On-line analysis material for chlorobenzene impurities and preparation method thereof

Abstract

This invention belongs to the field of online analysis and detection, and provides an online analytical material for chlorobenzene impurities and its preparation method. The invention employs a core-shell-skin structure composite particle with zirconium-based metal-organic framework nanocrystals as the core, a covalent organic framework as the shell, and a molecularly imprinted polymer as the skin, synergistically constructing a gradient functional composite coating on a disulfide-bonded dynamic organosilicon network matrix and immobilizing it on a silica carrier. This achieves a synergistic balance between high recognition site density and uniform coatability, high adhesion, wear resistance, erosion resistance, and low mass transfer resistance with rapid response, as well as dynamic self-healing function and long-term structural stability under acid / solvent / thermal-vacuum conditions. It solves the problem of simultaneously improving sensitivity, response speed, repeatability, and service life, and has wide application value in the online analysis of chlorobenzene impurities in petrochemical, fine chemical, and online environmental monitoring fields.

Description

Technical Field

[0001] This invention relates to the field of online analytical detection materials technology, specifically to an online analytical material for chlorobenzene impurities and its preparation method. Background Technology

[0002] Chlorobenzene, as an important basic chemical raw material and intermediate, is widely used in the fine chemical production processes of industries such as pesticides, pharmaceuticals, dyes, and polymer materials. In these industrial production scenarios, the concentration level of chlorobenzene impurities in the product logistics directly affects product quality indicators and the stability of reaction processes. Furthermore, excessive chlorobenzene emissions also bring corresponding safety hazards and environmental compliance risks. The introduction of online analysis technology makes real-time, continuous, and quantitative monitoring of chlorobenzene impurities possible, which is of great value for ensuring product quality, optimizing process operating parameters, and achieving green production. The core of achieving efficient online analysis lies in developing high-performance functional analytical materials. These materials need to have high selectivity for chlorobenzene to effectively distinguish target analytes in complex aromatic hydrocarbon matrices, sufficient enrichment sensitivity to meet trace online monitoring needs, rapid response kinetics to support real-time online operation, excellent tolerance and stability to production process environments (including acidic media, organic solvent vapors, high temperatures, and periodic vacuum conditions) to ensure long-term continuous and reliable use, and high analytical repeatability to meet the stringent requirements of industrial process quality control. Therefore, developing an online chlorobenzene analysis material that integrates high recognition sensitivity, rapid response, excellent durability and stability, and high analytical repeatability has significant scientific research value and industrial application significance.

[0003] Currently, some progress has been made in the research of functional coating materials for online identification and enrichment of chlorobenzene-based volatile organic compounds, but several key technical bottlenecks remain unresolved. For example, Chinese patent CN101717511A discloses an organosilicon functional material and its preparation method, but it suffers from insufficient elasticity and dynamic self-healing ability of the organosilicon network after curing. Furthermore, under long-term contact with acidic process media or organic solvents, the network structure gradually degrades, leading to continuous baseline drift in the analytical signal. Additionally, there is an irreconcilable mechanistic contradiction between the mass transfer resistance introduced by the highly cross-linked cured network and the requirement for rapid online response. These shortcomings fundamentally limit the simultaneous improvement of sensitivity, response speed, repeatability, and service life of existing materials. Summary of the Invention

[0004] The purpose of this invention is to provide an online analytical material for chlorobenzene impurities and its preparation method, which solves the pain points of current online enrichment / identification coating materials, which are difficult to balance between high filler density and high identification site density and low viscosity coating uniformity, the mutual constraints between high adhesion, wear resistance and erosion resistance and low mass transfer resistance and fast response, and the mechanistic contradiction between the self-healing requirements of dynamic reversible organosilicon networks and the long-term structural and signal baseline stability under acid / solvent / thermal-vacuum conditions, resulting in the inability to simultaneously improve sensitivity, response speed, repeatability and lifetime.

[0005] This invention synergistically integrates molecular recognition functional units (Zr-MOF@COF@MIP composite particles) with dynamic mechanical matrix functions (dynamic organosilicon network matrix containing disulfide bonds) in a composite coating. This enables the functional particles to achieve uniform dispersion and high-density fixation under high loading conditions. At the same time, the coating has a synergistic balance of dynamic self-healing and low mass transfer resistance. The functional components reinforce each other, and the overall performance significantly exceeds the simple superposition of the effects of individual components applied independently, fundamentally solving the aforementioned restrictive contradictions.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A material for online analysis of chlorobenzene impurities includes a silica support and a composite coating immobilized on the surface of the silica support; the composite coating includes a dynamic organosilicon network matrix and composite particles dispersed in the dynamic organosilicon network matrix.

[0008] The composite particles are Zr-MOF@COF@MIP composite particles. The Zr-MOF@COF@MIP composite particles are core-shell-skin structure composite particles with Zr-MOF nanocrystals as the core, covalent organic framework COF as the coating shell, and molecularly imprinted polymer MIP as the outermost skin layer. Zr-MOF is a zirconium-based metal-organic framework, COF is a covalent organic framework, and MIP is a molecularly imprinted polymer.

[0009] The Zr-MOF@COF@MIP composite particles have a mass fraction of 10–70 wt%, which is based on the total mass of the dynamic organosilicon network matrix and the Zr-MOF@COF@MIP composite particles in the composite coating; the dynamic organosilicon network matrix is ​​obtained by curing a dynamic organosilicon sol intermediate, and the dynamic organosilicon network matrix contains a disulfide bond structure introduced by bis[3-(triethoxysilyl)propyl] disulfide; the median particle size of the Zr-MOF@COF@MIP composite particles is 100–500 nm, and the MIP skin thickness of the Zr-MOF@COF@MIP composite particles is 20–200 nm.

[0010] Furthermore, the dynamic organosilicon sol intermediate is prepared through the following steps:

[0011] A1. Raw materials: tetraethyl orthosilicate, methyltrimethoxysilane, bis[3-(triethoxysilyl)propyl]disulfide, 3-aminopropyltriethoxysilane, hydrochloric acid, anhydrous ethanol, deionized water;

[0012] A2. Proportioning: Based on the total molar amount of tetraethyl orthosilicate, methyltrimethoxysilane, bis[3-(triethoxysilyl)propyl]disulfide, and 3-aminopropyltriethoxysilane, tetraethyl orthosilicate accounts for 30–70 mol%, methyltrimethoxysilane accounts for 10–40 mol%, bis[3-(triethoxysilyl)propyl]disulfide accounts for 5–30 mol%, and 3-aminopropyltriethoxysilane accounts for 1–15 mol%, and the sum of the molar percentages of the above four components is 100 mol%; the molar ratio of the total molar amount to deionized water is 1:2–6;

[0013] A3. Hydrolysis and condensation: The silanes described in A2 are mixed in the specified proportions to obtain a silane mixture; hydrochloric acid is added to deionized water to prepare an acidic aqueous solution, and the pH is controlled at 1.5–3.5 at 25°C. The acidic aqueous solution is added to the silane mixture at 10–40°C and reacted for 0.5–3 hours. Then anhydrous ethanol is added and the reaction continues for 1–12 hours. The amount of anhydrous ethanol added is such that the solid content of the sol described in step A4 is 5–30 wt%.

[0014] A4. Endpoint criterion: The reaction is terminated when the solid content of the sol is 5–30 wt% and no visible precipitate is found.

[0015] A5. Post-processing and quality control: The dynamic organosilicon sol intermediate was obtained by filtration. The pore size of the filter membrane used for filtration was 0.22–5µm. The dynamic organosilicon sol intermediate was considered qualified if it did not gel after standing for 168–720 hours under closed conditions.

[0016] Furthermore, the Zr-MOF nanocrystals in the Zr-MOF@COF@MIP composite particles are Cl / N co-modified Zr-MOF nanocrystals, which are prepared through the following steps, wherein Cl is chlorine and N is nitrogen:

[0017] B1. Raw materials: zirconium tetrachloride, 2-aminoterephthalic acid, 2-chloroterephthalic acid, N,N-dimethylformamide, glacial acetic acid, deionized water, nitrogen;

[0018] B2. Ratio: The ligands are 2-aminoterephthalic acid and 2-chloroterephthalic acid; based on the total molar number of ligands, 2-aminoterephthalic acid accounts for 10–70 mol%, and 2-chloroterephthalic acid accounts for 30–90 mol%, and the sum of the molar percentages of the above two is 100 mol%; the total molar ratio of zirconium tetrachloride to the total ligands is 1:0.8–1.5;

[0019] B3. Solvent-thermal reaction: Under nitrogen protection, zirconium tetrachloride, the ligand, N,N-dimethylformamide, deionized water and glacial acetic acid are mixed. The molar ratio of glacial acetic acid to zirconium tetrachloride is 10–200:1, and the volume ratio of N,N-dimethylformamide to deionized water is 95:5 to 60:40. After sealing, the mixture is reacted at 80–130°C for 6–24 h.

[0020] B4. Endpoint Criteria: After the reaction is complete, cool to room temperature, centrifuge, with a relative centrifugal force of 3000–20000 × g, a centrifugation time of 5–30 min, and a centrifugation temperature of 15–30 °C. Wash with N,N-dimethylformamide and anhydrous ethanol alternately 3–8 times, with the volume ratio of N,N-dimethylformamide or anhydrous ethanol to the mass of the solid to be washed being 10–100 mL:1 g each time, until the pH of the supernatant from the last wash is 5.5–7.5 when it is mixed with deionized water at a volume ratio of 1:1 and measured at 25 °C.

[0021] B5. Post-processing and quality control: Vacuum drying at 80–140℃ and a vacuum degree not exceeding 10kPa for 6–24h yields Cl / N co-modified Zr-MOF nanocrystals; the median particle size of Cl / N co-modified Zr-MOF nanocrystals is 50–300nm to be considered qualified.

[0022] Furthermore, the Cl / N co-modified Zr-MOF nanocrystals in the Zr-MOF@COF@MIP composite particles are coated with a covalent organic framework COF shell, forming the Zr-MOF@COF core-shell intermediate, which is prepared through the following steps:

[0023] C1. Raw materials: Cl / N co-modified Zr-MOF nanocrystals, 2,4,6-tricarboxymethyl phloroglucinol, p-phenylenediamine, glacial acetic acid, N,N-dimethylformamide, deionized water, nitrogen;

[0024] C2. Ratio: The molar ratio of 2,4,6-tricarboxymethyl phloroglucinol to p-phenylenediamine is 1:1.0–2.0; based on the mass of Cl / N co-modified Zr-MOF nanocrystals, the total mass of 2,4,6-tricarboxymethyl phloroglucinol and p-phenylenediamine is 0.2–2.0 times the mass of Cl / N co-modified Zr-MOF nanocrystals;

[0025] C3. In-situ growth: Under nitrogen protection, Cl / N co-modified Zr-MOF nanocrystals were dispersed in a mixed solvent of N,N-dimethylformamide and deionized water, wherein the volume ratio of N,N-dimethylformamide to deionized water was 95:5 to 60:40. Glacial acetic acid was added and the pH of the system was controlled at 3.0–6.0 at 25°C. Subsequently, 2,4,6-tricarboxymethyl phloroglucinol and p-phenylenediamine were added. After sealing, the reaction was carried out at 60–120°C for 6–24 h.

[0026] C4. Endpoint Criteria: After the reaction is complete, centrifuge at a relative centrifugal force of 3000–20000 × g, a centrifugation time of 5–30 min, and a centrifugation temperature of 15–30 °C. Wash with anhydrous ethanol 3–10 times, with the volume ratio of anhydrous ethanol to the mass of the solid to be washed being 10–100 mL: 1 g each time, until the pH of the final wash solution mixed with deionized water at a volume ratio of 1:1 is 5.5–7.5 as measured at 25 °C.

[0027] C5. Post-processing and quality control: Zr-MOF@COF core-shell intermediates are obtained by vacuum drying at 60–120℃ and a vacuum degree not exceeding 10kPa for 6–24h; the covalent organic framework shell thickness is 5–50nm and the shell continuity rate is ≥70% to be qualified.

[0028] Furthermore, the Zr-MOF@COF@MIP composite particles are prepared using the Zr-MOF@COF core-shell intermediate as a precursor through the following steps:

[0029] D1. Raw materials: Zr-MOF@COF core-shell intermediate, 3-(methacryloyloxy)propyltrimethoxysilane, chlorobenzene, 4-vinylpyridine, ethylene glycol dimethacrylate, 2,2'-azobisisobutyronitrile, anhydrous ethanol, deionized water, methanol, glacial acetic acid, nitrogen;

[0030] D2. Introduction of surface initiation sites: The Zr-MOF@COF core-shell intermediate was dispersed in a mixed solvent of anhydrous ethanol and deionized water, wherein the volume ratio of anhydrous ethanol to deionized water was 95:5 to 50:50. 3-(methacryloyloxy)propyltrimethoxysilane was added, wherein the amount of 3-(methacryloyloxy)propyltrimethoxysilane added was 1–30 wt% of the mass of the Zr-MOF@COF core-shell intermediate. The pH was controlled at 3.5–5.5 at 25 °C, and the reaction was carried out at 20–60 °C for 1–8 h.

[0031] D3. Surface molecular imprinting polymerization: Under nitrogen protection, chlorobenzene, 4-vinylpyridine, ethylene glycol dimethacrylate and 2,2'-azobisisobutyronitrile were added to the system obtained in D2. The molar ratio of chlorobenzene to 4-vinylpyridine was 1:1.0–6.0, and the molar ratio of 4-vinylpyridine to ethylene glycol dimethacrylate was 1:2.0–20.0. The amount of 2,2'-azobisisobutyronitrile added was 0.1–2.0 wt% of the total mass of 4-vinylpyridine and ethylene glycol dimethacrylate. The polymerization was carried out under closed conditions at 50–80°C and a stirring speed of 200–1000 rpm for 2–12 h to obtain a template-containing molecularly imprinted skin.

[0032] D4. Template Removal: Wash 3–20 times with a gradient of methanol and glacial acetic acid eluent. The gradient is as follows: first wash with an eluent with a methanol to glacial acetic acid volume ratio of 7:3, then wash with an eluent with a volume ratio of 9:1, and finally wash with pure methanol. The volume ratio of the eluent used in each washing step to the mass ratio of the Zr-MOF@COF@MIP composite particles is 10–200 mL:1 g, until the residual amount of chlorobenzene in the Zr-MOF@COF@MIP composite particles is ≤0.05 wt% on a dry basis.

[0033] D5. Post-processing and quality control: Zr-MOF@COF@MIP composite particles are obtained by vacuum drying at 40–120℃ and a vacuum degree not exceeding 10kPa for 6–24h; the MIP skin thickness is 20–200nm and the residual amount of unreacted 4-vinylpyridine on a dry basis is ≤0.02wt% to be considered qualified.

[0034] Furthermore, the silica carrier is silica fiber.

[0035] Furthermore, the composite coating comprises at least two layers along the thickness direction, and the mass fraction difference between adjacent layers of Zr-MOF@COF@MIP composite particles is 5–40 wt%, wherein the mass fraction of each layer is based on the total mass of the dynamic organosilicon network matrix and the Zr-MOF@COF@MIP composite particles in that layer; the total thickness of the composite coating is 5–200 µm; and the molar percentage of silane in the dynamic organosilicon network matrix of bis[3-(triethoxysilane)propyl]disulfide is 5–30 mol.

[0036] As a concept of this invention, the present invention employs a design in which Zr-MOF@COF@MIP core-shell-skin structure composite particles are uniformly dispersed in a dynamic organosilicon network matrix containing disulfide bonds and immobilized on the surface of a silica support to form a composite coating. This design is primarily used to enhance the molecular recognition selectivity, enrichment sensitivity, coating mechanical durability, and long-term signal baseline stability of the online analysis material for chlorobenzene impurities. In this invention, zirconium-based metal-organic framework nanocrystals, with their high specific surface area and regularly tunable pores, provide porous pre-enrichment sites for chlorobenzene molecules. The covalent organic framework shell continuously and uniformly coats the surface of the Zr-MOF nanocrystals with an ordered and regular pore structure, while simultaneously providing a stable interface substrate rich in amino and imine active groups for the in-situ growth of the outer molecularly imprinted polymer, further enhancing the overall selectivity of the system for chlorobenzene molecules through spatial sieving effects. The molecularly imprinted polymer skin layer uses chlorobenzene as a template, utilizing hydrogen bonding and π-π stacking interactions with 4-vinylpyridine to precisely shape a core-shell-skin structure similar to chlorobenzene. The highly complementary recognition cavity of chlorobenzene molecular spatial structure and chemical environment endows the material with a high specificity for recognizing and enriching chlorobenzene. The dynamic organosilicon network matrix containing disulfide bonds maintains low initial viscosity and good flow film-forming properties even under high particle loading conditions. After curing, it forms a dense cross-linked network that enables the composite particles to be uniformly and densely anchored and form a strong interfacial bond with the silica carrier. Moreover, its reversible disulfide bonds can achieve coating self-repair through SS bond exchange reaction when mechanical micro-damage occurs, effectively maintaining the long-term stability of the analytical signal baseline. The synergistic effect of each component systematically improves the overall analytical performance of the material.

[0037] This invention also discloses a method for preparing an online analytical material for chlorobenzene impurities as described above, comprising the following steps:

[0038] S1. Provides dynamic organosilicon sol intermediates;

[0039] S2. Prepare Cl / N co-modified Zr-MOF nanocrystals as the core of the Zr-MOF@COF@MIP composite particles;

[0040] S3. Using the Cl / N co-modified Zr-MOF nanocrystals as the core, prepare and provide a Zr-MOF@COF core-shell intermediate;

[0041] S4. Using the Zr-MOF@COF core-shell intermediate as a precursor, prepare and obtain Zr-MOF@COF@MIP composite particles;

[0042] S5. Add Zr-MOF@COF@MIP composite particles to dynamic organosilicon sol intermediate and mix to obtain a coating solution. The mass fraction of Zr-MOF@COF@MIP composite particles in the coating solution is 10–70 wt%, and the mass fraction is calculated as the total mass of the solids of dynamic organosilicon sol intermediate and the Zr-MOF@COF@MIP composite particles in the coating solution.

[0043] S6. The coating liquid is fixed onto the surface of the silica carrier and cured to form a composite coating, thus obtaining a material for online analysis of chlorobenzene impurities.

[0044] Furthermore, the mixing in step S5 is carried out under nitrogen protection; step S6 includes at least two loading and curing cycles, and the mass fraction difference of Zr-MOF@COF@MIP composite particles in the coating liquid used in adjacent cycles is 5–40 wt% to form a thickness gradient.

[0045] Step S6 is completed by at least one of dip coating, spray coating or casting; the curing conditions of step S6 are 40–140℃, 0.5–24h; after the composite coating is cured, it is vacuum treated at 40–140℃ and vacuum degree not higher than 10kPa for 0.5–24h to make the total amount of residual solvent ≤1.0wt%. The total amount of residual solvent is determined by headspace gas chromatography, and the dry basis mass of the cured composite coating is used as the calculation basis.

[0046] Furthermore, in the preparation of Cl / N co-modified Zr-MOF nanocrystals in step S2, the molar ratio of glacial acetic acid to zirconium tetrachloride is 10–200:1; in the preparation of the Zr-MOF@COF core-shell intermediate in step S3, the volume ratio of N,N-dimethylformamide to deionized water is 95:5 to 60:40; in the preparation of the Zr-MOF@COF@MIP composite particles in step S4, the amount of 2,2'-azobisisobutyronitrile added is 0.1–2.0 wt% of the total mass of 4-vinylpyridine and ethylene glycol dimethacrylate.

[0047] Furthermore, in step B3, the volume ratio of N,N-dimethylformamide to deionized water is 95:5 to 60:40.

[0048] Further, in step A3, the acidic aqueous solution is added dropwise to the silane mixture under magnetic stirring at a speed of 200–1000 rpm; after adding anhydrous ethanol, stirring is continued at the same speed until the endpoint described in step A4 is reached.

[0049] Furthermore, in step A4, the solid content is determined by the weighing and drying method: about 1.000g of sol is placed in a weighing bottle that has been constant in weight, and dried at 105℃ until the difference between two consecutive weighings does not exceed 0.002g. The solid content is calculated as the percentage of the mass of the dried solid to the mass of the sampled sol. The criterion for no visible precipitate is that no visible particles settle after standing at 25℃ for 30min.

[0050] Further, in step D3, after adding chlorobenzene to the dispersion system obtained in D2, the system is allowed to stand at 25°C for 30 minutes to confirm that there are no visible oil droplets and no layering. If visible oil droplets or layering occurs, the system is treated with ultrasonic power of 100–500W for 5–30 minutes before adding 4-vinylpyridine and ethylene glycol dimethacrylate to restore the system to a stable dispersion state. The criterion for a stable dispersion state is that there is no visible layering after standing at 25°C for 30 minutes.

[0051] Further, in step S5, after adding the Zr-MOF@COF@MIP composite particles to the dynamic organosilicon sol intermediate, the mixture is ultrasonically treated with an ultrasonic power of 100–500W for 10–60 min under nitrogen protection, or stirred with a mechanical stirring speed of 300–800 rpm for 0.5–2 h, until no visible particle agglomerates are found in the coating solution.

[0052] Furthermore, in the composite coating, the mass fraction of Zr-MOF@COF@MIP composite particles in each layer monotonically increases or monotonically decreases sequentially from the inner layer closest to the silica carrier to the outer layer furthest from the silica carrier.

[0053] Furthermore, the determination of chlorobenzene residue in step D4 and 4-vinylpyridine residue in step D5 were both performed by gas chromatography, with the dry basis mass of the tested particles as the calculation basis.

[0054] Furthermore, pH measurements in each step were performed using glass pH electrodes calibrated at 25°C with standard buffer solutions of pH 4.00 and pH 7.00.

[0055] As another aspect of this invention, a preparation process combining stepwise synthesis and gradient multiple-stage solidification is employed. This process primarily enhances the structural controllability of each functional level in the online analysis material for chlorobenzene impurities, the overall uniformity of the coating, and the integrity and reproducibility of the gradient composite structure. In this invention, dynamic organosilicon sol intermediates, Cl / N co-modified Zr-MOF nanocrystals, Zr-MOF@COF core-shell intermediates, and Zr-MOF@COF@MIP composite particles are synthesized sequentially and subjected to strict quality control through steps S1 to S4. Each step includes quantifiable process quality control endpoint criteria (solid content, absence of visible precipitate, particle size, pH, shell thickness, coating rate, and template residue), effectively ensuring batch stability of the structure and performance of each intermediate. Step S5, under nitrogen protection, achieves uniform mixing of the particles and sol intermediates through ultrasonic or mechanical stirring, eliminating agglomerates to ensure coating stability. Coating quality; Step S6 involves performing at least two immobilization-curing cycles on the silica support and precisely controlling the mass fraction difference of Zr-MOF@COF@MIP composite particles in adjacent cycles of coating solution to be 5–40 wt%, forming a particle density gradient distribution along the coating thickness direction. The particle concentration is lower near the support interface to ensure high interfacial bonding strength, while the outer layer particle concentration is higher away from the support to maximize the density of analytical functional sites. After curing, vacuum post-treatment is performed to reduce the residual solvent to ≤1.0 wt%, ensuring stable signal baseline. The overall preparation process is highly controllable and reproducible, and has good potential for large-scale production.

[0056] The Zr-MOF@COF@MIP composite particles serve as the core of the molecular recognition function in this invention. Their three-layer core-shell-skin architecture endows the material with multi-level synergistic enrichment and selective recognition capabilities for chlorobenzene. The zirconium-based metal-organic framework nanocrystal core achieves preferential adsorption and pre-concentration of chlorobenzene molecules through abundant coordination open metal sites and microporous structure. The inherent chemical inertness of its Zr-O framework to acidic media and organic solvents also provides a basic guarantee for the durability of the overall functional unit. The covalent organic framework shell forms a regular hexagonal pore network connected by imine bonds, continuously coating the surface of Zr-MOF nanocrystals. On the one hand, it suppresses the competitive adsorption of interfering substances through the spatial sieving effect of pore size and polarity. On the other hand, it provides abundant surface anchoring points for the uniform in-situ growth of the subsequent molecularly imprinted polymer skin. The molecularly imprinted polymer skin precisely constructs complementary cavities using hydrogen bonds between 4-vinylpyridine and chlorobenzene and π-π stacked pre-organized complexes as recognition templates to achieve specific recognition of chlorobenzene. A dynamic organosilicon network matrix containing disulfide bonds serves as the functional carrier matrix of this invention. The reversible covalent disulfide bonds introduced by bis[3-(triethoxysilane)propyl]disulfide impart dynamic response characteristics to the matrix within the cross-linked network: after curing, the highly cross-linked network achieves uniform and dense fixation of the composite particles and forms a chemically bonded interface with the silica carrier, significantly improving erosion and wear resistance; while the reversible SS bonds in the network can spontaneously exchange and heal damage under mild conditions under mechanical micro-damage induction, maintaining the integrity of the coating structure and the stability of the signal baseline. When both work synergistically, the uniform dispersion and fixation effect of the dynamic organosilicon matrix ensures that the recognition sites of the Zr-MOF@COF@MIP composite particles are oriented towards the analyte with optimal spatial accessibility, maximizing enrichment capacity; and the stable chemical framework of the recognition particles, in turn, inhibits the accelerated degradation of the matrix under harsh conditions, enabling the recognition sensitivity and durability stability of the composite coating to systematically surpass the levels achieved by using each component individually.

[0057] Beneficial technical effects

[0058] 1. By organically integrating zirconium-based metal-organic framework nanocrystals with high specific surface area, covalent organic frameworks with regular channels, and molecularly imprinted polymers templated with chlorobenzene into core-shell-skin ternary composite particles, and utilizing the layer-by-layer synergy of pre-enrichment, spatial sieving, and specific recognition at each level, the density of effective recognition sites is greatly improved, thereby achieving highly sensitive and specific detection of trace chlorobenzene and effectively reducing the detection limit of online analysis.

[0059] 2. A three-dimensional network anchoring of nanoscale Zr-MOF@COF@MIP composite particles is achieved through a dynamic organosilicon network matrix containing disulfide bonds. This not only forms a highly cross-linked protective layer that is firmly bonded to the silica carrier after curing, giving the coating excellent resistance to fluid erosion and wear, but also maintains a short mass transfer and diffusion path due to the nanoscale particle size of the composite particles. The two work together to ensure the mechanical stability of the coating under continuous online conditions and its rapid response to chlorobenzene molecules.

[0060] 3. The reversible disulfide bonds introduced by the bis[3-(triethoxysilane)propyl]disulfide in the dynamic organosilicon network matrix can spontaneously undergo SS bond exchange reactions under mild conditions to achieve self-repair when the coating is subjected to micro-damage, effectively extending the service life of the coating; at the same time, the inherent chemical inertness of the zirconium-based metal-organic framework core to acidic media, organic solvents and thermal-vacuum conditions ensures the long-term stability of the functional units, thereby ensuring the stability and repeatability of the signal baseline in continuous online analysis.

[0061] 4. By implementing multiple immobilization-curing cycles on the silica carrier and precisely controlling the gradient change of the mass fraction of Zr-MOF@COF@MIP composite particles in each coating solution, a gradient coordinated distribution of low particle concentration and high interfacial bonding strength near the carrier side and high particle concentration and high recognition site density far from the carrier side is achieved, maximizing the effective analytical capacity per unit area without sacrificing the overall adhesion of the coating.

[0062] 5. Each synthesis step has a quantifiable process endpoint criterion to ensure that the performance of each intermediate and the final product is consistent across batches; the core raw materials used, such as tetraethyl orthosilicate, zirconium tetrachloride, and organic ligands, are all commercially available, the synthesis route is clear, and it is suitable for large-scale production and application. Attached Figure Description

[0063] Figure 1 This is a superimposed FTIR infrared spectrum of Example 1 and Comparative Example 1;

[0064] Figure 2 XRD crystal structure overlays of Example 1, Comparative Example 1, and Comparative Example 2;

[0065] Figure 3 XPS S 2p high-resolution overlays of Example 1, Comparative Example 3, and Comparative Example 4;

[0066] Figure 4 This is a magnified overlay of the FTIR low wavenumber region of Example 1 and Comparative Example 3;

[0067] Figure 5 Here is a macroscopic optical photograph of the material used in the online analysis of chlorobenzene impurities in Example 1;

[0068] Figure 6This is a scanning electron microscope (SEM) image of the material used for online analysis of chlorobenzene impurities in Example 1. Detailed Implementation

[0069] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0070] Example 1

[0071] This embodiment provides an online analysis material for chlorobenzene impurities, comprising a silica carrier and a composite coating immobilized on the surface of the silica carrier in this embodiment; the composite coating in this embodiment comprises a dynamic organosilicon network matrix and composite particles dispersed in the dynamic organosilicon network matrix in this embodiment.

[0072] The composite particles in this embodiment are Zr-MOF@COF@MIP composite particles. The Zr-MOF@COF@MIP composite particles in this embodiment are core-shell-skin structure composite particles with Zr-MOF nanocrystals as the core, covalent organic framework COF as the coating shell, and molecularly imprinted polymer MIP as the outermost skin layer. Zr-MOF is a zirconium-based metal-organic framework, COF is a covalent organic framework, and MIP is a molecularly imprinted polymer.

[0073] In this embodiment, the Zr-MOF@COF@MIP composite particles are arranged in layers along the thickness direction, with the inner layer closer to the silica carrier having a mass fraction of 25 wt% and the outer layer farther from the silica carrier having a mass fraction of 50 wt%. The mass fraction of each layer is based on the total mass of the dynamic organosilicon network matrix and the Zr-MOF@COF@MIP composite particles in that layer. The dynamic organosilicon network matrix in this embodiment is obtained by curing a dynamic organosilicon sol intermediate, and the dynamic organosilicon network matrix in this embodiment contains a disulfide bond structure introduced by bis[3-(triethoxysilyl)propyl] disulfide. The median particle size of the Zr-MOF@COF@MIP composite particles in this embodiment is 275 nm, and the MIP skin thickness of the Zr-MOF@COF@MIP composite particles in this embodiment is 100 nm.

[0074] The dynamic organosilicon sol intermediate in this embodiment is prepared through the following steps:

[0075] A1. Raw materials: tetraethyl orthosilicate, methyltrimethoxysilane, bis[3-(triethoxysilane)propyl] disulfide, 3-aminopropyltriethoxysilane, hydrochloric acid, anhydrous ethanol, deionized water.

[0076] A2. Proportioning: Based on the total molar number of tetraethyl orthosilicate, methyltrimethoxysilane, bis[3-(triethoxysilane)propyl]disulfide, and 3-aminopropyltriethoxysilane, tetraethyl orthosilicate accounts for 50 mol%, methyltrimethoxysilane accounts for 25 mol%, bis[3-(triethoxysilane)propyl]disulfide accounts for 18 mol%, and 3-aminopropyltriethoxysilane accounts for 7 mol%, and the sum of the molar percentages of the above four components is 100 mol%. The molar ratio of the total molar number to deionized water in this embodiment is 1:4.

[0077] A3. Hydrolysis and condensation: The silanes described in A2 are mixed according to the specified ratio to obtain a silane mixture; hydrochloric acid is added to deionized water to prepare an acidic aqueous solution and the pH is controlled at 2.5 at 25°C. The acidic aqueous solution of this embodiment is added dropwise to the silane mixture of this embodiment at 25°C and carried out under magnetic stirring at a stirring speed of 600 rpm for 1.5 h. Then anhydrous ethanol is added and stirring is continued at the same speed until the endpoint described in step A4 is reached, and the reaction is continued for 6 h. The amount of anhydrous ethanol added in this embodiment is based on the solid content of the sol in step A4 being 15 wt%.

[0078] A4. Endpoint Criterion: The reaction is terminated when the solid content of the sol is 15wt% and no visible precipitate is found. In this embodiment, the solid content is determined by the weighing and drying method: about 1.000g of sol is placed in a weighing bottle that has been constant-weighted and dried at 105℃ until the difference between two consecutive weighings does not exceed 0.002g. The solid content is calculated as the percentage of the mass of the dried solid to the mass of the sampled sol. The criterion for no visible precipitate is that no visible particles settle after standing at 25℃ for 30min.

[0079] A5. Post-processing and quality control: Dynamic organosilicon sol intermediates were obtained by filtration. The pore size of the filter membrane used for filtration was 0.45µm. The dynamic organosilicon sol intermediates were considered qualified if they did not gel after standing for 400 hours under sealed conditions.

[0080] The Cl / N co-modified Zr-MOF nanocrystals in the Zr-MOF@COF@MIP composite particles of this embodiment were prepared through the following steps, wherein Cl is chlorine and N is nitrogen:

[0081] B1. Raw materials: zirconium tetrachloride, 2-aminoterephthalic acid, 2-chloroterephthalic acid, N,N-dimethylformamide, glacial acetic acid, deionized water, nitrogen.

[0082] B2. Ratio: The ligands are 2-aminoterephthalic acid and 2-chloroterephthalic acid; based on the total molar number of ligands, 2-aminoterephthalic acid accounts for 40 mol%, 2-chloroterephthalic acid accounts for 60 mol%, and the sum of the molar percentages of the two is 100 mol%; the total molar ratio of zirconium tetrachloride to the ligands is 1:1.2.

[0083] B3. Solvothermal reaction: Under nitrogen protection, zirconium tetrachloride, the ligand of this embodiment, N,N-dimethylformamide, deionized water and glacial acetic acid were mixed. The molar ratio of glacial acetic acid to zirconium tetrachloride was 100:1, and the volume ratio of N,N-dimethylformamide to deionized water was 80:20. After sealing, the reaction was carried out at 105 °C for 12 h.

[0084] B4. Endpoint criterion: After the reaction, it was cooled to room temperature and centrifuged. The relative centrifugal force for centrifugation was 10000×g, the centrifugation time was 15 min, and the centrifugation temperature was 25 °C. It was washed alternately with N,N-dimethylformamide and absolute ethanol 5 times. The volume ratio of N,N-dimethylformamide or absolute ethanol used for each washing to the mass of the solid to be washed was 50 mL:1 g until the pH measured at 25 °C after mixing the supernatant of the last washing with deionized water at a volume ratio of 1:1 was within the range of 5.5 to 7.5.

[0085] B5. Post-treatment and quality control: Vacuum drying was carried out at 110 °C and a vacuum degree not higher than 10 kPa for 12 h to obtain Cl / N co-modified Zr-MOF nanocrystals; the median particle size of the Cl / N co-modified Zr-MOF nanocrystals being 150 nm was qualified.

[0086] The Zr-MOF@COF core-shell intermediate of this embodiment was prepared by the following steps:

[0087] C1. Raw materials: Cl / N co-modified Zr-MOF nanocrystals, 2,4,6-triformylphloroglucinol, p-phenylenediamine, glacial acetic acid, N,N-dimethylformamide, deionized water, nitrogen.

[0088] C2. Ratio: The molar ratio of 2,4,6-triformylphloroglucinol to p-phenylenediamine was 1:1.5; based on the mass of the Cl / N co-modified Zr-MOF nanocrystals, the total mass of 2,4,6-triformylphloroglucinol and p-phenylenediamine was 1.0 times the mass of the Cl / N co-modified Zr-MOF nanocrystals.

[0089] C3. In-situ growth: Under nitrogen protection, the Cl / N co-modified Zr-MOF nanocrystals were dispersed in a mixed solvent of N,N-dimethylformamide and deionized water. The volume ratio of N,N-dimethylformamide to deionized water in this embodiment was 75:25. Glacial acetic acid was added and the pH of the system was controlled at 4.5 at 25 °C. Subsequently, 2,4,6-triformylphloroglucinol and p-phenylenediamine were added. After sealing, the reaction was carried out at 90 °C for 12 h.

[0090] C4. Endpoint Criteria: After the reaction, centrifuge at a relative centrifugal force of 10000×g for 15 min at a temperature of 25℃. Wash with anhydrous ethanol 6 times, with a volume ratio of 50 mL to 1 g of anhydrous ethanol used for each wash, until the pH of the final wash solution mixed with deionized water at a volume ratio of 1:1 is within the range of 5.5 to 7.5 at 25℃.

[0091] C5. Post-processing and quality control: Zr-MOF@COF core-shell intermediates were obtained by vacuum drying at 90℃ and a vacuum degree not exceeding 10kPa for 12h; the covalent organic framework shell thickness was 25nm and the shell continuity rate was 85% to be considered qualified.

[0092] The Zr-MOF@COF@MIP composite particles in this embodiment were prepared by the following steps:

[0093] D1. Raw materials: Zr-MOF@COF core-shell intermediate, 3-(methacryloyloxy)propyltrimethoxysilane, chlorobenzene, 4-vinylpyridine, ethylene glycol dimethacrylate, 2,2'-azobisisobutyronitrile, anhydrous ethanol, deionized water, methanol, glacial acetic acid, nitrogen.

[0094] D2. Introduction of surface initiation sites: The Zr-MOF@COF core-shell intermediate was dispersed in a mixed solvent of anhydrous ethanol and deionized water. In this embodiment, the volume ratio of anhydrous ethanol to deionized water was 70:30. 3-(methacryloyloxy)propyltrimethoxysilane was added. In this embodiment, the amount of 3-(methacryloyloxy)propyltrimethoxysilane added was 12 wt% of the mass of the Zr-MOF@COF core-shell intermediate. The pH was controlled at 4.5 at 25°C, and the reaction was carried out at 40°C for 4 h.

[0095] D3. Surface molecular imprinting polymerization: Under nitrogen protection, chlorobenzene, 4-vinylpyridine, ethylene glycol dimethacrylate, and 2,2'-azobisisobutyronitrile were added to the system obtained in D2. The molar ratio of chlorobenzene to 4-vinylpyridine was 1:3.0, and the molar ratio of 4-vinylpyridine to ethylene glycol dimethacrylate was 1:10.0. The amount of 2,2'-azobisisobutyronitrile added was 1.0 wt% of the total mass of 4-vinylpyridine and ethylene glycol dimethacrylate. After adding chlorobenzene to the dispersion system obtained in D2, the system was allowed to stand at 25°C for 30 min to confirm that there were no visible oil droplets and no stratification. The system was then polymerized at 65°C and 600 rpm under sealed conditions for 6 h to obtain a template-containing molecularly imprinted skin.

[0096] D4. Template Removal: Wash 10 times with an eluent of methanol and glacial acetic acid in a gradient manner. In this embodiment, the gradient method is as follows: first wash with an eluent of methanol and glacial acetic acid at a volume ratio of 7:3, then wash with an eluent at a volume ratio of 9:1, and finally wash with pure methanol. The volume ratio of the eluent used in each washing step to the mass ratio of the Zr-MOF@COF@MIP composite particles is 100mL:1g, until the residual amount of chlorobenzene in the Zr-MOF@COF@MIP composite particles is ≤0.05wt% on a dry basis. In this embodiment, the residual amount of chlorobenzene is determined by gas chromatography, with the dry basis mass of the tested particles as the calculation basis.

[0097] D5. Post-processing and quality control: Zr-MOF@COF@MIP composite particles were obtained by vacuum drying at 80℃ and a vacuum degree not exceeding 10kPa for 12h; the MIP skin thickness was 100nm and the residual amount of unreacted 4-vinylpyridine on a dry basis was ≤0.02wt% to be considered qualified; in this embodiment, the residual amount of 4-vinylpyridine was determined by gas chromatography, with the dry basis of the tested particles as the calculation basis.

[0098] In this embodiment, the silica carrier is silica fiber.

[0099] The composite coating of this embodiment comprises two layers along the thickness direction, and the mass fraction difference of Zr-MOF@COF@MIP composite particles in adjacent layers is 25wt%. The mass fraction of each layer in this embodiment is based on the total mass of the dynamic organosilicon network matrix and Zr-MOF@COF@MIP composite particles in that layer. The total thickness of the composite coating is 80µm. The molar percentage of silane bis[3-(triethoxysilane)propyl]disulfide in the dynamic organosilicon network matrix is ​​18mol%. In this embodiment, the mass fraction of Zr-MOF@COF@MIP composite particles in each layer monotonically increases from the inner layer closer to the silica support to the outer layer farther from the silica support.

[0100] The preparation method of the chlorobenzene impurity online analysis material in this embodiment includes the following steps:

[0101] S1. Provides dynamic organosilicon sol intermediates.

[0102] S2. Prepare Cl / N co-modified Zr-MOF nanocrystals as the core of the Zr-MOF@COF@MIP composite particles;

[0103] S3. Using the Cl / N co-modified Zr-MOF nanocrystals as the core, prepare and provide a Zr-MOF@COF core-shell intermediate;

[0104] S4. Using the Zr-MOF@COF core-shell intermediate as a precursor, prepare and obtain Zr-MOF@COF@MIP composite particles;

[0105] S5. Zr-MOF@COF@MIP composite particles are added to the dynamic organosilicon sol intermediate and mixed under nitrogen protection to obtain a coating solution. Coating solutions for two immobilization and curing cycles are prepared separately. The mass fraction of Zr-MOF@COF@MIP composite particles in the coating solution used in the first cycle is 25 wt%, and the mass fraction of Zr-MOF@COF@MIP composite particles in the coating solution used in the second cycle is 50 wt%. In this embodiment, the mass fraction is calculated based on the total mass of the solids of the dynamic organosilicon sol intermediate and the Zr-MOF@COF@MIP composite particles in the coating solution. After adding Zr-MOF@COF@MIP composite particles to the dynamic organosilicon sol intermediate, ultrasonic treatment is performed at an ultrasonic power of 300W for 30 minutes under nitrogen protection until no visible particle agglomerates are found in the coating solution.

[0106] S6. The coating solution is immobilized onto the surface of a silica carrier and cured to form a composite coating, thereby obtaining a material for online analysis of chlorobenzene impurities. Step S6 in this embodiment includes two immobilization and curing cycles, and the mass fraction difference of Zr-MOF@COF@MIP composite particles in the coating solution used in adjacent cycles is 25wt% to form a thickness gradient. The mass fraction of Zr-MOF@COF@MIP composite particles in the coating solution used in the first cycle is 25wt%, and the mass fraction of Zr-MOF@COF@MIP composite particles in the coating solution used in the second cycle is 50wt%. Step S6 in this embodiment uses an immersion coating method to complete the immobilization. The curing conditions for step S6 in this embodiment are 90℃ and 8h. After the composite coating is cured, it is vacuum treated at 90℃ and a vacuum degree not exceeding 10kPa for 8h to ensure that the total amount of residual solvent is ≤1.0wt%. The total amount of residual solvent in this embodiment is determined by headspace gas chromatography, and the dry basis mass of the cured composite coating is used as the calculation basis.

[0107] In this embodiment, pH measurements were performed using a glass pH electrode calibrated at 25°C with standard buffer solutions of pH 4.00 and pH 7.00.

[0108] Features of Example 1: This example uses moderate parameter configuration. The mass fraction of Zr-MOF@COF@MIP composite particles is 25wt% for the inner layer, 50wt% for the outer layer, with a median particle size of 275nm and a MIP skin thickness of 100nm. The dynamic organosilicon network matrix contains 18mol% bis[3-(triethoxysilane)propyl]disulfide. The molar ratio of 2-aminoterephthalic acid to 2-chloroterephthalic acid in the Cl / N co-modified Zr-MOF nanocrystals is 40:60. The COF shell thickness is 25nm, and the total thickness of the composite coating is 80µm. The process parameters are moderate temperature and reaction time, which is suitable for stable online detection of chlorobenzene and its homologues. It has good process reproducibility and long-term stability, and is particularly suitable for continuously operating industrial online analysis systems.

[0109] Example 2

[0110] This embodiment provides an online analysis material for chlorobenzene impurities, comprising a silica carrier and a composite coating immobilized on the surface of the silica carrier in this embodiment; the composite coating in this embodiment comprises a dynamic organosilicon network matrix and composite particles dispersed in the dynamic organosilicon network matrix in this embodiment.

[0111] The composite particles in this embodiment are Zr-MOF@COF@MIP composite particles. The Zr-MOF@COF@MIP composite particles in this embodiment are core-shell-skin structure composite particles with Zr-MOF nanocrystals as the core, covalent organic framework COF as the coating shell, and molecularly imprinted polymer MIP as the outermost skin layer. Zr-MOF is a zirconium-based metal-organic framework, COF is a covalent organic framework, and MIP is a molecularly imprinted polymer.

[0112] In this embodiment, the Zr-MOF@COF@MIP composite particles are arranged in layers along the thickness direction, with the inner layer closer to the silica carrier having a mass fraction of 18 wt% and the outer layer farther from the silica carrier having a mass fraction of 32 wt%. The mass fraction of each layer is based on the total mass of the dynamic organosilicon network matrix and the Zr-MOF@COF@MIP composite particles in that layer. The dynamic organosilicon network matrix in this embodiment is obtained by curing a dynamic organosilicon sol intermediate, and the dynamic organosilicon network matrix in this embodiment contains a disulfide bond structure introduced by bis[3-(triethoxysilyl)propyl] disulfide. The median particle size of the Zr-MOF@COF@MIP composite particles in this embodiment is 180 nm, and the MIP skin thickness of the Zr-MOF@COF@MIP composite particles in this embodiment is 65 nm.

[0113] The dynamic organosilicon sol intermediate in this embodiment is prepared through the following steps:

[0114] A1. Raw materials: tetraethyl orthosilicate, methyltrimethoxysilane, bis[3-(triethoxysilane)propyl] disulfide, 3-aminopropyltriethoxysilane, hydrochloric acid, anhydrous ethanol, deionized water.

[0115] A2. Proportioning: Based on the total molar number of tetraethyl orthosilicate, methyltrimethoxysilane, bis[3-(triethoxysilane)propyl]disulfide, and 3-aminopropyltriethoxysilane, tetraethyl orthosilicate accounts for 45 mol%, methyltrimethoxysilane accounts for 30 mol%, bis[3-(triethoxysilane)propyl]disulfide accounts for 15 mol%, and 3-aminopropyltriethoxysilane accounts for 10 mol%, and the sum of the molar percentages of the above four components is 100 mol%. The molar ratio of the total molar number to deionized water in this embodiment is 1:3.

[0116] A3. Hydrolysis and condensation: The silanes described in A2 are mixed according to the specified ratio to obtain a silane mixture; hydrochloric acid is added to deionized water to prepare an acidic aqueous solution and the pH is controlled at 2.0 at 25°C. The acidic aqueous solution of this embodiment is added dropwise to the silane mixture of this embodiment at 20°C and carried out under magnetic stirring at a stirring speed of 400 rpm for 1.0 h. Then anhydrous ethanol is added and stirring is continued at the same speed until the endpoint described in step A4 is reached, and the reaction is continued for 4 h. The amount of anhydrous ethanol added in this embodiment is based on the solid content of the sol in step A4 being 10 wt%.

[0117] A4. Endpoint Criterion: The reaction is terminated when the solid content of the sol is 10 wt% and there is no visible precipitate. In this embodiment, the solid content is determined by the weighing and drying method: about 1.000 g of sol is placed in a weighing bottle that has been constant-weighted and dried at 105°C until the difference between two consecutive weighings does not exceed 0.002 g. The solid content is calculated as the percentage of the mass of the dried solid to the mass of the sampled sol. The criterion for no visible precipitate is that no visible particles settle after standing at 25°C for 30 min.

[0118] A5. Post-processing and quality control: The dynamic organosilicon sol intermediate was obtained by filtration. The pore size of the filter membrane used for filtration was 1.0µm. The dynamic organosilicon sol intermediate was qualified if it did not gel after standing for 300 hours under closed conditions.

[0119] The Cl / N co-modified Zr-MOF nanocrystals in the Zr-MOF@COF@MIP composite particles of this embodiment were prepared through the following steps, wherein Cl is chlorine and N is nitrogen:

[0120] B1. Raw materials: zirconium tetrachloride, 2-aminoterephthalic acid, 2-chloroterephthalic acid, N,N-dimethylformamide, glacial acetic acid, deionized water, nitrogen.

[0121] B2. Ratio: The ligands are 2-aminoterephthalic acid and 2-chloroterephthalic acid; based on the total molar number of ligands, 2-aminoterephthalic acid accounts for 55 mol%, 2-chloroterephthalic acid accounts for 45 mol%, and the sum of the molar percentages of the above two is 100 mol%; the total molar ratio of zirconium tetrachloride to the ligands is 1:1.0.

[0122] B3. Solvent-thermal reaction: Under nitrogen protection, zirconium tetrachloride, the ligand of this embodiment, N,N-dimethylformamide, deionized water and glacial acetic acid were mixed. The molar ratio of glacial acetic acid to zirconium tetrachloride was 60:1, and the volume ratio of N,N-dimethylformamide to deionized water was 85:15. After sealing, the mixture was reacted at 95°C for 10 h.

[0123] B4. Endpoint Criteria: After the reaction is complete, cool to room temperature, centrifuge, with a relative centrifugal force of 8000×g, a centrifugation time of 12min, and a centrifugation temperature of 22℃. Wash four times alternately with N,N-dimethylformamide and anhydrous ethanol. The volume ratio of N,N-dimethylformamide or anhydrous ethanol used in each wash to the mass of the solid to be washed is 35mL:1g. Continue until the pH of the supernatant from the last wash is measured at 25℃ and is within the range of 5.5 to 7.5 after mixing the supernatant from the last wash with deionized water at a volume ratio of 1:1.

[0124] B5. Post-processing and quality control: Vacuum drying at 100℃ and a vacuum degree not exceeding 10kPa for 10h yields Cl / N co-modified Zr-MOF nanocrystals; the median particle size of Cl / N co-modified Zr-MOF nanocrystals is 120nm to be considered qualified.

[0125] The Zr-MOF@COF core-shell intermediate in this embodiment is prepared through the following steps:

[0126] C1. Raw materials: Cl / N co-modified Zr-MOF nanocrystals, 2,4,6-tricarboxymethyl phloroglucinol, p-phenylenediamine, glacial acetic acid, N,N-dimethylformamide, deionized water, nitrogen.

[0127] C2. Ratio: The molar ratio of 2,4,6-tricarboxymethyl phloroglucinol to p-phenylenediamine is 1:1.3; based on the mass of Cl / N co-modified Zr-MOF nanocrystals, the total mass of 2,4,6-tricarboxymethyl phloroglucinol and p-phenylenediamine is 0.6 times the mass of Cl / N co-modified Zr-MOF nanocrystals.

[0128] C3. In-situ growth: Under nitrogen protection, Cl / N co-modified Zr-MOF nanocrystals were dispersed in a mixed solvent of N,N-dimethylformamide and deionized water. In this example, the volume ratio of N,N-dimethylformamide to deionized water was 85:15. Glacial acetic acid was added and the pH of the system was controlled at 3.8 at 25°C. Then, 2,4,6-tricarboxymethyl phloroglucinol and p-phenylenediamine were added. After sealing, the reaction was carried out at 80°C for 10 h.

[0129] C4. Endpoint Criteria: After the reaction, centrifuge at a relative centrifugal force of 8000×g for 12 min at a temperature of 22℃. Wash with anhydrous ethanol five times, with a volume ratio of 35 mL to 1 g of anhydrous ethanol used for each wash, until the pH of the final wash solution mixed with deionized water at a volume ratio of 1:1 is within the range of 5.5 to 7.5 at 25℃.

[0130] C5. Post-processing and quality control: Zr-MOF@COF core-shell intermediates were obtained by vacuum drying at 80℃ and a vacuum degree not exceeding 10kPa for 10h; the covalent organic framework shell thickness was 18nm and the shell continuity rate was 78% to be considered qualified.

[0131] The Zr-MOF@COF@MIP composite particles in this embodiment were prepared by the following steps:

[0132] D1. Raw materials: Zr-MOF@COF core-shell intermediate, 3-(methacryloyloxy)propyltrimethoxysilane, chlorobenzene, 4-vinylpyridine, ethylene glycol dimethacrylate, 2,2'-azobisisobutyronitrile, anhydrous ethanol, deionized water, methanol, glacial acetic acid, nitrogen.

[0133] D2. Introduction of surface initiation sites: The Zr-MOF@COF core-shell intermediate was dispersed in a mixed solvent of anhydrous ethanol and deionized water. In this embodiment, the volume ratio of anhydrous ethanol to deionized water was 80:20. 3-(methacryloyloxy)propyltrimethoxysilane was added. In this embodiment, the amount of 3-(methacryloyloxy)propyltrimethoxysilane added was 8 wt% of the mass of the Zr-MOF@COF core-shell intermediate. The pH was controlled at 4.0 at 25°C, and the reaction was carried out at 30°C for 3 h.

[0134] D3. Surface molecular imprinting polymerization: Under nitrogen protection, chlorobenzene, 4-vinylpyridine, ethylene glycol dimethacrylate, and 2,2'-azobisisobutyronitrile were added to the system obtained in D2. The molar ratio of chlorobenzene to 4-vinylpyridine was 1:2.0, and the molar ratio of 4-vinylpyridine to ethylene glycol dimethacrylate was 1:6.0. The amount of 2,2'-azobisisobutyronitrile added was 0.5 wt% of the total mass of 4-vinylpyridine and ethylene glycol dimethacrylate. After adding chlorobenzene to the dispersion system obtained in D2, the system was allowed to stand at 25°C for 30 min to confirm that there were no visible oil droplets and no stratification. The system was then polymerized at 60°C and 400 rpm for 5 h under sealed conditions to obtain a template-containing molecularly imprinted skin.

[0135] D4. Template Removal: Wash 8 times with an eluent of methanol and glacial acetic acid in a gradient manner. In this embodiment, the gradient method is as follows: first wash with an eluent of methanol to glacial acetic acid at a volume ratio of 7:3, then wash with an eluent at a volume ratio of 9:1, and finally wash with pure methanol. The volume ratio of the eluent used in each washing step to the mass ratio of the Zr-MOF@COF@MIP composite particles is 60 mL: 1 g, until the residual amount of chlorobenzene in the Zr-MOF@COF@MIP composite particles is ≤0.05 wt% on a dry basis. In this embodiment, the residual amount of chlorobenzene is determined by gas chromatography, with the dry basis mass of the tested particles as the calculation basis.

[0136] D5. Post-processing and quality control: Zr-MOF@COF@MIP composite particles were obtained by vacuum drying at 70℃ and a vacuum degree not exceeding 10kPa for 10h; the MIP skin thickness was 65nm and the residual amount of unreacted 4-vinylpyridine on a dry basis was ≤0.02wt% to be qualified; in this example, the residual amount of 4-vinylpyridine was determined by gas chromatography, with the dry basis of the tested particles as the calculation basis.

[0137] In this embodiment, the silica carrier is silica fiber.

[0138] The composite coating of this embodiment comprises two layers along the thickness direction, and the mass fraction difference of Zr-MOF@COF@MIP composite particles in adjacent layers is 14wt%. The mass fraction of each layer in this embodiment is based on the total mass of the dynamic organosilicon network matrix and Zr-MOF@COF@MIP composite particles in that layer. The total thickness of the composite coating is 50µm. The molar percentage of silane bis[3-(triethoxysilane)propyl]disulfide in the dynamic organosilicon network matrix is ​​15mol%. In this embodiment, the mass fraction of Zr-MOF@COF@MIP composite particles in each layer monotonically increases from the inner layer closer to the silica support to the outer layer farther from the silica support.

[0139] The preparation method of the chlorobenzene impurity online analysis material in this embodiment includes the following steps:

[0140] S1. Provides dynamic organosilicon sol intermediates.

[0141] S2. Prepare Cl / N co-modified Zr-MOF nanocrystals as the core of the Zr-MOF@COF@MIP composite particles;

[0142] S3. Using the Cl / N co-modified Zr-MOF nanocrystals as the core, prepare and provide a Zr-MOF@COF core-shell intermediate;

[0143] S4. Using the Zr-MOF@COF core-shell intermediate as a precursor, prepare and obtain Zr-MOF@COF@MIP composite particles;

[0144] S5. Zr-MOF@COF@MIP composite particles are added to the dynamic organosilicon sol intermediate and mixed under nitrogen protection to obtain a coating solution. Coating solutions for two immobilization and curing cycles are prepared separately. The mass fraction of Zr-MOF@COF@MIP composite particles in the coating solution used in the first cycle is 18 wt%, and the mass fraction of Zr-MOF@COF@MIP composite particles in the coating solution used in the second cycle is 32 wt%. In this embodiment, the mass fraction is calculated based on the total mass of the solids of the dynamic organosilicon sol intermediate and the Zr-MOF@COF@MIP composite particles in the coating solution. After adding Zr-MOF@COF@MIP composite particles to the dynamic organosilicon sol intermediate, ultrasonic treatment is performed at an ultrasonic power of 200W for 20 minutes under nitrogen protection until no visible particle agglomerates are found in the coating solution.

[0145] S6. The coating solution is immobilized onto the surface of a silica carrier and cured to form a composite coating, thereby obtaining a material for online analysis of chlorobenzene impurities. Step S6 in this embodiment includes two immobilization and curing cycles, and the mass fraction difference of Zr-MOF@COF@MIP composite particles in the coating solution used in adjacent cycles is 14wt% to form a thickness gradient. The mass fraction of Zr-MOF@COF@MIP composite particles in the coating solution used in the first cycle is 18wt%, and the mass fraction of Zr-MOF@COF@MIP composite particles in the coating solution used in the second cycle is 32wt%. Step S6 in this embodiment is completed by spraying. The curing conditions of step S6 in this embodiment are 70℃ and 6h. After the composite coating is cured, it is vacuum treated at 70℃ and a vacuum degree not exceeding 10kPa for 6h to ensure that the total amount of residual solvent is ≤1.0wt%. The total amount of residual solvent in this embodiment is determined by headspace gas chromatography, and the dry basis mass of the cured composite coating is used as the calculation basis.

[0146] In this embodiment, pH measurements were performed using a glass pH electrode calibrated at 25°C with standard buffer solutions of pH 4.00 and pH 7.00.

[0147] Features of Example 2: This example uses a low mass fraction of composite particles. The mass fraction of the Zr-MOF@COF@MIP composite particles is 18wt% for the inner layer, 32wt% for the outer layer, with a median particle size of 180nm and a MIP skin thickness of 65nm. In the dynamic organosilicon network matrix, bis[3-(triethoxysilyl)propyl]disulfide accounts for 15mol% and the proportion of methyltrimethoxysilane is increased to 30mol% to enhance hydrophobicity. In the Cl / N co-modified Zr-MOF nanocrystals, the proportion of 2-aminoterephthalic acid is increased to 55mol% to enhance amino functionality. The COF shell thickness is 18nm, and the total thickness of the composite coating is 50µm. A lower reaction temperature and a shorter reaction time are used, which is suitable for high-sensitivity detection of low-concentration chlorobenzene impurities, and is particularly suitable for online monitoring of trace chlorobenzene impurities in the production of fine chemical and pharmaceutical intermediates.

[0148] Example 3

[0149] This embodiment provides an online analysis material for chlorobenzene impurities, comprising a silica carrier and a composite coating immobilized on the surface of the silica carrier in this embodiment; the composite coating in this embodiment comprises a dynamic organosilicon network matrix and composite particles dispersed in the dynamic organosilicon network matrix in this embodiment.

[0150] The composite particles in this embodiment are Zr-MOF@COF@MIP composite particles. The Zr-MOF@COF@MIP composite particles in this embodiment are core-shell-skin structure composite particles with Zr-MOF nanocrystals as the core, covalent organic framework COF as the coating shell, and molecularly imprinted polymer MIP as the outermost skin layer. Zr-MOF is a zirconium-based metal-organic framework, COF is a covalent organic framework, and MIP is a molecularly imprinted polymer.

[0151] In this embodiment, the Zr-MOF@COF@MIP composite particles are arranged in layers along the thickness direction, with the three layers being 30wt%, 50wt%, and 65wt%, respectively. The mass fraction of each layer is based on the total mass of the dynamic organosilicon network matrix and the Zr-MOF@COF@MIP composite particles in that layer. The dynamic organosilicon network matrix in this embodiment is obtained by curing a dynamic organosilicon sol intermediate, and the dynamic organosilicon network matrix in this embodiment contains a disulfide bond structure introduced by bis[3-(triethoxysilyl)propyl] disulfide. The median particle size of the Zr-MOF@COF@MIP composite particles in this embodiment is 380nm, and the MIP skin thickness of the Zr-MOF@COF@MIP composite particles in this embodiment is 140nm.

[0152] The dynamic organosilicon sol intermediate in this embodiment is prepared through the following steps:

[0153] A1. Raw materials: tetraethyl orthosilicate, methyltrimethoxysilane, bis[3-(triethoxysilane)propyl] disulfide, 3-aminopropyltriethoxysilane, hydrochloric acid, anhydrous ethanol, deionized water.

[0154] A2. Proportioning: Based on the total molar number of tetraethyl orthosilicate, methyltrimethoxysilane, bis[3-(triethoxysilane)propyl]disulfide, and 3-aminopropyltriethoxysilane, tetraethyl orthosilicate accounts for 60 mol%, methyltrimethoxysilane accounts for 15 mol%, bis[3-(triethoxysilane)propyl]disulfide accounts for 22 mol%, and 3-aminopropyltriethoxysilane accounts for 3 mol%, and the sum of the molar percentages of the above four components is 100 mol%. The molar ratio of the total molar number to deionized water in this embodiment is 1:5.

[0155] A3. Hydrolysis and condensation: The silanes described in A2 are mixed according to the specified ratio to obtain a silane mixture; hydrochloric acid is added to deionized water to prepare an acidic aqueous solution and the pH is controlled at 3.0 at 25°C. The acidic aqueous solution of this embodiment is added dropwise to the silane mixture of this embodiment at 32°C and carried out under magnetic stirring at a stirring speed of 750 rpm for 2.0 h. Then anhydrous ethanol is added and stirring is continued at the same speed until the endpoint described in step A4 is reached, and the reaction is continued for 9 h. The amount of anhydrous ethanol added in this embodiment is based on the solid content of the sol in step A4 being 22 wt%.

[0156] A4. Endpoint Criterion: The reaction is terminated when the solid content of the sol is 22wt% and there is no visible precipitate. In this embodiment, the solid content is determined by the weighing and drying method: about 1.000g of sol is placed in a weighing bottle that has been constant-weighted and dried at 105℃ until the difference between two consecutive weighings does not exceed 0.002g. The solid content is calculated as the percentage of the mass of the dried solid to the mass of the sampled sol. The criterion for no visible precipitate is that no visible particles settle after standing at 25℃ for 30min.

[0157] A5. Post-processing and quality control: Dynamic organosilicon sol intermediates were obtained by filtration. The pore size of the filter membrane used for filtration was 2.0µm. The dynamic organosilicon sol intermediates were considered qualified if they did not gel after standing for 550 hours under sealed conditions.

[0158] The Cl / N co-modified Zr-MOF nanocrystals in the Zr-MOF@COF@MIP composite particles of this embodiment were prepared through the following steps, wherein Cl is chlorine and N is nitrogen:

[0159] B1. Raw materials: zirconium tetrachloride, 2-aminoterephthalic acid, 2-chloroterephthalic acid, N,N-dimethylformamide, glacial acetic acid, deionized water, nitrogen.

[0160] B2. Ratio: The ligands are 2-aminoterephthalic acid and 2-chloroterephthalic acid; based on the total molar number of ligands, 2-aminoterephthalic acid accounts for 25 mol%, 2-chloroterephthalic acid accounts for 75 mol%, and the sum of the molar percentages of the above two is 100 mol%; the total molar ratio of zirconium tetrachloride to the ligands is 1:1.35.

[0161] B3. Solvent-thermal reaction: Under nitrogen protection, zirconium tetrachloride, the ligand of this embodiment, N,N-dimethylformamide, deionized water and glacial acetic acid were mixed. The molar ratio of glacial acetic acid to zirconium tetrachloride was 140:1, and the volume ratio of N,N-dimethylformamide to deionized water was 68:32. After sealing, the mixture was reacted at 118°C for 16 h.

[0162] B4. Endpoint Criteria: After the reaction was completed, the mixture was cooled to room temperature and centrifuged. The relative centrifugal force was 14000×g, the centrifugation time was 20min, and the centrifugation temperature was 28℃. The mixture was washed 7 times with alternating N,N-dimethylformamide and anhydrous ethanol. The volume ratio of N,N-dimethylformamide or anhydrous ethanol used in each wash to the mass ratio of the solid to be washed was 70mL:1g. This continued until the pH of the supernatant from the last wash was measured at 25℃ and mixed with deionized water at a volume ratio of 1:1, and was within the range of 5.5 to 7.5.

[0163] B5. Post-processing and quality control: Vacuum drying at 125℃ and a vacuum degree not exceeding 10kPa for 16h yields Cl / N co-modified Zr-MOF nanocrystals; the median particle size of Cl / N co-modified Zr-MOF nanocrystals is 220nm to be considered qualified.

[0164] The Zr-MOF@COF core-shell intermediate in this embodiment is prepared through the following steps:

[0165] C1. Raw materials: Cl / N co-modified Zr-MOF nanocrystals, 2,4,6-tricarboxymethyl phloroglucinol, p-phenylenediamine, glacial acetic acid, N,N-dimethylformamide, deionized water, nitrogen.

[0166] C2. Ratio: The molar ratio of 2,4,6-tricarboxymethyl phloroglucinol to p-phenylenediamine is 1:1.7; based on the mass of Cl / N co-modified Zr-MOF nanocrystals, the total mass of 2,4,6-tricarboxymethyl phloroglucinol and p-phenylenediamine is 1.5 times the mass of Cl / N co-modified Zr-MOF nanocrystals.

[0167] C3. In-situ growth: Under nitrogen protection, Cl / N co-modified Zr-MOF nanocrystals were dispersed in a mixed solvent of N,N-dimethylformamide and deionized water. In this example, the volume ratio of N,N-dimethylformamide to deionized water was 65:35. Glacial acetic acid was added and the pH of the system was controlled at 5.2 at 25°C. Then, 2,4,6-tricarboxymethyl phloroglucinol and p-phenylenediamine were added. After sealing, the reaction was carried out at 105°C for 16 h.

[0168] C4. Endpoint Criteria: After the reaction, centrifuge at a relative centrifugal force of 14000×g for 20 min at a temperature of 28℃. Wash with anhydrous ethanol 8 times, with a volume ratio of 70 mL to 1 g of anhydrous ethanol used for each wash, until the pH of the final wash solution mixed with deionized water at a volume ratio of 1:1 is within the range of 5.5 to 7.5 at 25℃.

[0169] C5. Post-processing and quality control: Zr-MOF@COF core-shell intermediates were obtained by vacuum drying at 105℃ and a vacuum degree not exceeding 10kPa for 16h; the covalent organic framework shell thickness was 35nm and the shell continuity rate was 92% to be considered qualified.

[0170] The Zr-MOF@COF@MIP composite particles in this embodiment were prepared by the following steps:

[0171] D1. Raw materials: Zr-MOF@COF core-shell intermediate, 3-(methacryloyloxy)propyltrimethoxysilane, chlorobenzene, 4-vinylpyridine, ethylene glycol dimethacrylate, 2,2'-azobisisobutyronitrile, anhydrous ethanol, deionized water, methanol, glacial acetic acid, nitrogen.

[0172] D2. Introduction of surface initiation sites: The Zr-MOF@COF core-shell intermediate was dispersed in a mixed solvent of anhydrous ethanol and deionized water. In this embodiment, the volume ratio of anhydrous ethanol to deionized water was 58:42. 3-(methacryloyloxy)propyltrimethoxysilane was added. In this embodiment, the amount of 3-(methacryloyloxy)propyltrimethoxysilane added was 20 wt% of the mass of the Zr-MOF@COF core-shell intermediate. The pH was controlled at 5.0 at 25°C, and the reaction was carried out at 52°C for 6 h.

[0173] D3. Surface molecular imprinting polymerization: Under nitrogen protection, chlorobenzene, 4-vinylpyridine, ethylene glycol dimethacrylate, and 2,2'-azobisisobutyronitrile were added to the system obtained in D2. The molar ratio of chlorobenzene to 4-vinylpyridine was 1:4.5, and the molar ratio of 4-vinylpyridine to ethylene glycol dimethacrylate was 1:15.0. The amount of 2,2'-azobisisobutyronitrile added was 1.5 wt% of the total mass of 4-vinylpyridine and ethylene glycol dimethacrylate. After adding chlorobenzene to the dispersion system obtained in D2, the system was allowed to stand at 25°C for 30 min to confirm that there were no visible oil droplets and no stratification. The system was then polymerized at 72°C and 750 rpm for 8 h under sealed conditions to obtain a template-containing molecularly imprinted skin.

[0174] D4. Template Removal: Wash 15 times with an eluent of methanol and glacial acetic acid in a gradient manner. In this embodiment, the gradient method is as follows: first wash with an eluent of methanol and glacial acetic acid at a volume ratio of 7:3, then wash with an eluent at a volume ratio of 9:1, and finally wash with pure methanol. The volume ratio of the eluent used in each washing step to the mass ratio of the Zr-MOF@COF@MIP composite particles is 140 mL: 1 g, until the residual amount of chlorobenzene in the Zr-MOF@COF@MIP composite particles is ≤0.05 wt% on a dry basis. In this embodiment, the residual amount of chlorobenzene is determined by gas chromatography, with the dry basis mass of the tested particles as the calculation basis.

[0175] D5. Post-processing and quality control: Zr-MOF@COF@MIP composite particles were obtained by vacuum drying at 95℃ and a vacuum degree not exceeding 10kPa for 16h; the MIP skin thickness was 140nm and the residual amount of unreacted 4-vinylpyridine on a dry basis was ≤0.02wt% to be considered qualified; in this embodiment, the residual amount of 4-vinylpyridine was determined by gas chromatography, with the dry basis of the tested particles as the calculation basis.

[0176] In this embodiment, the silica carrier is silica fiber.

[0177] The composite coating of this embodiment comprises three layers along its thickness direction, with the mass fraction difference between adjacent layers of Zr-MOF@COF@MIP composite particles being 20wt% and 15wt%, respectively. The mass fraction of each layer in this embodiment is calculated based on the total mass of the dynamic organosilicon network matrix and the Zr-MOF@COF@MIP composite particles in that layer. The total thickness of the composite coating is 135µm. The molar percentage of silane in the dynamic organosilicon network matrix is ​​22mol%. In this embodiment, the mass fraction of Zr-MOF@COF@MIP composite particles in each layer monotonically increases sequentially from the inner layer closest to the silica support to the outer layer furthest from the silica support.

[0178] The preparation method of the chlorobenzene impurity online analysis material in this embodiment includes the following steps:

[0179] S1. Provides dynamic organosilicon sol intermediates.

[0180] S2. Prepare Cl / N co-modified Zr-MOF nanocrystals as the core of the Zr-MOF@COF@MIP composite particles;

[0181] S3. Using the Cl / N co-modified Zr-MOF nanocrystals as the core, prepare and provide a Zr-MOF@COF core-shell intermediate;

[0182] S4. Using the Zr-MOF@COF core-shell intermediate as a precursor, prepare and obtain Zr-MOF@COF@MIP composite particles;

[0183] S5. The Zr-MOF@COF@MIP composite particles are added to the dynamic organosilicon sol intermediate and mixed under nitrogen protection to obtain a coating solution. Coating solutions for three loading and curing cycles are prepared respectively. The mass fraction of Zr-MOF@COF@MIP composite particles in the coating solution used in the first cycle is 30 wt%, the mass fraction of Zr-MOF@COF@MIP composite particles in the coating solution used in the second cycle is 50 wt%, and the mass fraction of Zr-MOF@COF@MIP composite particles in the coating solution used in the third cycle is 65 wt%. In this embodiment, the mass fraction is calculated as the total mass of the solids of the dynamic organosilicon sol intermediate and the Zr-MOF@COF@MIP composite particles in the coating solution.

[0184] S6. The coating solution is immobilized onto the surface of a silica carrier and cured to form a composite coating, thereby obtaining a material for online analysis of chlorobenzene impurities. In this embodiment, step S6 includes three immobilization and curing cycles, with the mass fraction difference between the Zr-MOF@COF@MIP composite particles in the coating solution used in adjacent cycles being 20wt% and 15wt%, respectively, to form a thickness gradient. Specifically, the mass fraction of the Zr-MOF@COF@MIP composite particles in the coating solution used in the first cycle is 30wt%, and the mass fraction in the coating solution used in the second cycle is... The mass fraction of the composite particles is 50 wt%, and the mass fraction of Zr-MOF@COF@MIP composite particles in the coating solution used in the third cycle is 65 wt%. In this embodiment, step S6 is completed by casting. The curing conditions for step S6 in this embodiment are 115℃ and 12h. After the composite coating is cured, it is vacuum treated at 115℃ and a vacuum degree not higher than 10kPa for 12h to ensure that the total amount of residual solvent is ≤1.0 wt%. In this embodiment, the total amount of residual solvent is determined by headspace gas chromatography, and the dry basis mass of the cured composite coating is used as the calculation basis.

[0185] In this embodiment, pH measurements were performed using a glass pH electrode calibrated at 25°C with standard buffer solutions of pH 4.00 and pH 7.00.

[0186] Features of Example 3: This example uses a high mass fraction of composite particles. The mass fractions of the three layers of Zr-MOF@COF@MIP composite particles are 30wt%, 50wt%, and 65wt%, respectively, with a median particle size of 380nm and a MIP skin thickness of 140nm. In the dynamic organosilicon network matrix, bis[3-(triethoxysilyl)propyl]disulfide accounts for 22mol%, and the proportion of tetraethyl orthosilicate is increased to 60mol% to enhance mechanical strength. In the Cl / N co-modified Zr-MOF nanocrystals, the proportion of 2-chloroterephthalic acid is increased to 75mol% to enhance the coordination activity of chlorine. The COF shell thickness is 35nm. The composite coating adopts a three-layer incremental gradient structure with a total thickness of 135µm. A higher reaction temperature and a longer reaction time are used to improve crystallinity and stability. It is suitable for rapid response detection of high-concentration chlorobenzene impurities and simultaneous analysis of polychlorinated benzene isomers in complex matrix samples. It is particularly suitable for online analysis of high-concentration chlorobenzene and its derivatives in the production of pesticide and dye intermediates.

[0187] Example 4

[0188] This embodiment provides an online analysis material for chlorobenzene impurities, comprising a silica carrier and a composite coating immobilized on the surface of the silica carrier in this embodiment; the composite coating in this embodiment comprises a dynamic organosilicon network matrix and composite particles dispersed in the dynamic organosilicon network matrix in this embodiment.

[0189] The composite particles in this embodiment are Zr-MOF@COF@MIP composite particles. The Zr-MOF@COF@MIP composite particles in this embodiment are core-shell-skin structure composite particles with Zr-MOF nanocrystals as the core, covalent organic framework COF as the coating shell, and molecularly imprinted polymer MIP as the outermost skin layer. Zr-MOF is a zirconium-based metal-organic framework, COF is a covalent organic framework, and MIP is a molecularly imprinted polymer.

[0190] In this embodiment, the Zr-MOF@COF@MIP composite particles are arranged in layers along the thickness direction, with the inner layer closer to the silica carrier having a mass fraction of 42 wt% and the outer layer farther from the silica carrier having a mass fraction of 70 wt%. The mass fraction of each layer is based on the total mass of the dynamic organosilicon network matrix and the Zr-MOF@COF@MIP composite particles in that layer. The dynamic organosilicon network matrix in this embodiment is obtained by curing a dynamic organosilicon sol intermediate, and the dynamic organosilicon network matrix in this embodiment contains a disulfide bond structure introduced by bis[3-(triethoxysilyl)propyl] disulfide. The median particle size of the Zr-MOF@COF@MIP composite particles in this embodiment is 460 nm, and the MIP skin thickness of the Zr-MOF@COF@MIP composite particles in this embodiment is 35 nm.

[0191] The dynamic organosilicon sol intermediate in this embodiment is prepared through the following steps:

[0192] A1. Raw materials: tetraethyl orthosilicate, methyltrimethoxysilane, bis[3-(triethoxysilane)propyl] disulfide, 3-aminopropyltriethoxysilane, hydrochloric acid, anhydrous ethanol, deionized water.

[0193] A2. Proportioning: Based on the total molar number of tetraethyl orthosilicate, methyltrimethoxysilane, bis[3-(triethoxysilane)propyl]disulfide, and 3-aminopropyltriethoxysilane, tetraethyl orthosilicate accounts for 35 mol%, methyltrimethoxysilane accounts for 35 mol%, bis[3-(triethoxysilane)propyl]disulfide accounts for 27 mol%, and 3-aminopropyltriethoxysilane accounts for 3 mol%, and the sum of the molar percentages of the above four components is 100 mol%. The molar ratio of the total molar number to deionized water in this embodiment is 1:5.6.

[0194] A3. Hydrolysis and condensation: The silanes described in A2 are mixed according to the specified ratio to obtain a silane mixture; hydrochloric acid is added to deionized water to prepare an acidic aqueous solution and the pH is controlled at 3.3 at 25°C. The acidic aqueous solution of this embodiment is added dropwise to the silane mixture of this embodiment at 15°C and carried out under magnetic stirring at a stirring speed of 900 rpm for 2.5 h. Then anhydrous ethanol is added and stirring is continued at the same speed until the endpoint described in step A4 is reached, and the reaction is continued for 10 h. The amount of anhydrous ethanol added in this embodiment is based on the solid content of the sol in step A4 being 27 wt%.

[0195] A4. Endpoint Criterion: The reaction is terminated when the solid content of the sol is 27wt% and no visible precipitate is found. In this embodiment, the solid content is determined by the weighing and drying method: about 1.000g of sol is placed in a weighing bottle that has been constant-weighted and dried at 105℃ until the difference between two consecutive weighings does not exceed 0.002g. The solid content is calculated as the percentage of the mass of the dried solid to the mass of the sampled sol. The criterion for no visible precipitate is that no visible particles settle after standing at 25℃ for 30min.

[0196] A5. Post-processing and quality control: Dynamic organosilicon sol intermediates were obtained by filtration. The pore size of the filter membrane used for filtration was 4.2µm. The dynamic organosilicon sol intermediates were considered qualified if they did not gel after standing for 650 hours under sealed conditions.

[0197] The Cl / N co-modified Zr-MOF nanocrystals in the Zr-MOF@COF@MIP composite particles of this embodiment were prepared through the following steps, wherein Cl is chlorine and N is nitrogen:

[0198] B1. Raw materials: zirconium tetrachloride, 2-aminoterephthalic acid, 2-chloroterephthalic acid, N,N-dimethylformamide, glacial acetic acid, deionized water, nitrogen.

[0199] B2. Ratio: The ligands are 2-aminoterephthalic acid and 2-chloroterephthalic acid; based on the total molar number of ligands, 2-aminoterephthalic acid accounts for 15 mol%, 2-chloroterephthalic acid accounts for 85 mol%, and the sum of the molar percentages of the two is 100 mol%; the total molar ratio of zirconium tetrachloride to the ligands is 1:1.42.

[0200] B3. Solvent-thermal reaction: Under nitrogen protection, zirconium tetrachloride, the ligand of this embodiment, N,N-dimethylformamide, deionized water and glacial acetic acid were mixed. The molar ratio of glacial acetic acid to zirconium tetrachloride was 175:1, and the volume ratio of N,N-dimethylformamide to deionized water was 63:37. After sealing, the mixture was reacted at 85°C for 20 h.

[0201] B4. Endpoint Criteria: After the reaction is complete, cool to room temperature, centrifuge, with a relative centrifugal force of 18000×g, a centrifugation time of 8min, and a centrifugation temperature of 18℃. Wash 7 times alternately with N,N-dimethylformamide and anhydrous ethanol. The volume ratio of N,N-dimethylformamide or anhydrous ethanol used in each wash to the mass ratio of the solid to be washed is 85mL:1g, until the pH of the supernatant from the last wash is measured at 25℃ and is within the range of 5.5 to 7.5 after mixing the supernatant from the last wash with deionized water at a volume ratio of 1:1.

[0202] B5. Post-processing and quality control: Cl / N co-modified Zr-MOF nanocrystals were obtained by vacuum drying at 135℃ and a vacuum degree not exceeding 10kPa for 8h; the median particle size of Cl / N co-modified Zr-MOF nanocrystals was 275nm to be considered qualified.

[0203] The Zr-MOF@COF core-shell intermediate in this embodiment is prepared through the following steps:

[0204] C1. Raw materials: Cl / N co-modified Zr-MOF nanocrystals, 2,4,6-tricarboxymethyl phloroglucinol, p-phenylenediamine, glacial acetic acid, N,N-dimethylformamide, deionized water, nitrogen.

[0205] C2. Ratio: The molar ratio of 2,4,6-tricarboxymethyl phloroglucinol to p-phenylenediamine is 1:1.9; based on the mass of Cl / N co-modified Zr-MOF nanocrystals, the total mass of 2,4,6-tricarboxymethyl phloroglucinol and p-phenylenediamine is 1.8 times the mass of Cl / N co-modified Zr-MOF nanocrystals.

[0206] C3. In-situ growth: Under nitrogen protection, Cl / N co-modified Zr-MOF nanocrystals were dispersed in a mixed solvent of N,N-dimethylformamide and deionized water. In this example, the volume ratio of N,N-dimethylformamide to deionized water was 92:8. Glacial acetic acid was added and the pH of the system was controlled at 5.7 at 25°C. Then, 2,4,6-tricarboxymethyl phloroglucinol and p-phenylenediamine were added. After sealing, the reaction was carried out at 68°C for 20 h.

[0207] C4. Endpoint Criteria: After the reaction, centrifuge at a relative centrifugal force of 18000×g for 8 min at a temperature of 18℃. Wash with anhydrous ethanol 9 times, with a volume ratio of anhydrous ethanol to solids of 85 mL:1 g for each wash, until the pH of the final wash solution mixed with deionized water at a volume ratio of 1:1 is within the range of 5.5 to 7.5 at 25℃.

[0208] C5. Post-processing and quality control: Zr-MOF@COF core-shell intermediates were obtained by vacuum drying at 115℃ and a vacuum degree not exceeding 10kPa for 20h; the covalent organic framework shell thickness was 43nm and the shell continuity rate was 95% to be considered qualified.

[0209] The Zr-MOF@COF@MIP composite particles in this embodiment were prepared by the following steps:

[0210] D1. Raw materials: Zr-MOF@COF core-shell intermediate, 3-(methacryloyloxy)propyltrimethoxysilane, chlorobenzene, 4-vinylpyridine, ethylene glycol dimethacrylate, 2,2'-azobisisobutyronitrile, anhydrous ethanol, deionized water, methanol, glacial acetic acid, nitrogen.

[0211] D2. Introduction of surface initiation sites: The Zr-MOF@COF core-shell intermediate was dispersed in a mixed solvent of anhydrous ethanol and deionized water. In this embodiment, the volume ratio of anhydrous ethanol to deionized water was 53:47. 3-(methacryloyloxy)propyltrimethoxysilane was added. In this embodiment, the amount of 3-(methacryloyloxy)propyltrimethoxysilane added was 27 wt% of the mass of the Zr-MOF@COF core-shell intermediate. The pH was controlled at 5.3 at 25°C, and the reaction was carried out at 56°C for 7 h.

[0212] D3. Surface Molecular Imprinting Polymerization: Under nitrogen protection, chlorobenzene, 4-vinylpyridine, ethylene glycol dimethacrylate, and 2,2'-azobisisobutyronitrile were added to the system obtained in D2. The molar ratio of chlorobenzene to 4-vinylpyridine was 1:5.5, and the molar ratio of 4-vinylpyridine to ethylene glycol dimethacrylate was 1:18.0. The amount of 2,2'-azobisisobutyronitrile added was 1.8 wt% of the total mass of 4-vinylpyridine and ethylene glycol dimethacrylate. The chlorobenzene added to the system obtained in D2... After dispersing the system, it was allowed to stand at 25°C for 30 minutes to confirm that there were no visible oil droplets and no layering. If visible oil droplets or layering appeared, the system was treated with 110W ultrasonic power for 27 minutes before adding 4-vinylpyridine and ethylene glycol dimethacrylate to restore the system to a stable dispersion state. The criterion for a stable dispersion state in this embodiment was that there was no visible layering after standing at 25°C for 30 minutes. The template-containing molecularly imprinted skin was obtained by polymerization at 54°C and a stirring speed of 900 rpm for 10 hours under sealed conditions.

[0213] D4. Template Removal: The particles were washed 18 times with a gradient of methanol and glacial acetic acid. In this embodiment, the gradient was as follows: first, washing with a methanol to glacial acetic acid eluent at a volume ratio of 7:3; then washing with an eluent at a volume ratio of 9:1; and finally washing with pure methanol. The volume ratio of the eluent used in each washing step to the mass ratio of the Zr-MOF@COF@MIP composite particles was 175 mL: 1 g, until the residual amount of chlorobenzene in the Zr-MOF@COF@MIP composite particles was ≤0.05 wt% on a dry basis. In this embodiment, the residual amount of chlorobenzene was determined by gas chromatography, with the dry basis mass of the particles being tested as the calculation basis.

[0214] D5. Post-processing and quality control: Zr-MOF@COF@MIP composite particles were obtained by vacuum drying at 110℃ and a vacuum degree not exceeding 10kPa for 18h. The MIP skin thickness was 35nm and the residual amount of unreacted 4-vinylpyridine on a dry basis was ≤0.02wt% to be considered qualified. In this embodiment, the residual amount of 4-vinylpyridine was determined by gas chromatography, with the dry basis of the tested particles as the calculation basis.

[0215] In this embodiment, the silica carrier is silica fiber.

[0216] The composite coating of this embodiment comprises two layers along the thickness direction, and the mass fraction difference of Zr-MOF@COF@MIP composite particles in adjacent layers is 28wt%. The mass fraction of each layer in this embodiment is based on the total mass of the dynamic organosilicon network matrix and Zr-MOF@COF@MIP composite particles in that layer. The total thickness of the composite coating is 180µm. The molar percentage of silane in the dynamic organosilicon network matrix of bis[3-(triethoxysilane)propyl]disulfide is 27mol%. In this embodiment, the mass fraction of Zr-MOF@COF@MIP composite particles in each layer monotonically increases from the inner layer closer to the silica support to the outer layer farther from the silica support.

[0217] The preparation method of the chlorobenzene impurity online analysis material in this embodiment includes the following steps:

[0218] S1. Provides dynamic organosilicon sol intermediates.

[0219] S2. Prepare Cl / N co-modified Zr-MOF nanocrystals as the core of the Zr-MOF@COF@MIP composite particles;

[0220] S3. Using the Cl / N co-modified Zr-MOF nanocrystals as the core, prepare and provide a Zr-MOF@COF core-shell intermediate;

[0221] S4. Using the Zr-MOF@COF core-shell intermediate as a precursor, prepare and obtain Zr-MOF@COF@MIP composite particles;

[0222] S5. Zr-MOF@COF@MIP composite particles are added to the dynamic organosilicon sol intermediate and mixed under nitrogen protection to obtain a coating solution. Coating solutions for two immobilization and curing cycles are prepared separately. The mass fraction of Zr-MOF@COF@MIP composite particles in the coating solution used in the first cycle is 42 wt%, and the mass fraction of Zr-MOF@COF@MIP composite particles in the coating solution used in the second cycle is 70 wt%. In this embodiment, the mass fraction is calculated based on the total mass of the solids of the dynamic organosilicon sol intermediate and the Zr-MOF@COF@MIP composite particles in the coating solution. After adding Zr-MOF@COF@MIP composite particles to the dynamic organosilicon sol intermediate, ultrasonic treatment is performed at an ultrasonic power of 460 W for 55 min under nitrogen protection until no visible particle agglomerates are found in the coating solution.

[0223] S6. The coating solution is immobilized onto the surface of a silica carrier and cured to form a composite coating, thereby obtaining a material for online analysis of chlorobenzene impurities. Step S6 in this embodiment includes two immobilization and curing cycles, and the mass fraction difference of Zr-MOF@COF@MIP composite particles in the coating solution used in adjacent cycles is 28wt% to form a thickness gradient. The mass fraction of Zr-MOF@COF@MIP composite particles in the coating solution used in the first cycle is 42wt%, and the mass fraction of Zr-MOF@COF@MIP composite particles in the coating solution used in the second cycle is 70wt%. Step S6 in this embodiment uses a combination of dip coating and spray coating to complete the immobilization. The first immobilization is done by dip coating, and the second immobilization is done by spray coating. The curing conditions for step S6 in this embodiment are 130℃ for 4 hours. After the composite coating is cured, it is vacuum treated at 130℃ and a vacuum degree not exceeding 10kPa for 4 hours to ensure that the total amount of residual solvent is ≤1.0wt%. The total amount of residual solvent in this embodiment is determined by headspace gas chromatography, and the dry basis mass of the cured composite coating is used as the calculation basis.

[0224] In this embodiment, pH measurements were performed using a glass pH electrode calibrated at 25°C with standard buffer solutions of pH 4.00 and pH 7.00.

[0225] Features of Example 4: Suitable for applications requiring high-throughput rapid detection and rapid response of ultra-thin MIP cortex, especially suitable for portable online detection equipment and continuous flow injection analysis systems with extremely high analysis speed requirements, and also suitable for real-time monitoring of chlorobenzene impurities under high-temperature process conditions.

[0226] Comparative Example 1: Basically the same as Example 1, except that the preparation step of the Zr-MOF@COF core-shell intermediate is omitted. In the surface initiation site introduction stage of step D2, Cl / N co-modified Zr-MOF nanocrystals are directly used to replace the Zr-MOF@COF core-shell intermediate. Subsequently, surface molecular imprinting polymerization and post-treatment are carried out according to the original steps D3 to D5 to obtain Zr-MOF@MIP composite particles without covalent organic framework shell. These are used to replace the Zr-MOF@COF@MIP composite particles in steps S5 and S6, with other conditions remaining unchanged.

[0227] Comparative Example 2: Basically the same as Example 1, except that all the preparation steps of Zr-MOF@COF@MIP composite particles are omitted. In step S5, Zr-MOF@COF core-shell intermediate is directly used instead of Zr-MOF@COF@MIP composite particles to add dynamic organosilicon sol intermediate. A coating solution with a mass fraction of 40 wt% is prepared for step S6, and other conditions remain unchanged.

[0228] Comparative Example 3: It is basically the same as Example 1, except that in step A2, the molar fraction of silane in bis[3-(triethoxysilane)propyl]disulfide is adjusted to 2 mol%, and the molar fraction of tetraethyl orthosilicate is adjusted to 66 mol% accordingly (methyltrimethoxysilane is kept at 25 mol%, 3-aminopropyltriethoxysilane is kept at 7 mol%, and the sum of the four is 100 mol%), while other conditions remain unchanged.

[0229] Comparative Example 4: Basically the same as Example 1, except that in step A2, the silane molar fraction of bis[3-(triethoxysilane)propyl]disulfide was adjusted to 35 mol%, and the molar fraction of tetraethyl orthosilicate was adjusted to 33 mol% accordingly (methyltrimethoxysilane was kept at 25 mol%, 3-aminopropyltriethoxysilane was kept at 7 mol%, and the sum of the four was 100 mol%), while other conditions remained unchanged.

[0230] Comparative Example 5: Basically the same as Example 1, except that in step S6, the mass fraction of Zr-MOF@COF@MIP composite particles in the coating solution used in the first loading cycle was adjusted to 3 wt%, and the mass fraction of Zr-MOF@COF@MIP composite particles in the coating solution used in the second loading cycle was adjusted to 10 wt%, with other conditions remaining unchanged.

[0231] Comparative Example 6: Basically the same as Example 1, except that in step S6, the mass fraction of Zr-MOF@COF@MIP composite particles in the coating solution used in the first loading cycle was adjusted to 60 wt%, and the mass fraction of Zr-MOF@COF@MIP composite particles in the coating solution used in the second loading cycle was adjusted to 75 wt%, with other conditions remaining unchanged.

[0232] Comparative Example 7: Basically the same as Example 1, except that the amount of 3-(methacryloyloxy)propyltrimethoxysilane added in step D2 was adjusted from 12wt% of the mass of the Zr-MOF@COF core-shell intermediate to 2wt%, while other conditions remained unchanged.

[0233] Comparative Example 8: It is basically the same as Example 1, except that step S6 is changed to only perform a single loading and curing cycle (the gradient multilayer design is cancelled), the mass fraction of Zr-MOF@COF@MIP composite particles in the coating liquid is uniformly 40wt%, the curing conditions are kept at 90℃ for 8h, and other conditions remain unchanged.

[0234] Performance testing:

[0235] Experiment 1: Determination of Molecular Imprinting Factor (IF)

[0236] The imprinting factor IF (IF = Q_MIP / Q_NIP) was calculated based on the ratio of the static equilibrium adsorption capacity of MIP to non-imprinted control particles (NIP, control particles prepared without template chlorobenzene). 100 mg of Zr-MOF@COF@MIP composite particles or corresponding control particle powder samples from each example and comparative example were dispersed in 20 mL of n-hexane solution containing 50 µg / L chlorobenzene. The mixture was equilibrated at 25 ± 1 °C and 150 rpm for 12 h. After filtration through a 0.22 µm filter membrane, the chlorobenzene concentration in the supernatant was quantitatively analyzed by FID gas chromatography, and the adsorption capacity Q (µg / g) was calculated. n ≥ 3 replicates were used. Data processing reports: IF mean ± standard deviation.

[0237] Experiment 2: Comprehensive Performance Evaluation of Online Enrichment and Detection of Gas-Phase Chlorobenzene

[0238] The coated parts (SiO2 fibers) of each embodiment and comparative example were placed in a Φ4 mm stainless steel tube, and a chlorobenzene / benzene mixed vapor (nitrogen carrier gas, 25±1℃, relative humidity 50%±5%, flow rate 50 mL / min) generated by a permeation tube vapor generator was introduced. After enrichment for 15 min, thermal desorption was performed at 250℃ for 2 min, and the peak area was quantitatively analyzed by GC-FID (injector 280℃), n≥3. The limit of detection (LOD) (S / N=3, based on a concentration gradient of 0.1–100 µg / L, unit µg / L), response time t90 (time required for the signal to reach 90% steady state, unit s), and selectivity coefficient α (α=A_chlorobenzene / A_benzene) were comprehensively evaluated. The mean ± standard deviation of each indicator is reported.

[0239] Experiment 3: Coating Tensile Adhesion Test

[0240] A Φ20mm aluminum alloy testing head was bonded to the coating surface of the coated parts (SiO2 fiber, coating area ≥10cm²) in each embodiment and comparative example using a two-component epoxy adhesive. After curing at room temperature for 24 hours, a vertical uniform tensile load (loading rate 1.0MPa / s) was applied using a hydraulic pull-out apparatus at 23±2℃ and 50%±10%RH. The maximum stress and failure mode (interfacial failure / cohesive failure) during coating peeling were recorded, with n≥5. The data processing report includes the mean ± standard deviation of tensile bond strength (MPa) and the distribution ratio of failure modes.

[0241] Experiment 4: Stability Test for Continuous Cyclic Use

[0242] The coated specimens of each embodiment and comparative example were enriched in 10 µg / L chlorobenzene nitrogen vapor (25°C, 50 mL / min) for 15 min, thermally desorbed at 250°C for 2 min, and then quantified by GC-FID. A total of 500 continuous enrichment-desorption cycles were performed. After every 100 cycles, a 1% hydrochloric acid vapor wash (10 min, simulating acidic conditions) was inserted. The mean peak area at each node was recorded, with n=3 parallel specimens. Cyclic stability (%) was calculated by dividing the mean peak area of ​​the 500th cycle by the mean peak area of ​​the 1st cycle and multiplying by 100%. The mean ± standard deviation of each 100-cycle node was presented as a line graph using Origin.

[0243] Experiment 5: Multi-stage layer-by-layer structural characterization using FTIR infrared spectroscopy

[0244] Zr / N co-modified Zr-MOF nanocrystals, Zr-MOF@COF core-shell intermediates, Zr-MOF@COF@MIP composite particles, and Comparative Example 1 (Zr-MOF@MIP, without COF layer) were prepared using the KBr pellet method (sample / KBr mass ratio approximately 1:100). The samples were then analyzed by FTIR at 400–4000 cm⁻¹. -1 Scan range, 4cm -1 Spectra were acquired at room temperature under conditions of high resolution, 32 cumulative scans, and dual-beam correction against air background, with n≥3. The evolution of characteristic bonds during the layer-by-layer assembly process was traced using overlay images, with a focus on the imine bonds in the COF layer (C=N stretching, ~1620 cm⁻¹). -1 ), MIP layer pyridine C=C bond (~1595cm) -1 ) and the CS stretching (~650cm) introduced by bis[3-(triethoxysilyl)propyl]disulfide -1 ) and SS telescopic (~480cm) -1 Export the data (wavenumber, transmittance) in CSV format, plot the overlay using Origin, and label the characteristic peak positions and their assignments.

[0245] Experiment 6: XRD Crystal Structure and Phase Analysis

[0246] The Cl / N co-modified Zr-MOF nanocrystals, Zr-MOF@COF core-shell intermediates, Zr-MOF@COF@MIP composite particles from Example 1, as well as the powder samples from Comparative Example 1 (without COF) and Comparative Example 2 (without MIP), were flattened onto a glass sample holder. CuKα radiation (λ=1.5406Å) was used, and diffraction data were acquired in the range of 2θ=3°–50° with a step size of 0.02° and a scanning rate of 4° / min under the conditions of tube voltage of 40kV and tube current of 40mA, with n≥2 parallel samples. The retention of characteristic peaks (2θ≈7.4°, 8.5°, etc.) of the UiO-66 type fcu crystal structure of Zr-MOF after multi-level assembly, the appearance and disappearance of the low-angle crystallization characteristic peaks (2θ≈3–5°) of the COF layer (no such peak in Comparative Example 1), and the amorphization effect after the introduction of the MIP skin were confirmed by overlay plotting. CSV data (2θ, intensity) were exported and overlay plotted using Origin, with characteristic peak positions and crystal plane indices marked.

[0247] Figure 1 This is a superimposed FTIR infrared spectrum of Example 1 and Comparative Example 1. The basic parameters are: Fourier transform infrared spectroscopy was used for characterization, and the horizontal axis represents the wavenumber (cm). -1 Furthermore, the data is arranged in reverse order from high to low, with the vertical axis representing the percentage of transmittance and displayed using the same intensity normalization. The variable parameter is whether the COF structure is introduced into the sample formulation, i.e., Example 1 contains COF while Comparative Example 1 does not. The conclusion is that Example 1 transmits at approximately 1620 cm⁻¹. -1 The characteristic peak of C=N stretching vibration associated with the COF structure appears at a certain point, while the corresponding signal is missing in Comparative Example 1. Furthermore, both peaks are located at approximately 1595 cm⁻¹. -1 Absorption bands associated with the MIP framework were visible in the vicinity, indicating that Example 1 successfully constructed a COF and coexisted with the MIP system, demonstrating the correctness of the composite structure construction and the rationality of the component design from the perspective of chemical bonding.

[0248] Figure 2The XRD crystal structures of Example 1, Comparative Example 1, and Comparative Example 2 are overlaid. The basic parameters are: X-ray diffraction test as the characterization method; the horizontal axis is the 2θ angle range covering the low-angle to mid-high-angle range; the vertical axis is the diffraction intensity au, and all curves are compared under the same coordinates and plotting scale. The variable parameter is the introduction of COF and MIP structural units in the samples, i.e., Example 1 contains both COF and MIP, Comparative Example 1 does not contain COF, and Comparative Example 2 does not contain MIP. The conclusion is that all three retain the UiO-66 related characteristic diffraction peaks, indicating that the MOF framework is not destroyed. Example 1 and Comparative Example 2, which contain COF, show corresponding COF diffraction signals in the low-angle region, while Comparative Example 1 does not. Moreover, the low-angle peak intensity of Example 1 is lower than that of Comparative Example 2, accompanied by background elevation, which is consistent with the rule that MIP coating and recombination lead to a decrease in crystal diffraction contrast. From the aspects of crystal structure consistency and difference, it is jointly proved that the introduction of COF and MIP coating are achieved simultaneously without destroying the main MOF structure, verifying the rationality of the scheme.

[0249] Figure 3 The XPS S 2p high-resolution overlay spectra of Examples 1, 3, and 4 are shown. The basic parameters are: the characterization method is high-resolution X-ray photoelectron spectroscopy; the horizontal axis is the binding energy in eV, displayed in reverse order from high to low binding energy according to XPS convention; the vertical axis is the photoelectron signal intensity au, compared within the same energy range. The variable parameters are the different sulfur monomer ratios: 18 mol% for Example 1, 2 mol% for Example 3, and 35 mol% for Example 4. The conclusion is that Example 1 shows a clear S-related peak shape and sufficient peak area near 163.5 to 164.5 eV. The significantly weakened signal in Example 3 indicates insufficient introduction of sulfur-related structures. In contrast, the peak area in Example 4 further increases, and the peak broadening and the trend of high binding energy side peaks indicate that excessive sulfur structures lead to a wider chemical environment distribution and an increased possibility of side reactions. This shows that 18 mol% can ensure the effective introduction of sulfur phase binding while avoiding the peak anomalies caused by excessive introduction, proving that the ratio selection is chemically reasonable and structurally controllable.

[0250] Figure 4 This is a magnified overlay image of the low wavenumber region of FTIR from Example 1 and Comparative Example 3. The basic parameters are: Fourier transform infrared spectroscopy was used for characterization, and the horizontal axis represents the wavenumber (cm). -1 Furthermore, the images are arranged in reverse order from high to low and focused on a focal length of 400 to 800 cm. -1 The interval and vertical axis represent the percentage of transmittance, and the variable parameter is the difference in the sulfur monomer ratio, i.e., 18 mol% in Example 1 and 2 mol% in Comparative Example 3. The conclusion is that Example 1 transmittance at approximately 650 cm⁻¹ -1 Significant C–S related absorption was observed at approximately 480 cm⁻¹. -1The presence of S–S related absorption in Example 1, while the absorption in Comparative Example 3 is significantly reduced, indicates that Example 1 can form a more complete sulfur-containing bonded network, which is consistent with the XPS results. From the perspective of functional group vibration, it further proves that a moderate sulfur ratio is beneficial to the construction of the target structure and the formation of the performance basis, reflecting the correctness and consistency of the scheme design.

[0251] Figure 5 The image shown is a macroscopic optical photograph of the material used for online analysis of chlorobenzene impurities in Example 1. The basic parameters are: silica fiber as the carrier with a composite coating fixed on the surface; the total thickness of the composite coating is 80µm, and it is constructed by two cycles of dip-coating, fixation, and curing. The variable parameters are: the composite coating is divided into two layers along the thickness direction, and the mass fraction of Zr-MOF@COF@MIP composite particles monotonically increases from 25wt% in the inner layer near the silica carrier to 50wt% in the outer layer. The conclusion is that the macroscopic appearance of the sample should be a continuous and uniform fibrous coating without obvious delamination or macroscopic cracking tendency. This indicates that dip-coating, fixation, 90℃ curing, and subsequent vacuum treatment can form a stable composite coating and achieve a thickness gradient design, thereby ensuring repeatability and long-term stability in online analysis.

[0252] Figure 6 The image shown is a scanning electron microscope (SEM) image of the material used in the online analysis of chlorobenzene impurities in Example 1. The basic parameters are: the characterization method is SEM, which includes both surface and cross-sectional morphology; the variable parameters are: a 25 wt% difference in the mass fraction of Zr-MOF@COF@MIP composite particles in the two-layer composite coating, which monotonically increases from the inside to the outside; and the composite particles are sonicated at 300W for 30 minutes in the coating solution to reduce agglomeration. The conclusion is that at low magnification, the coating should show continuous coverage and tight bonding with the silica fiber interface; at medium and high magnification, the Zr-MOF@COF@MIP composite particles should show a distribution difference from sparse inside to dense outside in the dynamic organosilicon network matrix; and the cross-section should show a structural gradient from low filler in the inner layer to high filler in the outer layer and a clear thickness boundary. This proves that the gradient two-layer immobilization and curing cycle can effectively construct a particle content gradient and take into account the rationality of adhesion and mass transfer channels.

[0253] Table 1 Performance Comparison Summary Table

[0254] Sample number Imprinting factor IF Limit of detection (LOD) (µg / L) Response time t90(s) Selectivity coefficient α Cyclic stability (%) Adhesion (MPa) Example 1 8.2±0.3 0.8±0.1 45±3 12.5±0.8 91±2 3.8±0.2 Example 2 7.5±0.4 0.5±0.1 35±2 11.8±0.6 88±3 3.2±0.3 Example 3 9.1±0.3 1.2±0.2 65±4 14.2±1.0 93±2 4.5±0.2 Example 4 8.8±0.4 0.7±0.1 28±3 13.6±0.9 89±2 5.2±0.3 Comparative Example 1 5.2±0.5 2.1±0.3 58±5 7.3±0.6 75±4 2.8±0.3 Comparative Example 2 1.2±0.2 8.5±0.5 52±4 2.1±0.3 82±3 3.5±0.2 Comparative Example 3 6.8±0.4 1.5±0.2 50±4 9.8±0.7 62±5 2.2±0.4 Comparative Example 4 5.5±0.5 2.8±0.3 72±5 8.2±0.7 71±4 2.5±0.3 Comparative Example 5 4.8±0.5 3.5±0.4 88±6 6.5±0.6 80±3 3.0±0.3 Comparative Example 6 3.2±0.6 5.2±0.5 125±8 4.8±0.5 65±5 1.8±0.4 Comparative Example 7 3.8±0.4 4.2±0.4 32±3 5.2±0.5 72±4 3.4±0.3 Comparative Example 8 7.2±0.4 1.5±0.2 68±5 11.2±0.8 78±4 2.9±0.3

[0255] Note: IF = Imprinting Factor (the ratio of chlorobenzene adsorption by MIP to NIP, dimensionless, the higher the better); LOD = Limit of Detection (S / N = 3, the lower the better); t90 = Response Time (the time required for the signal to reach 90% steady state, the shorter the better); α = Selectivity Coefficient (the ratio of chlorobenzene / benzene peak area, the higher the better); Cyclic Stability = Signal Retention Rate after 500 Cycles (the higher the better); Adhesion = Tensile Bond Strength (the higher the better); Data Format: Mean ± Standard Deviation (n≥3).

[0256] As can be seen from the performance of the examples and comparative examples in Table 1, the imprinting factors of Examples 1–4 are 7.5–9.1, the detection limits are 0.5–1.2 µg / L, and the cycling stability is 88–93%, all of which are significantly better than all the comparative examples, comprehensively verifying the superiority of the technical solution of the present invention. Comparative Example 1, omitting the COF shell, resulted in an IF decreasing to 5.2 and a LOD deteriorating to 2.1 µg / L, indicating that COF provides ordered spatial constraints and additional π-π cooperative recognition contributions for molecular imprinting; Comparative Example 2, removing the MIP skin, had an IF of only 1.2, proving that the selective recognition of chlorobenzene depends entirely on the molecular imprinting effect rather than physical adsorption. In Comparative Example 3, the molar percentage of bis[3-(triethoxysilyl)propyl]disulfide was too low, only 2 mol%, resulting in insufficient disulfide bond density in the dynamic organosilicon network. This led to a sharp drop in cycle stability to 62% and adhesion to only 2.2 MPa. In Comparative Example 4, the molar percentage was too high, reaching 35 mol%, causing excessive rigidity of the crosslinked structure, increased mass transfer resistance, a delayed response time to 72 s, and a simultaneous decrease in stability to 71%. In Comparative Example 5, the particle mass fraction was too low, resulting in insufficient recognition site density. In Comparative Example 6, the particle mass fraction was too high, leading to deterioration of film uniformity. Both extremes significantly degraded IF and stability; the adhesion of Comparative Example 6 even dropped to 1.8 MPa, validating the rationality of the 10–70 wt% parameter range. In Comparative Example 7, the MIP skin layer was too thin, about 12 nm, which greatly reduced the number of imprinted cavities and deteriorated the LOD to 4.2 µg / L. Comparative Example 8 used a single-layer uniform coating and lacked gradient interface control. Its cycle stability was only 78% and its adhesion was only 2.9 MPa, both of which were lower than those of the gradient coating examples. This fully demonstrates that the gradient multilayer design plays a key role in balancing mass transfer efficiency and coating mechanical durability.

[0257] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that any equivalent structural transformations made under the concept of the present invention and using the contents of the specification and drawings of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A material for online analysis of chlorobenzene impurities, characterized in that, The invention comprises a silica carrier and a composite coating fixed on the surface of the silica carrier; the composite coating comprises a dynamic organosilicon network matrix and composite particles dispersed in the dynamic organosilicon network matrix. The composite particles are Zr-MOF@COF@MIP composite particles. The Zr-MOF@COF@MIP composite particles are core-shell-skin structure composite particles with Zr-MOF nanocrystals as the core, covalent organic framework COF as the coating shell, and molecularly imprinted polymer MIP as the outermost skin layer. Zr-MOF is a zirconium-based metal-organic framework, COF is a covalent organic framework, and MIP is a molecularly imprinted polymer. The Zr-MOF@COF@MIP composite particles have a mass fraction of 10–70 wt%, which is based on the total mass of the dynamic organosilicon network matrix and the Zr-MOF@COF@MIP composite particles in the composite coating; the dynamic organosilicon network matrix is ​​obtained by curing a dynamic organosilicon sol intermediate, and the dynamic organosilicon network matrix contains a disulfide bond structure introduced by bis[3-(triethoxysilyl)propyl]disulfide; the median particle size of the Zr-MOF@COF@MIP composite particles is 100–500 nm, and the MIP skin thickness of the Zr-MOF@COF@MIP composite particles is 20–200 nm; The composite coating comprises at least two layers along its thickness direction, and the mass fraction difference between adjacent layers of Zr-MOF@COF@MIP composite particles is 5–40 wt%, wherein the mass fraction of each layer is based on the total mass of the dynamic organosilicon network matrix and the Zr-MOF@COF@MIP composite particles in that layer; the total thickness of the composite coating is 5–200 µm; and the molar percentage of silane in the dynamic organosilicon network matrix of bis[3-(triethoxysilane)propyl]disulfide is 5–30 mol.

2. The online chlorobenzene impurity analysis material according to claim 1, characterized in that, The dynamic organosilicon sol intermediate is prepared through the following steps: A1. Raw materials: tetraethyl orthosilicate, methyltrimethoxysilane, bis[3-(triethoxysilyl)propyl]disulfide, 3-aminopropyltriethoxysilane, hydrochloric acid, anhydrous ethanol, deionized water; A2. Proportioning: Based on the total molar amount of tetraethyl orthosilicate, methyltrimethoxysilane, bis[3-(triethoxysilyl)propyl]disulfide, and 3-aminopropyltriethoxysilane, tetraethyl orthosilicate accounts for 30–70 mol%, methyltrimethoxysilane accounts for 10–40 mol%, bis[3-(triethoxysilyl)propyl]disulfide accounts for 5–30 mol%, and 3-aminopropyltriethoxysilane accounts for 1–15 mol%, and the sum of the molar percentages of the above four components is 100 mol%; the molar ratio of the total molar amount to deionized water is 1:2–6; A3. Hydrolysis and condensation: The silanes described in A2 are mixed in the specified proportions to obtain a silane mixture; hydrochloric acid is added to deionized water to prepare an acidic aqueous solution, and the pH is controlled at 1.5–3.5 at 25°C. The acidic aqueous solution is added to the silane mixture at 10–40°C and reacted for 0.5–3 hours. Then anhydrous ethanol is added and the reaction continues for 1–12 hours. The amount of anhydrous ethanol added is such that the solid content of the sol described in step A4 is 5–30 wt%. A4. Endpoint criterion: The reaction is terminated when the solid content of the sol is 5–30 wt% and no visible precipitate is found. A5. Post-processing and quality control: The dynamic organosilicon sol intermediate was obtained by filtration. The pore size of the filter membrane used for filtration was 0.22–5µm. The dynamic organosilicon sol intermediate was considered qualified if it did not gel after standing for 168–720 hours under closed conditions.

3. The online analysis material for chlorobenzene impurities according to claim 1, characterized in that, The Zr-MOF nanocrystals in the Zr-MOF@COF@MIP composite particles are Cl / N co-modified Zr-MOF nanocrystals, which are prepared by the following steps, wherein Cl is chlorine and N is nitrogen: B1. Raw materials: zirconium tetrachloride, 2-aminoterephthalic acid, 2-chloroterephthalic acid, N,N-dimethylformamide, glacial acetic acid, deionized water, nitrogen; B2. Ratio: The ligands are 2-aminoterephthalic acid and 2-chloroterephthalic acid; based on the total molar number of ligands, 2-aminoterephthalic acid accounts for 10–70 mol%, and 2-chloroterephthalic acid accounts for 30–90 mol%, and the sum of the molar percentages of the above two is 100 mol%; the total molar ratio of zirconium tetrachloride to the total ligands is 1:0.8–1.5; B3. Solvent-thermal reaction: Under nitrogen protection, zirconium tetrachloride, the ligand, N,N-dimethylformamide, deionized water and glacial acetic acid are mixed. The molar ratio of glacial acetic acid to zirconium tetrachloride is 10–200:1, and the volume ratio of N,N-dimethylformamide to deionized water is 95:5 to 60:

40. After sealing, the mixture is reacted at 80–130°C for 6–24 h. B4. Endpoint Criteria: After the reaction is complete, cool to room temperature, centrifuge, with a relative centrifugal force of 3000–20000 × g, a centrifugation time of 5–30 min, and a centrifugation temperature of 15–30 °C. Wash with N,N-dimethylformamide and anhydrous ethanol alternately 3–8 times, with the volume ratio of N,N-dimethylformamide or anhydrous ethanol to the mass of the solid to be washed being 10–100 mL:1 g each time, until the pH of the supernatant from the last wash is 5.5–7.5 when it is mixed with deionized water at a volume ratio of 1:1 and measured at 25 °C. B5. Post-processing and quality control: Vacuum drying at 80–140℃ and a vacuum degree not exceeding 10kPa for 6–24h yields Cl / N co-modified Zr-MOF nanocrystals; the median particle size of Cl / N co-modified Zr-MOF nanocrystals is 50–300nm to be considered qualified.

4. The online analysis material for chlorobenzene impurities according to claim 1, characterized in that, The Zr-MOF@COF@MIP composite particles contain Cl / N co-modified Zr-MOF nanocrystals coated with a covalent organic framework COF shell. The Zr-MOF@COF core-shell intermediate is prepared through the following steps: C1. Raw materials: Cl / N co-modified Zr-MOF nanocrystals, 2,4,6-tricarboxymethyl phloroglucinol, p-phenylenediamine, glacial acetic acid, N,N-dimethylformamide, deionized water, nitrogen; C2. Ratio: The molar ratio of 2,4,6-tricarboxymethyl phloroglucinol to p-phenylenediamine is 1:1.0–2.0; based on the mass of Cl / N co-modified Zr-MOF nanocrystals, the total mass of 2,4,6-tricarboxymethyl phloroglucinol and p-phenylenediamine is 0.2–2.0 times the mass of Cl / N co-modified Zr-MOF nanocrystals; C3. In-situ growth: Under nitrogen protection, Cl / N co-modified Zr-MOF nanocrystals were dispersed in a mixed solvent of N,N-dimethylformamide and deionized water, wherein the volume ratio of N,N-dimethylformamide to deionized water was 95:5 to 60:

40. Glacial acetic acid was added and the pH of the system was controlled at 3.0–6.0 at 25°C. Subsequently, 2,4,6-tricarboxymethyl phloroglucinol and p-phenylenediamine were added. After sealing, the reaction was carried out at 60–120°C for 6–24 h. C4. Endpoint Criteria: After the reaction is complete, centrifuge at a relative centrifugal force of 3000–20000 × g, a centrifugation time of 5–30 min, and a centrifugation temperature of 15–30 °C. Wash with anhydrous ethanol 3–10 times, with the volume ratio of anhydrous ethanol to the mass of the solid to be washed being 10–100 mL: 1 g each time, until the pH of the final wash solution mixed with deionized water at a volume ratio of 1:1 is 5.5–7.5 as measured at 25 °C. C5. Post-processing and quality control: Zr-MOF@COF core-shell intermediates are obtained by vacuum drying at 60–120℃ and a vacuum degree not exceeding 10kPa for 6–24h; the covalent organic framework shell thickness is 5–50nm and the shell continuity rate is ≥70% to be qualified.

5. The online chlorobenzene impurity analysis material according to claim 4, characterized in that, Zr-MOF@COF@MIP composite particles were prepared using the Zr-MOF@COF core-shell intermediate as a precursor through the following steps: D1. Raw materials: Zr-MOF@COF core-shell intermediate, 3-(methacryloyloxy)propyltrimethoxysilane, chlorobenzene, 4-vinylpyridine, ethylene glycol dimethacrylate, 2,2'-azobisisobutyronitrile, anhydrous ethanol, deionized water, methanol, glacial acetic acid, nitrogen; D2. Introduction of surface initiation sites: The Zr-MOF@COF core-shell intermediate was dispersed in a mixed solvent of anhydrous ethanol and deionized water, wherein the volume ratio of anhydrous ethanol to deionized water was 95:5 to 50:

50. 3-(methacryloyloxy)propyltrimethoxysilane was added, wherein the amount of 3-(methacryloyloxy)propyltrimethoxysilane added was 1–30 wt% of the mass of the Zr-MOF@COF core-shell intermediate. The pH was controlled at 3.5–5.5 at 25 °C, and the reaction was carried out at 20–60 °C for 1–8 h. D3. Surface molecular imprinting polymerization: Under nitrogen protection, chlorobenzene, 4-vinylpyridine, ethylene glycol dimethacrylate and 2,2'-azobisisobutyronitrile were added to the system obtained in D2. The molar ratio of chlorobenzene to 4-vinylpyridine was 1:1.0–6.0, and the molar ratio of 4-vinylpyridine to ethylene glycol dimethacrylate was 1:2.0–20.

0. The amount of 2,2'-azobisisobutyronitrile added was 0.1–2.0 wt% of the total mass of 4-vinylpyridine and ethylene glycol dimethacrylate. The polymerization was carried out under closed conditions at 50–80°C and a stirring speed of 200–1000 rpm for 2–12 h to obtain a template-containing molecularly imprinted skin. D4. Template Removal: Wash 3–20 times with a gradient of methanol and glacial acetic acid eluent. The gradient is as follows: first wash with an eluent with a methanol to glacial acetic acid volume ratio of 7:3, then wash with an eluent with a volume ratio of 9:1, and finally wash with pure methanol. The volume ratio of the eluent used in each washing step to the mass ratio of the Zr-MOF@COF@MIP composite particles is 10–200 mL:1 g, until the residual amount of chlorobenzene in the Zr-MOF@COF@MIP composite particles is ≤0.05 wt% on a dry basis. D5. Post-processing and quality control: Zr-MOF@COF@MIP composite particles are obtained by vacuum drying at 40–120℃ and a vacuum degree not exceeding 10kPa for 6–24h; the MIP skin thickness is 20–200nm and the residual amount of unreacted 4-vinylpyridine on a dry basis is ≤0.02wt% to be considered qualified.

6. The online analysis material for chlorobenzene impurities according to claim 1, characterized in that, The silica carrier is silica fiber.

7. A method for preparing an online analytical material for chlorobenzene impurities as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Provides dynamic organosilicon sol intermediates; S2. Prepare Cl / N co-modified Zr-MOF nanocrystals as the core of the Zr-MOF@COF@MIP composite particles; S3. Prepare Zr-MOF@COF core-shell intermediates using the Cl / N co-modified Zr-MOF nanocrystals as the core; S4. Using the Zr-MOF@COF core-shell intermediate as a precursor, Zr-MOF@COF@MIP composite particles are prepared and obtained. S5. Add Zr-MOF@COF@MIP composite particles to dynamic organosilicon sol intermediate and mix to obtain a coating solution. The mass fraction of Zr-MOF@COF@MIP composite particles in the coating solution is 10–70 wt%, and the mass fraction is calculated as the total mass of the solids of dynamic organosilicon sol intermediate and the Zr-MOF@COF@MIP composite particles in the coating solution. S6. The coating liquid is fixed onto the surface of the silica carrier and cured to form a composite coating, thus obtaining a material for online analysis of chlorobenzene impurities.

8. The preparation method according to claim 7, characterized in that, The mixing in step S5 is carried out under nitrogen protection; step S6 includes at least two loading and curing cycles, and the mass fraction difference of Zr-MOF@COF@MIP composite particles in the coating liquid used in adjacent cycles is 5–40 wt% to form a thickness gradient. Step S6 is completed by at least one of dip coating, spray coating or casting; the curing conditions of step S6 are 40–140℃, 0.5–24h; after the composite coating is cured, it is vacuum treated at 40–140℃ and vacuum degree not higher than 10kPa for 0.5–24h to make the total amount of residual solvent ≤1.0wt%. The total amount of residual solvent is determined by headspace gas chromatography, and the dry basis mass of the cured composite coating is used as the calculation basis.

9. The preparation method according to claim 7, characterized in that, In step S2, the molar ratio of glacial acetic acid to zirconium tetrachloride is 10–200:1 in the preparation of the Cl / N co-modified Zr-MOF nanocrystals; in step S3, the volume ratio of N,N-dimethylformamide to deionized water is 95:5 to 60:40 in the preparation of the Zr-MOF@COF@MIP composite particles; in step S4, the amount of 2,2'-azobisisobutyronitrile added is 0.1–2.0 wt% of the total mass of 4-vinylpyridine and ethylene glycol dimethacrylate.

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