A mesoporous Fe-g-C3N4 catalyst support, preparation method thereof and application thereof in enzyme loading

Abstract

The present invention belongs to the technical field of porous materials, and specifically relates to a mesoporous Fe-g-C3N4 catalyst support, a preparation method thereof, and an application thereof in enzyme loading. The mesoporous Fe-g-C3N4 catalyst support provided by the present invention is prepared by a one-step thermal shrinkage polymerization method from potassium ferrocyanide and melamine. The mass fraction of Fe element in the mesoporous Fe-g-C3N4 catalyst support is 1% - 5%; the pore diameter of the mesopores in the mesoporous Fe-g-C3N4 catalyst support is 10 - 30 nm. The mesoporous Fe-g-C3N4 catalyst support not only has excellent photo-Fenton catalytic performance, and its degradation ability for pollutants is significantly better than that of g-C3N4; moreover, the special pore size and the hydroxyl and amino groups on the surface of the Fe-g-C3N4 catalyst support of the present invention enable it to be an excellent support for biological enzymes. While improving the stability of the immobilized enzyme, it does not affect the catalytic activity of the biological enzyme, and has great application prospects in immobilized enzymes.

Description

Technical Field

[0001] The present invention belongs to the technical field of porous materials, and particularly relates to a mesoporous Fe-g-C3N4 catalyst support, a preparation method thereof, and an application thereof in enzyme loading. Background Art

[0002] Graphitic carbon nitride (g-C3N4), as a metal-free semiconductor widely studied in recent years, is composed of a two-dimensional structure of triazine connected by amines, and has advantages such as simple structure, stable chemical properties, and environmental friendliness. Its band gap is 2.7 eV, which is suitable for absorbing visible light, and it is a visible light catalyst that has been widely used in fields such as organic synthesis, photocatalytic degradation of organic pollutants, and photocatalytic water splitting for hydrogen production.

[0003] The "nitrogen tank" in the internal structure of graphitic carbon nitride (g-C3N4) has six nitrogen lone pairs of electrons, which is an ideal site for chemical immobilization of iron species. Nitrogen-rich g-C3N4 can capture iron atoms to form highly dispersed Fe-N X active sites, and the FeN X sites can achieve the maximum utilization of metal sites, thereby improving the catalytic efficiency. For example, Jin Ruirui et al. (Acta Physico-Chimica Sinica, Vol. 30, No. 9, 1706) studied the photocatalytic effects of graphitic carbon nitride doped with 0.14%, 0.4%, and 1% of Fe.

[0004] At present, how to further improve the efficiency of the catalyst and form a multi-functional catalyst by compounding with other materials is a hot research direction. Preparing the material into a porous structure with mesopores / micropores to improve its adsorption and loading capacity is an important research direction; therefore, many scholars have focused on how to improve the structure of graphitic carbon nitride to improve its loading capacity, especially for loading enzymes with catalytic effects.

[0005] Currently, relatively mature mesoporous materials and microporous materials, such as mesoporous carbon, mesoporous silica, etc., generally have pore diameters less than 10 nm. Existing research has shown that the pore size of nanopores in porous materials has a direct impact on the adsorption amount, enzyme activity, and stability of immobilized enzymes. Materials with pore diameters less than 10 nm are not conducive to the loading of macromolecular enzymes. However, currently, graphitic carbon nitride usually has a dense and pore-free structure. Even if some researchers prepare graphitic carbon nitride with a porous structure, its typical pore size range is between 4 and 8 nm, resulting in poor loading capacity for macromolecular enzymes.

[0006] For bioenzyme molecules with a molecular weight of 300 to 3000, the suitable loading pore diameter is 10 to 30 nm. However, there is currently no preparation of enzyme carriers for regulating this pore diameter, especially no graphitic carbon nitride materials with a pore diameter of 10 to 30 nm. This is because in existing graphitic carbon nitride materials, their mesoporous structures are not good, the pore diameters are too large or too small. In particular, it is difficult to prepare graphitic carbon nitride materials rich in pore diameters of 10 to 30 nm, resulting in their enzyme-loading performance not meeting the requirements of the biomedical and enzyme-catalysis fields. Summary of the Invention

[0007] Aiming at the problem of poor mesoporous structure of existing graphitic carbon nitride materials, the purpose of the present invention is to provide a mesoporous Fe-g-C3N4 catalyst carrier, a preparation method thereof, and its application in enzyme loading. The present invention uses potassium ferrocyanide as a raw material, and utilizes the large amount of N2 generated by its thermal decomposition to make the prepared mesoporous Fe-g-C3N4 catalyst carrier rich in excellent mesopores with a pore diameter of 10 to 30 nm. It is an ideal carrier for loading bioenzyme molecules with a molecular weight of 300 to 3000. It not only has a physical adsorption effect on bioenzymes, but also the -OH and -NH2 groups on the surface of the carrier are connected to bioenzymes through chemical bonds, enabling the immobilization of bioenzymes on mesoporous Fe-g-C3N4 without reducing the catalytic activity of the bioenzymes themselves.

[0008] Based on the above purpose, the technical solution adopted by the present invention is as follows:

[0009] In the first aspect, the present invention provides a mesoporous Fe-g-C3N4 catalyst carrier. The mass fraction of Fe element in the mesoporous Fe-g-C3N4 catalyst carrier is 1% to 5%, and the pore diameter of the mesopores in the mesoporous Fe-g-C3N4 catalyst carrier is 10 to 30 nm.

[0010] The "nitrogen tank" in the internal structure of g-C3N4 has six nitrogen lone pairs. Nitrogen-rich g-C3N4 can capture iron atoms to form highly dispersed Fe-N X active sites in the g-C3N4 structure. The FeN X sites can achieve the maximum utilization of metal sites, thereby improving the catalytic efficiency. The mesoporous Fe-g-C3N4 catalyst carrier provided by the present invention has excellent photo-Fenton catalytic performance, and its degradation ability for pollutants is significantly better than that of g-C3N4. The present invention prepares for the first time a Fe-g-C3N4 catalyst carrier with a mesoporous pore diameter of 10 to 30 nm. Its special pore size and surface hydroxyl and amino groups are beneficial to the loading of bioenzymes without affecting the catalytic activity of bioenzymes.

[0011] Preferably, the mass fraction of Fe element in the mesoporous Fe-g-C3N4 catalyst carrier is 2%.

[0012] Preferably, the degradation rate of Rhodamine B by the mesoporous Fe-g-C3N4 catalyst support under visible light reaches 98%.

[0013] Through the experiment on the removal effect of Rhodamine B dye under visible light, it is found that the mesoporous Fe-g-C3N4 catalyst support with 2% iron element content exhibits relatively the best photocatalytic degradation effect, and the degradation rate of Rhodamine B under light illumination is as high as 98%.

[0014] In a second aspect, the present invention provides a method for preparing the above-mentioned mesoporous Fe-g-C3N4 catalyst support, which includes the following steps:

[0015] According to the mass fraction of Fe element in the mesoporous Fe-g-C3N4 catalyst support being 1% - 5%, weigh melamine and potassium ferrocyanide. After mixing melamine and potassium ferrocyanide, heat up to 540 - 560 °C and keep the temperature for reaction for 4 - 6 h. The obtained reaction product is the mesoporous Fe-g-C3N4 catalyst support.

[0016] The present invention uses potassium ferrocyanide as the iron source and pore-forming agent, and synthesizes the mesoporous Fe-g-C3N4 catalyst support through a one-step thermal shrinkage polymerization method. During the thermal polymerization process, potassium ferrocyanide can decompose and release a large amount of N2, which creates favorable conditions for optimizing the pore structure of the material.

[0017] Preferably, the mass fraction of Fe element in the mesoporous Fe-g-C3N4 catalyst support is 2%.

[0018] Through experiments, it is found that the mesoporous Fe-g-C3N4 catalyst support containing 2% Fe exhibits more excellent photo-Fenton reaction performance, and its degradation rate of pollutants under light illumination is as high as 98%.

[0019] Preferably, the heating rate after mixing melamine and potassium ferrocyanide is 5 - 10 °C / min.

[0020] In a third aspect, the present invention provides the application of the above-mentioned mesoporous Fe-g-C3N4 catalyst support in enzyme loading. The enzyme is a bio-enzyme, and the molecular weight of the bio-enzyme is 300 - 3000.

[0021] This is because the mesoporous pore diameter of the mesoporous Fe-g-C3N4 catalyst support prepared by the present invention is 10 - 30 nm, and its pore size matches that of the bio-enzyme with the above-mentioned molecular weight. Moreover, groups such as hydroxyl groups (the hydroxyl groups are derived from the CN heptazine ring structure of carbon nitride and are natural oxygen-doped defect sites introduced during the sintering process) and amino groups on the surface of the mesoporous Fe-g-C3N4 catalyst support are molecularly connected with the bio-enzyme, making the immobilized enzyme have high loading stability and not affecting the catalytic activity of the bio-enzyme.

[0022] Preferably, the bio-enzyme is glucose oxidase.

[0023] Preferably, the bio-enzyme is glucose oxidase, so that the prepared catalyst loaded with glucose oxidase can serve as a spontaneous photo-Fenton system without external addition of H2O2.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] For the first time, the present invention uses potassium ferrocyanide as an iron source and a pore-forming agent, and synthesizes a mesoporous Fe-g-C3N4 catalyst support with melamine through a simple one-step thermal shrinkage polymerization method. The mesoporous Fe-g-C3N4 catalyst support prepared by the present invention not only has excellent photo-Fenton catalytic performance, and its degradation ability for pollutants is significantly better than that of g-C3N4; moreover, the mesoporous pore diameter of the Fe-g-C3N4 catalyst support of the present invention is 10-30 nm, and its special pore size and surface hydroxyl and amino groups enable it to be an excellent support for bio-enzymes. While improving the stability of the immobilized enzyme, it does not affect the catalytic activity of the bio-enzyme and has great application prospects in immobilized enzymes. Description of the Drawings

[0026] Figure 1 shows the catalytic degradation performance of catalysts with different Fe contents for Rhodamine B dye;

[0027] Figure 2 shows the transmission electron microscopy images, EDS-Mapping elemental mapping images and HRTEM images of the mesoporous Fe-g-C3N4 catalyst support and the original g-C3N4 sample;

[0028] Figure 3 shows the nitrogen adsorption-desorption isotherm and pore size distribution curve of the mesoporous Fe-g-C3N4 catalyst support;

[0029] Figure 4 shows the XPS full spectrum of the mesoporous Fe-g-C3N4 catalyst support;

[0030] Figure 5 shows the X-ray diffraction pattern (XRD) and Fourier transform infrared spectrum (FTIR) of different material samples;

[0031] Figure 6 shows the ultraviolet-visible absorption spectrum, Kubelka-Munk function curve, XPS valence band spectrum and energy band structure of different material samples;

[0032] Figure 7 shows the photocurrent response, electrochemical impedance spectrum and photoluminescence spectrum of different material samples. Detailed Embodiments

[0033] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments. Those skilled in the art should understand that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. The test methods used in the examples are all conventional methods unless otherwise specified; the materials, reagents, etc. used, unless otherwise specified, can be obtained from commercial channels.

[0034] Example 1

[0035] Taking the Fe-g-C3N4 catalyst support with a Fe content of 2% as an example, a preparation method of a mesoporous Fe-g-C3N4 catalyst support is provided, including the following steps:

[0036] Weigh 8.49 g of melamine and 1.51 g of potassium ferrocyanide according to the proportion that the iron element content of the finally prepared Fe-g-C3N4 catalyst support is 2%. Mix the two in a covered crucible, and after mixing evenly, put it into a muffle furnace and heat it to 550 °C at a rate of 5 °C / min, keep the temperature for 4 h, and take it out after natural cooling to room temperature. Grind the obtained solid into powder to obtain the Fe-g-C3N4 catalyst support with a Fe content of 2%.

[0037] Example 2

[0038] The purpose of this example is to prepare Fe-g-C3N4 catalyst supports with different Fe contents and analyze their catalytic performance. The specific methods and results are as follows:

[0039] Refer to the preparation method described in Example 1, with the only difference being that the iron element content in the finally prepared Fe-g-C3N4 catalyst support is 1% and 3%.

[0040] At the same time, the original g-C3N4 sample is used as a control, and the preparation method of the original g-C3N4 sample is as follows:

[0041] Put 10 g of melamine powder into a covered crucible and stir evenly, then put it into a muffle furnace and heat it to 550 °C at a rate of 5 °C / min, keep it for 4 hours, take it out after natural cooling to room temperature, and carefully grind the obtained pale yellow solid product into powder to obtain the original g-C3N4 sample.

[0042] The performance analysis of Fe-g-C3N4 catalyst supports with different Fe contents is as follows:

[0043] 1. Catalytic performance analysis of mesoporous Fe-g-C3N4 catalyst support

[0044] In this example, the photocatalytic Fenton reaction performance of the catalyst was analyzed by the catalytic degradation effect of the above catalyst on rhodamine B dye (RhB). The catalytic degradation performance of the catalyst with different Fe contents on rhodamine B dye is as follows Figure 1 As shown, the photocatalytic Fenton performance of the original g-C3N4 is poor, and the degradation efficiency of RhB within 60 minutes is only 70%. The degradation ability of the 1% - 3% Fe-g-C3N4 catalyst support for RhB is significantly better than that of g-C3N4. Among them, the degradation rate of 2% Fe-g-C3N4 can be as high as 98%, which is better than the catalyst supports with other Fe contents. Therefore, we believe that when the mass percentage of iron in the Fe-g-C3N4 catalyst support is 2%, this catalyst support is an efficient photocatalytic Fenton material.

[0045] 2. Transmission electron microscopy and morphological analysis of mesoporous Fe-g-C3N4 catalyst support

[0046] The transmission electron microscopes of the mesoporous Fe-g-C3N4 catalyst support prepared in Example 1 and the original g-C3N4 sample are respectively as follows Figure 2 b and Figure 2 a. The transmission electron microscope (TEM) images in the figure show the microstructures of the Fe-g-C3N4 catalyst support and the traditional bulk g-C3N4 catalyst. Compared with the dense and pore-free bulk g-C3N4, Fe-g-C3N4 shows an obvious hollow mesoporous structure (as shown by the circles in Figure 2 c).

[0047] The EDS-Mapping elemental mapping images and HRTEM images of the mesoporous Fe-g-C3N4 catalyst support prepared in Example 1 are as follows Figure 2 shown, among which, Figure 2 d - Figure 2 g are the EDS-Mapping elemental mapping images of the mesoporous Fe-g-C3N4 catalyst support prepared in Example 1, showing the energy dispersive spectroscopy (EDS) spectrum of Fe-g-C3N4, indicating that C, N, O, and Fe elements are uniformly distributed in the sample.

[0048] Figure 2 h - Figure 2 j are the HRTEM images of the mesoporous Fe-g-C3N4 catalyst support prepared in Example 1. It can be clearly seen from Figure 2 h that Fe-g-C3N4 contains a large number of crystalline particles with a size of less than 3 nm. By measuring the lattice distance of the small nanocrystalline particles in Figure 2 i, it is found that the two typical lattice distances of 0.209 and 0.253 nm correspond to the (400) and (311) planes of Fe3O4 respectively. Therefore, the iron in Fe-g-C3N4 exists in the form of Fe3O4 nanoparticles. In addition,Figure 2 The selected area electron diffraction image (SAED) in j shows bright lattice spots, further confirming the crystalline nature of the highly dispersed Fe3O4 nanoparticles.

[0049] Example 3

[0050] The purpose of this example is to analyze the application performance of the mesoporous Fe-g-C3N4 catalyst support prepared in Example 1 in the immobilization of bioenzymes. The specific methods and results are as follows:

[0051] This example provides a method for loading glucose oxidase (GOD) on the mesoporous Fe-g-C3N4 catalyst support prepared in Example 1. The steps are as follows:

[0052] Mix 1 g of GOD and 1 g of Fe-g-C3N4 powder and dissolve them in 50 ml of deionized water. Place it on a stirrer at room temperature and continuously stir at a speed of 280 rpm for 120 minutes. After stirring, pour the solution into a sample tube and centrifuge it at a speed of 10,000 rpm to collect the sample. Finally, place the collected sample in a vacuum drying oven at 45 °C and dry it for 12 hours to achieve the immobilization of GOD on the Fe-g-C3N4 catalyst support.

[0053] The performance analysis is as follows:

[0054] (1) Nitrogen adsorption-desorption isotherm and pore size distribution curve

[0055] Generally, specific surface area and pore structure are one of the important indicators to measure the reaction activity and adsorption capacity of materials. Figure 3 Figure a shows the N2 adsorption-desorption isotherms and corresponding pore size distribution curves of g-C3N4, Fe-g-C3N4, and Fe-g-C3N4 / GOD. By analyzing the pore structure, the mesoporous characteristics of the Fe-g-C3N4 matrix before and after the loading of glucose oxidase (GOD) can be quantified.

[0056] According to the classification of the International Union of Pure and Applied Chemistry (IUPAC), Figure 3 all three samples in Figure a have typical type-IV isotherms and H3 hysteresis loops. Table 1 lists the specific surface area and pore volume parameters of different materials. Compared with g-C3N4, the specific surface area and pore volume of Fe-g-C3N4 are about 3 times that of the initial g-C3N4, which are 18.965 m 2 g -1 and 0.129 cm 3 g -1 .

[0057] Figure 3The pore size distribution curve in b shows that in the original g-C3N4 sample, the pore size range is mainly distributed around 4-8 nm, while in the Fe-g-C3N4 sample, the pore size range is mainly distributed between 10-26 nm. This result is consistent with the phenomenon observed by TEM.

[0058] In addition, Figure 3 c~ Figure 3 The cumulative pore volume and specific surface area diagrams of g-C3N4 and Fe-g-C3N4 determined by the original density functional theory model in d can more intuitively show that the high-quality mesopore rate around 20 nm in Fe-g-C3N4 is significantly increased compared to g-C3N4. This pore size provides an ideal position and channel for the loading and catalysis of GOD. When GOD is loaded, the pore structure in the Fe-g-C3N4 / GOD material still largely remains in the range of 9-24 nm, which is beneficial to the effective mass transfer of subsequent chemical reactions.

[0059] Table 1 Void structure characteristics of mesoporous Fe-g-C3N4 catalyst support and original g-C3N4 sample

[0060] [[ID=[]]

[0061] (2) X-ray photoelectron spectroscopy (XPS)

[0062] To further reveal the surface composition and corresponding valence states of the Fe-g-C3N4 support, we performed X-ray photoelectron spectroscopy (XPS) measurements on the samples prepared in Example 1. Figure 4 a shows the full spectra of all elements in g-C3N4 and Fe-g-C3N4. In the full spectrum of g-C3N4, it mainly contains three atoms of C, N, and O, while the Fe-g-C3N4 support contains four atoms of C, N, O, and Fe. Since the iron content in Fe-g-C3N4 is very low (2%), the iron peak is weak.

[0063] Figure 4 In b, the XPS C1s spectrum of g-C3N4 can be deconvoluted into two peaks at binding energies of 284.7 eV and 288.1 eV, which are attributed to sp 2 C and the tri-s-triazine structure of N-C=N, respectively. Figure 4 In c, the XPS N1s spectrum of g-C3N4 has four characteristic peaks at binding energies of 398.9, 399.5, 400.9 eV, and 404.9 eV, which can be attributed to the bidentate nitrogen atoms (CN=C), tridentate nitrogen atoms (N-C3), surface amino groups, and charge effects in the aromatic g-C3N4 heterocycle, respectively. Compared with g-C3N4, the peak position offsets of C1s and N1s in the Fe-gC3N4 sample are not large or slightly shift towards the lower binding energy direction. InFigure 4 In (d), the O 1s spectrum shows a characteristic peak at 532.8 eV, which is attributed to surface adsorbed water in g-C3N4 and Fe-g-C3N4. In addition to the peak related to surface adsorbed water, the O 1s spectrum of Fe-g-C3N4 also has a small Fe-O characteristic peak at 530.3 eV, indicating the presence of iron oxide species in the Fe-g-C3N4 support, which can correspond to the Fe3O4 crystal particles observed in TEM.

[0064] Figure 4 In (e), the Fe 2p spectrum shows two broad characteristic peaks at binding energies of ~711 and ~724 eV, which are attributed to Fe 2p 3 / 2 and Fe 2p 1 / 2 . As shown in the figure, these peaks can all be deconvolved into two small peaks related to Fe 3+ and Fe 2+ , indicating that trivalent iron and divalent iron coexist in the Fe-g-C3N4 catalyst support, and the calculated Fe 2+ / Fe 3+ ratio is 1.35, indicating that the catalyst has a good divalent iron-rich surface state in the Fenton reaction.

[0065] Since the convenience of catalyst recycling is also an important aspect of evaluating its performance, we analyzed the vibrating sample magnetometer (VSM) magnetism of the Fe-g-C3N4 / GOD material at room temperature, with the magnetic field range from -20000 to +20000 Oe. As Figure 4 shown in (f), the hysteresis loop of Fe-g-C3N4 / GOD shows that the magnetization curve is consistent with the demagnetization curve, and the remanent magnetization and coercivity tend to zero. This indicates that Fe-g-C3N4 / GOD has typical superparamagnetism and is very similar to superparamagnetic Fe3O4. Due to the very low iron content in Fe-g-C3N4 / GOD, the synthesized Fe3O4 nanocrystals are also few, and the saturation magnetization of Fe-g-C3N4 / GOD is only 0.5 emu / g, but this result can still support the magnetic recycling of the catalyst in water treatment applications.

[0066] (3) X-ray diffraction pattern (XRD) and Fourier transform infrared spectroscopy (FTIR)

[0067] X-ray diffraction, as an effective means of analyzing the crystal structure of particles, is widely used to clarify the chemical structure composition of the material surface. Figure 5a shows the XRD patterns of g-C3N4, Fe-g-C3N4, GOD, and Fe-g-C3N4 / GOD. The XRD pattern of g-C3N4 has two typical obvious peaks at 27.5° and 13.1°, which are the characteristic (002) peak of the interlayer stacking of the aromatic system and the (100) peak corresponding to the interplanar separation, respectively. Compared with GOD, Fe-g-C3N4 / GOD does not show the characteristic peaks of GOD, indicating that GOD is uniformly distributed in the Fe-g-C3N4 support and does not crystallize.

[0068] To further analyze the surface functional group characteristics of g-C3N4, Fe-g-C3N4, GOD, and Fe-g-C3N4 / GOD, Fourier transform infrared spectroscopy (FTIR) was used to characterize the samples, and the results are as Figure 5 shown in Fig. b. The broad peak between 3000 and 3500 cm -1 is caused by the breathing vibration of -OH at the defects of the aromatic ring and the stretching vibration of the terminal -NH2 and =NH amino groups. Compared with Fe-g-C3N4, this broad peak is significantly weakened in Fe-gC3N4 / GOD, indicating that the terminal -NH2 on g-C3N4 may be connected to the -OH on GOD as the original site through an oxidative amination reaction. The absorption peaks in the range of 1200 - 1700 cm -1 are the typical stretching modes of the aromatic carbon nitride heterocycle. The main characteristic peak of GOD at 3350 - 3600 cm -1 appears in the spectrum of Fe-gC3N4 / GOD, indicating that GOD is successfully immobilized on the surface of Fe-g-C3N4.

[0069] (4) Energy band structure analysis

[0070] Since the light absorption performance and energy band structure have a great influence on the catalytic performance, the ultraviolet-visible diffuse reflectance spectrum (UV-vis DRS) of the materials was tested and analyzed in the scanning range of 200 - 800 nm. As Figure 6 shown in Fig. a, the absorption edge of the original g-C3N4 is about 456 nm. With the increase of the iron content in the catalyst, the adsorption range of the catalyst is significantly redshifted. Compared with the original g-C3N4, the absorption edge of Fe-g-C3N4 is redshifted to 478 nm, indicating that the light absorption ability of the Fe-g-C3N4 support has been improved. When GOD enzyme is loaded, the adsorption edge of Fe-g-C3N4 / GOD is further redshifted to 487 nm. This may be due to the large specific surface area and pore structure of this material, thus enhancing its light capture and light absorption ability.

[0071] According to Figure 6The band gaps of g-C3N4, Fe-g-C3N4, and Fe-g-C3N4 / GOD estimated from the Kubelka-Munk function curves in b are approximately 2.72 eV, 2.60 eV, and 2.55 eV, respectively. Compared with pure g-C3N4, the relatively narrow band gaps in Fe-g-C3N4 and Fe-g-C3N4 / GOD enable them to absorb more light energy in a wider spectral range.

[0072] Since the positions of the conduction band and valence band are also crucial for determining the possible reaction pathways during the photocatalytic process, the band gap values calculated from UV-vis DRS, the valence band edge potential (EVB) measured by XPS valence spectra, and the conduction band edge potential (ECB) of the samples were analyzed and compared. As Figure 6 c~ Figure 6 shown in d, the conduction band potential of Fe-g-C3N4 and Fe-g-C3N4 / GOD is more negative than that of the original g-C3N4, indicating that the catalyst can effectively promote the rapid separation of photo-generated electron-hole pairs (e - -h + ). The optimized band positions suggest that Fe-g-C3N4 / GOD can generate not only hydroxyl radicals but also superoxide radicals. The above results indicate that the Fe-g-C3N4 / GOD composite catalyst has strong photocatalytic oxidation potential.

[0073] (5) Electrochemical analysis

[0074] Since the separation rate of photo-generated electron-hole pairs is the key to evaluating the performance of a photo-Fenton catalyst, we tested and analyzed the electron-carrier pairs under photoexcitation through photoluminescence experiments. Figure 7 a Analyzed the transient photocurrent response of the materials. As shown in the figure, compared with g-C3N4, the photocurrent response of Fe-g-C3N4 is significantly enhanced, confirming that Fe-g-C3N4 has a lower recombination rate of photo-generated electron-hole pairs and a higher separation rate. Figure 7 b Analyzed the conductivity and photo-generated charge separation rate of the materials through electrochemical impedance spectroscopy (EIS). The results show that the radius of the Nyquist curve of Fe-g-C3N4 is significantly smaller than that of g-C3N4, indicating that Fe-g-C3N4 has a more excellent electron-hole pair separation efficiency. Compared with g-C3N4, Figure 7 c The photoluminescence spectrum (PL) intensity of Fe-g-C3N4 is significantly reduced, indicating again that the recombination rate of photo-generated electron-hole pairs in the Fe-g-C3N4 catalyst is low. In addition, the Fe-g-C3N4 / GOD catalyst largely retains the electrochemical properties of the Fe-g-C3N4 matrix, indicating that the Fe-g-C3N4 / GOD composite catalyst after loading GOD still has good photoelectrochemical stability.

[0075] Based on the above analysis, it can be seen that in the present invention, potassium ferrocyanide is used as an iron source and a pore-forming agent for the first time, and mesoporous Fe-g-C3N4 catalyst supports are synthesized with melamine through a simple one-step thermal shrinkage polymerization method. The mesoporous Fe-g-C3N4 catalyst supports prepared in the present invention not only have excellent photo-Fenton catalytic performance, and their degradation ability for pollutants is significantly better than that of g-C3N4; moreover, the mesoporous pore size of the Fe-g-C3N4 catalyst supports in the present invention is 10-30 nm, and their special pore size and the hydroxyl and amino groups on the surface enable them to be excellent loading supports for bioenzymes. While improving the stability of the immobilized enzyme, it does not affect the catalytic activity of the bioenzyme, and has great application prospects in immobilized enzymes.

Claims

1. Application of a mesoporous Fe-g-C3N4 catalyst support in enzyme loading, characterized in that, The enzyme is a biological enzyme, and the molecular weight of the biological enzyme is 300 to 3000; the biological enzyme is glucose oxidase; the mass fraction of Fe element in the mesoporous Fe-g-C3N4 catalyst support is 1% to 5%, and the pore diameter of the mesopores in the mesoporous Fe-g-C3N4 catalyst support is 10 to 30 nm.

2. The application according to claim 1, wherein The mass fraction of Fe element in the mesoporous Fe-g-C3N4 catalyst support is 2%.

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