阅读说明：本技术 一种类共价有机材料及其制备方法和应用 (Covalent-like organic material and preparation method and application thereof ) 是由 王耀 王权 尹昱博 周国富 于 2021-08-26 设计创作，主要内容包括：本发明公开了一种类共价有机材料及其制备方法和应用,所述类共价有机材料的制备方法包括如下步骤：将含化合物1与化合物2的混合溶液调节至pH为0.5～3,然后进行水热反应,得到类共价有机材料。本发明利用了在高温高压下从过饱和热水溶液中培养晶体的方法,采用了化合物1和化合物2为前驱体,通过一步水热法制备了对甲醛具有特殊响应性能的类共价有机材料；合成方法简单便捷、反应条件温和,原料成本低廉,对环境友好。通过以上制备方法制得的类共价有机材料能在室温条件下对甲醛气体发生快速响应,并且具有反应灵敏度高、检测限低、恢复速度快的优点。(The invention discloses a covalent organic material and a preparation method and application thereof, wherein the preparation method of the covalent organic material comprises the following steps: will contain the compound 1 With compound 2)

1. A covalent organic-like material characterized by: the covalent organic-like material has a chemical structural formula as shown in formula I:

m and n are independently integers between 0 and 6, and R₁Is H, C_1～6Hydrocarbyl or C_1～6A substituted hydrocarbyl group.

2. The covalent organic-like material of claim 1, wherein: the R is₁Is H or C_1～3Alkanes, preferably H.

3. The covalent organic-like material of claim 1, wherein: the chemical structural formula of the covalent organic-like material is

4. A composition as claimed in any one of claims 1 to 3A method for preparing a valuable organic material, characterized in that: the method comprises the following steps: will contain the compound 1With compound 2Adjusting the pH value of the mixed solution to 0.5-3, and then carrying out hydrothermal reaction to obtain a covalent organic material; m and n are independently integers between 0 and 6, and R₁Is H, C_1～6Hydrocarbyl or C_1～6A substituted hydrocarbyl group.

5. The method according to claim 4, wherein: the method of adjusting the pH is by adding an acid to the mixed solution; preferably, the acid comprises at least one of boric acid, phosphoric acid, hydrochloric acid, acetic acid, sulfuric acid; preferably, the acid is added in the form of an acid solution, and the mass fraction of the acid solution is 30-37%; preferably, the volume ratio of the mixed solution to the acid solution is 1 mL: 1 to 70 μ L.

6. The method according to claim 4, wherein: the molar ratio of the compound 1 to the compound 2 is 1-2: 1; preferably, the mass-volume concentration of the compound 1 in the mixed solution is 2-3 g/100 mL.

7. The method according to claim 4, wherein: the temperature of the hydrothermal reaction is 90-220 ℃; preferably, the time of the hydrothermal reaction is 5-72 h; preferably, the hydrothermal reaction is carried out in a closed container, and the ratio of the volume of the mixed solution to the volume of the container is 1: 2 to 5.

8. Use of the covalent organic material of any one of claims 1 to 3 or the covalent organic material prepared by the preparation method of any one of claims 4 to 7 in the detection of formaldehyde.

9. A gas-sensitive electrode, characterized by: the surface of the gas-sensitive electrode is provided with a gas-sensitive coating, and the gas-sensitive coating contains the covalent-like organic material as described in any one of claims 1 to 3 or the covalent-like organic material prepared by the preparation method as described in any one of claims 4 to 7.

10. A sensor or sensing equipment for formaldehyde detection, characterized in that: the sensor or sensing device for formaldehyde detection comprising the gas sensitive electrode of claim 9.

Technical Field

The invention relates to the technical field of gas-sensitive materials, in particular to a covalent organic material and a preparation method and application thereof.

Background

The rapid development of modern society industry and agriculture enables the living standard of people to be rapidly improved, meanwhile, certain pollution is caused to the environment, and the life health and property safety of people are seriously harmed. Among various environmental pollutions, air pollution is the most concerned, and the harm to people is the most direct and the most threatening. The poisonous and harmful gas in the air can damage the health of people all the time along with the breathing of people. Formaldehyde (HCHO) gas is used as a main component of indoor pollutants, and brings great trouble to daily life of people due to the characteristics of long existence time and great harm. Formaldehyde is a flammable, colorless, pungent and smelly toxic gas, and is widely used in various indoor furniture and decoration materials which are closely contacted in daily life. The formaldehyde has strong toxicity, potential health safety hazards can exist when the formaldehyde is exposed in the formaldehyde environment, and the human health poses a great threat. Studies have shown that prolonged exposure to formaldehyde vapor can lead to a variety of ailments, such as mucosal inflammation, throat pain, pulmonary edema, nausea, vomiting, leukemia, pregnancy syndromes, brain tumors, and the like. In 2006, the international agency for research on cancer (IARC) upgraded the classification of formaldehyde from "potentially carcinogenic" to "carcinogenic to humans". Formaldehyde has been listed as a mutagen and possibly a carcinogen by the us environmental protection agency and the world health organization. It is noteworthy that only 0.4ppm of formaldehyde causes irritation to the eyes and nose. The investigation shows that the time of people in the indoor environment accounts for up to 70-90%. The indoor protection limit of the World Health Organization (WHO) to formaldehyde is 0.08mg/m³. Although formaldehyde has pungent odor, the human olfactory valve to formaldehyde is usually 0.06-0.07 mg/m³And the detection of the low-concentration formaldehyde in the indoor environment cannot be realized. Therefore, the real-time monitoring of the formaldehyde in the environment is promoted to be developed in a direction of being faster, more sensitive and more intelligent, and the method has great significance for protecting the life health and safety of people.

Due to the wide existence and great toxicity of formaldehyde, the development and research of formaldehyde sensors have been widely concerned by researchers for a long time. The existing formaldehyde detection methods are many, and common methods comprise a photometric method, a chromatographic method, an electrochemical analysis method, an instrument monitoring method and the like. The instruments for detecting indoor formaldehyde are mainly distributed in developed countries such as Europe, America and Japan. For example, a INTERSCAN4160 type instrument for detecting formaldehyde in real time is developed by the company of INTERSCAN in the United states, the resolution is 0.01ppm, and the detection range is 0-20 ppm; the XP-308B formaldehyde detector developed by Japan COSMOS company has the resolution of 0.01ppm and the detection range of 0.01-3 ppm; the resolution of the PPM-HTV formaldehyde detector developed by British PPM company is 0.01PPM, and the detection range is 0.01-10 PPM. The formaldehyde detection instruments developed by the companies have leading indexes in the aspects of resolution, detection range and the like all around the world, but the detectors are very expensive and cannot achieve the aim of common use. Meanwhile, the development of the formaldehyde detector in China is still in an initial stage and mainly comprises a spectrophotometer, a colorimeter, an electrochemical analyzer and the like. Among them, the development of formaldehyde gas sensors for electrochemical analyzers is mainly used. In recent years, Covalent Organic materials (COFs) are distinguished from other materials by simple preparation methods, excellent performance and unique Covalent structures, and attract the attention of a plurality of experts and scholars, so that the Covalent Organic materials have great application potential in the directions of adsorption, catalysis, chiral resolution and the like.

Most of materials for formaldehyde sensing are metal oxides, or metal oxides are doped, and the doping method is various, but has many problems. For example, the practical purposes of convenience, rapidness and flexible use cannot be achieved by a great deal of problems such as high working temperature, insufficient response speed, insufficient recovery speed, low response multiple and the like, complex manufacturing process, high energy consumption and the like. Therefore, it is important to research how to realize high-sensitivity detection of formaldehyde at room temperature in the field of semiconductor formaldehyde gas sensors.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art. Therefore, the covalent organic material provided by the invention can be used for quickly detecting formaldehyde, and has the advantages of high sensitivity, high response speed, good restorability, low cost and simplicity in preparation.

Meanwhile, the invention also provides a preparation method and application of the covalent organic material.

Specifically, the technical scheme adopted by the invention is as follows:

in a first aspect of the invention, there is provided a covalent-like organic material having the chemical structure of formula I:

m and n are independently integers between 0 and 6, and R₁Is H, C_1～6Hydrocarbyl or C_1～6A substituted hydrocarbyl group.

The covalent organic-like material according to the first aspect of the invention has at least the following beneficial effects:

the substance with the structural formula I is a covalent organic material, and the invention discovers that the substance has special responsiveness to formaldehyde, can be used for quickly detecting the formaldehyde, and has high sensitivity, high response speed and good restorability.

In some embodiments of the present invention, m is an integer between 1 and 3, and n is an integer between 0 and 2.

In some embodiments of the invention, R is₁Is H or C_1～3Alkanes, preferably H.

In some embodiments of the present invention, the chemical structure of the covalent organic-like material is

In a second aspect, the present invention provides a method for preparing a covalent organic-like material, comprising the steps of: will contain the compound 1With compound 2Adjusting the pH value of the mixed solution to 0.5-3, and then carrying out hydrothermal reaction to obtain a covalent organic material; m and n are independently integers between 0 and 6, and R₁Is H, C_1～6Hydrocarbyl or C_1～6A substituted hydrocarbyl group.

The preparation method of the covalent organic material like in the second aspect of the invention has at least the following beneficial effects:

in the prior art, a mixed solution with a structure similar to that of a compound 1 and a compound 2 is generally adopted to prepare a carbon quantum dot material with a fluorescent property through a hydrothermal reaction, and the inventor finds that a covalent organic material, rather than a carbon quantum dot, can be obtained through adjusting the mixed solution of the compound 1 and the compound 2 to be acidic and performing the hydrothermal reaction, and the covalent organic material has special responsiveness to formaldehyde, can be used for rapid detection of formaldehyde, and has the advantages of high sensitivity, high response speed, good restorability, low cost and simplicity in preparation.

In some embodiments of the present invention, the pH of the mixed solution is 0.5 to 2.3, preferably 1 to 2.3, and more preferably 1 to 2.1. Such as about 2.26, 2.09, 1.06, 0.70, 0.58, etc.

In some embodiments of the present invention, the method of adjusting pH is by adding an acid to the mixed solution, wherein the acid is required not to react with the compound 1 and the compound 2, and may comprise at least one of boric acid, phosphoric acid, hydrochloric acid, acetic acid and sulfuric acid. The acidity of the mixed solution is adjusted by adding acid, so that the appearance of the covalent organic material is controlled.

In some embodiments of the invention, the acid is added in the form of an acid solution, the mass fraction of the acid solution being between 30% and 37%.

Preferably, the acid solution is concentrated hydrochloric acid, and the mass fraction of the concentrated hydrochloric acid is 30-37%, preferably 36%; the mass concentration of the substances is 10-15 mol/L, preferably 12 mol/L; the density is 1 to 1.2g/cm³Preferably about 1.179g/cm³。

In some embodiments of the invention, the volume ratio of the mixed solution to the acid solution is 1 mL: 1 to 70 μ L. More specifically, the volume ratio of the mixed solution to the acid solution may be set to 1 mL: 5-65 μ L, 1 mL: 5-35 μ L, 1 mL: 20-35 mu L, 1 mL: 4-10 μ L, 1 mL: 10-30 μ L, 1 mL: 30-45 mu L, 1 mL: 45-55 mu L, 1 mL: 60-70 μ L, etc.

In some embodiments of the present invention, m is an integer between 1 and 3, and n is an integer between 0 and 2.

In some embodiments of the invention, R is₁Is H or C_1～3Alkanes, preferably H.

In some embodiments of the present invention, the compound 1 comprises at least one of o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, preferably o-phenylenediamine.

In some embodiments of the invention, the compound 2 comprises at least one of glutamic acid, aspartic acid, cystine, preferably glutamic acid.

In some embodiments of the invention, compound 1 is o-phenylenediamine and compound 2 is glutamic acid.

In some embodiments of the present invention, the molar ratio of compound 1 to compound 2 is 1-2: 1.

in some embodiments of the invention, the mass-volume concentration of the compound 1 in the mixed solution is 2-3 g/100 mL.

In some embodiments of the invention, the mixed solution is an aqueous solution of compound 1 and compound 2.

In some embodiments of the present invention, the temperature of the hydrothermal reaction is 90 to 220 ℃, and the time of the hydrothermal reaction is 5 to 72 hours.

In some embodiments of the present invention, the hydrothermal reaction is performed in a closed container, and the ratio of the volume of the mixed solution to the volume of the container is 1: 2-5, preferably 1: 2 to 3. The size of the container in which the reaction is carried out, the reaction temperature, the reaction time and the like all influence the internal pressure of the container, and finally influence the type, the morphology and the like of the reaction product. Under such conditions, a covalent-like organic material responsive to formaldehyde can be formed.

In some embodiments of the present invention, the hydrothermal reaction further comprises cooling, filtering, and washing steps after completion.

The third aspect of the invention provides the application of the covalent organic material in the detection of formaldehyde.

The fourth aspect of the invention provides a gas-sensitive electrode, wherein a gas-sensitive coating is arranged on the surface of the gas-sensitive electrode, and the gas-sensitive coating contains the covalent organic material.

The invention also provides a sensor or sensing equipment for detecting formaldehyde, which comprises the gas-sensitive electrode.

Compared with the prior art, the invention has the following beneficial effects:

the present invention utilizes a method of culturing crystals from a supersaturated hot water solution at high temperature and high pressure, using compound 1And compound 2(such as phenylenediamine and amino acid) are used as precursors, and a covalent organic material with special response performance to formaldehyde is prepared by a one-step hydrothermal method; the synthesis method is simple and convenient, the reaction condition is mild, the cost of raw materials is low, and the method is environment-friendly. The covalent-like organic material prepared by the preparation method can quickly respond to formaldehyde gas at room temperature, and has the advantages of high reaction sensitivity, low detection limit and high recovery speed.

Drawings

FIG. 1 is a schematic reaction scheme of o-phenylenediamine and glutamic acid of example 1;

FIG. 2 is an XRD pattern of COFs-like materials of examples 1-5;

FIG. 3 is an SEM topography of COFs-like materials of example 1;

FIG. 4 is an SEM topography of COFs-like materials of example 2;

FIG. 5 is an SEM topography of COFs-like materials of example 3;

FIG. 6 is an SEM topography of COFs-like materials of example 4;

FIG. 7 is an SEM topography of COFs-like materials of example 5;

FIG. 8 is a FT-IR spectrum of COFs-like materials of examples 1 to 5;

FIG. 9 shows the results of the cyclic stability test of the COFs-like material of example 1 for detecting formaldehyde;

FIG. 10 shows the results of the cyclic stability test of the COFs-like material of example 2 for detecting formaldehyde;

FIG. 11 shows the results of the cyclic stability test of the COFs-like material of example 3 for detecting formaldehyde;

FIG. 12 shows the results of the cyclic stability test of the COFs-like material of example 4 for detecting formaldehyde;

FIG. 13 shows the results of the cyclic stability test of the COFs-like material of example 5 for detecting formaldehyde;

FIG. 14 shows the results of the test of the response of COFs-like materials of example 1 to different concentrations of formaldehyde;

FIG. 15 shows the results of the test of the response of COFs-like materials of example 2 to different concentrations of formaldehyde;

FIG. 16 shows the results of the test of the response of COFs-like materials of example 3 to different concentrations of formaldehyde;

FIG. 17 shows the results of the test of the response of the COFs-like material of example 4 to different concentrations of formaldehyde;

FIG. 18 shows the results of the test of the response of COFs-like materials of example 5 to different concentrations of formaldehyde;

FIG. 19 shows the recovery time of the COFs-like materials of examples 1-5 for the same concentration of formaldehyde.

Detailed Description

The technical solution of the present invention is further described below with reference to specific examples. The starting materials used in the following examples, unless otherwise specified, are available from conventional commercial sources; the processes used, unless otherwise specified, are conventional in the art.

Example 1

S1, weighing 0.2705g of o-phenylenediamine and 0.4126g of glutamic acid, dissolving in 10mL of deionized water, and obtaining a uniform dispersion system by ultrasonic oscillation.

S2, adding 50 μ L concentrated salt to the dispersion obtained in step S1Acid (mass fraction of 36%, 12mol/L, density of 1.179 g/cm)³) The pH of the solution was adjusted to acidity (pH 2.26) and stirred well.

S3, putting the mixed solution prepared in the step S2 into a polytetrafluoroethylene high-pressure reaction kettle lining with the capacity of 25mL, screwing up the mixed solution, and transferring the mixed solution into a hydrothermal oven to perform hydrothermal reaction at the reaction temperature of 150 ℃ for 6 hours. The reaction scheme of o-phenylenediamine and glutamic acid during the hydrothermal reaction is shown in FIG. 1.

S4, cooling the reaction solution prepared in the step S3 to room temperature, taking out, filtering and washing with water to obtain the sheet covalent organic materials (COFs-like materials), wherein the labels are COFs-1.

Example 2

S1, weighing 0.2707g of o-phenylenediamine and 0.4127g of glutamic acid, dissolving in 10mL of deionized water, and obtaining a uniform dispersion system by ultrasonic oscillation.

S2, adding 200 μ L concentrated hydrochloric acid into the dispersion system prepared in the step S1, adjusting the pH of the solution to acidity (pH 2.09), and stirring uniformly.

S3, putting the mixed solution prepared in the step S2 into a polytetrafluoroethylene high-pressure reaction kettle lining with the capacity of 25mL, screwing up the mixed solution, and transferring the mixed solution into a hydrothermal oven to perform hydrothermal reaction at the reaction temperature of 150 ℃ for 6 hours.

S4, cooling the reaction solution prepared in the step S3 to room temperature, taking out, filtering and washing with water to obtain flower-shaped COFs (COFs-4).

Example 3

S1, weighing 0.2703g of o-phenylenediamine and 0.4126g of glutamic acid, dissolving in 10mL of deionized water, and obtaining a uniform dispersion system by ultrasonic oscillation.

S2, adding 350 μ L concentrated hydrochloric acid into the dispersion system prepared in the step S1, adjusting the pH of the solution to acidity (pH 1.06), and stirring uniformly.

S3, putting the mixed solution prepared in the step S2 into a polytetrafluoroethylene high-pressure reaction kettle lining with the capacity of 25mL, screwing up the mixed solution, and transferring the mixed solution into a hydrothermal oven to perform hydrothermal reaction at the reaction temperature of 150 ℃ for 6 hours.

S4, cooling the reaction solution prepared in the step S3 to room temperature, taking out, filtering and washing the reaction solution to obtain linear COFs (COFs-7).

Example 4

S1, weighing 0.2705g of o-phenylenediamine and 0.4124g of glutamic acid, dissolving in 10mL of deionized water, and obtaining a uniform dispersion system by ultrasonic oscillation.

S2, adding 500. mu.L concentrated hydrochloric acid into the dispersion system prepared in the step S1, adjusting the pH of the solution to acidity (pH 0.70), and uniformly stirring.

S3, putting the mixed solution prepared in the step S2 into a polytetrafluoroethylene high-pressure reaction kettle lining with the capacity of 25mL, screwing up the mixed solution, and transferring the mixed solution into a hydrothermal oven to perform hydrothermal reaction at the reaction temperature of 150 ℃ for 6 hours.

S4, cooling the reaction liquid prepared in the step S3 to room temperature, taking out, filtering and washing with water to obtain the taxus chinensis branch-like COFs material (COFs-10).

Example 5

S1, weighing 0.2708g of o-phenylenediamine and 0.4125g of glutamic acid, dissolving in 10mL of deionized water, and obtaining a uniform dispersion system by ultrasonic oscillation.

S2, adding 650 μ L concentrated hydrochloric acid to the dispersion system prepared in the step S1, adjusting the pH of the solution to acidity (pH 0.58), and stirring uniformly.

S3, putting the mixed solution prepared in the step S2 into a polytetrafluoroethylene high-pressure reaction kettle lining with the capacity of 25mL, screwing up the mixed solution, and transferring the mixed solution into a hydrothermal oven to perform hydrothermal reaction at the reaction temperature of 150 ℃ for 6 hours.

S4, cooling the reaction solution prepared in the step S3 to room temperature, taking out, filtering and washing the reaction solution with water to obtain the flaky COFs (COFs-13).

In the preparation processes of the above examples 1 to 5, the main variables were the addition amount of concentrated hydrochloric acid, which was 50, 200, 350, 500 and 650. mu.L in this order.

Structural characterization and performance testing:

(1) XRD tests are carried out on the COFs-like materials of examples 1-5, and XRD patterns are shown in FIG. 2. As can be seen from fig. 2, the five samples all show a plurality of distinct diffraction peaks, the narrow peak positions indicate that the COFs-like materials have high crystallinity, and no material which can be well matched with the COFs-like materials is found in the XRD-PDF card library, and the high intensity diffraction peak positions at small angles also make us reasonably doubtful that the metallic luster materials which are originally found in the past may be a class of COFs materials.

(2) SEM electron microscope tests are carried out on the COFs-like materials of examples 1-5, and the obtained SEM topography images are respectively shown in figures 3-7. The results show that the COFs-like materials of example 1 have a fault-sheet structure; the material of example 2 has a petal-like structure; the fiber of the embodiment 3 has a fiber structure, and the diameter of the fiber is distributed between 5 and 10 mu m; the taxus chinensis-like branched structure of example 4; example 5 has a sheet-like structure. And reflecting the shape test result, and changing the shape of the COFs by adjusting the acidity of the reaction system.

(3) FT-IR spectra of COFs-like materials of examples 1 to 5 are shown in FIG. 8. In the FTIR spectrum at 3255cm^-1An absorption band is nearby, which is attributed to stretching vibration of a nitrogen-hydrogen single bond (N-H); at 1661, 1601 and 1120cm^-1Some nearby vibration peaks correspond to stretching vibrations of carbon-nitrogen (C ═ N) or carbon-oxygen double bonds (C ═ O), carbon-carbon double bonds (C ═ C), and carbon-nitrogen single bonds (C — N), respectively; at 3440cm^-1And a vibration peak is arranged nearby, and corresponds to the stretching vibration of the (O-H) single bond.

Example 6

1) Respectively dispersing the COFs-like materials of the embodiments 1-5 in deionized water to obtain sensing material dispersion liquid;

2) dripping the sensing material dispersion liquid prepared in the step 1) on the surface of a test electrode, removing the water of the sensing material dispersion liquid dripped on the test electrode, and forming a gas-sensitive coating on the surface of the test electrode to prepare a gas-sensitive electrode;

3) connecting the gas-sensitive electrode prepared in the step 2) on a gas-sensitive testing device to prepare the sensor for detecting formaldehyde.

The formaldehyde gas to be detected is detected by adopting the formaldehyde detection sensor. The detection method specifically comprises the following steps: the gas-sensitive electrode is placed in a closed test cavity of air atmosphere to test the initial resistance of the gas-sensitive electrode, formaldehyde gas with certain concentration is injected into the test cavity after the stability is achieved, the resistance change of the gas-sensitive electrode is recorded, the test cavity is opened after the response is completed, the air atmosphere in the test cavity is recovered, and the change of the resistance of the gas-sensitive electrode is recorded.

By the above method, formaldehyde gas having a concentration of 5ppm was detected at room temperature (26.3 ℃) and a relative humidity of 43% RH, and a cyclic stability test was performed, and the results are shown in fig. 9 to 13. From the test results of the graph, the COFs material in the example 1 is excellent in the cyclic stability detection of formaldehyde gas, the response multiple to 5ppm of formaldehyde at room temperature is 1.87 times, the response value is basically kept unchanged in 5 cycles, the response value is maintained at about 85%, the cyclic stability is good, and the COFs material has important significance for realizing the long-term accurate repeatability of formaldehyde detection. The COFs material of the embodiment 2 has a response multiple of 2.08 times to 5ppm of formaldehyde at room temperature, and has good cycling stability; the COFs material of the embodiment 3 has the response multiple of 2.26 times to 5ppm of formaldehyde at room temperature, and has good cycle stability; the COFs material of the embodiment 4 has 1.56 times of response times to 5ppm of formaldehyde at room temperature, and has good cycling stability; the COFs material of example 5 has 1.42 times of response time to 5ppm of formaldehyde at room temperature, and has better cycling stability.

Gas-sensitive phase response recovery tests are respectively carried out on formaldehyde gas with the concentration of 1-5 ppm under the conditions of room temperature (26.3 ℃) and the relative humidity of 43% RH, so as to investigate the response and recovery performance of the sensing material to the formaldehyde gas, and the response results of the COFs-like materials of examples 1-5 to formaldehyde gas with different concentrations are shown in FIGS. 14-18. The test results show that the COFs material of example 1 has a response value of 32% to formaldehyde gas with a concentration of 1ppm, a response multiple of 1.35, response and recovery times of 45s and 7s respectively, and a response value of 86% to formaldehyde gas with a concentration of 5ppm, and response and recovery times of 32s and 9s respectively. Fitting shows that the response value to formaldehyde gas has good linear relation with the formaldehyde concentration. Meanwhile, the response multiples of the COFs materials of the embodiments 2-5 to formaldehyde gas with the concentration of 1ppm are 1.15, 1.25, 1.29 and 1.15 in sequence, and the linear relation between the response value to the formaldehyde gas and the formaldehyde concentration is good.

In addition, in order to better compare the room temperature sensing performance and the response recovery time of the COFs-like materials to formaldehyde gas with the same concentration, the formaldehyde sensing performance of the COFs-like materials of examples 1 to 5 at the concentration of 5ppm was respectively tested. As shown in fig. 19, the COFs-like materials of example 3 exhibited the highest formaldehyde response at a concentration of 5ppm, reaching a response value of 152%, and response and recovery times of 41s and 6s, respectively.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.