Photoresponse type charge transfer compound and preparation method and application thereof

Abstract

The invention is applicable to the technical field of volatile organic compound treatment, and provides a photoresponse type charge transfer compound as well as a preparation method and application thereof. The photoresponse type charge transfer compound (EtP5-F4TCNQ alpha) can efficiently adsorb toluene (Tol), after adsorption, toluene molecules can be triggered to be rapidly released through near-infrared laser irradiation, dependence of traditional desorption on a heat source, pressure or a chemical elution reagent is avoided, harsh conditions of high temperature and high pressure are avoided, energy consumption and operation cost are remarkably reduced, and the method is suitable for industrial production. The structural stability and the recycling performance of the adsorption material can be effectively maintained. External chemical substances do not need to be introduced in the whole desorption process, so that secondary pollution is fundamentally avoided, and green and low-carbon operation is realized. The invention provides a new green, efficient and easy-to-operate desorption regeneration strategy, shows wide application prospects in the adsorption regeneration process in the fields of chemical separation, environmental governance, energy materials and the like, and has important engineering application value and environmental protection significance.

Description

Technical Field

[0001] This invention belongs to the field of volatile organic compound treatment technology, and particularly relates to a photoresponsive charge transfer complex, its preparation method and application. Background Technology

[0002] In the field of volatile organic compound (VOC) treatment, the adsorption and treatment of toluene mainly relies on two types of materials: activated carbon and zeolite molecular sieves. Activated carbon, with its well-developed pore structure and cost advantage, has become the mainstream adsorbent for treating medium to high concentrations of toluene. Zeolite molecular sieves, due to their regular crystal channels and tunable hydrophobic properties, exhibit excellent performance under low concentration or humidity fluctuation conditions. In industrial applications, fixed-bed adsorption technology is mature and widely applicable, and has become one of the standard processes for waste gas purification in industries such as chemical engineering and spraying.

[0003] In industrial fields such as chemical engineering, environmental protection, and energy, the desorption and regeneration process of adsorbent materials is a core element determining their recyclability and economic benefits. Currently, the desorption technologies commonly used in industry are mainly divided into three categories: thermal desorption, pressure desorption, and chemical elution. Each type of technology has its own characteristics and has formed standardized application schemes. Thermal desorption, as the most traditional regeneration method, works by using an external heat source to disrupt the interaction forces between the adsorbate and the adsorbent. In practice, high-temperature steam or thermal inert gas is typically used as the heat transfer medium to regenerate the adsorbent in a fixed-bed or fluidized-bed device; alternatively, a vacuum oven can be used for direct activation. This technology is mature and widely used in the regeneration of various adsorbent materials. Pressure desorption technology breaks the adsorption equilibrium by changing the system pressure (such as depressurization or vacuuming), causing the adsorbate to desorb from the adsorbent surface. Chemical elution technology introduces chemical reagents to react with the adsorbate, changing its state on the adsorbent and thus achieving desorption and regeneration. This method typically utilizes solvent elution, acid-base treatment, redox reactions, or complexation reactions to disrupt the interaction between the adsorbate and adsorbent, or to convert the adsorbate into an easily removable form, thereby achieving desorption and material regeneration. These desorption technologies have evolved into relatively mature process routes and equipment systems through long-term industrial practice. In practical applications, depending on the properties of the adsorbate, the type of adsorbent, and the process requirements, appropriate desorption methods or combinations of multiple technologies can be selected. With advancements in materials science and process technology, these traditional desorption technologies continue to be optimized and improved.

[0004] However, existing adsorption technologies still have significant drawbacks: activated carbon is greatly affected by ambient humidity, its adsorption capacity drops sharply under high temperatures, and it is prone to pore structure collapse after multiple regenerations, leading to irreversible degradation of adsorption performance; zeolite molecular sieves face problems such as limited adsorption capacity under high concentration conditions, high mass transfer resistance, and high raw material costs. In the desorption process, traditional thermal desorption technology consumes a large amount of steam or electricity, resulting in high energy consumption, incomplete desorption, and the risk of secondary pollution; pressure desorption technology relies on high-pressure equipment, limiting its applicability and incurring high equipment investment costs; chemical elution technology is prone to contaminating adsorption materials due to reagent residues and requires additional treatment of elution wastewater, further increasing process costs and environmental pressure. These limitations of materials and processes severely restrict the economic viability and long-term operational stability of toluene adsorption technology, thus necessitating the development of efficient and low-carbon integrated adsorption-desorption solutions.

[0005] To address the aforementioned technical bottlenecks, this invention proposes a photoresponsive charge transfer composite, its preparation method, and its applications. Summary of the Invention

[0006] The purpose of this invention is to provide a photoresponsive charge transfer composite, its preparation method, and its application, in order to solve the problems mentioned in the background art.

[0007] The objective of this invention is achieved through the following technical solution: A photoresponsive charge-transfer complex is based on a columnar pentaaryl aromatic hydrocarbon and a 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone guest compound. The columnar pentaaryl aromatic hydrocarbon is an electron donor, and the 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone is an electron acceptor. The electron donor and electron acceptor are bound together through charge-transfer interactions.

[0008] A method for preparing the photoresponsive charge transfer complex according to the above-described method includes the following steps: The pentane aromatic hydrocarbon was mixed with 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone and placed in an agate mortar. The mixture was ground at room temperature until the color of the mixture turned yellowish-brown, thus obtaining a photoresponsive charge transfer complex.

[0009] Furthermore, the molar ratio of the columnar pentaaryl aromatic hydrocarbon to 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone is 1:2.

[0010] An application of the photoresponsive charge transfer complex described above in the adsorption of toluene (Tol) involves using the photoresponsive charge transfer complex as an adsorbent in a closed vapor adsorption system to contact toluene and achieve toluene adsorption.

[0011] Furthermore, the closed vapor adsorption system is constructed as follows: 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. After sealing, the system is placed in a room temperature environment for adsorption.

[0012] An application of the photoresponsive charge transfer complex described above in toluene photoinduced desorption includes the following steps: Adsorption pretreatment: The photoresponsive charge transfer complex adsorbs toluene, forming a complex after toluene adsorption; Photoinduced desorption: The toluene-adsorbed complex is irradiated with a near-infrared laser to achieve toluene desorption.

[0013] Furthermore, the near-infrared laser has a wavelength of 808 nm and a power density of 0.4 W / cm². 2 .

[0014] Compared with the prior art, the beneficial effects of the present invention are: This invention provides a photoresponsive charge-transfer complex (EtP5-F4TCNQα) and innovatively proposes a toluene adsorption-photoinduced desorption scheme based on this complex. This complex can efficiently adsorb toluene, and after adsorption, under near-infrared laser irradiation of a specific wavelength, it can trigger the rapid release of toluene molecules through a charge-transfer effect induced by the light source, breaking through the technical bottleneck of traditional desorption. This technology completely eliminates the dependence of traditional desorption on heat sources, pressure, or chemical eluents, avoiding harsh conditions of high temperature and high pressure, significantly reducing energy consumption and operating costs, and effectively maintaining the structural stability and recyclability of the adsorbent material. The entire desorption process does not require the introduction of external chemical substances, fundamentally eliminating secondary pollution and achieving green and low-carbon operation. This invention provides a green, efficient, and easy-to-operate new desorption and regeneration strategy, showing broad application prospects in adsorption and regeneration processes in chemical separation, environmental remediation, and energy materials, and has significant engineering application value and environmental significance. Attached Figure Description

[0015] Figure 1 This describes the preparation process of the charge transfer complex.

[0016] Figure 2 This is a photo-induced toluene vapor desorption experiment.

[0017] Figure 3 UV characterization of the preparation process of EtP5-F4TCNQα.

[0018] Figure 4 XRD characterization of the preparation process of EtP5-F4TCNQα.

[0019] Figure 5 Infrared characterization of the preparation process of EtP5-F4TCNQα.

[0020] Figure 6 EtP5-F4TCNQα adsorbent saturated with toluene 1 H NMR.

[0021] Figure 7 The adsorption curve of toluene for EtP5-F4TCNQα is shown.

[0022] Figure 8 The UV and color changes of toluene adsorbed by EtP5-F4TCNQα.

[0023] Figure 9 XRD changes of toluene adsorbed on EtP5-F4TCNQα.

[0024] Figure 10 This is a crystal diagram of EtP5-F4TCNQ.

[0025] Figure 11 The crystal diagram of EtP5-F4TCNQ@Tol.

[0026] Figure 12 The toluene release curve of EtP5-F4TCNQα+Tol is shown.

[0027] Figure 13 XRD of toluene release of EtP5-F4TCNQα+Tol.

[0028] Figure 14 The color change of toluene release from EtP5-F4TCNQα+Tol.

[0029] Figure 15 UV characterization of toluene release from EtP5-F4TCNQα+Tol.

[0030] Figure 16 Toluene adsorption-desorption cycle stability test of EtP5-F4TCNQα. Detailed Implementation

[0031] 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.

[0032] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0033] This invention proposes a charge-transfer complex based on macrocyclic aromatic hydrocarbons (MARHs). The complex uses pentacyclic aromatic hydrocarbon (EtP5) as the host and the electron-deficient compound 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone (F4TCNQ) as the guest, named EtP5-F4TCNQα (the crystals grown in solution are EtP5-F4TCNQ). This complex can be used as an adsorbent for toluene adsorption (the toluene adsorbed by the charge-transfer complex is named EtP5-F4TCNQα+Tol, and the crystals grown in solution are EtP5-F4TCNQ@Tol). The relevant preparation, performance testing, and application procedures are as follows: 1. Raw material preparation; The EtP5 used in this invention was prepared according to the method described in the prior art "Pillar[5,6]arene-Functionalized SiliconDioxide: Synthesis, Characterization, and Adsorption of Herbicide", and the specific preparation process will not be repeated here. The CAS number of F4TCNQ is 29261-33-4, purchased from Anaiji Chemical, catalog number D0504030010.

[0034] 2. Preparation of the charge transfer complex (EtP5-F4TCNQα); Using EtP5 as the electron donor and F4TCNQ as the electron acceptor, a charge transfer complex is formed by mixing and grinding the electron donor and acceptor at a molar ratio of 1:2. The specific steps are as follows: EtP5 and F4TCNQ are mixed in an agate mortar and ground thoroughly with a pestle at room temperature until a significant color change occurs, indicating the formation of the charge transfer complex. The white EtP5 and yellow F4TCNQ, after grinding, form a yellowish-brown mixed powder, which is the charge transfer complex EtP5-F4TCNQα (preparation process as follows). Figure 1 (As shown).

[0035] 3. Adsorption performance test of EtP5-F4TCNQα; Weigh 20 mg of EtP5-F4TCNQα sample and place it in a 2 mL transparent glass bottle. Then, pipette 200 μL of toluene (Tol) solvent and inject it into the bottom of the 20 mL clean glass sample bottle. Place the 2 mL glass bottle containing the sample into the 20 mL glass bottle to form a closed vapor adsorption system. Place this system at room temperature for the adsorption experiment. During the experiment, samples are taken at regular intervals, and equal amounts of adsorbed samples are subjected to 1H NMR spectroscopy (1H NMR spectroscopy). 1The adsorption amount was quantitatively calculated by using ¹H NMR (hydrogen spectroscopy) analysis and the integral area of ​​characteristic peaks. Finally, a complete adsorption kinetic curve was obtained by plotting adsorption time on the x-axis and adsorption amount on the y-axis.

[0036] 4. Material property characterization of EtP5-F4TCNQα and EtP5-F4TCNQα+Tol; To characterize EtP5-F4TCNQα obtained after grinding and EtP5-F4TCNQα+Tol obtained after toluene adsorption, the UV-Vis absorption spectra of both were measured using a UV-Vis spectrophotometer, and PXRD tests were performed using a powder diffractometer to analyze whether the grinding process would cause changes in the crystal phase.

[0037] 5. Crystal growth of EtP5-F4TCNQ and EtP5-F4TCNQ@Tol; 5 mg of EtP5 was dissolved in 2 mL of a saturated chloroform solution containing F4TCNQ, and 2 mL of methylcyclohexane was added. The solution was allowed to stand at room temperature to evaporate the solvent, resulting in a smooth, bulk single crystal. The crystal structure of EtP5-F4TCNQ was determined by single-crystal X-ray diffraction analysis. Using the same method, 5 mg of EtP5 and F4TCNQ were dissolved in 2 mL of a saturated toluene solution. After evaporation at room temperature, bulk crystals were obtained. X-ray diffraction tests were performed on suitable single crystals to obtain the crystal structure diagram of EtP5-F4TCNQ@Tol.

[0038] 6. Photoinduced toluene vapor desorption experiment; Weigh 50 mg of EtP5-F4TCNQα+Tol powder sample and spread it evenly on a clean quartz plate (20 mm × 20 mm × 1 mm). Use an 808 nm near-infrared laser (output power density 0.4 W / cm²). 2 The light is irradiated vertically onto the sample surface, and the spot diameter is adjusted to cover the entire sample area (e.g., ...). Figure 2 (As shown). During continuous irradiation, samples were taken at regular intervals, and changes in the crystal structure of the samples were monitored by powder X-ray diffraction (PXRD); at the same time, changes in the toluene content in the samples were analyzed by measuring the changes in the integral area of ​​the characteristic peaks, combined with nuclear magnetic resonance hydrogen spectroscopy.

[0039] 7. Cyclic performance test; Take 20 mg of EtP5-F4TCNQα+Tol powder, disperse it evenly on a quartz substrate, and use an 808 nm laser (0.4 W / cm²) to perform the reaction. 2 Toluene was released by irradiation, followed by re-adsorption with 200 μL of fresh toluene in a sealed container. This release-re-adsorption process was repeated 5 times. After each cycle, the crystal phase stability of the sample was analyzed by powder XRD, and the toluene content was determined by proton nuclear magnetic resonance spectroscopy.

[0040] Example 1: Preparation of charge transfer complex based on organic macrocyclic aromatic hydrocarbons and study on the adsorption-photoinduced desorption performance of toluene; Preparation of EtP5-F4TCNQα: During preparation, 89.11 mg (0.1 mmol) of EtP5 and 55.23 mg (0.2 mmol) of F4TCNQ were mixed in an agate mortar and ground with a pestle for 30 min at room temperature to obtain the charge transfer complex EtP5-F4TCNQα.

[0041] Structural characterization of EtP5-F4TCNQα: The characteristic absorption band changes caused by charge transfer (CT) interactions can be detected by UV-Vis absorption spectroscopy. When white EtP5 and yellow F4TCNQ are mixed and ground in a 1:2 molar ratio, a significant color change occurs, yielding a yellowish-brown mixture powder. Solid-state UV-Vis absorption spectroscopy shows that EtP5-F4TCNQα has a distinct absorption band in the near-infrared region (800-1200 nm), which contrasts sharply with the absence of an absorption band in the near-infrared region for single-component EtP5 and F4TCNQ. Figure 3 ).

[0042] To investigate the effect of EtP5 and F4TCNQ mixed grinding on the crystal structure, PXRD tests were conducted. The PXRD images show (...). Figure 4 The PXRD spectrum of EtP5-F4TCNQα formed after mixing and grinding showed obvious peak overlap with the PXRD spectra of EtP5 and F4TCNQ, indicating the successful preparation of the charge transfer complex.

[0043] Fourier transform infrared spectroscopy analysis showed that ( Figure 5 The stretching vibration peak of the cyano (-CN) group in EtP5-F4TCNQα was 4 cm⁻¹ higher than that of its precursor F4TCNQ. -1 redshift (from 2224cm) -1 Move to 2220cm -1 This redshift can be attributed to the increased electron cloud density of the cyano nitrogen atom due to charge-transfer interactions, which weakens the bond force constant of the -CN bond. This result strongly confirms the formation of an efficient charge-transfer complex between EtP5 (electron donor) and F4TCNQ (electron acceptor).

[0044] Toluene adsorption performance test of EtP5-F4TCNQα: The adsorption amount was measured by nuclear magnetic resonance hydrogen spectroscopy (NMR). Figure 6 Quantitative characterization and analysis were performed. From... Figure 7It can be seen that the adsorption capacity gradually increases with the extension of adsorption time. After 8 hours of adsorption, EtP5-F4TCNQα reaches adsorption saturation. Calculations using the standard curve and peak area integration determined the saturation adsorption capacity to be 3.7 mol / EtP5-F4TCNQα, reflecting the maximum adsorption capacity of the charge-transfer complex for toluene under these conditions. After toluene adsorption, the color of EtP5-F4TCNQα macroscopically changes significantly from its original yellowish-brown to red (forming EtP5-F4TCNQα+Tol). This change is further verified by UV-Vis absorption spectroscopy: in the near-infrared region of 800-1200 nm, the absorption intensity of EtP5-F4TCNQα+Tol is significantly enhanced compared to EtP5-F4TCNQα. This spectral change is consistent with the macroscopic color change from yellowish-brown to red, indicating that toluene adsorption induces a change in the electronic structure of EtP5-F4TCNQα, thereby affecting its light absorption behavior. Figure 8 To further investigate the structural changes of EtP5-F4TCNQα during toluene adsorption, PXRD analysis was performed on the adsorbed sample (EtP5-F4TCNQα+Tol). Figure 9 It can be seen that the PXRD spectrum of EtP5-F4TCNQα after toluene adsorption shows significant changes in the position and intensity of the diffraction peaks compared to EtP5-F4TCNQα. Furthermore, the position and intensity of the diffraction peaks are almost identical to those simulated by EtP5-F4TCNQα+Tol. This indicates that EtP5-F4TCNQα underwent structural reorganization during adsorption, ultimately forming a new crystal phase structure (i.e., EtP5-F4TCNQ@Tol).

[0045] An investigation into the formation mechanism of EtP5-F4TCNQα host-guest interaction: To further investigate the formation mechanism of this type of host-guest interaction, EtP5-F4TCNQ crystals were grown in a mixed solution of chloroform and methylcyclohexane. Figure 10From a crystal structure perspective, EtP5 and F4TCNQ maintain stability through multiple non-covalent interactions, including C–H···π interactions, π···π stacking interactions, and C–H···O hydrogen bonds. Using toluene as a solvent, a ternary eutectic of EtP5, F4TCNQ, and toluene (i.e., EtP5-F4TCNQ@Tol crystal) was successfully grown. Subsequent crystal structure analysis revealed detailed intermolecular interactions within the eutectic system. The structure shows that one F4TCNQ molecule is embedded between two EtP5 macrocycles, forming a sandwich structure; simultaneously, two toluene molecules are encapsulated within the EtP5 cavity, while another toluene molecule is primarily located outside the cavity; the entire supramolecular assembly is stably maintained through abundant weak interactions, mainly including C–H···π interactions, C–H···O hydrogen bonds, and C–H···F halogen bonds, among other non-covalent interactions, which collectively maintain the stability of the EtP5-F4TCNQ@Tol crystal structure. Figure 11 ).

[0046] Photoinduced toluene desorption and cycling performance testing of EtP5-F4TCNQα: To investigate the toluene release behavior of EtP5-F4TCNQα under photoinduced conditions, a systematic vapor desorption experiment was conducted. From Figure 12 It can be seen that within just 1 minute after the start of illumination, the amount of remaining toluene in EtP5-F4TCNQ@Tol decreased significantly, with more than 50% of the adsorbed toluene being rapidly released; by 10 minutes, toluene was completely desorbed, indicating that this charge-transfer complex possesses highly efficient photoresponsive release characteristics. During the toluene desorption process, the crystal structure of EtP5-F4TCNQ@Tol gradually transformed into the EtP5-F4TCNQ binary eutectic crystal form (…). Figure 13 Along with this structural transformation, the material's appearance also changed significantly, gradually transitioning from an initial red to a yellowish-brown. Figure 14 This color change can be quantitatively monitored using ultraviolet-visible absorption spectroscopy (UV-Vis). Figure 15 It can be seen that with increasing illumination time, the absorption intensity in the near-infrared region of 800-1200 nm gradually increases, indicating that the electronic structure of EtP5-F4TCNQα+Tol undergoes a corresponding evolution during desorption (gradually reverting to the electronic structure of EtP5-F4TCNQα); after 10 min of illumination, the absorption spectrum basically no longer changes, indicating that the desorption process is nearing completion (completely reverting to EtP5-F4TCNQα). Furthermore, the cycling stability experiment results show ( Figure 16After five consecutive adsorption-desorption cycles, the adsorption capacity of EtP5-F4TCNQα for toluene did not decrease significantly, indicating that the charge transfer complex has good structural reversibility and recyclability.

[0047] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A photoresponsive charge transfer complex, characterized in that, The compound is based on a columnar pentaaryl aromatic hydrocarbon and uses 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone as a guest. The columnar pentaaryl aromatic hydrocarbon is an electron donor, and 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone is an electron acceptor. The electron donor and electron acceptor are combined through charge transfer interactions.

2. A method for preparing the photoresponsive charge transfer complex according to claim 1, characterized in that, Includes the following steps: The pentane aromatic hydrocarbon was mixed with 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone and placed in an agate mortar. The mixture was ground at room temperature until the color of the mixture turned yellowish-brown, thus obtaining a photoresponsive charge transfer complex.

3. The preparation method according to claim 2, characterized in that, The molar ratio of the columnar pentaaryl aromatic hydrocarbon to 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone is 1:

2.

4. The application of the photoresponsive charge transfer complex according to claim 1 in toluene adsorption, characterized in that, The photoresponsive charge transfer complex was used as an adsorbent and contacted with toluene in a closed vapor adsorption system to achieve toluene adsorption.

5. The application according to claim 4, characterized in that, The closed vapor adsorption system is constructed as follows: 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. After sealing, the system is placed in a room temperature environment for adsorption.

6. The application of the photoresponsive charge transfer complex according to claim 1 in the photoinduced desorption of toluene, characterized in that, Includes the following steps: Adsorption pretreatment: The photoresponsive charge transfer complex adsorbs toluene, forming a complex after toluene adsorption; Photoinduced desorption: The toluene-adsorbed complex is irradiated with a near-infrared laser to achieve toluene desorption.

7. The application according to claim 6, characterized in that, The near-infrared laser has a wavelength of 808 nm and a power density of 0.4 W / cm². 2 .

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