ZnTCPP-coated Ti-MOFs nanoparticles for microalgae carbon sequestration and oil production as well as preparation method and application of ZnTCPP-coated Ti-MOFs nanoparticles

Abstract

The invention discloses ZnTCPP-coated Ti-MOFs nanoparticles for microalgae carbon sequestration and oil production and a preparation method and application, and belongs to the technical field of microalgae biotechnology and biomass energy utilization, meso-tetra (4-carboxyphenyl) porphyrin and zinc acetate are added into an N, N-dimethylformamide solution, oil bath heating is performed, washing is performed until clarification is achieved, and ZnTCPP powder is obtained after freeze drying; the preparation method comprises the following steps: adding ZnTCPP powder into a mixed solution of methanol and N, N-dimethylformamide, adding 2-aminoterephthalic acid, carrying out ultrasonic treatment, stirring, adding tetrabutyl titanate, and carrying out hydrothermal reaction, washing and drying to obtain the ZnTCPP-coated Ti-MOFs nano-particles. Ti-MOF has extremely high CO2 adsorption capacity, carbon dioxide in the environment can be effectively enriched, and sufficient carbon source supply is ensured. ZnTCPP can enter microalgae cells, so that the activity of key enzymes is improved, and the efficiency of a carbon immobilization process and a grease synthesis path is promoted. By enhancing the enzyme activity, the ZnTCPP promotes the CO2 absorption and conversion of the microalgae, and improves the photosynthesis rate and the grease yield, thereby enhancing the overall carbon sequestration efficiency.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of microalgae biotechnology and biomass energy utilization, and particularly relates to ZnTCPP@Ti-MOFs nanoparticles for microalgae carbon fixation and oil production, a preparation method and application thereof. BACKGROUND

[0002] With global climate change and increasing energy demand, it is crucial to develop efficient and environmentally friendly carbon fixation and oil production technologies. Microalgae, as a fast-growing photosynthetic organism, can efficiently convert carbon dioxide into organic matter under light conditions and can be used to produce high-value-added products such as food, feed, and biofuels. Its high carbon fixation efficiency, strong environmental adaptability, and abundant resources make it an ideal choice for a new generation of clean, economic, and efficient renewable carbon fixation technology. However, in practical applications, the main challenge of microalgae carbon fixation technology is how to improve the CO2 fixation efficiency and oil production. Traditional culture systems have difficulty maintaining high carbon fixation rates in high-concentration CO2 environments, and low CO2 solubility, poor mass transfer capacity, and short residence time in water also limit the carbon fixation efficiency of microalgae. In addition, the use of carbon supplement devices increases the complexity and energy consumption of the system, which needs to be addressed.

[0003] The team of Academician Li Can of Nankai University published in Nature Communications (2023, 14, 5337) Enhancing photosynthetic CO2 fixation by assembling metal-organic frameworks on microalgae for bioenergy production Chlorella pyrenoidosa By synthesizing NH2-MIL-101-Fe and assembling it on the surface of microalgae, the carbon fixation efficiency of Chlorella vulgaris was improved by about 1.9 times, but the chlorophyll content in the microalgae cells was reduced after adding NH2-MIL-101-Fe material, and the researchers found that it did not significantly improve the oil production. Patent CN202410078293 reports a method for promoting inorganic carbon conversion of microalgae culture and carbon fixation using Zn / Fe MOFs nanoparticles. In this method, Zn / Fe MOFs nanomaterials are prepared by two-step heating reaction of zinc salt, iron salt and 2-methylimidazole, but its function is single and cannot meet the growing energy demand.

[0004] Therefore, it is of great significance to develop a dual-functional material that can promote microalgae carbon fixation and oil production with a simple preparation method. SUMMARY

[0005] In order to overcome the above-mentioned defects of the prior art, the purpose of the present application is to provide ZnTCPP@Ti-MOFs nanoparticles for microalgae carbon fixation and oil production, a preparation method and application, so as to solve the technical problems that the existing microalgae carbon fixation and oil production technology is difficult to maintain a high carbon fixation rate in a high concentration CO2 environment, the CO2 dissolution rate is low, the mass transfer capacity is poor, and the residence time in water is short, which limits the efficiency of microalgae carbon fixation, and the performance of microalgae carbon fixation and oil production is significantly improved by introducing zinc porphyrin modified titanium-based metal organic framework (ZnTCPP@Ti-MOFs) nanoparticles.

[0006] In order to achieve the above-mentioned purpose, the technical scheme is adopted in the present application: The present application discloses a preparation method of ZnTCPP@Ti-MOFs nanoparticles for microalgae carbon fixation and oil production, comprising: 1) meso-tetra (4-carboxyphenyl) porphyrin and zinc acetate are added to a N,N-dimethylformamide solution, heated by oil bath, washed until clear, and then freeze-dried to obtain ZnTCPP powder; 2) the ZnTCPP powder prepared in step 1) is added to a mixed solution of methanol and N,N-dimethylformamide, 2-amino terephthalic acid is further added, and then stirred after ultrasonic treatment, tetrabutyl titanate is added, and then hydrothermal reaction, washing and drying are carried out to obtain ZnTCPP@Ti-MOFs nanoparticles for microalgae carbon fixation and oil production.

[0007] Preferably, in step 1), the molar ratio of meso-tetra (4-carboxyphenyl) porphyrin to zinc acetate is (0.1-1):1, the molar ratio of N,N-dimethylformamide solution to Zn is (415-430):1, and the molar ratio of Zn to Ti is (0.1-1):1; The temperature of oil bath heating is 90-110℃, and the time of oil bath heating is 4-6h.

[0008] Preferably, in step 2), the amount ratio of the mixed solution of methanol and N,N-dimethylformamide, 2-amino terephthalic acid and tetrabutyl titanate is (15-30)mL:(0.1-1)g:(0.1-1)mL; In the mixed solution of methanol and N,N-dimethylformamide, the volume ratio of methanol to N,N-dimethylformamide is (5-15):1; The temperature of hydrothermal reaction is 140-160℃, and the time of hydrothermal reaction is 24-72h.

[0009] The present application also discloses ZnTCPP@Ti-MOFs nanoparticles for microalgae carbon fixation and oil production, which are prepared by the above-mentioned preparation method of ZnTCPP@Ti-MOFs nanoparticles for microalgae carbon fixation and oil production.

[0010] The application further discloses the application of the ZnTCPP@Ti-MOFs nanoparticles for carbon fixation and oil production of microalgae in carbon fixation and oil production of microalgae, wherein the ZnTCPP@Ti-MOFs nanoparticles prepared by the preparation method are added into a microalgae culture medium, and a photobioreactor is used to culture under light conditions.

[0011] Preferably, the photobioreactor is a gas-lift photobioreactor, the gas-lift photobioreactor is provided with an aeration device for introducing CO2, and the gas-lift photobioreactor is externally provided with an LED light system for providing necessary light sources for microalgae growth. The microalgae culture medium is an optimized L1 culture medium, and one liter of the optimized L1 culture medium comprises the following components: 1L seawater, 75 g NaNO3, 4.35 g NaH2PO4, 30 g Na2SiO3·9H2O, 2.5 mg CuSO4·5H2O, 23 mg ZnSO4·7H2O, 11.9 mg CoCl·6H2O, 178.1 mg MnCl·4H2O, 19.9 mg Na2MoO4·2H2O, 3.15 g FeCl3·6H2O, 1.29 mg H2SeO3, 2.63 mg NiSO4·6H2O, 1.84 mg Na3VO4, 1.94 mg K2CrO4, 0.2 g B1, 1 mg Biotin and 1 mg B. 12 .

[0012] Preferably, the ZnTCPP@Ti-MOFs nanoparticles are first dispersed in a culture medium solution to obtain an optimized culture medium solution, and then the algal seeds and the optimized culture medium solution are mixed uniformly to prepare a microalgae culture medium solution.

[0013] Further preferably, the algal seeds are first cultured under light in a sterile environment for 5-7 days, then fresh L1 culture medium is added, and then CO2 gas with different volume fractions is introduced for domestication, and finally the algal seeds are transferred to the photobioreactor and the optimized culture medium solution is added. The algal seeds are microalgae, and the initial biomass concentration after inoculation is 0.16-0.17 g / L.

[0014] Further preferably, the domestication method is as follows: The algal seeds are introduced under the condition that the volume concentration of CO2 is 10%, and the aeration is continuously carried out at a flow rate of 20 mL / min, after 10-15 days of culture, 1 / 2 of the algal liquid is discarded, and an equal volume of fresh L1 culture medium is added, and the domestication is continuously carried out for 2-5 cycles to ensure the tolerance of the algal seeds to CO2 with a volume concentration of 10%.

[0015] Preferably, the method for microalgae carbon fixation and oil production under light conditions comprises: filling the steel cylinder with CO2 mixed with air uniformly, the volume concentration of CO2 is 0-10% and does not contain 0%, the inlet rate is 0.01-1.5 L / min, the light intensity is 2000-4000 Lux, and the culture temperature is 23-27 DEG C.

[0016] Compared with the prior art, the present application has the following beneficial effects: The application discloses a preparation method of ZnTCPP@Ti-MOFs nanoparticles for carbon fixation and oil production of microalgae, meso-tetra(4-carboxyphenyl) porphyrin is a planar macrocyclic compound with four carboxylic acid groups, and a stable metal coordination center can be formed by controlling the spatial arrangement of the carboxylic acid groups, thereby providing a binding site for subsequent anchoring of titanium oxide clusters. Zinc acetate is used as a zinc ion source, and the acetate form is beneficial to dissociation in an organic solvent, so that sufficient coordination of zinc ions and porphyrin rings can be realized. The N,N-dimethylformamide solution is used as a high-polarity solvent, and the organic ligand and metal salt can be dissolved simultaneously, so that the crystal growth rate is optimized. The oil bath heating maintains a constant temperature environment through an external heat source, and promotes the formation of coordination bonds and the preliminary growth of crystals. The mixed solution of methanol and N,N-dimethylformamide is used as a reaction medium, and the volume ratio can adjust the hydrolysis speed of titanium ester, balance the formation rate of titanium oxide clusters and the dispersibility of organic ligands. In the process of hydrolysis of tetrabutyl titanate to generate titanium oxide clusters, the molar ratio of Zn to Ti is controlled to ensure the stability of the skeleton structure and retain sufficient active sites. In the organic solvent system, zinc ions preferentially form coordination bonds with nitrogen atoms of the porphyrin ring to generate ZnTCPP precursors with a clear crystal structure. When the precursors are co-hydrolyzed with tetrabutyl titanate in the mixed solvent, titanium oxide clusters form coordination connections with ZnTCPP through carboxylic acid groups, and amino terephthalic acid is used as an auxiliary ligand to fill the skeleton gap. The hydrothermal reaction can fully hydrolyze the titanium ester without damaging the porphyrin structure, and ensure the complete growth of the crystal. The formed composite nanoparticles have a Ti-MOF main frame and a ZnTCPP functional unit, wherein a three-dimensional network constructed by titanium oxide clusters provides a CO2 adsorption channel, and the embedded zinc porphyrin unit can penetrate the microalgae cell membrane to activate the carbonic anhydrase activity. Compared with the prior art, the traditional single-metal MOFs material only improves CO2 adsorption through surface modification, while the application constructs a system with synergistic effect of penetrating channels and active sites through double-metal coordination. Through the step-by-step synthesis strategy, the damage of high temperature to the porphyrin structure is effectively avoided, and the precise positioning of the functional unit is realized through in-situ coordination. Compared with the problem of chlorophyll content reduction caused by the material in the prior art, the stable combination of zinc porphyrin and titanium oxide clusters reduces the free metal ions, thereby maintaining the normal metabolic function of the microalgae cells. The continuous and stable supply of CO2 in the microalgae culture system is realized, and the enzyme activity of the intracellular carbon metabolism is simultaneously improved. The formed hierarchical porous structure can efficiently enrich CO2 molecules outside the cells, and the zinc porphyrin unit penetrates into the cells to activate the carbonic anhydrase catalytic HCO3 - conversion, solving the problem that the physical adsorption and biological conversion links are disconnected in the traditional technology. The step-by-step assembly of organic-inorganic components in the material preparation process ensures the stability of the crystal structure and the integrity of the biological active site, maintains a high carbon fixation efficiency, and significantly improves the oil synthesis rate.

[0017] Further, Ti-MOF has extremely strong CO2 adsorption capacity, which can effectively enrich carbon dioxide in the environment and ensure sufficient carbon source supply. Even under low concentration CO2 conditions, Ti-MOF can efficiently capture and release CO2, providing a continuous and stable carbon source for microalgae. ZnTCPP (zinc porphyrin) can enter the microalgae cell interior, improve the activity of key enzymes (such as carbonic anhydrase), and promote the efficiency of carbon fixation process and oil synthesis pathway. By enhancing enzyme activity, ZnTCPP promotes the absorption and conversion of CO2 by microalgae, increases the photosynthesis rate and oil yield, and thus improves the overall carbon fixation efficiency. As an organic ligand, ZnTCPP can enhance the activity of enzymes in microalgae cells without causing significant toxicity to the cells, showing good biocompatibility. Compared with some inorganic nanoparticles, ZnTCPP@Ti-MOFs have less impact on microalgae cells and do not interfere with their normal metabolic processes, ensuring the healthy growth of microalgae.

[0018] Further, when the TCPP / Zn molar ratio is 0.25:1 and the Zn / Ti metal molar ratio is 0.06:1, the obtained ZnTCPP@Ti-MOFs nanoparticles have the highest specific surface area and pore volume, and at the same time have a certain number of micropores and mesopores, with the most optimal pore characteristics among all materials.

[0019] The application further discloses the ZnTCPP@Ti-MOFs nanoparticles for microalgae carbon fixation and oil production prepared by the preparation method, wherein the nanoparticles are prepared by the following steps: reacting meso-tetra(4-carboxyphenyl) porphyrin and zinc acetate in N,N-dimethylformamide to generate a zinc porphyrin precursor, and then performing hydrothermal synthesis on the zinc porphyrin precursor and tetrabutyl titanate in a mixed solvent. The zinc porphyrin can enter the microalgae cell interior through penetration, activate carbonic anhydrase activity, and promote the conversion of carbon dioxide into bicarbonate. The titanium-based metal organic framework is a porous crystalline material formed by titanium-oxygen clusters and organic ligands through coordination bonds, and the framework has hierarchical pore structure and can enrich carbon dioxide molecules in the gas phase through physical adsorption and chemical action. The zinc porphyrin and amino terephthalic acid jointly participate in the coordination process of the titanium-oxygen cluster, so that the nanoparticles have high carbon dioxide adsorption capacity and intracellular enzyme activity regulation capacity. The zinc porphyrin forms a coordination bond with the titanium-oxygen cluster through a carboxylic acid group and is embedded in the skeleton of the titanium-based metal organic framework to form a stable composite structure. In the process of microalgae cultivation, the outer surface pores of the titanium-based metal organic framework preferentially adsorb carbon dioxide in the environment, and the gas molecules are transmitted to the surface of the microalgae cell through the mesoporous channel; at the same time, the zinc porphyrin is dissociated from the framework and penetrates the cell membrane to combine with intracellular carbonic anhydrase, thereby accelerating the carbon dioxide hydration reaction to generate bicarbonate ions to provide sufficient substrate for the Calvin cycle. The internal and external synergistic mechanism enables the microalgae to fix more carbon sources in unit time and tilt the photosynthesis products to the lipid synthesis path. Compared with the prior art, the traditional metal organic framework material only improves the local concentration of carbon dioxide through surface adsorption, but cannot intervene in the intracellular metabolic process; and the single zinc-based material can activate enzyme activity, but lacks sustained carbon supply capacity. The application integrates the carbon dioxide capture and metabolic regulation functions in a single nanoparticle through a double-ligand design, thereby overcoming the spatial separation problem of functional modules. In addition, the acid resistance of the titanium-based skeleton avoids the collapse of the structure in a high-pressure carbon dioxide environment, and the titanium-based material has better chemical stability than the iron-based or zinc-based material. The titanium-based metal organic framework continuously supplies concentrated carbon dioxide, reduces the mass transfer limitation from the gas phase to the liquid phase, the zinc porphyrin optimizes the intracellular enzymatic reaction kinetics, and promotes the diversion of photosynthetic products to the lipid synthesis direction. The synergistic effect of the two enables the microalgae to maintain normal growth while significantly increasing the volume ratio of liposomes in the cell, and does not cause chloroplast structure damage or antioxidant system overload.

[0020] Further, the ZnTCPP@Ti-MOFs nanoparticles are added to a photobioreactor, and when the concentration is 10 ppm, the photosynthesis efficiency, growth rate, carbon fixation efficiency and lipid production rate of the microalgae cells are the highest in all systems.

[0021] The application also discloses application of the ZnTCPP@Ti-MOFs nanoparticles prepared by the preparation method in microalgae carbon fixation and oil production, and the ZnTCPP@Ti-MOFs nanoparticles are a dual-functional nanomaterial formed by compounding zinc porphyrin and titanium-based metal organic framework, and can be realized by hydrothermal reaction of zinc porphyrin coordination to titanium oxygen cluster nodes and co-coordination with amino terephthalic acid. CO2 is adsorbed and enriched through the pore structure of the titanium-based skeleton, and at the same time, zinc porphyrin components penetrate into microalgae cells to activate metabolic enzyme activity. In the microalgae culture process, the ZnTCPP@Ti-MOFs nanoparticles are uniformly dispersed in the culture medium. The titanium-based metal organic framework captures CO2 molecules in the gas phase through the mesoporous structure, and continuously releases dissolved inorganic carbon in the liquid phase, overcoming the problem of low CO2 mass transfer efficiency in the traditional culture system. The zinc porphyrin component enters the microalgae inside through the cell membrane, and after combining with carbonic anhydrase, the catalytic activity of HCO3 ⁻ The gas distribution device arranged in the photobioreactor ensures sufficient contact between CO2 and the culture solution, and periodic light regulation promotes microalgae to efficiently utilize the enriched carbon source to synthesize oil precursors in the light period, and to complete the assembly and accumulation of triglycerides in the dark period. Compared with the prior art, the traditional method uses a single metal organic framework to only improve the CO2 adsorption amount, but cannot simultaneously activate the intracellular metabolic pathway. The Zn / Fe MOFs nanoparticles promote inorganic carbon conversion, but lack regulation of lipid synthesis enzymes. The application realizes the synergistic effect of extracellular CO2 enrichment and intracellular metabolic enhancement through the dual-functional nanomaterial, and the gas-light coupling design of the photobioreactor matches the CO2 supply rate with the photosynthetic rhythm of microalgae. The CO2 fixation amount per unit culture volume is increased while the intracellular oil accumulation is increased under the premise of maintaining the normal growth of microalgae. The titanium-based skeleton of the nanoparticles avoids the dramatic fluctuation of the pH value of the culture solution in a high-concentration CO2 environment, and the enzyme activation effect of zinc porphyrin ensures that the carbon flow is distributed to the lipid synthesis pathway, solving the problem that the carbon fixation and oil production efficiency cannot be simultaneously improved in the traditional technology. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is a device diagram of the gas-lift photobioreactor of the application.

[0023] Figure 2 It is a synthesis route diagram of the ZnTCPP@Ti-MOFs nanoparticles for microalgae carbon fixation and oil production of the application.

[0024] Figure 3 It is a diagram of the change of the cell density of microalgae in the system with the addition of different concentrations of ZnTCPP@Ti-MOFs nanoparticles for microalgae carbon fixation and oil production with time.

[0025] Figure 4The figure of the change of the biomass of the microalgae in the system added with different concentrations of ZnTCPP@Ti-MOFs nanoparticles for carbon fixation and oil production of microalgae over time. DETAILED DESCRIPTION

[0026] The technical solutions of the present application will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0027] In the present application, all the embodiments and preferred embodiments mentioned in the present application can be combined to form new technical solutions, unless otherwise specified.

[0028] In the present application, all the technical features and preferred features mentioned in the present application can be combined to form new technical solutions, unless otherwise specified.

[0029] In the present application, the percentage (%) or the part refers to the weight percentage or the weight part of the composition, unless otherwise specified.

[0030] In the present application, the components or the preferred components involved can be combined to form new technical solutions, unless otherwise specified.

[0031] In the present application, unless otherwise specified, the numerical range "a~b" represents a shorthand notation for any real number combination between a and b, wherein a and b are both real numbers. For example, the numerical range "6~22" represents that all the real numbers between "6~22" have been listed herein, and "6~22" is only a shorthand notation for these numerical combinations.

[0032] The lower limit and the upper limit of the range disclosed in the present application can be one or more lower limits and one or more upper limits, respectively.

[0033] In the present application, the term "and / or" used herein refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0034] In the present application, unless otherwise specified, each reaction or operation step can be sequentially performed or performed according to the sequence. Preferably, the reaction method herein is sequentially performed.

[0035] Unless otherwise specified, the professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. In addition, any method or material similar or equivalent to the described content can also be applied in the present application.

[0036] The present invention provides a method for promoting carbon fixation and oil production in microalgae using ZnTCPP@Ti-MOFs nanoparticles. ZnTCPP@Ti-MOFs nanoparticles are added to a microalgae culture medium, and the microalgae are cultured under light conditions using a photobioreactor. The carbon fixation and oil production capacity of the microalgae are then evaluated. The ZnTCPP@Ti-MOFs nanoparticles are a dual-ligand Ti-based metal-organic framework prepared by in-situ introduction of zinc porphyrin into the Ti-based framework by sharing the coordination nodes of the titanium oxide cluster with 2-aminoterephthalic acid (NH2BDC).

[0037] The present invention cultivates microalgae in an airlift photobioreactor. The microalgae culture medium is an optimized L1 culture medium. The microalgae culture medium is placed in the airlift photobioreactor. The airlift photobioreactor is provided with an aeration device for introducing CO2. The outside of the airlift photobioreactor is provided with an LED lighting system that provides the necessary light source for the growth of microalgae.

[0038] The optimized L1 medium formulation consists of the following specific components per liter: Seawater 1L, 75 g NaNO3, 4.35 g NaH2PO4, 30 g Na2SiO3·9H2O, 2.5 mg CuSO4·5H2O, 23 mg ZnSO4·7H2O, 11.9 mg CoCl·6H2O, 178.1 mg MnCl·4H2O, 19.9 mg Na2MoO4·2H2O, 3.15 gFeCl3·6H2O, 1.29 mg H2SeO3, 2.63 mg NiSO4·6H2O, 1.84 mg Na3VO4, 1.94 mg K2CrO4, 0.2 gB1, 1 mg Biotin, 1 mg B 12 .

[0039] ZnTCPP@Ti-MOFs nanoparticles were added to the microalgae culture medium in the following form: First, ZnTCPP@Ti-MOFs nanoparticles are dispersed in the culture medium solution to obtain an optimized culture medium solution; then the algae seeds and the optimized culture medium solution are evenly mixed to form a microalgae solution.

[0040] The algae were cultured in sterile Erlenmeyer flasks under light for 5 to 7 days. As the color of the microalgae became darker, fresh L1 culture medium was added. Then, CO2 gas with different volume fractions was introduced for acclimatization. Finally, the microalgae were transferred to a photobioreactor and the optimized L1 culture medium solution was added.

[0041] The algae were acclimated by introducing CO2 gas with different volume fractions as follows: The algal species was introduced under the condition of 10% (v:v) CO2 concentration, and aeration was carried out at a flow rate of 20 mL / min. After 10-15 days of culture, 1 / 2 of the algal liquid was discarded, and an equal volume of fresh medium was added, and continuous acclimation was carried out for 2-5 cycles to ensure the tolerance of the algal species to 10% (v:v) CO2.

[0042] The algal species was Nannochloropsis, purchased from the Algal Seed Bank of Xiamen University, and the initial biomass concentration after inoculation was 0.16-0.17 g / L. The culture period of the microalgae was 10-15 days.

[0043] The ZnTCPP@Ti-MOFs nanoparticles were synthesized by the following method: S1. Take the meso-tetra (4-carboxyphenyl) porphyrin (TCPP) and zinc acetate and add them to a N,N-dimethylformamide (DMF) solution, transfer the reactants to an oil bath in a round-bottom flask, then wash with deionized water until the filtrate is clear, and freeze-dry to obtain purple ZnTCPP powder.

[0044] S2. Take the purple ZnTCPP powder obtained in S1 and add it to a mixed solution of methanol and DMF, then add NH2BDC, ultrasonic, then stir, then add tetrabutyl titanate, transfer the mixture to a reaction kettle, and react, then wash the obtained reaction product with methanol and dry it, and the ZnTCPP@Ti-MOFs nanoparticles are obtained.

[0045] In the ZnTCPP powder, the molar ratio of TCPP to zinc acetate is (0.1-1):1, the molar ratio of DMF to Zn is (415-430):1, and the molar ratio of Zn to Ti is (0.1-1):1.

[0046] In S1, the oil bath temperature is 90-110℃, and the oil bath time is 4-6h; in S2, the hydrothermal reaction temperature is 140-160℃, and the hydrothermal reaction time is 24-72h.

[0047] The microalgae were cultured under light conditions to produce oil, and the method was as follows: CO2 and air were mixed uniformly at a certain ratio, the volume concentration of CO2 was 0-10% and did not include 0%, the inlet rate of the mixed gas was 0.01-1.5 L / min, the intensity of the light condition was 2000-5000 Lux, and the culture temperature was 23-27℃.

[0048] The application introduces zinc porphyrin into the Ti-based framework in situ by sharing the coordination nodes of titanium-oxygen clusters with NH2BDC, preparing a dual-ligand Ti-based metal organic framework to enhance the carbon fixation and oil production performance of microalgae. Specifically, the Ti-MOF has extremely strong CO2 adsorption capacity, can effectively enrich carbon dioxide in the environment, and ensure sufficient carbon source supply; ZnTCPP can enter the microalgae cell interior, improve the activity of key enzymes, and promote the efficiency of the carbon fixation process and the oil synthesis path. In addition, the method realizes automatic stable CO2 supply, reduces the subsequent investment of manpower and material resources, and can maintain high carbon fixation and oil production performance even under high CO2 concentration conditions. In summary, the application not only provides a new solution for microalgae carbon fixation and biodiesel production, but also shows broad application prospects in addressing climate change and promoting sustainable development, achieving the purpose of the application.

[0049] To make the purpose, technical solutions and advantages of the embodiments of the application clearer, the technical solutions in the embodiments of the application will be described clearly and completely below in conjunction with the drawings in the embodiments of the application. Obviously, the described embodiments are only a part of the embodiments of the application, rather than all the embodiments. The components of the embodiments of the application described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the application provided in the drawings is not intended to limit the scope of the claimed application, but only represents selected embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the protection of the application.

[0050] Embodiment 1 (1) Preparation of ZnTCPP@Ti-MOFs nanoparticles Take 60 mg of TCPP (0.076 mmol) and 67 mg of zinc acetate (0.304 mmol) and add them to a 10 mL DMF (0.1287 mol) solution. Transfer the reaction to a round-bottom flask and heat in an oil bath at 110°C for 4 h. Then wash with deionized water until the filtrate is clear, and freeze-dry for 12 h to obtain purple ZnTCPP powder.

[0051] Take 90 mg of ZnTCPP (0.138 mmol) powder and add it to a mixture of 2 mL of methanol and 8 mL of DMF. Then add 0.56 g of NH2BDC, sonicate, and then stir. Then add 0.6 mL of tetrabutyl titanate, transfer the mixture to a reaction kettle, and react at 160°C for 24 h. Wash the obtained reaction with methanol and dry to obtain the ZnTCPP@Ti-MOFs nanoparticles.

[0052] (2) Start-up and operation of the system An airlift photobioreactor was used for microalgae cultivation experiments. The reactor body had a height of 30 cm, an inner diameter of 8 cm, and a thickness of 5 mm. The reactor was made of acrylic glass.

[0053] Step 1: Inoculation of microalgae. ZnTCPP@Ti-MOFs nanoparticles were dispersed in 1 L of culture medium at concentrations of 10, 15, 20, 25, and 50 ppm, respectively. A blank control group without ZnTCPP@Ti-MOFs nanoparticles was used to obtain six optimized culture medium solutions. The algae seed and optimized culture medium solutions were then mixed evenly to form the microalgae solutions. The initial biomass concentration of the microalgae in each experimental group was 0.17 g / L. Step 2: Aeration. Aeration of 10% CO2 was introduced from the bottom of the culture system at a flow rate of 1.5 L / min. Culture was continued for 10 days. Step 3: Operation. The light sources on both sides were turned on, with an incident light intensity of 4000 Lux. A 12h / 2h photoperiod was used, and the ambient temperature was maintained at 27°C.

[0054] (3) Testing of comprehensive system performance Take a sample every 24 hours and test the pH and absorbance OD of the solution 680 , carbon fixation efficiency and other parameters. After the cultivation, algae powder was collected to test its oil yield. The system operation cycle was 14 days.

[0055] The test related performance and shape are as follows: Table 1 Cell density and biomass of microalgae at different ZnTCPP@Ti-MOFs concentrations

[0056] Table 1 shows the cell density and biomass of microalgae at different ZnTCPP@Ti-MOFs concentrations. It can be seen from the table that the cell density and biomass of microalgae are the highest when the ZnTCPP@Ti-MOFs concentration is 10 ppm.

[0057] Carbon fixation efficiency of microalgae at different ZnTCPP@Ti-MOFs concentrations: None: 0.119 g CO2 / L / d; 10ppm: 0.210 g CO2 / L / d; 15ppm: 0.153 g CO2 / L / d; 20ppm: 0.133 g CO2 / L / d; 25ppm: 0.145 g CO2 / L / d; 50ppm: 0.127 g CO2 / L / d.

[0058] Oil yield of microalgae at different ZnTCPP@Ti-MOFs concentrations: None: 36.94%; 10 ppm: 61.63%; 15 ppm: 52.99%; 20 ppm: 40.38%; 25 ppm: 38.69%; 50 ppm: 38.47%.

[0059] Example 2 (1) Preparation of ZnTCPP@Ti-MOFs nanoparticles 30 mg of TCPP (0.038 mmol) and 67 mg of zinc acetate (0.304 mmol) were added to a 10 mL DMF (0.1287 mol) solution, and the reaction was transferred to a round-bottom flask and heated in an oil bath at 90°C for 6 h, followed by washing with deionized water until the filtrate was clear, and freeze-drying for 12 h to obtain a purple ZnTCPP powder.

[0060] 90 mg of ZnTCPP (0.138 mmol) powder was added to a mixture of 2 mL of methanol and 8 mL of DMF, and then 0.56 g of NH2BDC was added. After ultrasonic stirring, 1.2 mL of tetrabutyl titanate was added, and the mixture was transferred to a reaction kettle and reacted at 140°C for 72 h. The resulting reaction was washed with methanol and dried to obtain the final material, which was named MOFs-1.

[0061] (2) Start-up and operation of the system The gas-lift photobioreactor was used for microalgae cultivation experiments, with a reactor body height of 30 cm, an internal diameter of 8 cm, a thickness of 5 mm, and a reactor material of acrylic organic glass.

[0062] First step: inoculate microalgae. First, 10 ppm MOFs-1 nanoparticles were dispersed in 1 L of culture medium solution to obtain an optimized culture medium solution; then the algal seeds and the optimized culture medium solution were mixed evenly to form the microalgae solution, and the initial biomass concentration of the microalgae in each experimental group was 0.16 g / L. Second step: aeration. With a gas flow rate of 0.01 mL / min, 10% CO2 gas was introduced from the bottom of the culture system, and continuous cultivation was carried out for 15 days. Third step: operation. Turn on the light sources on both sides, with an incident light intensity of 2000 Lux, and use a 12h / 2h light cycle, with an environmental temperature of 23°C.

[0063] (3) Test of the comprehensive performance of the system Every 24 h, test the pH, absorbance OD 680 , and carbon fixation efficiency of the solution, and after the cultivation is completed, collect the algal powder to test the oil yield. The system operation period is 14 days.

[0064] Test the related performance and shape as follows: Cell density: 26.778 x 10 6 cell / mL; Biomass: 1.037 g / L; Carbon fixation efficiency: 0.189 g CO2 / L / d; Oil yield: 52.31%.

[0065] Example 3 (1) Preparation of ZnTCPP@Ti-MOFs nanoparticles 90 mg of TCPP (0.114 mmol) and 67 mg of zinc acetate (0.304 mmol) were added to a 10 mL DMF (0.1287 mol) solution, and the reaction was transferred to a round-bottom flask and heated in an oil bath at 100°C for 5 h, followed by washing with deionized water until the filtrate was clear, and freeze-drying for 12 h to obtain purple ZnTCPP powder.

[0066] 90 mg of ZnTCPP (0.138 mmol) powder was added to a mixture of 2 mL of methanol and 8 mL of DMF, and then 0.56 g of NH2BDC was added. After ultrasonic stirring, 1.8 mL of tetrabutyl titanate was added, and the mixture was transferred to a reaction kettle and reacted at 150°C for 24 h. The resulting reaction was washed with methanol and dried to obtain the final material, which was named MOFs-2.

[0067] (2) Start-up and operation of the system The microalgae cultivation experiment was carried out using a gas-lift photobioreactor, with a reactor body height of 30 cm, an internal diameter of 8 cm, a thickness of 5 mm, and a reactor material of acrylic organic glass.

[0068] First step: inoculation of microalgae. 10 ppm of MOFs-2 nanoparticles were dispersed in 1 L of culture medium solution to obtain an optimized culture medium solution; then the algal seeds and the optimized culture medium solution were mixed uniformly to prepare the microalgae solution, and the initial biomass concentration of the microalgae in each experimental group was 0.16 g / L. Second step: aeration. With a gas flow rate of 20 mL / min, 10% CO2 gas was introduced from the bottom of the culture system, and continuous cultivation was carried out for 14 days. Third step: operation. The light sources on both sides were turned on, the incident light intensity was 4000 Lux, and a light cycle of 12 h / 2 h was adopted, with an environmental temperature of 25°C.

[0069] (3) Test of comprehensive performance of the system Samples were taken every 24 h, and parameters such as pH, absorbance OD 680 , carbon fixation efficiency, etc. of the solution were tested, and after the cultivation was completed, the algal powder was collected to test its oil yield, and the system operation cycle was 28 days.

[0070] The related performance and shape were tested as follows: Cell density: 25.231 x 10 6cell / mL; Biomass: 0.997 g / L; Carbon fixation efficiency: 0.124 g CO2 / L / d; Oil yield: 44.24%.

[0071] Example 4 (1) Preparation of ZnTCPP@Ti-MOFs nanoparticles 120 mg of TCPP (0.152 mmol) and 67 mg of zinc acetate (0.304 mmol) were added to a 10 mL DMF (0.1287 mol) solution, and the reaction was transferred to a round-bottom flask and heated in an oil bath at 100°C for 5 h, followed by washing with deionized water until the filtrate was clear, and freeze-drying for 12 h to obtain a purple ZnTCPP powder.

[0072] 90 mg of ZnTCPP (0.138 mmol) powder was added to a mixture of 2 mL of methanol and 8 mL of DMF, and then 0.56 g of NH2BDC was added. After ultrasonic stirring, 2.4 mL of tetrabutyl titanate was added, and the mixture was transferred to a reaction kettle and reacted at 150°C for 24 h. The resulting reaction was washed with methanol and dried to obtain the final material, which was named MOFs-3.

[0073] (2) Start-up and operation of the system The gas-lift photobioreactor was used for microalgae cultivation experiments, with a reactor body height of 30 cm, an internal diameter of 8 cm, a thickness of 5 mm, and a reactor material of acrylic organic glass.

[0074] First step: inoculate microalgae. 10 ppm of MOFs-2 nanoparticles were dispersed in 1 L of culture medium solution to obtain an optimized culture medium solution; then the algal seeds and the optimized culture medium solution were mixed uniformly to prepare the microalgae solution, and the initial biomass concentration of the microalgae in each experimental group was 0.16 g / L. Second step: aeration. With a gas flow rate of 20 mL / min, 10% CO2 gas was introduced from the bottom of the culture system, and continuous cultivation was carried out for 14 days. Third step: operation. Turn on the light sources on both sides, with an incident light intensity of 4000 Lux, and use a light cycle of 12 h / 2 h, with an environmental temperature of 25°C.

[0075] (3) Test of comprehensive performance of the system Samples were taken every 24 h to test the pH, absorbance OD 680 , carbon fixation efficiency, etc. of the solution, and after the cultivation was completed, the algal powder was collected to test its oil yield. The system operation cycle was 14 days.

[0076] The relevant performance and shape were tested as follows: Cell density: 24.901 x 106 cell / mL; Biomass: 0.982 g / L; Carbon fixation efficiency: 0.120 g CO2 / L / d; Oil yield: 39.78%.

[0077] Example 5 (1) Preparation of ZnTCPP@Ti-MOFs nanoparticles 240 mg of TCPP (0.304 mmol) and 67 mg of zinc acetate (0.304 mmol) were added to a 10 mL DMF (0.1287 mol) solution, and the reaction was transferred to a round-bottom flask and heated in an oil bath at 100°C for 5 h. Then, the filtrate was washed with deionized water until it was clear, and freeze-dried for 12 h to obtain a purple ZnTCPP powder.

[0078] 90 mg of ZnTCPP (0.138 mmol) powder was added to a mixture of 2 mL of methanol and 8 mL of DMF, and then 0.56 g of NH2BDC was added. After ultrasonic stirring, 2.4 mL of tetrabutyl titanate was added, and the mixture was transferred to a reaction kettle and reacted at 150°C for 24 h. The resulting reaction was washed with methanol and dried to obtain the final material, which was named MOFs-4.

[0079] (2) Start-up and operation of the system The gas-lift photobioreactor was used for microalgae cultivation experiments, with a reactor body height of 30 cm, an internal diameter of 8 cm, a thickness of 5 mm, and a reactor material of acrylic organic glass.

[0080] First step: inoculate microalgae. 10 ppm of MOFs-2 nanoparticles were dispersed in 1 L of culture medium solution to obtain an optimized culture medium solution; then the algal seeds and the optimized culture medium solution were mixed evenly to prepare the microalgae solution, and the initial biomass concentration of the microalgae in each experimental group was 0.16 g / L. Second step: aeration. With a gas flow rate of 20 mL / min, 10% CO2 gas was introduced from the bottom of the culture system, and continuous cultivation was carried out for 14 days. Third step: operation. Turn on the light sources on both sides, with an incident light intensity of 4000 Lux, and use a light cycle of 12 h / 2 h, with an environmental temperature of 25°C.

[0081] (3) Test of comprehensive performance of the system Samples were taken every 24 h to test the pH, absorbance OD 680 , carbon fixation efficiency, and other parameters of the solution. After the cultivation was completed, the algal powder was collected to test its oil yield, and the system operation cycle was 14 days.

[0082] The related performance and shape were tested as follows: Cell density: 19.256×10 6 cell / mL; Biomass: 0.782 g / L; Carbon sequestration efficiency: 0.091 g CO2 / L / d; Oil yield: 23.14%.

[0083] Figure 1 This diagram shows the setup of the airlift photobioreactor of the present invention. As can be seen, the cylindrical, transparent main tank serves as the reaction or treatment chamber, capable of holding liquids or gases. Side inlets and outlets (with ball valves) control fluid flow. The blue device at the bottom is an aerator.

[0084] Figure 2 This is a synthetic route for the ZnTCPP@Ti-MOFs nanoparticles used for carbon sequestration and oil production in microalgae. The figure shows two main routes for the synthesis of the ZnTCPP / TiMOF composite. First, using tetraethoxytitanium (Ti(OC2H5)4) as the metal source and 2-aminoterephthalic acid (NH2-BDC) as the organic ligand, an amino-modified MIL-125 titanium-based metal-organic framework (TMOF) is synthesized via a solvothermal method in a solvent such as N,N-dimethylformamide (DMF). Second, tetrakis(4-carboxyphenyl)porphyrin (TCPP) and zinc acetate are stirred and reacted in a solvent such as ethanol or DMF. The ZnTCPP / TiMOF composite is then washed and dried.

[0085] Figure 3 A graph showing the change in cell density of microalgae over time in a system containing different concentrations of ZnTCPP@Ti-MOFs nanoparticles for carbon fixation and oil production in microalgae according to the present invention. As can be seen from the figure, the three-dimensional growth curve comprehensively displays the change in cell density over time under different treatment concentration conditions, intuitively showing that high-concentration treatment significantly inhibits cell growth and survival in a dose-dependent manner, providing important data basis for evaluating the effects of treatment agents on cell growth.

[0086] Figure 4 A graph shows the change in microalgae biomass over time in a system containing different concentrations of ZnTCPP@Ti-MOFs nanoparticles for microalgae carbon fixation and oil production, as described in the present invention. The data in the graph indicate that cell dry weight increases with culture time but is significantly affected by the dose of the treated substance. The higher the treatment concentration, the more strongly cell growth and biomass accumulation are inhibited. The untreated group had the highest dry weight, while the 500 ppm group had the lowest, demonstrating a clear dose-effect relationship. This result intuitively reflects the negative impact of the treatment agent on organism growth and provides a quantitative reference for practical applications. In summary, the application discloses a method for significantly improving the carbon fixation and oil production performance of microalgae by introducing ZnTCPP@Ti-MOFs into microalgae, and a preparation process thereof. The method comprises introducing ZnTCPP@Ti-MOFs nanoparticles into the microalgae culture medium, and using a gas-lift photobioreactor to culture the microalgae under a 12h / 12h light cycle. The application utilizes the high-efficiency CO2 capture characteristics of ZnTCPP@Ti-MOFs nanoparticles to perform self-assembly on the surface of microalgae, which can significantly improve the CO2 fixation efficiency of microalgae and the accumulation amount of intracellular oil. Experimental results show that the microalgae treated by the method of the application exhibit higher photosynthesis rate and oil content under light conditions, while maintaining good biological stability and environmental adaptability. The application not only provides an innovative technical path for microalgae carbon fixation and biodiesel production, but also shows broad application prospects in addressing climate change and energy crisis, and is particularly suitable for large-scale industrial application and environmental remediation projects.

[0087] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the application, and not to limit them; although the application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the application.

Claims

1. A method for preparing ZnTCPP@Ti-MOFs nanoparticles for carbon fixation and oil production in microalgae, characterized in that: include: 1) Add meso-tetrakis(4-carboxyphenyl)porphyrin and zinc acetate to N,N-dimethylformamide solution, heat in an oil bath, wash until clear, and freeze-dry to obtain ZnTCPP powder; 2) The ZnTCPP powder prepared in step 1) is added to a mixed solution of methanol and N,N-dimethylformamide, followed by 2-aminoterephthalic acid. The mixture is ultrasonically stirred and tetrabutyl titanate is added. The mixture is subjected to a hydrothermal reaction, washed, and dried to obtain ZnTCPP@Ti-MOFs nanoparticles for carbon fixation and oil production in microalgae.

2. The method for preparing ZnTCPP@Ti-MOFs nanoparticles for microalgae carbon fixation and oil production according to claim 1, characterized in that: In step 1), the molar ratio of meso-tetrakis(4-carboxyphenyl)porphyrin to zinc acetate is (0.1-1):1, the molar ratio of N,N-dimethylformamide solution to Zn is (415-430):1, and the molar ratio of Zn to Ti is (0.1-1):1; The oil bath heating temperature is 90-110° C., and the oil bath heating time is 4-6 hours.

3. The method for preparing ZnTCPP@Ti-MOFs nanoparticles for microalgae carbon fixation and oil production according to claim 1, characterized in that: In step 2), the ratio of the mixed solution of methanol and N,N-dimethylformamide, 2-aminoterephthalic acid and tetrabutyl titanate is (15-30) mL: (0.1-1) g: (0.1-1) mL; In the mixed solution of methanol and N,N-dimethylformamide, the volume ratio of methanol to N,N-dimethylformamide is (5-15):1; The temperature of the hydrothermal reaction is 140-160° C., and the time of the hydrothermal reaction is 24-72 hours.

4. A ZnTCPP@Ti-MOFs nanoparticle for carbon fixation and oil production in microalgae, characterized in that: The ZnTCPP@Ti-MOFs nanoparticles for microalgae carbon fixation and oil production are prepared by the preparation method of any one of claims 1 to 3.

5. The use of ZnTCPP@Ti-MOFs nanoparticles for microalgae carbon fixation and oil production prepared by the preparation method of ZnTCPP@Ti-MOFs nanoparticles for microalgae carbon fixation and oil production according to any one of claims 1 to 3 in microalgae carbon fixation and oil production, characterized in that: ZnTCPP@Ti-MOFs nanoparticles were added to the microalgae culture medium and cultured under light conditions using a photobioreactor.

6. The use of ZnTCPP@Ti-MOFs nanoparticles for microalgae carbon fixation and oil production in microalgae carbon fixation and oil production according to claim 5, characterized in that: The photobioreactor is an airlift photobioreactor; an aeration device for introducing CO2 is provided in the airlift photobioreactor; an LED lighting system is provided outside the airlift photobioreactor to provide the necessary light source for the growth of microalgae; The microalgae culture medium is an optimized L1 culture medium; each liter of the optimized L1 culture medium includes the following components: 1 L of seawater, 75 g NaNO3, 4.35 g NaH2PO4, 30 g Na2SiO3•9H2O, 2.5 mg CuSO4•5H2O, 23 mg ZnSO4•7H2O, 11.9 mg CoCl•6H2O, 178.1 mg MnCl•4H2O, 19.9 mg Na2MoO4•2H2O, 3.15 g FeCl3•6H2O, 1.29 mg H2SeO3, 2.63 mg NiSO4·6H2O, 1.84 mg Na3VO4, 1.94 mg K2CrO4, 0.2 g B1, 1 mg Biotin, and 1 mg B 12 .

7. The use of ZnTCPP@Ti-MOFs nanoparticles for microalgae carbon fixation and oil production in microalgae carbon fixation and oil production according to claim 5, characterized in that: First, ZnTCPP@Ti-MOFs nanoparticles are dispersed in a culture medium solution to obtain an optimized culture medium solution; then, the algae seeds and the optimized culture medium solution are evenly mixed to form a microalgae culture medium solution.

8. The use of ZnTCPP@Ti-MOFs nanoparticles for carbon fixation and oil production in microalgae according to claim 7, characterized in that: The algae were first cultured in a sterile environment under light for 5-7 days, then fresh L1 medium was added, and then CO2 gas with different volume fractions was introduced for acclimatization. Finally, the algae were transferred to a photobioreactor and the optimized culture medium solution was added. The algae species is Nannochloropsis, and the initial biomass concentration after inoculation is 0.16-0.17 g / L.

9. The use of ZnTCPP@Ti-MOFs nanoparticles for microalgae carbon fixation and oil production in microalgae carbon fixation and oil production according to claim 7, characterized in that: The method of described domestication is: Introduce algae species under conditions of a CO2 volume concentration of 10%, and continuously aerate at a flow rate of 20 mL / min. After culturing for 10 to 15 days, discard 1 / 2 of the algae liquid and re-add an equal volume of fresh L1 culture medium. Repeat acclimation for 2 to 5 cycles to ensure the tolerance of the algae species to a CO2 volume concentration of 10%.

10. The use of ZnTCPP@Ti-MOFs nanoparticles for carbon fixation and oil production in microalgae according to claim 5, characterized in that: The method for carbon fixation and oil production by microalgae under light conditions includes: mixing CO2 and air evenly and then filling them into a cylinder, the volume concentration of CO2 is 0~10% and does not include 0%, the air intake rate is 0.01~1.5 L / min, the light intensity is 2000~4000 Lux, and the culture temperature is 23~27℃.

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