Samarium complex as well as preparation method and application thereof

Abstract

The invention provides a samarium complex as well as a preparation method and application thereof. The samarium complex takes samarium as a coordination center ion and diphenyl phosphonic acid as a ligand. According to the samarium complex, the synthesis method is simple, reaction conditions are mild, raw materials are easy to obtain, and the catalytic effect of the samarium complex on hydrogen production through photocatalytic splitting of water is excellent.

Description

Technical Field

[0001] The present invention relates to the field of material science, and specifically to samarium complexes, preparation methods thereof and applications thereof. Background Art

[0002] In recent years, with the continuous application of non-renewable energy such as coal, energy shortage and environmental pollution have become two major problems that mankind needs to solve. It is particularly important to develop and manufacture environmentally friendly, sustainable, reliable and benign alternative energy sources. Therefore, the reaction of producing hydrogen from water through photocatalysis has attracted the attention of experts and scholars.

[0003] On the other hand, phosphonic acid complexes have good chemical stability and thermal stability and are widely used in the fields of photodegradation of dyes, photoreduction of carbon dioxide, photolysis of water to produce hydrogen, etc. Among them, Yang's research group prepared layered aluminum (III), iron (III), and zinc (II) complexes with phenylphosphonic acid as a ligand. These compounds have good flame retardant functions and are a good class of flame retardants, but the application of these complexes in the fields of photodegradation of dyes, photoreduction of carbon dioxide, photolysis of water to produce hydrogen was not mentioned. Wang's research group used phenylphosphonic acid as a ligand to form a complex with cobalt and nickel as transition metal elements, and used the prepared complex as a catalyst in the active reaction of photocatalytic hydrogen production and photoreduction of carbon dioxide. However, the catalytic activity is very limited. That is, the application effect of phosphonic acid metal complexes in existing research on photocatalytic hydrogen production still has room for improvement. At present, the design and synthesis of a new type of metal complex for photocatalytic water splitting to produce hydrogen is an important problem to be solved in this field. Summary of the invention

[0004] 1. Technical issues to be resolved In view of the above technical problems, the present invention provides a samarium complex having a simple synthesis method, mild reaction conditions, readily available raw materials and extremely excellent catalytic effect of photocatalytic water splitting to produce hydrogen, a preparation method thereof and applications thereof.

[0005] (II) Technical solution The invention provides a samarium complex, which uses samarium as a coordination center ion and diphenylphosphonic acid as a ligand.

[0006] The samarium complex of the present invention has the molecular formula [Sm(OPPh2O)3] n Wherein, n is a samarium complex unit. The samarium complex of the present invention has a simple synthesis method, mild reaction conditions, readily available raw materials, and good photocatalytic water splitting hydrogen production activity and stability.

[0007] In addition, the present invention also provides a method for preparing a samarium complex, which comprises subjecting a samarium metal salt to a solvothermal reaction with diphenylphosphonic acid in a solvent to obtain the samarium complex.

[0008] That is, the present invention proposes a solvent thermal reaction to prepare samarium diphenylphosphonate from samarium metal salt and diphenylphosphonic acid. The method is carried out in a closed system, the reaction is simple and easy to control, and the impact of solvent volatilization on the environment can be effectively prevented.

[0009] The metal salt of samarium is samarium chloride hexahydrate or samarium nitrate hexahydrate, among which samarium chloride hexahydrate is preferred.

[0010] The preparation method of samarium of the present invention uses samarium metal salt as raw material, and particularly preferably uses samarium chloride hexahydrate as raw material for preparation, because the raw material is easily available and the preparation process is stable.

[0011] In addition, the molar ratio of the samarium metal salt to diphenylphosphonic acid is 1:1-5, more preferably 1:3.

[0012] The invention can stably prepare samarium diphenylphosphonate by controlling the molar ratio of samarium metal salt to diphenylphosphonic acid, and the preparation process is controllable. The prepared samarium diphenylphosphonate has excellent photocatalytic water splitting hydrogen production reaction activity and stability.

[0013] In addition, the solvent is anhydrous ethanol.

[0014] In addition, the reaction temperature of the solvothermal reaction is 175-185°C, more preferably 180°C.

[0015] In addition, the reaction time of the solvothermal reaction is 70 to 75 hours, more preferably 72 hours.

[0016] The present invention can stably and controllably prepare samarium diphenylphosphonate by controlling the solvent, reaction temperature and reaction time of the solvothermal reaction, and the prepared samarium diphenylphosphonate has excellent photocatalytic water splitting hydrogen production reaction activity and stability.

[0017] In addition, the present invention also provides an application of the samarium complex, which uses the samarium complex as a catalyst in a photocatalytic water splitting reaction to produce hydrogen.

[0018] In addition, when the samarium complex of the present invention is used as a catalyst in the photocatalytic splitting of water to produce hydrogen, triethanolamine is preferably used as a sacrificial agent. When triethanolamine is used as a sacrificial agent at the same time, the ratio of the sacrificial agent to water is 1:99 by volume.

[0019] (III) Beneficial effects According to the present invention, a samarium complex with a simple synthesis method, mild reaction conditions, readily available raw materials, good photocatalytic water splitting hydrogen production activity and stability can be provided, as well as a preparation method and application of the samarium complex. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1This is the mechanism of the photocatalytic splitting of water to produce hydrogen by the samarium diphenylphosphonate complex of the present invention.

[0021] Figure 2 1 is a scanning electron microscope image of the samarium diphenylphosphonate complex prepared in Example 1.

[0022] Figure 3 This is the X-ray diffraction pattern of the samarium diphenylphosphonate complex prepared in Example 1.

[0023] Figure 4 This is the infrared absorption spectrum of the samarium diphenylphosphonate complex prepared in Example 1.

[0024] Figure 5 This is the UV-visible diffuse reflectance spectrum of the samarium diphenylphosphonate complex prepared in Example 1.

[0025] Figure 6 This is the reaction result of photocatalytic water splitting to produce hydrogen.

[0026] Figure 7 Schematic diagram of the structural stability of the samarium diphenylphosphonate complex prepared in Example 1 before and after the photocatalytic water splitting reaction to produce hydrogen.

[0027] Figure 8 This is the infrared absorption spectrum of the samarium diphenylphosphonate complex prepared in Example 2.

[0028] Fig. 9 This is the X-ray diffraction pattern of the samarium diphenylphosphonate complex prepared in Example 2.

[0029] Fig.10 This is the infrared absorption spectrum of the samarium diphenylphosphonate complex prepared in Example 3.

[0030] Fig.11 This is the X-ray diffraction pattern of the samarium diphenylphosphonate complex prepared in Example 3.

[0031] Fig.12 This is the infrared absorption spectrum of the samarium diphenylphosphonate complex prepared in Example 4.

[0032] Fig.13 This is the X-ray diffraction pattern of the samarium diphenylphosphonate complex prepared in Example 4. DETAILED DESCRIPTION

[0033] The present invention is described in detail below with reference to the accompanying drawings and by enumerating embodiments. The embodiments are merely illustrative and do not limit the present invention. Any solution having substantially the same composition and exerting the same effect as the technical concept described in the claims of the present invention is included in the technical scope of the present invention.

[0034] The invention provides a samarium complex, which uses samarium as a coordination center ion and diphenylphosphonic acid as a ligand, and is named samarium diphenylphosphonate complex, and has a molecular formula of [Sm(OPPh2O)3] n , wherein n is a samarium complex unit.

[0035] The samarium diphenylphosphonate of the present invention is prepared by subjecting a samarium metal salt to a solvothermal reaction with diphenylphosphonic acid in a solvent, and specifically, the following reaction formula can be shown.

[0036] The preparation method of the samarium diphenylphosphonate complex of the present invention specifically includes the following steps: (1) respectively mixing samarium metal salt, diphenylphosphonic acid (DPPA) and a solvent in a certain molar ratio, and stirring the mixture uniformly at room temperature; (2) transferring the mixture into an autoclave, placing the autoclave at a specified temperature, and reacting; (3) After the reaction is completed, the mixture is naturally cooled to room temperature, filtered, washed and dried to obtain a samarium diphenylphosphonate complex.

[0037] Among them, the metal salt of samarium is samarium chloride hexahydrate or samarium nitrate hexahydrate, and samarium chloride hexahydrate is more preferred.

[0038] The molar ratio of the samarium metal salt to diphenylphosphonic acid is 1:1-5, more preferably 1:3. The solvent is anhydrous ethanol. In addition, the reaction temperature of the solvothermal reaction is 175-185°C, more preferably 180°C. In addition, the reaction time of the solvothermal reaction is 70-75, more preferably 72 hours.

[0039] Wherein, the autoclave is preferably a stainless steel autoclave lined with polytetrafluoroethylene.

[0040] In addition, the mechanism of photocatalytic water splitting and hydrogen production of the samarium diphenylphosphonate complex of the present invention is as follows Figure 1As shown. In the process of photocatalytic water splitting to produce hydrogen, there is a mechanism of electron transfer from the ligand to the metal. The specific process is as follows: Under the irradiation of ultraviolet visible light, the benzene ring on diphenylphosphonic acid absorbs photons to generate photogenerated electrons-holes. The electrons on the benzene ring of diphenylphosphonic acid are transferred to Sm (III) to form Sm (II). At the same time, the holes are captured by the sacrificial agent triethanolamine. Sm (II) has a high reaction activity and can undergo an oxidation-reduction reaction with water to generate hydrogen, thereby completing the photocatalytic water splitting reaction to produce hydrogen. When the samarium complex of the present invention is used as a catalyst in the photocatalytic water splitting reaction to produce hydrogen, it is preferred to use triethanolamine as a sacrificial agent at the same time. When the samarium complex of the present invention is used as a catalyst in the photocatalytic water splitting reaction to produce hydrogen, its amount is not particularly limited and is the usual catalyst amount. From the perspective of achieving excellent catalysis, it is preferred to use 50 mg of the samarium complex of the present invention for every 99 ml of water. When triethanolamine is used as a sacrificial agent at the same time, the ratio of the sacrificial agent to water is 1:99 by volume.

[0041] The present invention is further described by way of examples given below.

[0042] Example 1 (1) Preparation of samarium diphenylphosphonate complex ① Dissolve samarium chloride hexahydrate SmCl3·6H2O (0.1824 g, 0.5 mmol) and diphenylphosphonic acid DPPA (0.3273 g, 1.5 mmol) in 7 mL of anhydrous ethanol, and stir the mixture at room temperature for 20 min until it becomes homogeneous.

[0043] ② The mixture was transferred to a 15 mL polytetrafluoroethylene-lined stainless steel autoclave, and the autoclave was placed in a muffle furnace. The autoclave was kept at a constant temperature of 180°C for 72 hours.

[0044] ③After the reaction time is over, take out the autoclave, cool it naturally to room temperature, open the autoclave, filter, wash with anhydrous ethanol, and dry in air to obtain 0.19g of white sample samarium diphenylphosphonate with a yield of 49%. Labeled as SmDPPA. The elemental analysis results are C53.61, H4.06 (theoretical values ​​C53.92, H3.77).

[0045] (2) Characterization of samarium diphenylphosphonate complexes ①Scanning electron microscopy (SEM) analysis The morphology of the samarium diphenylphosphonate complex prepared in Example 1 was analyzed using a Hitachi S-3400N tungsten filament scanning electron microscope. The results are shown in Figure 2 .

[0046] like Figure 2As shown, the morphology of the samarium diphenylphosphonate complex is rod-shaped with a smooth surface and uniform distribution.

[0047] ②X-ray diffraction test The phase of the samarium diphenylphosphonate complex prepared in Example 1 was measured using an Ultima IV X-ray diffractometer produced by Rigaku.

[0048] The test conditions are as follows: X-ray tube type: Cu target, scanning mode: theta / 2theta goniometer, detector: D / texUltra detector, scanning range: 5~80°, scanning speed: 2° / min, step length: 0.01°. The results are shown in Figure 3 .

[0049] like Figure 3 As shown, the samarium diphenylphosphonate complex is a crystalline compound, and there is a strong diffraction peak at 2θ=7.28°, which is a characteristic diffraction peak belonging to metal samarium diphenylphosphonate.

[0050] ③Infrared absorption spectrum measurement The samarium diphenylphosphonate complex prepared in Example 1 was qualitatively analyzed using a Nicolet iS10 Fourier transform infrared spectrometer from Thermo Scientific, USA. The KBr tablet method was used and the spectral scanning range was 400-4000 cm -1 The results are shown in Figure 4 .

[0051] Depend on Figure 4 It can be seen that at 3055cm -1 and 1593cm -1 There is a strong absorption peak at 1437cm -1 There is a strong absorption peak at 1051cm, which is the characteristic absorption peak of the vibration of the benzene ring skeleton; -1 There is a strong absorption peak at , which is the characteristic absorption peak of Sm-OP. Therefore, the characteristic absorption peak on the infrared absorption spectrum further confirms the existence of important functional groups in the composition and structure of samarium diphenylphosphonate.

[0052] ④ Characterization of optical properties The diffuse reflectance analysis of the samarium diphenylphosphonate complex prepared in Example 1 was performed using a Lambda 365 UV-visible spectrophotometer from PerkinElmer, USA. The results are shown in Figure 5 .in, Figure 5 (a) is the UV-visible diffuse reflectance spectrum of diphenylphosphonic acid and samarium diphenylphosphonate. Figure 5(b) is the band gap spectrum of samarium diphenylphosphonate.

[0053] like Figure 5 As shown, the absorption of diphenylphosphonic acid and samarium diphenylphosphonate is mainly located in the ultraviolet region. By using the Tauc equation (αhν=A(hν-Eg) 2 ) and the UV-visible absorption data of the compound by making (αhν) 1 / 2 By taking a tangent to the curve and extending it to the x-axis, the band gap of the complex can be determined. Using this treatment, the band gap of samarium diphenylphosphonate was determined to be 4.38 eV.

[0054] (3) Photocatalytic performance test of samarium diphenylphosphonate complex The photocatalytic splitting of water to produce hydrogen was tested in a fully automatic online trace gas analysis closed exhaust circulation system. A 300 W xenon lamp was used as the light source. The specific experimental steps are as follows: 50 mg of the samarium diphenylphosphonate complex prepared in Example 1 and 1 mL of triethanolamine (TEOA) were mixed in 99 mL of water and stirred continuously. The suspension was sealed in a quartz container (200 mL), purged with nitrogen for 30 minutes to remove residual oxygen, and the reaction temperature was maintained at 20°C with cooling water. The product was periodically analyzed using a Shimadzu GC-14C gas chromatograph and a TCD detector. The results are shown in Figure 6 .

[0055] like Figure 6 As shown in a, after 3 h of UV-visible light irradiation, the hydrogen production of the samarium diphenylphosphonate complex test group was 109.9 μmol / g; Figure 6 As shown in b, the cycle performance test results show that the samarium diphenylphosphonate complex still maintains a relatively stable hydrogen production capacity after 4 cycles of 12 hours, and the hydrogen production efficiency remains at 96%.

[0056] In addition, XRD was further used to evaluate the stability of the samarium diphenylphosphonate complex in catalytic water splitting to produce hydrogen. Specifically, the structure of the samarium diphenylphosphonate complex was determined by XRD before and after the catalytic water splitting reaction to produce hydrogen. The two spectra were compared and the results are shown in Figure 7 .like Figure 7 As shown, by comparing the XRD spectra of the complex before and after photocatalytic hydrogen production, it can be seen that the XRD spectrum of samarium diphenylphosphonate before and after photocatalytic hydrogen production remains basically unchanged, which indicates that the complex has good stability.

[0057] Example 2 ① Dissolve samarium chloride hexahydrate SmCl3·6H2O (0.1824 g, 0.5 mmol) and diphenylphosphonic acid DPPA (0.1090 g, 0.5 mmol) in 7 mL of anhydrous ethanol, and stir the mixture at room temperature for 20 min until it becomes homogeneous.

[0058] ② The mixture was transferred to a 15 mL polytetrafluoroethylene-lined stainless steel autoclave, and the autoclave was placed in a muffle furnace. The autoclave was kept at a constant temperature of 175°C for 72 hours.

[0059] ③ After the reaction time is over, the autoclave is taken out and cooled naturally to room temperature. The autoclave is opened, filtered, washed with anhydrous ethanol, and dried in air to obtain 0.16 g of a white sample of samarium diphenylphosphonate, which is labeled as SmDPPA.

[0060] The infrared absorption spectrum of samarium diphenylphosphonate obtained is as follows Figure 8 The X-ray diffraction pattern of the obtained samarium diphenylphosphonate is shown as Fig. 9 shown.

[0061] Example 3 ① Dissolve samarium chloride hexahydrate SmCl3·6H2O (0.1824 g, 0.5 mmol) and diphenylphosphonic acid DPPA (0.5455 g, 2.5 mmol) in 10 mL of anhydrous ethanol, and stir the mixture at room temperature for 20 min until it becomes homogeneous.

[0062] ② The mixture was transferred to a 15 mL polytetrafluoroethylene-lined stainless steel autoclave, and the autoclave was placed in a muffle furnace. The autoclave was kept at a constant temperature of 185°C for 75 hours.

[0063] ③ After the reaction time is over, the autoclave is taken out and cooled naturally to room temperature. The autoclave is opened, filtered, washed with anhydrous ethanol, and dried in air to obtain 0.15 g of a white sample of samarium diphenylphosphonate, which is labeled as SmDPPA.

[0064] The infrared absorption spectrum of samarium diphenylphosphonate obtained is as follows Fig.10 The X-ray diffraction pattern of the obtained samarium diphenylphosphonate is shown as Fig.11 shown.

[0065] Example 4 ① Dissolve samarium nitrate hexahydrate Sm(NO3)3·6H2O (0.2222 g, 0.5 mmol) and diphenylphosphonic acid DPPA (0.3273 g, 1.5 mmol) in 7 mL of anhydrous ethanol, and stir the mixture at room temperature for 20 min until it becomes homogeneous.

[0066] ② The mixture was transferred to a 15 mL polytetrafluoroethylene-lined stainless steel autoclave, and the autoclave was placed in a muffle furnace. The autoclave was kept at a constant temperature of 180°C for 70 hours.

[0067] ③ After the reaction time is over, the autoclave is taken out and cooled naturally to room temperature. The autoclave is opened, filtered, washed with anhydrous ethanol, and dried in air to obtain 0.15 g of a white sample of samarium diphenylphosphonate, which is labeled as SmDPPA.

[0068] The infrared absorption spectrum of samarium diphenylphosphonate obtained is as follows Fig.12 The X-ray diffraction pattern of the obtained samarium diphenylphosphonate is shown as Fig.13 shown.

[0069] Comparative Example 1 Dissolve cobalt chloride hexahydrate CoCl2·6H2O (0.1190 g, 0.5 mmol) and phenylphosphonic acid (PPA) (0.0790 g, 0.5 mmol) in 7 mL of anhydrous ethanol. Stir the mixture at room temperature for 20 min until it is uniform and place it in a 15 mL polytetrafluoroethylene-lined stainless steel autoclave. Keep it at 180 ° C for 72 h and cool it naturally to room temperature. Filter, wash with anhydrous ethanol, and dry in air to obtain phenyl cobalt phosphate.

[0070] The phenyl cobalt phosphate prepared in this way was used to replace the samarium diphenylphosphonate used in the photocatalytic performance test of the samarium diphenylphosphonate complex (3) in Example 1, and a test of photocatalytic water splitting to produce hydrogen was carried out under the same conditions. The results showed that the phenyl cobalt phosphate had no catalytic activity.

[0071] Comparative Example 2 Nickel phenylphosphonate was prepared in the same manner as cobalt phenylphosphonate. Nickel chloride hexahydrate NiCl2·6H2O (0.1188 g, 0.5 mmol), PPA (0.0790 g, 0.5 mmol) and 7 mL of anhydrous ethanol were mixed. Nickel phenylphosphonate was finally obtained by treatment and collection in the same manner as cobalt phenylphosphonate.

[0072] The nickel phenylphosphonate prepared in this way was used to replace the samarium diphenylphosphonate used in "(3) Photocatalytic performance test of samarium diphenylphosphonate complex" in Example 1, and a test of photocatalytic water splitting to produce hydrogen was carried out under the same conditions. The result showed that the nickel phenylphosphonate had no catalytic activity.

Claims

1. A samarium complex, characterized in that: The samarium complex takes samarium as the coordination center ion and diphenylphosphonic acid as the ligand.

2. The method for preparing the samarium complex according to claim 1, characterized in that: The samarium metal salt and diphenylphosphonic acid are subjected to a solvothermal reaction in a solvent to obtain the samarium complex.

3. The preparation method according to claim 2, characterized in that: The metal salt of samarium is samarium chloride hexahydrate or samarium nitrate hexahydrate.

4. The preparation method according to claim 2, characterized in that: The molar ratio of the samarium metal salt to diphenylphosphonic acid is 1:1-5.

5. The preparation method according to claim 4, characterized in that: The molar ratio of the samarium metal salt to diphenylphosphonic acid is 1:

3.

6. The preparation method according to claim 2, characterized in that: The solvent is anhydrous ethanol.

7. The preparation method according to claim 2, characterized in that: The reaction temperature of the solvothermal reaction is 175-185°C.

8. The preparation method according to claim 2, characterized in that: The reaction time of the solvent thermal reaction is 70 to 75 hours.

9. The use of the samarium complex according to any one of claims 1 to 8, characterized in that: The samarium complex is used as a catalyst in a photocatalytic water splitting reaction to produce hydrogen.

10. The use of the samarium complex according to claim 9, characterized in that: Triethanolamine was used as the sacrificial agent.

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