Preparation method and application of porous organic polymer material based on nitrogen-containing heterocyclic skeleton

Abstract

The invention discloses a preparation method and application of a porous organic polymer adsorption material based on a nitrogen-containing heterocyclic skeleton. The material is prepared by taking benzo [c] cinnoline, pyridazine or phenanthroline derivatives as a nitrogen-containing skeleton, introducing vinyl through palladium-catalyzed coupling reaction and then polymerizing, has a micropore-mesopore hierarchical structure, and has the specific surface area of 214-893 m < 2 > / g. According to the material, efficient selective adsorption on SO2 is achieved through S delta < + >... N delta <-> dipole interaction, the SO2 adsorption capacity reaches 9.75 mmol / g under the conditions of 298 K and 1 bar, and the IAST selectivity of SO2 / CO2 (10: 90) reaches 450. A dynamic penetration experiment shows that the penetration time of the composite material to SO2 in SO2 / CO2 / N2 mixed gas reaches 969.34 min / g, and the capacity retention ratio after five times of circulation is greater than 95%. The method is simple in process, excellent in regeneration performance and suitable for efficient capture and separation of SO2 in industrial flue gas.

Description

Technical Field

[0001] This invention belongs to the field of environmental functional materials technology, specifically relating to a method for preparing porous organic polymer (POPs) adsorbent materials based on nitrogen-containing heterocyclic frameworks, and their application in selective SO2 capture and SO2 / CO2 separation. Background Technology

[0002] Sulfur dioxide (SO2), a major air pollutant, is primarily emitted from fossil fuel combustion, industrial smelting, and chemical production processes. Globally, over 87% of SO2 emissions are related to human activities. Excessive emissions not only lead to environmental problems such as acid rain and smog but also cause serious harm to the human respiratory system and the ecological environment. Currently, widely used industrial desulfurization technologies, such as wet limestone scrubbing, can partially remove SO2 from flue gas, but suffer from limited adsorption efficiency, the generation of large amounts of solid waste (such as CaSO3 / CaSO4), and secondary pollution. Furthermore, traditional adsorption materials such as activated carbon, zeolites, and metal oxides are insufficient to meet the demands for efficient and low-energy SO2 capture due to their low specific surface area, poor selectivity, or difficulty in regeneration. In recent years, porous materials such as metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have become research hotspots due to their high specific surface area and tunable pore structure. However, their strongly alkaline sites easily lead to irreversible SO2 chemisorption, high regeneration energy consumption, and some materials lack stability in humid or acidic environments.

[0003] Porous organic polymers are renowned for their all-organic composition, tunable pore structure, and adjustable chemical composition. To further balance adsorption performance and regeneration energy consumption, researchers have turned their attention to a new class of porous organic polymers. For example, the physical adsorption capacity for SO2 has been enhanced by introducing moderately basic nitrogen sites (such as tertiary amine groups). However, these materials still face significant challenges in practical applications: First, their selective adsorption capacity is insufficient, especially in SO2 / CO2 separation, where efficient sieving remains difficult due to the similar molecular diameters of the two gases. Second, there is a bottleneck in cycle stability; the material capacity tends to significantly decrease after multiple adsorption-desorption cycles. Most importantly, the control of adsorption forces remains difficult. For instance, while some nitrogen-containing polymers can adsorb SO2 through the interaction of lone pair electrons with the sulfur atoms of SO2, the adsorption heat is too high (>40 kJ / mol), making SO2 desorption difficult and regeneration energy consumption still significant, hindering truly efficient reversible capture. Therefore, developing novel porous organic polymers that combine high adsorption capacity, excellent selectivity (especially in SO2 / CO2 / N2 mixed gases) and reversible adsorption performance has become the key to solving the industrial desulfurization problem.

[0004] This invention employs a novel approach using porous organic polymers with unique nitrogen sites, avoiding the use of strongly basic groups that could hinder adsorbent regeneration and recovery. Whether pyridazine, benzo[c]cenline, or phenanthroline, the rings contain stable and moderately basic nitrogen atoms, allowing for reversible binding with low concentrations of sulfur dioxide. This invention prepared various porous organic polymers with different nitrogen sites, and calculated the SO2 / CO2 selectivity using the Ideal Adsorption Solution Theory (IAST). Based on the theoretical calculations, fixed-bed breakthrough experiments verified the actual separation capabilities of these porous organic polymers for sulfur dioxide / carbon dioxide / nitrogen. Density functional theory simulations determined the active sites of the porous organic polymers, elucidating their adsorption and separation mechanisms, providing a reference and direction for the future development of novel adsorbent materials. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing porous organic polymer adsorbent materials based on nitrogen-containing heterocyclic frameworks and their applications.

[0006] I. Preparation of porous organic polymer adsorbent materials The method for preparing the porous organic polymer adsorbent of the present invention includes the following steps: (1) The nitrogen-containing heterocyclic derivative was reacted with potassium vinyltrifluoroborate in a palladium catalyst, base and toluene / tetrahydrofuran / water mixed solvent under a nitrogen atmosphere at 80~100℃ for 20~25h, and the divinyl-substituted nitrogen-containing heterocyclic monomer was obtained after purification. The nitrogen-containing heterocyclic derivative is a dibromo derivative of benzo[c]cenline, pyridazine, or phenanthroline, preferably 3,8-dibromobenzo[c]cenline, 3,6-dibromopyridazine, or 3,8-dibromo-1,10-phenanthroline. The nitrogen-containing heterocyclic monomer is 3,8-divinylbenzo[c]cenline, 3,6-divinylpyridazine, or 3,8-divinyl-1,10-phenanthroline.

[0007] The molar ratio of the nitrogen-containing heterocyclic derivative to potassium vinyltrifluoroborate is 1:2.5 to 1:3.5; the palladium catalyst is tetra(triphenylphosphine)palladium, and the base is potassium carbonate; in the toluene / tetrahydrofuran / water mixed solvent, the volume ratio of H2O, toluene, and tetrahydrofuran is 1:(3~5):(3~4).

[0008] (2) The nitrogen-containing heterocyclic monomer from step (1) is reacted with azobisisobutyronitrile in a solvent at 373-408 K for 48-72 h. Unreacted monomers and impurities are removed by Soxhlet extraction to obtain porous organic polymer adsorbent materials POP-Bce, POP-Pyr, or POP-Phe. The solvent is DMF or THF; the mass ratio of the nitrogen-containing heterocyclic monomer to azobisisobutyronitrile is 10:1. The synthetic routes for POP-Bce, POP-Pyr, and POP-Phe are as follows: Figure 1-3 .

[0009] II. Structure of Adsorption Materials Will pass 13 The structure of the adsorbent material was analyzed using several methods, including CCP / MAS NMR, FT-IR, TG, SEM, TEM, and nitrogen adsorption-desorption curves.

[0010] 1. 13 CCP / MAS NMR analysis Figure 4 (a) shows the solid-state carbon NMR spectrum of POP-Phe, with three strong signal peaks between 128 and 150.7 ppm and two strong signal peaks at 39.9 and 27.1 ppm. The three strong peaks in the 128-150.7 ppm range are attributed to the 1,10-phenanthroline skeleton, while the latter two are related to the C-C bonds after vinyl polymerization.

[0011] Solid state of polymer POP-Bce 13 CCP / MAS NMR spectrum as follows Figure 4 As shown in (b), similar to POP-Phe, the three signal peaks in the 120.5–144.9 ppm range are attributed to the benzo[c]cenline skeleton, with the latter two related to the C-C bonds after vinyl polymerization. Solid state of polymer POP-Pyr 13 CCP / MAS NMR spectrum as follows Figure 4 As shown in (c), the peaks at 127.2 and 162.1 ppm belong to two types of carbons within the pyridazine, while the peak at 30.9 ppm and its shoulder belong to two alkyl carbons after vinyl polymerization. 13 C CP / MAS NMR indicates the successful synthesis of the three polymers.

[0012] 2.FT-IR analysis To further confirm the structures of the three adsorbent materials, FT-IR analysis was performed on POP-Phe, POP-Bce, and POP-Pyr. The infrared spectra of the three polymers correspond to their respective characteristic peaks, as shown below. Figure 5 As shown.

[0013] Between 1500 and 1690 cm-1 There are stretching vibrations of C=N double bonds, N=N double bonds, and the benzene ring. The C=N bending vibrations of POP-Phe, POP-Bce, and POP-Pyr are located at 2925, 2933, and 2929 cm⁻¹, respectively. -1 Location. Additionally, at 2233.6, 2233.1, and 2235.0 cm. -1 A CN stretching vibration peak appeared at [location missing]. The synthesis of the adsorbent was further confirmed by FT-IR.

[0014] 3. TG Analysis Thermogravimetric analysis of three adsorbent materials, POP-Phe, POP-Bce, and POP-Pyr, in different temperature ranges is as follows: Figure 6 As shown, under the action of a nitrogen gas flow, POP-Phe began to decompose significantly at 677 K. The TG curve of POP-Phe shows a 1.85% mass loss within the temperature range of 26–200 °C, likely due to the volatilization of solvents such as methanol and N,N-dimethylformamide. The curve is relatively flat within this range, indicating that the sample was sufficiently dried. In comparison, while POP-Bce and POP-Pyr have lower thermal stability than POP-Phe, both materials exhibit good stability at 200 °C and are still suitable for industrial desulfurization applications.

[0015] 4. Nitrogen adsorption-desorption curve analysis like Figure 7 As shown in (a), the nitrogen adsorption-desorption isotherms and corresponding pore size distribution curves of POP-Phe exhibit Type I and Type IV curves, indicating the presence of micropores and mesopores. When the relative pressure is below 0.1 bar, micropore filling occurs during the test. The figure shows a hysteresis loop isotherm and no obvious saturation adsorption plateau, indicating the presence of mesopores and a highly irregular pore structure. The pore size distribution, calculated using nonlocal density functional theory (NLDFT) of the N2 adsorption-desorption isotherms, also confirms this, showing that POP-Phe mainly exists in the form of micropores and mesopores, which is beneficial for gas adsorption. The specific surface area of ​​POP-Phe is approximately 893 m². 2 / g, total pore volume is 1.20 cm³. 3 / g.

[0016] POP-Bce and POP-Pyr, for example Figure 7 As shown in (b, c), the pore size distribution of POP-Bce and POP-Pyr is still dominated by micro and mesopores, and the specific surface areas of POP-Bce and POP-Pyr are approximately 334 and 214 m², respectively. 2 / g, with total pore volumes of 0.31 and 0.59 cm³. 3 / g.

[0017] 5. SEM and TEM analysis SEM observation of POP-Phe ( Figure 8 This allows us to obtain samples with irregular shapes and irregular pores. Furthermore, TEM analysis of POP-Phe confirmed the existence of hierarchical pores, with comparable results observed in POP-Bce and POP-Pyr.

[0018] III. Adsorption Performance Study 1. Static adsorption performance of single-component gases To investigate the adsorption capacity of the adsorbent material for different gases, especially carbon dioxide and sulfur dioxide, adsorption isotherms of the adsorbent material for sulfur dioxide, carbon dioxide and nitrogen were measured at 273 and 298 K using different gases.

[0019] (1) Nitrogen adsorption isotherm For N2 molecules, all three adsorbents exhibited exclusion resistance to the gas, showing almost no adsorption. Even at 273 K, the maximum adsorption capacity of POP-Phe was only 0.13 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 in the pore structure, thus the adsorption capacity gradually increases with increasing pressure. Notably, the adsorption capacity of nitrogen decreases with increasing temperature. This may be because as temperature increases, the interaction force between the guest molecules and the adsorbent decreases, and since adsorption is an exothermic process, increasing temperature favors desorption rather than adsorption, thus reducing the adsorption capacity.

[0020] (2) Carbon dioxide adsorption isotherm CO2 adsorption tests were conducted on three types of POPs to evaluate the selectivity of SO2 for other flue gas components. For example... Figure 9 As shown, at 298 K and 1 bar, the CO2 adsorption capacities of POP-Phe, POP-Pyr, and POP-Bce are 1.59, 1.36, and 0.50 mmol / g, respectively. Even at 273 K, the maximum adsorption capacity is only 2.23 mmol / g. Compared to SO2, the CO2 adsorption capacity is much smaller. Observing the shape of the adsorption isotherms in the figure, it can be found that the adsorption isotherms of CO2 for the three adsorbents are nearly linear. The CO2 adsorption capacity gradually increases with increasing pressure within the studied pressure range, indicating that the relative interaction between the three adsorbents and carbon dioxide molecules is relatively weak. In particular, POP-Pyr has a CO2 adsorption heat of only 8.8 kJ / mol.

[0021] (3) Sulfur dioxide adsorption isotherm like Figure 10As shown in the figure, observing the shape of the adsorption isotherms reveals that the adsorption isotherms of SO2 for the three adsorbents basically exhibit a type I pattern. Under low pressure, the adsorption capacity increases rapidly. Taking 298 K as an example, at 0.0012 and 0.1 bar, the adsorption capacity of POP-Phe for sulfur dioxide reaches 1.49 and 4.72 mmol / g, respectively. After 0.2 bar, the increase in adsorption begins to slow down. At 1 bar, adsorption equilibrium is reached, with an adsorption capacity of 9.75 mmol / g. At 273 K, the adsorption capacities of the three adsorbents for SO2 reach 15.4, 12.9, and 11.7 mmol / g, respectively.

[0022] The adsorption enthalpy (Qst) of SO2 was also calculated. Under limited surface coverage, SO2 exhibits a low Qst, ranging from 17 to 21 kJ / mol. The interaction between the N-containing functional groups in POP-Phe and sulfur dioxide is relatively weak; SO2 is adsorbed onto the polymer surface and within its pores via intermolecular forces, insufficient to generate a large heat of adsorption. Figure 10 As shown in (c), the Qst of the material decreases with increasing SO2 loading. This indicates that the host-guest interaction weakens and SO2 molecules have occupied the main binding sites.

[0023] Based on the above data, it can be concluded that this type of adsorbent possesses excellent sulfur dioxide adsorption capacity, surpassing many reported porous materials, such as DMOF-TM (9.68 mmol / g), TAM-POF (9.45 mmol / g), Mg-MOF-74 (8.60 mmol / g), MFM-300(In) (8.28 mmol / g), SIFSIX-2-Cu-i (6.90 mmol / g), PI-COF-m20 (5.60 mmol / g), and Zn(bdc)(ted). 0.5 (4.41 mmol / g), KAUST-8 (2.90 mmol / g). Notably, the hysteresis loop between the adsorption and desorption isotherms indicates a strong interaction between SO2 and the adsorbent. Compared to CO2 and N2, these adsorbents exhibit higher adsorption performance for SO2, and this significant adsorption difference suggests their potential application value in the separation of SO2 / CO2 mixed systems.

[0024] The gas adsorption and separation mechanism mainly includes the following three principles: First, the molecular sieve effect (i.e., steric hindrance mechanism) based on the difference in gas molecule size; second, the kinetic effect, which is dominated by the diffusion rate of gas molecules, and its speed is related to the molecular configuration characteristics, the pore structure parameters of the adsorbent, and the interaction of adsorption sites; and finally, the equilibrium mechanism, where gas separation occurs when the pore size of the adsorbent is significantly larger than that of the two molecules, and the separation selectivity mainly stems from the difference in their equilibrium adsorption.

[0025] As shown in Table 1, the kinetic diameters of sulfur dioxide, carbon dioxide, and nitrogen are 4.1, 3.3, and 3.6-3.8 Å, respectively, all smaller than the pore size of the adsorbent material. Therefore, all gases can enter the pores within the adsorbent. However, due to the significant differences in the polarity of gas molecules, their varying physical properties can lead to differences in adsorption capacity. Furthermore, the adsorbent itself possesses specific adsorption sites, resulting in substantial variations in adsorption amounts. Therefore, the adsorption mechanism can be summarized as an equilibrium mechanism, with high gas adsorption capacity typically associated with strong host-guest interactions.

[0026] 2. Selective separation performance of sulfur dioxide / carbon dioxide Based on the combination of selectivity calculation and adsorption thermodynamic analysis according to the ideal adsorption solution theory, an evaluation of the separation capability of SO2 / CO2 component system was constructed. By calculating the IAST selectivity parameters, the gas sieving performance of the material was analyzed.

[0027] in Figure 12 The figures show the fitted adsorption curves for sulfur dioxide and carbon dioxide gases. The fitting parameters for the DSLF equations of POP-Phe, POP-Bce, and POP-Pyr are listed in Tables 2, 3, and 4, respectively. The isothermal adsorption data of sulfur dioxide and carbon dioxide were fitted using POP-Phe at 298 K, with the squared correlation coefficients R(SO2). 2 =0.99987 and R(CO2) 2 =0.99997, indicating a high degree of agreement between the model and the actual model. The theoretical maximum adsorption capacities of the adsorbent calculated using the two-site Langmuir-Freundlich adsorption isotherm model were 9.724 and 1.587 mmol / g, respectively, which are close to the experimental data (9.754 and 1.588 mmol / g), thus providing an explanation for the experimental data. Similarly, fitting was performed on POP-Bce and POP-Pyr, and the correlation coefficients were both greater than 0.999, indicating a high degree of agreement, and these models can be used.

[0028] like Figure 11 As shown, the selectivity of SO2 / CO2 (10:90) was calculated using the Ideal Adsorption Solution Theory (IAST). Notably, POP-Phe exhibits an IAST selectivity of up to 450 for SO2 / CO2, surpassing many previously reported adsorbents. The selectivities for POP-Bce and POP-Pyr are 153 and 115, respectively. These results indicate that POPs exhibit competitive selective adsorption of SO2, suggesting that SO2 may be more readily adsorbed onto Phe-Phe, POP-Pyr, and POP-Bce in mixed gases.

[0029] 3. Analysis of the gas-mixture penetration experiment Breakthrough curves can be used to study the dynamic adsorption behavior of gases in porous media, providing theoretical support for industrial applications. This section uses fixed-bed breakthrough experiments to demonstrate the good dynamic separation performance of the adsorbents for the ternary SO2 / CO2 / N2 mixture. To investigate the actual separation performance of POP-Phe, POP-Bce, and POP-Pyr, a flow rate of 20 cm⁻¹ was used at 298 K and 1 bar. 3 A dynamic breakthrough experiment was conducted on a SO2 / CO2 / N2 (0.17 / 15 / 84.83 v %) mixture at a speed of 0.5 min.

[0030] like Figure 13 As shown in (a), the dynamic breakthrough experiment demonstrates that the fixed bed filled with POP-Phe can successfully separate SO2 from the SO2 / CO2 / N2 mixed gas. It can be seen that the breakthrough times of N2 and CO2 in the POP-Phe fixed bed are 0.66 and 3.74 min / g, respectively. N2 and CO2 break through the POP-Phe material in a very short time, and the N2 and CO2 concentrations at the outlet rise rapidly, achieving complete breakthrough at 1.04 and 6.44 min / g, respectively. In contrast, the breakthrough time of SO2 in the POP-Phe fixed bed is as long as 969.34 min / g, indicating that POP-Phe has a strong adsorption capacity for SO2 and excellent SO2 adsorption and separation capabilities. Furthermore, the dynamic saturation SO2 capacity can reach 1.47 mmol / g. Observing the shape of the breakthrough curve, the steep rise of the curve indicates a fast mass transfer rate of SO2 by POP-Phe, further demonstrating the high utilization rate of SO2 gas adsorption by POP-Phe.

[0031] Similarly, such as Figure 13As shown in (b, c), the breakthrough times of N2 and CO2 in the POP-Bce and POP-Pyr fixed beds were 0.90 min / g, 2.09 min / g, and 0.24 min / g, 0.24 min / g, respectively. The outlet concentrations of N2 and CO2 increased rapidly, achieving complete breakthrough at 1.50 min / g, 5.05 min / g, 1.00 min / g, and 3.13 min / g, respectively. The SO2 breakthrough times for POP-Bce and POP-Pyr were 293.5 and 57.1 min / g, respectively, with saturated SO2 capacities of 0.45 and 0.03 mmol / g, respectively. Compared to the breakthrough curve of POP-Phe, the breakthrough curves of POP-Bce and POP-Pyr showed a slower rise, especially for POP-Pyr, which only reached complete equilibrium at 700 min / g. This indicates that the mass transfer rate of SO2 by POP-Pyr is extremely slow.

[0032] 4. Cyclic testing and in-situ FT-IR testing To verify the material's reusability and feasibility for industrial application, we conducted SO2 adsorption cycling experiments on this POP-Phe. Figure 14 As shown, although POP-Phe has a high SO2 adsorption capacity under low pressure, after being reactivated at 100°C in a vacuum, POP-Phe exhibits fully reversible SO2 absorption for more than 5 cycles at 298 K, with almost no loss of absorption capacity, demonstrating the material's excellent recyclability.

[0033] To understand the excellent reversible adsorption characteristics of POP-Phe for SO2, in-situ FT-IR experiments were conducted using a Nicolet 6700 FT-IR spectrometer (e.g., Figure 15 (As shown). During continuous SO2 introduction, at 2455, 1320, and 1048 cm⁻¹... -1 An absorption peak related to SO2 adsorption appears at 2455 and 1320 cm⁻¹, and the intensity of the absorption peak increases with adsorption time, reaching saturation after 10 minutes of continuous adsorption. Notably, similar to previous studies, absorption peaks at 2455 and 1320 cm⁻¹ are observed. -1 The two signal peaks indicate the presence of physical adsorption of SO2, while the 1048 cm⁻¹ peak... -1 The appearance of the signal peak indicates the presence of S2O5. 2-Multilayer adsorption is observed. These signals decrease with increasing temperature gradient, indicating that the desorption process has begun. Notably, the signal peaks essentially disappear when the temperature rises to 120 °C, indicating that irreversible chemisorption of SO2 does not occur in POP-Phe. Combined with cyclic testing, POP-Phe retains its initial capacity after 5 adsorption-desorption cycles. These results demonstrate that POP-Phe exhibits good recovery ability for SO2, effectively confirming the material's reusability and feasibility for industrial applications.

[0034] 5. Density functional theory simulation calculations To gain a deeper understanding of the adsorption mechanism, density functional theory (Table 5 and...) was employed. Figure 16 The adsorption energy of SO2 by POP-Phe was simulated. The adsorption energy of SO2 was -18.0 kJ / mol.

[0035] The surface electrostatic potential distribution of SO2 molecules and three types of nitrogen-containing adsorbents (POP-Phe, POP-Bce, and POP-Pyr) was analyzed using Gaussian 9. The calculation results show that sulfur atoms in SO2 molecules exhibit a significant positive electrostatic potential on the van der Waals surface, because the polarity of the SO bonds within the SO2 molecule leads to the accumulation of positive charge on the sulfur atoms. Conversely, a distinct negative electrostatic potential region exists around the pyridine and pyridazine nitrogen sites on the adsorbent surface, mainly due to the delocalization of lone pair electrons within nitrogen atoms in the nitrogen-containing adsorbent materials, resulting in the enrichment of negative charge on the nitrogen atoms. This complementary distribution of positive and negative potentials indicates a strong electrostatic attraction between sulfur and nitrogen atoms. The electrostatic potential calculations revealed an electrostatic interaction between S in SO2 and N in the adsorbent, providing a theoretical basis for designing highly efficient sulfur oxide capture materials.

[0036] To further investigate the adsorption behavior of sulfur dioxide in adsorbent materials and gain a deeper understanding of the differences in sulfur dioxide adsorption by POP-Phe, POP-Bce, and POP-Pyr at the molecular level, density functional theory simulations were used to model the interaction mechanisms between POP-Phe, POP-Bce, and POP-Pyr and sulfur dioxide molecules. Each sulfur dioxide molecule interacts with sulfur dioxide molecules via S... δ+ ···N δ- The dipole interactions are adsorbed into the material. For example... Figure 17 As shown, each sulfur dioxide molecule can form a double S with two N atoms from adjacent phenanthroline, benzo[c]cenline, and pyridazine. δ+ ···N δ-The dipole-dipole interactions have interaction distances of 2.59 Å and 3.11 Å, 2.59 Å and 3.23 Å, and 2.55 Å and 3.61 Å, respectively. These distances are all smaller than the sum of the van der Waals radii of S and N atoms (4.08 Å). Overall, the distances between S in SO2 and N in POP-Phe (2.59 and 3.11 Å) are smaller than the distances between S in SO2 and N in POP-Bce and POP-Pyr (2.59 Å and 3.23 Å, 2.55 Å and 3.61 Å, respectively). The distances between O···N were also calculated. Notably, the calculations showed that the distances between each sulfur dioxide molecule and the two O···N molecules in the adjacent phenanthroline, benzo[c]cenline, and pyridazine were mostly greater than the van der Waals radius (~3.07 Å). The van der Waals attraction was insufficient to overcome the repulsive force between the atomic nucleus and the electron cloud, resulting in an effective interaction approaching zero, indicating that there was no significant van der Waals interaction between them.

[0037] Molecular dynamics simulations revealed significant differences in the RDF peaks of nitrogen atoms and adsorbate atoms (SO2, CO2, and N2) within the POP-Phe framework at 298 K equilibrium. Figure 18 As shown, the RDF value of NS(SO2) is much higher than that of NC(CO2) and NN(N2). The interaction between POP-Phe and SO2 is stronger than that between POP-Bce and POP-Pyr and SO2, which is consistent with the DFT calculation. Therefore, the N sites in POP-Phe are more likely to interact with SO2 in the gas mixture, indicating the feasibility of the practical application of POP-Phe in selectively adsorbing SO2 in SO2 / CO2 / N2 gas mixtures. Simulation results show that POP-Phe has a strong attraction to sulfur dioxide, which is consistent with experimental results.

[0038] In summary, this invention prepares novel porous organic polymers with unique nitrogen sites, avoiding the difficulties in adsorbent regeneration and recovery caused by the use of strongly basic groups. Among them, POP-Phe exhibits good adsorption performance under low pressure and demonstrates excellent selective separation performance in breakthrough experiments. In-situ FT-IR, RDF, electrostatic potential, and DFT calculations revealed the binding sites and interaction mechanisms of sulfur dioxide molecules in the channels of POP-Phe, POP-Bce, and POP-Pyr, providing a deeper understanding of the sulfur dioxide capture mechanisms of POP-Phe, POP-Bce, and POP-Pyr.

[0039] 1. Static adsorption experiments on SO2 / CO2 / N2 revealed that POP-Phe, POP-Bce, and POP-Pyr exhibited weak adsorption for nitrogen and carbon dioxide, with CO2 adsorption capacities of 1.59, 1.36, and 0.50 mmol / g, respectively, at 298 K and 1.0 bar. However, they showed strong adsorption for sulfur dioxide, with POP-Phe reaching an adsorption capacity of 2.59 mmol / g at low pressure (0.01 bar). The selectivity of SO2 / CO2 (10:90) was calculated using the Ideal Adsorption Solution Theory (IAST). The IAST selectivities of POP-Phe, POP-Bce, and POP-Pyr for sulfur dioxide / carbon dioxide (10 / 90) were 450, 153, and 115, respectively.

[0040] 2. Fixed-bed breakthrough experiments show that POP-Phe has excellent dynamic separation performance for sulfur dioxide / carbon dioxide / nitrogen, and POP-Phe has a short mass transfer zone and a fast mass transfer rate, showing potential application prospects.

[0041] 3. Density functional theory simulations show that each sulfur dioxide molecule passes through S... δ+ ···N δ- The dipole interactions are adsorbed in the material. The RDF peak values ​​of nitrogen atoms and adsorbate atoms (SO2, CO2 and N2) in the POP-Phe, POP-Bce and POP-Pyr frameworks show significant differences. The RDF value of NS (SO2) is much higher than that of NC (CO2) and NN (N2). Furthermore, by calculating the electrostatic potential, it was found that there is a strong electrostatic interaction between S in SO2 and N in the adsorbent.

[0042] The beneficial effects of this invention are: This invention achieves efficient and selective capture and separation of SO2 by designing porous organic polymer (POPs) adsorbents with specific nitrogen sites, exhibiting excellent adsorption performance, selective separation, regeneration stability, structural characteristics, and industrial applicability.

[0043] (1) Highly efficient adsorption performance: This material combines a designed nitrogen-containing heterocyclic skeleton (benzo[c]cenline, pyridazine, phenanthroline) with a controllable vinyl crosslinking network to construct unique Sδ+···Nδ- dipole interaction sites (interaction distance 2.55-3.61 Å) at the molecular level, achieving highly efficient recognition and capture of SO2. Under standard conditions (298 K, 1 bar), the SO2 adsorption capacity of POP-Phe reached 9.75 mmol / g, far exceeding that of traditional adsorbents.

[0044] (2) Excellent selective separation capability: The IAST selectivity of SO2 / CO2 (10:90) mixture reached 450, and the dynamic adsorption performance of SO2 in actual ternary gas mixture (SO2 / CO2 / N2) was verified by fixed bed breakthrough experiment.

[0045] (3) Good regeneration performance and stability: The moderate heat of adsorption of the material (17-21 kJ / mol) gives it excellent regeneration characteristics, and the capacity retention rate exceeds 95% after 5 cycles.

[0046] (4) Structural advantages and designability: The microporous-mesoporous hierarchical structure (specific surface area 214-893 m² / g) and the tunable nitrogen-containing framework further expand the design flexibility of the material.

[0047] (5) Industrial application potential: The raw materials are readily available and the synthesis process is simple. The mild synthesis process and stable physicochemical properties provide a solid foundation for its application in complex industrial scenarios such as coal-fired power plants and metallurgical tail gas. Compared with traditional wet desulfurization technology, it has significant advantages of no secondary pollution and low energy consumption. Attached Figure Description

[0048] Figure 1 Synthetic route of POP-Bce; Figure 2 Synthetic route of POP-Pyr; Figure 3 Synthetic route of POP-Phe; Figure 4 Solid-state carbon spectra of POP-Phe (a), POP-Bce (b) and POP-Pyr (c); Figure 5 Infrared spectra of POP-Phe (a), POP-Bce (b) and POP-Pyr (c); Figure 6 Thermogravimetric curves of POP-Phe, POP-Bce and POP-Pyr; Figure 7 Nitrogen isotherms and pore size distributions of POP-Phe (a, b), POP-Bce (c, d) and POP-Pyr (e, f); Figure 8 TEM (a, b) and SEM (c, d) of POP-Phe; Figure 9 CO2 adsorption isotherms of POP-Phe, POP-Bce and POP-Pyr at 298 K (a) and 273 K (b) and heat of adsorption of CO2 (c). Figure 10SO2 adsorption isotherms of POP-Phe, POP-Bce and POP-Pyr at 298 K (a) and 273 K (b) and heat of adsorption of SO2 (c); Figure 11 POP-Phe, POP-Bce and POP-Pyr regarding SO2 / CO2 (10:90) IAST selectivity; Figure 12 The adsorption isotherms of SO2 and CO2 for POP-Phe (a, d), POP-Bce (b, e) and POP-Pyr (c, f) were fitted using the two-site Langmuir-Freundlich equation. Figure 13 POP-Phe (a), POP-Bce (b), and POP-Pyr (c) were used for SO2 / CO2 / N2 mixed gas (SO2 / CO2 / N2 = 0.17 / 15.0 / 84.83 v % , flow rate = 20 cm). 3 Transmission curve ( / min, 298 K); Figure 14 Cyclic adsorption isotherm of SO2 on POP-Phe at 298 K; Figure 15 In-situ FT-IR changes of SO2 adsorbed by POP-Phe at 30℃ over time and SO2 desorption at different temperatures; Figure 16 Surface electrostatic potential of POP-Phe (a), POP-Bce (b), POP-Pyr (c) and SO2 (d); Figure 17 Adsorption information of SO2 molecules in different adsorbents; Figure 18 Radial distribution function plots of SO2, CO2, N2 and POP-Phe (a), POP-Bce (b), and POP-Pyr (c). Detailed Implementation

[0049] The preparation method of the porous organic polymer adsorbent material of the present invention will be further described in detail below through specific embodiments.

[0050] Example 1: Synthesis of POP-Bce (1) A mixture of 2,5-dibromonitrobenzene (22.8725 g, 81.4 mmol), copper powder (16.4752 g, 25.9 mmol), and N,N-dimethylformamide (100 mL) was transferred to a 250 mL flask. The mixture was evacuated three times under nitrogen circulation and heated to 120 °C for 6 h. After the reaction was completed, 150 mL of toluene was added, and the mixture was filtered to obtain a clear filtrate. The filtrate was washed with water and brine, dried over anhydrous magnesium sulfate, and the toluene was evaporated to obtain a yellow solid product, dibromodinitrobiphenyl (10.0574 g, 25 mmol, 61.5%).

[0051] (2) The mixture of dibromodinitrobiphenyl (3.7051 g, 9.22 mmol), anhydrous diethyl ether (200 mL), and toluene (100 mL) obtained in step (1) was transferred to a 500 mL two-necked flask. The mixture was evacuated three times under nitrogen circulation. Lithium aluminum hydride was added under a nitrogen atmosphere, and the reaction was carried out at room temperature for 1.5 h, followed by a further reaction at 45 °C for 0.5 h. The reaction was confirmed by TLC. After the reaction was completed, the lithium aluminum hydride was quenched with water. The mixture was filtered through a glass plate filter funnel, and the organic layer was extracted with dichloromethane. The organic layer was dried with anhydrous sodium sulfate and then subjected to rotary evaporation to remove excess solvent. The crude product was separated by column chromatography with DCM:PE = 1:1 as the eluent. The target product 3,8-dibromobenzo[c]cenline (1.6201 g, 4.79 mmol, 52%) was obtained.

[0052] (3) The mixture of 3,8-dibromobenzo[c]cenline (7.0005 g, 20.7 mmol), potassium vinyltrifluoroborate (8.3777 g, 62.5 mmol), potassium carbonate (17.0056 g, 125.0 mmol), tetra(triphenylphosphine)palladium (0.4818 g, 0.42 mmol), H2O (25 mL), toluene (100 mL), and tetrahydrofuran (90 mL) obtained in step (2) 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, it 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 3,8-divinylbenzo[c]cenline (1.6201 g, 4.79 mmol, 52%).

[0053] (4) Dissolve 1 g of 3,8-divinylbenzo[c]cenline and 100 mg of azobisisobutyronitrile (AIBN) in DMF (10 mL). Transfer the mixed solvent to a polytetrafluoroethylene reactor and heat at 373 K for 48 h. After the reaction is complete, wash with dichloromethane and then extract the product with methanol to remove impurities, obtaining the porous organic polymer POP-Bce. The synthetic route is as follows: Figure 1 Solid-state carbon NMR spectrum as follows Figure 4 (b).

[0054] Example 2 Synthesis of POP-Pyr (1) A mixture of 3,6-dibromopyridazine (8.01 g, 33.7 mmol), potassium vinyltrifluoroborate (13.52 g, 100.9 mmol), potassium carbonate (27.44 g, 201.8 mmol), tetra(triphenylphosphine)palladium (0.772 g, 0.67 mmol), H2O (20 mL), toluene (100 mL), and tetrahydrofuran (90 mL) 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, the crude product was post-processed and separated by column chromatography to obtain the target product 3,6-divinylpyridazine (2.29 g, 17.3 mmol, 51.6%).

[0055] (2) 1 g of 3,6-divinylpyridinium and 100 mg of azobisisobutyronitrile (AIBN) were dissolved in THF (10 mL). The mixed solvent was transferred to a polytetrafluoroethylene reactor and heated at 408 K for 72 h. After the reaction, the product was washed with dichloromethane and then extracted with methanol to remove impurities, yielding POP-Pyr. The synthetic route is as follows. Figure 2 Solid-state carbon NMR spectrum as follows Figure 4 (c).

[0056] Example 3 Synthesis of POP-Phe A mixed solution of 3,8-dibromo-1,10-phenanthroline (2.0 g, 5.95 mmol), potassium vinyltrifluoroborate (2.39 g, 17.86 mmol), potassium carbonate (4.86 g, 35.71 mmol), tetrakis(triphenylphosphine)palladium (0.275 g, 0.238 mmol), H₂O (20 mL), toluene (70 mL), and tetrahydrofuran (70 mL) was transferred to a 250 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 product was treated. The crude product was subjected to column chromatography to give the yellow product 3,8-divinyl-1,10-phenanthroline (0.83 g, 3.57 mmol, 62.8%).

[0057] 1 g of 3,8-divinyl-1,10-phenanthroline and 100 mg of azobisisobutyronitrile (AIBN) were dissolved in DMF (10 mL). The mixed solvent was transferred to a polytetrafluoroethylene reactor and heated at 373 K for 48 h. After the reaction, the product was washed with dichloromethane and then extracted with methanol to remove impurities, yielding POP-Phe. The synthetic route is as follows: Figure 3 Solid-state carbon NMR spectrum as follows Figure 4 (a).

Claims

1. A method for producing a porous organic polymer adsorbent material based on a nitrogen-containing heterocyclic skeleton, characterized by, The method comprises the following steps: (1) reacting nitrogen-containing heterocyclic derivatives with potassium vinyltrifluoroborate in a palladium catalyst, a base and a mixed solvent of toluene / tetrahydrofuran / water under a nitrogen atmosphere at 80-100 ℃ for 20-25 h to obtain a divinyl-substituted nitrogen-containing heterocyclic monomer through purification; the nitrogen-containing heterocyclic derivatives are dibrominated derivatives of benzo[c]cinnoline, pyridazine or phenanthroline; (2) heating the nitrogen-containing heterocyclic monomer in step (1) to 373-408 K in a solvent for 48-72 h with azobisisobutyronitrile to obtain a porous organic polymer adsorption material through purification.

2. The method of claim 1, wherein: In step (1), the nitrogen-containing heterocyclic derivatives are 3,8-dibromobenzo[c]cinnoline, 3,6-dibromopyridazine or 3,8-dibromo-1,10-phenanthroline; the nitrogen-containing heterocyclic monomer is 3,8-divinylbenzo[c]cinnoline, 3,6-divinylpyridazine or 3,8-divinyl-1,10-phenanthroline.

3. The method of claim 1, wherein: In step (1), the molar ratio of the nitrogen-containing heterocyclic derivatives to potassium vinyltrifluoroborate is 1:2.5-1:3.5; the palladium catalyst is tetrakis(triphenylphosphine)palladium, and the base is potassium carbonate; in the mixed solvent of toluene / tetrahydrofuran / water, the volume ratio of H2O, toluene and tetrahydrofuran is 1:(3-5):(3-4).

4. The method of claim 1, wherein: In step (2), the solvent is DMF or THF; the mass ratio of the nitrogen-containing heterocyclic monomer to azobisisobutyronitrile is 10:

1.

5. The porous organic polymeric adsorbent material prepared according to the method of any one of claims 1 to 4, characterized in that: The material has microporous and mesoporous structures, a specific surface area of 214-893 m² / g, a pore volume of 0.31-1.20 cm³ / g; and the nitrogen-containing heterocyclic units in the material skeleton are benzo[c]cinnoline, pyridazine or phenanthroline derivatives.

6. The porous organic polymeric adsorbent material of claim 5, wherein: The adsorption amount of SO2 is ≥9.75 mmol / g at 298 K and 1 bar, and the IAST selectivity of SO2 / CO2 is as high as 450.

7. The porous organic polymer adsorption material according to claim 5 is applied to SO2 adsorption and separation.

8. Use according to claim 7, characterized in that: The material is used for selective separation of SO2 / CO2, SO2 / N2 or SO2 / CO2 / N2 mixed gas.

9. Use according to claim 8, characterized in that: The material preferentially adsorbs SO2 in SO2 / CO2 / N2 mixed gas, and the SO2 breakthrough time in a dynamic breakthrough experiment is as long as 969.34 min / g.

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