Integrated catalyst for coenzyme regeneration and preparation method thereof

Abstract

The invention discloses an integrated catalyst for photocatalytic coenzyme regeneration, which is characterized in that a silicon dioxide template and a precursor for preparing bulk-phase carbon nitride are mutually mixed, bulk-phase carbon nitride is formed under the support of the template, and porous carbon nitride is formed by removing the template; assembling a poly (allylamine hydrochloride) / 2, 2 '-bipyridine-5, 5'-dicarboxylic acid solution coating on the surface of the porous carbon nitride by utilizing electrostatic interaction of amino in a poly (allylamine hydrochloride) solution and carboxyl in a 2, 2 '-bipyridine-5, 5'-dicarboxylic acid solution; 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride is used for activating carboxyl, so that covalent bonds are formed between amino and carboxyl, and the coating is stabilized; and (Cp * RhCl2) 2 and a bipyridine structure in the coating form coordination through long-time soaking and contact, so that immobilization of a cocatalyst [Cp * Rh (bpy-COOH) H2O] < 2 + > is realized. By regulating and controlling the immobilization amount of [Cp * Rh (bpy-COOH) H2O] < 2 + > on the surface of the photocatalyst, electron transfer and utilization are coordinated and optimized, and efficient regeneration of NADH is achieved.

Description

Technical Field

[0001] The present invention relates to the preparation of photocatalysts, and particularly to an integrated catalyst for photocatalytic coenzyme regeneration and a preparation method thereof. Background Art

[0002] The enzyme-light (light-enzyme) coupled artificial photosynthetic system mimics natural photosynthesis, uses semiconductors and enzymes as catalysts, triethanolamine and the like as electron donors, coenzymes such as coenzyme (NADH) as energy carriers, and uses photocatalysis to regenerate coenzymes and drive the enzyme-catalyzed material transformation process. Compared with the light-chemical coupling system and the light-microbial coupling system, the enzyme-light coupling system has the advantages of mild reaction conditions, path designability, easy mechanism analysis, etc., and is one of the important ways to solve problems such as energy shortage and environmental crisis. In the enzyme-light coupled artificial photosynthesis process, coenzyme molecules such as NADH act as energy currencies responsible for energy transfer and material transformation. Therefore, designing an integrated catalyst for coenzyme regeneration to construct an efficient photocatalytic NADH regeneration system is the key to improving the overall light-chemical conversion efficiency of the system. Summary of the Invention

[0003] The purpose of the present invention is to provide an integrated catalyst for photocatalytic coenzyme regeneration and a preparation method thereof. The present invention uses a simple and controllable hard template method to prepare a photocatalyst, and immobilizes [Cp*Rh(bpy-COOH)H 2 O] 2+ (denoted as Rh) on the surface of the catalyst, realizing efficient photocatalytic regeneration of NADH.

[0004] To achieve the above purpose, the present invention proposes an integrated catalyst for photocatalytic coenzyme regeneration, which mixes a silica template with a precursor for preparing bulk graphitic carbon nitride (GCN), forms bulk GCN supported by the template, and finally removes the template to form porous carbon nitride (PCN); uses the electrostatic interaction between the amino group in the polyallylamine hydrochloride solution (PAH) and the carboxyl group in the 2,2'-bipyridine-5,5'-dicarboxylic acid solution (bpy-COOH) to assemble a polyallylamine hydrochloride / 2,2'-bipyridine-5,5'-dicarboxylic acid solution (PAH / bpy-OOH) coating on the surface of the porous carbon nitride (PCN); uses 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride to activate the carboxyl group to form a covalent bond between the amino group and the carboxyl group to stabilize the coating; through long-term immersion contact with (Cp*RhCl 2 ) 2 so that (Cp*RhCl 2 ) 2 coordinates with the bipyridine structure in the coating to realize the cocatalyst [Cp*Rh(bpy-COOH)H 2 O] 2+The immobilization forms the porous carbon nitride with the surface-immobilized cocatalyst, which is the integrated catalyst described above.

[0005] Meanwhile, the present invention also provides a preparation method of the above integrated catalyst, including the following steps:

[0006] Step 1: Preparation of the silica template, including: preparing solution phase A: adding ammonia water with a mass concentration of 28%, absolute ethanol, and deionized water into a container according to a volume ratio of 9:16.25:24.75, and stirring at 900 r / min for 10 min to obtain solution phase A; preparing solution phase B: adding tetraethyl orthosilicate and absolute ethanol into a container according to a volume ratio of 1:10.11, and stirring at 900 r / min for 10 min to obtain solution phase B; quickly adding the solution phase B to the solution phase A according to a volume ratio of 1:1, first stirring quickly, and then reducing the rotation speed to continue stirring to obtain a white suspension. After centrifuging the white suspension, washing it three times with ethanol, and drying it at 60 °C for 24 h, a white blocky solid is obtained. After grinding, silica microspheres with an average diameter of 360 nm ± 20 nm are obtained, which are the silica template.

[0007] Step 2: Preparation of porous carbon nitride filled with silica microspheres, including: mixing the silica microspheres obtained in Step 1 and melamine according to a mass ratio of 1:1 and placing them in a container, adding an appropriate amount of deionized water, wherein the mass-volume ratio of the mixture to deionized water is 300 mg / mL. After ultrasonic dispersion, stirring at 1200 r / min at a constant temperature of 60 °C until the water is completely evaporated to obtain a white powder; transferring all the white powder to a crucible, wrapping it with two layers of tin foil paper, putting it into a muffle furnace for calcination, taking it out after cooling to room temperature, obtaining a dark yellow blocky solid, and the product obtained after grinding is porous carbon nitride filled with silica microspheres (SiO 2 @PCN);

[0008] Step 3: Removal of the silica template to form porous carbon nitride, including: adding the SiO 2 @PCN obtained in Step 2 to an ammonium bifluoride (NH -1 HF 4 ) solution with a concentration of 4 mol / L according to a mass-volume ratio of 20 mg / mL, placing it in a shaker for etching for 24 h, centrifuging and washing it three times with water; drying it at 60 °C for 24 h to obtain porous carbon nitride powder, denoted as PCN; 2 ) solution with a concentration of 4 mol / L according to a mass-volume ratio of 20 mg / mL, placing it in a shaker for etching for 24 h, centrifuging and washing it three times with water; drying it at 60 °C for 24 h to obtain porous carbon nitride powder, denoted as PCN;

[0009] Step 4: Assembling a coating on the surface of the porous carbon nitride, including: dispersing the PCN obtained in Step 3 in a solution with a concentration of 1 mg / mL according to a mass-volume ratio of 12.5 mg / mL by ultrasonic -1, In a PAH solution with a pH of 7.0, shake for 10 min to obtain a dispersion; add a bpy-COOH solution with a concentration of 20 mM and a pH of 6.0 to the above dispersion according to a volume ratio of 8:7, and shake for 10 min; after centrifugation, directly place it in a vacuum drying oven for drying without washing with water. The obtained product is PCN with PAH and bpy-COOH coatings assembled on the surface (PCN / PAH-bpy);

[0010] Step Five, stabilizing the coating, including: preparing a 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride / morpholineethanesulfonic acid monohydrate (EDC / MES) solution with a concentration of 300 / 100 mg mL -1 and a pH of 5.0; ultrasonically disperse the product PCN / PAH-bpy obtained in Step Four in the EDC / MES solution according to a mass-volume ratio of 5 mg / mL, shake at room temperature for 2 h, centrifuge and wash once with water;

[0011] Step Six, immobilizing the cocatalyst [Cp*Rh(bpy-COOH)H 2 O] 2+ , including: adding a (Cp*RhCl -1 ) with a concentration of 0.5 - 2.0 mg mL 2 to the solution obtained in Step Five according to a volume ratio of 1:10, shake at room temperature for 12 h, centrifuge and wash 3 times with water, then treat with liquid nitrogen and freeze-dry to obtain a PCN integrated catalyst (PCN / Rh 2 ) with the cocatalyst [Cp*Rh(bpy-COOH)H 2 O] 2+ immobilized on the surface. x )

[0012] Furthermore, in the preparation method of the present invention, where:

[0013] In Step One, the rotation speed of the rapid stirring is 900 r / min, and the stirring time is 1 min; the rotation speed of the continued stirring at a reduced speed is 400 r / min, and the stirring time is 12 h.

[0014] In Step Two, the process of ultrasonic dispersion is to place the suspension in an ultrasonic cleaner with an ultrasonic frequency of 30 - 50 kHz for ultrasonic treatment for 20 - 30 min. The process conditions of the calcination are: firing at 500 °C for 4 h, and the heating rate from room temperature to 500 °C is 5 °C / min.

[0015] In Step Four, the process conditions of the drying are: the drying temperature of the vacuum drying oven is 40 °C, and the drying time is 12 h.

[0016] In Step 6, the freeze-drying process is as follows: place it in a freeze-dryer at a temperature of -40°C for 10 - 12 hours.

[0017] The preparation conditions of the present invention are mild and the process is simple. Compared with the existing GCN photocatalytic coenzyme regeneration technology, the photocatalyst PCN / Rh prepared in the present invention x has a significant improvement in the performance of coenzyme regeneration. The preparation method of the present invention uses the hard template method to prepare PCN, and then successfully immobilizes different concentrations of the cocatalyst Rh on the surface of PCN by the surface coating method to prepare the supported catalyst (PCN / Rh x ). The hard template method in the present invention utilizes the advantage that the connected porous structure is beneficial to the generation and transfer of electrons, promotes the electron transfer process of PCN, and strengthens the photocatalytic NADH performance of PCN. In the photocatalytic NADH regeneration reaction, the effective product is enzymatically active 1,4-NADH. Through the proton-coupled electron transfer method, the cocatalyst Rh can directly reduce NAD + to 1,4-NADH. The immobilization of Rh is beneficial to the rapid transfer of electrons from the catalyst surface to the cocatalyst Rh, reduces the electron-hole recombination rate, and improves the electron transfer and utilization ability of PCN / Rh. This method can regulate the surface Rh immobilization amount of PCN / Rh by controlling the concentration of the solution (Cp*RhCl 2 ) during the Rh immobilization process, which significantly improves the efficiency of photocatalytic coenzyme regeneration. 2 x BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 SEM photograph of PCN obtained during the preparation process of the invention;

[0019] Figure 2 TEM photograph of PCN / Rh prepared in Example 1 of the present invention; 1

[0020] Figure 3 Photocatalytic NADH regeneration performance graph of GCN prepared in Comparative Example 1 and PCN prepared in Comparative Example 2;

[0021] Figure 4 Photocatalytic NADH regeneration performance graph of PCN, PCN plus free Rh, and PCN immobilized with Rh;

[0022] Figure 5 Photocatalytic NADH regeneration performance graph of PCN / Rh prepared in Example 1, Comparative Examples 3 - 4, Examples 2 - 3, and Comparative Example 5; x DETAILED DESCRIPTION OF THE INVENTION ​​​​

[0023] The design concept of the present invention is as follows: taking the "carrier generation, transfer and utilization" in the photocatalytic NADH regeneration reaction as the research object, using the strategy of constructing a photocatalytic NADH regeneration system based on porous carbon nitride to strengthen the processes of carrier generation, transfer and utilization, and improving the photo-chemical conversion efficiency. Taking advantage of the fact that the connected porous structure is beneficial to electron generation and transfer, PCN is prepared by the hard template method, and the immobilization of Rh is beneficial to the rapid transfer of electrons from the catalyst surface to the cocatalyst Rh, reducing the electron-hole recombination rate. Therefore, different concentrations of the cocatalyst Rh are immobilized on the surface of PCN by the surface coating method, which significantly improves the efficiency of photocatalytic coenzyme regeneration. Its basic technical solution is: mixing the silica template with the precursor for preparing GCN, forming GCN under the support of the template, and finally using NH 4 HF 2 for etching to remove the template to form PCN; then using the electrostatic interaction between the amino group in PAH and the carboxyl group in bpy-COOH to assemble a PAH / bpy-OOH coating on the surface of porous carbon nitride; then activating the carboxyl group with EDC to form a covalent bond between the amino group and the carboxyl group to stabilize the coating; finally, through long-term immersion contact, (Cp*RhCl 2 ) 2 forms a coordination with the bipyridine structure in the coating to achieve the immobilization of the cocatalyst Rh, forming a PCN / Rh x catalyst. Porous carbon nitride is prepared by the hard template method, and different concentrations of [Cp*Rh(bpy-COOH)H 2 O] 2+ are immobilized on the surface of porous carbon nitride by the surface coating method to prepare the photocatalyst PCN / Rh x . Through the way of proton-coupled electron transfer, the cocatalyst [Cp*Rh(bpy-COOH)H 2 O] 2+ can directly reduce NAD + to 1,4-NADH, avoiding the generation of NAD·. Immobilizing [Cp*Rh(bpy-COOH)H 2 O] 2+ on the surface of the photocatalyst can effectively relieve the diffusion limitation and shorten the transfer distance of electrons to [Cp*Rh(bpy-COOH)H 2 O] 2+ , improving the performance of the photocatalytic NADH regeneration reaction.

[0024] The following further describes the technical solution of the present invention in detail with reference to the drawings and specific embodiments. The specific embodiments described are only for explaining the present invention and are not intended to limit the present invention.

[0025] Comparative Example 1: Preparation of the photocatalyst GCN, the steps are as follows:

[0026] Step 1: Weigh 1 g of melamine powder and place it in a crucible, wrap it with two layers of tin foil, and calcine it using the following calcination procedure: calcine at 500° C. for 4 hours, and the heating rate of the above heating process is 5° C. / min.

[0027] Step 2: Cool the powder in step 1 to room temperature and take it out to obtain a yellow block solid. After grinding, the final product is the photocatalyst GCN.

[0028] Figure 3 The photocatalytic NADH regeneration performance of the photocatalyst GCN is shown in FIG.

[0029] The test method used in the present invention is as follows: the reaction container is a 10×10×30 mm 3 The reaction solution mainly includes hydrogen bonded organic framework microcapsule membrane photocatalyst (1.0 mg mL -1 ), NAD + Solution (1mmol L -1 ), TEOA solution (400 mmol L -1 ) and PBS solution (100 mmol L -1 ), the pH of the reaction solution was 7.4. Before the test, the reactor containing the reaction solution was placed in the dark for 10 min, and then an LED light with a wavelength of 420 nm (100 mW cm -2 ) for illumination, and samples were taken at different time points after illumination. After filtration, the absorbance of the reaction solution at 340 nm was detected by a UV-visible spectrophotometer, and the concentration of photocatalytic NADH regeneration at this time was calculated using formula (1).

[0030]

[0031] Where c is the concentration of NADH regenerated by photocatalysis (mol L -1 ), A is the absorbance of the reaction solution at 340 nm, K is the absorption coefficient 6220 mol L -1 cm -1 , b is the optical path length (1 cm in this test).

[0032] Comparative Example 2: Preparation of photocatalyst PCN, the steps are as follows:

[0033] Step 1: Preparation of silica template, including: preparing solution phase A: adding 9 mL of ammonia water (mass concentration 28%) into a beaker, 16.25 mL of absolute ethanol and 24.75 mL of deionized water, and rapidly stirring at 900 r / min for 10 min. Preparing solution phase B: adding 4.5 mL of tetraethyl orthosilicate and 45.5 mL of absolute ethanol into a beaker, and rapidly stirring at 900 r / min for 10 min. Rapidly adding solution phase B into solution phase A, first stirring at 900 r / min for 1 min and then reducing the speed to 400 r / min and stirring for 12 h. At this time, a white suspension can be obtained. Centrifuging the white suspension at 8000 r / min for 3 min, washing with ethanol three times, and drying at 60 °C for 24 h to obtain a white block solid. After grinding, white silica microsphere powder with an average diameter of about 360 nm, namely silica template, can be obtained.

[0034] Step 2: Mix the white silica microsphere powder obtained in Step 1 with melamine in a mass ratio of 1:1 to obtain a mixture with a total mass of 1500 mg, and place it in a beaker. Add 5 mL of deionized water, and place it in an ultrasonic cleaner with an ultrasonic frequency of 50 kHz for ultrasonic dispersion treatment for 20 min. Place the beaker on a 60 °C constant temperature heating plate and rapidly stir at a speed of 1200 r / min until the water is completely evaporated to obtain a uniformly mixed white powder. Transfer all the obtained white powder to a crucible, wrap it with two layers of tin foil paper, put it into a muffle furnace for calcination, and carry out calcination under the same calcination process conditions as in Comparative Example 1. After cooling to room temperature, take it out to obtain a dark yellow block solid. The product obtained after grinding is porous carbon nitride filled with silica microspheres (SiO 2 @PCN).

[0035] Step 3: Weigh 500 mg of SiO 2 @PCN and add it to 25 mL of a 4 mol / L -1 NH 4 HF 2 solution, place it on a shaker for etching for 24 h, centrifuge and wash with water three times (10000 r / min, 5 min), and dry at 60 °C for 24 h to obtain porous carbon nitride powder, namely photocatalyst PCN.

[0036] Figure 1 is the SEM image of the photocatalyst PCN, Figure 3 showing the NADH regeneration performance of the photocatalyst PCN shown in it.

[0037] Example 1: Preparation of photocatalyst PCN / Rh 1 is as follows:

[0038] Step 1: Ultrasonically disperse 20 mg of the PCN finally obtained in Comparative Example 2 in 1.6 mL of PAH with a concentration of 1 mg / mL -1 and a pH of 7.0, and shake for 10 min; directly add 1.4 mL of a bpy-COOH solution with a concentration of 20 mM and a pH of 7.0 to the above dispersion, and shake for 10 min; after centrifugation, place it directly in a vacuum drying oven at 40 °C for drying for 12 h to obtain a PCN sample with PAH and bpy-COOH coatings assembled on the surface, denoted as PCN / PAH-bpy.

[0039] Step 2: Ultrasonically disperse the above PCN sample PCN / PAH-bpy in 4 mL of an EDC / MES solution with a concentration of 300 / 100 mM and a pH of 5.0, shake at room temperature for 2 h, and centrifuge and wash once with water;

[0040] Step 3: Add 400 μL of a solution with a concentration of 1.0 mg / mL -1 of (Cp*RhCl 2 ) 2 , shake at room temperature for 12 h, centrifuge and wash 3 times with water, and then place it in a freeze dryer for freeze drying at a temperature of -40 °C for 10 - 12 h; obtain a PCN sample with a co-catalyst Cp*Rh(bpy-COOH)H 2 O] 2+ solidly supported on the surface. Since the concentration of (Cp*RhCl 2 ) 2 added during the preparation process is 1.0 mg / mL -1 , denote the PCN sample with the co-catalyst Cp*Rh(bpy-COOH)H 2 O] 2+ solidly supported on the surface as PCN / Rh 1.0 .

[0041] Figure 1 Figure 34 is the SEM image of Comparative Example 2 required in the preparation process of this Example 1, Figure 2 Figure 36 is the EM image of PCN / Rh 1.0 obtained in this Example 1. It can be seen from the figure that PCN / Rh 1.0 was successfully prepared, and the Rh element is distributed at the edge of the ring.

[0042] Figure 5 Figure 44 shows that the photocatalytic coenzyme regeneration performance of the photocatalyst PCN / Rh 1.0 obtained in this Example 1 is 74.3%.

[0043] Comparative Example 3: Photocatalyst PCN / Rh 0.1Preparation. The procedure of Comparative Example 3 was basically the same as that of Example 1, except that: in step three of Example 1, the concentration of (Cp*RhCl 2 ) 2 was changed from 1.0 mg mL -1 to 0.1 mg mL -1 . The finally prepared product was photocatalyst PCN / Rh 0.1 .

[0044] Figure 5 It can be seen from 0.1 that the photocatalytic coenzyme regeneration performance of the photocatalyst PCN / Rh

[0045] prepared in Comparative Example 3 was about 24.4%.

[0045] Comparative Example 4: Preparation of photocatalyst PCN / Rh 0.2 . The procedure of Comparative Example 4 was basically the same as that of Example 1, except that: in step three of Example 1, the concentration of (Cp*RhCl 2 ) 2 was changed from 1.0 mg mL -1 to 0.2 mg mL -1 . The finally prepared product was photocatalyst PCN / Rh 0.2 .

[0046] Figure 5 It can be seen from 0.2 that the photocatalytic coenzyme regeneration performance of the photocatalyst PCN / Rh

[0047] prepared in Comparative Example 4 was about 43.8%.

[0047] Example 2: Preparation of photocatalyst PCN / Rh 0.5 . The procedure of Example 2 was basically the same as that of Example 1, except that: in step three of Example 1, the concentration of (Cp*RhCl 2 ) 2 was changed from 1.0 mg mL -1 to 0.5 mg mL -1 . The finally prepared product was photocatalyst PCN / Rh 0.5 .

[0048] Figure 5 It can be seen from 0.5 that the photocatalytic coenzyme regeneration performance of the photocatalyst PCN / Rh

[0049] prepared in Example 2 was about 64.9%.

[0049] Example 3: Preparation of photocatalyst PCN / Rh 2 . The procedure of Example 3 was basically the same as that of Example 1, except that: in step three of Example 1, the concentration of (Cp*RhCl 2 ) 2 was changed from 1.0 mg mL-1 Changed to 2.0 mg / mL -1 , and the finally prepared product is photocatalyst PCN / Rh 2.0 .

[0050] Figure 5 It can be seen from [reference] that the photocatalytic coenzyme regeneration performance of the photocatalyst PCN / Rh prepared in Example 2 2.0 is about 79.0%.

[0051] Comparative Example 5: Preparation of photocatalyst PCN / Rh 4 , the steps of Comparative Example 5 are basically the same as those of Example 1, and the difference is only that: in Step 3 of Example 1, the concentration of (Cp*RhCl 2 ) 2 was changed from 1.0 mg / mL -1 to 4.0 mg / mL -1 , and the finally prepared product is photocatalyst PCN / Rh 4.0 .

[0052] Figure 5 It can be seen from [reference] that the photocatalytic coenzyme regeneration performance of the photocatalyst PCN / Rh prepared in Comparative Example 5 4.0 is about 81.5%.

[0053] From Figure 3 the NADH regeneration performance graph shown, it can be seen that the NADH regeneration efficiencies of photocatalysts GCN and PCN are 38.4% and 42.1% respectively. Compared with GCN, the NADH regeneration efficiency of PCN has increased.

[0054] From Figure 5 the photocatalytic NADH regeneration performance graph shown, it can be seen that in the present invention, by regulating the concentration of (Cp*RhCl 2 ) 2 for catalyst design, the concentrations of (Cp*RhCl 2 ) 2 in Example 1, Comparative Examples 3-4, Examples 2-3, and Comparative Example 5 are 1.0, 0.1, 0.2, 0.5, 2.0, and 4.0 mg / mL -1 in turn, and moreover, the regeneration efficiency of NADH is positively correlated with the immobilization amount of Rh, see Table 1. Among them, the NADH regeneration performance of PCN / Rh 4 is the highest, and the NADH regeneration efficiency is 81.46%.

[0055] Table 1

[0056]

[0057] It can be seen from Table 1 that when (Cp*RhCl2 ) 2 When the solution concentration reaches 1.0 mg / mL -1 and then its concentration is further increased, the NADH regeneration performance of PCN / Rh x increases less. Considering the economic cost of Rh ($3904.69 per gram) and the photocatalytic NADH regeneration performance comprehensively, PCN / Rh 1 can be selected for other related research.

[0058] From the TEM image corresponding to Example 1 and the coenzyme regeneration performance diagrams corresponding to Examples 1-6 and Comparative Examples 1-2 above, it is found that first, PCN was prepared by the hard template method, and then the cocatalyst Rh was successfully immobilized on the surface of PCN by the surface coating method to prepare a supported catalyst (PCN / Rh x ). By regulating the concentration of the immobilized cocatalyst Rh, the catalyst was designed, and its NADH regeneration performance was tested. Figure 3 It can be seen that the performance of porous carbon nitride is superior to that of bulk carbon nitride; Figure 4 as can be seen from , the performance of immobilizing Rh on porous carbon nitride is superior to adding free Rh to the reaction solution of porous carbon nitride; Figure 5 as can be seen from , the regeneration efficiency of NADH is positively correlated with the loading amount of Rh. Among them, the NADH regeneration performance of PCN / Rh 4 is the highest, and the regeneration efficiency of NADH is 81.5%. The immobilization of Rh is beneficial to the rapid transfer of electrons from the catalyst surface to the cocatalyst Rh, reducing the electron-hole recombination rate and enhancing the electron transfer and utilization ability of PCN / Rh. By regulating the Rh loading amount on the photocatalyst surface and coordinating and optimizing electron transfer and utilization, the efficient regeneration of NADH was achieved. Therefore, the present invention uses the hard template method and the surface coating method for the design of an integrated catalyst. The preparation process is simple. By changing the amount of the immobilized cocatalyst Rh, the catalyst structure is regulated. Finally, the successful preparation of the catalyst is proved by the TEM image, and the NADH regeneration efficiency of 81.5% is obtained through the performance diagram.

[0059] Although the present invention has been described above in conjunction with the accompanying drawings, the present invention is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can also make many improvements and changes without departing from the spirit of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. An integrated catalyst for photocatalytic coenzyme regeneration, characterized in that: The silicon dioxide template and the precursor for preparing bulk carbon nitride are mixed with each other to form bulk carbon nitride under the support of the template, and finally the template is removed to form porous carbon nitride; the electrostatic interaction between the amino group in the polyallylamine hydrochloride solution and the carboxyl group in the 2,2'-bipyridine-5,5'-dicarboxylic acid solution is used to assemble the polyallylamine hydrochloride / 2,2'-bipyridine-5,5'-dicarboxylic acid solution coating on the surface of the porous carbon nitride; the carboxyl group is activated by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride to form a covalent bond between the amino group and the carboxyl group to stabilize the coating; by soaking in (Cp*RhCl2)2 for a long time, (Cp*RhCl2)2 is coordinated with the bipyridine structure in the coating to achieve the cocatalyst [Cp*Rh(bpy-COOH)H2O] 2+ The porous carbon nitride with the catalyst support formed by the solid loading on the surface is the integrated catalyst.

2. A method for preparing an integrated catalyst as claimed in claim 1, characterized in that: The following steps are involved: Step 1, preparation of a silica template, comprising: preparing a solution phase A: adding ammonia water, anhydrous ethanol and deionized water with a mass concentration of 28% in a container according to a volume ratio of 9:16.25:24.75, and stirring at 900r / min for 10min to obtain a solution phase A; preparing a solution phase B: adding tetraethyl orthosilicate and anhydrous ethanol in a container according to a volume ratio of 1:10.11, and stirring at 900r / min for 10min to obtain a solution phase B; rapidly adding the solution phase B to the solution phase A according to a volume ratio of 1:1, first rapidly stirring, then reducing the speed and continuing stirring to obtain a white suspension, centrifuging the white suspension, washing it three times with ethanol, and drying it at 60°C for 24h to obtain a white block solid, and grinding to obtain silicon oxide microspheres with an average diameter of 360nm±20nm, which are the silica template; Step 2, preparing porous carbon nitride filled with silicon oxide microspheres, comprising: mixing the silicon oxide microspheres obtained in step 1 with melamine in a mass ratio of 1:1 and placing them in a container, adding an appropriate amount of deionized water, wherein the mass volume ratio of the mixture to the deionized water is 300 mg / mL, and stirring at a constant temperature of 60° C. and 1200 r / min until the water is completely evaporated to obtain a white powder after ultrasonic dispersion; transferring all the white powder to a crucible, wrapping it with two layers of tin foil, placing it in a muffle furnace for calcination, cooling it to room temperature and then taking it out to obtain a dark yellow block solid, and the product obtained after grinding is the porous carbon nitride filled with silicon oxide microspheres; Step 3: removing the silicon dioxide template to form porous carbon nitride, comprising: adding the porous carbon nitride filled with silicon oxide microspheres obtained in step 2 to a concentration of 4 mol L -1 The mixture was placed in an ammonium bifluoride solution, etched on a shaker for 24 hours, centrifuged and washed with water three times; dried at 60°C for 24 hours to obtain porous carbon nitride powder, denoted as PCN; Step 4: assembling a coating on the surface of the porous carbon nitride, comprising: ultrasonically dispersing the PCN obtained in step 3 at a concentration of 1 mg mL -1 , a polyallylamine hydrochloride solution with a pH of 7.0, and shaking for 10 minutes to obtain a dispersion; adding a 20mM 2,2'-bipyridine-5,5'-dicarboxylic acid solution with a concentration of 20mM and a pH of 6.0 to the above dispersion at a volume ratio of 8:7, and shaking for 10 minutes; after centrifugation, directly placing it in a vacuum drying oven for drying without washing with water, and the obtained product is a porous carbon nitride with a coating of polyallylamine hydrochloride solution and 2,2'-bipyridine-5,5'-dicarboxylic acid solution assembled on the surface; Step 5: Stabilize the coating, including: preparing a concentration of 300 / 100 mg mL -1 , a 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride / morpholineethanesulfonic acid monohydrate solution with a pH of 5.0, recorded as solution C; ultrasonically disperse the product obtained in step 4 in solution C at a mass volume ratio of 5 mg / mL, shake at room temperature for 2 hours, centrifuge and wash with water once; Step 6: Realize the co-catalyst [Cp*Rh(bpy-COOH)H2O] 2+ The immobilization step comprises: adding 0.5 to 2.0 mg mL -1 The (Cp*RhCl2)2 was shaken at room temperature for 12 h, centrifuged and washed with water three times, then treated with liquid nitrogen and freeze-dried to obtain the surface-supported catalyst [Cp*Rh(bpy-COOH)H2O] 2+ PCN integrated catalyst.

3. The preparation method according to claim 2, characterized in that: In step 1, the rotation speed of the rapid stirring is 900 r / min, and the stirring time is 1 min; the rotation speed of the reduced speed continued stirring is 400 r / min, and the stirring time is 12 h.

4. The preparation method according to claim 2, characterized in that: In step 2, the ultrasonic dispersion process is to place the suspension in an ultrasonic cleaning machine with an ultrasonic frequency of 30 to 50 kHz for ultrasonic treatment for 20 to 30 minutes.

5. The preparation method according to claim 2, characterized in that: In step 2, the calcination process conditions are: calcination at 500°C for 4 hours, and the heating rate from room temperature to 500°C is 5°C / min.

6. The preparation method according to claim 2, characterized in that: In step 4, the drying process conditions are: the drying temperature of the vacuum drying oven is 40° C., and the drying time is 12 h.

7. The preparation method according to claim 2, characterized in that: In step six, the freeze-drying process is: placing in a freeze dryer at a temperature of -40°C for 10-12 hours.

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