Preparation and application of porous organic polymer adsorption material based on Trger alkali skeleton

Abstract

The invention discloses preparation and application of a porous organic polymer adsorption material based on a Trger alkali skeleton. According to the adsorbent, a divinyl Trger alkali monomer is synthesized through a Suzuki coupling reaction, and then a porous polymer material with a specific pore diameter structure is prepared through free radical polymerization. The material comprises unmodified POP-TB, POP-eTB into which an ethylene group is introduced, and POP-Me-TB into which an arylmethyl group is introduced. Under the conditions of 298 K and 1 bar, the adsorbing capacity of SO2 reaches 6.48-8.85 mmol / g, and the IAST selectivity of SO2 / CO2 reaches up to 406. In a low-concentration SO2 dynamic penetration experiment simulating an actual flue gas condition, the POP-eTB still keeps the SO2 penetration time of 346 min / g in a mixed gas containing 2% of water vapor, and the adsorption performance is not attenuated after six times of circulation. By regulating and controlling the electron cloud density and the aperture structure of the Trger alkali skeleton, efficient selective adsorption of SO2 is achieved, the technical problems that an existing adsorption material is low in selectivity and poor in water stability are solved, and the method can be widely applied to the fields of flue gas desulfurization and industrial waste gas treatment.

Description

Technical Field

[0001] This invention belongs to the field of porous organic polymer materials technology, specifically relating to a porous organic polymer (POPs) adsorbent material based on the Tröger base framework, its preparation method and application, which is particularly suitable for the efficient selective adsorption of SO2 and the separation of mixed gases. Background Technology

[0002] In the current field of environmental pollution control, efficient capture and separation technologies for sulfur dioxide (SO2) face significant challenges. Existing adsorbent materials such as metal-organic frameworks (MOFs), activated carbon, and zeolites have obvious limitations in industrial applications: Although MOFs have adjustable pore structures, their hydrothermal stability is generally poor, and they are prone to structural degradation or pore collapse in humid flue gas environments; activated carbon, while inexpensive, has limited selective adsorption capacity for SO2, and during regeneration, it is prone to pore blockage due to carbon buildup or sulfate deposition leading to adsorption capacity decay; traditional zeolite adsorbents, due to their narrow pore size distribution and lack of adjustability, are difficult to effectively sieve mixtures of SO2 (kinetic diameter 4.1 Å) with CO2 (3.3 Å) and N2 (3.6-3.8 Å). More importantly, industrial waste gases often contain 2-5% water vapor, which can react with SO2 to form sulfurous acid, corroding the adsorbent, not only damaging equipment but also occupying adsorption sites, significantly reducing the material's cycle stability and adsorption efficiency. In recent years, researchers have attempted to enhance SO2 affinity by introducing open metal sites (such as Mg-MOF-74) or constructing hydrogen bonding sites (such as the MFM-300 series). However, these strategies often reduce the selectivity of SO2 / N2 or SO2 / CO2 due to competitive adsorption of molecules such as CO2 and H2O, and their performance degrades significantly in humid environments.

[0003] Porous organic polymers (POPs) have emerged as an emerging solution due to their designable chemical structures and excellent stability. However, conventional POPs suffer from insufficient electron cloud density at nitrogen sites, resulting in weak dipole interactions with SO2 and limited adsorption capacity and unsatisfactory selectivity. Furthermore, existing Tröger base polymers exhibit an excessively wide pore size distribution (1-5 nm), failing to precisely match the SO2 molecular size, leading to adsorption capacities (generally <5 mmol / g) and selectivity (SO2 / CO2 <100) that are insufficient to meet practical requirements. In summary, existing SO2 adsorption materials generally suffer from technical bottlenecks such as insufficient hydrothermal stability, low selectivity, weak resistance to water interference, and poor regeneration performance, severely hindering the development of flue gas desulfurization and industrial waste gas treatment technologies. Therefore, there is an urgent need to develop novel adsorption materials that combine high adsorption capacity, high selectivity, excellent hydrothermal stability, and good regeneration performance. Summary of the Invention

[0004] The present invention aims to provide a porous organic polymer (POP) adsorbent based on a Tröger base framework, its preparation method, and its applications. This invention, by introducing nitrogen sites, modifies the pore structure through the introduction of aryl methyl and ethylene groups, thereby enhancing the affinity for SO2; and by altering the chemical environment surrounding the nitrogen sites, it increases the dipole moment. Through these methods, the adsorption capacity for SO2 can be enhanced, and the selectivity for sulfur dioxide / carbon dioxide can be improved.

[0005] I. Preparation method of porous organic polymer adsorbent based on Tröger base (1) The Tröger base derivative was reacted with potassium vinyltrifluoroborate, potassium carbonate and tetra(triphenylphosphine)palladium in a toluene / tetrahydrofuran / water mixed solvent at 80-100°C for 20-25 hours under a nitrogen atmosphere, and the divinylTröger base monomer was obtained after purification.

[0006] The Tröger base derivative is 2,8-dibromo-6H,12H-5,11-methylenedibenzo[b,f][1,5]diazaarocal, 2,8-dibromo-6H,12H-5,11-ethylenedibenzo[b,f][1,5]diazaarocal, or 2,8-dibromo-4,10-dimethyl-6H,12H-5,11-methylenedibenzo[b,f][1,5]diazaarocal; The porous organic polymer adsorbent is a Tröger base skeleton polymer POP-TB without aryl methyl or ethylene group, a Tröger base skeleton polymer POP-eTB with ethylene group, or a Tröger base skeleton polymer POP-Me-TB with aryl methyl.

[0007] The molar ratio of the Tröger base derivative to potassium vinyltrifluoroborate is 1:3 to 1:4, and the volume ratio of H2O, toluene, and tetrahydrofuran in the toluene / tetrahydrofuran / water mixed solvent is 1:5:5.

[0008] (2) The divinyl Tröger base monomer obtained in step (1) and the azobisisobutyronitrile initiator are heated to 360~380K in DMF and reacted for 20~30h. After washing and drying, a porous organic polymer adsorbent is obtained. The mass ratio of the divinyl Tröger base monomer to the azobisisobutyronitrile is 10:1.

[0009] The synthesis method of 2,8-dibromo-6H,12H-5,11-ethylenedibenzo[b,f][1,5]diazo[octano] is as follows: 2,8-dibromo-6H,12H-5,11-methylenedibenzo[b,f][1,5]diazo[octano], 1,2-dibromoethane, and Li2CO3 are added to DMF and reacted at 100~120℃ for 70~75 hours. After the reaction is completed, the product is quenched, extracted, and concentrated by rotary evaporation. The crude product is separated by column chromatography to obtain the target product. The molar ratio of 2,8-dibromo-6H,12H-5,11-methylenedibenzo[b,f][1,5]diazo[octano], 1,2-dibromoethane, and Li2CO3 is 1:(4~5):(4~5).

[0010] The synthesis method of 2,8-dibromo-4,10-dimethyl-6H,12H-5,11-methylenedibenzo[b,f][1,5]diaza-aromaoctylene is as follows: 2-methyl-4-bromoaniline, paraformaldehyde, and CF3COOH are mixed and stirred in an ice-salt bath at -15°C. After the mixture reaches room temperature, stirring is continued for 45-50 hours. Ice and 30% ammonia solution are added to adjust the pH to 9-10. The target product is obtained by column chromatography. The molar ratio of 2-methyl-4-bromoaniline to paraformaldehyde is 1:2.

[0011] II. Structure of Adsorbent Materials Will pass 13 The structure of the adsorbent material was analyzed using several methods, including C CP / MAS, NMR, TG, SEM, TEM, and nitrogen adsorption-desorption curves.

[0012] 1. 13 CCP / MAS NMR analysis like Figure 4 As shown in a, through solid-state 13 C10 NMR confirmed the formation of POP-eTB. Three strong peaks were observed at 149.1, 136.9, and 127.6 ppm, attributed to the carbon atoms of the benzene ring in the polymer backbone. The peak at 59.5 ppm belonged to the carbon atom of the ethyl group between the two nitrogen groups. Simultaneously, the peaks in the 110–120 ppm range disappeared, related to vinyl radical polymerization, while a strong peak appeared at 46.7 ppm, assigned to the polymerized vinyl groups. Figure 4 b, 4c are shown through solid-state 13 C10 NMR confirmed the formation of POP-TB and POP-Me-TB. In conclusion, the monomer has been successfully converted into a polymer.

[0013] 2. TG Analysis Thermogravimetric analysis of POP-eTB adsorbent material in different temperature ranges, such as Figure 5As shown in the figure, the thermogravimetric analysis (TG) curve of POP-eTB was tested, and the material exhibits good thermal stability. Under a nitrogen atmosphere, the TG curve of POP-eTB shows a significant downward trend at 690 K, indicating that the sample's skeleton begins to decompose and the structure collapses. Notably, a small amount of mass loss occurred within the temperature range of 23–56°C. This is likely due to the evaporation of residual dichloromethane solvent within the polymer during heating, indicating that the DMF in the POP-eTB sample was fully replaced by dichloromethane during the washing process.

[0014] 3. Nitrogen adsorption-desorption curve analysis Figure 6 The nitrogen adsorption-desorption isotherms of POP-eTB are typical Type I and Type IV curves, indicating the presence of micropores and mesopores. The sharp increase in the isotherm at relative pressures (P / P0) below 0.1 is due to micropore filling, demonstrating the microporous structure of POP-eTB. The presence of hysteresis loops and the absence of a clear saturation adsorption plateau indicate the presence of mesopores and a highly irregular pore structure. The pore size distribution of POP-eTB was calculated using nonlocal density functional theory (NLDFT) of the N2 adsorption-desorption isotherms, as shown below. Figure 6 As shown in (f), its main pore size distribution is at 1.27 nm. The calculated BET surface area of ​​POP-eTB is 486 m². 2 / g, total pore volume is 0.30 cm³. 3 / g. By introducing ethylene groups, the minimum pore size increased from 0.46 nm to 1.0 nm, thus improving the minimum pore diameter.

[0015] Furthermore, nitrogen adsorption-desorption isotherms of POP-TB and POP-Me-TB were tested under the same conditions. Analysis of the nitrogen adsorption isotherms of POP-TB and POP-Me-TB revealed them to be typical Type I and Type IV curves, indicating the presence of micropores and mesopores, respectively. The specific surface areas of the two materials were 523 and 604 m², respectively. 2 / g, with total pore volumes of 0.40 and 0.44 cm³, respectively. 3 / g. The main pore size distribution of POP-TB is concentrated at 0.64 and 1.27 nm, and similarly, the main pore size distribution of POP-Me-TB is concentrated at 0.64 and 1.27 nm. However, it is worth noting that the regulatory effect of introducing aryl methyl groups on the pore structure of the material is reflected in the synergistic improvement of micropore volume and total pore volume. Specifically, gas adsorption isotherm analysis revealed that POP-Me-TB maintains its micro- and mesoporous advantages (BET specific surface area reaches 604 m²). 2While the contribution of its pore size distribution curve to pore volume in the 1-4 nm range was improved, the most significant increase was in the pore volume contribution rate of 1.27 nm micropores, from 0.33 cm⁻¹. 3 / g increased to 0.46 cm 3 The increased specific surface area and pore volume of the POP-Me-TB sample provide more adsorption sites for SO2 gas molecules, thus improving the SO2 adsorption performance of the sample. Furthermore, the aryl methyl group, as a hydrophobic functional group, alters the polarity distribution of the material surface, creating a microenvironment more conducive to gas molecule adsorption.

[0016] 4. SEM and TEM analysis The morphology of POP-eTB was characterized by SEM and TEM. POP-eTB is a polyhedral block with significant irregular morphological features and a hierarchical porous structure. Figure 7 SEM images (a, b) show that the POP-eTB particles exhibit an amorphous stacking morphology with blurred boundaries and numerous nanoscale depressions. This disordered porous structure endows the material with a high specific surface area (up to 486 m² / g) and a wide pore size distribution, which is beneficial for improving gas adsorption capacity and gas molecule diffusion. Furthermore, the TEM images reveal the presence of layered porosity.

[0017] III. Adsorption Performance 1. Static adsorption performance of single-component gases To investigate the adsorption capacity of the adsorbent material for different gases, particularly carbon dioxide and sulfur dioxide, adsorption isotherms for carbon dioxide and nitrogen were measured at 273 and 298 K using different gases. Adsorption isotherms for sulfur dioxide were measured at 298, 313, and 333 K.

[0018] (1) Nitrogen adsorption isotherm like Figure 8 As shown, all three adsorbents exhibit exclusion resistance to nitrogen gas for N2 molecules, showing almost no adsorption. Even at 298 K, the maximum adsorption capacity of POP-TB is only 0.06 mmol / g. This may be related to the physical properties of the gas molecules. Due to the extremely weak interaction between nitrogen and the adsorbent framework, N2 can be uniformly distributed within the pore structure; therefore, the adsorption capacity gradually increases with increasing pressure. Compared to POP-TB, the nitrogen adsorption capacity of POP-Me-TB and POP-eTB, which incorporate arylmethyl and ethylene groups respectively, decreases to only 0.05 and 0.04 mmol / g.

[0019] (2) Carbon dioxide adsorption isotherm To investigate the CO2 adsorption capacity of the adsorbents, the CO2 adsorption curves of POP-TB, POP-Me-TB, and POP-eTB were tested at temperatures of 273 and 298 K, respectively. Figure 9 As shown in (b), the CO2 adsorption capacities of POP-TB, POP-Me-TB, and POP-eTB were 1.25, 1.06, and 0.93 mmol / g, respectively. Figure 9 As shown in (a), even at 273 K, the maximum adsorption capacities of the three adsorbents were only 2.31 g, 1.78 and 1.66 mmol / g, respectively, indicating that the interaction between these three adsorbents and carbon dioxide molecules was relatively weak.

[0020] The adsorption capacities of POP-Me-TB and POP-eTB decreased after the introduction of aryl methyl and ethylene groups, respectively, at 298 K, with reductions of 0.19 and 0.32 mmol / g, respectively. This indicates that the introduction of aryl methyl or ethylene functional groups into the POP-TB framework design may inhibit carbon dioxide adsorption due to both steric hindrance and dipole moment, thus weakening the adsorption performance of the adsorbent for CO2.

[0021] The adsorption heat (Qst) of POP-eTB, calculated by the virial method using the carbon dioxide adsorption isotherm, is approximately 29.79 kJ / mol. The adsorption heats of POP-TB and POP-Me-TB are 35.05 and 28.24 kJ / mol, respectively.

[0022] (3) Sulfur dioxide adsorption isotherm Figure 10The sulfur dioxide adsorption isotherms of POP-eTB, POP-TB, and POP-Me-TB at different temperatures are shown under pure SO2 conditions. It can be seen that at 1 bar SO2 and 298 K, the SO2 adsorption capacities of POP-eTB, POP-TB, and POP-Me-TB are 8.85, 7.86, and 6.48 mmol / g, respectively, with POP-eTB exhibiting a higher SO2 adsorption capacity than POP-TB and POP-Me-TB. Based on the above data, this adsorbent exhibits excellent sulfur dioxide adsorption capacity, surpassing many reported porous materials such as Mg-MOF-74 (8.60 mmol / g), MFM-300(In) (8.28 mmol / g), P(D[VImC6]Br) (7.80 mmol / g), MS-1.0mPEI (7.50 mmol / g), MFM-305 (6.99 mmol / g), SIFSIX-2-Cu-i (6.90 mmol / g), NbOFFIVE-Cu-TPA (6.32 mmol / g), PI-COF-m20 (5.60 mmol / g), MFM-600 (5.00 mmol / g), and Zn(bdc)(ted). 0.5 (4.41 mmol / g), ZU-801 (~3.5 mmol / g), KAUST-8 (2.90 mmol / g).

[0023] The introduction of ethylene-based functional groups into the POP-TB framework significantly improved its SO2 adsorption capacity. This is attributed to the enhanced electron-donating inductive effect of the alkyl group, which increases with the size of the substituent, leading to a substantial increase in the electron cloud density around the nitrogen atom and the formation of stronger local negative charge centers, thus enhancing the dipole interaction with SO2. Conversely, the introduction of aryl methyl functional groups into the POP-TB framework, possibly due to the increased steric hindrance caused by the aryl methyl group, made it difficult for the adsorption sites to bind with sulfur dioxide, resulting in a decrease in the SO2 adsorption capacity of POP-Me-TB.

[0024] It is worth noting that the heat of SO2 adsorption can be calculated using SO2 isotherms at different temperatures. For example... Figure 10 As shown in (d), the SO2 adsorption heats of POP-eTB, POP-TB, and POP-Me-TB are 39.08, 34.42, and 16.27 kJ / mol, respectively. Similarly, these adsorbents exhibit a relatively large adsorption capacity for SO2, but a lower adsorption capacity compared to CO2 and N2, indicating their ability to separate SO2 / CO2 and SO2 / N2 mixed gases.

[0025] 2. Selective separation performance of sulfur dioxide / carbon dioxide The selectivity of SO2 / CO2 under simulated flue gas conditions was evaluated using the Ideal Adsorption Solution Theory (IAST) model. Figure 12 The figures show the fitted adsorption curves for sulfur dioxide and carbon dioxide. The fitting parameters for the DSLF equations of POP-eTB, POP-TB, and POP-Me-TB are listed in Tables 1, 2, and 3, respectively. The isothermal adsorption data of sulfur dioxide and carbon dioxide by POP-eTB at 298 K were fitted, and the squared correlation coefficients were R(SO2). 2 =0.99982 and R(CO2) 2 =1 indicates a high degree of fit for the model. Similarly, fitting POP-TB and POP-Me-TB also yielded correlation coefficients greater than 0.999, indicating a high degree of fit, and therefore the model can be used.

[0026] like Figure 11 As shown, the selectivity of SO2 / CO2 (10:90) was calculated using the Ideal Adsorption Solution Theory (IAST). Notably, the SO2 / CO2 IAST selectivity of POP-eTB is as high as 406, exceeding that of many previously reported adsorbents. The selectivities of POP-TB and POP-Me-TB are 289 and 38, respectively.

[0027] 3. Analysis of the gas-mixture penetration experiment To further evaluate the actual desulfurization effect of the adsorbent, a dynamic breakthrough experiment was conducted. Gas (SO2 / CO2 / N2 = 0.17 / 15.0 / 84.83 v % , flow rate = 10 cm⁻¹) 3 ( / min, 298 K) flows through an activated adsorbent (POP-eTB, POP-TB, and POP-Me-TB) packed column. For example... Figure 13As shown in (a, b, c), carbon dioxide and nitrogen breakthrough occur within a very short time, while sulfur dioxide breakthrough time on POP-eTB is 398 min / g, indicating that POP-eTB has a strong adsorption capacity for sulfur dioxide and good sulfur dioxide adsorption and separation capabilities, with a dynamic saturated SO2 adsorption capacity of 0.61 mmol / g. The breakthrough times for sulfur dioxide on other materials, POP-TB and POP-Me-TB, are 443 and 237 min / g, respectively, with dynamic saturated sulfur dioxide adsorption capacities of 0.65 and 0.23 mmol / g, respectively. Besides the competitive adsorption between sulfur dioxide and carbon dioxide, the negative impact of large amounts of water vapor in industrial waste gas should also be considered, as sulfur dioxide will generate sulfurous acid in the presence of water, which is highly corrosive. To investigate the effect of water on the dynamic separation of the adsorbent, as shown in... Figure 13 As shown in (d, e, f), the SO2 breakthrough experiments of POP-eTB, POP-TB, and POP-Me-TB under a 2% water vapor supply were further investigated. Notably, POP-eTB exhibited similar SO2 adsorption curves with and without water vapor, indicating that POP-eTB possesses excellent water resistance, maintaining a breakthrough time of 346 min / g and a corresponding saturated SO2 adsorption capacity of 0.47 mmol / g in humid atmospheres. POP-TB and POP-Me-TB achieved breakthrough times of 342 and 138 min / g, respectively, with corresponding saturated sulfur capacities of 0.51 and 0.24 mmol / g.

[0028] 4. Cyclic testing and in-situ FT-IR testing Repeatability and stability of materials are essential parameters for practical applications. To verify the repeatability and feasibility of industrial applications, we conducted SO2 adsorption cycling experiments on this POP-eTB. Figure 14 As shown, at 298 K, POP-eTB exhibits fully reversible SO2 absorption for more than 6 cycles with almost no loss of absorption capacity, demonstrating the material's excellent recyclability.

[0029] The dynamic adsorption and desorption process of SO2 by porous organic polymers was studied using in-situ FT-IR spectroscopy, with POP-eTB selected as a typical sample. Figure 15 (a) shows the in-situ adsorption process of SO2 in POP-eTB collected at atmospheric pressure. Notably, the adsorption capacity reached a rapid equilibrium within 10 min, at 1660 and 1304 cm⁻¹. -1 New absorption peaks appeared at [location missing]. These absorption peaks are attributed to the asymmetric stretching vibration (V0) of S=O in SO2. as ) and symmetric tensile vibrations of physical adsorption (V s ).exist Figure 15 In (b), as the temperature increases, SO2 gradually desorbs from the polymer. When the temperature reaches approximately 333 K, the signal peak essentially disappears, indicating that POP-eTB does not undergo irreversible chemical adsorption of SO2 and can achieve complete desorption. Combining cyclic testing and in-situ infrared spectroscopy, it can be concluded that POP-eTB exhibits good stability in the selective adsorption and separation of SO2.

[0030] 5. Simulation calculation To further evaluate the host-guest interactions between guest molecules and polymers at the atomic level, we investigated the adsorption behavior of N2, CO2, and SO2 under aqueous and anhydrous conditions using density functional theory (DFT) calculations. The adsorption configurations and corresponding adsorption energy data are presented in [Table / Table / Insert Table ... Figure 16 As shown in Table 4, without considering the presence of water, the distance between SO2 and POP-eTB (2.53 Å) is significantly smaller than the distance between CO2 / N2 and POP-eTB (2.90 / 3.09 Å), causing the corresponding adsorption energy to gradually decrease from -55.4 kJ / mol to -23.5 kJ / mol and then to -11.0 kJ / mol. Similarly, a similar phenomenon exists with POP-TB and POP-Me-TB. The distance between SO2 and POP-TB (2.46 Å) is significantly smaller than the distance between CO2 / N2 and POP-TB (2.79 / 3.29 Å), causing the corresponding adsorption energy to gradually decrease from -51.7 kJ / mol to -24.9 kJ / mol and then to -9.2 kJ / mol. The distance between SO2 and POP-Me-TB (2.63 Å) is significantly smaller than the distance between CO2 / N2 and POP-eTB (2.90 / 3.19 Å), resulting in the corresponding adsorption energy decreasing from -42.5 kJ / mol to -21.5 kJ / mol and then gradually decreasing to -10.4 kJ / mol.

[0031] The presence of H2O in the mixed gas has little effect on the adsorption of SO2 / CO2 / N2 by the POP-eTB monomer, with corresponding adsorption energies of -54.6, -25.4, and -10.8 kJ / mol, respectively. Based on the adsorption energy analysis results, POP-eTB exhibits excellent selective adsorption performance for SO2 and excellent water resistance. The performance of POP-TB and POP-Me-TB is comparable to that of POP-eTB; however, their adsorption capacity for SO2 is slightly lower, with corresponding adsorption energies of -51.7 and -42.5 kJ / mol, respectively.

[0032] To explore the underlying mechanisms behind the significant selective adsorption of SO2 by polyoxymethylene (POPs), the analysis of intrinsic bond orbitals (IBOs) and electronic localization functions (ELFs) has proven to be a powerful tool for understanding host-guest interactions. The nitrogen atom in the POP monomer possesses unpaired electrons, such as... Figure 17 As shown in (ac), the electron density of N in POP-eTB is slightly greater than that in POP-TB and POP-Me-TB. When POPs adsorb SO2 molecules, electrons on the N atom begin to transfer to the S atom, as shown in (ac). Figure 17 As shown in (df), this results in a decrease in the electron density on nitrogen atoms in POPs. It is worth noting that the POP-eTB monomer has the highest degree of electron transfer. Figure 17 The ELF plot shown in (gi) provides a clearer visualization, revealing that the ELF region between the N and S atoms gradually darkens, indicating that the interaction between SO2 and the N site gradually weakens. In summary, the nitrogen sites in POP-eTB have a higher electron density, which is more conducive to the adsorption of SO2 molecules.

[0033] The diffusion of N2, CO2, H2O, and SO2 molecules in POP-eTB was studied using mean square displacement (MSD). Figure 18 a) quantitatively determined the diffusion coefficient ( Figure 18 b). Diffusion coefficients (D) of N2, CO2, H2O, and SO2 s The values ​​are 17.9 × 10⁻⁶ respectively. -8 7.2×10 -8 1.3×10 -8 and 0.82×10 -8 m 2 These results indicate that SO2 molecules diffuse much more slowly than CO2 molecules.

[0034] In summary, this invention provides a rationally designed novel porous organic polymer solid adsorbent based on the Tröger base framework, which can be used for efficient, stable, and highly reversible adsorption-desorption of SO2. In-situ FT-IR, intrinsic bond orbital (IBOs), electronic localization function (ELF), mean square shift (MSD), and density functional theory (DFT) calculations revealed the binding sites and interaction mechanisms of sulfur dioxide molecules in the channels of POP-eTB, POP-TB, and POP-Me-TB, providing a deeper understanding of the sulfur dioxide capture mechanisms of POP-eTB, POP-TB, and POP-Me-TB. Specific conclusions are as follows: 1. Static adsorption experiments of POP-eTB, POP-TB, and POP-Me-TB on sulfur dioxide, carbon dioxide, and nitrogen showed that POP-eTB, POP-TB, and POP-Me-TB exhibited weak adsorption of nitrogen and carbon dioxide, but strong adsorption of sulfur dioxide. These materials thus possess the ability to separate SO2 / CO2 mixtures. The selectivity of SO2 / CO2 (10:90) was calculated using the Ideal Adsorption Solution Theory (IAST). The selectivities of POP-eTB, POP-TB, and POP-Me-TB for sulfur dioxide / carbon dioxide (10:90) were 406, 289, and 38, respectively.

[0035] 2. Fixed-bed breakthrough experiments showed that these materials all possessed good sulfur dioxide adsorption and separation capabilities. Based on this, the effect of water on the dynamic separation of the adsorbents was investigated. POP-eTB exhibited similar SO2 adsorption curves under conditions with and without water vapor, indicating that POP-eTB has excellent water resistance.

[0036] 3. At the atomic level, the host-guest interactions between guest molecules and polymers were further evaluated. Density functional theory (DFT) calculations were used to study the adsorption behavior of N2, CO2, and SO2 on the three polymers under both aqueous and anhydrous conditions. The distance between SO2 and POP-eTB was significantly smaller than that between CO2 / N2 and POP-eTB, and the adsorption energy between SO2 and POP-eTB was the highest among the three gases. Analysis of intrinsic bond orbitals (IBOs) and electronic localization functions (ELFs) revealed that the nitrogen sites in POP-eTB have a higher electron density, which is more favorable for SO2 molecule adsorption. The diffusion of N2, CO2, H2O, and SO2 molecules in POP-eTB was studied using mean square displacement (MSD). The diffusion of SO2 molecules was much slower than that of CO2, N2, and H2O molecules.

[0037] The beneficial effects of this invention: This invention has achieved a breakthrough in the field of SO2 capture through the innovative design of porous organic polymer (POPs) adsorbents based on the Tröger base framework. Its significant advantages are as follows: First, by precisely controlling the Tröger base framework structure and introducing ethylene groups or arylmethyl groups for modification, the pore size was successfully optimized to the range of 0.64-1.27 nm, achieving an ideal match with the SO2 molecular dynamic diameter (4.1 Å). Simultaneously, the electron cloud density of the nitrogen sites was significantly increased, resulting in an adsorption capacity of POP-eTB for SO2 as high as 8.85 mmol / g at 298 K and 1 bar. Second, the unique framework design endows the material with excellent selective separation performance. IAST theoretical calculations confirmed that POP-eTB achieves a selectivity of 406 for SO2 / CO2 (10:90) mixtures, which is 4-10 times higher than traditional materials. This is mainly due to the strong electron-donating effect of the ethylene groups, which enhances the dipole interaction with SO2. More importantly, the material exhibits excellent engineering application characteristics: it maintains an SO2 breakthrough time of 346 min / g in simulated flue gas containing 2% water vapor, and its performance shows no degradation after 6 adsorption-desorption cycles. TG analysis shows that its thermal stability is as high as 690K, solving the industry pain points of existing adsorbents being susceptible to water vapor interference and difficult regeneration. Furthermore, DFT calculations and IBO / ELF analysis revealed the electron transfer mechanism between nitrogen sites and SO2 at the atomic level, while MSD simulations demonstrated the diffusion coefficient of SO2 within the channels (0.82 × 10⁻⁻⁴). 8 The m² / s ratio is significantly lower than that of CO2, which explains the high selectivity from a kinetic perspective. These characteristics enable the material to combine high efficiency, stability, and economy in practical applications such as flue gas desulfurization and industrial waste gas treatment. Attached Figure Description

[0038] Figure 1 Synthetic route of POP-TB; Figure 2 Synthetic route of POP-eTB; Figure 3 Synthetic route of POP-Me-TB; Figure 4 Solid-state carbon spectra of POP-eTB (a), POP-TB (b) and POP-Me-TB (c); Figure 5 Thermogravimetric curve of POP-eTB; Figure 6 Nitrogen isotherms and pore size distributions of POP-TB (a, b), POP-Me-TB (c, d) and POP-eTB (e, f); Figure 7 SEM (a, b) and TEM (c, d) of POP-eTB; Figure 8 N2 adsorption isotherms of POP-TB, POP-Me-TB and POP-eTB at 298 K Figure 9 CO2 adsorption isotherms of POP-TB, POP-Me-TB and POP-eTB at 273 K (a) and 298 K (b); heat of carbon dioxide adsorption of POP-TB, POP-Me-TB and POP-eTB (c). Figure 10 SO2 adsorption isotherms of POP-eTB, POP-TB and POP-Me-TB at 298 K (a), 313 K (b) and 333 K (c); (d) Sulfur dioxide adsorption heat of POP-TB, POP-Me-TB and POP-eTB; Figure 11 POP-eTB, POP-Me-TB and POP-TB with respect to SO2 / CO2 (10:90) IAST selectivity; Figure 12 The adsorption isotherms of POP-eTB (a, d), POP-Me-TB (b, e), and POP-TB (c, f) with respect to SO2 and CO2 were fitted using the two-site Langmuir-Freundlich equation. Figure 13 POP-eTB (a, d), POP-TB (b, e), and POP-Me-TB (c, f) are used for SO2 / CO2 / N2 mixed gases (SO2 / CO2 / N2 = 0.17 / 15.0 / 84.83 v %, flow rate = 10 cm). 3 / min, 298 K) and (SO2 / CO2 / H2O / N2 = 0.17 / 15.0 / 2.0 / 84.83v %, flow rate = 20 cm 3 Transmission curve ( / min, 298 K); Figure 14 Cyclic adsorption isotherm of SO2 on POP-eTB at 298 K; Figure 15 In-situ FT-IR changes of SO2 adsorbed by POP-eTB over time and SO2 desorption at different temperatures; Figure 16 POP-eTB (a), POP-TB (b) and POP-Me-TB (c) adsorbents and their corresponding adsorption conformations; Figure 17IBOs analysis of SO2 adsorption configurations (df) and ELF contour plots (gi) of SO2 adsorption configurations for POP-eTB, POP-TB and POP-Me-TB monomers (ac). Figure 18 (a) Initial state of N2, CO2, H2O and SO2 molecules adsorbed by POP-eTB, (b) Mean square displacement (MSD) of each molecule in POP-eTB. Detailed Implementation

[0039] The present invention will be further illustrated below through specific embodiments.

[0040] Example 1: Synthesis of POP-TB (1) A mixture of 4-bromoaniline (18.0 g, 104.7 mmol), paraformaldehyde (6.35 g, 209.4 mmol), and CF3COOH (150 mL) was transferred to a 250 mL round-bottom flask and stirred vigorously in an ice-salt bath at -15°C. After the mixture reached room temperature and stirring continued for 48 hours, ice and 30% ammonia solution (200 mL) were slowly added to adjust the pH to 9-10. After the reaction was complete, the mixture was extracted with CH2Cl2 (3 × 50 mL), the organic layer was dried on MgSO4, and the solvent was removed under vacuum to obtain the crude product. The crude product was purified by column chromatography to obtain the target product 2,8-dibromo-6H,12H-5,11-methylenedibenzo[b,f][1,5]diazapentanoctanoic acid. (Yield: 60.3%) (2) The mixture of 2,8-dibromo-6H,12H-5,11-methylenedibenzo[b,f][1,5]diazapentaoctanoate (6.0 g, 15.8 mmol), potassium vinyltrifluoroborate (6.35 g, 47.4 mmol), potassium carbonate (13.07 g, 94.7 mmol), tetra(triphenylphosphine)palladium (0.36 g, 0.31 mmol), H2O (20 mL), toluene (100 mL), and tetrahydrofuran (100 mL) obtained in step (1) was transferred to a 500 mL flask. The mixture was evacuated three times under nitrogen circulation and heated to 90 °C for 24 h. After the reaction was completed, the result was confirmed by TLC, followed by quenching, extraction, and rotary evaporation concentration. The crude product was separated by column chromatography to obtain the target product 2,8-divinyl-6H,12H-5,11-methylenedibenzo[b,f][1,5]diazapentanoctyl. (Yield: 64.4%) (3) Dissolve 1 g of 2,8-divinyl-6H,12H-5,11-methylenedibenzo[b,f][1,5]diazapentanol and 100 mg of azobisisobutyronitrile (AIBN) in DMF (10 mL). Transfer the mixed solvent to a polytetrafluoroethylene reactor and heat at 373 K for 24 h. After the reaction is complete, wash with dichloromethane to remove impurities and obtain POP-TB. The synthetic route is as follows: Figure 1 .

[0041] Example 2 Synthesis of POP-eTB (1) 2,8-Dibromo-6H,12H-5,11-methylenedibenzo[b,f][1,5]diazapentine (12.0 g, 31.6 mmol), 1,2-dibromoethane (26.70 g, 142.1 mmol), Li₂CO₃ (11.67 g, 157.9 mmol) and 150 mL DMF were added to a 250 mL round-bottom flask. The resulting mixture was then heated to 110°C and reacted for 72 hours. After the reaction was completed, the reaction was confirmed by TLC, followed by quenching, extraction, and rotary evaporation for concentration. The crude product was separated by column chromatography to obtain the target product 2,8-dibromo-6H,12H-5,11-ethylenedibenzo[b,f][1,5]diazapentine. (Yield: 42.2%) (2) The mixture of 1 g of 2,8-dibromo-6H,12H-5,11-ethylenedibenzo[b,f][1,5]diazapentaoctanoate (5.28 g, 13.4 mmol), potassium vinyltrifluoroborate (5.39 g, 42.2 mmol), potassium carbonate (11.09 g, 80.4 mmol), tetra(triphenylphosphine)palladium (0.31 g, 0.29 mmol), H2O (20 mL), toluene (100 mL), and tetrahydrofuran (100 mL) obtained in step (1) was transferred to a 500 mL flask. The mixture was evacuated three times under nitrogen circulation and heated to 90 °C overnight. After the reaction was completed, the mixture was confirmed by TLC, and then quenched, extracted, and concentrated by rotary evaporation. The crude product was separated by column chromatography to obtain the target product 2,8-divinyl-6H,12H-5,11-ethylenedibenzo[b,f][1,5]diazapentanoctanoic acid (yield: 70.1%). (3) Dissolve 1 g of 2,8-divinyl-6H,12H-5,11-ethylenedibenzo[b,f][1,5]diazapentaoctanoic acid and 100 mg of azobisisobutyronitrile (AIBN) in DMF (10 mL). Transfer the mixed solvent to a polytetrafluoroethylene reactor and heat at 373 K for 24 h. After the reaction is complete, wash with dichloromethane to remove impurities and obtain POP-eTB. The synthetic route is as follows: Figure 2 .

[0042] Example 3 Synthesis of POP-Me-TB (1) A mixture of 2-methyl-4-bromoaniline (12.0 g, 64.5 mmol), paraformaldehyde (3.9 g, 129.0 mmol), and CF3COOH (150 mL) was transferred to a 250 mL round-bottom flask and stirred vigorously in an ice-salt bath at -15°C. After the mixture reached room temperature and stirring continued for 48 hours, ice and 200 mL of 30% ammonia solution were slowly added to adjust the pH to 9-10. After the reaction was complete, the mixture was extracted with CH2Cl2 (3 × 50 mL), the organic layer was dried on MgSO4, and the solvent was removed under vacuum to obtain the crude product. The crude product was purified by column chromatography to obtain the target product 2,8-dibromo-4,10-dimethyl-6H,12H-5,11-methylenedibenzo[b,f][1,5]diazapentanoctanoic acid. (Yield: 83.3%) (2) The mixture of 2,8-dibromo-4,10-dimethyl-6H,12H-5,11-methylenedibenzo[b,f][1,5]diazapentaoctanoate (5.8 g, 14.2 mmol), potassium vinyltrifluoroborate (5.71 g, 42.6 mmol), potassium carbonate (11.77 g, 85.3 mmol), tetra(triphenylphosphine)palladium (0.33 g, 0.29 mmol), H2O (20 mL), toluene (100 mL), and tetrahydrofuran (100 mL) obtained in step (1) was transferred to a 500 mL flask. The mixture was evacuated three times under nitrogen circulation and heated to 90 °C overnight. After the reaction was completed, the mixture was confirmed by TLC, followed by quenching, extraction, and rotary evaporation concentration. The crude product was separated by column chromatography to obtain the target product. (Yield: 73.4%) (3) Dissolve 1 g of 2,8-divinyl-4,10-dimethyl-6H,12H-5,11-methylenedibenzo[b,f][1,5]diazapentazo[azo]octanoic acid and 100 mg of azobisisobutyronitrile (AIBN) in DMF (10 mL). Transfer the mixed solvent to a polytetrafluoroethylene reactor and heat at 373 K for 24 h. After the reaction is complete, wash with dichloromethane to remove impurities to obtain POP-Me-TB. The synthetic route is as follows: Figure 3 .

Claims

1. A method for preparing a porous organic polymer adsorbent material based on a Tröger base framework, characterized in that, Includes the following steps: (1) The Tröger base derivative was reacted with potassium vinyltrifluoroborate, potassium carbonate and tetra(triphenylphosphine)palladium in a toluene / tetrahydrofuran / water mixed solvent at 80~100℃ for 20~25 hours under a nitrogen atmosphere, and the divinylTröger base monomer was obtained after purification. (2) The divinyl Tröger base monomer obtained in step (1) is reacted with azobisisobutyronitrile initiator in DMF and heated to 360~380K for 20~30h. After washing and drying, a porous organic polymer adsorbent material is obtained.

2. The preparation method according to claim 1, characterized in that: The Tröger base derivative is 2,8-dibromo-6H,12H-5,11-methylenedibenzo[b,f][1,5]diazaarocal, 2,8-dibromo-6H,12H-5,11-ethylenedibenzo[b,f][1,5]diazaarocal, or 2,8-dibromo-4,10-dimethyl-6H,12H-5,11-methylenedibenzo[b,f][1,5]diazaarocal; The porous organic polymer adsorbent is a Tröger base skeleton polymer POP-TB without aryl methyl or ethylene group, a Tröger base skeleton polymer POP-eTB with ethylene group, or a Tröger base skeleton polymer POP-Me-TB with aryl methyl group.

3. The preparation method according to claim 1, characterized in that: In step (1), the molar ratio of the Tröger base derivative to potassium vinyltrifluoroborate is 1:3 to 1:4, and the volume ratio of H2O, toluene and tetrahydrofuran in the toluene / tetrahydrofuran / water mixed solvent is 1:5:

5.

4. The preparation method according to claim 2, characterized in that: The synthesis method of 2,8-dibromo-6H,12H-5,11-ethylenedibenzo[b,f][1,5]diazo[octano] is as follows: 2,8-dibromo-6H,12H-5,11-methylenedibenzo[b,f][1,5]diazo[octano], 1,2-dibromoethane, and Li2CO3 are added to DMF and reacted at 100~120℃ for 70~75 hours. After the reaction is completed, the product is quenched, extracted, and concentrated by rotary evaporation. The crude product is then separated by column chromatography to obtain the target product. The molar ratio of 2,8-dibromo-6H,12H-5,11-methylenedibenzo[b,f][1,5]diazo[octano], 1,2-dibromoethane, and Li2CO3 is 1:(4~5):(4~5).

5. The preparation method according to claim 2, characterized in that: Synthesis of 2,8-dibromo-4,10-dimethyl-6H,12H-5,11-methylenedibenzo[b,f][1,5]diaza-aromaoctylene: 2-methyl-4-bromoaniline, paraformaldehyde, and CF3COOH were mixed and stirred in an ice-salt bath at -15°C. After the mixture reached room temperature, stirring was continued for 45-50 hours. Ice and 30% ammonia solution were added, and the pH was adjusted to 9-10. The target product was obtained by column chromatography. The molar ratio of 2-methyl-4-bromoaniline to paraformaldehyde was 1:

2.

6. The preparation method according to claim 1, characterized in that: In step (2), the mass ratio of the divinylTröger base monomer to azobisisobutyronitrile is 10:

1.

7. The porous organic polymer adsorbent material prepared by the method according to any one of claims 1-4, characterized in that: The adsorbent material has a BET surface area of ​​486~604 m² / g and a pore size distribution of 0.64~1.27 nm; its adsorption capacity for SO2 at 298 K and 1 bar is 6.48~8.85 mmol / g; and its IAST selectivity for SO2 / CO2 is as high as 406.

8. The application of the porous organic polymer adsorbent material according to claim 7 in SO2 adsorption and separation.

9. The application according to claim 8, characterized in that: Used for the selective separation of SO2 / CO2, SO2 / N2 or SO2 / CO2 / N2 mixed gases.

10. The application according to claim 9, characterized in that: When used in flue gas desulfurization or industrial waste gas treatment systems, the SO2 breakthrough time is 237~443 min / g, and it still maintains stable adsorption performance in the presence of water vapor.

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