G-C3N4 / Cu-BTC catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of photocatalytic materials, and particularly relates to a g-C3N4 / Cu-BTC catalyst as well as a preparation method and application thereof. According to the preparation method, after Cu-BTC blue powder crystals are prepared through a hydrothermal method, melamine is placed in a muffle furnace to be subjected to high-temperature calcination treatment, yellow powdery g-C3N4 can be prepared, then a physical grinding composite method is adopted, the prepared Cu-BTC blue powder and the prepared g-C3N4 yellow powder are mixed according to a preset mass ratio, mechanical fusion is achieved through sufficient grinding, and the g-C3N4 / Cu-BTC composite material is obtained. Finally, the g-C3N4 / Cu-BTC catalyst with the composite structure is prepared and obtained. According to the preparation process, through the synergistic effect of hydrothermal synthesis and high-temperature calcination and in combination with a composite process of physical grinding, structural integration and performance synergy of two functional materials are achieved, and a preparation path of an efficient composite material is provided for application of photocatalytic inhibition of heterosylvus rugosa and the like.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic materials technology, specifically relating to a g-C3N4 / Cu-BTC catalyst, its preparation method, and its application. Background Technology

[0002] Harmful algal blooms (HABs), especially those caused by *Heterosigma akashiwo*, have become a widespread ecological crisis in coastal waters worldwide. These blooms not only deplete dissolved oxygen and disrupt aquatic food webs, but also secrete ichthyotoxins that cause mass fish deaths in aquaculture, resulting in catastrophic economic losses and severely threatening marine biodiversity. While traditional control strategies (such as clay physical flocculation and chemical algicide inactivation) can alleviate blooms to some extent, they often suffer from high operating costs, low efficiency, and, more critically, the risk of secondary pollution to the ecosystem. Therefore, there is an urgent need to develop green, sustainable, and efficient technologies to control harmful algal blooms without compromising environmental safety.

[0003] Among novel pollution control technologies, photocatalytic inactivation based on advanced oxidation processes (AOPs) has attracted significant attention due to its ability to utilize solar energy for deep mineralization of organic pollutants and microorganisms. To date, numerous photocatalysts have been successfully developed and applied to freshwater algal bloom control, with extensive research focusing on the photocatalytic control of cyanobacteria (such as Microcystis aeruginosa). However, research on the photocatalytic inactivation of harmful marine algae remains relatively scarce. Unlike freshwater environments, marine environments are characterized by high salinity and complex ionic backgrounds, placing more stringent demands on the stability and activity of photocatalysts. Therefore, developing highly stable photocatalysts specifically designed for marine red tide control has significant scientific and practical implications. Summary of the Invention

[0004] The technical problem to be solved by this invention is to address the shortcomings of existing technologies by providing a strategy that combines the visible light response characteristics of g-C3N4 with the high specific surface area and regular pore structure of Cu-BTC. Through the S-type heterojunction interface, charge dynamics are synergistically optimized—under visible light irradiation, photogenerated electrons in the conduction band of g-C3N4 migrate directionally to the valence band of Cu-BTC, achieving a unity of high efficiency photocatalytic performance, wide environmental adaptability, and green sustainability, providing an innovative composite catalytic solution for marine red tide control and water body restoration.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] The first aspect of this invention provides a method for preparing a g-C3N4 / Cu-BTC catalyst, comprising the following steps:

[0007] S1. Cu-BTC is prepared by uniformly mixing copper nitrate solution and trimesic acid solution and then undergoing a crystallization reaction.

[0008] S2. Melamine was calcined at high temperature to prepare g-C3N4;

[0009] S3. Mix g-C3N4 and Cu-BTC evenly and grind thoroughly to obtain the g-C3N4 / Cu-BTC catalyst.

[0010] In S1, the volume ratio of the copper nitrate solution to the trimesic acid solution is 1:1.

[0011] In S1, the concentration of the copper nitrate solution is 0.05 g / mL, and the solvent is deionized water; the concentration of the trimesic acid solution is 0.02 g / mL, and the solvent is anhydrous ethanol.

[0012] Specifically, a 1:1 mixture of water and ethanol can create a gradient polarity environment. 2+ It is readily hydrolyzed in pure aqueous phase, but the addition of ethanol can adjust the polarity of the system, promote the dissolution and deprotonation of trimesic acid (H3BTC), and simultaneously inhibit Cu. 2+ Excessive hydrolysis ensures that the coordination reaction proceeds efficiently within a suitable pH range. Experiments show that this ratio results in the highest ligand-metal charge transfer efficiency, which is beneficial for the formation of a stable Cu-BTC three-dimensional network structure.

[0013] In S1, the conditions for the crystallization reaction are: temperature 120~150 ℃, time 12~15 h.

[0014] Specifically, the reaction temperature should be controlled at 120~150 ℃ for the synthesis of Cu-BTC blue powder crystals. The reaction time should be controlled at 12~15 h to facilitate the dispersion of nanoparticles. If the time is less than 12 h, unreacted precursors may remain, and if the time exceeds 15 h, it will lead to crystal agglomeration.

[0015] In some embodiments of the present invention, in S1, the conditions for the crystallization reaction are: temperature 120 °C and time 12 h.

[0016] In some embodiments of the present invention, in S1, after the crystallization reaction is completed, the solid is collected by centrifugation, washed multiple times with a mixed solution of deionized water and ethanol in a volume ratio of 1:1, and finally dried at 80 °C for 12 h to obtain blue powder crystal Cu-BTC.

[0017] In S2, the conditions for high-temperature calcination are: heating rate of 5 ℃ / min, calcination temperature of 500~550 ℃, and calcination time of 2~4 h.

[0018] Specifically, this temperature range ensures the full polymerization of the triazine ring structure to form a highly crystalline graphite phase structure, while avoiding the residual organic precursors caused by low temperatures (<500 ℃) and the collapse of the layered structure caused by high temperatures (>550 ℃). Phase transformation kinetic studies show that the initiation temperature for the transformation of amorphous precursors to the graphite phase is 480 ℃. Below this temperature, undecomposed amino groups will remain, while above 550 ℃, local carbonization is easily induced. The calcination time needs to be strictly controlled within 2~4 h: less than 2 h will result in incomplete formation of the carbon-nitrogen skeleton and residual carbon impurities; more than 4 h may cause excessive grain growth and reduce the specific surface area.

[0019] In some embodiments of the present invention, in S2, the conditions for high-temperature calcination are: heating rate of 5 °C / min, calcination temperature of 550 °C, and calcination time of 4 h.

[0020] In some embodiments of the present invention, in S2, after high-temperature calcination, the product is cooled to room temperature, collected, and ground into powder to obtain g-C3N4.

[0021] In S3, the mass of g-C3N4 is 5-30% of the mass of Cu-BTC.

[0022] In some embodiments of the present invention, in S3, the mass of the g-C3N4 is 10% or 30% of the mass of Cu-BTC.

[0023] In some embodiments of the present invention, in S3, the mass of g-C3N4 is 10% of the mass of Cu-BTC.

[0024] A second aspect of the present invention provides a g-C3N4 / Cu-BTC catalyst prepared by the aforementioned preparation method.

[0025] The particle size of the g-C3N4 / Cu-BTC catalyst is 300~800 nm.

[0026] A third aspect of the present invention provides the application of a g-C3N4 / Cu-BTC catalyst in the photocatalytic suppression of harmful algal blooms.

[0027] The effective concentration of the g-C3N4 / Cu-BTC catalyst is 1~5 mg / mL.

[0028] In some embodiments of the present invention, the effective concentration of the g-C3N4 / Cu-BTC catalyst is 2 mg / mL.

[0029] In some embodiments of the present invention, the harmful algal bloom is selected from red tide microalgae, specifically Heterosigma akashiwo (strain number: CCMALYG001).

[0030] In some embodiments of the present invention, the g-C3N4 / Cu-BTC catalyst was successfully prepared by the above-described preparation method. Photocatalytic algal bloom inhibition experiments showed that at an effective concentration of 2 mg / mL, and when the mass of g-C3N4 was 10% of the mass of Cu-BTC, the g-C3N4 / Cu-BTC catalyst exhibited the optimal photocatalytic inhibition efficiency. This complex significantly reduced the carotenoid content of *Heterosigma rubrum*, with the reduction reaching the maximum observed value. This phenomenon confirms that 10CN / Cu-BTC can maximize the photocatalytic inhibition activity of the complex against the target algal species. The mechanism may stem from the heterogeneous interface formed by g-C3N4 and Cu-BTC promoting effective separation of photogenerated carriers, thereby enhancing the oxidative stress response and inhibiting the synthesis of key pigments in algal photosynthesis. This demonstrates the promising application of the g-C3N4 / Cu-BTC catalyst in the photocatalytic inhibition of harmful algal blooms.

[0031] Beneficial effects:

[0032] This invention utilizes a hydrothermal method to prepare Cu-BTC, enabling precise control of crystal nucleation and growth kinetics to obtain highly crystalline, uniform (micrometer-scale) blue powder crystals. Its three-dimensional network structure facilitates mass transfer and adsorption. High-temperature calcination of melamine efficiently removes amino groups and polymerizes triazine rings, forming a layered, stacked graphitic phase g-C3N4. The yellow powder product exhibits intrinsic visible light response characteristics (absorption sideband approximately 460 nm). The physical grinding composite method is simple to operate and low in cost, requiring no solvents or high-temperature, high-pressure conditions. It achieves uniform mixing and interfacial fusion of the two powders through mechanical shear force, avoiding structural damage caused by chemical bonding. This method, through gradient optimization of process, structure, and performance, realizes a complete technical path from basic material preparation to functional composite, providing a scientifically reliable solution for the design and application of high-performance photocatalytic composite materials.

[0033] The g-C3N4 / Cu-BTC catalyst achieves functional synergy through its heterostructure: Cu-BTC's high specific surface area and regular pores can enrich target pollutants (such as Heterosigma auriculata) and simultaneously act as an electron transport channel to promote the separation of photogenerated carriers; g-C3N4's suitable band structure (approximately 2.7 eV) endows it with visible light photocatalytic activity, and the S-type heterojunction formed at the interface of the two can effectively inhibit electron-hole recombination and prolong carrier lifetime. Experiments show that when the mass ratio is 1:10 (10% g-C3N4), due to the optimal interfacial contact area and band structure matching, the complex achieves a peak inhibition rate of carotenoids against Heterosigma auriculata, realizing 89.90% inhibition of algal cell density and a 93.05% reduction in carotenoid content within 60 min. By combining g-C3N4 with Cu-BTC to form an S-type heterojunction, photogenerated carrier recombination is effectively suppressed, and hole lifetime is extended to the microsecond level. At the same time, the composite material exhibits a synergistic effect in the inhibition experiment of red tide Heterobacter pluvialis. Finally, a multifunctional composite system integrating adsorption, photocatalysis and anti-bioattachment is formed, providing an efficient, stable and green solution for marine red tide management and water body restoration. Attached Figure Description

[0034] The present invention will be further described in detail below with reference to the accompanying drawings, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0035] Figure 1 This is a process flow diagram for the preparation of the g-C3N4 / Cu-BTC catalyst in this embodiment of the invention.

[0036] Figure 2 This is a diagram showing the results of a photocatalytic algae suppression experiment in an embodiment of the present invention. Detailed Implementation

[0037] The present invention will be further described in detail below with reference to specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0038] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0039] Example 1:

[0040] This embodiment provides a method for preparing a g-C3N4 / Cu-BTC catalyst. Figure 1 The process flow diagram for preparing the g-C3N4 / Cu-BTC catalyst includes the following steps:

[0041] S1. Weigh 0.84 g Cu(NO3)2·3H2O and dissolve it in 18 mL of deionized water, denoted as solution A. Weigh 0.39 g trimesic acid and dissolve it in 18 mL of anhydrous ethanol, denoted as solution B. Place solution A and solution B together in a magnetic stirrer and stir for 30 min. After mixing evenly, transfer the mixture to a 100 mL reaction vessel lined with polytetrafluoroethylene. Place the vessel in an oven and heat it to 120 °C. After crystallization for 12 h, cool it to room temperature. Collect the solid by centrifugation and wash it several times with a 1:1 volume ratio of deionized water and ethanol. Finally, dry it at 80 °C for 12 h to obtain blue powder crystal Cu-BTC.

[0042] S2. Weigh 6 g of melamine and place it in a covered alumina crucible. Calcinate the melamine in a muffle furnace at 550 °C for 4 h with a heating rate of 5 °C / min. After the reaction is complete, allow it to cool to room temperature, collect the light yellow product, and grind it into powder to obtain g-C3N4.

[0043] S3. Weigh g-C3N4 and Cu-BTC in different mass ratios into a mortar, add a small amount of anhydrous ethanol, grind until the powder is evenly mixed, and finally dry at 80 ℃ for 2 h to obtain the g-C3N4 / Cu-BTC catalyst, denoted as xCN / Cu-BTC, where "x" represents the mass percentage of g-C3N4 in Cu-BTC in the catalyst, which are 5%, 10%, 15%, 20%, 25% and 30%, respectively.

[0044] The catalytic ability of different xCN / Cu-BTC ratios was verified through photocatalytic algae suppression experiments. The red tide microalga used in this example was *Heterosigma akashiwo* (strain number: CCMALYG001), isolated from the Lianyungang sea area in 2020 and kindly provided by Professor Ji Nanjing's research group at Jiangsu Ocean University. This algal strain was cultured in sterile F / 2 medium at a temperature of 20 ± 1 ℃ and a light intensity of 2000 lux (approximately 36 μmol photons m²). -2 s -1 The light-dark cycle was 12 h:12 h. Before conducting the photocatalysis experiment, algal culture in the logarithmic growth phase was inoculated into freshly sterilized F / 2 medium, and its initial cell density was adjusted to approximately 7.5 × 10⁻⁶ cells / day. 4The specific experimental steps are as follows: The photocatalytic algae inhibition experiment was conducted in 200 mL glass test tubes. To evaluate the effect of different Cu-BTC loading ratios, 200.00 mg of different xCN / Cu-BTC catalysts (x=5, 10, 15, 20, 25, 30) were accurately weighed, with pure g-C3N4 and pure Cu-BTC as controls. These were added to test tubes containing 100 mL of prepared algal solution, ensuring a final concentration of 2 mg / mL for each catalyst. The reaction vessel was fixed in a temperature-controlled, light-controlled, and shaking incubator (HY-4, Shanghai Surui Instruments Co., Ltd., China), with a shaking rate of 150 rpm. A 30 W full-spectrum LED lamp (color temperature 5000 K, color rendering index Ra 95, Guanglian Tianxia, ​​China) was used to provide simulated sunlight irradiation, with a light intensity of 1200 W / m² on the algal solution surface. 2 (Approximately 33,000 lux), the reaction system was continuously irradiated with light at 20 ± 1 °C for 60 min.

[0045] Algal cell density was determined by direct microscopic counting using a hemocytometer (Type 1103, Shanghai Qiujing). The content of photosynthetic pigments (specifically carotenoids) was determined by a modified spectrophotometric method. The specific steps were as follows: 1 mL of algal solution was centrifuged at 12000 rpm for 10 min to collect the algal cell precipitate. The supernatant was discarded, and 1 mL of chromatographic grade methanol was added for pigment extraction. The mixture was vortexed vigorously for 30 s, and then placed in a 60 ℃ water bath for 15 min in the dark. After centrifugation again (12000 rpm, 10 min) to remove cell debris, the absorbance of the supernatant at 440, 662, and 644 nm was measured using a UV-Vis spectrophotometer (V-5100, Shanghai Yuanxi). The carotenoid concentration was calculated according to formula (1):

[0046] Carotenoid (mg / L) = 4.7 × OD 440 - (1.38 × OD 662 + 5.48 × OD 644 (1)

[0047] Figure 2 The image shows the results of a photocatalytic algae suppression experiment. Figure 2 Figure 'a' shows the change in carotenoid content with light exposure time. Figure 2 Figure 'b' shows the change in algal cell density over time. Carotenoids are the most important photosynthetic pigments and antioxidants in *Heterosigma rubrum* cells. A rapid decrease in their content indicates damage to the algal cells' photosynthetic system and severe oxidative damage, a key indicator of algal inactivation or death. Figure 2As shown in section 'a', compared to the curves of pure Cu-BTC and pure g-C3N4, all xCN / Cu-BTC catalysts exhibited superior carotenoid degradation capabilities, and the degradation rate was related to the loading ratio. The 10CN / Cu-BTC catalyst showed the best degradation effect, indicating that when g-C3N4 and Cu-BTC are combined in this ratio, an optimal heterojunction structure may be formed, achieving the most efficient photogenerated charge separation, thereby generating more reactive oxygen species to attack algal cells. Changes in algal cell density directly reflect changes in algal biomass and are a direct indicator of the final algal suppression effect; a significant decrease in cell density means that the algae have been killed or inactivated. Figure 2 As shown in b in the figure, the changes in algal cell density have similar results to the carotenoid degradation in figure a. Compared with the curves of pure Cu-BTC and pure g-C3N4, all xCN / Cu-BTC catalysts can reduce the cell density to 4 × 10⁻⁶ after 60 minutes. 4 The catalysts exhibited strong algicidal capabilities, reducing cell density to below 0.71 × 10⁻⁶ cells / mL. Among them, the 10CN / Cu-BTC catalyst showed the best degradation effect, decreasing cell density to 0.71 × 10⁻⁶ cells / mL after 60 minutes. 4 The number of cells / mL is significantly lower than other xCN / Cu-BTC catalysts.

[0048] This invention provides a g-C3N4 / Cu-BTC catalyst, its preparation method, and its application. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A method for preparing a g-C3N4 / Cu-BTC catalyst, characterized in that, Includes the following steps: S1. Cu-BTC is prepared by uniformly mixing copper nitrate solution and trimesic acid solution and then undergoing a crystallization reaction. S2. Melamine was calcined at high temperature to prepare g-C3N4; S3. Mix g-C3N4 and Cu-BTC evenly and grind thoroughly to obtain the g-C3N4 / Cu-BTC catalyst.

2. The preparation method according to claim 1, characterized in that, In S1, the volume ratio of the copper nitrate solution to the trimesic acid solution is 1:

1.

3. The preparation method according to claim 2, characterized in that, In S1, the concentration of the copper nitrate solution is 0.05 g / mL, and the solvent is deionized water; the concentration of the trimesic acid solution is 0.02 g / mL, and the solvent is anhydrous ethanol.

4. The preparation method according to claim 1, characterized in that, In S1, the conditions for the crystallization reaction are: temperature 120~150 ℃, time 12~15 h.

5. The preparation method according to claim 1, characterized in that, In S2, the conditions for high-temperature calcination are: heating rate of 5 ℃ / min, calcination temperature of 500~550 ℃, and calcination time of 2~4 h.

6. The preparation method according to claim 1, characterized in that, In S3, the mass of g-C3N4 is 5-30% of the mass of Cu-BTC.

7. The g-C3N4 / Cu-BTC catalyst prepared by the preparation method according to any one of claims 1 to 6.

8. The g-C3N4 / Cu-BTC catalyst according to claim 7, characterized in that, The particle size of the g-C3N4 / Cu-BTC catalyst is 300~800 nm.

9. The application of the g-C3N4 / Cu-BTC catalyst according to claim 7 or 8 in photocatalytic suppression of harmful algal blooms.

10. The application according to claim 9, characterized in that, The effective concentration of the g-C3N4 / Cu-BTC catalyst is 1~5 mg / mL.

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