Three-dimensional covalent organic framework material for photocatalysis and preparation method thereof

Abstract

The invention discloses a three-dimensional covalent organic framework material for photocatalysis and a preparation method thereof, and relates to the field of covalent organic framework compounds, and the novel three-dimensional covalent organic framework material is prepared by adjusting the steric hindrance of an intermediate in a polycondensation process to control the formation of 3D COFs. The compound is formed by connecting an octa-aldehyde porphyrin compound and p-diamino polyphenyl through a condensation reaction, and contains a porphyrin unit, so that the compound belongs to a photosensitizer, can catalyze oxygen to generate singlet oxygen (1O2), and has a better application prospect in the field of catalysis after being coordinated with metal, such as hydrogen production through water photolysis, carbon dioxide reduction and the like. According to the preparation method provided by the invention, the growth of the framework can be influenced through predesignable, reorientable and self-adaptive intermediates, and meanwhile, the intermediates can be further regarded as new precursors participating in stereo conformation adjustment and stabilization.

Description

Technical Field

[0001] The present invention relates to the field of covalent organic framework compounds, and specifically to a three-dimensional covalent organic framework material for photocatalysis and a preparation method thereof. Background Art

[0002] Three-dimensional covalent organic frameworks (3D COFs) have unique pore structures and better material adsorption and transport capabilities compared to two-dimensional covalent organic frameworks (2D COFs), making them ideal materials in application fields such as catalysis, separation, and molecular recognition. However, the development of 3D COFs lags far behind that of 2D COFs and other three-dimensional framework materials, largely due to bottlenecks in aspects such as the design, synthesis, and precise structure analysis of the building units involved in forming COFs. To overcome these obstacles, it is crucial to continuously explore new precursors for 3D COF topologies and their related physical and chemical properties.

[0003] Since Yaghi et al. first proposed 3D COFs more than a decade ago, the significant progress in this field has mainly relied on polyhedral precursors, which can be divided into three categories: (1) tetrahedral precursors centered on carbon, silicon, adamantane, twisted biphenyl, woven units, etc.; (2) triangular prismatic precursors centered on cages or triptycene; (3) planar twisted structures centered on benzene, biphenyl, pyrene, and porphyrin. These precursor nodes with inherent three-dimensional structures only lead to polymerization in three-dimensional space, thereby forming covalent organic frameworks with three-dimensional structures. Recently, multi-node planar precursors have also been utilized, but only for specific unit combinations or reactions. For example, 3-connected triangular units and 4-connected square units used to construct ffc or tbo topologies, 4-connected D 4h units and 6-connected D 3h units, as well as bifunctional units carrying boric acid and phosphoric acid groups, which form 8-connected polycubanes through self-condensation. To date, the reported 3D COF topologies include dia, pts, ctn, bor, lon, lij, qtz, stp, acs, ceq, hea, pcu, scu, tty, pcb, she, bcu, flu, rra, srs, nbo, ffc, tbo, fjh, pto, mhq-z, lnj, sqc, and alb-3,6-Ccc2.

[0004] Compared with the number of topologies of three-dimensional metal-organic frameworks, the number of topologies of three-dimensional covalent organic frameworks that have been discovered is still very limited. This indicates that it is urgent to expand the precursor molecular library and the types of synthesis mechanisms of three-dimensional covalent organic frameworks. Summary of the Invention

[0005] In view of the above deficiencies of the prior art, the present invention provides a three-dimensional covalent organic framework material for photocatalysis and a preparation method thereof.

[0006] To achieve the above invention object, the technical solution adopted by the present invention is as follows:

[0007] Provide a three-dimensional covalent organic framework material for photocatalysis, which is composed of an octa-aldehyde porphyrin compound shown in Formula I and p-diaminobiphenyl connected by a condensation reaction; the biphenyl in p-diaminobiphenyl is composed of two or more benzene rings linearly connected; its structural general formula is shown in Formula II;

[0008]

[0009] Wherein i is the number of linearly connected benzene rings, and i≥2.

[0010] The present invention also provides a preparation method of the above three-dimensional covalent organic framework material for photocatalysis, including the following specific steps:

[0011] S1: Dissolve the octa-aldehyde porphyrin compound and p-diaminobiphenyl in a solvent, add the catalyst acetic acid and mix evenly;

[0012] S2: React the mixed solution at 120 °C for 72 h;

[0013] S3: Filter to obtain the reaction product, wash it successively with N,N-dimethylformamide and acetone, and dry it to obtain the three-dimensional covalent organic framework material.

[0014] Further, the molar ratio of the octa-aldehyde porphyrin compound to p-diaminobiphenyl is 1:4.

[0015] Further, the solvent is a mixed solvent of o-dichlorobenzene and n-butanol, and the volume ratio of o-dichlorobenzene to n-butanol is 1:1; the catalyst is a 6M acetic acid solution, and the volume ratio of the acetic acid solution to the solvent is 1:10.

[0016] Further, the dosage ratio of the solvent to the octa-aldehyde porphyrin compound is 1 mL:0.02 mmol.

[0017] Further, between step S1 and S2, it also includes: freezing and degassing the mixed solution, and heating the mixed solution to 120 °C in a vacuum-sealed environment.

[0018] The present invention also provides a three-dimensional covalent organic framework material for photocatalysis, as shown in Formula III, which is composed of an octa-aldehyde porphyrin compound and benzidine connected by a condensation reaction;

[0019]

[0020] The present invention also provides a three-dimensional covalent organic framework material for photocatalysis, as shown in Formula IV, which is composed of an octaaldehyde porphyrin compound and 4,4'-diamino-p-terphenyl connected by a condensation reaction;

[0021]

[0022] The beneficial effects of the present invention are:

[0023] The present invention prepares a new three-dimensional covalent organic framework material by adjusting the steric hindrance of the intermediate in the polycondensation process to control the formation of 3D COFs. The compound is composed of an octaaldehyde porphyrin compound and a p-diamino polyphenyl connected by a condensation reaction. It contains a porphyrin unit and is therefore a photosensitizer that can catalyze oxygen to generate singlet oxygen ( 1 O2), in addition, it has good application prospects in the field of catalysis after coordination with metals, such as photolysis of water to produce hydrogen, carbon dioxide reduction, etc.

[0024] The preparation method provided by this invention can influence the growth of the framework through pre-designed, re-directable, and adaptive intermediates. Simultaneously, these intermediates can be further viewed as new precursors involved in the adjustment and stabilization of the three-dimensional conformation. This allows for the control of the structure of three-dimensional covalent organic framework materials and, further, the material's properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 : This is a comparison chart of the experimental PXRD data of BNU-1, BNU-2 and BNU-3 in Example 4;

[0026] Figure 2 4 is a comparison diagram of the experimental PXRD data and the theoretical XRD data in Example 4;

[0027] Figure 3 The SEM and TEM images of BNU-2 and BNU-3 in Example 4 are shown;

[0028] Figure 4 N2 isothermal adsorption-desorption curves and pore size distribution diagrams of BNU-2 and BNU-3 in Example 5;

[0029] Figure 5 Thermogravimetric curves of BNU-2 and BNU-3 in Example 5;

[0030] Figure 6 This is the photocatalytic performance diagram in Example 6. DETAILED DESCRIPTION

[0031] The specific embodiments of the present invention will be described below to facilitate those skilled in the art of this technology to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art of this technology, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concept of the present invention are within the scope of protection.

[0032] The octaaldehyde porphyrin compound was purchased from Beijing Innochem Science & Technology Co., Ltd., and the rest of the raw material reagents were all conventional analytical pure commercially available materials.

[0033] Example 1 Preparation of a three-dimensional covalent organic framework material as shown in Formula III

[0034] The following specific method was adopted:

[0035] S1: Add 0.02 mmol of octaaldehyde porphyrin compound, 0.08 mmol of benzidine, 0.5 mL of 1,2-dichlorobenzene, 0.5 mL of n-butanol, and 0.1 mL of acetic acid aqueous solution with a concentration of 6 M into a pressure-resistant glass tube with an outer diameter of 10 mm and an inner diameter of 7 mm; ultrasonically mix all the raw materials evenly for 10 min; after mixing evenly, quickly freeze the tube in liquid nitrogen. After exhausting for 5 minutes, seal the glass tube at a position 4 cm from the tube mouth;

[0036] S2: Place the sealed glass tube in an oven at 120 °C and heat for 72 h;

[0037] S3: Filter to obtain the reaction product, wash it successively with N,N-dimethylformamide and acetone for a total of three times, and dry it in vacuo to obtain a solid, which is named BNU-2.

[0038] Example 2 Preparation of a three-dimensional covalent organic framework material as shown in Formula IV

[0039] The difference between this example and Example 1 is that benzidine is replaced with a linear linker 4,4'-diaminoterphenyl with three benzene rings, and the obtained solid is named BNU-3.

[0040] Example 3

[0041] The difference between this example and Example 1 is that benzidine is replaced with a linear linker p-phenylenediamine with one benzene ring, and the obtained solid is named BNU-1.

[0042] Example 4

[0043] Respectively take the solid products prepared in Examples 1 to 3, and use a powder X-ray diffractometer to perform powder X-ray diffraction (PXRD) to characterize their crystal structures. The test conditions are CuKα source The range of 2θ is from 2° to 40°, with a step size of 0.02°, and each step takes 1 s at room temperature. The structure was analyzed using Materials Studio software. The results are as Figure 1 shown. It can be seen from Figure 1 that the BNU-2 material prepared in Example 1 has an obvious diffraction peak at 3.82°, and relatively weak peaks at 5.46°, 7.79°, 8.74° and 11.65°. The BNU-3 material prepared in Example 2 has a strong diffraction peak at 3.17°, and weak diffraction peaks at 4.39°, 7.33° and 9.91°. However, the BNU-1 material prepared in Example 3 has no strong diffraction peak.

[0044] The experimental PXRD data (Experimental) of BNU-1, BNU-2 and BNU-3 were respectively compared with the theoretical XRD data of the corresponding non-interpenetrated and doubly interpenetrated pcb topological models, as shown in Figure 2 shown, where Figure 2 a is the XRD comparison data graph of BNU-1, Figure 2 b is the XRD comparison data graph of BNU-2, Figure 2 c is the XRD comparison data graph of BNU-3; it can be seen from Figure 2 that when the number of benzene rings in the linear linker is 1, the PXRD pattern of the prepared BNU-1 does not match the 3D COFs structure, and a three-dimensional covalent organic framework material cannot be formed. When the number of benzene rings in the linear linker is 2 or 3, the PXRD patterns of the prepared BNU-2 or BNU-3 are in agreement with the theoretical prediction results, and a 3D COFs structure can be successfully prepared.

[0045] The morphologies of BNU-2 and BNU-3 were studied by scanning electron microscopy (SEM, Hitachi SU-8010) and cryogenic transmission electron microscopy (Cryo-TEM, Themis300) at 300 kV. The results are as Figure 3 shown, where Figure 3 a is the SEM image of BNU-2, Figure 3 b is the SEM image of BNU-3, Figure 3 c is the TEM image of BNU-2, Figure 3 d is the TEM image of BNU-3.

[0046] It can be seen from Figure 3 a and Figure 3 c that BNU-2 is composed of small cubes with a side length of about 50 nm. The quadrilateral arranged pores and periodic lattice fringes can be clearly observed. The pore width is 0.63 nm, which is in good agreement with the pore width (0.62 nm) of the model.

[0047] As can be seen from Figure 3 b and Figure 3 d, BNU-3 is composed of small cubes with an edge length of about 50 nm stacked together. Quadrilateral arranged pores and periodic lattice fringes can be clearly observed. The pore width is 1.13 nm, which is in good agreement with the pore width of the model (1.18 nm).

[0048] Example 5

[0049] The pore characteristics of BNU-2 and BNU-3 prepared in the above examples were studied using a fully automatic specific surface area and porosity analyzer Micromeritics ASAP2420 at 77 K by means of nitrogen adsorption-desorption isotherms. The results are as Figure 4 shown, where Figure 4 a and c are the N2 isothermal adsorption-desorption curves and pore size distribution diagrams of BNU-2 respectively, Figure 4 b and d are the N2 isothermal adsorption-desorption curves and pore size distribution diagrams of BNU-3 respectively; As can be seen from Figure 4 a and b, both BNU-2 and BNU-3 exhibit typical type I isotherms, indicating their microporous characteristics. As can be seen from Figure 4 c and d, BNU-2 / 3 exhibit pore size distributions centered at 0.64 nm and 1.18 nm respectively, which are consistent with the results from the model crystal structure (0.62 nm, 1.14 nm) and high-resolution transmission electron microscopy (0.63 nm, 1.13 nm).

[0050] Meanwhile, in an air atmosphere, the COF samples were subjected to thermogravimetric analysis (TGA) in a platinum tray at a flow rate of 40 mL / min. The instrument used was a PerkinElmer STA6000 series thermogravimetric analyzer. The temperature was raised from 25 °C to 800 °C by furnace heating at a heating rate of 5 °C / min. The results are as Figure 5 shown, where Figure 5 a is the thermogravimetric curve of BNU-2, Figure 5 b is the thermogravimetric curve of BNU-3; As can be seen from Figure 5 it, the starting decomposition temperature of BNU-2 and BNU-3 is 400 °C. This indicates that both BNU-2 and BNU-3 have good thermal stability.

[0051] Example 6

[0052] The photocatalytic production of 1 O2 performance tests were carried out on BNU-2 and BNU-3 prepared in the above examples. The specific test steps are as follows:

[0053] (1) Prepare 10 μM singlet oxygen (1 N-methylpyrrolidone solution of the O2 indicator (1,3-diphenylisobenzofuran, DPBF).

[0054] (2) Disperse 50 μg of COFs (BNU-2 or BNU-3) in 1 mL of the above N-methylpyrrolidone solution.

[0055] (3) Irradiate the solution with a 660 mm monochromatic laser (60 mW / cm 2 ) in an air atmosphere.

[0056] (4) At room temperature, record the ultraviolet-visible absorption spectrum of the solution at 417 nm every 1 min using a UV-1800 ultraviolet spectrophotometer to detect 1 the generation of O2.

[0057] At the same time, set up a control group (DPBF) without adding COFs. The results are as Figure 6 shown, where Figure 6 a is the ultraviolet-visible absorption spectrum of the control group, Figure 6 b is the ultraviolet-visible absorption spectrum with BNU-2 added, Figure 6 c is the ultraviolet-visible absorption spectrum with BNU-3 added, Figure 6 d is the comparison chart of the time-absorbance changes of the control group, BNU-2, and BNU-3; it can be Figure 6 seen that irradiating at 660 nm for 8 minutes can trigger the rapid generation of singlet oxygen by BNU-2 or BNU-3, consuming 86.6% or 99.3% of 1,3-diphenylisobenzofuran (DPBF) respectively, while without adding COFs, only 10.6% of DPBF is consumed. The ability of BNU-2 and BNU-3 to photocatalytically generate singlet oxygen far exceeds that of the 3DPor-COF formed by the tetrahedral precursor (after irradiating for 50 min, 60% of the singlet oxygen indicator is consumed), which indicates that the induction of the 3DCOF formation by the intermediate steric effect may be beneficial to the development of new photocatalysis.

Claims

1. A three-dimensional covalent organic framework material for photocatalysis, characterized in that The three-dimensional covalent organic framework material is composed of an octa-aldehyde porphyrin compound shown in Formula I and p-diaminobiphenyl connected by a condensation reaction; the biphenyl in the p-diaminobiphenyl is composed of two or more benzene rings linearly connected; its structural general formula is shown in Formula II; wherein i is the number of linearly connected benzene rings, and i≥2.

2. The preparation method of the three-dimensional covalent organic framework material for photocatalysis according to claim 1, characterized in that, It includes the following specific steps: S1: Dissolve the octa-aldehyde porphyrin compound and diaminobiphenyl in a solvent, add the catalyst acetic acid, and mix evenly; S2: React the mixed solution at 120 °C for 72 h; S3: Filter to obtain the reaction product, wash it successively with N,N-dimethylformamide and acetone, and dry it to obtain the three-dimensional covalent organic framework material.

3. The preparation method according to claim 2, characterized in that, The molar ratio of the octa-aldehyde porphyrin compound to diaminobiphenyl is 1:

4.

4. The preparation method according to claim 2, wherein The solvent is a mixed solvent of o-dichlorobenzene and n-butanol, and the volume ratio of o-dichlorobenzene to n-butanol is 1:1; the catalyst is a 6M acetic acid solution, and the volume ratio of the acetic acid solution to the solvent is 1:

10.

5. The preparation method according to claim 4, characterized in that, The dosage ratio of the solvent to the octa-aldehyde porphyrin compound is 1 mL:0.02 mmol.

6. The preparation method according to claim 2, characterized in that Between step S1 and S2, it further includes: freezing and degassing the mixed solution, and heating the mixed solution to 120 °C in a vacuum-sealed environment.

7. A three-dimensional covalent organic framework material for photocatalysis, characterized in that, The three-dimensional covalent organic framework material is shown in Formula III, and it is composed of an octa-aldehyde porphyrin compound and benzidine connected by a condensation reaction; 8. A three-dimensional covalent organic framework material for photocatalysis, characterized in that, The three-dimensional covalent organic framework material is shown in Formula IV, and it is composed of an octa-aldehyde porphyrin compound and 4,4'-diaminoterphenyl connected by a condensation reaction;

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