Metal quinoline covalent organic framework and preparation method and application thereof

Abstract

The invention belongs to the field of coordination polymers, and particularly relates to a novel metal quinoline covalent organic framework and preparation thereof, and application of the novel metal quinoline covalent organic framework in photocatalytic alkenyl carbonyl reductive cross-coupling. The invention provides various metal quinoline covalent organic frameworks. Raw materials of the metal quinoline covalent organic frameworks comprise an amino monomer, an aldehyde group-containing organic monomer, pyruvic acid and transition metal salt. The metal quinoline covalent organic framework obtained by the invention has ultralong-life excitons exceeding 8000 picoseconds, and shows excellent performance of photocatalytic alkenyl carbonyl reduction cross coupling; the method has remarkable conversion efficiency and separation yield in a wide substrate range, the highest conversion efficiency is 99%, and the catalyst has recoverability.

Description

Technical Field

[0001] This invention belongs to the field of coordination polymers, specifically relating to a novel metal quinoline covalent organic framework and its preparation method, as well as its application in photocatalytic olefin carbonyl reduction cross-coupling. Background Technology

[0002] Photocatalysis offers a promising pathway to upgrading industrial chemical manufacturing because its mild reaction conditions and low energy consumption enable more sustainable and environmentally friendly processes. A key factor determining photocatalytic performance is the efficiency of the catalyst in exciton generation, exciton separation into charge carriers, and subsequent transport to the catalytic center. Long lifetimes are often crucial for efficient exciton separation. A popular design principle for extending exciton lifetime is to construct donor-acceptor (DA) structures with spatially separated distributions between the highest occupied molecular orbitals (HOMO) and the lowest unoccupied molecular orbitals (LUMO).

[0003] As a representative example, covalent organic frameworks (COFs) are emerging crystalline porous materials with structural designability, allowing the integration of D and A moieties into their lattice to extend exciton lifetimes. Currently, the exciton lifetimes of COF-based photocatalysts range from 1 to 800 ps, ​​which is still insufficient for effective charge separation. This is because most COFs are purely organic materials, leading to the following problems: The low dielectric constant of COFs results in exciton binding energies as high as 100 to 2000 meV, while the weak coupling between the π orbitals of localized electrons leads to low charge transfer rates and increased recombination opportunities during charge separation. Furthermore, the dominant excited states of COFs are short-lived singlet excitons, along with high-energy and widely distributed charge transfer states that readily undergo nonradiative recombination. In summary, these limitations make achieving long-lived excitons in COFs for effective charge separation quite challenging.

[0004] Metal complexes have become promising material design platforms due to their unique metal-ligand charge transfer (MLCT) state. The strong coupling between the d orbitals of the metal center and the π orbitals of the ligands significantly promotes electron delocalization and lowers the exciton binding energy, thereby promoting charge separation and suppressing recombination. Therefore, incorporating metal complexes into COFs can, in principle, overcome the inherent problems of COFs and generate long-lived excitons for charge separation. For example, aromatic heterocyclic compounds quinolines have been studied for providing long-lived excitons in small-molecule organic photocatalysts. Furthermore, nitrogen atoms can coordinate with metal ions to form metal-quinoline complexes. Utilizing the MLCT state, the light absorption range of metal-quinoline complexes can be broadened from the ultraviolet region to the visible light region, and the exciton lifetime can be further extended. In addition, through the electronic regulation of quinoline ligands, metal-quinoline complexes can exhibit (quasi-)reversible multi-electron transfer pathways under illumination, providing feasibility for complex single / multi-electron photocatalytic reactions. However, reports on the incorporation of metal quinolines into COFs are scarce, with only a few works mentioning the synthesis of quinoline-based COFs. Further research on incorporating metal ions into the quinoline-based COF framework or incorporating metal-quinoline complexes into COF channels has not yet been conducted. This is because achieving metal-quinoline chelation while maintaining the COF crystal structure in highly photostable COFs is quite challenging. Once this problem is solved, it will make a significant contribution to the development of metal complex-based porous materials in the field of photocatalysis.

[0005] Here, a challenging olefin-carbonyl reduction cross-coupling reaction was completed using metal quinoline COF as a photocatalyst. This reaction not only exhibits high stability but also significant conversion efficiency across a wide range of substrates, providing new insights into the design of metal quinoline-incorporated COFs with long-lived excitons for photochemistry. Summary of the Invention

[0006] The purpose of this invention is to propose a method of pre-assembly-post-modification-in-situ chelation to construct a novel metal-quinoline covalent organic framework (M-QL-COF) through a molecular design strategy. The resulting metal-quinoline covalent organic framework has an ultralong exciton lifetime and exhibits excellent performance in catalyzing olefin-carbonyl reduction cross-coupling reactions.

[0007] The technical solution of this invention:

[0008] The first technical problem to be solved by the present invention is to provide a metal quinoline covalent organic framework, wherein the raw materials of the metal quinoline covalent organic framework include: an amino monomer, an aldehyde-containing organic monomer, pyruvate and a transition metal salt; wherein the amino monomer is 2,4,6-tris(4-aminophenyl)-1,3,5-triazine.

[0009] Furthermore, in the above-mentioned metal quinoline covalent organic framework, the aldehyde-containing organic monomer is selected from at least one of 2,5-dihydroxyterephthalaldehyde, terephthalaldehyde, or 2,5-dimethoxyterephthalaldehyde.

[0010] Furthermore, in the above-mentioned metal quinoline covalent organic framework, the transition metal salt is selected from at least one of the nitrate, sulfate, or chloride salts of transition metals.

[0011] Preferably, in the above-mentioned metal quinoline covalent organic framework, the transition metal is selected from at least one of iron, cobalt, nickel, copper, or zinc. More preferably, it is iron.

[0012] More preferably, in the above-mentioned metal quinoline covalent organic framework, the transition metal salt is selected from at least one of ferric chloride, cobalt chloride, copper chloride, nickel chloride, or zinc chloride. More preferably, it is ferric chloride.

[0013] Furthermore, in the above-mentioned metal quinoline covalent organic framework, the molar ratio of the amino monomer to the aldehyde-containing organic monomer is 1:1 to 3. Preferably, it is 1:1.5.

[0014] Furthermore, in the above-mentioned metal quinoline covalent organic framework, the molar ratio of the amino monomer to the transition metal salt is 1:1 to 5.

[0015] Preferably, in the above-mentioned metal quinoline covalent organic framework, the molar ratio of pyruvate to amino monomer is 1:1 to 10.

[0016] The second technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned metalloquinoline covalent organic framework. The preparation method includes the following steps: preparing the metalloquinoline covalent organic framework by reacting an amino monomer, an aldehyde-containing organic monomer, and a transition metal salt under the action of a catalyst.

[0017] The preparation method includes the following steps: an amino monomer and an aldehyde-containing organic monomer react under the action of a catalyst to obtain an imine covalent organic framework (imine COF); the imine COF reacts with pyruvate under the action of an oxidant to obtain a quinoline covalent organic framework (quinoline COF); and finally, it coordinates with a transition metal salt to obtain the metal quinoline covalent organic framework (M-QL-COF).

[0018] Furthermore, in the above method for preparing the metalloquinoline covalent organic framework, the catalyst is selected from at least one of acetic acid or isoquinoline. Acetic acid is preferred.

[0019] Preferably, in the above method for preparing the metal quinoline covalent organic framework, the oxidant is selected from at least one of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), tetrachlorobenzoquinone, and tetrabutylammonium iodide. Preferably, it is 2,3-dichloro-5,6-dicyano-1,4-benzoquinone.

[0020] More preferably, in the above-mentioned method for preparing the metal quinoline covalent organic framework, the molar ratio of the oxidant to the amino monomer is 1:1 to 5.

[0021] Furthermore, in the above method for preparing the metalloquinoline covalent organic framework, the reaction temperature for preparing the imine COF is 100-160℃, and the reaction time is more than 3 days.

[0022] Furthermore, in the above-mentioned method for preparing the metalloquinoline covalent organic framework, the reaction temperature for preparing the quinoline COF is 100-160℃, and the reaction time is more than 3 days.

[0023] Furthermore, in the above-mentioned method for preparing the metalloquinoline covalent organic framework, the coordination temperature is room temperature, and the time is 12 to 48 hours.

[0024] Specifically, the preparation method of the above-mentioned metal-quinoline covalent organic framework includes the following steps:

[0025] 1) Disperse amino monomers, aldehyde-containing organic monomers, and catalysts in a solvent, remove air, react at 100-160℃ under sealed conditions, cool and wash to obtain imine covalent organic frameworks;

[0026] 2) Disperse the imine covalent organic framework, pyruvate, and oxidant in a solvent, remove the air, react at 100-160℃ under sealed conditions, cool and wash to obtain the quinoline covalent organic framework;

[0027] 3) The quinoline covalent organic framework and transition metal salt are dispersed in a solvent, stirred at room temperature, and washed to obtain the metal quinoline covalent organic framework.

[0028] Preferably, in step 1) of the above-mentioned method for preparing the metalloquinoline covalent organic framework, dispersion is performed using ultrasound. The ultrasound treatment lasts for 5 to 120 seconds.

[0029] Preferably, in step 2) of the above-mentioned preparation method of the metalloquinoline covalent organic framework, dispersion is performed by ultrasonication. The ultrasonic treatment lasts for 5 to 120 seconds.

[0030] Preferably, in step 3) of the above-mentioned method for preparing the metalloquinoline covalent organic framework, dispersion is performed using ultrasound. The ultrasound treatment lasts for 5 to 120 seconds.

[0031] Preferably, in step 1) of the above-mentioned method for preparing the metal quinoline covalent organic framework, the reaction is carried out at 100 ~ 160°C for more than 3 days.

[0032] Preferably, in step 2) of the above-mentioned method for preparing the metal quinoline covalent organic framework, the reaction is carried out at 100 ~ 160°C for more than 3 days.

[0033] Preferably, in step 3) of the above-mentioned method for preparing the metal quinoline covalent organic framework, the stirring is carried out at room temperature for 12 to 48 hours.

[0034] Preferably, in step 1) of the above-mentioned method for preparing the metal quinoline covalent organic framework, the solvent is selected from at least one of n-butanol, o-dichlorobenzene, or methanol.

[0035] Preferably, in step 2) of the above-mentioned method for preparing the metal quinoline covalent organic framework, the solvent is selected from at least one of n-butanol, o-dichlorobenzene, or methanol.

[0036] Preferably, in step 3) of the above-mentioned method for preparing the metal quinoline covalent organic framework, the solvent is selected from at least one of n-butanol, o-dichlorobenzene, or methanol.

[0037] The third technical problem to be solved by the present invention is to provide the use of the above-obtained metal quinoline covalent organic framework as a catalyst in the field of photocatalysis.

[0038] The fourth technical problem to be solved by this invention is to provide the use of the above-mentioned metal quinoline covalent organic framework as a catalyst for photocatalytic olefin-carbonyl reduction cross-coupling reaction. The catalyst is a metal quinoline covalent organic framework, which is prepared by an amino monomer, an aldehyde-containing organic monomer, and a transition metal salt under the action of a catalyst; wherein the aldehyde-containing organic monomer is selected from 2,5-dihydroxyterephthalaldehyde, terephthalaldehyde, or 2,5-dimethoxyterephthalaldehyde, the transition metal salt is selected from ferric chloride, and the polynitrogen-containing amino monomer is 2,4,6-tris(4-aminophenyl)-1,3,5-triazine.

[0039] The beneficial effects of this invention are:

[0040] This invention provides a metal-quinoline covalent organic framework with ultra-long exciton lifetime, single-atom dispersion of the metal in the structure, an MN₂O₂ asymmetric coordination environment for the metal ions, and catalytic activity. The metal-quinoline covalent organic framework obtained by this invention possesses ultra-long exciton lifetimes exceeding 8000 picoseconds; it can be used as a photocatalyst and exhibits excellent photocatalytic performance in alkene-carbonyl reduction cross-coupling, demonstrating significant conversion efficiency and separation yield across a wide substrate range, with a maximum conversion efficiency of 99%, and the catalyst is recyclable. Attached Figure Description

[0041] Figure 1 Schematic diagram of the reaction of the covalent organic frameworks obtained in Examples 1, 2 and 3 of this invention.

[0042] Figure 2 Infrared spectra of the covalent organic framework samples obtained in Examples 1 and 2 of this invention; as shown in the figures, the C=O stretching vibration peak disappears in all products, and the characteristic peak of the imine bond is at 1577 cm⁻¹. −1 The presence of this feature indicates the formation of an imine bond in the reaction. Additionally, the presence of this feature at 1717 cm⁻¹ in the quinoline covalent organic framework further supports this. −1 The characteristic peak at the point is attributed to the stretching vibration of the C=O group in the carboxylic acid on the quinoline ring, confirming the conversion of imine to quinoline.

[0043] Figure 3 PXRD patterns of the covalent organic framework samples obtained in Examples 1 and 2 of this invention; a is the PXRD pattern of TAPT-DHTA-COF, and b is the PXRD pattern of QL-COF; as shown in the figure, the experimental PXRD patterns are in good agreement with the simulated patterns; the imine covalent organic framework (TAPT-DHTA-COF) shows strong peaks at 2.82°, 4.92°, 5.68° and 7.42°, corresponding to the (100), (110), (200) and (210) crystal planes, respectively. The proposed model was refined using the Pawley refinement method, and the cell parameters were obtained as follows: a = b = 36.5745 Å, c = 3.6569 Å, α = β = 90°, γ = 120°, R wp = 5.33% and R p = 4.28%. Furthermore, the experimental PXRD pattern of the quinoline covalent organic framework (QL-COF) showed good consistency with the simulated pattern, maintaining high crystallinity. Strong peaks appeared at 2.81°, 4.93°, 5.69°, and 7.42°, corresponding to the (100), (110), (200), and (210) crystal planes, respectively. The proposed model was refined using the Pawley refinement method, yielding the following cell parameters: a = b = 37.0544 Å, c = 3.5489 Å, α = β = 90°, γ = 120°, R... wp = 4.88% and R p = 3.93%.

[0044] Figure 4 TEM images of the covalent organic frameworks obtained in Examples 1, 2 and 3 of this invention; as shown in the figures, TAPT-DHTA-COF, QL-COF and Fe-QL-COF exhibit good crystallinity.

[0045] Figure 5 HAADF-STEM image of Fe-QL-COF obtained in Example 3 of this invention; as can be seen from the image, the metal exhibits a single-atom dispersion in the structure.

[0046] Figure 6The XANES and EXAFS spectra of the Fe-QL-COF sample obtained in Example 3 of this invention are shown in the left figure. Comparing the XANES spectra of the example and the two standard references (Fe foil and FePc), the XANES curves of Fe-QL-COF show similar contours, indicating similar local coordination geometry. In the EXAFS spectrum of the right figure, the Fe-N / O peaks in Fe-QL-COF are close to those in Fe2O3 and FePc. Simultaneously, Fe-QL-COF lacks Fe-Fe, exhibiting its characteristic of single-atom dispersion.

[0047] Figure 7 The 2D-mapped fs-TA spectra of the covalent organic frameworks obtained in Examples 3 and 2 of this invention are shown in Figures 1, 2, and 3. Figure 1 shows the 2D-mapped fs-TA spectrum of the Fe-QL-COF film, and Figure 2 shows the 2D-mapped fs-TA spectrum of the QL-COF film. As can be seen from the figures, after excitation at 350 nm, the initially recorded fs-TA spectrum in the Fe-QL-COF film consists of a negative band in the range of 360 to 500 nm and a positive band that peaks at 550 nm. The former negative band is attributed to ground-state bleaching (GSB). This is consistent with the comparison of the steady-state absorption spectra, while the positive band is related to excited-state absorption (ESA). The fs-TA spectrum of QL-COF is similar to that of Fe-QL-COF.

[0048] Figure 8 The kinetic curves of the fs-TA spectra of the covalent organic frame samples obtained in Examples 3 and 2 of this invention are shown in the figure. As can be seen from the figure, by fitting the kinetic curve at 550 nm, the ESA lifetimes of Fe-QL-COF and QL-COF are estimated to be approximately 43,000 ps and 12,000 ps, ​​respectively. It should be noted that due to the limitations of instrument detection, the maximum lifetime value we measured experimentally was 8,000 ps.

[0049] Figure 9Performance of COF photocatalysts in olefin-carbonyl reduction cross-coupling reactions; (a) Conversion efficiency and individual yield of olefin-carbonyl reduction cross-coupling reactions using M-QL-COF (M = Fe, Co, Ni, Cu, Zn) as photocatalysts; (b) Conversion efficiency and individual yield of olefin-carbonyl reduction cross-coupling reactions using Fe-QL-COF or under controlled conditions; (c) olefin-carbonyl reduction cross-coupling reactions using Fe-QL-COF as a catalyst. Conversion efficiency and individual yield of different products synthesized by combined reaction; 1: methyl 4-(4-fluorophenyl)-4-hydroxybutyrate, 2: methyl 4-([1,1'-biphenyl]-4-yl)-4-hydroxybutyrate, 3: methyl 4-(3,4-dimethoxyphenyl)-4-hydroxybutyrate, 4: 1-(4-fluorophenyl)-3-(benzenesulfonyl)prop-1-ol, 5: 4-([1,1'-biphenyl]-4-yl)-4-hydroxybutyronitrile; (d) Fe-QL-COF Recovery experiments were conducted. (a) demonstrated the catalytic effects of quinoline COFs of different metals, with Fe-QL-COF showing the best catalytic effect, exhibiting the highest conversion and separation rates for the olefin-carbonyl reduction cross-coupling reaction using p-fluorobenzaldehyde and methyl acrylate as raw materials. (b) showed the differences in the catalytic effect of Fe-QL-COF under different controlled conditions for the olefin-carbonyl reduction cross-coupling reaction using p-fluorobenzaldehyde and methyl acrylate as raw materials; no reaction occurred without light, and the reaction was very poor without a catalyst. (c) indicated the synthesis of different products from the olefin-carbonyl reduction cross-coupling reaction using Fe-QL-COF. The raw materials were: Group 1: p-fluorobenzaldehyde and methyl acrylate; Group 2: [1,1'-biphenyl]-4-carboxaldehyde and methyl acrylate; Group 3: 3,4-dimethoxybenzaldehyde and methyl acrylate; Group 4: p-fluorobenzaldehyde and phenyl vinyl sulfone; Group 5: [1,1'-biphenyl]-4-carboxaldehyde and propylene. (d) showed the effects of Fe-QL-COF. The recovery test showed the conversion rate and separation rate of the five-cycle reaction; the conversion rate refers to the amount of raw material converted, and the separation rate refers to the amount of product obtained. Detailed Implementation

[0050] This invention provides a series of M-QL-COFs, wherein the raw materials for the M-QL-COFs include: amino monomers, aldehyde-containing organic monomers, pyruvic acid, and transition metal salts; wherein the amino monomer TAPT ( ), aldehyde-containing organic monomers (e.g., DHTA) Imine COF is obtained through Schiff base reaction; imine COF reacts with pyruvate to obtain quinoline COF; finally, it forms coordination with transition metals (such as Fe(III), Co(II), Ni(II), Cu(II), Zn(II) ions) to obtain a series of M-QL-COF.

[0051] Specifically, the preparation method of the metal quinoline covalent organic framework of the present invention includes the following steps:

[0052] 1) Disperse amino monomers and aldehyde-containing organic monomers in a solvent and sonicate for 5 to 120 seconds; then add a catalyst and perform at least three cycles of freezing-vacuuming-thawing to remove air from the reaction apparatus; then seal the apparatus with a flame gun at 600 to 1200°C; finally react in a sealed container at 100 to 160°C for at least 3 days, cool to room temperature, and wash to obtain an imine covalent organic framework;

[0053] 2) Disperse the imine covalent organic framework, pyruvate, and oxidant in a solvent and sonicate for 5 to 120 seconds; purge the air from the reaction apparatus by at least three cycles of freezing-vacuuming-thawing; then seal the tube with a flame gun at 600 to 1200°C; finally, react in a sealed container at 100 to 160°C for at least 3 days, cool to room temperature, and wash to obtain the quinoline covalent organic framework.

[0054] 3) Disperse the quinoline covalent organic framework and transition metal salt in a solvent, sonicate for 5 to 120 seconds, stir at room temperature for 12 to 48 hours, and wash to obtain the metal quinoline covalent organic framework.

[0055] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified, specific conditions in the examples are performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used without a specified manufacturer are all commercially available conventional products. In the embodiments of the present invention, 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, 2,5-dihydroxyterephthalaldehyde, pyruvic acid, DDQ, transition metal salts, 2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylic acid ester (HEH), o-dichlorobenzene, n-butanol, acetic acid, acetone, methanol, and tetrahydrofuran were purchased from Adamas-beta.

[0056] Example 1

[0057] A mixture of TAPT (28.35 mg, 0.08 mmol), DHTA (19.93 mg, 0.12 mmol), 6 M acetic acid (100 μL), o-dichlorobenzene (0.5 mL), and n-butanol (0.5 mL) was placed in a 10 mL Pyrex tube. The mixture was sonicated for 2 minutes, degassed by three freeze-thaw cycles, vacuum sealed, and heated at 120 °C for 3 days. The reaction mixture was cooled to room temperature. The product was collected by filtration, washed several times with acetone, methanol, and tetrahydrofuran, and then Soxhlet extracted with acetone, methanol, and tetrahydrofuran (24 hours for each solvent). After vacuum drying at 80 °C for 12 hours, the target product TAPT-DHTA-COF was obtained.

[0058] Example 2

[0059] A mixture of TAPT-DHTA-COF (30 mg), pyruvate (80 μL), DDQ (20 mg), o-dichlorobenzene (0.5 mL), and n-butanol (0.5 mL) was placed in a 10 mL Pyrex tube. The mixture was sonicated for 2 minutes, degassed by three freeze-thaw cycles, vacuum sealed, and heated at 120 °C for 3 days. The reaction mixture was cooled to room temperature. The product was collected by filtration, washed several times with acetone, methanol, and tetrahydrofuran, and then Soxhlet extracted with acetone, methanol, and tetrahydrofuran (24 hours for each solvent). After vacuum drying at 80 °C for 12 hours, the target product QL-COF was obtained.

[0060] Example 3

[0061] A mixture of QL-COF (90 mg, 1.35 mmol), MCl2 (M = Co, Ni, Cu, or Zn) or FeCl3 (4.05 mmol) and methanol (120 mL) was placed in a 250 mL round-bottom flask. The mixture was sonicated for 2 minutes and stirred at room temperature for 24 hours. The product was collected by filtration, washed several times with methanol and deionized water, and then dried under vacuum at 80 °C for 12 hours to obtain the target product M-QL-COF (M = Fe, Co, Ni, Cu, or Zn).

[0062] Structural characterization of Examples 1-3

[0063] 1) Infrared images of covalent organic framework samples obtained using amino monomers and aldehyde monomers.

[0064] The obtained sample was first dried in a vacuum oven at 60°C, and then infrared testing was performed on the sample.

[0065] 2) The crystallography of the covalent organic framework sample was measured using X-ray diffraction (PXRD).

[0066] Powder X-ray diffraction (PXRD) measurements were performed on a Rigaku SmartLab X-ray diffractometer using Cu-Kα radiation (λ = 1.54178 Å) in the 2θ range, from 2° to 30°, at a scan rate of 5° min. -1 .

[0067] 3) TEM images of covalent organic framework samples obtained by field emission transmission electron microscopy.

[0068] Field emission scanning electron microscopy (FE-TEM) images were acquired on a Talos F200S and obtained on a high-resolution transmission electron microscope (HR-TEM).

[0069] 4) The atomic distribution of the covalent organic framework sample was obtained using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM).

[0070] Images of dual Cs-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) were studied using a Spectra Ultra 60-300 with an accelerating voltage of 200 kV.

[0071] 5) XANES / EXAFS plots of covalent organic framework samples obtained by XAFS testing and software fitting.

[0072] XAFS measurements of the transition metal cobalt were performed at station BL17B of the Shanghai Synchrotron Radiation Facility (SSRF). The SSRF's electron storage ring operated at 3.5 GeV with a maximum current of 200 mA. Metal K-edge XAFS data were acquired using a fixed-exit Si(111) dual-crystal monochromator. Fluorescence signals were collected using a Wright detector, and the energy was calibrated using a metal foil.

[0073] The obtained EXAFS data were analyzed using the ATHENA module of the IFEFFIT software package according to standard procedures. The EXAFS contributions of different coordination layers were separated using the Hanning window. Subsequently, quantitative curve fitting was performed in R space and Fourier transform k space using the ARTEMIS module of IFEFFIT.

[0074] 6) Femtosecond transient absorption spectroscopy (fs-TA) measurement of covalent organic framework samples

[0075] Femtosecond transient absorption spectroscopy (fs-TA) measurements were performed using a self-made femtosecond pump-probe setup. A Ti:sapphire femtosecond laser system provided the laser pulses for the femtosecond transient absorption measurements. A regenerative amplifier (Spectra Physics, Spitfire) equipped with a mode-locked Ti:sapphire laser (Spectra Physics, Tsunami) output a laser pulse at a wavelength of 800 nm (150 fs, 1 kHz), which was then split into two parts using a 9:1 beam splitter. The primary part was fed into a TOPAS Prime (LightConversion) to generate a pump pulse (350 nm, 150 fs, 1 kHz). The secondary part was further attenuated and focused onto a 3 mm calcium fluoride plate to generate a probe pulse. An ultraviolet filter was inserted into the probe beam to select the ultraviolet-visible probe beam (360–680 nm). The time delay between the pump beam and the probe beam was adjusted using a computer-controlled motorized translation stage in the pump beam. The time resolution between the pump pulse and the probe pulse was determined to be ~150 fs (FWHM). Transmitted light was detected using a CMOS linear image sensor. The excitation pulse energy measured at the sampling point was approximately 0.4 μJ cm⁻¹. −2 Spectrophotometry was used to check the stability of the samples before and after each experiment. The kinetic trajectories obtained from time-resolved spectra were analyzed, and a nonlinear least-squares fitting method was used to deconvolve the instrument response function (IRF) to obtain a general exponential function. All spectroscopic measurements were performed at room temperature.

[0076] Application of the photocatalytic olefin carbonyl reduction cross-coupling experiment of the products obtained in Examples 2-3

[0077] A general procedure for photocatalytic olefin-carbonyl reduction cross-coupling:

[0078] A mixture of M-QL-COF (1 mg) and 2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylic acid ester (HEH) (101.3 mg, 0.4 mmol) was placed in a 15 mL Schlenk tube. The tube was completely degassed and purged three times with argon. 4-fluorobenzaldehyde (21.5 μL, 0.2 mmol), methyl acrylate (90.1 μL, 1 mmol), and anhydrous DMSO (1 mL) were injected into the Schlenk tube. The reaction mixture was irradiated with a blue LED (420–430 nm, 45 W) for 24 hours and cooled with an electric fan to maintain a constant reaction temperature of 25 °C. After the reaction was complete, all liquid phases were collected and quantitatively analyzed by gas chromatography (GC) with a flame ionization detector (FID), using n-dodecane as an internal standard. The product was confirmed by comparison of retention times with standards and further validated by gas chromatography-mass spectrometry (GC-MS). Gas chromatography analysis was performed using a Shimadzu GC-2030 chromatographic column equipped with an HP-5 column (30 m × 320 μm × 0.25 μm) and an FID detector, with N2 as the carrier gas. Gas chromatography-mass spectrometry analysis was performed using quadrupole mass spectrometry equipped with an HP-5 MS column (30 m × 0.25 mm × 0.25 μm), with He as the carrier gas.

Claims

1. A metalloquinoline covalent organic framework, characterized in that: The raw materials for the metal quinoline covalent organic framework include: an amino monomer, an aldehyde-containing organic monomer, pyruvate, and a transition metal salt; wherein the amino monomer is 2,4,6-tris(4-aminophenyl)-1,3,5-triazine.

2. The metalloquinoline covalent organic framework according to claim 1, characterized in that: The aldehyde-containing organic monomer is selected from at least one of 2,5-dihydroxyterephthalaldehyde, terephthalaldehyde, or 2,5-dimethoxyterephthalaldehyde; further, the molar ratio of the amino monomer to the aldehyde-containing organic monomer is 1:1 to 3; preferably 1:1.

5.

3. The metalloquinoline covalent organic framework according to claim 1 or 2, characterized in that: The transition metal salt is selected from at least one of the nitrate, sulfate, or chloride salts of a transition metal; further, the transition metal in the transition metal salt is selected from at least one of iron, cobalt, nickel, copper, or zinc; preferably, the transition metal salt is selected from at least one of ferric chloride, cobalt chloride, copper chloride, nickel chloride, or zinc chloride; more preferably, the molar ratio of the amino monomer to the transition metal salt is 1:1 to 5.

4. The metalloquinoline covalent organic framework according to any one of claims 1-3, characterized in that: The molar ratio of pyruvate to amino monomer is 1:1 to 10.

5. The method for preparing the metalloquinoline covalent organic framework according to any one of claims 1-4, characterized in that: Includes the following steps: An amino monomer and an aldehyde-containing organic monomer react under the action of a catalyst to obtain an imine covalent organic framework; the imine covalent organic framework reacts with pyruvate under the action of an oxidant to obtain a quinoline covalent organic framework; finally, it is coordinated with a transition metal salt to obtain the metal quinoline covalent organic framework.

6. The method for preparing the metalloquinoline covalent organic framework according to claim 5, characterized in that: The catalyst is selected from at least one of acetic acid or isoquinoline; preferably acetic acid; the oxidant is selected from at least one of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone, tetrachlorobenzoquinone, and tetrabutylammonium iodide; preferably 2,3-dichloro-5,6-dicyano-1,4-benzoquinone.

7. The method for preparing the metalloquinoline covalent organic framework according to claim 5 or 6, characterized in that: Includes the following steps: 1) Disperse amino monomers, aldehyde-containing organic monomers, and catalysts in a solvent, remove air, react under sealed conditions at 100-160℃, cool, and wash to obtain an imine covalent organic framework; 2) Disperse imine covalent organic framework, pyruvate, and oxidant in a solvent, remove air, react at 100-160℃ under sealed conditions, cool and wash to obtain quinoline covalent organic framework; 3) The quinoline covalent organic framework and transition metal salt are dispersed in a solvent, stirred at room temperature, and washed to obtain the metal quinoline covalent organic framework.

8. The method for preparing the metalloquinoline covalent organic framework according to claim 7, characterized in that: The reaction is carried out at 100-160℃ for more than 3 days; the stirring is carried out at room temperature for 12-48 hours.

9. The method for preparing the metalloquinoline covalent organic framework according to claim 7 or 8, characterized in that: The solvent is selected from at least one of n-butanol, o-dichlorobenzene, or methanol.

10. The use of the metal quinoline covalent organic framework according to any one of claims 1-4 or the metal quinoline covalent organic framework prepared by the preparation method according to any one of claims 5-9 as a catalyst in the field of photocatalysis; further, as a catalyst for photocatalytic olefin-carbonyl reduction cross-coupling reaction.

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