Photoresponsive charge transfer complex, and preparation method and application thereof

Abstract

The application is suitable for the technical field of volatile organic compounds treatment, and provides a light response type charge transfer complex as well as a preparation method and application thereof. The light response type charge transfer complex (EtP5-F4TCNQα) can efficiently adsorb toluene (Tol), and after adsorption, the toluene molecules can be triggered to be released rapidly by near-infrared laser irradiation, which avoids the dependence on heat source, pressure or chemical elution reagent in the traditional desorption, avoids the harsh conditions of high temperature and high pressure, significantly reduces the energy consumption and operation cost, and can effectively maintain the structural stability and recycling performance of the adsorption material. The whole desorption process does not need to introduce external chemicals, fundamentally eliminates secondary pollution, and realizes green and low-carbon operation. The application provides a green, efficient and simple-to-operate desorption regeneration new strategy, and has important engineering application value and environmental protection significance in the adsorption regeneration process in the fields of chemical separation, environmental governance and energy materials.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of volatile organic compounds treatment, and particularly relates to a light-responsive charge transfer complex as well as a preparation method and application thereof. BACKGROUND

[0002] In the field of volatile organic compounds treatment, the adsorption treatment of toluene mainly relies on two types of materials, namely activated carbon and zeolite molecular sieve. Among them, activated carbon has become the mainstream adsorbent for treating medium and high concentration toluene due to its developed pore structure and cost advantage; zeolite molecular sieve shows excellent performance in low concentration or humidity fluctuation conditions due to its regular crystal pore and controllable hydrophobicity. In industrial applications, the fixed bed adsorption process technology is mature and widely applicable, and has become one of the standard processes for waste gas purification in chemical, spraying and other industries.

[0003] In the industrial fields of chemical industry, environmental protection, energy and the like, the desorption regeneration process of the adsorption material is the core link for determining the cyclic use performance and economic benefits. The current desorption technology system widely used in the industry is mainly divided into three categories: thermal desorption technology, pressure desorption technology and chemical washing technology, each of which has its own characteristics and has formed a standardized application scheme. The thermal desorption technology, as the most traditional regeneration method, its principle is to destroy the action force between the adsorbate and the adsorbent by external heat source input. In specific implementation, high temperature steam or hot inert gas is usually used as the heat transfer medium to regenerate the adsorbent in a fixed bed or fluidized bed device; or a vacuum oven is directly used for activation. This technology is mature and widely used in the regeneration of various adsorption materials. The pressure desorption technology breaks the adsorption balance by changing the system pressure (such as pressure reduction or vacuum) to promote the desorption of the adsorbate from the adsorbent surface. The chemical washing technology changes the state of the adsorbate on the adsorbent by introducing chemical reagents to react with the adsorbate, so as to realize desorption and regeneration. This method usually uses solvent washing, acid-base treatment, oxidation-reduction or complexation reaction and other means to destroy the action force between the adsorbate and the adsorbent, or to convert the adsorbate into an easy-to-remove form, so as to achieve the purpose of desorption and material regeneration. These desorption technologies have developed relatively mature process routes and equipment systems through long-term industrial practice. In actual application, according to the properties of the adsorbate, the type of the adsorbent and the process requirements, appropriate desorption methods or combined application schemes of multiple technologies can be selected. With the progress of material science and process technology, these traditional desorption technologies are still being continuously optimized and improved.

[0004] However, the existing adsorption technology still has significant defects: the activated carbon is greatly affected by environmental humidity, the adsorption capacity sharply decreases under high temperature conditions, and the pore structure collapses after multiple regeneration, leading to irreversible decay of adsorption performance; zeolite molecular sieve faces problems of limited adsorption capacity under high concentration conditions, large mass transfer resistance and high raw material cost. In the desorption link, the traditional thermal desorption technology needs to consume a large amount of steam or electric energy, and has the problems of high energy consumption, incomplete desorption and secondary pollution risk; the pressure desorption technology needs to rely on high-pressure equipment, and is limited in application scenarios and has high equipment investment cost; the chemical elution technology is easy to pollute the adsorption material due to reagent residue, and needs additional treatment of elution waste liquid, further increasing the process cost and environmental protection pressure. The limitations of these materials and processes seriously restrict the economy and long-term operation stability of the toluene adsorption technology, and therefore it is necessary to develop an efficient and low-carbon adsorption-desorption integrated solution.

[0005] In view of the above technical bottlenecks, the present application provides a light-responsive charge transfer complex and a preparation method and application thereof. SUMMARY

[0006] The present application aims to provide a light-responsive charge transfer complex and a preparation method and application thereof, and aims to solve the problems raised in the above background.

[0007] The object of the present application is achieved by the following technical solutions:

[0008] A light-responsive charge transfer complex, with a pillar [5] arene as a host and 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyano dimethyl p-benzoquinone as a guest; the pillar [5] arene is an electron donor, the 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyano dimethyl p-benzoquinone is an electron acceptor, and the electron donor and the electron acceptor are combined by charge transfer interaction.

[0009] A preparation method of the light-responsive charge transfer complex, comprising the following steps:

[0010] Mixing the pillar [5] arene and the 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyano dimethyl p-benzoquinone, grinding in a agate mortar at room temperature until the color of the mixture changes to yellow brown, to obtain the light-responsive charge transfer complex.

[0011] Further, the molar ratio of the pillar [5] arene to the 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyano dimethyl p-benzoquinone is 1:2.

[0012] An application of the light-responsive charge transfer complex in toluene (Tol) adsorption, the light-responsive charge transfer complex is used as an adsorbent, and is contacted with toluene in a closed steam adsorption system to realize adsorption of toluene.

[0013] Further, the closed vapor adsorption system is constructed in a manner that 20 mg of the light-responsive charge transfer complex is placed in a 2 mL transparent glass bottle, and then the 2 mL transparent glass bottle is placed in a 20 mL clean glass sample bottle containing 200 μL of toluene, and after sealing, it is placed in a room temperature environment for adsorption.

[0014] An application of the light-responsive charge transfer complex in toluene photo-induced desorption according to the above-mentioned application, comprising the following steps:

[0015] Adsorption pretreatment: adsorbing toluene by the light-responsive charge transfer complex to form a complex after adsorbing toluene;

[0016] Photo-induced desorption: irradiating the complex after adsorbing toluene by near-infrared laser to realize desorption of toluene.

[0017] Further, the wavelength of the near-infrared laser is 808 nm, and the power density is 0.4 W / cm 2 .

[0018] Compared with the prior art, the application has the following beneficial effects:

[0019] The application provides a light-responsive charge transfer complex (EtP5-F4TCNQα), and innovatively provides a toluene adsorption-photo-induced desorption scheme based on the complex. The complex can efficiently adsorb toluene, and after adsorbing toluene, under irradiation of near-infrared laser of a specific wavelength, the complex can trigger rapid release of toluene molecules by exciting charge transfer effect of the light source, thereby breaking through the technical bottleneck of traditional desorption. The technology completely gets rid of the dependence of traditional desorption on heat source, pressure or chemical elution reagent, not only avoids harsh conditions of high temperature and high pressure, significantly reduces energy consumption and operation cost, but also effectively maintains the structural stability and recycling performance of the adsorption material. The whole desorption process does not need to introduce external chemicals, fundamentally eliminates secondary pollution, and realizes green and low-carbon operation. The application provides a green, efficient and simple-to-operate desorption regeneration new strategy, and has important engineering application value and environmental protection significance in the adsorption regeneration process in the fields of chemical separation, environmental governance and energy materials. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is the preparation process of the charge transfer complex.

[0021] Figure 2 It is a photo-induced toluene vapor desorption experiment.

[0022] Figure 3 It is the ultraviolet characterization of the preparation process of EtP5-F4TCNQα.

[0023] Figure 4XRD characterization of the preparation process of EtP5-F4TCNQα.

[0024] Figure 5 Infrared characterization of the preparation process of EtP5-F4TCNQα.

[0025] Figure 6 EtP5-F4TCNQα adsorbent saturated with toluene 1 H NMR.

[0026] Figure 7 The adsorption curve of toluene for EtP5-F4TCNQα is shown.

[0027] Figure 8 The UV and color changes of toluene adsorbed by EtP5-F4TCNQα.

[0028] Figure 9 XRD changes of toluene adsorbed on EtP5-F4TCNQα.

[0029] Figure 10 This is a crystal diagram of EtP5-F4TCNQ.

[0030] Figure 11 The crystal diagram of EtP5-F4TCNQ@Tol.

[0031] Figure 12 The toluene release curve of EtP5-F4TCNQα+Tol is shown.

[0032] Figure 13 XRD of toluene release of EtP5-F4TCNQα+Tol.

[0033] Figure 14 The color change of toluene release from EtP5-F4TCNQα+Tol.

[0034] Figure 15 UV characterization of toluene release from EtP5-F4TCNQα+Tol.

[0035] Figure 16 Toluene adsorption-desorption cycle stability test of EtP5-F4TCNQα. Detailed Implementation

[0036] To provide a clearer understanding of the technical features, objectives, and beneficial effects of this invention, the technical solution of this invention is described in detail below, but this should not be construed as limiting the scope of implementation of this invention. In this invention, materials, reagents, or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0037] The specific implementation of the present application is described in detail below in combination with specific examples.

[0038] The present application proposes an organic macrocyclic aromatic hydrocarbon-based charge transfer complex, which takes pillar[5]arene (EtP5) as the host and electron-deficient compound 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanoquinodimethane (F4TCNQ) as the guest, and is named as EtP5-F4TCNQα (the crystal grown in solution is EtP5-F4TCNQ). The complex can be used as an adsorbent for toluene adsorption (the charge transfer complex after adsorbing toluene is named as EtP5-F4TCNQα+Tol, and the crystal grown in solution is EtP5-F4TCNQ@Tol), and the related preparation, performance test and application process are as follows:

[0039] 1 Raw material preparation;

[0040] The EtP5 used in the present application is prepared according to the method in the prior art "Pillar[5,6]arene-Functionalized Silicon Dioxide: Synthesis, Characterization, and Adsorption of Herbicide", and the specific preparation process is not described here. The CAS number of F4TCNQ is 29261-33-4, which is purchased from Angene Chemical, and the item number is D0504030010.

[0041] 2 Preparation of charge transfer complex (EtP5-F4TCNQα);

[0042] The electron donor and the electron acceptor are mixed and ground in a molar ratio of 1:2 to form the charge transfer complex. The specific operation steps are as follows: EtP5 and F4TCNQ are mixed in a marquis mortar, and the mixture is ground with a pestle at room temperature until the color of the mixture changes obviously, indicating that the charge transfer complex has been formed. Among them, the white EtP5 and the yellow F4TCNQ form a yellow-brown mixed powder after grinding, which is the charge transfer complex EtP5-F4TCNQα (the preparation process is as shown in Figure 1 ).

[0043] 3 Adsorption performance test of EtP5-F4TCNQα;

[0044] Take 20 mg of EtP5-F4TCNQα sample and place it in a 2 mL transparent glass bottle. Then use a pipette to take 200 μL of toluene (Tol) solvent and inject it into the bottom of a 20 mL clean glass sample bottle. Place the 2 mL glass bottle containing the sample in the 20 mL glass bottle to form a closed vapor adsorption system, and place the system in a room temperature environment for the adsorption experiment. During the experiment, take samples at regular intervals, and test each equal amount of adsorbed sample by nuclear magnetic resonance hydrogen spectrum (H NMR) to quantitatively calculate the adsorption amount by the integral area of the characteristic peak. Finally, take the adsorption time as the horizontal coordinate and the adsorption amount as the vertical coordinate to obtain the complete adsorption kinetics curve. 1 H NMR) test, and the adsorption amount is quantitatively calculated by the integral area of the characteristic peak. Finally, take the adsorption time as the horizontal coordinate and the adsorption amount as the vertical coordinate to obtain the complete adsorption kinetics curve.

[0045] 4 Material property characterization of EtP5-F4TCNQα and EtP5-F4TCNQα+Tol;

[0046] To characterize the EtP5-F4TCNQα obtained after grinding and the EtP5-F4TCNQα+Tol obtained after adsorbing toluene, an ultraviolet-visible spectrophotometer is used to determine the ultraviolet-visible absorption spectrum of both, and a powder diffractometer is used for PXRD test to analyze whether the grinding process will change the crystal phase.

[0047] 5 Crystal growth of EtP5-F4TCNQ and EtP5-F4TCNQ@Tol;

[0048] Dissolve 5 mg of EtP5 in 2 mL of a saturated solution of F4TCNQ in chloroform, add 2 mL of methylcyclohexane, and let it stand at room temperature and evaporate the solvent to obtain a smooth block-shaped single crystal. Through single crystal X-ray diffraction analysis, the crystal structure of EtP5-F4TCNQ is obtained. Using the same method, dissolve 5 mg of EtP5 and F4TCNQ in 2 mL of a toluene saturated solution, and after evaporation at room temperature, obtain a block-shaped crystal. Select a suitable single crystal for X-ray diffraction test to obtain the crystal structure diagram of EtP5-F4TCNQ@Tol.

[0049] 6 Light-induced toluene vapor desorption experiment;

[0050] Take 50 mg of EtP5-F4TCNQα+Tol powder sample and evenly spread it on a clean quartz sheet (20 mm x 20 mm x 1 mm). Use an 808 nm near-infrared laser (output power density 0.4 W / cm 2 ) to vertically irradiate the sample surface, and adjust the spot diameter to cover the entire sample area (such as Figure 2The samples were irradiated with 808 nm laser (0.4 W / cm2) to release toluene, and then re-adsorbed with 200 μL fresh toluene in a closed container. The release-re-adsorption process was repeated for 5 cycles. The crystal structure of the sample was analyzed by powder XRD after each cycle, and the toluene content was determined by 1H NMR test.

[0051] 7 Cycling performance test;

[0052] Take 20 mg of EtP5-F4TCNQα+Tol powder, uniformly disperse it on a quartz substrate, irradiate it with an 808 nm laser (0.4 W / cm 2 ) to release toluene, and then re-adsorb it with 200 μL fresh toluene in a closed container, and repeat the release-re-adsorption process for 5 cycles. The crystal phase stability of the sample was analyzed by powder XRD after each cycle, and the toluene content was determined by 1H NMR test.

[0053] Example 1: Preparation of charge transfer complex based on organic macrocyclic aromatic hydrocarbon and study on toluene adsorption-photoinitiated desorption performance;

[0054] Preparation of EtP5-F4TCNQα:

[0055] During preparation, take 89.11 mg (0.1 mmol) of EtP5 and 55.23 mg (0.2 mmol) of F4TCNQ, mix them in a marble mortar, and grind the mixture with a pestle for 30 min at room temperature to obtain the charge transfer complex EtP5-F4TCNQα.

[0056] Structural characterization of EtP5-F4TCNQα:

[0057] Through UV-Vis absorption spectrum, the characteristic absorption band change caused by charge transfer (CT) interaction can be detected. When white EtP5 and yellow F4TCNQ are mixed and ground at a molar ratio of 1:2, a significant color change occurs, and a yellow-brown mixture powder is obtained. Solid-state UV-Vis absorption spectrum shows that EtP5-F4TCNQα has a clear absorption band in the near-infrared region (800-1200 nm), which is in sharp contrast to the absence of absorption band in the near-infrared region of single-component EtP5 and F4TCNQ ( Figure 3 ).

[0058] To explore the effect of mixing and grinding EtP5 and F4TCNQ on the crystal structure, PXRD test was carried out. From the PXRD graph, it can be seen that ( Figure 4 ), the PXRD spectrum of EtP5-F4TCNQα formed after mixing and grinding shows a clear peak overlap with the PXRD spectra of EtP5 and F4TCNQ, indicating the successful preparation of the charge transfer complex.

[0059] Fourier transform infrared spectroscopy analysis shows that Figure 5 ), the stretching vibration peak of cyano group (-CN) in EtP5-F4TCNQa has a 4 cm -1 red shift (from 2224 cm -1 to 2220 cm -1 ) compared with its precursor F4TCNQ. This red shift phenomenon can be attributed to the increased electron cloud density of cyano nitrogen atom caused by charge transfer interaction, which in turn weakens the bond force constant of -CN bond. This result strongly confirms the formation of effective charge transfer complex between EtP5 (electron donor) and F4TCNQ (electron acceptor).

[0060] Toluene adsorption performance test of EtP5-F4TCNQa:

[0061] The adsorption amount is quantitatively characterized and analyzed by nuclear magnetic resonance hydrogen spectrum technology Figure 6 . It can be seen from Figure 7 that the adsorption amount gradually increases with the extension of adsorption time, and after 8 hours of adsorption process, EtP5-F4TCNQa reaches the adsorption saturation state. Through standard curve calculation and spectrum peak area integration, the final saturated adsorption amount is determined to be 3.7 mol / EtP5-F4TCNQa, which reflects the maximum adsorption capacity of the charge transfer complex to toluene under this condition. After adsorbing toluene, the color of EtP5-F4TCNQa is macroscopically obviously changed from original yellow brown to red (forming EtP5-F4TCNQa+Tol). At the same time, this change can be further verified by ultraviolet-visible absorption spectrum analysis: in the near-infrared region of wavelength 800-1200 nm, the absorption intensity of EtP5-F4TCNQa+Tol is significantly enhanced compared with EtP5-F4TCNQa, which is consistent with the phenomenon that the macroscopic color of the material changes from yellow brown to red, indicating that toluene adsorption induces the change of electronic structure of EtP5-F4TCNQa, which in turn affects its light absorption behavior Figure 8 . In order to further explore the structural change of EtP5-F4TCNQa in toluene adsorption process, PXRD analysis is carried out on the sample after adsorption (EtP5-F4TCNQa+Tol), from Figure 9 which it can be seen that the PXRD spectrum of EtP5-F4TCNQa after adsorbing toluene is obviously changed in peak position and intensity compared with EtP5-F4TCNQa, and the peak position and intensity are almost consistent with the simulated PXRD of EtP5-F4TCNQa+Tol, which shows that EtP5-F4TCNQa has a structural reorganization in the adsorption process, and finally forms a new crystal phase structure (i.e. EtP5-F4TCNQaTol).

[0062] Investigation on the formation mechanism of EtP5-F4TCNQ host-guest interaction:

[0063] To further investigate the formation mechanism of this kind of host-guest interaction, EtP5-F4TCNQ crystals were grown in a mixed solution of chloroform and methylcyclohexane. Figure 10 From the crystal structure, EtP5 and F4TCNQ are stabilized by multiple non-covalent interactions, such as C–H···π interaction, π···π stacking and C–H···O hydrogen bond. By choosing toluene as the solvent, ternary co-crystals of EtP5, F4TCNQ and toluene (i.e. EtP5-F4TCNQ@Tol crystals) were successfully grown. Through subsequent crystal structure analysis, the intermolecular interactions existing in the co-crystal system were analyzed in detail. The structure shows that one F4TCNQ molecule is embedded between two EtP5 macrocycles, forming a sandwich structure; at the same time, two toluene molecules are wrapped in the cavity of EtP5, and another toluene molecule is mainly located outside the cavity; the entire supramolecular assembly is stabilized by rich weak interaction forces, mainly including C–H···π interaction, C–H···O hydrogen bond and C–H···F halogen bond, etc. multiple non-covalent interactions, which together maintain the stability of the EtP5-F4TCNQ@Tol crystal structure. Figure 11

[0064] Photoinitiated toluene desorption and cyclic performance test of EtP5-F4TCNQα:

[0065] To further investigate the release behavior of toluene in EtP5-F4TCNQα under light-induced conditions, systematic vapor desorption experiments were carried out. It can be seen from Figure 12 that within 1 min after the start of light, the amount of remaining toluene in EtP5-F4TCNQα+Tol is greatly reduced, and more than 50% of the adsorbed toluene has been rapidly released; by 10 min, toluene can be completely desorbed, which indicates that the charge transfer complex has high-efficiency light-responsive release properties. During the toluene desorption process, the crystal structure of EtP5-F4TCNQ@Tol gradually changes to that of the binary co-crystal of EtP5-F4TCNQ. Figure 13 With this structural change, the color of the material also changes significantly, from red to yellow-brown. Figure 14 This color change can be quantitatively monitored by ultraviolet-visible absorption spectroscopy (UV-Vis), from Figure 15 ​It can be seen that the absorption intensity in the near-infrared region of 800-1200 nm gradually increases with the increase of illumination time, indicating that the electronic structure of EtP5-F4TCNQα+Tol evolves (gradually recovers to the electronic structure of EtP5-F4TCNQα) during the desorption process; when the illumination time is 10 min, the absorption spectrum basically no longer changes, indicating that the desorption process tends to be completed (it has completely recovered to EtP5-F4TCNQα). In addition, the results of the cycle stability experiment show that (Fig. 6) Figure 16 ) After 5 consecutive adsorption-desorption cycles, the toluene adsorption capacity of EtP5-F4TCNQα does not decrease significantly, indicating that the charge transfer complex has good structural reversibility and cycle performance.

[0066] The above is only the preferred embodiment of the present application, it should be noted that for those skilled in the art, without departing from the concept of the present application, can also make a number of deformation and improvement, these should be considered as the protection scope of the present application, these will not affect the effect and practicality of the patent of the present application.

Claims

1. A photo-responsive charge transfer complex, characterized in that, A column pentaphenyl EtP5 is used as a host, and 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyano dimethyl-p-benzoquinone is used as a guest; the column pentaphenyl EtP5 is an electron donor, and 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyano dimethyl-p-benzoquinone is an electron acceptor, and the electron donor and the electron acceptor are combined through charge transfer interaction; The preparation method of the photoresponsive charge transfer complex comprises the following steps: The column pentaphenyl EtP5 is mixed with 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyano dimethyl-p-benzoquinone, and is ground in a agate mortar at room temperature until the color of the mixture turns to yellow brown, to obtain a photoresponsive charge transfer complex; The molar ratio of the column pentaphenyl EtP5 to 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyano dimethyl-p-benzoquinone is 1:2; The photoresponsive charge transfer complex has an XRD characterization graph as shown in Figure 4.

2. Use of the photoresponsive charge transfer complex according to claim 1 in toluene adsorption, characterized in that, The photoresponsive charge transfer complex is used as an adsorbent, is contacted with toluene in a closed vapor adsorption system, and toluene adsorption is realized.

3. Use according to claim 2, characterized in that, The closed vapor adsorption system is constructed in the following manner: 20 mg of the photoresponsive charge transfer complex is placed in a 2 mL transparent glass bottle, and then the 2 mL transparent glass bottle is placed in a 20 mL clean glass sample bottle containing 200 μL of toluene, and after being sealed, is placed in a room temperature environment for adsorption.

4. Use of the photoresponsive charge transfer complex according to claim 1 in toluene photo-induced desorption, characterized in that, The method comprises the following steps: Adsorption pretreatment: the photoresponsive charge transfer complex is used to adsorb toluene, to form a complex after adsorbing toluene; Photoinduced desorption: near-infrared laser is used to irradiate the complex after adsorbing toluene, to realize toluene desorption.

5. Use according to claim 4, characterized in that, The wavelength of the near-infrared laser is 808 nm, and the power density is 0.4 W / cm 2 .

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