A porphyrin-based porous organic salt and a preparation method and photocatalytic application thereof

Abstract

This invention discloses a porphyrin-based porous organic salt (Por-POS), its preparation method, and its photocatalytic application. Its chemical structure is shown in Formula 3. The preparation method is as follows: using the organic base 5,10,15,20-tetra(4-aminophenyl)-21H,23H-porphyrin (Formula 1) and the organic acid 1,5-naphthalenedisulfonic acid (Formula 2) as raw materials, Por-POS material is synthesized through charge-assisted hydrogen bond self-assembly and acid-base neutralization reaction. This method has advantages such as simple process, no need for external catalyst, mild reaction conditions, and short reaction time. The prepared Por-POS can serve as a highly efficient heterogeneous photocatalyst, exhibiting excellent photocatalytic activity and stability in the photocatalytic oxidative coupling reaction of benzylamine under blue light irradiation.

Description

Technical Field

[0001] This invention belongs to the field of design and preparation of functionalized porous materials, specifically relating to a porphyrin-based porous organic salt with photocatalytic activity and its preparation method, and further disclosing the application of this material in the photocatalytic benzylamine oxidative coupling reaction. Background Technology

[0002] In recent years, porous organic materials have shown broad application prospects in catalysis, adsorption, separation, energy storage, and photoelectric conversion due to their tunable pore structure, high specific surface area, and good functional modifiability. Among them, porous organic polymers (POPs) and covalent organic frameworks (COFs) are two representative material systems that have attracted widespread attention. POPs are usually formed by connecting organic building blocks through strong covalent bonds. Although they are structurally stable, their synthesis often depends on harsh reaction conditions (such as high temperature and the use of metal catalysts), and the post-processing is relatively cumbersome, which to some extent limits their large-scale preparation and functional integration. COFs are constructed through dynamic covalent chemistry (such as imine bonds, borate ester bonds, etc.) and have long-range ordered crystal structures. However, their bonding bonds have limited chemical stability in practical application environments such as strong acids, strong bases, or long-term light exposure, and are prone to hydrolysis or structural degradation. Especially in photo / thermal catalytic systems involving mass transfer and interfacial interactions, their long-term cycling stability faces challenges.

[0003] To overcome the limitations of the aforementioned covalently linked porous materials, porous organic salts (POSs) have also attracted widespread attention as an emerging type of porous material. POSs are typically constructed from organic acid and organic base modules with opposite charges through an ionic self-assembly strategy. This synthetic route has significant advantages: (1) the reaction conditions are mild, usually carried out at room temperature or lower temperatures in conventional solvents; (2) no metal catalysts or complex activation steps are required, making the synthesis process green and simple; (3) the assembly is driven by non-covalent forces such as strong electrostatic interactions, hydrogen bonds, and possible π-π stacking, resulting in an ionic framework with good chemical stability and reversible dynamic response characteristics. By rationally selecting or designing acidic / basic building blocks, the pore size, pore surface chemical environment, and charge distribution of POSs can be precisely controlled, thereby achieving selective recognition and efficient enrichment of specific guest molecules. Although POSs have shown initial potential in fields such as gas adsorption, ion conduction, and sensing, their development is still in its early stages, and the integration types of functional units are relatively limited. In particular, there is still a lot of room for exploration in constructing efficient, stable, and multifunctional photocatalysts that combine light capture and catalytic conversion capabilities.

[0004] Porphyrins and their derivatives are a class of classic functional molecules with large π-conjugated planar structures. Their unique electronic structure and photophysical properties make them ideal photosensitizers and catalytic active centers. Introducing porphyrin units into porous frameworks can effectively promote the separation and migration of photogenerated electron-hole pairs, while the confinement effect provided by the porous structure facilitates the enrichment of reactants near the active sites. Currently, strategies for integrating porphyrins into porous materials mainly include: participating in the construction of covalent organic frameworks (COFs) as nodes or linkers, loading them as guest components in porous polymers, or grafting them onto the material surface as modifying groups. However, the synthesis of porphyrin COFs based on strong covalent bonds is difficult, and the bond stability problem still exists; physical loading or surface modification methods may face problems such as low loading of active sites, easy detachment, or uneven distribution.

[0005] Integrating porphyrins into the POS (Polyporin-Based Photocatalyst) framework in ion-pair form provides a novel design strategy for constructing high-performance porphyrin-based photocatalysts. On one hand, the ion bonding method is mild and efficient, preserving the optical and catalytic properties of the porphyrins themselves to the greatest extent. On the other hand, the dynamic ionic environment of POSs may facilitate the diffusion and mass transfer of reactants / products, and their tunable pores and surface charges can also help optimize the catalytic reaction pathway. More importantly, by selecting matching organic acid pairing units, the band structure, charge separation efficiency, and surface hydrophilicity / hydrophobicity of the composite material can be systematically controlled, thereby improving its photocatalytic performance. To date, no studies have reported the application of porous organic salts based on porphyrins and naphthalene disulfonic acid in the photocatalytic oxidative coupling reaction of benzylamine. Naphthalene disulfonic acid is inexpensive and readily available, and its rigid planar structure and sulfonic acid groups are conducive to the formation of a stable porous ionic network. Therefore, designing and synthesizing a porphyrin-based porous organic salt (Por-POS) that is self-assembled through simple acid-base neutralization using an amino-functionalized porphyrin as a base and 1,5-naphthalenedisulfonic acid as an acid, and exploring its performance in catalyzing the oxidative coupling of benzylamine under visible light (especially blue light), not only helps to expand the application of POS materials in the field of photocatalysis, but also provides a new idea and material platform for developing novel, efficient, and stable heterogeneous porphyrin-based photocatalysts, which has important scientific significance and potential application prospects. Summary of the Invention

[0006] The present invention aims to provide a porphyrin-based porous organic salt (Por-POS), its preparation method, and its photocatalytic application. This method involves a simple preparation process, requiring only a one-step charge-assisted hydrogen bond self-assembly reaction to obtain the target material. The prepared material, when used as a heterogeneous photocatalyst in the photocatalytic oxidative coupling reaction of benzylamine, exhibits excellent photocatalytic activity.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a functionalized porphyrin-based porous organic salt, Por-POS, whose chemical structural formula is shown in Formula 3:

[0008]

[0009] Formula 1 The 5,10,15,20-tetra(4-aminophenyl)-21H,23H-porphyrin shown is used as an organic base, in combination with formula 2 The porphyrin-based porous organic salt Por-POS was synthesized by using 1,5-naphthalenedisulfonic acid as an organic acid via a charge-assisted hydrogen bond self-assembly reaction.

[0010] Furthermore, the preparation method specifically includes the following steps:

[0011] S1: Dissolve 5,10,15,20-tetrakis(4-aminophenyl)-21H,23H-porphyrin as shown in Formula 1 in the organic solvent N,N-dimethylformamide (DMF) and stir until completely dissolved to obtain homogeneous solution 1;

[0012] S2: Dissolve the 1,5-naphthalenedisulfonic acid shown in Formula 2 in the organic solvent DMF and stir until completely dissolved to obtain homogeneous solution 2;

[0013] S3: Mix the homogeneous solution 1 obtained in step S1 with the homogeneous solution 2 obtained in step S2, place them in a reaction vessel, and carry out an acid-base neutralization reaction at a certain temperature; after the reaction is completed, filter, wash and dry to obtain the porphyrin-based porous organic salt Por-POS.

[0014] Preferably, in step S3, the molar ratio between 5,10,15,20-tetra(4-aminophenyl)-21H,23H-porphyrin shown in Formula 1 and 1,5-naphthalenedisulfonic acid shown in Formula 2 is 1:2.

[0015] Preferably, in step S3, the reaction temperature is 80 ℃ and the reaction time is 12 hours.

[0016] This invention also provides the application of the above-mentioned porphyrin-based porous organic salt Por-POS in the photocatalytic oxidative coupling reaction of benzylamine.

[0017] Furthermore, the specific method of the application is as follows: using benzylamine or its derivatives as the reaction substrate, using the Por-POS as the heterogeneous photocatalyst, and using blue LEDs as the light source in an atmospheric pressure air atmosphere, a photocatalytic reaction is carried out at room temperature to prepare the corresponding imine compounds.

[0018] The general structural formula of the benzylamine or its derivatives is: R is selected from hydrogen, methyl, methoxy, fluorine, chloro, bromo, tert-butyl, or trifluoromethyl.

[0019] In summary, this invention successfully prepared the photoactive porphyrin-based porous organic salt Por-POS using a simple one-step charge-assisted hydrogen bond self-assembly strategy. This material integrates abundant ionic sites, porphyrin photoactive centers, and the synergistic effect of aromatic rings. Experiments show that Por-POS prepared at 80 °C can efficiently catalyze the blue light-driven oxidative coupling reaction of benzylamine under mild conditions of room temperature and atmospheric pressure, generating the target imine product, exhibiting excellent heterogeneous photocatalytic performance. Therefore, this invention develops a novel heterogeneous photocatalytic system based on Por-POS, which can achieve the efficient and green conversion of benzylamine compounds to imines under blue light irradiation and air atmosphere.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) The synthesis process is simple and efficient: The preparation method of the present invention adopts a one-step synthesis strategy, with mild reaction conditions, simple operation, no need for complex equipment or post-processing, and has good potential for industrial scale-up.

[0022] (2) Excellent photocatalyst structure and function: Photoactive porphyrin units were successfully introduced into the porous ionic framework through a clever charge-assisted hydrogen bond self-assembly strategy. The prepared Por-POS has abundant ionic functional sites, efficient porphyrin photosensitizing centers and synergistic effects generated by π-π aromatic ring stacking, thus endowing it with excellent photocatalytic activity.

[0023] (3) Outstanding photocatalytic performance and practicality: The Por-POS photocatalyst prepared in this invention exhibits high activity and high selectivity for the blue light-driven photocatalytic oxidative coupling reaction of benzylamine under normal temperature and pressure conditions. At the same time, the catalyst is a solid multiphase material, which can be easily separated and recovered from the reaction system by simple centrifugation or filtration, meeting the requirements of green chemistry and sustainable chemistry. Attached Figure Description

[0024] Figure 1 The following are the Fourier Transform Infrared (FTIR) and X-ray Photoelectron Spectroscopy (XPS) spectra of the raw materials 5,10,15,20-tetra(4-aminophenyl)-21H,23H-porphyrin (TAPP), 1,5-naphthalenedisulfonic acid (NDSA), and the prepared Por-POS, as shown in Example 1. (A) FTIR spectrum, (B) XPS full spectrum, (C) C 1s, (D) N 1s, (E) O 1s, and (F) S 2p.

[0025] Figure 2The X-ray powder diffraction (XRD) spectra of the raw material TAPP and the prepared Por-POS in Example 1 are shown below.

[0026] Figure 3 The images are scanning electron microscope (SEM) images of the Por-POS prepared in Example 1, (A) a 2.5 μm SEM image and (B) a 500 nm SEM image;

[0027] Figure 4 The Por-POS prepared in Example 1 is shown in the measured N2 adsorption-desorption isotherm and the pore size distribution obtained based on the nonlocal density functional theory (NLDFT) model: (A) N2 adsorption-desorption isotherm and (B) NLDFT pore size distribution curve.

[0028] Figure 5 The images show the UV-Vis absorption spectra of the raw materials TAPP, NDSA, and the prepared Por-POS in Example 1, and the Tauc plots obtained by linear fitting using the Kubelka-Munk function and optical band gap. (A) UV-Vis spectrum and (B) Tauc plot. (C) XPS valence band spectrum of Por-POS; (D) band structure of Por-POS.

[0029] Figure 6 The photocurrent density response and impedance spectrum represented by the Nyquist plot of the Por-POS prepared in Example 1 are shown, where (A) is the photocurrent density response and (B) is the impedance spectrum.

[0030] Figure 7 This study investigates the substrate applicability of the Por-POS prepared in Example 1 to the photocatalytic oxidative coupling reaction of benzylamine. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to the embodiments.

[0032] Example 1: Preparation of Por-POS, a porphyrin-based porous organic salt

[0033] Synthesis route:

[0034]

[0035] The starting materials 5,10,15,20-tetratetra(4-aminophenyl)-21H,23H-porphyrin (TAPP, 0.1 mmol, 0.0675 g) and 1,5-naphthalenedisulfonic acid (NDSA, 0.2 mmol, 0.0675 g) were dissolved separately in 5 mL of DMF. The two solutions were mixed and transferred to a 50 mL reaction tube, and stirred at room temperature for 20 minutes. Subsequently, the reaction system was placed at 80 °C for 12 hours. After the reaction was completed, the resulting precipitate was dispersed in 20 mL of trifluoroethanol (CF3CH2OH) and stirred for 2 hours. The solid was collected by vacuum filtration and washed thoroughly with DMF and ethanol successively. Finally, the solid was dried in a vacuum drying oven at 80 °C for 12 hours to obtain the target product, porphyrin-based porous organic salt Por-POS.

[0036] Structural and compositional characterization:

[0037] Figure 1 A shows the infrared spectra of the raw materials TAPP, NDSA, and the prepared Por-POS used in Example 1. The figure shows that the Por-POS material at 1640 cm⁻¹... −1 and 3478~3314 cm −1 The characteristic infrared peaks at 3478 and 3314 cm⁻¹ are attributed to the stretching vibrations of the C−N bond and the primary amine N−H in TAPP. These peaks were observed in Por-POS. −1 The absorption band at this point broadens and splits, which is attributed to the formation of ammonium ions (−NH3⁺) and sulfonate ions (−SO3⁻). − The interactions between the groups, and the hydrogen bonding between the unprotonated amine group (−NH2) and water molecules or sulfonic acid groups. Furthermore, at 1030, 793, and 590 cm⁻¹... − The characteristic peak observed at ¹ corresponds to the asymmetric and symmetric stretching vibrations of the sulfonic acid group. The evolution of the above spectral characteristics confirms the successful reaction between TAPP and NDSA to generate the target product Por-POS.

[0038] Figure 1 B is the Por-POS XPS full spectrum, and its elemental quantitative analysis results show the atomic percentages as follows: C (81.99 at%), N (7.42 at%), O (10.59 at%), and S (2.26 at%). C 1s fine spectrum ( Figure 1 C) can be fitted to three peaks, with binding energies at 284.3 eV (C−C / C=C), 285.0 eV (CN / C=N), and 286.0 eV (C=O), respectively. The C−N / C=N peak originates from the connection between the aromatic benzene ring and the amino group, as well as the intrinsic structure of the porphyrin skeleton. In the N 1s fine spectrum ( Figure 1D), four characteristic peaks were observed, corresponding to binding energies of 398.9 eV (pyrrole nitrogen, Pyr-N), 399.6 eV (neutral amino group, −NH2), 400.3 eV (NH on the pyrrole ring, Pyr−NH), and 401.9 eV (protonated ammonium cation, −NH3⁺). Quantitative analysis showed that the molar ratio of −NH2 to −NH3⁺ was approximately 3:1, confirming their coexistence in the material Por-POS. Based on this, it was calculated that approximately 34% of the −NH2 groups in the TAPP molecules bind to the −SO3 derived from NDSA. − Protonation occurs through the formation of ion pairs; the remaining -NH2 groups then form a hydrogen bond network with the unreacted -SO3H groups. O 1s fine spectrum ( Figure 1 E) exhibits characteristic peaks at 531.1 eV (−S−O) and 532.3 eV (−S=O), while the O−H signal present in the spectrum can be partially attributed to adsorbed water and intramolecular hydrogen bonds. S2p fine spectrum ( Figure 1 F) at 167.8 eV (S 2p) 3 / 2 ) and 169.0 eV (S 2p 1 / 2 The double peak at () is attributed to the -SO3⁻ anion and the residual -SO3H group. Based on the above spectral analysis, it can be seen that two main intermolecular interactions exist simultaneously in Por-POS: one is a strong ionic bond formed by the acid-base neutralization of -SO3⁻ and -NH3⁺; the other is a hydrogen bond formed between -SO3H and -NH2. This "charge-assisted hydrogen bond" exhibits highly ionized characteristics, combining the orientation of hydrogen bonds with the strength of ionic bonds, thus significantly enhancing the stability and rigidity of the framework.

[0039] Figure 2 The images show the X-ray powder diffraction (XRD) spectra of the raw material TAPP used in Example 1 and the prepared Por-POS. The precursor TAPP exhibits a sharp crystalline diffraction peak at 20.0°, accompanied by broadened diffraction peaks at 26.2°, 32.9°, and 50.9°. In contrast, Por-POS still shows corresponding broadened diffraction characteristics near 26.2°, 32.9°, and 50.9°, but the sharp crystalline diffraction peaks in the monomer have essentially disappeared. These results indicate that TAPP and NDSA underwent significant structural reorganization through self-assembly, and the resulting Por-POS is primarily an amorphous structure while retaining a certain degree of short-range order.

[0040] Figure 3 The images show scanning electron microscopy (SEM) images of Por-POS, revealing a loose morphology of tightly packed nanoparticles with a clearly visible porous structure. The porosity of Por-POS was characterized by N₂ adsorption-desorption tests at 77 K. Figure 4As shown in Figure A, Por-POS exhibits a type-IV adsorption isotherm and shows an obvious adsorption hysteresis loop and significant N2 absorption in the high-pressure region (0.80 < P / P0 < 0.99), indicating the presence of abundant mesoporous structures in the material. The BET specific surface area of Por-POS is 15 m 2 g −1 . The pore size distribution calculated based on the NLDFT model ( Figure 4 Figure B) shows that the pore size of Por-POS is mainly concentrated in the mesoporous range of 2.44 - 3.22 nm, which is consistent with the characteristics of the type-IV adsorption isotherm.

[0041] Figure 5 Figure A compares the ultraviolet-visible-near infrared absorption spectra of the raw materials TAPP, NDSA, and Por-POS. Due to the characteristics of the large π-conjugated system of porphyrin, TAPP shows strong absorption in the visible light region (450 - 800 nm); NDSA also has certain absorption in the same region due to the conjugated structure of its naphthalene ring, but the intensity is significantly lower than that of TAPP. Por-POS formed by their self-assembly shows a strong and broad absorption characteristic in the visible light region, which results from the conjugated extension effect generated by the intermolecular interaction between porphyrin and naphthalene ring, thus significantly improving the absorption and utilization efficiency of Por-POS for visible light. According to the Kubelka-Munk formula and the Tauc plot method ( Figure 5 Figure B), the optical band gaps (E g ) of TAPP, NDSA, and Por-POS are calculated to be 1.31 eV, 3.08 eV, and 2.83 eV, respectively. Combining with the analysis of the XPS valence band spectrum ( Figure 5 Figure C), the valence band maximum (VBM) of Por-POS is measured to be 1.05 eV, and the potential relative to the standard hydrogen electrode (NHE) is 0.81 eV. According to the energy band matching formula (E CB = E VB (vs. NHE) - E g ), the conduction band minimum (CBM) potential of Por-POS is -2.02 eV. As shown in Figure 5 Figure D, this conduction band position is much more negative than the reduction potential (-0.33 eV vs. NHE) for the reduction of oxygen to generate superoxide radicals (O2 •− ), which thermodynamically proves that Por-POS has the ability to drive the photocatalytic oxygen reduction reaction. Por-POS has both a broad visible light absorption range and a suitable optical band gap, which endows it with good visible light capture ability and semiconductor characteristics, laying a foundation for its photocatalytic applications. Further, the photogenerated charge behavior of the Por-POS material is evaluated by photoelectrochemical tests. The transient photocurrent response test ( Figure 6A) shows that Por-POS exhibits a more significant and stable photocurrent response than TAPP and NDSA in all five on-off photocycles, indicating that it has a more efficient separation and migration of photogenerated carriers. Nyquist plot of electrochemical impedance spectroscopy (…) Figure 6 B) indicates that the impedance radius of Por-POS is smaller than that of the two raw materials, TAPP and NDSA, suggesting lower charge transfer resistance and superior interfacial charge transport kinetics. These results collectively demonstrate that Por-POS, a charged porous organic salt with an extended π-conjugated system formed by assembling TAPP and NDSA, can effectively promote the separation and transport of photogenerated electron-hole pairs, which is the key reason for its excellent photocatalytic performance.

[0042] Example 2: Comparison of catalytic performance and reusability of photocatalytic benzylamine oxidative coupling reaction

[0043] The Por-POS catalyst prepared in Example 1 was applied to the blue light photocatalytic coupling reaction of benzylamine. The specific experimental procedure is as follows: Benzylamine (0.5 mmol, 53.5 mg) and the Por-POS catalyst prepared in Example 1 (5 mg) were added sequentially to a 20 mL glass reaction tube. The reaction was carried out under 5 W blue LED irradiation, with the system kept in contact with air to provide the oxygen required for the reaction. The reaction mixture was continuously stirred at 500 r / min at room temperature. After the reaction was completed, an appropriate amount of deuterated chloroform (CDCl3) was added directly to the system, stirred for 0.5 hours, filtered, and the CDCl3 filtrate containing the product was collected. 1 ¹H NMR spectroscopy determined the conversion and selectivity of the product. The solid catalyst after reaction was washed with ethyl acetate, dried under vacuum, and then directly used in the next catalytic cycle.

[0044] Table 1 shows the performance of the photocatalytic benzylamine oxidative coupling reaction under a blue LED light source. The photocatalyst Por-POS exhibited excellent catalytic performance, achieving a conversion rate of 99% and a selectivity of 98% for the target imine within 2.5 hours of illumination (Table 1, No. 1), indicating its superior photocatalytic activity. In contrast, under the same conditions, the conversion rate was 70% (No. 2) when using TAPP as the catalyst, showing moderate activity; and the conversion rate of benzylamine was only 9% (No. 3) when using NDSA as the catalyst, indicating weaker photocatalytic activity. To further explore the synergistic effect, TAPP and NDSA were physically mixed according to the mass ratio of the raw materials used in the synthesis of Por-POS (No. 4), and this mixture was used as a catalyst. Under the same reaction conditions, the conversion rate of the target imine also reached 99%, with a selectivity of 99%. This result confirms that even a physical mixture can effectively promote photocatalytic performance, mainly due to the synergistic effect of the porphyrin photosensitizing center and the acidic site simultaneously present in the system. Control experiments showed that benzylamine did not transform without the addition of a catalyst or without light irradiation (numbers 5 and 6), proving that both the photocatalyst and the blue light source are essential conditions for the reaction. Combining structural characterization and photoelectric performance analysis, the excellent photocatalytic performance of Por-POS can be attributed to its unique structural advantages: abundant ion sites and porphyrin photoactive centers construct a highly efficient reaction interface; the conjugated extension effect between porphyrin and the naphthalene ring significantly enhances visible light absorption; and charge-assisted hydrogen bonds and ion interactions effectively promote the separation and migration of photogenerated carriers.

[0045] Table 1. Photocatalytic oxidative coupling reaction of benzylamine by photocatalysts Por-POS, TAPP, and NDSA under different conditions.

[0046] Serial Number catalyst light source Time (h) Conversion rate (%) Selectivity (%) 1 Por-POS Blue LEDs 2.5 99 98 2 TAPP Blue LEDs 2.5 70 99 3 NDSA Blue LEDs 2.5 9 99 4 <![CDATA[TAPP +NDSA a ]]> Blue LEDs 2.5 99 99 5 None Blue LEDs 2.5 - - 6 Por-POS dark 2.5 - -

[0047] Reaction conditions: benzylamine (0.5 mmol), photocatalyst (5 mg), blue LEDs (5 W), solvent-free, room temperature, air atmosphere (1 atm), reaction time 2.5 h. a The mass of TAPP is 2.69 mg, and the mass of NDSA is 2.31 mg.

[0048] To evaluate the catalyst's stability, the reacted Por-POS catalyst was washed, dried, and directly used in subsequent cyclic experiments. The results showed that Por-POS maintained high catalytic activity for the benzylamine oxidative coupling reaction (conversion rate of 95% in the fifth cycle) and the product selectivity remained essentially unchanged throughout five consecutive cycles. This indicates that the catalyst possesses good structural stability and reusability, validating its practical potential as a heterogeneous photocatalyst.

[0049] Table 2. Recyclability of Por-POS in benzylamine photocatalytic oxidation coupling

[0050] Number of times to reuse Time (h) Conversion rate (%) Selectivity (%) 1 2.5 99 98 2 2.5 98 98 3 2.5 96 99 4 2.5 95 99 5 2.5 95 99

[0051] Reaction conditions: benzylamine (0.5 mmol), photocatalyst Por-POS (5 mg), blue LEDs (5 W), solvent-free, room temperature, air atmosphere (1 atm), reaction time 2.5 h.

[0052] Example 3: Substrate suitability of the catalyst Por-POS

[0053] In this example, the Por-POS catalyst prepared in Example 1 was used as the catalyst, and a series of benzylamine derivatives with different substituents were selected as substrates for photocatalytic oxidative coupling reactions under the same reaction conditions. Specific substrates included: 4-methylbenzylamine, 4-methoxybenzylamine, 4-fluorobenzylamine, 4-chlorobenzylamine, 4-bromobenzylamine, 4-tert-butylbenzylamine, and 4-trifluoromethylbenzylamine. The reaction conditions were basically the same as in Example 2, except that the reaction time (2.5 h–4 h) was optimized for different substrates to evaluate the catalytic performance of the catalyst for benzylamines with different structures. The photocatalytic performance results are as follows: Figure 7 As shown, Por-POS exhibits excellent catalytic performance and substrate suitability for benzylamine and various substituted benzylamines (1a-1h), with catalytic conversion (C) reaching 98%–99% and selectivity (S) of 97%–99%. The reaction yields the corresponding imine compounds, the structures of which were confirmed by 1H NMR spectroscopy (¹H NMR). Specific NMR data are as follows:

[0054] N-Benzyl-1-phenylmethylamine (2a) 1 H NMR (400 MHz, CDCl3): δ=8.47 (s, 1H), 7.87~7.85 (d, 2H), 7.50~7.48 (m, 3H), 7.43~7.34(m, 5H), 4.90 ppm (s, 2H).

[0055] N-(4-methylbenzyl)-1-(4-methylbenzyl)methylamine (2b) 1 H NMR (400 MHz, CDCl3): δ=8.42(s, 1H), 7.77~7.75 (d, 2H), 7.32~7.31 (d, 2H), 7.29~7.25 (d, 2H), 7.23 (d,2H), 4.86 (s, 2H), 2.46 (s, 3H), 2.42 ppm (s, 3H).

[0056] N-(4-methoxybenzyl)-1-(4-methoxyphenyl)methylamine (2c) 1 H NMR (400 MHz, CDCl3): δ=8.35 (s, 1H), 7.79~7.76 (d, 2H), 7.31~7.30 (d, 2H), 6.99~6.97 (d, 2H), 6.95~6.93 (d, 2H), 4.78 (s, 2H), 3.89~3.85 ppm (d, 6H).

[0057] N-(4-fluorobenzyl)-1-(4-fluorophenyl)-methylamine (2d) 1 H NMR (400 MHz, CDCl3): δ=8.34 (s,1H), 7.79~7.77 (m, 2H), 7.30~7.28 (m, 2H), 7.12~7.10 (t, 2H), 7.05~7.04 (t,2H), 4.77 ppm (s, 2H).

[0058] N-(4-chlorobenzyl)-1-(4-chlorophenyl)methylamine (2e) 1 H NMR (400 MHz, CDCl3): δ=8.45 (s,1H), 7.77~7.76 (d, 2H), 7.45~7.44 (d, 2H), 7.38~7.36 (d, 2H), 7.33~7.31 (d,2H), 4.82 ppm (s, 2H).

[0059] N-(4-bromobenzyl)-1-(4-bromophenyl)methylamine (2f) 1 H NMR (400 MHz, CDCl3): δ= 8.32 (s,1H), 7.65~7.63 (d, 2H), 7.56~7.51 (d, 2H), 7.48~7.46 (t, 2H), 7.22~7.20 (t,2H), 4.74 ppm (s, 2H).

[0060] N-(4-(tert-butyl)benzyl)-1-(4-(tert-butyl)phenyl)methylamine (2g) 1H NMR (400 MHz, CDCl3): δ=8.46 (s, 1H), 7.83~7.81 (d, 2H), 7.54~7.52 (d, 2H), 7.47~7.45 (d, 2H), 7.37~7.35 (d, 2H), 4.88 (s, 2H), 1.42~1.41 ppm (d, 18H).

[0061] N-(4-trifluoromethylbenzyl)-1-(4-trifluoromethylphenyl)methylamine (2h) 1 H NMR (400 MHz, CDCl3): δ=8.42 (s, 1H), 7.92~7.90 (d, 2H), 7.70~7.68(d, 2H), 7.62~7.60 (d, 2H), 7.48~7.46 (d, 2H), 4.90 ppm (s, 2H).

Claims

1. A porphyrin-based porous organic salt, characterized in that, It is a porous organic salt material formed by charge-assisted hydrogen bonding self-assembly and acid-base neutralization, named Por-POS, and its chemical structure is shown in Formula 3.

2. A method for preparing the porphyrin-based porous organic salt according to claim 1, characterized in that, Includes the following steps: Using 5,10,15,20-tetra(4-aminophenyl)-21H,23H-porphyrin (Formula 1) and 1,5-naphthalenedisulfonic acid (Formula 2) as raw materials, the porphyrin-based porous organic salt material Por-POS was synthesized through charge-assisted hydrogen bonding self-assembly and acid-base neutralization reaction. The structural formula of 5,10,15,20-tetra(4-aminophenyl)-21H,23H-porphyrin (Formula 1) is as follows: The structural formula of 1,5-naphthalenedisulfonic acid shown in Formula 2 is as follows: .

3. The preparation method according to claim 2, characterized in that, Specifically, the following steps are included: S1: Add the 5,10,15,20-tetra(4-aminophenyl)-21H,23H-porphyrin shown in Formula 1 to a container containing the organic solvent N,N-dimethylformamide, and stir until it is completely dissolved to obtain a homogeneous solution 1. S2: Add the 1,5-naphthalenedisulfonic acid shown in Formula 2 to a container containing N,N-dimethylformamide, stir until it is completely dissolved, and obtain a homogeneous solution 2; S3: Mix the homogeneous solution 1 and the homogeneous solution 2, place them in a reaction vessel, and carry out an acid-base neutralization reaction at a certain temperature. After the reaction is completed, wash, filter and dry to obtain the porphyrin-based porous organic salt Por-POS.

4. The preparation method according to claim 3, characterized in that, In step S3, the molar ratio of 5,10,15,20-tetra(4-aminophenyl)-21H,23H-porphyrin represented by Formula 1 to 1,5-naphthalenedisulfonic acid represented by Formula 2 is 1:

2.

5. The preparation method according to claim 3, characterized in that, In step S3, the reaction temperature is 80°C. o C, the reaction time is 12 hours.

6. The application of the porphyrin-based porous organic salt according to claim 1 in the photocatalytic benzylamine coupling reaction.

7. The application according to claim 6, characterized in that, Specifically, it includes: Using benzylamine as the reaction substrate and the Por-POS described in claim 1 as the heterogeneous photocatalyst, a photocatalytic benzylamine coupling reaction was carried out at room temperature under normal pressure air atmosphere and blue LED irradiation to prepare the corresponding imine compound.

8. The application according to claim 7, characterized in that, The general structural formula of the benzylamine or its derivatives is: R is selected from any one of hydrogen, methyl, methoxy, fluoro, chloro, bromo, tert-butyl, and trifluoromethyl.

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