Planar organic ligand, metal organic framework material based on connector torsion angle regulation and control, and preparation method and application of metal organic framework material

Abstract

The invention discloses a planar organic ligand, a metal organic framework material based on connector torsion angle regulation and control and a preparation method and application thereof, after 2, 5-di (1H-pyrazole-4-yl) thieno [3, 2-b] thiophene and a nickel metal cluster form an MOF (Metal Organic Framework), the smaller torsion angle structure of the ligand can regulate and control the LMCT (Ligand Molecular Cluster Transfer) efficiency; therefore, the generation of O2 <-> by single electron transfer is decisively influenced; the photocatalytic reaction performance of MOF is promoted, and the coupling rate of benzylamine reaches 94% or above after photocatalytic benzylamine is subjected to oxidative coupling reaction. The ligand is obtained by removing a protecting group through palladium-catalyzed coupling reaction, the reaction condition is mild, and the coupling reaction yield is proper; the metal organic framework material can be prepared through solvothermal reaction, the reaction is mature, and large-scale preparation can be realized.

Description

Technical Field

[0001] This invention belongs to the field of metal-organic functional materials technology, specifically relating to a planar organic ligand, a metal-organic framework material based on the control of the linker torsion angle, its preparation method and application. Background Technology

[0002] Fine organic synthesis is crucial for economic and social development, but it places extremely high demands on reaction efficiency and selectivity. Utilizing photons as a traceless and green reagent, photoactivating molecular oxygen (O2) to generate reactive oxygen species (ROS) maximizes atom economy, providing an efficient and sustainable approach for this field. – Formed through the single-electron reduction of molecular oxygen, it is characterized by an unpaired electron occupying an antibonding π* orbital. This endows it with dual properties as both a free radical and anion. In many sophisticated organic synthesis reactions, such as the selective oxidation of sulfides to sulfoxides and the oxidative coupling of benzylamine, over-oxidation is a major factor leading to side reactions, while O2•, with its milder reactivity... – This could potentially achieve high selectivity; therefore, promoting O2• – The generation of this substance has broad prospects for the synthesis of fine chemicals.

[0003] However, O2• – The functional role of O2 is often overlooked, and related research remains relatively limited and faces a dual challenge. First, from a photophysics perspective, O2• – (Generated via electron transfer pathway) and 1 The generation of O2 (through energy transfer pathways) directly competes with its common precursor—photogenerated excitons. Furthermore, even in the electron transfer-driven photocatalytic O2 reduction reaction (ORR), O2• – It also always competes with other products (such as H2O2 generated by two-electron ORR), making it complex to maintain its concentration and lifetime. Despite significant efforts to regulate ROS generation in O2 photoactivation, current research still faces challenges related to low selectivity (especially for O2•). – This also highlights the challenges of lacking a comprehensive understanding of the mechanisms underlying catalyst exciton dynamics.

[0004] Metal-organic frameworks (MOFs) are crystalline porous materials formed through coordination-driven self-assembly of metal nodes and organic linkers, providing an ideal platform for regulating O2 photoactivation pathways. Photocatalytic processes in MOFs are typically initiated by ligand-to-metal charge transfer (LMCT). To date, several strategies have been developed to regulate ROS generation in MOFs, such as defect engineering (altering the electronic structure of metal clusters through doping), linker engineering (introducing specific photosensitive groups, such as porphyrins and pyrene), and metal node engineering (creating unsaturated sites to influence charge separation). Inspired by the natural photosynthesis of chlorophyll, chromophores such as porphyrins, pyrene, anthraquinones, and their derivatives play a crucial role in triggering photocatalytic redox reactions in MOFs, thanks to their excellent visible light absorption, redox properties, and photophysical characteristics. Therefore, regulating the structural properties of chromophore linkers in MOFs (e.g., the degree of intermolecular delocalization and torsion angle) holds promise for easily promoting the generation of target ROS. Unfortunately, attempts to precisely control the exciton dynamics of MOFs through the rational design of chromophore linkers are still rare, and the relationship between chromophore structure and their exciton behavior is not yet fully understood. Summary of the Invention

[0005] For the reasons stated above, the first objective of this invention is to provide a planar organic ligand, 2,5-bis(1H-pyrazol-4-yl)thieno[3,2-b]thiophene, in which the two planes containing the two pyrazoles and two thiophenes have an angle of approximately 1.63°. Therefore, the organic ligand is nearly planar. After constructing a MOF, it can modulate the LMCT efficiency, thereby decisively affecting the single-electron transfer to generate O2•. – ; Enhance the competition between energy transfer and the generation of ¹O2.

[0006] The second objective of this invention is to provide a method for preparing 2,5-bis(1H-pyrazol-4-yl)thiophene[3,2-b]thiophene, wherein the planar organic ligand 2,5-bis(1H-pyrazol-4-yl)thiophene[3,2-b]thiophene is synthesized by coupling reaction.

[0007] The third objective of this application is to provide a metal-organic framework (MOF) material based on the torsion angle regulation of the linker. Ni8O6 metal clusters form a MOF through coordination with the planar organic ligand 2,5-bis(1H-pyrazol-4-yl)thiophene[3,2-b]thiophene. The planar linker ligands between the metal clusters and the near-0° torsion angle allow the MOF material to regulate the LMCT efficiency, thereby decisively influencing the single-electron transfer to generate O2•. – This promotes the photocatalytic reaction.

[0008] The fourth objective of this application is to provide a method for preparing metal-organic framework materials based on the control of the torsion angle of the linker. The method involves the coordination of 2,5-bis(1H-pyrazol-4-yl)thiopheno[3,2-b]thiophene with a nickel precursor via a solvothermal reaction. The reaction is mature and can be prepared on a large scale.

[0009] The fifth objective of this invention is to provide a metal-organic framework material based on the torsion angle regulation of the linker as a catalyst in the photocatalytic oxidative coupling reaction of benzylamine, which can photocatalyze the oxidative coupling reaction of benzylamine with high reaction rate and selectivity.

[0010] The first objective of this invention can be achieved by adopting the following technical solution:

[0011] A planar organic ligand, chemically named 2,5-bis(1H-pyrazol-4-yl)thiopheno[3,2-b]thiophene; its chemical structural formula is shown in Formula I:

[0012]

[0013] The second objective of this invention can be achieved by adopting the following technical solution:

[0014] A method for preparing planar organic ligands includes the following steps:

[0015] After coupling 2,5-dibromothieno[3,2-b]thiophene with 1-(tetrahydro-2H-pyran-2-yl)-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborane-2-yl)-1H-pyrazole, the pyran protecting group is removed to obtain 2,5-bis(1H-pyrazol-4-yl)thieno[3,2-b]thiophene.

[0016] The third objective of this invention can be achieved by adopting the following technical solution:

[0017] A metal-organic framework material based on the control of the torsion angle of the linker includes a 2,5-bis(1H-pyrazol-4-yl)thiopheno[3,2-b]thiophene organic ligand and a Ni8O6 metal cluster; in one unit, a Ni8O6 metal cluster is coordinated with twelve deprotonated organic ligands to form a tetrahedral cage and an octahedral cage; exhibiting an fcu topology.

[0018] Furthermore, the metal-organic framework material based on the control of the torsion angle of the linker is a cubic crystal system with a space group of Fm-3m; the unit cell parameters are: a=b=c=29.22 Å, α=β=γ= 90°.

[0019] The fourth objective of this invention can be achieved by adopting the following technical solution:

[0020] The preparation method of metal-organic framework materials based on the control of the torsion angle of the connector includes the following steps:

[0021] The metal-organic framework material based on the linker torsion angle was prepared by solvothermal reaction of 2,5-bis(1H-pyrazol-4-yl)thiopheno[3,2-b]thiophene with a nickel precursor in a solvent.

[0022] Furthermore, the nickel precursor is one or more of nickel hydrochloride, acetate, nitrate, or their hydrates.

[0023] Furthermore, the molar ratio of 2,5-bis(1H-pyrazol-4-yl)thiopheno[3,2-b]thiophene to the nickel precursor is 1:(2-2.2).

[0024] Furthermore, the solvent is a mixture of N,N-dimethylacetamide and water, with a volume ratio of N,N-dimethylacetamide to water of (2-8):1.

[0025] Furthermore, the molar volume ratio of 2,5-bis(1H-pyrazol-4-yl)thiopheno[3,2-b]thiophene to the solvent is (10-50) μmol: 1 mL.

[0026] Furthermore, the reaction is carried out in the presence of nitric acid, with nitric acid added until the concentration of the reaction solution is 0.5-2 mol / L.

[0027] Furthermore, the reaction temperature is 100-140℃, and the reaction time is 12-96h.

[0028] Furthermore, the reaction includes purification and activation steps: solid-liquid separation is performed after the reaction, and the solid phase is washed with DMF, methanol and acetone.

[0029] Furthermore, after Soxhlet extraction and activation using acetone as a solvent, the material is dried to obtain the metal-organic framework material based on the control of the linker torsion angle.

[0030] The fifth objective of this invention can be achieved by adopting the following technical solutions:

[0031] Application of metal-organic framework materials based on linker torsion angle as catalysts in photocatalytic benzylamine oxidative coupling reaction.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] 1. The planar organic ligand of this invention is 2,5-bis(1H-pyrazol-4-yl)thieno[3,2-b]thiophene, in which the two planes containing the pyrazol and thiophene rings are nearly coplanar (with an included angle of approximately 1.63°). After constructing a MOF with a nickel metal cluster, the small torsion angle structure of this ligand can modulate the LMCT efficiency, thereby decisively affecting the single-electron transfer to generate O2• – ; to enhance the performance of MOF photocatalytic reactions.

[0034] 2. The present invention provides a method for preparing 2,5-bis(1H-pyrazol-4-yl)thieno[3,2-b]thiophene, wherein 2,5-dibromothiophene undergoes a palladium-catalyzed coupling reaction with pyrazole containing a protecting group and a 4,4,5,5-tetramethyl-1,3,2-dioxaborane reactive group, followed by removal of the protecting group to obtain the planar organic ligand 2,5-bis(1H-pyrazol-4-yl)thieno[3,2-b]thiophene. The palladium-catalyzed reaction conditions are mild, and the coupling reaction yield is suitable.

[0035] 3. This application relates to metal-organic framework (MOF) materials based on the torsion angle regulation of the linker. The Ni8O6 metal cluster forms a MOF through coordination with the planar organic ligand 2,5-bis(1H-pyrazol-4-yl)thiophene[3,2-b]thiophene. By establishing the geometry (torsion angle) of the linker, the electron transfer efficiency is improved, thereby optimizing the ROS route of the MOF material to generate O2• through single-electron transfer. – This significantly improves the catalytic performance of MOF materials as photocatalysts.

[0036] 4. The method for preparing metal-organic framework materials based on the control of the torsion angle of the linker in this application can be prepared by coordinating 2,5-bis(1H-pyrazol-4-yl)thiopheno[3,2-b]thiophene with a nickel precursor through a solvothermal reaction; the reaction is mature and can be prepared on a large scale.

[0037] 5. The application of the metal-organic framework material based on the torsion angle regulation of the linker as a catalyst in the photocatalytic oxidative coupling reaction of benzylamine in this invention can achieve high reaction rate and selectivity in the photocatalytic oxidative coupling reaction of benzylamine; the benzylamine coupling yield reaches more than 94%. Attached Figure Description

[0038] Figure 1 The 1H NMR spectrum of H2TTPz-α prepared in Example 1;

[0039] Figure 2 The carbon NMR spectrum of H2TTPz-α prepared in Example 1;

[0040] Figure 3 High-resolution mass spectra of H2TTPz-α prepared in Example 1;

[0041] Figure 4 The hydrogen NMR spectrum of H2TTPz-β prepared in Comparative Example 1;

[0042] Figure 5 The carbon NMR spectrum of H2TTPz-β prepared in Comparative Example 1;

[0043] Figure 6 High-resolution mass spectra of H2TTPz-β prepared for Comparative Example 1;

[0044] Figure 7 PXRD patterns of Ni-TTPz-α and Ni-TTPz-β;

[0045] Figure 8 Fourier transform infrared spectra of Ni-TTPz-α and Ni-TTPz-β and their ligands;

[0046] Figure 9 SEM and HR-TEM images of Ni-TTPz-α and Ni-TTPz-β;

[0047] Figure 10 Nitrogen adsorption-desorption isotherms and their pore size distributions measured at 77 K for Ni-TTPz-α and Ni-TTPz-β.

[0048] Figure 11 Figure 1 shows the yield results of the visible light-driven photocatalytic oxidative coupling reaction of benzylamine under different conditions.

[0049] Figure 12 For Ni-TTPz-α and Ni-TTPz-β 1 O2 and O2• – Radar chart comparing generation rate and performance;

[0050] Figure 13 The figure shows the quenching experimental results of the Ni-TTPz-α catalytic benzylamine oxidation reaction;

[0051] Figure 14 EPR spectra of the Ni-TTPz-α system containing DMPO under different blue LED irradiation times;

[0052] Figure 15 This is a schematic diagram of the assembly of Ni-TTPz-α and Ni-TTPz-β. Detailed Implementation

[0053] The technical solution of the present invention will now be clearly and completely described in conjunction with specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0054] Regulating ROS, especially O2• – The formation of ROS is particularly important for substrate conversion and product selectivity in photocatalysis. However, existing catalyst preparation methods often struggle to precisely control the formation pathway of a specific ROS. Furthermore, catalyst preparation methods involving doping or defects often introduce risks such as sacrificing porosity (ligand modification or metal node modification), deteriorating MOF stability and crystallinity (defect engineering), making MOF composition analysis and influencing factors more complex. Therefore, this application provides a MOF material that modulates electron transfer efficiency and ROS pathway selection through the geometry (torsion angle) of the linker itself, thereby improving photocatalyst performance.

[0055] A planar organic ligand, chemically named 2,5-bis(1H-pyrazol-4-yl)thiopheno[3,2-b]thiophene; its chemical structural formula is shown in Formula I:

[0056]

[0057] The organic ligand 2,5-bis(1H-pyrazol-4-yl)thieno[3,2-b]thiophene has a pyrazole ring attached to each of the 2 and 5 positions of the dithiophene structure. The connection at the 2 and 5 positions ensures that the pyrazole ring and the dithiophene ring are almost in the same plane (the two planes have an angle of approximately 1.63°). Therefore, the organic ligand 2,5-bis(1H-pyrazol-4-yl)thieno[3,2-b]thiophene is a nearly planar ligand. After constructing a MOF, it can modulate the LMCT efficiency and promote single-electron transfer to generate O2•. – .

[0058] This application also provides a method for preparing a planar organic ligand, comprising the following steps:

[0059] 2,5-Dibromothieno[3,2-b]thiophene undergoes coupling with 1-(tetrahydro-2H-pyran-2-yl)-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborane-2-yl)-1H-pyrazole, followed by deprotection of the pyran protecting group, to yield 2,5-bis(1H-pyrazol-4-yl)thieno[3,2-b]thiophene. The reaction pathway is as follows:

[0060]

[0061] In one embodiment, the molar ratio of 2,5-dibromothiopheno[3,2-b]thiophene to 1-(tetrahydro-2H-pyran-2-yl)-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborane-2-yl)-1H-pyrazole is 1:4-6.

[0062] The coupling reaction was carried out in a palladium-catalyzed system; the reaction system consisted of Cs2CO3 as the base, Pd(PPh3)4 as the catalyst, and a mixed solution of THF and water as the solvent, and the reaction was carried out under an inert gas atmosphere.

[0063] In one embodiment, the molar ratio of Pd(PPh3)4, Cs2CO3 and 2,5-dibromothiophene[3,2-b]thiophene is (0.04-0.08):(7-12):1.

[0064] As one implementation method, the volume ratio of THF to water is (2-6):1.

[0065] As one embodiment, the molar volume ratio of 2,5-dibromothiopheno[3,2-b]thiophene to the solvent is (0.08-0.15) mmol: 1 mL.

[0066] In one implementation method, the reaction temperature is 60-85°C and the reaction time is 12-72 hours.

[0067] As one implementation method, a post-processing procedure is performed after the coupling reaction is completed. Preferably, the reaction solution is poured into water, extracted with ethyl acetate, and dried over anhydrous Na2SO4. Further, purification is performed by column chromatography using 200-300 mesh silica gel, with petroleum ether:ethyl acetate = 2:1 as the eluent.

[0068] As one embodiment, the deprotection is carried out in an acidic ethanol solution; the acidity is provided by a hydrochloric acid solution.

[0069] The coupled product was added to an ethanol solution containing hydrochloric acid aqueous solution and heated to remove the protecting group.

[0070] In one implementation method, the heating reaction is carried out at the reflux temperature for 6-24 hours.

[0071] As one embodiment, after the deprotection reaction, post-treatment is performed to remove the solvent, the residue is added to water, and the pH is adjusted to 5-7 with saturated sodium carbonate solution; the product is collected by filtration, washed with water and rinsed with a small amount of ethanol to obtain the 2,5-bis(1H-pyrazol-4-yl)thiopheno[3,2-b]thiophene.

[0072] This application also provides a metal-organic framework material based on the control of the torsion angle of the linker, comprising a 2,5-bis(1H-pyrazol-4-yl)thiopheno[3,2-b]thiophene organic ligand and a Ni8O6 metal cluster; in one unit, a Ni8O6 metal cluster is coordinated with twelve deprotonated organic ligands to form a tetrahedral cage and an octahedral cage; exhibiting an fcu topology.

[0073] MOF is composed of Ni8O6 metal clusters coordinated with 2,5-bis(1H-pyrazol-4-yl)thiopheno[3,2-b]thiophene organic ligands. Each metal cluster is coordinated with twelve deprotonated ligands through a pyrazol group, forming a three-dimensional porous structure with tetrahedral and octahedral cavities.

[0074] 2,5-Di(1H-pyrazol-4-yl)thieno[3,2-b]thiophene serves as a linker, and the planar thiophene-pyrazole accelerates the charge transfer from the ligand to the metal, optimizing the ROS route of the MOF material to generate O2• through single-electron transfer. – This significantly improves the catalytic performance of MOF materials as photocatalysts.

[0075] As one implementation method, the metal-organic framework material based on the control of the torsion angle of the connector is a cubic crystal with a space group of Fm-3m; the cell parameters are: a=b=c=29.22 Å, α=β=γ= 90°.

[0076] This application also provides a method for preparing a metal-organic framework material based on the control of the torsion angle of the connector, comprising the following steps: The metal-organic framework material based on the linker torsion angle was prepared by solvothermal reaction of 2,5-bis(1H-pyrazol-4-yl)thiopheno[3,2-b]thiophene with a nickel precursor in a solvent.

[0077] Metal-organic framework materials based on the control of the torsion angle of the linker can be prepared by solvothermal reaction. The method is simple and mature, does not require harsh reaction conditions and complex processes, and is suitable for large-scale preparation.

[0078] In one embodiment, the nickel precursor is one or more of nickel hydrochloride, acetate, nitrate, or their hydrates. This application preferentially uses Ni(OAc)₂·4H₂O as the nickel precursor.

[0079] In one embodiment, the molar ratio of 2,5-bis(1H-pyrazol-4-yl)thiopheno[3,2-b]thiophene to the nickel precursor is 1:(2-2.2).

[0080] In one embodiment, the solvent is a mixture of N,N-dimethylacetamide and water, with a volume ratio of N,N-dimethylacetamide to water of (2-8):1.

[0081] As one embodiment, the molar volume ratio of 2,5-bis(1H-pyrazol-4-yl)thiopheno[3,2-b]thiophene to the solvent is (10-50) μmol: 1 mL.

[0082] As one implementation method, the reaction is carried out in the presence of nitric acid, with nitric acid added until the concentration of the reaction solution is 0.5-2 mol / L.

[0083] In one implementation method, the reaction temperature is 100-140°C and the reaction time is 12-96 hours.

[0084] As one implementation method, the reaction also includes purification and activation steps: solid-liquid separation is performed after the reaction, and the solid phase is washed with DMF, methanol and acetone.

[0085] As one embodiment, the metal-organic framework material based on the linkage torsion angle is obtained by Soxhlet extraction and activation with acetone as solvent and then drying.

[0086] This application also provides the application of metal-organic framework materials based on the control of linker torsion angle as catalysts in the photocatalytic oxidative coupling reaction of benzylamine.

[0087] The following is a further explanation using specific embodiments.

[0088] Example 1

[0089] The preparation process of 2,5-bis(1H-pyrazol-4-yl)thienro[3,2-b]thiophene (named H2TTPz-α) is as follows:

[0090]

[0091] (1) In a 200 mL double-necked round-bottom flask equipped with a magnetic stirrer, add 6.85 mmol of 2,5-dibromothiopheno[3,2-b]thiophene powder, 41.34 mmol of 1-(tetrahydro-2H-pyran-2-yl)-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborane-2-yl)-1H-pyrazole, 66.91 mmol of Cs2CO3 and 0.38 mmol of Pd(PPh3)4; then repeat the vacuuming and nitrogen purging operation three times; after degassing with nitrogen, a mixed solution of 48 mL of THF and 12 mL of H2O is injected into the flask through a tube under nitrogen flow; then the flask is connected to a condenser and stirred under nitrogen protection for 24 h; after the reaction is completed, the mixture is poured into 100 mL of water and extracted three times with 150 mL of ethyl acetate; the organic phases are combined and washed with 150 mL of water three times. The product was dried over anhydrous Na2SO4; the organic solvent was removed by rotary evaporation to obtain the crude product; it was purified by silica gel column chromatography with petroleum ether:ethyl acetate = 2:1 (v / v) to give 1.57 g of 2,5-bis(1-(tetrahydro-2H-pyran-2-yl)-1H-pyrazol-4-yl)thieno[3,2-b]thiophene (named TTPz-α-THP); yield 52% (based on 2,5-dibromothieno[3,2-b]thiophene).

[0092] The proton and carbon NMR spectra are shown below;

[0093]

[0094]

[0095] (2) In a 50 mL flask, 0.91 mmol of TTPz-α-THP and 12 mL of ethanol were added, followed by 5 mL of 2.0 M HCl aqueous solution; the flask was connected to a condenser and the reaction was refluxed for 12 h; after the reaction mixture was cooled to room temperature, the solvent was removed by rotary evaporation; then, under vigorous stirring, the mixture was slowly poured into 20 mL of water; the pH was adjusted to 5-7 with saturated sodium carbonate solution; the product was collected by vacuum filtration, washed with water and rinsed with a small amount of ethanol to obtain 0.22 g of 2,5-bis(1H-pyrazol-4-yl)thieno[3,2-b]thiophene (named H2TTPz-α), with a yield of 88%;

[0096] 1H NMR spectrum as follows Figure 1 As shown; C NMR spectrum as shown Figure 2 As shown; High-resolution mass spectrometry is as follows Figure 3 As shown;

[0097] 1H NMR (400MHz, DMSO-d6)δ=7.96 (s,4H), 7.48(s,2H);

[0098] 13 C NMR (100MHz, DMSO-d6)δ=137.10,136.56,116.34,115.19 ppm;

[0099] RMS (m / z) calculated value C 12 H9N4S2 [M + H] + : 273.03, Measured value: 272.87.

[0100] Example 2

[0101] To a thick-walled, round-bottomed glass tube (high borosilicate glass, outer diameter 10 mm, inner diameter 8 mm), 36 µmol of Ni(OAc)₂·4H₂O, 18 µmol of H₂TTPz-α prepared in Example 1, 40 µL of nitric acid (952 µmol), 750 µL of N,N-dimethylacetamide, and 150 µL of H₂O were added sequentially. The mixture was sonicated for 5 min to form a uniformly dispersed suspension. The glass tube was then sealed and heated in an oven at 120 °C for 48 h, followed by natural cooling to room temperature. The resulting reddish-brown crystalline powder was collected and washed three times each with 1.0 mL of DMF, 1.0 mL of methanol, and 1.0 mL of acetone, and then vacuum dried at room temperature to obtain a crude product. The crude product was extracted with acetone using a Soxhlet extractor for 24 h, and the resulting crystalline powder was vacuum dried at 90 °C for 2 h to obtain 4.5 mg of activated metal-organic framework material based on linker torsion angle regulation, named Ni-TTPz-α.

[0102] Example 3

[0103] To a thick-walled, round-bottomed glass tube (high borosilicate glass, outer diameter 10 mm, inner diameter 8 mm), 37.8 µmol of Ni(OAc)₂·4H₂O, 18 µmol of H₂TTPz-α prepared in Example 1, 38 µL of nitric acid (900 µmol), 240 µL of N,N-dimethylacetamide, and 120 µL of H₂O were added sequentially. The mixture was sonicated for 5 min to form a uniformly dispersed suspension. The glass tube was then sealed and heated in an oven at 100 °C for 96 h, followed by natural cooling to room temperature. The resulting reddish-brown crystalline powder was collected and washed three times each with 1.0 mL of DMF, 1.0 mL of methanol, and 1.0 mL of acetone, and then vacuum dried at room temperature to obtain a crude product. The crude product was extracted with acetone using a Soxhlet extractor for 24 h, and the resulting crystalline powder was vacuum dried at 90 °C for 2 h to obtain 4.5 mg of activated metal-organic framework material based on linker torsion angle regulation, named Ni-TTPz-α.

[0104] Example 4

[0105] To a thick-walled, round-bottomed glass tube (high borosilicate glass, outer diameter 10 mm, inner diameter 8 mm), 39.6 µmol of Ni(OAc)₂·4H₂O, 18 µmol of H₂TTPz-α prepared in Example 1, 30 µL of nitric acid (720 µmol), 1.6 mL of N,N-dimethylacetamide, and 0.2 mL of H₂O were added sequentially. The mixture was sonicated for 5 min to form a uniformly dispersed suspension. The glass tube was then sealed and heated in an oven at 140 °C for 12 h, followed by natural cooling to room temperature. The resulting reddish-brown crystalline powder was collected and washed three times each with 1.0 mL of DMF, 1.0 mL of methanol, and 1.0 mL of acetone, and then vacuum dried at room temperature to obtain a crude product. The crude product was extracted with acetone using a Soxhlet extractor for 24 h, and the resulting crystalline powder was vacuum dried at 90 °C for 2 h to obtain 4.5 mg of activated metal-organic framework material based on linker torsion angle regulation, named Ni-TTPz-α.

[0106] Comparative Example 1

[0107] The preparation process of 3,6-bis(1H-pyrazol-4-yl)thienro[3,2-b]thiophene (named H2TTPz-β) is as follows:

[0108]

[0109] (1) In a 200 mL double-necked round-bottom flask equipped with a magnetic stirrer, add 10.10 mmol of 3,6-dibromothiopheno[3,2-b]thiophene powder, 45.8 mmol of 1-(tetrahydro-2H-pyran-2-yl)-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborane-2-yl)-1H-pyrazole, 99.26 mmol of Cs2CO3 and 0.55 mmol of Pd(PPh3)4; then repeat the vacuuming and nitrogen purging operation three times; after degassing a mixed solution of 72 mL of THF and 18 mL of H2O with nitrogen, inject it into the flask through a tube under a nitrogen flow; then connect the flask to a condenser and reflux and stir for 24 h under nitrogen protection; after the reaction is completed, pour the mixture into 150 mL of water and extract it three times with 200 mL of ethyl acetate; combine the organic phases and wash with 200 mL of water 3 times. The product was dried over anhydrous Na2SO4; the organic solvent was removed by rotary evaporation to obtain the crude product; it was purified by silica gel column chromatography with petroleum ether:ethyl acetate = 5:1 (v / v) to give 3.69 g of 3,6-bis(1-(tetrahydro-2H-pyran-2-yl)-1H-pyrazol-4-yl)thieno[3,2-b]thiophene (named TTPz-β-THP); yield 83% (based on 3,6-dibromothieno[3,2-b]thiophene).

[0110] The proton and carbon NMR spectra are shown below.

[0111] .

[0112]

[0113] (2) In a 50 mL flask, 1.07 mmol of TTPz-β-THP and 8 mL of ethanol were added, followed by 4.5 mL of 2.0 M HCl aqueous solution; the flask was connected to a condenser and the reaction was refluxed for 12 h; after the reaction mixture was cooled to room temperature, the solvent was removed by rotary evaporation; then, under vigorous stirring, the mixture was slowly poured into 20 mL of water; the pH was adjusted to 5-7 with saturated sodium carbonate solution; the product was collected by vacuum filtration, washed with water and rinsed with a small amount of ethanol to obtain 0.25 g of 3,6-bis(1H-pyrazol-4-yl)thiopheno[3,2-b]thiophene (named H2TTPz-β), with a yield of 86%;

[0114] 1H NMR spectrum as follows Figure 4 As shown; C NMR spectrum as shown Figure 5 As shown; High-resolution mass spectrometry is as follows Figure 6 As shown;

[0115] 1H NMR (400MHz, DMSO-d6)δ=8.07(s,2H),7.84(s,1H);

[0116] 13 C NMR (100MHz, DMSO-d6)δ=137.04,126.21,120.38,115.07 ppm;

[0117] RMS (m / z) calculated value C 12 H9N4S2 [M + H] + : 273.03, Measured value: 273.17.

[0118] Comparative Example 2

[0119] To a thick-walled, round-bottomed glass tube (high borosilicate glass, outer diameter 10 mm, inner diameter 8 mm), 36 µmol of Ni(OAc)₂·4H₂O, 18 µmol of H₂TTPz-β prepared in Comparative Example 1, 40 µL of nitric acid (952 µmol), 750 µL of N,N-dimethylacetamide, and 150 µL of H₂O were added sequentially. The mixture was sonicated for 5 min to form a uniformly dispersed suspension. The glass tube was then sealed and heated in an oven at 120 °C for 48 h, followed by natural cooling to room temperature. The resulting reddish-brown crystalline powder was collected and washed three times each with 1.0 mL of DMF, 1.0 mL of methanol, and 1.0 mL of acetone, and then vacuum dried at room temperature to obtain a crude product. The crude product was extracted with acetone using a Soxhlet extractor for 24 h, and the resulting crystalline powder was vacuum dried at 90 °C for 2 h to obtain 4.8 mg of activated metal-organic framework material based on linker torsion angle regulation, named Ni-TTPz-β.

[0120] Characterization and performance testing

[0121] 1. Powder X-ray Diffraction (PXRD) Test

[0122] Powder X-ray diffraction tests were performed on the Ni-TTPz-α prepared in Example 2 and the Ni-TTPz-β prepared in Comparative Example 2. The results are as follows: Figure 7 As shown, a is the X-ray diffraction pattern of Ni-TTPz-α; b is the X-ray diffraction pattern of Ni-TTPz-β.

[0123] PXRD confirmed the high crystallinity of these two MOFs. The structures of these MOFs were determined by modifying previously reported structural models in Materials Studio, and the optimized structures were refined using Pawley refinement before comparison with experimental data. The refinement results confirmed that both Ni-TTPz-α and Ni-TTPz-β are cubic crystals with space group Fm-3m and exhibit an fcu topology. Their cell parameters are: Ni-TTPz-α, a=b=c=29.22 Å, α=β=γ=90° (Rp=3.56%, Rwp=1.95%); Ni-TTPz-β, a=b=c=26.67 Å, ​​α=β=γ=90° (Rp=2.54%, Rwp=1.75%).

[0124] In both structures, the framework is composed of Ni8O6 metal clusters, each cluster being coordinated with twelve deprotonated ligands via pyrazole groups, forming a three-dimensional porous structure with tetrahedral and octahedral cavities; such as Figure 15 As shown, the planes containing the atoms in H2TTPz-α have an angle of 1.63°, making them almost coplanar; while the planes containing the atoms in H2TTPz-β have an angle of 33.80°, making them non-planar structures.

[0125] 2. Fourier Transform Infrared Spectroscopy (FTIR) Test

[0126] Fourier transform infrared spectroscopy was performed on the H2TTPz-α prepared in Example 1, the Ni-TTPz-α prepared in Example 2, the H2TTPz-β prepared in Comparative Example 1, and the Ni-TTPz-β prepared in Comparative Example 2. The results are as follows: Figure 8 As shown, a is the infrared spectrum of H2TTPz-α and Ni-TTPz-α; b is the infrared spectrum of H2TTPz-β and Ni-TTPz-β.

[0127]

[0128]

[0129]

[0130]

[0131] like Figure 8 As shown, the FTIR spectra of both Ni-TTPz-α and Ni-TTPz-β are at 3138 cm⁻¹. –1 and 861cm –1The disappearance of the peak at this point is attributed to the stretching and bending vibrations of the NH group in the free ligand, respectively. This observation confirms the deprotonation of the pyrazole nitrogen atom and its subsequent coordination with the nickel center. Furthermore, in the 1034–1045 cm⁻¹ range… –1 The appearance of a new peak attributable to the Ni-N stretching vibration within the range provides additional evidence for successful metal-ligand coordination.

[0132] 3. Scanning electron microscope (SEM) and high-resolution transmission electron microscope (HR-TEM)

[0133] The Ni-TTPz-α prepared in Example 2 and the Ni-TTPz-β prepared in Comparative Example 2 were observed by scanning electron microscopy and high-resolution transmission electron microscopy, respectively. Figure 9 As shown, a is the SEM image of Ni-TTPz-α; b is the SEM image of Ni-TTPz-β; c is the HR-TEM image of Ni-TTPz-α; and d is the HR-TEM image of Ni-TTPz-β.

[0134] Both Ni-TTPz-α and Ni-TTPz-β exhibit similar octahedral morphologies, indicating that the influence of the interconnect heterogeneous engineering on the structure is negligible. Clear Fast Fourier Transform (FFT) patterns with diffraction points can be observed in HR-TEM images, confirming the high crystallinity of Ni-TTPz-α and Ni-TTPz-β. Furthermore, the inset image shows clear lattice fringes consistent with the (002) crystal plane.

[0135] 4. Nitrogen adsorption measurement

[0136] Nitrogen adsorption measurements were performed on the Ni-TTPz-α prepared in Example 2 and the Ni-TTPz-β prepared in Comparative Example 2. The nitrogen adsorption-desorption isotherms and their pore size distribution diagrams are shown below. Figure 10 As shown; where a is the nitrogen adsorption-desorption isotherm of Ni-TTPz-α; b is the pore size distribution of Ni-TTPz-α; c is the nitrogen adsorption-desorption isotherm of Ni-TTPz-β; and d is the pore size distribution of Ni-TTPz-β.

[0137] Nitrogen adsorption-desorption measurements at 77 K showed typical type I isotherms, indicating a microporous structure. Ni-TTPz-α exhibited a BET specific surface area of ​​714.5 m² / g, with pore sizes concentrated between 0.6 nm and 1.2 nm. In contrast, Ni-TTPz-β had a BET surface area of ​​657.2 m² / g and pore sizes of 0.6 nm and 0.9 nm. The high specific surface area and well-defined pore size distribution further indicate that both frameworks possess good crystallinity and structural integrity.

[0138] 5. Photocatalytic oxidative coupling reaction of benzylamine

[0139] (1) The oxidative coupling of benzylamine was selected as a model reaction to evaluate the O2 photoactivation activity of this framework material. Reaction conditions: benzylamine (0.50 mmol), catalyst (3.0 mg), acetonitrile (4.0 mL), room temperature, 12 h, blue LED irradiation. The yield was determined by ¹H NMR with 1,1,2,2-tetrachloroethane as an internal standard; and the oxidative coupling reaction of benzylamine was carried out under different conditions, with the results as follows: Figure 11 As shown in the figure; a represents the yield of benzylamine oxidative coupling under different conditions; b represents the yield of photocatalytic products using Ni-TTPz-α and Ni-TTPz-β as catalysts under optimal reaction conditions.

[0140] The two ligands, H₂TTPz-α and H₂TTPz-β, exhibited negligible performance in visible-light-driven oxidative coupling of benzylamine, likely due to the lack of metal clusters for efficient LMCT formation. When Ni-TTPz-β was used as a catalyst, the reaction rate was slightly improved, reaching a yield of 48% after 12 h. Notably, Ni-TTPz-α showed the best performance in visible-light-driven oxidative coupling of benzylamine, achieving a yield as high as 99% under optimal conditions. Subsequently, the solvent effect was evaluated using ethanol, DMF, water, and acetonitrile. Acetonitrile proved to be the optimal solvent, yielding the highest yield in benzylamine oxidative coupling. Furthermore, experiments confirmed that the reaction is strictly dependent on photocatalytic O₂ activation: almost no product formation was observed under light-free, catalyst-free, or oxygen-free conditions (using a N₂ atmosphere), or when heated in the dark.

[0141] (2) In order to evaluate the tolerance of the photocatalyst to functional groups, a series of substituted benzylamines with electron-donating and electron-withdrawing groups were tested; the reaction results of different substrates are shown in Table 1. The reaction conditions were: benzylamine derivative (0.50 mmol), catalyst (3.0 mg), acetonitrile (4.0 mL), room temperature, 12 h, blue LED irradiation; orange background indicates Ni-TTPz-α catalysis results, and blue background indicates Ni-TTPz-β catalysis results; a and b indicate the reactions carried out in air and oxygen atmospheres, respectively.

[0142] Table 1. Reaction yields of different substrates

[0143]

[0144] Using Ni-TTPz-α as a catalyst, yields of all substrates exceeded 80%. This catalyst is particularly effective for substrates with electron-donating groups, and the substitution mode has little effect on the results. All substrates, including those with strong electron-withdrawing substituents (such as -F, -CF3), readily yielded yields exceeding 90% in air. A few exceptions, such as methoxy-substituted derivatives, required an oxygen atmosphere to achieve yields above 97%. Other substrates with -Br, -Cl, or -ester groups also benefited from an O2 atmosphere. In summary, Ni-TTPz-α exhibits excellent functional group tolerance and high catalytic activity across a broad substrate range. The superior performance of Ni-TTPz-α highlights the crucial role of the linker torsion angle.

[0145] (3) Quantitative kinetic analysis of reactive oxygen species (ROS) generation under visible light was performed to elucidate their structure-property relationship. 9,10-Anthracenediyl-bis(methylene)dimalonic acid (ABDA) was used as a trapping agent to monitor singlet oxygen (…). 1 The absorption peak of ABDA in the Ni-TTPz-α system decayed more rapidly, almost completely disappearing within 5 minutes, while the Ni-TTPz-β system required approximately 9 minutes. Kinetic analysis yielded apparent rate constants (kobs) of 0.43 min for both Ni-TTPz-α and Ni-TTPz-β. –1 and 0.20min –1 Corresponding 1 The O2 generation rate was 17.68 µM min. –1 and 12.4µM min –1 The two are similar 1 The O2 generation rate indicates that, 1 O2 is not the main factor leading to the enhanced activity of Ni-TTPz-α.

[0146] The reduction experiment of nitroblue tetrazolium (NBT) was used to study superoxide radicals (O2• – The formation of Ni-TTPz-α rapidly quenches the characteristic peak of NBT at 255 nm within 2 minutes, while Ni-TTPz-β shows no significant activity. For example... Figure 12 The quantitative analysis shown revealed significant differences in O2• between Ni-TTPz-α and Ni-TTPz-β. – The generation rates were 29.75 µM min⁻¹ and 2 µM min⁻¹, respectively, meaning the activity of Ni-TTPz-α was approximately 15 times that of the latter. Therefore, the enhanced activity of TTPz-α is mainly attributed to its stronger O₂• – Generation capability.

[0147] To further elucidate the role of ROS in the photocatalytic process, a series of quenching experiments were conducted in the Ni-TTPz-α system. Figure 13 Specifically, 1,4-benzoquinone (BQ), 1,4-diazabicyclo[2.2.2]octane (DABCO), KI, and AgNO3 were used as O2• – , 1 O2, photogenerated holes (h) + ) and photogenerated electrons (e – Quenching agent.

[0148] Experiments show that the reaction is completely inhibited when BQ or AgNO3 is added, indicating that the photogenerated e⁻ and O₂• – All of these are essential reactive species for the reaction; the reaction was partially inhibited upon the addition of KI, suggesting that photogenerated holes may interact with benzylamine-derived radical intermediates (PhCH2NH2• + The reaction was consumed; however, the addition of DABCO reduced the yield to 11%, indicating that... 1 Although O2 participates in the reaction process, it is not the main oxidant. 1 The reaction can continue even after O2 is quenched, while O2• – The reaction was significantly inhibited after being cleared, further confirming the role of O2• – It plays a leading role in the reaction.

[0149] Time-dependent electron paramagnetic resonance (EPR) spectroscopy further confirmed the generation of reactive oxygen species (ROS). 2,2,6,6-Tetramethylpiperidine (TEMP) and 5,5-dimethyl-1-pyrrolidine-N-oxide (DMPO) were used as singlet oxygen atoms, respectively. 1 O2) and superoxide radicals (O2• – The Ni-TTPz-α system acts as a spin trapping agent. No signal was detected in the Ni-TTPz-α system under dark conditions, indicating that visible light is a necessary condition for ROS generation. As the reaction proceeds, 1 O2 and O2• – The signal strength continued to increase ( Figure 14 This confirms the continuous generation of these two ROS.

[0150] In summary, this application constructs a metal-organic framework (MOF) with a nickel metal cluster and a planar organic ligand, 2,5-bis(1H-pyrazol-4-yl)thiophene[3,2-b]thiophene, which has a near-zero molecular torsion angle. Compared to the MOF constructed with the non-planar organic ligand 3,6-bis(1H-pyrazol-4-yl)thiophene[3,2-b]thiophene, the planar organic ligand improves electron transfer efficiency and selectively generates superoxide radicals (O2•) in photocatalytic reactions. –The ROS pathway promotes the use of organic framework materials as photocatalysts in the selective catalytic oxidative coupling reactions of organic amines and other reactions requiring O2• – Applications in highly selective oxidation reactions. This application also provides a method for controlling the torsion angle of MOF linkers to optimize the photocatalytic ROS generation pathway (especially preferentially generating O2•). – General strategies and methods for precise control.

[0151] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A planar organic ligand, characterized in that, The chemical name is 2,5-bis(1H-pyrazol-4-yl)thiopheno[3,2-b]thiophene; the chemical structural formula is shown in Formula I:

2. The method for preparing the planar organic ligand according to claim 1, characterized in that, Includes the following steps: After coupling 2,5-dibromothieno[3,2-b]thiophene with 1-(tetrahydro-2H-pyran-2-yl)-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborane-2-yl)-1H-pyrazole, the pyran protecting group is removed to obtain 2,5-bis(1H-pyrazol-4-yl)thieno[3,2-b]thiophene.

3. A metal-organic framework material based on the control of the torsion angle of the connector, characterized in that, It includes 2,5-bis(1H-pyrazol-4-yl)thiopheno[3,2-b]thiophene organic ligands and Ni8O6 metal clusters; in one unit, a Ni8O6 metal cluster is coordinated with twelve deprotonated organic ligands to form tetrahedral cages and octahedral cages; exhibiting an fcu topology.

4. The metal-organic framework material based on connector torsion angle control according to claim 3, characterized in that, The metal-organic framework material based on the control of the torsion angle of the linker is a cubic crystal with a space group of Fm-3m; the unit cell parameters are: a=b=c=29.22 Å, α=β=γ= 90°.

5. The method for preparing the metal-organic framework material based on the control of the torsion angle of the connector as described in claim 3 or 4, characterized in that, Includes the following steps: The metal-organic framework material based on the linker torsion angle was prepared by solvothermal reaction of 2,5-bis(1H-pyrazol-4-yl)thiopheno[3,2-b]thiophene with a nickel precursor in a solvent.

6. The method for preparing metal-organic framework materials based on the control of connector torsion angle according to claim 5, characterized in that, The nickel precursor is one or more of nickel hydrochloride, acetate, nitrate or their hydrate; The molar ratio of 2,5-bis(1H-pyrazol-4-yl)thieno[3,2-b]thiophene to the nickel precursor is 1:(2-2.2).

7. The method for preparing a metal-organic framework material based on the control of the torsion angle of the connector according to claim 5, characterized in that, The solvent is a mixture of N,N-dimethylacetamide and water, with a volume ratio of N,N-dimethylacetamide to water of (2-8):1; The molar volume ratio of 2,5-bis(1H-pyrazol-4-yl)thiopheno[3,2-b]thiophene to solvent is (10-50) μmol: 1 mL.

8. The method for preparing a metal-organic framework material based on the control of the torsion angle of the connector according to claim 5, characterized in that, The reaction is carried out in the presence of nitric acid, with nitric acid added until the concentration of the reaction solution is 0.5-2 mol / L; The reaction temperature is 100-140℃, and the reaction time is 12-96h.

9. The method for preparing a metal-organic framework material based on the control of the torsion angle of the connector according to claim 5, characterized in that, The reaction also includes purification and activation steps: solid-liquid separation is performed after the reaction, and the solid phase is washed with DMF, methanol and acetone; After activation by Soxhlet extraction using acetone as solvent, the material was dried to obtain the metal-organic framework material based on the control of the linker torsion angle.

10. The application of the metal-organic framework material based on the linkage torsion angle as described in any one of claims 5-9 as a catalyst in the photocatalytic oxidative coupling reaction of benzylamine.

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