyst, namely a ZIF-8 type composite photocatalyst.
Example 7
The method comprises the following steps: preparation of biomass nitrogen-doped carbon quantum dots (N-CQD)
And (3) placing the waste biomass material mangosteen shells in an oven for drying, then beating the waste biomass material mangosteen shells into small blocks, crushing the small blocks by using a crusher, and placing the small blocks in a sample bag for drying for later use. 1.0g of mangosteen shell and 0.1g of urea are weighed and fully dissolved in 50mL of deionized water to be uniformly stirred. And continuously carrying out hydrothermal reaction at 130 ℃ for 24h, carrying out purification operations such as centrifugation and dialysis, and carrying out freeze drying to obtain the purified N-CQD.
Step two: preparation of nitrogen-doped carbon quantum dot (N-CQD)/metal organic framework material ZIF-8
Respectively weighing 0.003g of biomass N-CQD with equal mass, and respectively dissolving the biomass N-CQD in 250mL of CH 3 OH and 200mL CH 3 In the OH solution, marked as solution A and solution B, after being subjected to ultrasonic treatment for 30min, zinc nitrate hexahydrate ((Zn (NO) 3 ) 2 ·6H 2 O) and 2-methylimidazole are dissolved in the solution A and the solution B respectively according to the mass ratio of 4.6g to 4.1g, the in-situ synthesis reaction is continuously carried out for 30min at the temperature of 30 ℃, and the obtained solid precipitate is purified (the obtained solid precipitate is treated by CH at the temperature of 35 ℃ by using CH) 3 OH solution is soaked for 12 h) and dried to obtain N-CQD/ZIF-8.
Step three: cuprous oxide (Cu) 2 O)/nitrogenPreparation of carbon quantum dot (N-CQD)/metal organic framework material ZIF-8
Weighing 0.12g of cuprous sulfate and 0.8g of N-CQD/ZIF-8 catalyst, dissolving in 100mL of water, stirring at normal temperature for 30min, dropwise adding a cuprous sulfate solution (0.12 g of cuprous sulfate is dissolved in 100mL of water), sequentially adding 1g of sodium 2-hydroxyethyl sulfonate (SHES) and 0.8g of KOH, stirring at normal temperature for 30min, then adding 0.8g of glucose, stirring at 10 ℃ for 1h, centrifuging, washing, and drying in a vacuum drying oven at 80 ℃ for 10 h to obtain Cu 2 An O/N-CQD/ZIF-8 ternary composite photocatalyst, namely a ZIF-8 type composite photocatalyst.
The invention is described in further detail below with reference to the accompanying drawings:
referring to FIG. 1, it can be seen that the characteristic absorption peaks shown in the figure are all matched with the characteristic absorption peaks of the functional groups (such as N-H, C = C, C-H, O-H) which are generated in the reaction. Proves that N-CQD and metal organic framework material ZIF-8 are firmly combined together through functional group reaction, and Cu 2 O is successfully loaded on the N-CQD/ZIF-8 composite material.
Referring to FIG. 2, it can be seen that ZIF-8 exhibits selective absorption at a wavelength ranging from 200 to 400nm, incorporating Cu 2 After O, the absorption peak moves to the long wave direction, so that red shift occurs, and the absorption intensity is enhanced accordingly.
Referring to FIG. 3, it can be seen that Cu 2 The fluorescence intensity of the O/N-CQD/ZIF-8 composite photocatalyst (namely the ZIF-8 composite photocatalyst) is far lower than that of ZIF-8 and N-CQD/ZIF-8 composite materials, and the result shows that Cu 2 The introduction of O inhibits the rapid recombination of photogenerated electron-hole pairs generated by the material, thereby improving the Cu content 2 The performance of the O/N-CQD/ZIF-8 composite material in photocatalytic reduction of Cr (VI).
Referring to FIG. 4, the loads N-CQD and Cu are known 2 After O, the photocatalytic performance of the metal organic framework material ZIF-8 is remarkably improved to about six times of the original photocatalytic performance.
In conclusion, the invention discloses a ZIF-8 type composite photocatalyst and a preparation method thereof, and aims to provide a novel composite photocatalyst prepared by improving the ZIF-8 photocatalytic performance. The invention uses the walnut shell which is a biomass material as a raw material to prepare N-CQD by a hydrothermal method,the biomass N-CQD and the metal organic framework material ZIF-8 are effectively combined by adopting an in-situ synthesis method to prepare the N-CQD/ZIF-8. Then Cu is reduced and precipitated 2 O is introduced into N-CQD/ZIF-8 to prepare three-dimensional Cu 2 The O/N-CQD/ZIF-8 composite photocatalyst is a ZIF-8 composite photocatalyst, effectively improves the photocatalytic performance of ZIF-8, has short process flow, low energy consumption and cheap and easily-obtained raw materials, and is an ideal ZIF-8 composite photocatalyst Cu 2 A preparation method of O/N-CQD/ZIF-8.
The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.

Claims (5)

1. A preparation method of a ZIF-8 type composite photocatalyst is characterized in that a biomass material is used as a raw material, firstly a hydrothermal method is adopted to prepare biomass N-CQD, then the obtained biomass N-CQD and a metal organic framework material ZIF-8 are prepared into N-CQD/ZIF-8 by an in-situ synthesis method, and finally a reductive precipitation method is adopted to prepare Cu by Cu 2 Introducing O into N-CQD/ZIF-8 to obtain ZIF-8 type composite photocatalyst; the method specifically comprises the following steps:
1) Crushing and drying a biomass material to obtain biomass powder, and carrying out hydrothermal reaction on the biomass powder and urea to obtain biomass N-CQD; the biomass material is walnut shell, chestnut shell or mangosteen shell, and the mass ratio of the biomass powder to the urea is 1g (0.1 to 0.4) g;
2) Respectively and uniformly dispersing the obtained biomass N-CQD in two solutions to respectively obtain a solution A and a solution B, and respectively dissolving a metal zinc-based precursor and an imidazole ligand in the solution A and the solution B to obtain a reaction solution A and a reaction solution B; reacting the obtained reaction liquid A and the reaction liquid B based on an in-situ synthesis method to obtain a solid precipitate, and purifying and drying the obtained solid precipitate to obtain N-CQD/ZIF-8;
when preparing solution A or solution B, the solution is CH 3 The dosage ratio of the OH solution, the biomass N-CQD and the solvent is 0.001 to 0.003g, 200 to 300 mL; the mass ratio of the biomass N-CQD to the metal zinc-based precursor to the imidazole ligand is 0.001-0.003 g;
3) Dissolving a metal copper salt and N-CQD/ZIF-8 in water to prepare a metal copper salt/N-CQD/ZIF-8 solution; dissolving another copper salt with equal mass in water to prepare a copper salt solution; dripping the obtained metal copper salt solution into the obtained metal copper salt/N-CQD/ZIF-8 solution, continuously adding a sulfonate dispersant, an alkaline substance and a reducing agent to perform a reduction precipitation reaction at normal temperature, centrifuging after the reaction is finished to obtain a solid product, washing the obtained solid product, and drying to obtain the ZIF-8 type composite photocatalyst;
when preparing a solution of the metal copper salt/N-CQD/ZIF-8, the mass ratio of the metal copper salt to the N-CQD/ZIF-8 is 0.1-0.2 g: 0.5-1 g; the feeding ratio of the metallic copper salt to the sulfonate dispersant, the alkaline substance to the reducing agent is 0.1 to 0.2g, 1g:0.8 g:0.8g.
2. The method for preparing the ZIF-8 type composite photocatalyst as defined in claim 1, wherein the metallic copper salt is cupric chloride dihydrate or cuprous sulfate;
the sulfonate dispersant is sodium dodecyl benzene sulfonate, alpha-olefin sulfonate or 2-hydroxy ethyl sodium sulfonate.
3. The method for preparing the ZIF-8 type composite photocatalyst as claimed in claim 1, wherein the alkaline substance is NaOH or KOH;
the reducing agent is ascorbic acid or glucose.
4. The preparation method of the ZIF-8 type composite photocatalyst as claimed in claim 1, wherein the reaction temperature of the hydrothermal reaction is 100 to 200 ℃ and the reaction time is 12 to 24 hours;
the reaction temperature of the in-situ synthesis method is 10 to 35 ℃;
the reaction temperature of the reduction precipitation method is 10 to 35 ℃.
5. A ZIF-8 type composite photocatalyst prepared by the preparation method of any one of claims 1~4.
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