Cesium ion doped carbon nitride catalyst as well as preparation method and application thereof
Through the modification of the cesium ion doped carbon nitride catalyst, the problem of limited light absorption range, high photogenerated carrier recombination rate and insufficient catalytic stability of the g-C3N4 photocatalyst during the reduction of CO2 to formic acid is solved, and the efficient utilization of visible light and the stability of the catalyst are achieved, and the efficiency of CO2 reduction to formic acid is improved.
Patent Information
- Application Number
- CN202510510604.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-23
- Publication Date
- 2025-07-11
AI Technical Summary
During the reduction of CO2 to formic acid, the existing graphite phase carbon nitride (g-C3N4) photocatalysts have problems such as limited light absorption range, high photogenerated carrier recombination rate, small specific surface area and insufficient catalytic stability, especially in the low photo-enzyme synergy efficiency and poor doping uniformity, resulting in performance attenuation.
The heat-polycondensation method is used to prepare a cesium ion-doped carbon nitride catalyst. The specific surface area is increased by cesium ion doping, cyano and hydroxyl functional groups are formed, the separation of photogenerated electron-hole pairs is improved, and the fixation is carried out with formic acid dehydrogenase, and the performance of photoenzyme coupling reduction of CO2 to formic acid is optimized.
It improves the utilization effect of visible light, exposes more active sites, enhances the stability of the catalyst and the performance of photoenzyme-coupled reduction of CO2 as formic acid, and has good formic acid-producing properties of photoenzyme-coupled reduction of CO2.
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Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of material preparation, and particularly relates to a cesium ion-doped carbon nitride catalyst, a preparation method thereof, and an application thereof. Background Art
[0002] Since the Industrial Revolution, the extensive use of fossil fuels has led to a sharp rise in the global CO2 concentration. Data from the World Meteorological Organization (WMO) shows that the average atmospheric CO2 concentration in 2022 has exceeded 413.2 ± 0.2 ppm, nearly 49% higher than the pre-industrial (1750) level, becoming the core cause of intensified greenhouse effects, frequent extreme weather, and ecosystem imbalance. To address this crisis, the development of efficient and sustainable CO2 conversion technologies has become a global consensus. Current methods include chemical catalysis, electrochemical reduction, and enzyme catalysis, etc. Among them, although chemical and electrochemical methods can achieve CO2 conversion, they rely on high-temperature and high-pressure conditions, have low product selectivity, and high energy consumption, which limits their large-scale application. In contrast, enzyme catalysis technology stands out with its high substrate specificity, room-temperature and atmospheric-pressure reaction conditions, and low energy input requirements, and is regarded as an important direction of green chemistry. For example, formate dehydrogenase (FDH) can accurately catalyze the reduction of CO2 to formate, while relying on coenzyme NADH to provide electrons. However, enzyme catalysis requires continuous regeneration of NADH to maintain the reaction cycle, which has given rise to the innovation of a photocatalysis-enzyme coupling system: by capturing solar energy and exciting electrons with a photocatalyst, directly reducing NADH, and then driving enzyme-catalyzed CO2 conversion, ultimately achieving the goal of "artificial photosynthesis".
[0003] In the selection of photocatalysts, graphitic carbon nitride (g-C3N4) has become an ideal candidate material due to its low cost, high chemical stability, non-toxicity, and excellent biocompatibility. Research shows that coupling g-C3N4 with formate dehydrogenase (FDH) can construct an efficient photoenzymatic coupling system to achieve the directional conversion of CO2 to formic acid. Although the g-C3N4-enzyme coupling system shows potential in the reduction of CO2 to formic acid, its practical application still faces multiple challenges, specifically: (1) Limited light absorption range. The bandgap of pristine g-C3N4 is about 2.7 eV, which can only absorb visible light with wavelengths less than 460 nm and cannot utilize the longer-wavelength visible light that accounts for a higher proportion in the solar spectrum; (2) High recombination rate of photo-generated carriers and low effective electron utilization rate; (3) Small specific surface area and insufficient active sites; (4) Insufficient catalytic stability. In a continuous light irradiation and oxidative environment, g-C3N4 is prone to surface photocorrosion. Therefore, the metal cation doping strategy is introduced. Metal cation doping can induce lattice distortion in g-C3N4, optimize the electron migration path, and promote the separation of photo-generated electron-hole pairs. However, the existing doping technologies still face key bottlenecks: poor doping uniformity. The traditional calcination method is prone to local aggregation of metal ions, forming inactive phases; insufficient structural stability. The doped ions may leach out due to lattice loosening or acidic environment during the reaction, resulting in performance degradation; low photo-enzyme synergistic efficiency. Although the light absorption is enhanced, the interfacial energy loss is still relatively high.
[0004] For this reason, the present invention proposes a cesium ion-doped carbon nitride catalyst and its preparation method and application. The cesium ion-doped carbon nitride catalyst prepared by the thermal polycondensation method has good utilization effect on visible light; cesium ion doping increases the specific surface area of carbon nitride, exposing more active sites; and this catalyst has good stability, and the surface functional groups can immobilize formate dehydrogenase, thus having better performance in the photoenzymatic coupling reduction of CO2 to formic acid. Summary of the Invention
[0005] In view of the problems existing in the prior art, the purpose of the present invention is to provide a cesium ion-doped carbon nitride catalyst and its preparation method and application, which have the characteristics of good catalytic effect, simple preparation method, wide raw material sources, and safety and environmental protection.
[0006] To achieve the above purpose, the technical solution of the present invention is as follows: A preparation method of a cesium ion-doped carbon nitride catalyst, comprising the following steps: 1) Grind melamine and cesium chloride in a mortar. After grinding, add deionized water and mix evenly for later use; 2) Transfer the uniformly mixed material in step 1) to a porcelain boat, cover it with a ceramic lid, place it in a tube furnace, and slowly heat it for calcination in an N2 atmosphere. After the calcination is completed, grind the obtained solid product into powder for later use; 3) Wash the powder obtained in step 2) multiple times with deionized water to wash away the residual water-soluble cesium chloride until the pH value of the mixed solution is 7-8, and then centrifuge the mixture to obtain a solid. 4) Add the solid obtained in step 3) to a beaker, add deionized water, perform ultrasonic treatment, and finally centrifuge. Dry and encapsulate the obtained solid, which is the cesium ion-doped carbon nitride catalyst to be prepared.
[0007] Further, in step 1), the mass ratio of melamine to cesium chloride and the volume ratio of deionized water are 1:0.1-3:0.5-3, preferably 1:2:1, where the mass unit is g and the volume unit is mL.
[0008] Further, in step 2), the calcination temperature is 400-800 °C, preferably 550 °C; the calcination time is 2-5 h, preferably 4 h.
[0009] Further, in step 4), the ultrasonic time is 0.5-4 h, preferably 2 h; the drying time is 6-24 h, preferably 12 h.
[0010] The present invention provides a cesium ion-doped carbon nitride catalyst prepared by the above method.
[0011] The present invention also provides an application of the cesium ion-doped carbon nitride catalyst in the photocatalytic enzyme-coupled reduction of CO2 to formic acid.
[0012] Further, it includes the following steps: First, add the cesium ion-doped carbon nitride catalyst and triethanolamine to the sodium phosphate buffer solution, perform ultrasonic dispersion treatment, and then add [Cp*Rh(bpy)H2O] 2+ , a mixed solution of oxidized nicotinamide adenine dinucleotide (NAD + ). Then transfer the mixed solution to a photocatalytic reaction kettle, stir under sealed conditions, and introduce CO2. Add formate dehydrogenase (FDH) before light irradiation, and react under the irradiation of a xenon lamp light source to carry out the photocatalytic enzyme-coupled production of formic acid reaction.
[0013] Further, the mass ratio of the cesium ion-doped carbon nitride catalyst to the volume of the sodium phosphate buffer solution is 0.5-2:1, preferably 1:1, where the mass unit is g and the volume unit is mL; the volume ratio of triethanolamine to the sodium phosphate buffer solution is 0.1-0.5:1, preferably 0.15:1.
[0014] Further, [Cp*Rh(bpy)H2O] 2+ and oxidized nicotinamide adenine dinucleotide (NAD +The molar ratio of () is 0.2:3; the flow rate of CO2 introduced is 1 - 30 mL / min, preferably 10 mL / min.
[0015] Furthermore, the culturing time of the formate dehydrogenase is 10 - 24 h, preferably 12 h; the wavelength of the xenon lamp is 300 - 800 nm, preferably in the visible light band with a wavelength of 420 - 800 nm.
[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) In the present invention, first, melamine and cesium chloride are ground in a mortar. After grinding, deionized water is added and mixed evenly for standby. The uniformly mixed material is transferred to a porcelain boat, covered with a ceramic lid, and placed in a tube furnace. It is slowly heated and calcined in an N2 atmosphere. After the calcination is completed, the obtained solid product is ground into powder for standby. The obtained powder is washed multiple times with ionized water to wash away the residual water-soluble cesium chloride until the pH value of the mixed solution is 7 - 8. Subsequently, the mixture is centrifuged to obtain a solid. The obtained solid is added to a beaker, deionized water is added, and ultrasonic treatment is carried out. Finally, it is centrifuged, and the obtained solid is dried and encapsulated, which is the cesium ion-doped carbon nitride catalyst to be prepared. The preparation of the cesium ion-doped carbon nitride catalyst has good utilization effect on the dominant visible light in the solar spectrum, and thus has good performance in photocatalytic enzyme-coupled reduction of CO2 to formic acid; 2) In the present invention, by doping different masses of cesium ions to modify the carbon nitride material, a large number of cyano and hydroxyl functional groups are induced to form on the surface of the carbonized carbon material by cesium ions, thereby regulating the intrinsic structure of the material; 3) The present invention has the characteristics of simple method, wide source of raw materials, the prepared catalyst does not contain precious metals, good catalytic effect, and safety and environmental protection. Description of the Drawings
[0017] Figure 1 SEM diagrams of the cesium ion-doped carbon nitride catalysts prepared in Examples 1 - 4 of the present invention; Figure 2 FT-IR diagrams of the cesium ion-doped carbon nitride catalysts prepared in Examples 1 - 4 of the present invention; Figure 3 Performance comparison diagrams of the photocatalytic enzyme-coupled reduction of CO2 to formic acid by the cesium ion-doped carbon nitride catalysts prepared in Examples 6 - 9 of the present invention; Figure 4 Performance comparison diagrams of the photocatalytic enzyme-coupled reduction of CO2 to formic acid under different reaction temperature conditions by the cesium ion-doped carbon nitride catalysts prepared in Examples 10 - 12 of the present invention. Detailed Embodiments
[0018] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to the described scope. Example 1
[0019] A preparation method of a cesium ion-doped carbon nitride catalyst includes the following steps: 1) Weigh 3 g of melamine and 6 g of cesium chloride, place them in a mortar and grind. After grinding, add 1 mL of deionized water, mix evenly and set aside; 2) Transfer the evenly mixed material in step 1) to a porcelain boat, cover it with a ceramic lid, put it into a tube furnace, and under a N2 atmosphere, heat it to 550 °C at a heating rate of 2.2 °C / h, and keep it at 550 °C for 4 h; after the roasting is completed, grind the obtained solid product into powder and set aside; 3) Wash the powder obtained in step 2) with ionized water multiple times to wash away the residual water-soluble cesium chloride until the pH value of the mixed solution is 7-8, and then centrifuge the mixture to obtain a solid; 4) Transfer the solid obtained in step 3) to a beaker, add 200 mL of deionized water and ultrasonically treat it for 2 h. After completion, centrifuge to obtain the precipitate, and finally place the solid precipitate in a 60 °C vacuum oven and dry it for 12 h. The final cesium ion-doped carbon nitride catalyst 1 is obtained. Example 2
[0020] A preparation method of a cesium ion-doped carbon nitride catalyst includes the following steps: 1) Weigh 3 g of melamine and 3 g of cesium chloride, place them in a mortar and grind. After grinding, add 1 mL of deionized water, mix evenly and set aside; 2) Transfer the evenly mixed material in step 1) to a porcelain boat, cover it with a ceramic lid, put it into a tube furnace, and under a N2 atmosphere, heat it to 550 °C at a heating rate of 2.2 °C / h, and keep it at 550 °C for 4 h; after the roasting is completed, grind the obtained solid product into powder and set aside; 3) Wash the powder obtained in step 2) with ionized water multiple times to wash away the residual water-soluble cesium chloride until the pH value of the mixed solution is 7-8, and then centrifuge the mixture to obtain a solid; 4) Transfer the solid obtained in step 3) to a beaker, add 200 mL of deionized water and ultrasonically treat it for 2 h. After completion, centrifuge to obtain the precipitate, and finally place the solid precipitate in a 60 °C vacuum oven and dry it for 12 h. The final cesium ion-doped carbon nitride catalyst 2 is obtained. Example 3
[0021] A preparation method of a cesium ion-doped carbon nitride catalyst includes the following steps: 1) Weigh 3 g of melamine and 9 g of cesium chloride, place them in a mortar and grind. After grinding, add 1 mL of deionized water, mix evenly and set aside. 2) Transfer the evenly mixed material in step 1) to a porcelain boat, cover it with a ceramic lid, put it into a tube furnace, and under a N2 atmosphere, heat it to 550 °C at a heating rate of 2.2 °C / h, and keep it at 550 °C for 4 h. After the calcination is completed, grind the obtained solid product into powder and set aside. 3) Wash the powder obtained in step 2) several times with ionized water to wash away the residual water-soluble cesium chloride until the pH value of the mixed solution is 7 - 8, and then centrifuge the mixture to obtain a solid. 4) Transfer the solid obtained in step 3) to a beaker, add 200 mL of deionized water and ultrasonically treat it for 2 h. After completion, centrifuge to obtain the precipitate, and finally place the solid precipitate in a 60 °C vacuum oven and dry it for 12 h. The final cesium ion-doped carbon nitride catalyst 3 is obtained. Example 4
[0022] A preparation method of a cesium ion-doped carbon nitride catalyst, comprising the following steps: 1) Weigh 3 g of melamine and 0 g of cesium chloride, place them in a mortar and grind. After grinding, add 1 mL of deionized water, mix evenly and set aside. 2) Transfer the evenly mixed material in step 1) to a porcelain boat, cover it with a ceramic lid, put it into a tube furnace, and under a N2 atmosphere, heat it to 550 °C at a heating rate of 2.2 °C / h, and keep it at 550 °C for 4 h. After the calcination is completed, grind the obtained solid product into powder and set aside. 3) Wash the powder obtained in step 2) several times with ionized water to wash away the residual water-soluble cesium chloride until the pH value of the mixed solution is 7 - 8, and then centrifuge the mixture to obtain a solid. 4) Transfer the solid obtained in step 3) to a beaker, add 200 mL of deionized water and ultrasonically treat it for 2 h. After completion, centrifuge to obtain the precipitate, and finally place the solid precipitate in a 60 °C vacuum oven and dry it for 12 h. The final cesium ion-doped carbon nitride catalyst 4 is obtained.
[0023] From Figure 1 the scanning electron microscope (SEM) images, it can be seen that the morphologies of cesium ion-doped carbon nitride catalysts 1 - cesium ion-doped carbon nitride catalysts 4 all present an irregular flaky structure, and with the increase of the cesium ion doping amount, the catalyst gradually changes from a regular flaky structure to an amorphous structure and agglomeration occurs.
[0024] Furthermore, from Figure 2It can be seen from the Fourier transform infrared (FT-IR) spectrogram that the doping of an appropriate amount of cesium ions is a key factor for the formation of a large number of cyano and hydroxyl functional groups in the carbon nitride catalyst. The cyano and hydroxyl functional groups can effectively improve the carrier separation ability of the catalyst, promote the separation of electron-hole pairs in the catalyst, and are more conducive to more photogenerated carriers participating in the catalytic reaction of photocatalytic enzyme-coupled reduction of CO2 to formic acid.
[0025] The carbon nitride catalyst 4 is pristine unmodified graphitic carbon nitride, without cyano peaks (2173 cm -1 ), and hydroxyl peaks (3200 cm -1 -3600 cm -1 , 1150 cm -1 , 1000 cm -1 ). There is a basic heptazine ring structure (1200 cm -1 -1800cm -1 ). With the increase in the amount of cesium ions, a large number of cyano groups (2173 cm -1 ) and hydroxyl peaks (3200 cm -1 -3600 cm -1 , 1150 cm -1 , 1000 cm -1 ) appear, indicating the introduction of a large number of these two types of functional group structures. The heptazine ring structure is consistent with the graphitic carbon nitride material. However, the excessive amount of cesium ions leads to the destruction of the overall carbon-nitrogen structure and the loss of good visible light response ability. Example 5
[0026] A method for photocatalytic enzyme-coupled reduction of CO2 to formic acid using a cesium ion-doped carbon nitride catalyst, wherein the cultivation, separation, and purification of formate dehydrogenase include the following steps: The recombinant Escherichia coli BL21(DE3) cells are pre-cultured in LB medium containing 100 mg / L kanamycin at 37 °C for 12 hours. Subsequently, after culturing at 37 °C and 200 rpm for 3 hours, 50 μL of IPTG (500 mM) is added, and the cells are further cultured at 24 °C and 200 rpm for 12 hours. Finally, the optical density (OD600) of each culture is measured with a spectrophotometer at a wavelength of 600 nm.
[0027] The harvested cells were resuspended in phosphate buffer (50 mM, pH = 7.4), disrupted using an ultrasonic crusher, and the supernatant was collected after centrifugation. The supernatant was added to a Ni-NTA agarose affinity column and washed with phosphate buffer (50 mM, pH = 7.4) containing 40 mM imidazole. The expressed target protein was eluted with phosphate buffer (50 mM, pH = 7.4) containing 300 mM imidazole. Subsequently, the eluate was dialyzed for desalting (14 kDa cut-off) using 5 mM phosphate buffer and concentrated using solid polyethylene glycol (PEG) 20000. The GDH protein was identified by 10% sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The protein concentration was determined using the Bradford method. Example 6
[0028] A method for the photocatalytic enzyme-coupled reduction of CO2 to formic acid using a cesium ion-doped carbon nitride catalyst, comprising the following steps: First, 30 mg of cesium ion-doped carbon nitride catalyst 1 and 4.5 mL of triethanolamine were added to 30 mL of sodium phosphate buffer, followed by ultrasonic dispersion treatment, and then 2.6 mg of [Cp*Rh(bpy)H2O] 2+ (0.2 mM), 60 mg of oxidized nicotinamide adenine dinucleotide (NAD + ) (3 mM) were added to obtain a mixed solution. Then, the mixed solution was transferred to a 500 mL photocatalytic reactor, stirred under sealed conditions, and CO2 was introduced at a rate of 10 mL / min. Formate dehydrogenase (FDH) was added before illumination, and the reaction was carried out under irradiation with a 300 W xenon light source. A visible light filter with a cut-off wavelength of 420 nm was taken, and the light wavelength output by the xenon light source was controlled to be visible light with a wavelength greater than 420 nm; the reaction of photocatalytic enzyme-coupled production of formic acid was carried out by heating in a 37 °C water bath. The formic acid yield was detected by high performance liquid chromatography (HPLC, Ultimate 3000). Example 7
[0029] A method for the photocatalytic enzyme-coupled reduction of CO2 to formic acid using a cesium ion-doped carbon nitride catalyst, comprising the following steps: First, 30 mg of cesium ion-doped carbon nitride catalyst 2 and 4.5 mL of triethanolamine were added to 30 mL of sodium phosphate buffer, followed by ultrasonic dispersion treatment, and then 2.6 mg of [Cp*Rh(bpy)H2O] 2+ (0.2 mM), 60 mg of oxidized nicotinamide adenine dinucleotide (NAD +)(3 mM) to obtain a mixed solution, then transfer the mixed solution to a 500 mL photocatalytic reactor, stir under sealed conditions, and introduce CO2 at a rate of 10 mL / min. Add formate dehydrogenase (FDH) before illumination, react under the irradiation of a 300 W xenon light source, select a visible light filter with a cut-off wavelength of 420 nm, and control the light wavelength output by the xenon light source to visible light with a wavelength greater than 420 nm; carry out the photoenzymatic coupling reaction to produce formic acid by heating in a 37 °C water bath. The formic acid yield is detected by high performance liquid chromatography (HPLC, Ultimate 3000). Example 8
[0030] A method for using a cesium ion-doped carbon nitride catalyst for photoenzymatic coupling reduction of CO2 to produce formic acid, comprising the following steps: First, add 30 mg of cesium ion-doped carbon nitride catalyst 3 and 4.5 mL of triethanolamine to 30 mL of sodium phosphate buffer solution, perform ultrasonic dispersion treatment, and then add 2.6 mg of [Cp*Rh(bpy)H2O] 2+ (0.2 mM), 60 mg of oxidized nicotinamide adenine dinucleotide (NAD + )(3 mM) to obtain a mixed solution, then transfer the mixed solution to a 500 mL photocatalytic reactor, stir under sealed conditions, and introduce CO2 at a rate of 10 mL / min. Add formate dehydrogenase (FDH) before illumination, react under the irradiation of a 300 W xenon light source, select a visible light filter with a cut-off wavelength of 420 nm, and control the light wavelength output by the xenon light source to visible light with a wavelength greater than 420 nm; carry out the photoenzymatic coupling reaction to produce formic acid by heating in a 37 °C water bath. The formic acid yield is detected by high performance liquid chromatography (HPLC, Ultimate 3000). Example 9
[0031] A method for using a cesium ion-doped carbon nitride catalyst for photoenzymatic coupling reduction of CO2 to produce formic acid, comprising the following steps: First, add 30 mg of cesium ion-doped carbon nitride catalyst 4 and 4.5 mL of triethanolamine to 30 mL of sodium phosphate buffer solution, perform ultrasonic dispersion treatment, and then add 2.6 mg of [Cp*Rh(bpy)H2O] 2+ (0.2 mM), 60 mg of oxidized nicotinamide adenine dinucleotide (NAD +)(3 mM) to obtain a mixed solution, and then transfer the mixed solution to a 500 mL photocatalytic reactor, stir under sealed conditions, and introduce CO2 at a rate of 10 mL / min. Add formate dehydrogenase (FDH) before illumination, and react under the irradiation of a 300 W xenon light source. Select a visible light filter with a cut-off wavelength of 420 nm to control the light wavelength output by the xenon light source to visible light with a wavelength greater than 420 nm; carry out the photoenzymatic coupling reaction to produce formic acid by heating in a 37 °C water bath. The formic acid yield was detected by high performance liquid chromatography (HPLC, Ultimate 3000).
[0032] The experimental performance of the cesium ion-doped carbon nitride catalyst for photoenzymatic coupling reduction of CO2 to produce formic acid ( Figure 3 ) shows that as the amount of cesium ion doping increases, the concentration of formic acid produced by reducing CO2 shows the characteristics of a volcano-shaped curve. When the amount of cesium ion doping increases from 0 g to 6 g, the formic acid concentration increases from 0.01 mmol L -1 to 2.75 mmol L -1 ; when the amount of cesium ion doping further increases to 9 g, the formic acid concentration drops to 1.1 mmol L -1 . Carbon nitride catalyst 1 has the highest formic acid yield. However, for the cesium ion-doped carbon nitride catalyst 3, due to the modification of excessive cesium ions that destroys the carbon nitride structure, resulting in a decrease in the ability to produce formic acid, an appropriate amount of cesium ion doping (6 g) exhibits the best performance for reducing CO2 to produce formic acid. Example 10
[0033] A method for using a cesium ion-doped carbon nitride catalyst for photoenzymatic coupling reduction of CO2 to produce formic acid, comprising the following steps: First, add 30 mg of cesium ion-doped carbon nitride catalyst 1 and 4.5 mL of triethanolamine to 30 mL of sodium phosphate buffer solution, perform ultrasonic dispersion treatment, and then add 2.6 mg of [Cp*Rh(bpy)H2O] 2+ (0.2 mM), 60 mg of oxidized nicotinamide adenine dinucleotide (NAD + ) (3 mM) to obtain a mixed solution, and then transfer the mixed solution to a 500 mL photocatalytic reactor, stir under sealed conditions, and introduce CO2 at a rate of 10 mL / min. Add formate dehydrogenase (FDH) before illumination, and react under the irradiation of a 300 W xenon light source. Select a visible light filter with a cut-off wavelength of 420 nm to control the light wavelength output by the xenon light source to visible light with a wavelength greater than 420 nm; carry out the photoenzymatic coupling reaction to produce formic acid by heating in a 25 °C water bath. The formic acid yield was detected by high performance liquid chromatography (HPLC, Ultimate 3000). Example 11
[0034] A method for photocatalytic enzyme-coupled reduction of CO2 to formic acid using a cesium ion-doped carbon nitride catalyst, comprising the following steps: First, 30 mg of cesium ion-doped carbon nitride catalyst 1 and 4.5 mL of triethanolamine are added to 30 mL of sodium phosphate buffer solution, and ultrasonic dispersion treatment is carried out. Then, 2.6 mg of [Cp*Rh(bpy)H2O] 2+ (0.2 mM), 60 mg of oxidized nicotinamide adenine dinucleotide (NAD + ) (3 mM) are added to obtain a mixed solution. Then, the mixed solution is transferred to a 500 mL photocatalytic reactor, stirred under sealed conditions, and CO2 is introduced at a rate of 10 mL / min. Formate dehydrogenase (FDH) is added before illumination, and the reaction is carried out under irradiation with a 300 W xenon light source. A visible light filter with a cut-off wavelength of 420 nm is taken, and the light wavelength output by the xenon light source is controlled to be visible light with a wavelength greater than 420 nm; the reaction of photocatalytic enzyme-coupled production of formic acid is carried out by heating in a 15 °C water bath. The formic acid yield is detected by high performance liquid chromatography (HPLC, Ultimate 3000). Example 12
[0035] A method for photocatalytic enzyme-coupled reduction of CO2 to formic acid using a cesium ion-doped carbon nitride catalyst, comprising the following steps: First, 30 mg of cesium ion-doped carbon nitride catalyst 1 and 4.5 mL of triethanolamine are added to 30 mL of sodium phosphate buffer solution, and ultrasonic dispersion treatment is carried out. Then, 2.6 mg of [Cp*Rh(bpy)H2O] 2+ (0.2 mM), 60 mg of oxidized nicotinamide adenine dinucleotide (NAD + ) (3 mM) are added to obtain a mixed solution. Then, the mixed solution is transferred to a 500 mL photocatalytic reactor, stirred under sealed conditions, and CO2 is introduced at a rate of 10 mL / min. Formate dehydrogenase (FDH) is added before illumination, and the reaction is carried out under irradiation with a 300 W xenon light source. A visible light filter with a cut-off wavelength of 420 nm is taken, and the light wavelength output by the xenon light source is controlled to be visible light with a wavelength greater than 420 nm; the reaction of photocatalytic enzyme-coupled production of formic acid is carried out by heating in a 45 °C water bath. The formic acid yield is detected by high performance liquid chromatography (HPLC, Ultimate 3000).
[0036] From Figure 4 It can be seen from Examples 9-12 that as the reaction temperature increases, the performance of photocatalytic enzyme-coupled reduction of CO2 to formic acid also shows the characteristics of a volcano-shaped curve. When the reaction temperature rises from 15 °C to 37 °C, the formic acid concentration increases from 0.89 mmol L -1 to 2.75 mmol L -1However, when the temperature rises to 45 °C, the concentration of formic acid produced decreases rapidly. This is because formate dehydrogenase is sensitive to temperature. When the temperature is low, formate dehydrogenase cannot exhibit full activity, resulting in a low formic acid yield. When the temperature is too high, formate dehydrogenase will be partially inactivated, reducing the formic acid yield. Therefore, 37 °C was chosen as the reaction temperature.
Claims
1. A preparation method of a cesium ion-doped carbon nitride catalyst, characterized in that It includes the following steps: 1) Grind melamine and cesium chloride in a mortar. After grinding, add deionized water and mix evenly for standby; 2) Transfer the evenly mixed material in step 1) to a porcelain boat, cover it with a ceramic lid, place it in a tube furnace, and slowly heat it for roasting in an N2 atmosphere. After the roasting is completed, grind the obtained solid product into powder for standby; 3) Wash the powder obtained in step 2) with ionized water multiple times to wash away the residual water-soluble cesium chloride until the pH value of the mixed solution is 7-8. Then centrifuge the mixture to obtain a solid; 4) Add the solid obtained in step 3) to a beaker, add deionized water, perform ultrasonic treatment, and finally centrifuge. Dry and encapsulate the obtained solid, which is the cesium ion-doped carbon nitride catalyst to be prepared.
2. The preparation method of a cesium ion-doped carbon nitride catalyst according to claim 1, characterized in that In step 1), the mass ratio of melamine to cesium chloride and the volume ratio of deionized water are 1:0.1-3:0.5-3, preferably 1:2:
1. The mass unit is g and the volume unit is mL.
3. The preparation method of a cesium ion-doped carbon nitride catalyst according to claim 1, wherein In step 2), the roasting temperature is 400-800 °C, preferably 550 °C; the roasting time is 2-5 h, preferably 4 h.
4. The preparation method of a cesium ion-doped carbon nitride catalyst according to claim 1, characterized in that In step 4), the ultrasonic time is 0.5-4 h, preferably 2 h; the drying time is 6-24 h, preferably 12 h.
5. A cesium ion-doped carbon nitride catalyst prepared by the method according to any one of claims 1-4.
6. An application of the cesium ion-doped carbon nitride catalyst according to claim 5 in the photoenzymatic coupling reduction of CO2 to formic acid.
7. The application according to claim 6, characterized in that It includes the following steps: First, add cesium ion-doped carbon nitride catalyst and triethanolamine to sodium phosphate buffer solution, perform ultrasonic dispersion treatment, and then add [Cp*Rh(bpy)H2O] 2+ , a mixed solution of oxidized nicotinamide adenine dinucleotide (NAD + ). Then transfer the mixed solution to a photocatalytic reactor, stir under sealed conditions, and introduce CO2. Add formate dehydrogenase (FDH) before illumination, and react under the irradiation of a xenon lamp light source to carry out the reaction of photoenzymatic coupling to produce formic acid.
8. The application according to claim 7, characterized in that The mass ratio of the cesium ion-doped carbon nitride catalyst to the volume of sodium phosphate buffer is 0.5-2:1, preferably 1:
1. The mass unit is g and the volume unit is mL; the volume ratio of triethanolamine to sodium phosphate buffer is 0.1-0.5:1, preferably 0.15:
1.
9. The application according to claim 7, wherein [Cp*Rh(bpy)H2O] 2+ The molar ratio with oxidized nicotinamide adenine dinucleotide (NAD + ) is 0.2:3; the flow rate of CO2 introduced is 1 - 30 mL / min, preferably 10 mL / min.
10. The application according to claim 7, wherein The cultivation time of the formate dehydrogenase is 10-24 h, preferably 12 h. The wavelength of the xenon lamp is 300-800 nm, preferably in the visible light band with a wavelength of 420-800 nm.