CN108164549B - COFs material constructed based on flexible module and preparation method and application thereof - Google Patents
COFs material constructed based on flexible module and preparation method and application thereof Download PDFInfo
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Abstract
The invention belongs to the field of organic porous material adsorbents, and particularly relates to a COFs material constructed based on a flexible module, and a preparation method and application thereof. The invention provides a COFs material constructed based on a flexible module, which has a structure shown in a formula I. The invention also provides a preparation method of the COFs material constructed based on the flexible module and application of the COFs material as an iodine adsorbent. A series of COFs materials with large lattice sizes prepared by the flexible module show extremely high iodine enrichment capacity, and have great practical prospects in the fields of conventional enrichment and separation of radioactive iodine.
Description
Technical Field
The invention belongs to the field of organic porous material adsorbents, and particularly relates to a COFs material constructed based on a flexible module, and a preparation method and application thereof.
Background
Covalent Organic Frameworks (COFs) are a class of porous crystalline materials prepared from Organic molecular building blocks linked by Covalent bonds. COFs have the characteristics of large specific surface area, excellent chemical and biological stability, easy functional modification, highly ordered periodic sequences and the like, and have important application values in the aspects of gas storage, separation, catalysis, detection, optoelectronics, energy storage materials and the like. Despite the great progress made in the research of COFs during the last decade, especially in the last five years, there is still a great difficulty in how to simply and efficiently prepare COFs with regular structure and high crystallinity. In order to obtain a good crystal structure, relatively rigid monomer modules and a special bonding mode are generally selected for COFs, and bonded molecular chains are generally in a linear or nearly linear overall shape, such as boron-dioxy bonds, carbon-nitrogen double bonds, carbon-carbon double bonds, acetylene bonds and the like. The adoption of various flexible building modules for preparing the COFs creates the possibility of enriching the structural diversity and complexity of the COFs. Especially, the covalent organic framework material constructed based on the soft module has larger potential extensibility and more stacking modes because the flexible module has larger rotational freedom than the rigid monomer. However, it is also difficult to obtain regularly arranged spatial structures and high crystallinity of COFs prepared with flexible modules due to their large rotational freedom. Therefore, the construction of highly crystalline and novel covalent organic framework materials based on flexible modules remains a challenging research direction.
For practical application of the material, the high crystallinity and regular and ordered structural arrangement can greatly improve the application performance of the material in the fields of optics, electricity and the like. However, in many cases, good crystallinity does not necessarily mean good application properties, such as applications of the material in the fields of adsorption, separation, catalysis and the like. Therefore, how to effectively control the crystallinity of the covalent organic framework material and adjust the related application performance thereof is a research topic with great practical significance, and especially has more significance for COFs materials which have important development values, are constructed based on flexible modules and have large lattice sizes, and the research may bring unprecedented performance and application prospects to the COFs materials.
Iodine-129 is the most important radioactive contaminant in airborne radionuclide waste because of its extremely long radioactive half-life (1.57 × 10)7Year), volatility and biocompatibility, creating great hazards to the ecological environment and human health. Therefore, designing suitable materials for efficient capture and storage of iodine is critical to both public safety and nuclear safety. People are used to use natural or artificial molecular sieve and other inorganic composite material adsorbents as iodine adsorbentsThe adsorption capacity of the material to iodine is not ideal and the adsorption capacity is also low. The porous material has superior specific surface area and porosity and a more regular pore structure, and is one of the hot spots in the research of the iodine adsorbing material at present. Mainly comprising inorganic porous materials, metal organic framework Materials (MOFs) and Porous Organic Polymers (POPs). The loading rate of the inorganic porous material to iodine is usually between 8% and 175%, and is relatively low. Meanwhile, the application of the inorganic porous material in iodine capture is limited due to poor recycling capability of the inorganic porous material. The metal organic framework materials exhibit superior iodine uptake capacity than inorganic adsorption materials, however, due to their poor moisture and humidity stability and acid-base stability, MOFs materials are difficult to use for capture and storage of iodine in practical nuclear waste gases (containing large amounts of water vapor).
Disclosure of Invention
The invention provides a COFs material constructed based on a flexible module, which has a structure shown in a formula I:
wherein R is1、R2Independently is-H or-OH. Preferably, R1、R2Are all-H. Preferably, R1、R2Are all-OH.
The invention also provides a preparation method of the COFs material constructed based on the flexible module, which comprises the following steps:
a. preparation of 2,4, 6-tri-p-formylphenoxy-1, 3, 5-triazine: dissolving p-hydroxybenzaldehyde in a mixed solvent, adding alkali at 0-5 ℃, and stirring for 10-30 min; slowly dropwise adding an acetone-dissolved cyanuric chloride solution, and continuously reacting for 0.5-2 h at 0-5 ℃; then heating to reflux reaction for 1-5 h, naturally cooling, pouring the reacted solution into distilled water, filtering, washing the solid with an alkali solution, and drying in vacuum to obtain 2,4, 6-tri-p-formylphenoxy-1, 3, 5-triazine (TPT-CHO);
b. preparing COFs materials constructed based on flexible modules: and respectively carrying out ultrasonic treatment on the substituted benzidine and the mixed solvent, TPT-CHO and the mixed solvent for 2-10 min to respectively form uniform dispersion liquid, then slowly adding acetic acid into the TPT-CHO dispersion liquid, sealing, and standing and reacting for 2-5 days at 60-100 ℃ to obtain the COFs material constructed based on the flexible module.
In the above method for preparing COFs materials constructed based on flexible modules, the mixed solvent in step a is a mixed solvent of acetone and water; the volume ratio of the acetone to the water is 5: 1-1: 2.
In the above method for preparing COFs materials constructed based on flexible modules, the base is NaOH, KOH, CsOH, Ca (OH)2、Sr(OH)2Or Ba (OH)2Any one of the above; the molar ratio of the p-hydroxybenzaldehyde to the alkali is 1: 1-1: 2.
In the preparation method of the COFs material constructed based on the flexible module, the molar ratio of the p-hydroxybenzaldehyde to the cyanuric chloride in the step a is 5: 1-3: 1.
In the preparation method of the COFs material constructed based on the flexible module, the molar ratio of alkali to p-hydroxybenzaldehyde in the alkali solution in the step a is 3: 2-3: 1; the alkali solution is saturated NaHCO3Solution, 8-16% of Na2CO3Any one of a solution and a 5-10% NaOH solution.
In the above method for preparing COFs materials constructed based on flexible modules, the mixed solvent in step b is mesitylene (1,3, 5-trimethylbenzene)/dioxane solvent; the volume ratio of the mesitylene to the dioxane is 3: 1-1: 3.
In the preparation method of the COFs material constructed based on the flexible module, the molar ratio of the substituted benzidine in the step b to the TPT-CHO is 7: 4-6: 5.
In the preparation method of the COFs material constructed based on the flexible module, the concentration of the acetic acid in the step b is 5-15M; the molar ratio of acetic acid to TPT-CHO is 3: 1-15: 1.
The reaction formula of the preparation method of the COFs material constructed based on the flexible module is as follows:
wherein R is1、R2Independently is-H or-OH. Preferably, R1、R2Are all-H.
The invention also provides application of the COFs material constructed based on the flexible module as an iodine adsorbent.
The invention creatively uses a large flexible monomer containing triazine ring and ether bond as a building module to prepare the COFs material by adopting an aldehyde-amine condensation reaction. The in-situ nitrogen loading mode ensures that the product structure has abundant nitrogen atoms, thereby greatly increasing the iodine loading rate. Meanwhile, the prepared COFs material has good crystal form and large lattice size, which is very rare in the field of COFs constructed by flexible modules. According to the invention, through theoretical calculation and experimental research, the influence of the content of hydrogen bonds in the COFs material layer on the crystallinity and the iodine adsorption performance of the COFs constructed by the flexible module is deeply discussed for the first time, and the research finds that the hydrogen bonds reduce the rotational freedom of the construction unit and lock the partial structure of the COFs, so that the crystallinity of the material is effectively increased. Therefore, the control of the crystallinity of the COFs can be effectively realized by controlling the content of the hydrogen bonds in the system. However, the existence of hydrogen bonds also occupies a large number of adsorption active sites, so that the iodine capture performance of the material is obviously reduced. A series of COFs materials with large lattice sizes prepared by the flexible module show extremely high iodine enrichment capacity, the maximum adsorption quantity is up to 5.43g/g which is not reported, the COFs materials are the highest adsorption material in all types at present, and the characteristic makes the COFs materials have great practical prospect in the field of radioactive iodine enrichment in radioactive nuclear waste post-treatment.
Drawings
FIG. 1 shows the solid nuclear magnetic spectrum (a, b) and X-ray photoelectron spectrum (c, d) of the covalent organic framework materials TPT-BD COF (compound 1) and TPT-DHBD COF (compound 2) provided by the invention.
FIG. 2 powder X-ray diffraction patterns and material Studio computational simulation structures of covalent organic framework Materials TPT-BD COF (Compound 1) and TPT-DHBD COF (Compound 2) provided by the present invention.
FIG. 3 the covalent organic framework materials TPT-BD COF (Compound 1) and TPT-DHBD COF (Compound 2) provided by the present invention were dosed at a total dose of 105Gy is the infrared spectrogram before and after gamma ray irradiation.
FIG. 4 shows the adsorption time curves of compounds 1-5 to iodine.
FIG. 5 shows desorption curves of compounds 1 to 5 with respect to iodine.
FIG. 6 is an infrared spectrum of the covalent organic framework materials TPT-BD COF (Compound 1) and TPT-DHBD COF (Compound 2) and three reaction raw materials.
FIG. 7 is an infrared spectrum of compounds 1 to 5.
FIG. 8 is an infrared spectrum of the covalent organic framework material TPT-BD COF (Compound 1) of the present invention before and after adsorption of iodine.
FIG. 9 thermogravimetric curves before and after iodine adsorption of Compound 2(TPT-DHBD COF).
FIG. 10 Cyclic adsorption experiment of Compound 1(TPT-BD COF).
Detailed Description
The preparation method of the COFs material constructed based on the flexible module comprises the following steps:
a. preparation of 2,4, 6-tri-p-formylphenoxy-1, 3, 5-triazine: dissolving p-hydroxybenzaldehyde in a mixed solvent, adding alkali at 0-5 ℃, and stirring for 10-30 min; slowly dropwise adding an acetone-dissolved cyanuric chloride solution, and continuously reacting for 0.5-2 h at 0-5 ℃; then heating to reflux reaction for 1-5 h, naturally cooling, pouring the reacted solution into distilled water, filtering, washing the solid with an alkali solution, and drying in vacuum to obtain 2,4, 6-tri-p-formylphenoxy-1, 3, 5-triazine (TPT-CHO);
b. preparing COFs materials constructed based on flexible modules: and respectively carrying out ultrasonic treatment on the substituted benzidine and the mixed solvent, TPT-CHO and the mixed solvent for 2-10 min to respectively form uniform dispersion liquid, then slowly adding acetic acid into the TPT-CHO dispersion liquid, sealing, and standing and reacting for 2-5 days at 60-100 ℃ to obtain the COFs material constructed based on the flexible module.
In the above method for preparing COFs materials constructed based on flexible modules, the mixed solvent in step a is a mixed solvent of acetone and water; the volume ratio of the acetone to the water is 5: 1-1: 2.
In the above method for preparing COFs materials constructed based on flexible modules, the base is NaOH, KOH, CsOH, Ca (OH)2、Sr(OH)2Or Ba (OH)2Any one of the above; the molar ratio of the p-hydroxybenzaldehyde to the alkali is 1: 1-1: 2.
In the preparation method of the COFs material constructed based on the flexible module, the molar ratio of the p-hydroxybenzaldehyde to the cyanuric chloride in the step a is 5: 1-3: 1.
In the preparation method of the COFs material constructed based on the flexible module, the molar ratio of alkali to p-hydroxybenzaldehyde in the alkali solution in the step a is 3: 2-3: 1; the alkali solution is saturated NaHCO3Solution, 8-16% of Na2CO3Any one of a solution and a 5-10% NaOH solution.
In the above method for preparing COFs materials constructed based on flexible modules, the mixed solvent in step b is mesitylene (1,3, 5-trimethylbenzene)/dioxane solvent; the volume ratio of the mesitylene to the dioxane is 3: 1-1: 3.
In the preparation method of the COFs material constructed based on the flexible module, the molar ratio of the substituted benzidine in the step b to the TPT-CHO is 7: 4-6: 5.
In the preparation method of the COFs material constructed based on the flexible module, the concentration of the acetic acid in the step b is 5-15M; the molar ratio of acetic acid to TPT-CHO is 3: 1-15: 1.
EXAMPLE 12 preparation of 4, 6-Tri-p-formylphenoxy-1, 3, 5-triazine (TPT-CHO)
7.45g of p-hydroxybenzaldehyde was weighed out and dissolved in a mixed solvent of acetone and water (1:1v/v,100mL), 2.48g of NaOH was added under ice-bath conditions, and stirring was carried out for 30 min. 50mL of acetone-dissolved cyanuric chloride (3.68g) solution was slowly added dropwise to the reactor, stirred for 1 hour in an ice bath, refluxed for 2 hours at 80 ℃ and cooled naturally. Dissolving after reactionThe solution was poured into 300mL of distilled water to form a large amount of white solid. Filtering, and adding 10% Na to the solid2CO3Washing the solution for 2-3 times, and drying in vacuum. The obtained white solid powder was recrystallized from ethyl acetate to obtain TPT-CHO as a white crystalline powder with a yield of 88.9%.
1H NMR(400MHz,CDCl3):9.99(s,3H),7.92(d,J＝8.7Hz,6H),7.32(d,J＝8.5Hz,6H)。
Example 2 preparation of a covalent organic framework Material TPT-BD COF (Compound 1)
2,4, 6-Tri-p-formylphenoxy-1, 3, 5-triazine (TPT-CHO) (88.4mg, 0.2mmol) and Benzidine (BD) (55.2mg, 0.3mmol) were weighed into 10mL glass vials, and the solvents mesitylene/dioxane (1:1v/v, 1mL) were added each and sonicated for 5min to form a uniform dispersion. The TPT-CHO dispersion was then added to the 3,3' -dihydroxybenzidine dispersion, followed by the final slow addition of acetic acid (6M, 0.2mL), sealing, and standing at 85 ℃ for 4d to afford the product as a yellow crystalline solid in 61.3% yield. Molecular formula ((C)14H9N2O)n) Elemental analysis (% calculated/measured): c76.01/72.80, H4.10/4.35, N12.66/11.36, O7.23/11.49).
Example 3 preparation of the covalent organic framework Material TPT-DHBD COF (Compound 2)
2,4, 6-Tri-p-formylphenoxy-1, 3, 5-triazine (TPT-CHO) (88.4mg, 0.2mmol) and 3,3' -dihydroxybenzidine (DHBD) (64.8mg, 0.3mmol) were weighed into 10mL glass vials, and the solvent mesitylene/dioxane (1:1v/v, 1mL) was added each, and sonicated for 8min to form a uniform dispersion. The TPT-CHO dispersion was then added to the 3,3' -dihydroxybenzidine dispersion, followed by the final slow addition of acetic acid (6M, 0.3mL), sealing, and standing at 70 ℃ for 5d to obtain a yellow crystalline solid product in 62.5% yield. Molecular formula((C14H9N2O2)n) Elemental analysis (% calculated/measured): c70.87/65.46, H3.83/4.05, N11.81/9.87, O13.49/20.62).
From the analysis of FIGS. 1a and b, a characteristic formant of a sharp imino carbon appears at 154ppm in the spectrum of TPT-BD COF and TPT-DHBD COF, which confirms the existence of the imino bond in the material structure. Fig. 1C, d is N1 s core layer spectrum measured by X-ray photoelectron spectroscopy (XPS), peaks of TPT-BD COF (compound 1) and TPT-DHBD COF (compound 2) at the binding energy of 399.4eV, 398.7eV, 399.4eV and 399.0eV respectively belong to peaks of C ═ N bond and imine bond of triazine ring, only two peaks are present in the spectrum, and the areas are substantially the same, which shows that only triazine ring nitrogen atom and imine nitrogen atom are present in the material, the ratio is 1:1, and matches with the structure. Thus, the present invention successfully prepares COFs material combined by aldehyde-amine condensation.
Example 4 covalent organic framework Material TPT-DHBD25Preparation of COF (Compound 3)
Benzidine (BD) (82.8mg, 0.45mmol) and 3,3' -dihydroxybenzidine (DHBD) (32.4mg, 0.15mmol) were placed in a 20mL glass pressure bottle, 2mL mesitylene/dioxane (1:1v/v) mixed solvent was added, and sonication was performed for 8min to form a uniform dispersion. The monomer 2,4, 6-tri-p-formylphenoxy-1, 3, 5-triazine (TPT-CHO) (176.8mg, 0.4mmol) was dispersed in 2mL mesitylene/dioxane (1:1v/v) to form a uniform dispersion. The TPT-CHO dispersion was then transferred to a pressure bottle, sonicated for 20s and mixed, followed by slow addition of acetic acid (6M, 0.6mL), sealed, and allowed to stand at 90 ℃ for 3d to afford a yellow crystalline solid product in 59.8% yield. Molecular formula ((C)56H36N8O5)n) Elemental analysis (% calculated/measured): c74.66/71.19, H4.03/4.46, N12.44/11.21, O8.88/13.14).
Example 5 covalent organic framework Material TPT-DHBD50Preparation of COF (Compound 4)
Benzidine (BD) (55.2mg, 0.3mmol) and 3,3' -dihydroxybenzidine (DHBD) (64.8mg, 0.3mmol) were placed in a 20mL glass pressure bottle, and 2mL mesitylene/dioxane (1:1v/v) mixed solution was addedAnd (5) carrying out ultrasonic treatment for 5min to form a uniform dispersion liquid. The monomer 2,4, 6-tri-p-formylphenoxy-1, 3, 5-triazine (TPT-CHO) (176.8mg, 0.4mmol) was dispersed in 2mL mesitylene/dioxane (1:1v/v) to form a uniform dispersion. The TPT-CHO dispersion was then transferred to a pressure bottle, sonicated for 20s and mixed, followed by slow addition of acetic acid (6M, 0.4mL), sealed, and allowed to stand at 80 ℃ for 4d to afford a yellow crystalline solid product in 78.4% yield. Molecular formula ((C)56H36N8O6)n) Elemental analysis (% calculated/measured): c73.35/69.34, H3.96/4.27, N12.22/10.87, O10.47/15.52).
Example 6 covalent organic framework Material TPT-DHBD75Preparation of COF (Compound 5)
Benzidine (BD) (27.6mg, 0.15mmol) and 3,3' -dihydroxybenzidine (DHBD) (97.2mg, 0.45mmol) were placed in a 20mL glass pressure bottle, 2mL mesitylene/dioxane (1:1v/v) mixed solvent was added, and sonication was performed for 6min to form a uniform dispersion. The monomer 2,4, 6-tri-p-formylphenoxy-1, 3, 5-triazine (TPT-CHO) (176.8mg, 0.4mmol) was dispersed in 2mL mesitylene/dioxane (1:1v/v) to form a uniform dispersion. The TPT-CHO dispersion was then transferred to a pressure bottle, sonicated for 20s and mixed, followed by slow addition of acetic acid (6M, 0.5mL), sealed, and allowed to stand at 75 ℃ for 5d to give a yellow crystalline solid product in 68.7% yield. Molecular formula ((C)56H36N8O7)n) Elemental analysis (% calculated/measured): c72.10/67.29, H3.89/4.21, N12.01/10.87, O12.00/17.63).
Example 7 powder X-ray diffraction (PXRD) and theoretical simulation experiments for Compound 1 and Compound 2
Powder X-ray diffraction (PXRD) is one of the main characterization methods for the structure of crystalline materials. Since the PXRD main diffraction peak of most COF materials appears in the range of 2-5 degrees at 2 theta, the test range of the X-ray diffractometer adopted by the invention is 2-40 degrees. And determining the exact structures of the materials TPT-BD COF and TPT-DHBD COF by adopting a comparison study of PXRD experimental test values and theoretical simulation values.
PXRD showed that TPT-DHBD COF (compound 1) had a number of distinct diffraction peaks (fig. 2a), the major diffraction peak of which was caused by the (100) plane, located at 2.27 °. The other clearly visible peaks are located at 4.07 °, 4.69 °, 6.22 °, 8.13 °, 10.18 ° 2 θ, respectively due to the (110), (200), (210), (220), (xxx) crystal planes.
The crystal structure of TPT-DHBD COF (compound 2) was simulated using Materials Studio 7.0 software, and the results showed that the simulated PXRD pattern was similar to the experimental values in AA stacking. Cell parameters of Pawley refinement are
α - β -90 °, and γ -120 °, correlation coefficient RP2.80% and RWP3.91%. The Pawley refined value can be well matched with an experimental observed value. The material TPT-BD COF has more distinct diffraction peaks at 2 θ of 2.27, 4.03, 4.53, 6.16, 8.12 ° (fig. 2b), which are generated by (100), (110), (200), (210), (220) crystal planes, respectively. The structural simulation shows that the diffraction peak of each crystal face of the experimental value is basically the same as the AA stacking mode, and the cell parameter refined by Pawley is
α - β -120 °, γ -120 °, and the correlation coefficient is RP4.48% and RWP6.11%. PXRD comparison shows that the XRD diffraction peak intensity of TPT-DHBD COF is high, the pattern is slightly interfered by a base line, while the (100) diffraction peak intensity of TPT-BD COF is weak, the pattern is seriously interfered by the base line, and a strong amorphous peak appears near a 2 theta of 21.5 degrees. It is shown that TPT-DHBD COF has better crystallinity than TPT-BD COF, which is probably due to the formation of hydrogen bonds in TPT-DHBD COF.
EXAMPLE 8 Gamma ray irradiation experiment of Compound 1 and Compound 2
According to the designed structure, the series of covalent organic framework materials TPT-DHBD prepared by the inventionXCOFs have nitrogen-rich structures (C ═ N) and rich pi-pi conjugated systems, a structural property that provides many for their interaction with iodineIt is possible. In order to examine the stability of a material against radiation in a possible real application environment, the invention makes use of60Co gamma radiation source A total dose of 10 was applied to Compound 1 and Compound 25Gy gamma ray irradiation and comparison of infrared spectrograms before and after irradiation show the irradiation stability of the material.
The IR spectrum of FIG. 3 shows that the material has little change before and after irradiation, indicating that the material has good radiation stability and can withstand a total dose of at least 105Irradiation of Gy gamma rays. This indicates capture of radioiodine by the prepared covalent organic framework materials (e.g.129I and131I) the field has potential application value. In addition, the prepared material also has better thermal stability, particularly TPT-BD COF (compound 1), and only loses 7 percent of weight when the temperature is 25-400 ℃. The preparation material is therefore very suitable for adsorption-desorption applications of iodine vapor in practical environments.
Example 9 adsorption experiment of Compounds 1-5 to iodine
To evaluate the enrichment capacity of the material for iodine vapor, the prepared compound 1-5 powder was exposed to a closed system containing excess iodine at a temperature of 75 ℃ and at an ambient pressure, which is close to a typical nuclear fuel reprocessing environment. The adsorption capacity of the material for iodine at different adsorption times was determined gravimetrically. The specific operation is as follows: 10mg of the adsorbent powder was placed in a 2mL open glass tube, and the glass tube was placed in a glass vial containing 500mg of iodine, sealed, and subjected to adsorption experiments at 75 ℃ under normal pressure. Taking out the sample after a period of time (0-48h), cooling and weighing, and calculating the adsorption capacity of the sample at different times. The adsorption capacity of the adsorbent for iodine was calculated by the increase in weight: cu＝(W2-W1)/W1× 100 wt% of CuIs the adsorption capacity, W1,W2Is the mass of the material before and after adsorption of iodine vapor.
The results in fig. 4 show that the adsorption capacity increases very rapidly in an almost linear trend, reaching more than 70% of the total adsorption, within the first 6 h; when the reaction time reaches 12h, the adsorption is basically approachedBalancing; after the adsorption time exceeded 32h, the iodine loading was almost unchanged, indicating that the adsorption had reached equilibrium. During the adsorption process, the color of the material is continuously deepened and finally gradually changed from yellow to dark black, and the material after adsorbing iodine is represented as TPT-DHBDXCOFs@I2. From the adsorption curve we can see that the rates of the front and back stages of adsorption are very different, which indicates that the iodine enrichment is a combined action of chemisorption and physisorption. The adsorption kinetics research finds that chemical adsorption is a main action mode and has faster adsorption kinetics. Under such conditions, 1g of the compound 1-5 materials can adsorb iodine in amounts of about 5.43g/g, 3.88g/g, 4.63g/g, 4.30g/g, and 4.12g/g, respectively. Therefore, the series of materials of the compounds 1-5 have ultrahigh iodine saturation adsorption capacity, particularly the enrichment amount of the TPT-BD COF (compound 1) to iodine can reach 5.43g/g at most, and is higher than all reported adsorption materials, such as MOFs, amorpausPOPs and other COFs materials. More importantly, the prepared gram-magnitude TPT-DHBD COF (compound 2) can still enrich iodine by 4.03g/g, so that conditions are created for large-scale production and practical application of the material, and the material has great potential application value in the fields of enrichment and removal of radioactive iodine in specific environments such as nuclear accident sites and the like.
The infrared spectrum analysis of FIG. 8 shows that the peak of the material before and after iodine adsorption is greatly shifted, for example, C-C bond and C-H bond in benzene ring of TPT-BD COF are positioned at 1499cm-1And 815cm-1Where, move to 1492cm-1、805cm-1(ii) a The C ═ N double bond of the triazine ring is 1566cm-1And 1363cm-1Moved to 1562cm-1And 1359cm-1(ii) a Especially the peak of imine bond, from 1622cm-1Move to 1631cm-1There is a great variation. The other materials all have similar laws, which indicate that iodine adsorption may simultaneously occur on imine bonds, triazine rings and benzene rings of the materials.
Example 10 Desorption experiment of iodine with Compounds 1 to 5
The iodine desorption experiment was carried out at 125 ℃ (fig. 5) and the procedure was as follows: 30mg of the iodine vapor-adsorbed TPT-DHBDXCOFs@I2Placed in a 2mL open glass tube and placed in an open glass vial (50mL) for desorption experiments at 125 ℃ under atmospheric pressure. The desorption efficiency of iodine is Er ═ 30-Wt)/WX× 100 Wt%, where Er represents desorption efficiency and Wt represents TPT-DHBD at corresponding time (0-420min)XCOFs@I2Mass after heat release, WXRepresents 30mg of TPT-DHBDXCOFs@I2The content of iodine in the product.
Experiments show that all materials can release more than 80% of iodine within 40min, and the desorption rate is higher. After 6h, the desorption reached essentially equilibrium and almost all the iodine was desorbed (see table 1). The iodine loadings of TPT-DHBD COF (Compound 2) were calculated by TGA characterization (FIG. 9) and were 4.77g/g (400 deg.C), 4.24g/g (350 deg.C), 3.77g/g (250 deg.C), respectively, and the results were essentially consistent with the gravimetrically determined values, with a small difference probably due to incomplete release of some of the iodine at the calculated iodine loading temperature. The reusability experiments showed that TPT-BD COF (compound 1) can maintain 515 wt% iodine adsorption capacity (up to 96% recovery) after the first cycle is completed. After the third cycle, it still retained 472 wt% iodine adsorption capacity (87.9% recovery) (fig. 10). Therefore, the adsorption of the COF series materials prepared by the invention to iodine vapor is an efficient and reversible process, and the COF series materials have great operability in the aspects of enrichment and storage of volatile iodine.
TABLE 1 desorption amount of iodine with time table (125 ℃ C.)
A series of COFs materials with large lattice sizes prepared by the flexible module show extremely high iodine enrichment capacity, the maximum adsorption quantity is up to 5.43g/g which is not reported, the COFs materials are the highest adsorption material in all types at present, and the characteristic makes the COFs materials have great practical prospect in the field of radioactive iodine enrichment in radioactive nuclear waste post-treatment.
Claims (4)
1. The COFs material constructed based on the flexible module has a structure shown in a formula I:
wherein R is1、R2Independently is-H or-OH.
2. The COFs materials constructed based on flexible modules according to claim 1, wherein: r1、R2Are all-H.
3. The COFs materials constructed based on flexible modules according to claim 1, wherein: r1、R2Are all-OH.
4. Use of the COFs material constructed based on flexible modules as claimed in claim 1 to 3 as an iodine adsorbent.
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| CN109251285B (en) * | 2018-09-21 | 2021-07-27 | 台州学院 | Conjugated microporous polymer based on chlorinated 1,3, 5-tri (4-aldehyde pyridyl) triazine and preparation method thereof |
| CN109265657B (en) * | 2018-09-21 | 2021-02-05 | 台州学院 | Conjugated microporous polymer based on symmetric indacene-1, 3,5,7(2H,6H) -tetraone and preparation method thereof |
| CN109603764A (en) * | 2019-01-24 | 2019-04-12 | 浙江师范大学 | A kind of organic functional material and preparation method thereof and the application in iodine absorption |
| CN110544544B (en) * | 2019-09-25 | 2021-07-30 | 中国原子能科学研究院 | Device and method for continuously generating iodine steam |
| CN112090413B (en) * | 2020-08-24 | 2021-09-07 | 四川大学 | Quasi-three-dimensional phosphazene covalent organic framework material and preparation method and application thereof |
| CN112250883B (en) * | 2020-10-30 | 2022-01-28 | 武汉大学 | Covalent organic framework material with respiration effect, preparation method and application thereof |
| CN113351186B (en) * | 2021-06-18 | 2022-12-27 | 海南希源化工科技有限公司 | Preparation method of iodine adsorbent, obtained product and application |
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