A spin-catalytic material for promoting CO2 photoreduction and a preparation method thereof

Abstract

The application belongs to the field of carbon dioxide photocatalytic materials, and relates to a spin catalytic material for promoting CO2 photocatalysis and a preparation method thereof. The material is a high-activity metal grid supramolecule obtained by a volatilization method from a ligand 2,2'-pyrazine dihydrazine methanesulfamide (pbd) and a metal salt. As a photocatalyst, the material can adjust multiple spin states on a single Fe site in the metal grid supramolecule to effectively promote a visible light driven CO2 reduction reaction (CO2RR). After 1h of irradiation, the CO2 to CO yield can reach 6.26mmol g ‑1 , which shows an effective strategy of designing spin-based photocatalysts through supramolecular assembly to promote artificial photosynthesis.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of carbon dioxide photocatalytic materials, and relates to a spin catalytic material for promoting CO2 photocatalysis and a preparation method thereof. BACKGROUND

[0002] As a common strategy in supramolecular chemistry, self-assembly provides an important "bottom-up" principle for obtaining artificial functional molecules from simple building blocks. Among many synthetic strategies in the field of supramolecular chemistry, the method of coordination bond enables people to construct various multi-metal supramolecules, such as macrocycle, metal positioning and metal grid, using highly directional metal-ligand interactions. In fact, the modular nature of building blocks in the self-assembly process makes the synthesis of functional molecules easier, and a huge library of nanoscale molecular structures has been established.

[0003] Although the implementation of supramolecular strategy has made breakthroughs in several disciplines, due to the difficulty in adjusting the electronic structure of the metal center, the prediction of the valuable properties required for the assembly system is insufficient or impossible. For example, in the field of artificial photosynthesis, it has been proved to be an effective method to efficiently screen high-performance catalysts by modifying the electronic state using the local coordination environment around the catalytically active center. However, the influence of spin state on the predictable activity and / or selectivity in supramolecular assembly has long been ignored, mainly because it is a severe challenge to precisely control the local spin state of the catalytically active center.

[0004] Intentionally combining many metal sites together as accessible active components in multi-metal complexes, through high-density active sites and synergies between them, attractive catalytic properties are endowed. Some noble metal complexes, such as Ru(II), Pt(II), Ir(III), etc., have been widely used to construct photoactive metal-organic assemblies through some linear ligands. However, their lack of adjustable electronic structure often makes them unable to serve as suitable models to study the relationship between electronic structure and photocatalysis. SUMMARY

[0005] The application provides a spin catalytic material for promoting CO2 photocatalysis and a preparation method thereof, which is a supramolecular metal grid in which the spin state of the iron center can be chemically modified by counter anions to promote the photocatalytic CO2 reduction reaction (CO2RR). The pyrazine group located in the bridge ligand is expected to serve as a two-armed pocket to assemble a four-metal square supramolecule. The supramolecular metal lattice uses iron atoms as redox and spin crossover active centers.

[0006] The above technical purposes of the application are achieved by the following technical solutions:

[0007] The application provides a spin catalytic material for promoting CO2 photo-reduction, and a molecular formula of a single crystal structure of the material is [Fe4(pbd)4]ClO4·CH3OH or Fe4(pbd)4·2CH3CN; wherein, pbd is 2,2'-pyrazine dihydrazine thioamide.

[0008]

[0009] The material is tetragonal, and a space group is P4 / ncc; cell sizes of the material are similar, a and b are about c is about α=90°, β=90°, γ=90°, and Z=4.

[0010] Specifically, cell parameters of the spin catalytic material with the molecular formula [Fe4(pbd)4]ClO4·CH3OH are α=90°, β=90°, γ=90°, and Z=4,

[0011] Cell parameters of the spin catalytic material with the molecular formula Fe4(pbd)4·2CH3CN are α=90°, β=90°, γ=90°, and Z=4,

[0012] The application provides a preparation method of the spin catalytic material for promoting CO2 photo-reduction.

[0013] S1, preparing an organic ligand pbd: 2-acetylpyrazine is added into a double-mouthed round-bottom flask, and placed in an ice bath; anhydrous acetaldehyde and H2SO4 are added, and tert-butyl hydroperoxide is added dropwise; an FeSO4 solution is slowly added into the reaction bottle through a constant-pressure dropping funnel; after the dropwise addition is completed, the ice bath is removed, and stirring is performed at room temperature; after the reaction is completed, extraction is performed, and orange powder 2,5-diacetylpyrazine is obtained through reduced-pressure distillation; 2,5-diacetylpyrazine and aminothiourea are added into anhydrous ethanol, and glacial acetic acid is added as a catalyst; after the reaction is completed through heating and refluxing, suction filtration and drying are performed, and yellow powder 2,2'-pyrazine dihydrazine thioamide is obtained; a reaction formula of synthesizing 2,2'-pyrazine dihydrazine thioamide from 2,5-diacetylpyrazine and aminothiourea is as follows:

[0014]

[0015] S2, Preparation of complex [Fe4(pbd)4]ClO4.CH3OH: The ligand pbd was added to a single-neck flask containing methanol and heated to 70°C to obtain a yellow suspension. Fe(CIO4)2.xH2O was added to the ligand suspension, the solution quickly turned black, and after a period of reflux stirring, it was cooled to room temperature. The black solution was filtered and left to slowly evaporate in a beaker, and after a week, black square crystals were obtained.

[0016] S3, Preparation of complex Fe4(pbd)4.2CH3CN: The ligand pbd was added to a round-bottom flask containing methanol and heated to 70°C to obtain a yellow suspension. Fe(CF3SO3)2 was dissolved in acetonitrile and added to the ligand suspension, the solution quickly turned black, and after a period of reflux stirring, it was cooled to room temperature. The black solution was filtered and left to slowly evaporate in a beaker, and after a week, black square crystals were obtained.

[0017] Further, in the step S1, the molar ratio of 2,5-diacetylpyrazine and aminothiourea is (9.9-10.1):(9.9-10.1), and the volume ratio of ethanol and glacial acetic acid is (29.9 mL-30.1 mL):(0.3 mL-0.4 mL).

[0018] Further, in the step S1, the time of stirring reaction at room temperature is 5-6 h.

[0019] Further, in the step S1, the time of reflux stirring reaction is 6-7 h, and the temperature is 70-80°C.

[0020] Further, in the step S2, the molar ratio of pbd and Fe(CIO4)2.xH2O is (0.2-0.4):(0.2-0.4), and the ratio of methanol and pbd is (95 mL-105 mL):(0.2 mol-0.4) mol.

[0021] Further, in the step S3, the molar ratio of pbd and Fe(CF3SO3)2 is (0.2-0.4):(0.2-0.4), and the ratio of pbd, methanol and acetonitrile is (0.2 mmol-0.4 mmol):(25 mL-35 mL):(25 mL-35 mL).

[0022] Further, in the steps S2 and S3, the time of reflux heating treatment is 3-4 h, and the reflux heating temperature is 65-75°C.

[0023] The third aspect of the present application provides a kind of application of promoting CO2 photo-reduction spin catalytic material in the field of artificial photosynthesis as described above. The spin state of iron center can be chemically modified by counter anion to promote photocatalytic CO2 reduction reaction (CO2RR). The pyrazine group located in the middle of the bridging ligand is expected to be assembled as a two-armed pocket four-metal square supramolecule. The supramolecular metal lattice uses iron atom as the redox and spin crossover active center.

[0024] Compared with the prior art, the present application has the following beneficial effects:

[0025] The present application uses 2,2'-pyrazine dihydrazine thioamide as a ligand, and synthesizes high-activity metal grid supramolecular complexes 1 and 2 by solvent evaporation method with Fe(ClO4)2·xH2O and Fe(CF3SO3)2 respectively. Complex 1 involves a perchlorate ion in crystallization, and each ligand exhibits 2 units of negative charge, so that there is mixed valence iron of Fe Ⅲ and Fe Ⅱ in the crystalline molecules. The average distance between the two adjacent Fe ions is The dihedral angle between the two ligand planes is about 90°, the average bond length of the axial Fe-N bond (N3, N7) is The average bond length of the transverse Fe-N bond (N5, N4) is longer than that of the axial bond The average bond length of the transverse Fe-S bond is forming an axially compressed octahedral structure.

[0026] The average distance between the two adjacent Fe of complex 2 is The dihedral angle between the two ligands is about 90°, the average bond length of the axial Fe-N bond (N3, N7) is The average bond length of the transverse Fe-N bond (N5, N4) is longer than that of the axial bond The average bond length of the transverse Fe-S bond is forming an axially compressed octahedral structure.

[0027] The complex provided by the present application can adjust multiple spin states at a single Fe site in the metal grid supramolecule as a photocatalyst to effectively promote the visible light driven CO2 reduction reaction (CO2RR). Experimental research and theoretical calculation show that the single complete spin state transition of Fe 3+ from low spin (LS, s=1 / 2) to high spin (HS, s=5 / 2) will inhibit the CO2RR activity, which will increase the Fe-3d of the photocatalyst and the O-2 pThe orbital overlap between them, thus reducing the Gibbs free energy of forming key intermediates. The present invention improves the above problems by preparing complexes with three-component mixed-spin states (i.e. HS-Fe 2+ , LS-Fe 3+ and HS-Fe 3+ ).

[0028] The present invention also fine-tunes the ratio of spin states by counter anions, further accelerating the CO2RR rate. Complex 2 holds about 10% more HS sites than complex 1, due to partial spin conversion of active states, after 1h illumination, complex 2 (6.26 mmol g -1 ) exhibits twice faster CO2 to CO yield than complex 1 (2.96 mmol g -1 ), demonstrating an effective strategy to design spin-based photocatalysts for artificial photosynthesis through supramolecular assembly. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention or the prior art, the drawings needed in the embodiment or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments described in the present invention, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0030] Figure 1 X-ray crystal structure of complex 1 (a) and complex 2 (b);

[0031] Figure 2 Infrared spectrum of complex 1 (red line) and complex 2 (black line);

[0032] Figure 3 Powder X-ray diffraction pattern of complex 1 (a) and complex 2 (b);

[0033] Figure 4 Photocatalytic gas production over time of complex 1 (a) and complex 2 (b);

[0034] Figure 5 Cyclic voltammogram of complex 1 (a) and complex 2 (b) under different atmospheres;

[0035] Figure 6 Electron transfer pathway of photocatalytic reduction of CO2 in the catalytic system of the present invention;

[0036] Figure 7 Spin conversion mode in the photocatalytic reaction of the present invention. DETAILED DESCRIPTION

[0037] To further clarify the technical means and effects taken by the present application to achieve the predetermined inventive objectives, the specific embodiments, features and effects of a preparation method of a CO2 light reduction spin catalytic material according to the present application are described in detail as follows. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0038] The reagents involved in the experiment are from the production manufacturers such as Shanghai Lingfeng, etc., and the details are shown in Table 1; the reagents involved are not further purified and are used directly.

[0039] Table 1 Reagent Table

[0040]

[0041]

[0042] The equipment and instruments used in the experiment are shown in Table 2:

[0043] Table 2 Main Instruments

[0044]

[0045] Example 1

[0046] Preparation of ligand pbd: 2-acetylpyrazine (3.05 g, 25 mmol) was added to a double-mouth round-bottom flask, placed in an ice bath, 5.8 mL of anhydrous acetaldehyde and 6.2 mL of concentrated H2SO4 with a concentration of 3.4 mol L -1 were added, 6.0 mL of tert-butyl hydroperoxide was added dropwise, and 54 mL of FeSO4 solution with a concentration of 1.6 mol L -1 was slowly added to the reaction bottle through a constant-pressure dropping funnel, the ice bath was removed after the dropwise addition was completed, and stirring was performed at room temperature for 5 h. After the reaction was completed, extraction was performed, and vacuum distillation was performed to obtain orange powder 2,5-diacetylpyrazine. 2,5-diacetylpyrazine (1.64 g, 10 mmol) and aminothiourea (0.91 g, 10 mmol) were added to 30 mL of anhydrous ethanol, 3 drops of glacial acetic acid were added as a catalyst, and the reaction was stirred at 70°C under reflux for 6 h, then filtered and dried to obtain 2,2'-pyrazine bis-hydrazine methylthioamide yellow powder product.

[0047] Preparation of complex 1 [Fe4(pbd)4]ClO4.CH3OH: The ligand pbd (0.0620 g, 0.2 mmol) obtained from the above synthesis was added to a single neck flask with 90 mL of methanol and heated to 70 °C to obtain a yellow turbid solution. Fe(ClO4)2.xH2O (0.0509 g, 0.2 mmol) was dissolved in 10 mL of methanol and added to the ligand suspension. The solution turned black rapidly and stirring was continued for 3 h. The black solution was cooled to room temperature and filtered. The black crystals were obtained after slow evaporation in a beaker for a week.

[0048] Preparation of complex 2 Fe4(pbd)4.2CH3CN: The ligand pbd (0.0620 g, 0.2 mmol) was added to a round bottom flask with 30 mL of methanol and heated to 70 °C to obtain a yellow turbid solution. Fe(CF3SO3)2(0.7079 g, 0.2 mmol) was dissolved in 30 mL of acetonitrile and added to the ligand suspension. The solution turned black rapidly and stirring was continued for 3 h. The black solution was cooled to room temperature and filtered. The black crystals were obtained after slow evaporation in a beaker for a week.

[0049] Crystallographic data of complex 1, complex 2 were collected on a Bruker APEX-II CCD instrument with graphite monochromated radiation at the corresponding temperature. Data collection, data reduction and unit optimization were performed using two program packages, Bruker Instrument Service v4.2.2 and SAINT V8.34A. The structure of the complex was solved using the SHELXS package and the crystal data was refined by full-matrix least squares method using the SHELXL package. Absorption correction was performed using the multi-scan package SADABS. Hydrogen atoms of the organic ligand were optimized anisotropically on F2 by the riding mode on the SHELXTL package. The crystallographic data of the complex is shown in Table 3.

[0050] Table 3 Crystallographic parameters of the complex

[0051]

[0052]

[0053] a R1=∑(||F0|-|Fc||) / ∑|F0|; b wR2=[∑w(|F0 2 |-|Fc 2 |) 2 / ∑w|F0 2 | 2 ] 1 / 2 ; cGOF = [∑[w(F0 2 -Fc 2 ) 2 ] / (Nobs-Nparams)] 1 / 2 ,based on the dataI>2σ(I).

[0054] Complex 1 is tetragonal, space group P4 / ncc, and the unit cell parameters of the complex are α = 90°, β = 90°, γ = 90°, Z = 4, Since there is one perchlorate ion involved in the crystallization, and each ligand exhibits 2 units of negative charge, it makes the mixed valence iron of Fe Ⅲ and Fe Ⅱ exist in the crystalline molecule. The average distance between the two adjacent Fe ions is The dihedral angle between the two ligands is about 90°, and the average bond length of the axial Fe-N bond (N3, N7) is The average bond length of the transverse Fe-N bond (N5, N4) is longer than that of the axial bond The average bond length of the transverse Fe-S bond is forming an axially compressed octahedral structure.

[0055] The single crystal structure of complex 2 is Fe4(pbd)4·2CH3CN, wherein pbd is 2,2'-pyrazine dihydrazine methanesulfonamide. In the material, complex 2 is tetragonal, space group P4 / ncc, and the unit cell parameters of the complex are α = 90°, β = 90°, γ = 90°, Z = 4, The average distance between the two adjacent Fe is The dihedral angle between the two ligands is about 90°, and the average bond length of the axial Fe-N bond (N3, N7) is The average bond length of the transverse Fe-N bond (N5, N4) is longer than that of the axial bond The average bond length of the transverse Fe-S bond is forming an axially compressed octahedral structure.

[0056] Infrared absorption spectrum analysis: as shown in Figure 2 , the red spectrum is the infrared spectrum of complex 1, and complex 1 has a medium intensity peak at 1100 cm -1 , which is the absorption peak of the crystalline anion ClO4 - , while complex 2 does not, which is consistent with the crystal structure, and 1600 cm-1 The peak at is the stretching vibration peak of the Schiff base C=N bond on the ligand.

[0057] Powder X-ray diffraction analysis: Figure 3 As shown, Figure 3 As shown in (a), the red spectrum is the powder diffraction test data of complex 1, and the black spectrum is the data simulated by the software. It can be seen that the experimental value and the simulated value of complex 1 are in good agreement, indicating that the complex is pure; Figure 3 As shown in (b), the red spectrum is the powder diffraction data of complex 2, and the black spectrum is the data simulated by the software. It can be seen that the experimental and simulated values ​​of complex 2 are in good agreement, indicating that the complex is pure.

[0058] Catalytic performance analysis of complex 1 and complex 2: Complex 1 or complex 2 was added as catalyst (1 mg) into a photocatalytic reaction vessel, tris(2,2'-bipyridyl)ruthenium(II) chloride hexahydrate (1 mg) was used as photosensitizer, 1,3-dimethyl-2-phenylbenzimidazolidine (14 mg) was used as sacrificial agent, and the solvent system was acetonitrile:water = 4.8:0.2. CO2 was introduced into the photocatalytic system for 15 min, and the photocatalytic reaction was carried out under a light intensity of 100 mW cm -2 The samples were irradiated for 5 h and then detected by gas chromatography.

[0059] Analysis of gas production over time: Figure 4 As shown, gaseous products such as CO and H2 were analyzed by gas chromatography. Liquid products were detected by ion chromatography, but only trace amounts of HCOOH were detected. For the CO2 reduction reaction, as the illumination time increased, both complexes 1 and 2 tended to stabilize at 3 h. With complex 1 as the photocatalyst, the CO yield reached 2.96 mmol g after 1 hour of initial light irradiation. -1 However, when complex 2 was used as catalyst, the CO yield reached 6.26 mmol g -1 , more than twice that of complex 1.

[0060] Cyclic voltammetry curve analysis: Figure 5 As shown, in order to further reveal the electron transfer between the photocatalyst and CO2 reduction, cyclic voltammetry (CV) tests of the photocatalyst were carried out under N2 and CO2 atmospheres, respectively. Under N2 atmosphere, the CV of complexes 1 and 2 showed three irreversible reduction waves. For complex 1, the Fe 3+ / 2+ , -0.21V Fe 2+ / 1+ and Fe at -0.31V 1+ / 0 ; For complex 2, Fe 3+ / 2+ , -0.35V Fe 2+ / 1+and -0.58V Fe 1+ / 0 Under CO2 atmosphere, the reduction current of complex 1 is slightly lower than that under N2 atmosphere, indicating that the electron transfer activity of complex 1 to CO2 is poor. Compared with the current intensity of complex 2 under N2 atmosphere, the reduction current of complex 1 under Fe2 atmosphere is slightly lower than that under N2 atmosphere, indicating that the electron transfer activity of complex 1 to CO2 is poor. +1 / 0 After the redox event, the current intensity of complex 2 in CO2 atmosphere suddenly increases, and Fe 2+ / 1 + and Fe 1+ / 0 The redox potential of the photocatalyst 2 showed a significant positive shift, indicating that complex 2 is more active in catalyzing the reduction of CO2. Therefore, from the experimental observation of the CV curve, complex 2 has a stronger electron transfer activity for the reduction of CO2 than complex 1 as a photocatalyst.

[0061] Electron transfer pathway analysis: Figure 6 As shown in Figure 3, the quenching mode of activated RuPS* can be classified as an oxidative quenching pathway. The photocatalytic CO2RR is initiated by electron transfer from photoexcited RuPS* to the photocatalyst, which produces reduced Fe, thereby injecting electrons into the CO2RR.

[0062] Analysis of spin transition mode in photoreduction reaction: Figure 7 As shown in the figure, the active Fe sites of complexes 1 and 2 adopt an unprecedented three-component mixed spin state (i.e., HS-Fe 2+ LS-Fe 3+ and HS-Fe 3+ ), where the ratio of the spin states can be finely tuned by the counter anion. Therefore, the mixed spin metal grid provides an ideal model to understand the spin state effect of the active center after photocatalysis. Compared with complex 1, complex 2 only undergoes a subtle spin transition of about 10% of the Fe sites, which greatly improves the CO2RR rate. 3+ The iron metal grid with (HS, s = 5 / 2) sites (complex 2) has a higher CO2RR rate than the more low-spin Fe 3+ The iron metal grid (complex 1) has two times more (LS,s=1 / 2) sites.

[0063] Example 2

[0064] Preparation of ligand PBD: 2-acetylpyrazine (3.05 g, 25 mmol) was added to a double-necked round-bottom flask, placed in an ice bath, and 5.8 mL of anhydrous acetaldehyde and 6.2 mL of 3.4 mol·L -1 of H2SO4, add 6.0mL of tert-butyl peroxide, and add 54mL of 1.6mol L -1The reaction flask was placed in an ice bath and 54 mL of a 1.6 M solution of FeSO4 was added dropwise through a constant pressure dropping funnel. The ice bath was removed after the addition was complete and the reaction was stirred at room temperature for 5 h. After the reaction was complete, the product was extracted and distilled under reduced pressure to yield 2,5-diacetylpyrazine as an orange powder. The 2,5-diacetylpyrazine (1.64 g, 10 mmol) and thiosemicarbazide (0.91 g, 10 mmol) were added to 30 mL of anhydrous ethanol and 3 drops of glacial acetic acid were added as a catalyst. The reaction was stirred at reflux at 70 °C for 6 h and then filtered and dried to yield the 2,2'-pyrazine dihydrazine thiosemicarbazide as a yellow powder.

[0065] Preparation of complex (1) [Fe4(pbd)4]ClO4»CH3OH: The ligand pbd (0.0930 g, 0.3 mmol) was added to a single neck flask with 90 mL of methanol and heated to 70 °C to yield a yellow turbid solution. Fe(CIO4)2»xH2O (0.0762 g, 0.3 mmol) was dissolved in 10 mL of methanol and added to the ligand suspension. The solution quickly turned black and was stirred at reflux for 3 h. The solution was cooled to room temperature, filtered and left to slowly evaporate in a beaker. After one week, black square shaped crystals were obtained.

[0066] Preparation of complex (2) Fe4(pbd)4»2CH3CN: The ligand pbd (0.0930 g, 0.3 mmol) was added to a round bottom flask with 30 mL of methanol and heated to 70 °C to yield a yellow turbid solution. Fe(CF3SO3)2(0.1062 g, 0.3 mmol) was dissolved in 30 mL of acetonitrile and added to the ligand suspension. The solution quickly turned black and was stirred for 3 h. The black solution was cooled to room temperature, filtered and left to slowly evaporate in a beaker. After one week, black square shaped crystals were obtained.

[0067] Example 3

[0068] Preparation of ligand pbd: 2-acetylpyrazine (3.05 g, 25 mmol) was added to a two neck round bottom flask and placed in an ice bath. 5.8 mL of anhydrous acetaldehyde and 6.2 mL of concentrated H2SO4 at a concentration of 3.4 mol L -1 were added dropwise. A 54 mL solution of FeSO4 at a concentration of 1.6 mol L -1 was added dropwise through a constant pressure dropping funnel. The ice bath was removed after the addition was complete and the reaction was stirred at room temperature for 5 h. After the reaction was complete, the product was extracted and distilled under reduced pressure to yield 2,5-diacetylpyrazine as an orange powder. The 2,5-diacetylpyrazine (1.64 g, 10 mmol) and thiosemicarbazide (0.91 g, 10 mmol) were added to 30 mL of anhydrous ethanol and 3 drops of glacial acetic acid were added as a catalyst. The reaction was stirred at reflux at 70 °C for 6 h and then filtered and dried to yield the 2,2'-pyrazine dihydrazine thiosemicarbazide as a yellow powder.

[0069] Preparation of complex (1) [Fe4(pbd)4]ClO4.CH3OH: The ligand pbd (0.1240 g, 0.4 mmol) obtained from the above synthesis was added to a single-neck flask with 95 mL of methanol and heated to 70 °C to obtain a yellow turbidity. Fe(ClO4)2.xH2O (0.1019 g, 0.4 mmol) was dissolved in 10 mL of methanol and added to the ligand suspension. The solution turned black quickly, and the reflux stirring was continued for 3 h before cooling to room temperature. Filtration was performed, and the black crystals were obtained by slow evaporation in a beaker for a week.

[0070] Preparation of complex (2) Fe4(pbd)4.2CH3CN: The ligand pbd (0.1240 g, 0.4 mmol) was added to a round-bottom flask with 35 mL of methanol and heated to 70 °C to obtain a yellow turbidity. Fe(CF3SO3)2 (0.1415 g, 0.4 mmol) was dissolved in 35 mL of acetonitrile and added to the ligand suspension. The solution turned black quickly, and the stirring was continued for 3 h before cooling to room temperature. Filtration was performed, and the black crystals were obtained by slow evaporation in a beaker for a week.

[0071] The reaction concentration was increased in Examples 2 and 3, which was more prone to form a precipitate, but the obtained crystals were less rigid and had weaker diffraction.

[0072] This work reports that the multi-spin state of a single Fe site in a metal lattice supramolecule can effectively promote the visible light-driven CO2 reduction reaction (CO2RR). Experimental research and theoretical calculations show that the CO2RR activity is triggered by the spin state transition of Fe 3+ from low spin (LS, s = 1 / 2) to high spin (HS, s = 5 / 2), which increases the orbital overlap between the Fe-3d of the photocatalyst and the O-2p of the CO2 substrate, thereby reducing the Gibbs free energy of the formation of the key intermediate. The complex of the present invention improves the above problem by three-component mixed spin states (i.e., HS-Fe 2+ , LS-Fe 3+ and HS-Fe 3+ ). The present invention further adjusts the proportion of the spin state of the complex by the counter anion. Due to the partial spin transition of the active lattice, the CO2 to CO yield (6.26 mmol g -1 ) of the supramolecular metal lattice containing only about 10% HS sites is twice as fast as that of the LS lattice (2.96 mmol g -1 ) after 1 h of illumination. This work proves an effective strategy for designing spin-based photocatalysts through supramolecular assembly to promote artificial photosynthesis.

[0073] With the above ideal embodiments according to the present application as the inspiration, through the above description, relevant staff can make various changes and modifications without deviating from the technical idea of the present application. The technical scope of the present application is not limited to the content of the specification, and must be determined according to the scope of the claims.

Claims

1. A spin-catalytic material for promoting photo-reduction of CO2, characterized in that, The single crystal structure molecular formula of the spin catalytic material is [Fe4(pbd)4]ClO4·CH3OH or Fe4(pbd)4·2CH3CN, wherein H2pbd is 2,2'-pyrazine dihydrazine methanesulfamide, and a structural formula is shown in the following formula I; Formula I.

2. The spinocat material to facilitate CO2 photoreduction according to claim 1, wherein, The single crystal structure spin-catalytic material with a molecular formula of [Fe4(pbd)4]ClO4·CH3OH is tetragonal, and a space group is P4 / ncc , a cell parameter is a = 16.4086(1) Å, b = 16.4086(1) Å, c = 29.5402(6) Å, α = 90°, β = 90°, Gamma = 90°, Z =4, V = 7953.47(19) Å 3 .

3. The spinocat material to facilitate CO2 photoreduction according to claim 1, wherein, The single crystal structure spin-catalytic material with a molecular formula of Fe4(pbd)4·2CH3CN is tetragonal, and a space group is P4 / ncc , a cell parameter is a = 16.60710(10) Å, b = 16.60710(10) Å, c = 29.6272(3) Å, α = 90°, β = 90°, Gamma = 90°, Z = 4, V = 8171.06(13) Å 3 .

4. A method for producing a spin catalyst material for promoting photo-reduction of CO2 according to any one of claims 1 to 3, characterized by, The method comprises the following steps: S1, preparing an organic ligand pbd: 2,5-diacetylpyrazine and aminothiourea are added to anhydrous ethanol, glacial acetic acid is added as a catalyst, and after heating reflux stirring reaction, filtration, drying, and 2,2'-pyrazine dihydrazine methanesulfamide yellow powder is obtained; the 2,5-diacetylpyrazine is shown in the following formula II: Formula II; S2, preparing a single crystal structure spin catalytic material with a molecular formula of [Fe4(pbd)4]ClO4·CH3OH: the ligand pbd is added to a single-neck flask containing methanol and heated to 70 DEG C to obtain a yellow suspension, Fe(ClO4)2·xH2O is added to the ligand suspension, the solution quickly turns black, after heating treatment, cooling to room temperature, filtration, and slow evaporation in a beaker, black square crystals are obtained; S3, preparing a single crystal structure spin catalytic material with a molecular formula of Fe4(pbd)4·2CH3CN: the ligand pbd is added to a round-bottom flask containing methanol and heated to 70 DEG C to obtain a yellow suspension, Fe(CF3SO3)2 is dissolved in acetonitrile and then added to the ligand suspension, the solution quickly turns black, after heating treatment, cooling to room temperature, filtration, and slow evaporation in a beaker, black square crystals are obtained.

5. The method for facilitating the preparation of a spinocatalyst material for the photo-reduction of CO2 according to claim 4, wherein, In the step S1, the molar ratio of the 2,5-diacetylpyrazine and aminothiourea is (9.9 ~ 10.1) : (9.9 ~ 10.1), and the volume ratio of the ethanol and glacial acetic acid is (29.9 mL ~ 30.1 mL) : (0.3 mL ~ 0.4 mL).

6. The method for facilitating the preparation of a spinocatalyst material for the photo-reduction of CO2 according to claim 4, wherein, In the step S1, the heating reflux stirring reaction time is 6-7h, and the temperature is 70 DEG C ~ 80 DEG C.

7. The method for facilitating the preparation of a spinocatalyst material for the photo-reduction of CO2 according to claim 4, wherein, In the step S2, the molar ratio of the pbd and Fe(ClO4)2·xH2O is (0.2 ~ 0.4) : (0.2 ~ 0.4), and the amount ratio of the methanol and pbd is (95 mL ~ 105 mL) : (0.2 mmol ~ 0.4 mmol).

8. The method for facilitating the preparation of a spinocatalyst material for the photo-reduction of CO2 according to claim 4, wherein, In the step S3, the molar ratio of the pbd and Fe(CF3SO3)2 is (0.2 ~ 0.4) : (0.2 ~ 0.4), and the amount ratio of the pbd, methanol and acetonitrile is (0.2 mmol ~ 0.4 mmol) : (25 mL ~ 35 mL) : (25 mL ~ 35 mL).

9. The method for facilitating the preparation of a spinocatalyst material for the photo-reduction of CO2 according to claim 4, wherein, In the steps S2 and S3, the heating treatment time is 3 h ~ 4 h, and the temperature is 65 DEG C ~ 75 DEG C.

10. Use of a spin-catalyst material facilitating the photo-reduction of CO2 as claimed in any one of claims 1 to 3 in the field of artificial photosynthesis.

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