Integral flow reactor integrating catalysis and detection of 4-nitrophenol as well as preparation method and application of integral flow reactor

Abstract

The invention discloses an integral flow reactor integrating catalysis and detection of 4-nitrophenol as well as a preparation method and application of the integral flow reactor, and relates to the technical field of functional materials. The method comprises the following steps: loading gold nanoparticles on a cellulose integral material through a reduction reaction to prepare Au (at) CM; the preparation method comprises the following steps: modifying the surface of a cellulose integral material based on a ring-opening reaction between an epoxy group and an amino group, and then grafting a covalent organic polymer by utilizing an in-situ polymerization reaction to prepare MP (at) CM; the Au (at) CM and the MP (at) CM are connected through the phase separation process of a cellulose acetate solution, and the dual-function integral flow reactor integrating the catalysis function and the detection function is assembled. The difunctional flow reactor prepared by the invention has a better catalytic effect on 4-nitrophenol, has a simple and intuitive detection effect on the catalytic degree of 4-nitrophenol, and has great significance in the aspects of environmental protection, sewage treatment and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of functional materials, and in particular to an integral flow reactor integrating catalysis and detection of 4-nitrophenol, and a preparation method and application thereof. Background Art

[0002] 4-Nitrophenol is an organic pollutant widely found in industrial production. It is not only highly toxic but also highly water-soluble and chemically stable, making it easily enter the natural environment and posing a serious threat to ecosystems and human health. Therefore, the rapid and efficient detection and degradation of 4-nitrophenol are of great significance to environmental protection and human health. However, current traditional detection and removal methods generally suffer from low sensitivity, complex operations, and poor environmental friendliness. Therefore, there is an urgent need to develop new materials and technologies for the efficient catalysis and detection of 4-nitrophenol.

[0003] Gold nanoparticles are a type of metal nanomaterial with a size ranging from 1 to 100 nm. They can act as electron transfer media to catalyze the reduction reaction of nitro compounds. They have 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 enables them to maintain high catalytic activity under low temperature conditions; (3) excellent chemical stability ensures that they have good tolerance in a variety of chemical environments, allowing the catalytic process to occur stably. Based on the above advantages, gold nanoparticles have attracted much attention in the field of catalysis and are often used in various catalysts. However, exposed gold nanoparticles are prone to agglomeration, which not only leads to a significant decrease in their specific surface area, but also significantly reduces the mass transfer rate, reduces the effective contact between the analyte and the active sites of the gold nanoparticles, and thus reduces the catalytic efficiency. Therefore, it is urgent to develop a method that can effectively disperse and stabilize gold nanoparticles to prevent the occurrence of agglomeration and thus improve their catalytic performance.

[0004] Cellulose, one of the most abundant natural organic polymers, is widely distributed in wood fibers, cotton tissue, and agricultural waste biomass. Its molecular chains form highly ordered crystalline regions through a hydrogen-bonded network, creating 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 binding properties, allowing it to form stable coordination with gold nanoparticles through electrostatic adsorption or chemical bonding mechanisms. Furthermore, monolithic materials made from cellulose exhibit remarkable dispersion and controllability, enabling uniform loading of gold nanoparticles within a three-dimensional matrix, significantly increasing the exposed area of catalytically active sites. Notably, due to its renewable nature and compatibility with green chemistry, composite catalytic systems constructed with cellulose and gold nanoparticles are expected to improve the efficiency of precious metal catalysis and significantly reduce catalyst production costs, addressing the overall stability and sustainability challenges faced by traditional supported catalysts.

[0005] However, materials loaded solely with gold nanoparticles have limited functionality, and detecting the complete catalytic conversion of 4-nitrophenol is crucial. Covalent organic framework polymers, assembled from organic molecules via covalent bonds, possess a highly ordered structure, exhibiting high porosity and a high specific surface area, which facilitates the adsorption and enrichment of target molecules. More importantly, their conjugated systems (such as benzene and pyrazine rings) exhibit excellent fluorescence properties, with electron transfer between them and the highly electron-withdrawing nitro group, leading to fluorescence quenching. Therefore, covalent organic polymers can be used as sensors for detecting target molecules through fluorescence quenching.

[0006] In summary, while gold nanoparticles are suitable for the catalysis of nitro compounds, they are prone to aggregation. Covalent organic framework polymers have great application prospects in fluorescent probes, but their mechanical stability is poor. Furthermore, the preparation and application of a dual-function monolithic flow reactor that combines catalysis and detection of 4-nitrophenol and its derivatives has not yet been reported. Summary of the Invention

[0007] To address the shortcomings of the aforementioned background technology, the present invention provides a monolithic flow reactor that integrates catalysis and detection of 4-nitrophenol, as well as its preparation method and application. This method loads gold nanoparticles and a covalent organic polymer onto a cellulose acetate matrix (CM), respectively, to form a catalytic device (Au@CM) and a detection device (MP@CM) for 4-nitrophenol. These devices are then assembled through phase separation of a cellulose acetate solution, resulting in a cellulose-based monolithic flow reactor, MP@CM-Au@CM-MP@CM.

[0008] The first object of the present invention is to provide a method for preparing a monolithic flow reactor integrating catalysis and detection of 4-nitrophenol, comprising the following steps: subjecting the cellulose acetate monolithic material to a hydrolysis reaction to obtain a cellulose monolithic material; Au@CM was prepared by loading gold nanoparticles on the cellulose monolith via a reduction reaction. The surface of the cellulose monolith was modified based on the ring-opening reaction between epoxy groups and amine groups, and then covalent organic polymers were grafted onto it using in situ polymerization to prepare MP@CM. The Au@CM and MP@CM were connected by utilizing the phase separation process of cellulose acetate solution to assemble a dual-function monolithic flow reactor integrating catalytic and detection functions.

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

[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 was circulated through the cellulose monolith to obtain Au@CM; Among them, 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 to modify the amino groups based on a ring-opening reaction between epoxy groups and amino groups, comprising: The cellulose monolith is immersed in a NaOH methanol solution, kept at room temperature for 3-4 hours, and then rinsed with DMSO several times; the rinsed material is immersed in an epichlorohydrin / dimethyl sulfoxide solution at 30-40°C for 3-4 hours to react with the grafted epoxy groups, and then the reaction product is washed and dried; The dried material was immersed in polyethyleneimine / ethanol solution at 40-60 °C for 20-30 h, and then washed and dried; The concentration of NaOH in methanol solution is 5~8 wt%.

[0012] Preferably, the covalent organic polymer is grafted using an in situ polymerization reaction, comprising: adding trialdehyde phloroglucinol and 2,2′-bis(trifluoromethyl)diaminobiphenyl to a mixed solution of acetic acid and anhydrous mesitylene to obtain a mixed solution; The modified cellulose monolith was placed in the mixture and ultrasonically dispersed for 5-10 minutes. The monolith was then placed in an oil bath at 120-130°C for 70-80 hours. After the reaction, the product was subjected to Soxhlet extraction for 70-80 hours 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 object of the present invention is to provide an integral flow reactor that integrates catalysis and detection of 4-nitrophenol.

[0014] A third object of the present invention is to provide an application of a monolithic flow reactor in the catalysis and detection of 4-nitrophenol, wherein the Au@CM in the monolithic flow reactor is used for the catalysis of 4-nitrophenol, and the MP@CM in the monolithic flow reactor is used for the detection of 4-nitrophenol.

[0015] The fourth object of the present invention is to provide a 4-nitrophenol catalysis and detection method, comprising: The 4-nitrophenol solid was dissolved in water as a solvent, and 1-1.2 g of sodium borohydride was added to provide hydrogen; Rapid catalysis and detection of 4-nitrophenol using a monolithic flow reactor; The collected data were analyzed using UV spectroscopy and software colorimetry technology.

[0016] A fifth object of the present invention is to provide a catalytic and detection device used in a catalytic and detection method for 4-nitrophenol, comprising an ultraviolet lamp, a peristaltic pump, and a camera with color-picking software; wherein the monolithic flow reactor is fixed in a peristaltic pump; The ultraviolet lamp provides an ultraviolet light source, and the peristaltic pump provides power for transferring the liquid; The photographing device records the changes in the appearance of the integral flow reactor during the inspection process.

[0017] A sixth object of the present invention is to provide an application of a catalysis and detection device in catalysis and detection of 4-nitrophenol, comprising: The monolithic flow reactor is fixed in a peristaltic pump; The peristaltic pump was set to operate at a speed of 3-5 mL / min to allow the mixed solution of 4-nitrophenol and sodium borohydride to flow through the monolithic flow reactor, and the effluent was collected. The effluent was analyzed for 4-nitrophenol using a UV spectrophotometer; Color analysis software was used to collect the red, green, and blue channel intensity values of MP@CM in the monolithic flow reactor, and the degree of fluorescence quenching was analyzed.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a monolithic flow reactor that integrates catalysis and detection of 4-nitrophenol, as well as its preparation method and application. The present invention utilizes a cellulose monolith as a carrier, loaded with gold nanoparticles and a covalent organic polymer, respectively, to impart to the cellulose monolith the capabilities of simultaneous catalysis and detection of 4-nitrophenol. Compared to powdered nanometal particles and covalent organic polymers, Au@CM and MP@CM offer advantages such as ease of storage and ease of use. Furthermore, the preparation process is simple, and the product is stable and reusable. The monolithic flow reactor MP@CM-Au@CM-MP@CM, assembled from Au@CM and MP@CM, combines both catalytic and detection capabilities, making it a novel multifunctional monolithic material.

[0019] The cellulose-based monolithic flow reactor prepared in this invention can be used for the catalysis and detection of 4-nitrophenol. The Au@CM catalytic device performs a catalytic hydrogenation reaction on 4-nitrophenol. Simultaneously, colorimetric software is used 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 used to determine the catalytic performance of the Au@CM on 4-nitrophenol. The results demonstrate that this material exhibits excellent catalytic performance for 4-nitrophenol and can accurately measure the concentration of 4-nitrophenol in the effluent. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Prepare a flow diagram for the monolithic flow reactor.

[0021] Figure 2 CM scanning electron microscopy images (a is 1000 times magnification, b is 5000 times magnification).

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

[0023] Figure 4 Scanning electron microscopy images of MP@CM (a is 500x magnification, b is 1000x magnification).

[0024] Figure 5 This is the X-ray diffraction spectrum of Au@CM.

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

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

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

[0028] Figure 9 This is the graph showing the color change of MP@CM with the concentration of 4-nitrophenol.

[0029] Figure 10 is the standard curve of CR value.

[0030] Figure 11 Figure 5 is the MP@CM image and the corresponding UV spectrum at a flow rate of 15 mL / min, where a is the appearance of MP@CM when the flow rate of 4-nitrophenol is 15 mL / min, and b is the UV spectrum of the effluent when the flow rate of 4-nitrophenol is 15 mL / min.

[0031] Figure 12 Transmission electron microscopy 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 UV spectra of the effluent from the catalytic reaction of 4-nitrophenol by Au@CM and S-Au@CM. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention is further described below with reference to specific embodiments and drawings, but the embodiments are not intended to limit the present invention.

[0034] The present invention aims to provide a monolithic flow reactor that integrates catalysis and detection of 4-nitrophenol, as well as its preparation method and application. By loading gold nanoparticles and a covalent organic polymer onto CM, respectively, as a catalytic device (Au@CM) and a detection device (MP@CM) for 4-nitrophenol, and assembling them through phase separation of a cellulose acetate solution, a monolithic flow reactor that integrates catalysis and detection of 4-nitrophenol (MP@CM-Au@CM-MP@CM) was prepared.

[0035] In order to achieve the above object, the first aspect of the present invention provides a method for preparing a monolithic flow reactor integrating catalysis and detection of 4-nitrophenol, comprising the following steps: subjecting the cellulose acetate monolithic material to a hydrolysis reaction to obtain a cellulose monolithic material; Au@CM was prepared by loading gold nanoparticles on the cellulose monolith via a reduction reaction. The surface of the cellulose monolith was modified based on the ring-opening reaction between epoxy groups and amine groups, and then covalent organic polymers were grafted onto it using in situ polymerization to prepare MP@CM. The Au@CM and MP@CM were connected by utilizing the phase separation process of cellulose acetate solution to assemble a dual-function monolithic flow reactor integrating catalytic and detection functions.

[0036] The present invention first prepares cellulose matrix (CM) through thermally induced phase separation and hydrolysis. Subsequently, a prepared chloroauric acid solution is repeatedly passed through the CM, and gold nanoparticles are uniformly loaded onto the CM via a reduction reaction to form Au@CM. Furthermore, the CM surface is modified using an epoxy-amine ring-opening reaction to modify amino groups. The CM surface amino groups then react with the aldehyde groups of a functional monomer (used to prepare a covalent organic polymer) in the reaction system, allowing the covalent organic polymer to polymerize in situ on the CM surface. This results in the preparation of a covalent organic polymer-loaded cellulose monolithic material (MP@CM). Finally, the Au@CM and MP@CM are connected via phase separation in a cellulose acetate solution, forming a monolithic flow reactor (MP@CM-Au@CM-MP@CM) integrating catalytic and detection functions.

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

[0038] The Au@CM was prepared according to the following steps: Dissolve HAuCl4 and NaOH in deionized water to obtain HAuCl4 solution; The HAuCl4 solution was circulated through the cellulose monolith to obtain Au@CM; Among them, 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] The surface of the cellulose monolithic material is modified by the ring-opening reaction between the epoxy group and the amine group, including: The cellulose monolith is immersed in a NaOH methanol solution, kept at room temperature for 3-4 hours, and then rinsed with DMSO several times; the rinsed material is immersed in an epichlorohydrin / dimethyl sulfoxide solution at 30-40°C for 3-4 hours to react with the grafted epoxy groups, and then the reaction product is washed and dried; The dried material was immersed in polyethyleneimine / ethanol solution at 40-60 °C for 20-30 h, and then washed and dried; The concentration of NaOH in methanol solution is 5~8 wt%.

[0040] Grafting covalent organic polymers using in situ polymerization, including: adding trialdehyde phloroglucinol and 2,2′-bis(trifluoromethyl)diaminobiphenyl to a mixed solution of acetic acid and anhydrous mesitylene to obtain a mixed solution; The modified cellulose monolith was placed in the mixture and ultrasonically dispersed for 5-10 minutes. The monolith was then placed in an oil bath at 120-130°C for 70-80 hours. After the reaction, the product was subjected to Soxhlet extraction for 70-80 hours 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] Exemplarily, a method for preparing a dual-function monolithic flow reactor integrating catalysis and detection of 4-nitrophenol and its derivatives comprises: Step 1: preparing cellulose monolithic material (CM) by thermally induced phase separation and hydrolysis reaction; Step 2: Loading gold nanoparticles on the cellulose monolithic material through a reduction reaction to prepare the monolithic material Au@CM; Step 3: CM is surface-modified by a ring-opening reaction between epoxy groups and amine groups, and a covalent organic polymer (MP) is grafted onto the surface of ... Step 4: Utilize the phase separation process of the cellulose acetate solution to connect the Au@CM and MP@CM to assemble a dual-function monolithic flow reactor (MP@CM-Au@CM-MP@CM) that integrates catalytic and detection functions.

[0042] The CM was prepared according to the following steps: Preparation of cellulose acetate monolithic material: Add 1-1.5 g of cellulose acetate powder to 5-10 mL N,N -dimethylformamide and place in an 85-90°C oil bath for 0.5-1 h. Then, add 7.5-15 mL of n-hexanol and continue stirring in an 85-90°C oil bath for 0.5-1 h. Once a homogeneous, transparent solution is formed, pour it into a mold and place it in a 20-30°C water bath for 20-30 h. Finally, dry the product in a vacuum dryer at room temperature for 8-12 h before use. Preparation of CM: Dissolve 2-4 g of NaOH in 80-100 mL of deionized water to prepare a NaOH aqueous solution. Place 3-5 g of cellulose acetate monolith in this solution for 3-4 hours. This reaction hydrolyzes the acetyl groups in the cellulose acetate, restoring the original hydroxyl groups (-OH) in the cellulose, significantly increasing the hydrophilicity of the material. The resulting monolith is then washed 3-5 times with 500-600 mL of deionized water until the pH of the washing solution reaches 6.9-7.1. Finally, dry the resulting product in an oven at 60-80°C for 10-12 hours to yield 2-4 g of CM.

[0043] The cellulose monolithic material loaded with nano-gold particles is 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 with heat-shrink tubing and connect it to a peristaltic pump. Set the peristaltic pump flow rate 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 hours, rinse the resulting Au@CM two to five times with 500-600 mL of deionized water until the pH of the washing solution reaches 6.9-7.1. Finally, dry the product in a vacuum dryer at room temperature for 5-8 hours before use.

[0044] The usage 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: 0.5-1 g of CM was soaked in a 5-8 wt% NaOH methanol solution at room temperature for 3-4 h, and then rinsed with DMSO 3-4 times. Subsequently, the material was soaked in an epichlorohydrin / dimethyl sulfoxide solution (30-40%, v / v) to graft epoxy groups. The reaction was carried out at 30-40 °C for 3-4 h, and then washed with 500-600 mL of deionized water 3-5 times until the washing solution had a pH of 6.9-7.1. The product was dried in a vacuum dryer at room temperature for 5-8 h before use. Immerse the dried material in a polyethyleneimine / ethanol solution (30%–40%, v / v) at 50°C for 20–30 h. Rinse with 500–600 mL of deionized water 3–5 times until the pH of the wash solution reaches 6.9–7.1. Dry the product in a vacuum dryer at room temperature for 5–8 h before 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 mixture of acetic acid (0.4–0.6 mL) and anhydrous mesitylene (2–3 mL). 0.8–1 g of pretreated CM was ultrasonically dispersed in this solution for 5–10 min, then reacted in an oil bath at 120–130°C for 70–80 h. After the reaction, the resulting MP@CM was subjected to Soxhlet extraction for 70–80 h and then washed three to five times with 500–600 mL of deionized water until the washings reached a pH of 6.9–7.1. The product was then dried in a vacuum dessicator for 5–8 h before use.

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

[0048] Preparation of the monolithic flow reactor Step 1: Add cellulose acetate powder to the glass bottle, then add N,N -Dimethylformamide was used as the solvent and heated to 90 °C in a water bath with stirring until it was completely dissolved to form a uniform solution. Then 7.5 mL of n-hexanol solution was added and stirred continuously until the system became a uniform and transparent solution. Step 2: Add the solution dropwise between the Au@CM and MP@CM, and allow the system to stand at room temperature for 12 hours until phase separation is complete. Connect one end of the Au@CM to the MP@CM. Similarly, connect another MP@CM to the other end of the Au@CM to create a monolithic flow reactor with integrated catalytic and detection functions (MP@CM-Au@CM-MP@CM).

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

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

[0051] A fourth aspect of the present invention provides a 4-nitrophenol catalysis and detection method, comprising: The 4-nitrophenol solid was dissolved in water as a solvent, and 1-1.2 g of sodium borohydride was added to provide hydrogen; Rapid catalysis and detection of 4-nitrophenol using a monolithic flow reactor; The collected data were analyzed using UV spectroscopy and software colorimetry technology.

[0052] A fifth aspect of the present invention provides a catalytic and detection device used in a 4-nitrophenol catalytic and detection method, comprising an ultraviolet lamp, a peristaltic pump, and a camera with color-picking software; wherein the monolithic flow reactor is fixed in a peristaltic pump; The ultraviolet lamp provides an ultraviolet light source, and the peristaltic pump provides power for transferring the liquid; The photographing device records the changes in the appearance of the integral flow reactor during the inspection process.

[0053] A sixth aspect of the present invention provides an application of a catalytic and detection device in catalytic and detection of 4-nitrophenol, comprising: The monolithic flow reactor is fixed in a peristaltic pump; The peristaltic pump was set to operate at a speed of 3-5 mL / min to allow the mixed solution of 4-nitrophenol and sodium borohydride to flow through the monolithic flow reactor, and the effluent was collected. The effluent was analyzed for 4-nitrophenol using a UV spectrophotometer; Color analysis software was used to collect the red, green, and blue channel intensity values of MP@CM in the monolithic flow reactor, and the degree of fluorescence quenching was analyzed.

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

[0055] Example 1 (1) Preparation of dual-function flow reactor A. Preparation of CM Step 1: Add 1 g of cellulose acetate powder to a screw-cap glass bottle, then add 10 mL N,N -Dimethylformamide was used as a good solvent and heated to 90 °C in a water bath with stirring until it was completely dissolved to form a uniform 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 became a uniform and transparent solution. Step 2: The solution from step 1 was poured into a cylindrical mold and then placed in a 20°C water bath for phase separation. After 24 hours, phase separation was complete. The resulting monolith was demolded and solvent exchanged in anhydrous ethanol for 48 hours, with the anhydrous ethanol replaced every 2 hours for the first three times. Afterwards, the sample was collected and vacuum-dried at room temperature to obtain a cellulose acetate monolith (CA). Step 3: Weigh 2 g of NaOH solid and dissolve it completely in 100 mL of deionized water to obtain a NaOH aqueous solution with a concentration of 0.5 mol / L; cut the CA prepared in step 2 into small segments of about 1 cm and weigh 1 g, completely immerse it in a 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 reaches a pH of 7.1. Finally, place the obtained product in a 60 °C oven for drying for 12 h to obtain a 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 a HAuCl4NaOH solution (2 mmol / L, 50 mL). Step 2: Fix the CM in a heat shrink tube and connect it to a peristaltic pump, setting the peristaltic pump speed to 10 mL / min; circulate the HAuCl4NaOH solution prepared in step 1 through 0.15 g of the cellulose monolith 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 reaches 7. Then, vacuum dry the monolith at room temperature for 12 h to obtain the cellulose monolith loaded with gold nanoparticles, Au@CM.

[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, 1 g of CM was completely immersed in this solution at room temperature for 3 h. The whole material was rinsed with dimethyl sulfoxide (DMSO) and vacuum dried 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 overall material obtained in the above solution to graft epoxy groups, and keep it in a 30°C oil bath for 3 hours, then use 500 mL of deionized water to wash the material until the pH of the washing solution is 7, and then vacuum dry the overall material at room temperature for 12 hours to obtain the overall 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 a 50 °C oil bath for 24 h, then wash the material with 500 mL of deionized water until the pH of the washing solution is 7, and then vacuum dry the entire material at room temperature for 12 h to obtain the entire material CM-PEI.

[0059] Step 4: 24 mg of 2,2′-bis(trifluoromethyl)diaminobenzidine (TFMB), 21 mg of trialdehyde phloroglucinol (TP), 2000 μL of mesitylene and 400 μL of acetic acid were added to the schlenk tube respectively, and finally 1 g of CM-PEI was added to the schlenk tube and ultrasonicated for 5 min; the schlenk tube containing the mixture was immersed in liquid nitrogen and quickly frozen. After it was completely frozen, it was evacuated to an internal pressure of less than 5 Pa and the schlenk tube was sealed. After the mixture in the tube was thawed, nitrogen was filled into the interior until the air pressure in the tube returned to normal. After repeating the above steps three times, the schlenk tube containing the reactants was placed in an oil bath and heated at 120 °C for 72 h. After the reaction was completed, the overall material in the tube was taken out and repeatedly washed with anhydrous ethanol until the washing liquid was clear, and then vacuum dried at room temperature overnight to obtain a cellulose overall material MP@CM loaded with a covalent organic polymer.

[0060] D. Preparation of Monolithic Flow Reactor Step 1: Add 0.5 g of cellulose acetate powder to a glass bottle, then add 5 mL N,N -Dimethylformamide was used as the solvent and heated to 90 °C in a water bath with stirring until it was completely dissolved to form a uniform solution. Then 7.5 mL of n-hexanol solution was added and stirred continuously until the system became a uniform 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 piece of MP@CM and connect it to the other end of Au@CM to obtain a monolithic flow reactor MP@CM-Au@CM-MP@CM with integrated catalytic and detection functions. The preparation process of the monolithic flow reactor is as follows: Figure 1 shown.

[0061] Figure 2 This is the scanning electron microscope image of CM. Figure 2As shown, CM is 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 prove that CM is a good support material for constructing flow reactors.

[0062] Figure 3 This is the scanning electron microscope image of Au@CM. Figure 3 As shown in the figure, Au@CM retains the three-dimensional structure of CM. Since gold particles are good conductors, they significantly improve the conductivity of the material after being loaded on the surface of CM and avoid local charge accumulation. Therefore, the contrast of Au@CM in SEM images is usually higher and the image is clearer.

[0063] Figure 4 This is the scanning electron microscope image of MP@CM. Figure 4 As shown in the figure, MP@CM also retains the three-dimensional structure of CM, and the microporous polymer is evenly distributed on the surface of the entire material. However, due to the loading of the microporous polymer, the surface roughness of the material increases, and the pore size is about 5~10 μm.

[0064] Figure 5 is the XRD spectrum of Au@CM. Figure 5 As shown in Figure 2, when CM is loaded with gold nanoparticles, the XRD pattern will show two features: one is the diffraction peak of cellulose, which comes from the crystalline structure of cellulose. The diffraction peak at 22° can be observed before and after loading with gold particles. The other is the diffraction peak of gold, which comes from the characteristic peak of gold nanoparticles and is located at 38.1° and 44.4°, corresponding to the (111) and (200) crystal planes of gold, respectively.

[0065] (2) Au@CM for the catalysis of 4-nitrophenol Au@CM was used to catalyze 4-nitrophenol: 23.1 mg of 4-nitrophenol solid was weighed and added to 50 mL of deionized water. The solution was completely dissolved by ultrasonication for 30 minutes, followed by the addition of 1.14 g of NaBH4 to provide H2. 0.15 g of Au@CM material was fixed in a heat shrink tubing. A peristaltic pump was used to pass the mixed solution through the Au@CM material for a catalytic reaction. The effluent was collected and diluted 30 times with deionized water. The effluent was tested using an ultraviolet-visible spectrophotometer (UV-vis).

[0066] First, the peristaltic pump was set to operate at a speed of 3 mL / min, and 4-nitrophenol and the effluent were analyzed by UV-visible spectrophotometer. Figure 6As shown in the figure, before catalysis, 4-nitrophenol produced a signal peak with an absorbance of about 2.2 at 400 nm. After catalysis by Au@CM, the signal peak at 400 nm completely disappeared, and a new signal peak was generated at 300 nm, indicating that 4-nitrophenol had been reduced to 4-aminophenol.

[0067] The standard solution of 4-nitrophenol was tested and a concentration standard curve was established ( Figure 7 ), and the concentration of 4-nitrophenol in the solution before and after catalysis was calculated based on the standard curve. In order to explore the effect of solution flow rate on catalytic efficiency, starting from 3.5 mL / min, the flow rate of Au@CM solution was gradually increased. Starting from 7.8 mL / min, the solution after catalysis was no longer colorless, but light yellow; Figure 8 As shown in the figure, the absorbance corresponding to the signal peak at 400 nm began to decrease, indicating that when 4-nitrophenol flowed through Au@CM at a rate of 7.8 mL / min, Au@CM could no longer completely reduce 4-nitrophenol to 4-aminophenol.

[0068] (3) MP@CM for the detection of 4-nitrophenol Weigh 231 mg of 4-nitrophenol and dilute it to a 500 mL volumetric flask. The concentration of 4-nitrophenol in the volumetric 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, respectively. Add deionized water to dilute the volume to obtain 0.06, 0.12, 0.18, and 0.24 mmol / L 4-nitrophenol solutions, respectively. Take a 0.15 g MP@CM and fix it in a heat shrink tube. Set the peristaltic pump to 10 mL / min and flow the above five different concentrations of 4-nitrophenol solutions through the MP@CM in order of concentration. Figure 9 As shown in Figure 1, as the concentration of 4-nitrophenol solution gradually increases, the color of MP@CM gradually darkens and the fluorescence quenching phenomenon becomes increasingly obvious. The color of 4-nitrophenol solution with different concentrations flowing through MP@CM was compared using colorimetric software. Table 1 shows the red value (R) of MP@CM under different concentrations of 4-nitrophenol solution using the colorimetric software. s ), green value (G s ) and blue value (B s ) value, and use the formula to calculate the corresponding color ratio (C R ), draw as Figure 10 C shown R Value standard curve.

[0069] (4) Catalysis and detection of 4-nitrophenol using a monolithic flow reactor The prepared monolithic flow reactor MP@CM-Au@CM-MP@CM was fixed in a heat shrink tube, and the peristaltic pump speed was set to 15 mL / min. 4-nitrophenol with a concentration of 0.3 mmol / L flowed through the monolithic flow reactor. The color of the MP@CM at the liquid outflow end was obtained using colorimetric software. At this time, the R s Value, G s Value and B s The values are 87, 89, and 130 respectively, and the calculated C R The value is 0.5611, according to C R The concentration of 4-nitrophenol in the effluent was 0.1798 mmol / L ( Figure 11 ), the UV absorbance at this point should be 1.037, as shown by the standard curve for 4-nitrophenol concentration. The effluent was collected and analyzed by UV spectroscopy, yielding an absorbance of 0.944, which is within the error range, demonstrating that the monolithic flow reactor possesses both catalytic and detection functions.

[0070] Example 2 (1) Preparation of dual-function flow reactor A. Preparation of CM Step 1: Add 1.5 g of cellulose acetate powder to a screw-cap glass bottle, then add 5 mL N,N -Dimethylformamide was used as a good solvent and heated to 85 °C in a water bath with stirring until it was completely dissolved to form a uniform 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 became a uniform and transparent solution. Step 2: The solution from step 1 was poured into a cylindrical mold and then placed in a 20°C water bath for phase separation. After 24 hours, phase separation was complete. The resulting monolith was demolded and solvent exchanged in anhydrous ethanol for 48 hours, with the anhydrous ethanol replaced every 2 hours for the first three times. Afterwards, the sample was collected and vacuum-dried at room temperature to obtain a cellulose acetate monolith (CA). Step 3: Weigh 4 g of NaOH solid and dissolve it completely in 50 mL of deionized water to obtain a NaOH aqueous solution; cut the CA prepared in step 2 into small segments of about 1 cm and weigh 1 g, completely immerse it in the 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 reaches pH = 7.0. Finally, place the obtained product in an 80 °C oven for drying for 10 h to obtain a cellulose monolithic material CM.

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

[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, 0.5-0.8 g of CM is completely immersed in this solution at room temperature for 3 h. The whole material is rinsed with dimethyl sulfoxide (DMSO) and vacuum-dried 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 overall material obtained in the above solution to graft epoxy groups, and keep it in a 30°C oil bath for 3 hours, then wash the material with 500 mL of deionized water until the pH of the washing solution is 7, and then vacuum dry the overall material at room temperature for 12 hours to obtain the overall 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 a 50 °C oil bath for 24 h, then wash the material with 500 mL of deionized water until the pH of the washing solution is 7, and then vacuum dry the entire material at room temperature for 12 h to obtain the entire material CM-PEI.

[0074] Step 4: 42 mg of 2,2′-bis(trifluoromethyl)diaminobenzidine (TFMB), 25 mg of trialdehyde phloroglucinol (TP), 2000 μL of mesitylene and 400 μL of acetic acid were added to the schlenk tube respectively, and finally 0.6 g of CM-PEI was added to the schlenk tube and ultrasonicated for 5 min; the schlenk tube containing the mixture was immersed in liquid nitrogen and quickly frozen. After it was completely frozen, it was evacuated to an internal pressure of less than 5 Pa and the schlenk tube was sealed. After the mixture in the tube was thawed, nitrogen was filled into the interior until the air pressure in the tube returned to normal. After repeating the above steps three times, the schlenk tube containing the reactants was placed in an oil bath and heated at 120 °C for 72 h. After the reaction was completed, the overall material in the tube was removed and repeatedly washed with anhydrous ethanol until the washing liquid was clear, and then vacuum dried at room temperature overnight to obtain a cellulose overall material MP@CM loaded with a covalent organic polymer.

[0075] D. Preparation of Monolithic Flow Reactor Step 1: Add 0.5 g of cellulose acetate powder to a glass bottle, then add 5 mL N,N -Dimethylformamide was used as the solvent and heated to 90 °C in a water bath with stirring until it was completely dissolved to form a uniform solution. Then 7.5 mL of n-hexanol solution was added and stirred continuously until the system became a uniform 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 piece of MP@CM and connect it to the other end of Au@CM to obtain a monolithic flow reactor MP@CM-Au@CM-MP@CM with integrated catalytic and detection functions. The preparation process of the monolithic flow reactor is as follows: Figure 1 shown.

[0076] Comparative Example 1 Prepare 50 mL of 0.2 mmol / L HAuCl4NaOH solution and completely immerse CM in the solution at room temperature for 24 hours. Wash the CM with 500 mL of deionized water until the pH of the washing solution reaches 7. Then, vacuum dry the CM at room temperature for 12 hours to obtain the cellulose monolithic material S-Au@CM 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 the gold nanoparticles do not show agglomeration. The size of the gold nanoparticles of the monolithic material S-Au@CM obtained in this comparative example is about 20-30 nm, and agglomeration occurs. The prepared S-Au@CM was fixed in a heat shrink tubing, and the 4-nitrophenol aqueous solution (3 mmol / L, 30 mL) in Example 2 was prepared. 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 by ultraviolet-visible spectrophotometer (UV-vis), and the UV spectra of the effluents of the materials prepared by the two different methods for catalytic 4-nitrophenol were compared ( Figure 13 ), S-Au@CM has a clear signal peak at 400 nm, indicating that 4-nitrophenol flowing through S-Au@CM is not completely catalyzed into 4-aminophenol. In contrast, the signal peak at 400 nm of Au@CM prepared in Example 1 completely disappears, proving that 4-nitrophenol flowing through Au@CM has been completely catalyzed into 4-aminophenol.

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

[0079] C R The value is calculated as follows:

[0080] Where: C R — color ratio; R r - Red value measured in distilled water; G r - Green value measured in distilled water; B r - the blue value measured in distilled water; R s —— Red values measured from solutions of different concentrations; G s —— Green value measured from solutions of different concentrations; B s —— Blue values measured from solutions of different concentrations.

[0081] As shown in Table 1, the color of MP@CM at the liquid outflow end is picked using the color picking software. s Value, Gs Value and B s The value decreases with the increase of 4-nitrophenol solution concentration, C R The value also decreases.

[0082] In summary, the present invention provides a method for preparing a dual-function monolithic flow reactor that integrates catalysis and detection of 4-nitrophenol and its derivatives. First, a cellulose porous monolithic material (CM) is prepared by thermally induced phase separation and hydrolysis reaction. Then, gold nanoparticles are loaded on the cellulose monolithic material by a reduction reaction to prepare the monolithic material Au@CM. Second, the CM is surface-modified to modify amino groups by a ring-opening reaction of epoxy groups, and a covalent organic polymer (MP) is grafted by in situ polymerization to prepare MP@CM. Finally, the Au@CM and MP@CM are connected by the phase separation process of a cellulose acetate solution to assemble the MP@CM-Au@CM-MP@CM, an integrated flow reactor with integrated catalytic and detection functions. In this dual-function flow reactor, when the test liquid containing 4-nitrophenol flows through the MP@CM section, a fluorescence quenching reaction occurs; then it flows through the Au@CM section, where the 4-nitrophenol is catalyzed into 4-aminophenol using gold nanoparticles; finally, it flows through the MP@CM section, and the occurrence of a fluorescence quenching reaction determines whether the 4-nitrophenol has been completely catalyzed into 4-nitrophenol. The dual-function flow reactor prepared by the present invention has a relatively good catalytic effect on 4-nitrophenol and a simple and intuitive detection effect for its catalytic degree, which is of great significance in environmental protection, sewage treatment and other aspects. The present invention describes preferred embodiments and their effects. However, those skilled in the art, once informed of the basic inventive concept, may make additional changes and modifications to these embodiments. Therefore, it is intended that the appended claims be interpreted to include the preferred embodiments as well as all changes and modifications that fall within the scope of the invention.

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

Claims

1. A method for preparing a monolithic flow reactor integrating catalysis and detection of 4-nitrophenol, characterized in that: The following steps are involved: subjecting the cellulose acetate monolithic material to a hydrolysis reaction to obtain a cellulose monolithic material; Au@CM was prepared by loading gold nanoparticles on the cellulose monolith via a reduction reaction. The surface of the cellulose monolith was modified based on the ring-opening reaction between epoxy groups and amine groups, and then covalent organic polymers were grafted onto it using in situ polymerization to prepare MP@CM. The Au@CM and MP@CM were connected by utilizing the phase separation process of cellulose acetate solution to assemble a dual-function monolithic flow reactor integrating catalytic and detection functions.

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

3. The method for preparing a monolithic flow reactor integrating catalysis and detection of 4-nitrophenol according to claim 1, characterized in that: The Au@CM was prepared according to the following steps: Dissolve HAuCl4 and NaOH in deionized water to obtain HAuCl4 solution; The HAuCl4 solution was circulated through the cellulose monolith to obtain Au@CM; Among them, 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 a monolithic flow reactor integrating catalysis and detection of 4-nitrophenol according to claim 1, characterized in that: The surface of the cellulose monolithic material is modified by the ring-opening reaction between the epoxy group and the amine group, including: The cellulose monolith is immersed in a NaOH methanol solution, kept at room temperature for 3-4 hours, and then rinsed with DMSO several times; the rinsed material is immersed in an epichlorohydrin / dimethyl sulfoxide solution at 30-40°C for 3-4 hours to react with the grafted epoxy groups, and then the reaction product is washed and dried; The dried material was immersed in polyethyleneimine / ethanol solution at 40-60 °C for 20-30 h, and then washed and dried; The concentration of NaOH in methanol solution is 5~8 wt%.

5. The method for preparing a monolithic flow reactor integrating catalysis and detection of 4-nitrophenol according to claim 1, characterized in that: Grafting covalent organic polymers using in situ polymerization, including: adding trialdehyde phloroglucinol and 2,2′-bis(trifluoromethyl)diaminobiphenyl to a mixed solution of acetic acid and anhydrous mesitylene to obtain a mixed solution; The modified cellulose monolithic material was placed in the mixed solution and ultrasonically dispersed for 5-10 minutes. The monolithic material was then placed in an oil bath at 120-130°C and reacted for 70-80 hours. After the reaction, the product was subjected to Soxhlet extraction for 70-80 hours 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 integral flow reactor integrating catalysis and detection of 4-nitrophenol, prepared by the method according to any one of claims 1 to 5.

7. Use of the monolithic flow reactor according to claim 6 in catalysis and detection of 4-nitrophenol, characterized in that: Au@CM in the monolithic flow reactor was used for the catalysis of 4-nitrophenol, and MP@CM in the monolithic flow reactor was used for the detection of 4-nitrophenol.

8. A 4-nitrophenol catalysis and detection method, characterized in that: include: The 4-nitrophenol solid was dissolved in water as a solvent, and 1-1.2 g of sodium borohydride was added to provide hydrogen; Rapid catalysis and detection of 4-nitrophenol using the monolithic flow reactor according to claim 6; The collected data were analyzed using UV spectroscopy and software colorimetry technology.

9. A catalytic and detection device used in the method according to claim 8, characterized in that: Includes UV lamp, peristaltic pump and camera with color picking software; wherein the monolithic flow reactor is fixed in a peristaltic pump; The ultraviolet lamp provides an ultraviolet light source, and the peristaltic pump provides power for transferring the liquid; The photographing device records the changes in the appearance of the integral flow reactor during the inspection process.

10. Use of the catalysis and detection device according to claim 9 in catalysis and detection of 4-nitrophenol, characterized in that: include: The monolithic flow reactor is fixed in a peristaltic pump; The peristaltic pump was set to operate at a speed of 3-5 mL / min to allow the mixed solution of 4-nitrophenol and sodium borohydride to flow through the monolithic flow reactor, and the effluent was collected. The effluent was analyzed for 4-nitrophenol using a UV spectrophotometer; Color analysis software was used to collect the red, green, and blue channel intensity values of MP@CM in the monolithic flow reactor, and the degree of fluorescence quenching was analyzed.

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