A monolithic flow reactor integrating catalysis and detection of 4-nitrophenol and its preparation method and application

Abstract

The application discloses a kind of catalysis and detection 4-nitrophenol integrated into one whole flow reactor and its preparation method and application, it is related to functional material technical field.The method includes loading nano gold particles on cellulose monolith material by reduction reaction, and Au is prepared @CM;Based on the ring-opening reaction between epoxy group and amine group on the surface of cellulose monolith material, modification is carried out, then covalent organic polymer is grafted by using in-situ polymerization reaction, and MP is prepared @CM;Au@CM is connected with MP@CM using the phase separation process of cellulose acetate solution, and assembled into the bifunctional whole flow reactor integrated with catalysis and detection function.The bifunctional flow reactor prepared by the application has better catalytic effect on 4-nitrophenol, and has simple and intuitive detection effect on its catalytic degree, and has great significance in environmental protection, sewage treatment and the like.

Description

Technical Field

[0001] This invention relates to the field of functional materials technology, specifically to an integrated flow reactor that combines catalysis and detection of 4-nitrophenol, its preparation method, and its application. Background Technology

[0002] 4-Nitrophenol is a widely distributed organic pollutant in industrial production. This pollutant is not only highly toxic but also exhibits high water solubility and chemical stability, making it highly susceptible to entering the natural environment and posing a serious threat to ecosystems and human health. Therefore, the rapid and efficient detection and degradation of 4-nitrophenol is of great significance for environmental protection and public health. However, current traditional detection and removal methods generally suffer from low sensitivity, complex operation, or poor environmental friendliness. Therefore, there is an urgent need to develop novel materials and technologies to achieve efficient catalysis and detection of 4-nitrophenol.

[0003] Gold nanoparticles are metallic nanomaterials with sizes ranging from 1 to 100 nm, capable of acting as electron transfer mediators to catalyze the reduction reactions of nitro compounds. They possess the following significant advantages in catalytic reactions: (1) high surface energy and high specific surface area provide abundant active sites, significantly improving the catalytic reaction rate; (2) excellent low-temperature catalytic ability allows them to maintain high catalytic activity even at lower temperatures; (3) excellent chemical stability ensures good tolerance in diverse chemical environments, enabling stable catalytic processes. Based on these advantages, gold nanoparticles have attracted considerable attention in the field of catalysis and are frequently used in various catalysts. However, exposed gold nanoparticles are prone to aggregation, which not only significantly reduces their specific surface area but also significantly decreases the mass transfer rate, reducing the effective contact between the analyte and the active sites of the gold nanoparticles, thereby reducing catalytic efficiency. Therefore, it is urgent to develop a method that can effectively disperse and stabilize gold nanoparticles to prevent aggregation and thus improve their catalytic performance.

[0004] Cellulose, one of the most abundant natural organic polymers, is widely distributed in lignocellulose, cotton tissue, and agricultural waste biomass. Its molecular chains form highly ordered crystalline regions through a hydrogen bond network, constructing a structure that combines high strength, heat resistance, and biocompatibility, making it a highly promising green material. The abundant hydroxyl (-OH) functional groups on the cellulose surface endow it with excellent interfacial bonding properties, allowing it to form stable coordination with gold nanoparticles through electrostatic adsorption or chemical bonding mechanisms. Simultaneously, the monolithic material derived from cellulose exhibits significant dispersion control capabilities, enabling uniform loading of gold nanoparticles in a three-dimensional matrix, thereby significantly increasing the exposed area of ​​catalytic active sites. Notably, based on the renewable nature and green chemistry compatibility of cellulose, the composite catalytic system constructed with gold nanoparticles holds promise for improving the catalytic efficiency of noble metals, significantly reducing catalyst production costs, and addressing the challenges of overall stability and sustainability faced by traditional supported catalysts.

[0005] However, materials loaded solely with gold nanoparticles have limited functionality; the ability to detect the complete catalytic conversion of 4-nitrophenol is also crucial. Covalent organic framework polymers, assembled from organic molecules via covalent bonds, possess a highly ordered structure and exhibit high porosity and specific surface area, which are beneficial for the adsorption and enrichment of target molecules. More importantly, their conjugated systems (such as benzene rings and pyrazine rings) exhibit excellent fluorescence properties, and electron transfer occurs between them and nitro groups with strong electron-withdrawing capabilities, leading to fluorescence quenching. Therefore, covalent organic polymers can serve as sensors to identify the type of substance through fluorescence quenching, enabling the detection of target molecules.

[0006] In summary, although gold nanoparticles are suitable for the catalysis of nitro compounds, they are prone to aggregation; covalent organic framework polymers show great promise in fluorescent probes, but their mechanical stability is poor. Furthermore, no research has yet reported a method for preparing and applying a bifunctional monolithic flow reactor that integrates catalysis and detection of 4-nitrophenol and its derivatives. Summary of the Invention

[0007] To address the shortcomings of the aforementioned background technology, this invention provides an integrated flow reactor for catalysis and detection of 4-nitrophenol, its preparation method, and its application. This method involves loading gold nanoparticles and covalent organic polymers onto a cellulose acetate matrix (CM) to serve as the catalytic device (Au@CM) and detection device (MP@CM) for 4-nitrophenol, respectively. These are assembled through phase separation using a cellulose acetate solution, thereby preparing a cellulose-based integrated flow reactor, MP@CM-Au@CM-MP@CM.

[0008] The first objective of this invention is to provide a method for preparing an integrated flow reactor that combines catalysis and detection of 4-nitrophenol, comprising the following steps: Cellulose acetate monolithic material is obtained by hydrolysis reaction; Au@CM was prepared by loading gold nanoparticles onto monolithic cellulose material via a reduction reaction. The surface of the cellulose monolithic material was modified based on the ring-opening reaction between epoxy groups and amine groups, and then a covalent organic polymer was grafted using an in-situ polymerization reaction to obtain MP@CM; Au@CM and MP@CM are connected by utilizing the phase separation process of cellulose acetate solution to assemble a bifunctional monolithic flow reactor that integrates catalysis and detection functions.

[0009] Preferably, the monolithic cellulose acetate material is prepared by thermally induced phase separation of cellulose acetate.

[0010] Preferably, the Au@CM is prepared according to the following steps: Dissolve HAuCl4 and NaOH in deionized water to obtain HAuCl4 solution; The HAuCl4 solution is circulated through the monolithic cellulose material to obtain Au@CM; The mass ratio of HAuCl4 to NaOH is (0.8~1.2):(5~6). The mass ratio of cellulose monolithic material to HAuCl4 is (0.5~1):(0.08~0.09).

[0011] Preferably, the surface of the cellulose monolithic material is modified with amine groups based on a ring-opening reaction between epoxy groups and amine groups, including: The whole cellulose material was immersed in NaOH methanol solution and kept at room temperature for 3-4 h, then rinsed several times with DMSO; the rinsed material was immersed in epichlorohydrin / dimethyl sulfoxide solution and subjected to grafting epoxy group reaction at 30-40 °C for 3-4 h, and then the reaction product was washed and dried. The dried material is immersed in a polyethyleneimine / ethanol solution at 40-60 ℃ for 20-30 h, and then cleaned and dried. The concentration of NaOH in the methanol solution is 5-8 wt%.

[0012] Preferably, the method involves grafting covalent organic polymers using in-situ polymerization, including: Trialdehyde-based phloroglucinol and 2,2′-bis(trifluoromethyl)diaminobiphenyl were added to a mixed solution of acetic acid and anhydrous trimethylbenzene to obtain a mixed solution. The modified cellulose monolithic material was placed in the mixture and ultrasonically dispersed for 5-10 min. Then it was placed in an oil bath at 120-130 ℃ and reacted for 70-80 h. After the reaction, the product was treated with Soxhlet extraction for 70-80 h and then washed with deionized water until the pH of the washing solution was 6.9-7.1. The molar ratio of the trialdehyde phloroglucinol to 2,2′-bis(trifluoromethyl)diaminobiphenyl is (3~3.5):(4~4.5).

[0013] The second objective of this invention is to provide an integrated flow reactor that combines catalysis and detection of 4-nitrophenol.

[0014] The third objective of this invention is to provide an application of an integral flow reactor in the catalysis and detection of 4-nitrophenol, wherein Au@CM in the integral flow reactor is used for the catalysis of 4-nitrophenol, and MP@CM in the integral flow reactor is used for the detection of 4-nitrophenol.

[0015] The fourth objective of this invention is to provide a method for the catalysis and detection of 4-nitrophenol, comprising: 4-Nitrophenol solid was dissolved in water as a solvent, and 1~1.2 g of sodium borohydride was added to provide hydrogen gas; Rapid catalysis and detection of 4-nitrophenol using an integrated flow reactor; The collected data were analyzed using ultraviolet spectroscopy detection and software colorimetric techniques.

[0016] The fifth objective of this invention is to provide a catalytic and detection device for a 4-nitrophenol catalytic and detection method, including an ultraviolet lamp, a peristaltic pump, and an imaging device with color sampling software; In this design, the integral flow reactor is fixed within a peristaltic pump; The ultraviolet lamp provides an ultraviolet light source, and the peristaltic pump provides power for the transfer of liquid; The camera recorded the changes in the appearance of the monolithic flow reactor during the testing process.

[0017] The sixth objective of this invention is to provide an application of a catalytic and detection device in the catalysis and detection of 4-nitrophenol, comprising: The integral flow reactor is fixed in the peristaltic pump; Set the peristaltic pump to operate at a speed of 3-5 mL / min, and let the mixed solution of 4-nitrophenol and sodium borohydride flow through the integral flow reactor, and collect the effluent. 4-Nitrophenol in the effluent was analyzed using a UV spectrophotometer; The intensity values ​​of the red, green, and blue channels of MP@CM in the monolithic flow reactor were collected using color analysis software, and the fluorescence quenching degree was analyzed.

[0018] Compared with the prior art, the beneficial effects of the present invention are: This invention provides an integrated flow reactor for catalysis and detection of 4-nitrophenol, its preparation method, and its application. The invention uses monolithic cellulose material as a carrier, loading gold nanoparticles and covalent organic polymers respectively, endowing the monolithic cellulose material with the function of simultaneously catalyzing and detecting 4-nitrophenol. Compared with powdered nano-metal particles and covalent organic polymers, Au@CM and MP@CM have advantages such as ease of storage and use, simple preparation process, stable products that are not easily degraded, and can be reused. The integrated flow reactor MP@CM-Au@CM-MP@CM assembled from Au@CM and MP@CM simultaneously possesses catalytic and detection capabilities, making it a novel multifunctional monolithic material.

[0019] The cellulose-based monolithic flow reactor prepared in this invention can be applied to the catalysis and detection of 4-nitrophenol. The Au@CM catalytic device catalyzes the hydrogenation reaction of 4-nitrophenol, while simultaneously using colorimetric software to collect the intensity values ​​of the red, green, and blue channels on the surface of the MP@CM detection device. The degree of fluorescence quenching is then detected to determine the catalytic effect of Au@CM on 4-nitrophenol. Results show that this material has good catalytic performance for 4-nitrophenol and can accurately detect the concentration of 4-nitrophenol in the effluent. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating the preparation process of an integral flow reactor.

[0021] Figure 2 The images are CM scanning electron microscope images (a is magnified 1000 times, b is magnified 5000 times).

[0022] Figure 3 Here are scanning electron microscope images of Au@CM (a is magnified 500 times, b is magnified 1000 times).

[0023] Figure 4 The images are scanning electron microscope images of MP@CM (a is magnified 500 times, b is magnified 1000 times).

[0024] Figure 5 The image shows the X-ray diffraction pattern of Au@CM.

[0025] Figure 6 The UV spectra are for 4-nitrophenol and the effluent after catalysis.

[0026] Figure 7 This is the concentration standard curve for 4-nitrophenol.

[0027] Figure 8The UV spectra of the effluent after Au@CM catalysis of 4-nitrophenol at different flow rates are shown.

[0028] Figure 9 The graph shows the color change of MP@CM with the concentration of 4-nitrophenol.

[0029] Figure 10 This is the standard curve for CR values.

[0030] Figure 11 The images and corresponding UV spectra of MP@CM at a flow rate of 15 mL / min are shown. In the image, a is the appearance of MP@CM at a flow rate of 15 mL / min for 4-nitrophenol, and b is the UV spectrum of the effluent at a flow rate of 15 mL / min for 4-nitrophenol.

[0031] Figure 12 Transmission electron microscope images of Au@CM and S-Au@CM (a and c are magnified 100,000 times, b and d are magnified 400,000 times; a and b are Au@CM, c and d are S-Au@CM).

[0032] Figure 13 The UV spectra of the effluents of 4-nitrophenol catalyzed by Au@CM and S-Au@CM are shown. Detailed Implementation

[0033] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the present invention.

[0034] The purpose of this invention is to provide an integrated flow reactor that combines catalysis and detection of 4-nitrophenol, its preparation method, and its application. By loading gold nanoparticles and covalent organic polymers onto a CM (Chemical Components) to serve as the catalytic device (Au@CM) and the detection device (MP@CM) for 4-nitrophenol, respectively, and assembling them through phase separation of a cellulose acetate solution, an integrated flow reactor (MP@CM-Au@CM-MP@CM) that combines catalysis and detection of 4-nitrophenol is prepared.

[0035] To achieve the above objectives, the first aspect of the present invention provides a method for preparing an integrated flow reactor that combines catalysis and detection of 4-nitrophenol, comprising the following steps: Cellulose acetate monolithic material is obtained by hydrolysis reaction; Au@CM was prepared by loading gold nanoparticles onto monolithic cellulose material via a reduction reaction. The surface of the cellulose monolithic material was modified based on the ring-opening reaction between epoxy groups and amine groups, and then a covalent organic polymer was grafted using an in-situ polymerization reaction to obtain MP@CM; Au@CM and MP@CM are connected by utilizing the phase separation process of cellulose acetate solution to assemble a bifunctional monolithic flow reactor that integrates catalysis and detection functions.

[0036] This invention first prepares CM via thermally induced phase separation and hydrolysis. Then, on one hand, a prepared chloroauric acid solution is repeatedly flowed through CM, and gold nanoparticles are uniformly loaded onto it using a reduction reaction to obtain Au@CM. On the other hand, the surface of CM is modified with amino groups using an epoxy-amine ring-opening reaction. Then, the amino groups on the CM surface react with the aldehyde groups of functional monomers (used to prepare covalent organic polymers) in the reaction system, causing the covalent organic polymer to polymerize in situ on the CM surface, thus preparing a monolithic cellulose material MP@CM loaded with covalent organic polymers. Finally, Au@CM and MP@CM are connected using a phase separation process with a cellulose acetate solution, assembling into an integrated flow reactor (MP@CM-Au@CM-MP@CM) that combines catalysis and detection functions.

[0037] The cellulose acetate monolithic material is prepared by thermally induced phase separation of cellulose acetate.

[0038] The Au@CM is prepared according to the following steps: Dissolve HAuCl4 and NaOH in deionized water to obtain HAuCl4 solution; The HAuCl4 solution is circulated through the monolithic cellulose material to obtain Au@CM; The mass ratio of HAuCl4 to NaOH is (0.8~1.2):(5~6). The mass ratio of cellulose monolithic material to HAuCl4 is (0.5~1):(0.08~0.09).

[0039] Modification of the amine groups on the surface of the cellulose material based on the ring-opening reaction between epoxy groups and amine groups includes: The whole cellulose material was immersed in NaOH methanol solution and kept at room temperature for 3-4 h, then rinsed several times with DMSO; the rinsed material was immersed in epichlorohydrin / dimethyl sulfoxide solution and subjected to grafting epoxy group reaction at 30-40 °C for 3-4 h, and then the reaction product was washed and dried. The dried material is immersed in a polyethyleneimine / ethanol solution at 40-60 ℃ for 20-30 h, and then cleaned and dried. The concentration of NaOH in the methanol solution is 5-8 wt%.

[0040] Grafting covalent organic polymers using in-situ polymerization reactions, including: Trialdehyde phloroglucinol and 2,2′-bis(trifluoromethyl)diaminobiphenyl were added to a mixed solution of acetic acid and anhydrous trimethylbenzene to obtain a mixed solution; The modified cellulose monolithic material was placed in the mixture and ultrasonically dispersed for 5-10 min. Then it was placed in an oil bath at 120-130 ℃ and reacted for 70-80 h. After the reaction, the product was treated with Soxhlet extraction for 70-80 h and then washed with deionized water until the pH of the washing solution was 6.9-7.1. The molar ratio of the trialdehyde phloroglucinol to 2,2′-bis(trifluoromethyl)diaminobiphenyl is (3~3.5):(4~4.5).

[0041] An exemplary method for preparing a bifunctional monolithic flow reactor integrating catalysis and detection of 4-nitrophenol and its derivatives includes: Step 1: Prepare cellulose monolithic materials (CM) using thermally induced phase separation and hydrolysis reaction; Step 2: Load gold nanoparticles onto the monolithic cellulose material via a reduction reaction to obtain the monolithic material Au@CM; Step 3: CM is surface-modified by modifying the amine groups through a ring-opening reaction between epoxy groups and amine groups, and then a covalent organic polymer (MP) is grafted onto it using an in-situ polymerization reaction to obtain MP@CM; Step 4: Using the phase separation process of cellulose acetate solution, Au@CM and MP@CM are connected to assemble a bifunctional integral flow reactor (MP@CM-Au@CM-MP@CM) that integrates catalysis and detection functions.

[0042] The CM is prepared according to the following steps: Preparation of monolithic cellulose acetate material: Add 1~1.5 g of cellulose acetate powder to 5~10 mL N,N The mixture was reacted with dimethylformamide in an oil bath at 85-90 °C for 0.5-1 h, then 7.5-15 mL of n-hexanol was added, and the mixture was stirred in the oil bath at 85-90 °C for another 0.5-1 h. After a homogeneous and transparent solution was formed, it was poured into a mold and placed in a water bath at 20-30 °C for 20-30 h. Finally, the product was dried under vacuum at room temperature for 8-12 h for later use. Preparation of CM: Dissolve 2-4 g of NaOH in 80-100 mL of deionized water to prepare a NaOH aqueous solution. Then, add 3-5 g of whole cellulose acetate material to this solution and react for 3-4 h. This reaction hydrolyzes the acetyl groups in cellulose acetate, restoring the original hydroxyl groups (-OH) of cellulose and significantly improving the hydrophilicity of the material. Subsequently, wash the obtained whole cellulose material with 500-600 mL of deionized water 3-5 times until the washing solution reaches a pH of 6.9-7.1. Finally, place the obtained product in an oven at 60-80 ℃ for drying for 10-12 h to obtain 2-4 g of CM.

[0043] The monolithic cellulose material loaded with gold nanoparticles was prepared according to the following steps: Dissolve 0.8–1.2 g of HAuCl4 and 5–6 g of NaOH in 1200–1300 mL of deionized water. Encapsulate the resulting CM using a heated shrink tube and connect it to a peristaltic pump. Set the flow rate of the peristaltic pump to 10–12 mL / min, allowing the HAuCl4 solution to circulate through 0.1–0.2 g of CM. After reacting for 2.5–3.5 h, wash the resulting Au@CM 2–5 times with 500–600 mL of deionized water until the washing solution has a pH of 6.9–7.1. Finally, dry the product under vacuum at room temperature for 5–8 h for later use.

[0044] The ratio of CM to HAuCl4 is 0.5~1 g: 0.08~0.09 g.

[0045] The MP@CM is prepared according to the following steps: CM pretreatment: Immerse 0.5-1 g of CM in a 5-8 wt% NaOH methanol solution at room temperature for 3-4 h, then rinse with DMSO 3-4 times; subsequently, immerse the material in an epichlorohydrin / dimethyl sulfoxide solution (30-40%, v / v) to graft epoxy groups, and carry out the reaction at 30-40 °C for 3-4 h, then wash with 500-600 mL of deionized water 3-5 times until the washing solution has a pH of 6.9-7.1, and dry the product under vacuum at room temperature for 5-8 h for later use; The dried material was immersed in a polyethyleneimine / ethanol solution (30%~40%, v / v) at 50 °C for 20~30 h. It was then washed 3~5 times with 500~600 mL of deionized water until the pH of the washing solution was 6.9~7.1. The product was then dried under vacuum at room temperature for 5~8 h for later use.

[0046] Preparation of MP@CM: 20-25 mg of 1,3,5-triformylphloroglucinol (Tp) and 20-25 mg of 2,2′-bis(trifluoromethyl)benzidine (TFMB) were added to a mixed solution of acetic acid (0.4-0.6 mL) and anhydrous thiamethoxam (2-3 mL). 0.8-1 g of the pretreated CM was added to this solution and ultrasonically dispersed for 5-10 min, then reacted in an oil bath at 120-130 ℃ for 70-80 h. After the reaction, the obtained MP@CM was treated with Soxhlet extraction for 70-80 h, then washed 3-5 times with 500-600 mL of deionized water until the pH of the washing solution was 6.9-7.1. The product was then dried using a vacuum desiccator for 5-8 h for later use.

[0047] The molar ratio of TFMB to Tp is 3~3.5:4~4.5.

[0048] Preparation of the integral flow reactor Step 1: Add cellulose acetate powder to the glass bottle, then add... N,N Dimethylformamide was used as a solvent, and the mixture was stirred and heated to 90 °C in a water bath until it was completely dissolved to form a homogeneous solution. Then, 7.5 mL of n-hexanol solution was added, and the mixture was stirred continuously until the system was a homogeneous and transparent solution. Step 2: Add the solution dropwise between Au@CM and MP@CM, and fix the system at room temperature for 12 h until the solution completes phase separation. Connect one end of Au@CM to MP@CM. Similarly, take another MP@CM and connect it to the other end of Au@CM to obtain an integrated flow reactor (MP@CM-Au@CM-MP@CM) that integrates catalysis and detection functions.

[0049] A second aspect of the present invention provides an integrated flow reactor that combines catalysis and detection of 4-nitrophenol.

[0050] A third aspect of the present invention provides an application of an integral flow reactor in the catalysis and detection of 4-nitrophenol, wherein Au@CM in the integral flow reactor is used for the catalysis of 4-nitrophenol, and MP@CM in the integral flow reactor is used for the detection of 4-nitrophenol.

[0051] A fourth aspect of the present invention provides a method for the catalysis and detection of 4-nitrophenol, comprising: 4-Nitrophenol solid was dissolved in water as a solvent, and 1~1.2 g of sodium borohydride was added to provide hydrogen gas; Rapid catalysis and detection of 4-nitrophenol using an integrated flow reactor; The collected data were analyzed using ultraviolet spectroscopy detection and software colorimetric techniques.

[0052] The fifth aspect of the present invention provides a catalytic and detection device for a catalytic and detection method of 4-nitrophenol, including an ultraviolet lamp, a peristaltic pump, and an imaging device with color sampling software; In this design, the integral flow reactor is fixed within a peristaltic pump; The ultraviolet lamp provides an ultraviolet light source, and the peristaltic pump provides power for the transfer of liquid; The camera recorded the changes in the appearance of the monolithic flow reactor during the testing process.

[0053] The sixth aspect of this invention provides an application of a catalytic and detection device in the catalysis and detection of 4-nitrophenol, comprising: The integral flow reactor is fixed in the peristaltic pump; Set the peristaltic pump to operate at a speed of 3-5 mL / min, and let the mixed solution of 4-nitrophenol and sodium borohydride flow through the integral flow reactor, and collect the effluent; 4-Nitrophenol in the effluent was analyzed using a UV spectrophotometer; The intensity values ​​of the red, green, and blue channels of MP@CM in the monolithic flow reactor were collected using color analysis software, and the fluorescence quenching degree was analyzed.

[0054] It should be noted that, unless otherwise specified, the experimental methods used in this invention are all conventional methods; and the reagents and materials used, unless otherwise specified, are all commercially available.

[0055] Example 1 (1) Preparation of bifunctional flow reactor A. Preparation of CM Step 1: Add 1 g of cellulose acetate powder to a screw-top glass bottle, then add 10 mL of... N,N Dimethylformamide was used as a good solvent and stirred and heated to 90 °C in a water bath until it was completely dissolved to form a homogeneous solution. Then, 15 mL of n-hexanol was added as a poor solvent and the mixture was placed in a 90 °C oil bath and stirred for 1 h until the system was a homogeneous and transparent solution. Step 2: Pour the solution from Step 1 into a cylindrical mold, and then place it in a water bath at 20 °C for phase separation. After 24 h, phase separation is complete. Demold the resulting monolithic material and perform solvent replacement in anhydrous ethanol for 48 h, replacing the anhydrous ethanol every 2 h for the first three times. After that, collect the sample and vacuum dry it at room temperature to obtain monolithic cellulose acetate material (CA). Step 3: Weigh 2 g of NaOH solid and dissolve it completely in 100 mL of deionized water to obtain a 0.5 mol / L NaOH aqueous solution; cut the CA prepared in Step 2 into small segments of about 1 cm and weigh 1 g of each segment, immerse them completely in the 0.5 mol / L NaOH aqueous solution for hydrolysis for 3 h, then filter out the NaOH aqueous solution, and then wash the obtained cellulose monolithic material three times with 500 mL of deionized water until the washing solution has a pH of 7.1. Finally, place the obtained product in a 60 ℃ oven for drying for 12 h to obtain the cellulose monolithic material CM.

[0056] B. Preparation of Au@CM Step 1: Weigh 5 g of NaOH solid and dissolve it completely in 1250 mL of deionized water to obtain a 0.1 mol / L NaOH aqueous solution. Then add 1 g of HAuCl4 solid to the NaOH aqueous solution to obtain an HAuCl4NaOH solution (2 mmol / L, 50 mL). Step 2: Fix CM in a heat shrink tubing and connect it to a peristaltic pump, setting the pump speed to 10 mL / min; circulate the HAuCl4NaOH solution prepared in Step 1 through 0.15 g of the monolithic cellulose material for 3 h under the action of the peristaltic pump, then wash the material with 500 mL of deionized water until the pH of the washing solution is 7, and then vacuum dry the monolithic cellulose material Au@CM at room temperature for 12 h to obtain the monolithic cellulose material Au@CM loaded with gold nanoparticles.

[0057] C. Preparation of MP@CM Step 1: Weigh 5 g of NaOH solid and dissolve it completely in 100 mL of methanol to obtain a 5 wt% NaOH methanol solution. Then, completely immerse 1 g of CM in the solution at room temperature for 3 h. Rinse the whole material with dimethyl sulfoxide (DMSO) and vacuum dry for later use. Step 2: Measure 30 mL of epichlorohydrin (ECH) and mix it with 70 mL of DMSO to obtain an ECH / DMSO solution (30%, v / v); completely immerse the monolithic material obtained in Step 1 in the above solution to graft epoxy groups, and keep it in an oil bath at 30 °C for 3 h. Then wash the material with 500 mL of deionized water until the pH of the washing solution is 7. Subsequently, vacuum dry the monolithic material at room temperature for 12 h to obtain the monolithic material CM-Epoxy.

[0058] Step 3: Measure 9 mL of polyethyleneimine (PEI) and mix it with 70 mL of ethanol (EtOH) to obtain a PEI / EtOH solution (30%, v / v); completely immerse the CM-Epoxy obtained in Step 2 in the above solution and keep it in an oil bath at 50 °C for 24 h. Then wash the material with 500 mL of deionized water until the pH of the washing solution is 7. Subsequently, vacuum dry the whole material at room temperature for 12 h to obtain the whole material CM-PEI.

[0059] Step 4: Add 24 mg of 2,2′-bis(trifluoromethyl)diaminobiphenyl (TFMB), 21 mg of trialdehyde phloroglucinol (TP), 2000 μL of mesitylene, and 400 μL of acetic acid to a Schlenk tube. Finally, add 1 g of CM-PEI to the Schlenk tube and sonicate for 5 min. Immerse the Schlenk tube containing the mixture in liquid nitrogen for rapid freezing. After it is completely frozen, evacuate the tube until the internal pressure is below 5 Pa and seal it. After the mixture in the tube thaws, fill the tube with nitrogen until the internal pressure returns to normal. Repeat the above steps three times. Then, place the Schlenk tube containing the reactants in an oil bath and heat at 120 °C for 72 h. After the reaction is complete, remove the entire material from the tube and wash it repeatedly with anhydrous ethanol until the washing liquid is clear. Then, vacuum dry it overnight at room temperature to obtain the monolithic cellulose material MP@CM loaded with covalent organic polymer.

[0060] D. Preparation of monolithic flow reactor Step 1: Add 0.5 g of cellulose acetate powder to the glass bottle, then add 5 mL of... N,N Dimethylformamide was used as a solvent, and the mixture was stirred and heated to 90 °C in a water bath until it was completely dissolved to form a homogeneous solution. Then, 7.5 mL of n-hexanol solution was added, and the mixture was stirred continuously until the system was a homogeneous and transparent solution. Step 2: Add the solution dropwise between Au@CM and MP@CM, and fix the system at room temperature for 12 h until phase separation is complete. Connect one end of Au@CM to MP@CM. Similarly, connect another MP@CM to the other end of Au@CM to obtain the integrated flow reactor MP@CM-Au@CM-MP@CM, which integrates catalysis and detection functions. The preparation process of this integrated flow reactor is as follows: Figure 1 As shown.

[0061] Figure 2 This is a scanning electron microscope image of CM. (Example) Figure 2As shown, CM has a coral-like three-dimensional structure with a pore size of approximately 10-40 μm and a rough surface. This three-dimensional structure and simple chemical composition demonstrate that CM is a good supporting material for constructing flow reactors.

[0062] Figure 3 This is a scanning electron microscope image of Au@CM. (See image below.) Figure 3 As shown, Au@CM retains the three-dimensional structure of CM. Since gold particles are good conductors, their loading on the CM surface significantly improves the conductivity of the material and avoids local charge accumulation. Therefore, Au@CM usually has higher contrast in SEM images and the images are clearer.

[0063] Figure 4 This is a scanning electron microscope image of MP@CM. (Example) Figure 4 As shown, MP@CM also retains the three-dimensional structure of CM, with microporous polymers uniformly distributed on the surface of the entire material. However, due to the loading of microporous polymers, the surface roughness of the material increases, and the pore size is approximately 5~10 μm.

[0064] Figure 5 The image shows the XRD pattern of Au@CM. Figure 5 As shown, when CM is loaded with gold nanoparticles, the XRD pattern will show two characteristics: one is the diffraction peak of cellulose, which comes from the crystal structure of cellulose, and a diffraction peak of 22° can be observed before and after loading gold particles. The other is the diffraction peak of gold, which comes from the characteristic peak of gold nanoparticles, located at 38.1° and 44.4°, corresponding to the (111) crystal plane and (200) crystal plane of gold, respectively.

[0065] (2) Au@CM for the catalysis of 4-nitrophenol Catalysis of 4-nitrophenol using Au@CM: 23.1 mg of solid 4-nitrophenol was weighed and added to 50 mL of deionized water, and sonicated for 30 min to dissolve it completely. Then, 1.14 g of NaBH4 was added to provide H2. 0.15 g of Au@CM material was taken and fixed in a heat shrink tube. The mixed solution was flowed through the Au@CM material using a peristaltic pump to carry out the catalytic reaction. The effluent was collected and diluted 30 times with deionized water. The effluent was tested using a UV-Vis spectrophotometer.

[0066] First, the peristaltic pump operating speed was set to 3 mL / min, and 4-nitrophenol and the eluent were analyzed using a UV-Vis spectrophotometer. The results are as follows: Figure 6As shown, before catalysis, 4-nitrophenol produced a signal peak with an absorbance of about 2.2 at 400 nm. After Au@CM catalysis, the signal peak at 400 nm disappeared completely, and a new signal peak was generated at 300 nm, indicating that 4-nitrophenol had been reduced to 4-aminophenol.

[0067] A standard solution of 4-nitrophenol was tested to establish a concentration standard curve. Figure 7 The concentration of 4-nitrophenol in the solution before and after catalysis was calculated based on the standard curve. To investigate the effect of solution flow rate on catalytic efficiency, the flow rate of Au@CM solution was gradually increased from 3.5 mL / min. From 7.8 mL / min onwards, the catalyzed solution was no longer colorless but turned pale yellow. Figure 8 As shown, the absorbance corresponding to the signal peak at 400 nm begins to decrease, indicating that when 4-nitrophenol flows through Au@CM at a rate of 7.8 mL / min, Au@CM can no longer completely reduce 4-nitrophenol to 4-aminophenol.

[0068] (3) MP@CM is used for the detection of 4-nitrophenol. Weigh 231 mg of 4-nitrophenol and dilute to volume in a 500 mL volumetric flask. The concentration of 4-nitrophenol in the flask is now 0.3 mmol / L. Prepare four 50 mL volumetric flasks and add 10, 20, 30, and 40 mL of the above 0.3 mmol / L 4-nitrophenol solution to each flask, respectively. Dilute to volume with deionized water to obtain 4-nitrophenol solutions of 0.06, 0.12, 0.18, and 0.24 mmol / L, respectively. Take a 0.15 g MP@CM and fix it in a heat shrink tubing. Set the peristaltic pump to a speed of 10 mL / min and pass the five different concentrations of 4-nitrophenol solutions through the MP@CM in descending order of concentration. Figure 9 As shown, with the gradual increase of the 4-nitrophenol solution concentration, the color of MP@CM gradually darkened, and the fluorescence quenching phenomenon became increasingly obvious. Colorimetric software was used to compare the colors of MP@CM with different concentrations of 4-nitrophenol solution. Table 1 shows the red values ​​(R values) of MP@CM under different concentrations of 4-nitrophenol solution obtained by the colorimetric software. s ), Green value (G) s ) and blue value (B s The value is calculated using the formula, and the corresponding color ratio (C) is determined. R ), draw as Figure 10 C shown R Standard curve of values.

[0069] (4) Catalysis and detection of 4-nitrophenol using an integral flow reactor The prepared monolithic flow reactor MP@CM-Au@CM-MP@CM was fixed in a heat shrink tubing. A peristaltic pump was set to a speed of 15 mL / min, allowing 0.3 mmol / L 4-nitrophenol to flow through the monolithic flow reactor. Colorimetric software was used to sample the MP@CM at the liquid outlet. The R0 of MP@CM at this point was... s Value, G s Value and B s The values ​​are 87, 89, and 130 respectively, and C is calculated. R The value is 0.5611, according to C R The standard curve showed that the concentration of 4-nitrophenol in the effluent was 0.1798 mmol / L. Figure 11 According to the concentration standard curve of 4-nitrophenol, the absorbance of the ultraviolet spectrum at this point should be 1.037. Simultaneously, the effluent was collected and subjected to ultraviolet spectral analysis, yielding an absorbance of 0.944, which is within the error range. This indicates that the monolithic flow reactor combines catalysis and detection functions.

[0070] Example 2 (1) Preparation of bifunctional flow reactor A. Preparation of CM Step 1: Add 1.5 g of cellulose acetate powder to a screw-top glass bottle, then add 5 mL of... N,N Dimethylformamide was used as a good solvent and heated to 85 °C in a water bath until it was completely dissolved to form a homogeneous solution. Then, 15 mL of n-hexanol was added as a poor solvent and the mixture was placed in an oil bath at 90 °C and stirred for 1 h until the system was a homogeneous and transparent solution. Step 2: Pour the solution from Step 1 into a cylindrical mold, and then place it in a water bath at 20 °C for phase separation. After 24 h, phase separation is complete. Demold the resulting monolithic material and perform solvent replacement in anhydrous ethanol for 48 h, replacing the anhydrous ethanol every 2 h for the first three times. After that, collect the sample and vacuum dry it at room temperature to obtain monolithic cellulose acetate material (CA). Step 3: Weigh 4 g of NaOH solid and dissolve it completely in 50 mL of deionized water to obtain NaOH aqueous solution; cut the CA prepared in Step 2 into small segments of about 1 cm and weigh 1 g of each segment, immerse them completely in NaOH aqueous solution for hydrolysis for 4 h, then filter out the NaOH aqueous solution, and then wash the obtained cellulose monolithic material 5 times with 600 mL of deionized water until the washing solution has a pH of 7.0. Finally, place the obtained product in an 80 ℃ oven for drying for 10 h to obtain cellulose monolithic material CM.

[0071] B. Preparation of Au@CM Step 1: Weigh 6g of NaOH solid and dissolve it completely in 1300 mL of deionized water to obtain NaOH aqueous solution. Then add 0.8g of HAuCl4 solid to the NaOH aqueous solution to obtain HAuCl4NaOH solution. Step 2: Fix CM in a heat shrink tubing and connect it to a peristaltic pump, setting the pump speed to 12 mL / min; circulate the HAuCl4NaOH solution prepared in Step 1 through 0.2 g of the monolithic cellulose material for 3 h under the action of the peristaltic pump, then wash the material with 600 mL of deionized water until the pH of the washing solution is 7, and then vacuum dry the monolithic cellulose material Au@CM at room temperature for 12 h to obtain the monolithic cellulose material Au@CM loaded with gold nanoparticles.

[0072] C. Preparation of MP@CM Step 1: Weigh 5 g of NaOH solid and dissolve it completely in 100 mL of methanol to obtain a 5 wt% NaOH methanol solution. Then, immerse 0.5~0.8 g of CM completely in the solution at room temperature for 3 h. Rinse the whole material with dimethyl sulfoxide (DMSO) and vacuum dry for later use. Step 2: Measure 30 mL of epichlorohydrin (ECH) and mix it with 70 mL of DMSO to obtain an ECH / DMSO solution (30%, v / v); completely immerse the monolithic material obtained in Step 1 in the above solution to graft epoxy groups, and keep it in an oil bath at 30 °C for 3 h. Then wash the material with 500 mL of deionized water until the pH of the washing solution is 7. Subsequently, vacuum dry the monolithic material at room temperature for 12 h to obtain the monolithic material CM-Epoxy.

[0073] Step 3: Measure 9 mL of polyethyleneimine (PEI) and mix it with 70 mL of ethanol (EtOH) to obtain a PEI / EtOH solution (30%, v / v); completely immerse the CM-Epoxy obtained in Step 2 in the above solution and keep it in an oil bath at 50 °C for 24 h. Then wash the material with 500 mL of deionized water until the pH of the washing solution is 7. Subsequently, vacuum dry the whole material at room temperature for 12 h to obtain the whole material CM-PEI.

[0074] Step 4: Add 42 mg of 2,2′-bis(trifluoromethyl)diaminobiphenyl (TFMB), 25 mg of trialdehyde phloroglucinol (TP), 2000 μL of mesitylene, and 400 μL of acetic acid to a Schlenk tube. Finally, add 0.6 g of CM-PEI to the Schlenk tube and sonicate for 5 min. Immerse the Schlenk tube containing the mixture in liquid nitrogen for rapid freezing. After it is completely frozen, evacuate the tube until the internal pressure is below 5 Pa and seal it. After the mixture in the tube thaws, fill the tube with nitrogen until the internal pressure returns to normal. Repeat the above steps three times. Then, place the Schlenk tube containing the reactants in an oil bath and heat at 120 °C for 72 h. After the reaction is complete, remove the entire material from the tube and wash it repeatedly with anhydrous ethanol until the washing liquid is clear. Then, vacuum dry it overnight at room temperature to obtain the monolithic cellulose material MP@CM loaded with covalent organic polymer.

[0075] D. Preparation of monolithic flow reactor Step 1: Add 0.5 g of cellulose acetate powder to the glass bottle, then add 5 mL of... N,N Dimethylformamide was used as a solvent, and the mixture was stirred and heated to 90 °C in a water bath until it was completely dissolved to form a homogeneous solution. Then, 7.5 mL of n-hexanol solution was added, and the mixture was stirred continuously until the system was a homogeneous and transparent solution. Step 2: Add the solution dropwise between Au@CM and MP@CM, and fix the system at room temperature for 12 h until phase separation is complete. Connect one end of Au@CM to MP@CM. Similarly, connect another MP@CM to the other end of Au@CM to obtain the integrated flow reactor MP@CM-Au@CM-MP@CM, which integrates catalysis and detection functions. The preparation process of this integrated flow reactor is as follows: Figure 1 As shown.

[0076] Comparative Example 1 Prepare a 0.2 mmol / L, 50 mL HAuCl4NaOH solution and immerse CM completely in the solution at room temperature for 24 h. Wash CM with 500 mL deionized water until the washing solution pH=7, and then vacuum dry CM at room temperature for 12 h to obtain S-Au@CM, a monolithic cellulose material loaded with gold nanoparticles.

[0077] like Figure 12As shown in the TEM image of the monolithic material Au@CM obtained in Example 1, the size of the gold nanoparticles is 8-12 nm, and no aggregation of the gold nanoparticles is observed. In contrast, the size of the gold nanoparticles in the monolithic material S-Au@CM obtained in this comparative example is approximately 20-30 nm, and aggregation is observed. The prepared S-Au@CM was fixed into a heat shrink tube, and an aqueous solution of 4-nitrophenol (3 mmol / L, 30 mL) was prepared as in Example 2. Subsequently, NaBH4 (1.14 g) was added to provide H2. The mixed solution was passed through a monolithic flow reactor for catalytic reaction. The effluent was collected and diluted 30 times with deionized water. The effluent was tested using a UV-Vis spectrophotometer, and the UV spectra of the effluents of 4-nitrophenol catalyzed by the two materials prepared by different methods were compared. Figure 13 The presence of a distinct signal peak at 400 nm in S-Au@CM indicates that 4-nitrophenol flowing through S-Au@CM was not completely catalyzed to 4-aminophenol. In contrast, the signal peak at 400 nm of Au@CM prepared in Example 1 completely disappeared, proving that 4-nitrophenol flowing through Au@CM was completely catalyzed to 4-aminophenol.

[0078] Table 1 shows the C values ​​of 4-nitrophenol solutions of different concentrations when passing through MP@CM. R value

[0079] C R The formula for calculating the value is as follows:

[0080] In the formula: C R — Color ratio; R r — The red value measured from distilled water; G r — The green value measured from distilled water; B r — The blue color value measured from distilled water; R s — The red values ​​measured from solutions of different concentrations; G s — Green values ​​measured from solutions of different concentrations; B s — Blue values ​​measured from solutions of different concentrations.

[0081] Referring to Table 1, color sampling software was used to sample the MP@CM at the liquid outlet. At this time, the R of MP@CM... s Value, Gs Value and B s The value decreases as the concentration of 4-nitrophenol solution increases, C R The value also decreases accordingly.

[0082] In summary, this invention provides a method for preparing a bifunctional monolithic flow reactor integrating catalysis and detection of 4-nitrophenol and its derivatives. First, a porous monolithic cellulose material (CM) is prepared via thermally induced phase separation and hydrolysis. Then, gold nanoparticles are loaded onto the cellulose monolithic material using a reduction reaction to obtain the monolithic material Au@CM. Next, the surface of CM is modified with amino groups through a ring-opening reaction of epoxy groups, and a covalent organic polymer (MP) is grafted onto it using an in-situ polymerization reaction to obtain MP@CM. Finally, Au@CM and MP@CM are connected via a phase separation process using a cellulose acetate solution to assemble an integrated flow reactor MP@CM-Au@CM-MP@CM that integrates catalysis and detection functions. In this bifunctional flow reactor, when the test solution containing 4-nitrophenol flows through the MP@CM section, a fluorescence quenching reaction occurs; then it flows through the Au@CM section, where gold nanoparticles catalyze 4-nitrophenol to 4-aminophenol; finally, it flows through the MP@CM section, and the presence or absence of a fluorescence quenching reaction determines whether 4-nitrophenol has been completely catalyzed to 4-nitrophenol. The bifunctional flow reactor prepared in this invention exhibits superior catalytic performance for 4-nitrophenol and provides a simple and intuitive detection method for its catalytic degree, which is of great significance in environmental protection and wastewater treatment. This invention describes preferred embodiments and their effects. However, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to include both the preferred embodiments and all changes and modifications falling within the scope of this invention.

[0083] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an integrated flow reactor that combines catalysis and detection of 4-nitrophenol, characterized in that, Includes the following steps: Cellulose acetate monolithic material is obtained by hydrolysis reaction; Au@CM was prepared by loading gold nanoparticles onto monolithic cellulose material via a reduction reaction. The surface of the cellulose monolithic material was modified based on the ring-opening reaction between epoxy groups and amine groups, and then a covalent organic polymer was grafted using an in-situ polymerization reaction to obtain MP@CM; Au@CM and MP@CM are connected by utilizing the phase separation process of cellulose acetate solution to assemble a bifunctional monolithic flow reactor that integrates catalysis and detection functions.

2. The method for preparing the integrated flow reactor for catalysis and detection of 4-nitrophenol according to claim 1, characterized in that, The monolithic cellulose acetate material is prepared by thermally induced phase separation of cellulose acetate.

3. The method for preparing the integrated flow reactor for catalysis and detection of 4-nitrophenol according to claim 1, characterized in that, The Au@CM is prepared according to the following steps: Dissolve HAuCl4 and NaOH in deionized water to obtain HAuCl4 solution; The HAuCl4 solution is circulated through the monolithic cellulose material to obtain Au@CM; The mass ratio of HAuCl4 to NaOH is (0.8~1.2):(5~6). The mass ratio of cellulose monolithic material to HAuCl4 is (0.5~1):(0.08~0.09).

4. The method for preparing the integrated flow reactor for catalysis and detection of 4-nitrophenol according to claim 1, characterized in that, Modification of the amine groups on the surface of the cellulose material based on the ring-opening reaction between epoxy groups and amine groups includes: The whole cellulose material was immersed in NaOH methanol solution and kept at room temperature for 3-4 h, then rinsed several times with DMSO; the rinsed material was immersed in epichlorohydrin / dimethyl sulfoxide solution and subjected to grafting epoxy group reaction at 30-40 °C for 3-4 h, and then the reaction product was washed and dried. The dried material is immersed in a polyethyleneimine / ethanol solution at 40-60 ℃ for 20-30 h, and then cleaned and dried. The concentration of NaOH in the methanol solution is 5-8 wt%.

5. The method for preparing the integrated flow reactor for catalysis and detection of 4-nitrophenol according to claim 1, characterized in that, Grafting covalent organic polymers using in-situ polymerization reactions, including: Trialdehyde-based phloroglucinol and 2,2′-bis(trifluoromethyl)diaminobiphenyl were added to a mixed solution of acetic acid and anhydrous trimethylbenzene to obtain a mixed solution. The modified cellulose monolithic material was placed in the mixture and ultrasonically dispersed for 5-10 min. Then it was placed in an oil bath at 120-130℃ and reacted for 70-80 h. After the reaction, the product was treated with Soxhlet extraction for 70-80 h and then washed with deionized water until the pH of the washing solution was 6.9-7.

1. The molar ratio of the trialdehyde phloroglucinol to 2,2′-bis(trifluoromethyl)diaminobiphenyl is (3~3.5):(4~4.5).

6. An integrated flow reactor for catalysis and detection of 4-nitrophenol, prepared by the method of any one of claims 1 to 5.

7. The application of the integral flow reactor as described in claim 6 in the catalysis and detection of 4-nitrophenol, characterized in that, Au@CM in the monolithic flow reactor is used for the catalysis of 4-nitrophenol, while MP@CM in the monolithic flow reactor is used for the detection of 4-nitrophenol.

8. A catalytic method for the detection of 4-nitrophenol, characterized in that, include: 4-Nitrophenol solid was dissolved in water as a solvent, and 1~1.2 g of sodium borohydride was added to provide hydrogen gas; Rapid catalysis and detection of 4-nitrophenol using the integral flow reactor described in claim 6; The collected data were analyzed using ultraviolet spectroscopy detection and software colorimetric techniques.

9. A catalytic and detection apparatus used in the method of claim 8, characterized in that, This includes ultraviolet lamps, peristaltic pumps, and imaging equipment with color picking software; In this design, the integral flow reactor is fixed within a peristaltic pump; The ultraviolet lamp provides an ultraviolet light source, and the peristaltic pump provides power for the transfer of liquid; The camera recorded the changes in the appearance of the monolithic flow reactor during the testing process.

10. The application of the catalytic and detection device according to claim 9 in the catalysis and detection of 4-nitrophenol, characterized in that, include: The integral flow reactor is fixed in the peristaltic pump; Set the peristaltic pump to operate at a speed of 3-5 mL / min, and let the mixed solution of 4-nitrophenol and sodium borohydride flow through the integral flow reactor, and collect the effluent. 4-Nitrophenol in the effluent was analyzed using a UV spectrophotometer; The intensity values ​​of the red, green, and blue channels of MP@CM in the monolithic flow reactor were collected using color analysis software, and the fluorescence quenching degree was analyzed.

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