Novel neodymium metal complex and synthesis method thereof

Abstract

The invention relates to a neodymium complex [NdL (H2O) 2]. 3H2O, HL = 1, 3, 5-tri (carboxyl methoxy) benzene. An asymmetric structural unit of the neodymium complex is composed of an Nd < 3 + >, a completely protonated carboxylic acid ligand, water molecules with two structures and three free water molecules. A central metal ion Nd < 3 + > in the molecule, eight carboxylic acid oxygen atoms on five ligands and oxygen atoms on two water molecules are subjected to ten-coordination to form a double-cap tetragonal reverse prism structure, and chains are orderly stacked into a three-dimensional structure through ligand oxygen bridging, pi-pi interaction of ligand benzene rings and hydrogen-bond interaction. The conductive potential (-0.52 eV) of the neodymium complex is more negative than that of E (H < + > / H2), the hydrogen production rate of the neodymium complex used for photocatalytic water decomposition is 18.58 [mu] mol.g <-1 >. H <-1 >, the selectivity of catalyzing benzylamine oxidation to generate N-benzyl-1-phenylmethyleneimine under the air condition is 100%, and the yield is 26.9%.

Description

Technical Field

[0001] This invention relates to the field of chemistry, specifically to a neodymium complex [NdL(H2O)2]·3H2O and its preparation method. Background Technology

[0002] Photocatalysis technology can convert solar energy into chemical energy, with applications in various fields such as water splitting, carbon dioxide reduction, organic small molecule conversion, and pollutant degradation. However, the efficiency of existing inorganic semiconductor photocatalysts is insufficient for industrial applications, and adding co-catalysts introduces new problems. Therefore, the development of novel photocatalysts that do not require co-catalysts has become an urgent need in the industry. Metal-organic frameworks (MOFs) are porous crystalline materials composed of interconnected metal ions / clusters and multidentate organic ligands. They can absorb light and generate charge-separated states by directly exciting metal clusters or organic ligands. This characteristic is similar to that of semiconductor photocatalysts, making them suitable for photocatalytic reactions. Moreover, MOF catalysis has advantages over traditional catalysis, such as high porosity, adjustable light absorption range, shortened charge transfer paths, and improved electron-hole separation. Currently, the photocatalytic performance of MOFs is mainly applied in photocatalytic hydrogen production, photocatalytic CO2 reduction, and photocatalytic degradation of dyes and heavy metal ions. In addition, crystalline MOFs have well-defined composition and structure, which are easy to adjust. Therefore, MOF materials are also an ideal model for exploring the composition-structure-performance relationship in photocatalytic systems, and can provide guidance for the rational design and development of photocatalytic materials at the molecular level.

[0003] Organic ligands and metal active centers influence the structure and properties of MOF materials. Organic ligands contain various coordinating groups, among which carboxyl ligands, possessing multiple coordination nodes, are often selected as multifunctional organic ligands. These nodes promote diverse coordination modes between ligands and metal ions, facilitating the construction of rich structural topologies in MOFs. Rare earth metal ions can endow materials with higher coordination numbers and richer coordination geometries. High coordination numbers result in structural stability and unique optical, magnetic, and electrical properties, providing broad prospects for their application in photocatalysis and electrocatalysis. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a neodymium complex [NdL(H2O)2]·3H2O and its preparation method.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A neodymium complex, the chemical formula of which is [NdL(H2O)2]·3H2O, wherein HL = 1,3,5-tris(carboxymethoxy)benzene, the crystallographic parameters of which are shown in Table 1, and some bond lengths and bond angles of which are shown in Table 2.

[0006] The neodymium complex, wherein the asymmetric structural unit of the neodymium complex is composed of an Nd... 3+ The molecule consists of a fully protonated carboxylic acid ligand, two structurally linked water molecules, and three free water molecules. The central metal ion in the molecule is Nd. 3+ It forms a double-capped tetragonal antiprism configuration by decoordinating with eight carboxylic acid oxygen atoms on five ligands and oxygen atoms on two water molecules. The chains are orderly stacked into a three-dimensional structure through ligand oxygen bridging and π-π interactions and hydrogen bonding of the ligand benzene ring.

[0007] The method for synthesizing the neodymium complex [NdL(H2O)2]·3H2O includes the following steps: (1) The reaction system includes: a) A 55-65% (v / v) aqueous solution of acetonitrile; b) Neodymium acetate, in an amount of 0.048–0.052 mmol per 5 mL of the acetonitrile aqueous solution; c) 1,3,5-tris(carboxymethoxy)benzene, wherein the molar ratio of its amount to the neodymium acetate is 1:0.9~1.1.

[0008] (2) The reaction system is stirred evenly in a container, and then concentrated nitric acid is added dropwise to the container. The amount of concentrated nitric acid used is 0.04~0.06 mL of concentrated nitric acid per 5 mL of the acetonitrile aqueous solution. The mixture is stirred evenly. (3) Transfer the reaction system to a reaction vessel and react in an oven at 135~145 °C. After the reaction is completed, remove the system, cool it, filter it, and wash it to obtain the neodymium complex [NdL(H2O)2]·3H2O.

[0009] The method for synthesizing the neodymium complex [NdL(H2O)2]·3H2O includes the following steps: (1) Weigh 0.05 mmol of 1,3,5-tris(carboxymethoxy)benzene and 0.05 mmol of neodymium acetate and place them in a 25 mL beaker; (2) Measure 3 mL of acetonitrile and 2 mL of distilled water with a graduated cylinder, pour them into a 25 mL beaker, stir with a glass rod, then add a stir bar and stir with a magnetic stirrer at room temperature for about half an hour. (3) Add one drop of concentrated nitric acid to a 25 mL beaker, then place it in an ultrasonic instrument and vibrate for ten minutes. (4) Remove the stir bar, pour the reaction system into the reactor liner, cover it and put in the iron sleeve, react in an oven at 140℃ for 72 h, remove it and cool it to room temperature, filter it and wash it to obtain the neodymium complex [NdL(H2O)2]·3H2O.

[0010] Concentrated nitric acid is used as an acid regulator to adjust reaction conditions and control crystal growth.

[0011] L = trivalent anion of 1,3,5-tris(carboxymethoxy)benzene.

[0012] Compared with the prior art, the present invention has the following beneficial effects: A novel 3D-MOF rare-earth material, a neodymium complex [NdL(H2O)2]·3H2O, was constructed using 1,3,5-tris(carboxymethoxy)benzene as a directional ligand. Its single-crystal structure was analyzed to clarify the material's structure and composition. Hirshfeld surface and 2D fingerprint maps were plotted to reveal the types and proportions of intermolecular interactions and intramolecular forces within the complex. The photoelectrochemical properties of the material were measured to investigate its light absorption performance and the separation efficiency of photogenerated electrons and holes. Furthermore, the photocatalytic oxidation of benzylamine and hydrogen production from water splitting were determined, exploring the composition-structure-performance relationship of the synthesized rare-earth photocatalyst. Attached Figure Description

[0013] Figure 1 This is a synthesis scheme for the dysprosium complex and the neodymium complex.

[0014] Figure 2 This is a crystal structure diagram of the dysprosium complex.

[0015] Figure 3 The diagram shows the coordination polyhedron of the central ion in the dysprosium complex.

[0016] Figure 4 This is a three-dimensional packing diagram of the dysprosium complex.

[0017] Figure 5 This is a crystal structure diagram of the neodymium complex.

[0018] Figure 6 The diagram shows the coordination polyhedron of the central ion in the neodymium complex.

[0019] Figure 7 This is a three-dimensional packing diagram of the neodymium complex.

[0020] Figure 8 The infrared spectra of the 1,3,5-tris(carboxymethoxy)benzene ligand, the dysprosium complex, and the neodymium complex are shown.

[0021] Figure 9 This is a surface force diagram of the dysprosium complex.

[0022] Figure 10 This is a two-dimensional fingerprint region diagram of the surface interaction of the dysprosium complex.

[0023] Figure 11 This is a surface force diagram of the neodymium complex.

[0024] Figure 12 This is a two-dimensional fingerprint region diagram of the surface interaction of the neodymium complex.

[0025] Figure 13 The image shows the UV-Vis spectra of the dysprosium complex and the neodymium complex. The horizontal axis represents wavelength, and the vertical axis represents absorbance.

[0026] Figure 14 This is a band gap diagram of the dysprosium complex. The horizontal axis represents photon energy, the vertical axis α represents the absorption coefficient of the material, hν is the photon energy, n is the exponent, and n=2 represents the direct band gap.

[0027] Figure 15 This is a band gap diagram of the neodymium complex. The horizontal and vertical axes are... Figure 14 same.

[0028] Figure 16 This is a Mott-Schottky curve of the dysprosium complex. The horizontal axis represents the potential (relative to SCE), and the vertical axis represents C. - ² represents the reciprocal square of the space charge layer capacitance, with units of F. - 2 cm 4 .

[0029] Figure 17 This is a Mott-Schottky curve plot of the neodymium complex. The horizontal and vertical axes are... Figure 16 same.

[0030] Figure 18 This is a schematic diagram of the optical band gap of the dysprosium complex and the neodymium complex. The vertical axis represents the potential (relative to RHE).

[0031] Figure 19 The graph shows the instantaneous photocurrent response of the dysprosium complex. The horizontal axis represents time, and the vertical axis represents current density.

[0032] Figure 20 The graph shows the instantaneous photocurrent response of the neodymium complex. The horizontal axis represents time, and the vertical axis represents current density.

[0033] Figure 21 The graphs show the electrochemical impedance spectroscopy (EIS) spectra of the dysprosium and neodymium complexes. The horizontal axis represents the real impedance in ohms, reflecting the total resistance encountered by charge during transport within the electrode material and at the interface. The radius of the arc directly corresponds to the charge transfer resistance; a smaller radius indicates higher charge separation and transport efficiency. The vertical axis represents the imaginary impedance in ohms.

[0034] Figure 22 Schematic diagram of benzylamine oxidation reaction.

[0035] Figure 23 The 1H NMR spectrum of the benzylamine oxidation product. Detailed Implementation

[0036] The technical solution of the present invention will be further illustrated below through embodiments.

[0037] The experimental instruments used in the examples were: Bruker Smart CCD single-crystal diffractometer, Perkin-Elmer 240Q elemental analyzer, Spectrum 65 Fourier transform infrared spectrometer, Shimadzu UV-2700 UV-Vis spectrophotometer, Bruker Advance III 400MHz NMR spectrometer, JASCO FP-6500 solid-state fluorescence spectrophotometer, Agilent 7820A gas chromatograph, MC-XS500 xenon lamp light source system, and CHI 760E electrochemical workstation.

[0038] Experimental reagents used in the examples: All chemical reagents and chemicals used in the experiments were analytical grade reagents, including 1,3,5-tris(carboxymethoxy)benzene (Jinan Henghua Technology Co., Ltd.), dysprosium chloride hexahydrate, neodymium acetate (Shanghai Maclean Biochemical Technology Co., Ltd.), acetonitrile, nitric acid, anhydrous ethanol, DMF (Xilong Chemical Co., Ltd.), and ordinary reagent-grade concentrated nitric acid with a mass fraction of 65-68%.

[0039] Example 1: Synthesis of dysprosium and neodymium complexes 1.1 Synthesis method of the dysprosium complex [Dy(H3L)Cl3]·H2O (1) Weigh 0.05 mmol (0.0151 g) of 1,3,5-tris(carboxymethoxy)benzene (H3L) and 0.05 mmol (0.0189 g) of dysprosium chloride hexahydrate and put them into a 25 mL beaker; (2) Measure 3 mL of acetonitrile and 2 mL of distilled water with a graduated cylinder, pour them into a 25 mL beaker, stir with a glass rod, then add a stir bar and stir with a magnetic stirrer at room temperature for about half an hour. (3) Add one drop of concentrated nitric acid to a 25 mL beaker, then place it in an ultrasonic instrument and vibrate for ten minutes. (4) Remove the stir bar, pour the reaction system into the reactor liner, cover it and put in the iron sleeve, react in an oven at 130°C for 72 h, remove it and cool it to room temperature, filter it and wash it to obtain light yellow needle-like crystals, which are dysprosium complex [Dy(H3L)Cl3]·H2O.

[0040] Elemental analysis C 24 H 20 Cl3DyO 19 Theoretical values: C, 32.68; H, 2.27; Test values: C, 32.65; H, 2.29.

[0041] IR(KBr, cm -1 ): 1632, 1435, 1350, 1170, 1079, 738.

[0042] 1.2 Synthesis method of the neodymium complex [NdL(H2O)2]·3H2O (1) Weigh 0.05 mmol (0.0151 g) of 1,3,5-tris(carboxymethoxy)benzene (H3L) and 0.05 mmol (0.0189 g) of neodymium acetate and place them in a 25 mL beaker; (2) Measure 3 mL of acetonitrile and 2 mL of distilled water with a graduated cylinder, pour them into a 25 mL beaker, stir with a glass rod, then add a stir bar and stir with a magnetic stirrer at room temperature for about half an hour. (3) Add one drop of concentrated nitric acid to a 25 mL beaker, then place it in an ultrasonic instrument and vibrate for ten minutes. (4) Remove the stir bar, pour the reaction system into the reactor liner, cover it and put in the iron sleeve, react in an oven at 140℃ for 72 h, remove it and cool it to room temperature, filter it and wash it to obtain light yellow needle-like crystals, which is the complex [NdL(H2O)2]·3H2O.

[0043] Elemental analysis C 12 H 21 NdO 15 Theoretical values: C, 13.61; H, 1.99; Test values: C, 13.58; H, 2.01.

[0044] IR(KBr, cm -1 ): 1632, 1417, 1314, 1164, 1084, 736.

[0045] The synthesis schemes for the dysprosium complex and the neodymium complex are as follows: Figure 1 The dysprosium and neodymium complexes prepared in Example 1 were used in the experiments of Examples 2-7.

[0046] Example 2 Crystal Structure Analysis 2.1 Crystal Structure Determination Methods Samples of dysprosium complex [Dy(H3L)Cl3]·H2O (0.15 mm × 0.11 mm × 0.10 mm) and neodymium complex [NdL(H2O)2]·3H2O (0.15 mm × 0.13 mm × 0.12 mm) were selected. They were placed on an X-ray single-crystal diffractometer using a graphite-monochromatic Mo-Kα source (λ = 0.71073 Å). At 100 K, the data collection angle range for dysprosium complex [Dy(H3L)Cl3]·H2O was 3.326 ° < 2θ < 50.7 °; the data collection angle range for neodymium complex [NdL(H2O)2]·3H2O was 4.04 ° < 2θ < 52.736 °. Structural analysis, refinement, and drawing were performed using Olex2 software.

[0047] 2.2 Results of Crystal Structure Determination The crystallographic parameters of dysprosium and neodymium complexes are shown in Table 1. Table 2 shows some bond lengths and bond angles of neodymium complexes, and Table 3 shows some bond lengths and bond angles of dysprosium complexes.

[0048] 2.2.1 The structural analysis of dysprosium complexes is as follows: As shown in Table 1, the dysprosium complex [Dy(H3L)Cl3]·H2O belongs to the monoclinic crystal system, and its space group is [missing information]. C2 / c Its asymmetric structural unit consists of a Dy 3+ It coordinates with an undeprotonated carboxylic acid ligand to form a compound containing one free water molecule and three free chloride ions (two chloride ions occupying 0.5% of the compound).

[0049] from Figure 2 , Figure 3 It can be seen that the central metal ion Dy in the dysprosium complex molecule 3+ It forms a single-cap tetragonal antiprism configuration by nine coordinations with the nine carboxylic acid oxygen atoms on the six ligands.

[0050] from Figure 4 It can be seen that in dysprosium complexes, every two adjacent Dy 3+ All of these structures are further extended through the connection of oxygen atoms in the ligand carboxylic acid and are orderly stacked into three-dimensional structures through the π··π interaction of the ligand benzene ring. dysprosium complexes are formed via the central ion Dy 3+ The single-cap tetragonal antiprism configuration is formed by coordination with the nine carboxylic acid oxygen atoms on the six ligands. In dysprosium complexes, each pair of adjacent central metal ions is bridged by the oxygen atoms of the ligand carboxylic acid to form a three-dimensional stacked structure.

[0051] 2.2.2 The structural analysis of neodymium complexes is as follows: As shown in Table 1, the neodymium complex [NdL(H2O)2]·3H2O belongs to the triclinic crystal system, and its space group is [missing information]. P Its asymmetric structural unit consists of an Nd 3+ It consists of a fully protonated carboxylic acid ligand, two structural water molecules, and three free water molecules.

[0052] from Figure 5 and Figure 6 It can be seen that the central metal ion Nd in the neodymium complex molecule 3+ It forms a double-capped tetragonal antiprism configuration by decoordinating with eight carboxylic acid oxygen atoms on five ligands and oxygen atoms on two water molecules.

[0053] from Figure 7 It is known that the chains of neodymium complexes are orderly stacked into a three-dimensional structure through ligand oxygen bridging and π-π interactions and hydrogen bonding of the ligand benzene ring.

[0054] Table 1. Crystallographic parameters of dysprosium and neodymium complexes.

[0055] Note: [a] R 1 = Σ|| F o | – | F c || / Σ| F o |. [b] wR 2 = [Σ w (| F o 2 |– | F c 2 |) 2 / Σ w (| F o 2 |) 2 ] 1 / 2 . Table 2. Partial bond lengths and bond angles of neodymium complex [NdL(H2O)2]·3H2O

[0056] Table 3. Partial bond lengths and bond angles of dysprosium complex [Dy(H3L)Cl3]·H2O

[0057] Example 3 Infrared Spectroscopy 3.1 Infrared Spectroscopy Test Method (1) Take an appropriate amount of potassium bromide and put it into an oven to dry. Then, under an infrared lamp, take an appropriate amount of potassium bromide and grind it in an agate mortar. Add the sample according to the ratio of sample / KBr = 1 / 100 (w / w) and mix and grind them thoroughly.

[0058] (2) Take an appropriate amount of the mixture and press it into a mold to form a sample sheet with uniform thickness, no cracks, and light transmission. Use a Spectrum 65 Fourier transform infrared spectrometer to measure the sample with air as the background at 4000-400 cm⁻¹. -1 The sample was scanned within a wavelength range to measure its infrared spectrum. In this embodiment, the sample consisted of a 1,3,5-tris(carboxymethoxy)benzene ligand, a dysprosium complex, and a neodymium complex. The test results are as follows: Figure 8 As shown.

[0059] 3.2 Results and Analysis of Infrared Spectroscopy Tests from Figure 8 As can be seen, the absorption peaks with broad peak shapes of the 1,3,5-tris(carboxymethoxy)benzene ligand, the dysprosium complex, and the neodymium complex are located at 3408 cm⁻¹. -1 3425 cm -1 3430 cm -1 It is a characteristic absorption peak of the bending vibration of the OH bond in the -COOH group.

[0060] For the 1,3,5-tris(carboxymethoxy)benzene ligand, the C=O stretching vibration of the -COOH group is located at 1748 cm⁻¹. -1 The stretching vibration of the benzene ring C=C skeleton is located at 1603 cm⁻¹. -1 1472 cm -1 The stretching vibration of the CO bond is located at 1347 cm. -1 1170cm -1 1231 cm -1 The external bending vibration of the CH bond in the benzene ring is located at 676 cm⁻¹. -1 .

[0061] The stretching vibrations of the C=O bonds and the C=C skeleton of the benzene ring in the dysprosium complex were transferred to 1632 cm⁻¹. -1 1435 cm -1 , The stretching vibrations of the C=O bonds and the C=C bonds in the benzene ring skeleton of the neodymium complex were transferred to 1632 cm⁻¹. -1 1417 cm -1 .

[0062] The CO bond stretching vibration of the dysprosium complex is located at 1350 cm⁻¹.-1 1170 cm -1 1079 cm -1 , The CO bond stretching vibration of the neodymium complex is located at 1314 cm⁻¹. -1 1164 cm -1 1084 cm -1 .

[0063] The characteristic absorption peak of the Dy-O bond in the dysprosium complex appears at 738 cm⁻¹. -1 , The characteristic absorption peak of the Nd-O bond in the neodymium complex appears at 736 cm⁻¹. -1 .

[0064] This shows that in both dysprosium and neodymium complexes, rare earth metal ions coordinate with oxygen in the ligands.

[0065] Example 4: Hirshfeld Surface Analysis Using the crystal parameter CIF file of the sample as the data source, the distribution of Hirshfeld surface forces of the sample molecules was calculated using CrystalExplorer 3.1. Different intermolecular interactions were visualized on the three-dimensional molecular surface of the crystal structure, yielding Denorm, Shape index, and Curvedness maps. Furthermore, 2D fingerprinting was used to quantitatively analyze the nature and molecular type of the surface forces between molecules within the sample crystal, resulting in the surface force map and 2D fingerprint of the sample, as shown below. Figure 9-12 As shown. The samples described in this embodiment are dysprosium complexes and neodymium complexes.

[0066] from Figure 9 and Figure 11 As can be seen, the Dnorm surface has red spots, indicating that there are relatively strong surface forces between the dysprosium and neodymium complexes at these locations. The Shape index surface has bright yellow irregular patches, indicating that there are intermolecular π··π interactions between the dysprosium and neodymium complexes at these locations.

[0067] Depend on Figure 10 and Figure 12 As can be seen, the largest proportion of H···H interactions in both dysprosium and neodymium complexes is observed, with dysprosium complexes accounting for 18.0% and neodymium complexes accounting for 30.8%. The O···H / H···O interaction accounts for 12.7% in dysprosium complexes and 20.5% in neodymium complexes.

[0068] Example 5 Photoelectrochemical Performance 5.1 Photoelectrochemical Testing Methods A clean ITO glass (1 cm × 2 cm) was taped onto cardstock, leaving a 1 cm × 1 cm sample area. The synthesized sample (10 mg) was then dispersed in a centrifuge tube containing 1 mL of ethanol solution and sonicated until a uniformly dispersed suspension was formed. A pipette was used to transfer a drop of the suspension to the reserved sample area on the ITO glass, and the sample was allowed to air dry at room temperature. The ITO glass (1 cm × 2 cm) was used as the working electrode, Pt as the auxiliary electrode, Ag / AgCl as the reference electrode, and 0.1 mol / L sodium sulfate solution as the electrolyte.

[0069] The UV-Vis diffuse reflectance was corrected using barium sulfate white powder as a baseline. The Mott Schottky test frequencies were 500 Hz, 800 Hz, and 1000 Hz. The instantaneous photocurrent test was performed with the lamp turned on or off every ten seconds.

[0070] 5.2 Ultraviolet-Vis Diffuse Reflectance (UV-vis DRS) To understand the photoelectrochemical properties and subsequent photocatalytic performance of dysprosium and neodymium complexes, their ultraviolet-visible diffuse reflectance (UV-vis DRS) spectra were measured, and their light absorption capacity was evaluated by calculating the band gap values. The results are as follows: Figure 13-15 As shown.

[0071] from Figure 13 As can be seen, both dysprosium and neodymium complexes have a wide and obvious visible light absorption range (around 200-560 nm).

[0072] from Figure 14 and Figure 15 It can be seen that the band gap energy (Eg) of the dysprosium complex is 2.31 eV, and that of the neodymium complex is 2.05 eV. This indicates that both the dysprosium and neodymium complexes possess semiconductor characteristics, and the lower band gap energy (Eg) of the neodymium complex compared to the dysprosium complex demonstrates that the neodymium complex has better light absorption.

[0073] 5.3 Mott-Shotkey (1) The Mott-Schottky curve is an important tool for studying the characteristics of semiconductor electrode / solution interfaces or metal / semiconductor Schottky junctions through electrochemical impedance spectroscopy. It is mainly used to determine the carrier concentration and flat band potential of semiconductors. The results are as follows: Figure 16-17 As shown.

[0074] from Figure 16 and Figure 17 As can be seen, the slopes of the fitted lines are all positive, indicating that both dysprosium and neodymium complexes are n-type semiconductors. The estimated E0 of the dysprosium complex... fbThe value is 0.19 eV vs Ag / AgCl (0.39 eV vs NHE), estimating the E of the neodymium complex. fb The values ​​are -0.75 eV vs Ag / AgCl (-0.55 eV vs NHE). Relative to the standard hydrogen electrode potential, the conduction band gap (CB) of the dysprosium complex is 0.39 eV, and that of the neodymium complex is -0.55 eV. Therefore, using the band gap energy equation (E... VB =E CB +E g The valence band VB of the dysprosium complex was calculated to be 2.70 eV vs NHE, and the valence band VB of the neodymium complex was 1.50 eV vs NHE.

[0075] (2) An optical bandgap diagram is a graph used to determine the optical bandgap of a semiconductor or insulator material by analyzing its light absorption characteristics. The optical bandgap is the most critical parameter determining how a material interacts with light (e.g., what color of light it absorbs, and whether it emits light). An optical bandgap diagram is shown below. Figure 18 As shown.

[0076] from Figure 18 It can be seen that CB in the neodymium complex is reduced to superoxide radical (O2) than O2. • The required potential (-0.33 eV vs NHE) is more negative, making neodymium complexes potential photocatalysts for generating superoxide radical anion intermediates. Meanwhile, from Figure 20 It can be seen that the positions of the conduction band and valence band in the neodymium complex well span the reduction and oxidation potential of water. That is, the CB of the neodymium complex is more negative than the potential for hydrogen production by water splitting, and the VB of the neodymium complex is more positive than the potential for oxygen production by water oxidation. This proves that the neodymium complex has thermodynamic feasibility in the overall water splitting process.

[0077] 5.4 Instantaneous photocurrent test The height of the peaks in the photocurrent response graph represents the strength of the photocurrent response. Figure 19 and Figure 20 These are the photocurrent response test spectra obtained by periodically turning the lamps on and off on the dysprosium complex and the neodymium complex, respectively.

[0078] Depend on Figure 19 and Figure 20 It can be seen that when the light is turned on, both the dysprosium and neodymium complexes can produce stable peaks, i.e., generate photocurrent signals, reflecting charge transfer between the complexes and the electrodes. However, the current response difference between the dysprosium complex and the lamp being turned off is 0.35 μAcm. -2 The difference in current response between the neodymium complex and the lamp being switched on and off was 0.43 μA / cm. -2Therefore, the photocurrent response of neodymium complexes is stronger than that of dysprosium complexes, proving that neodymium complexes have higher separation efficiency of photogenerated electrons and photogenerated holes and stronger photogenerated charge transfer ability.

[0079] 5.5 Electrochemical Impedance Figure 21 This is the electrochemical impedance spectroscopy (EIS) spectrum of dysprosium and neodymium complexes; the size of the semicircles in the spectrum represents the magnitude of the impedance. From... Figure 21 It can be seen that the impedance of the neodymium complex under illumination is lower than that of the dysprosium complex, indicating that the neodymium complex has higher charge transfer and photogenerated electron-hole pair separation efficiency, and better photoelectrochemical performance. This is also related to... Figure 19 and Figure 20 Corresponding to the photocurrent response test results.

[0080] Study on photocatalytic water splitting for hydrogen production using the neodymium complex described in Example 6 6.1 Photocatalytic hydrolysis for hydrogen production Photocatalytic water splitting for hydrogen production is an effective measure to address energy shortages by efficiently converting light energy into chemical energy. Photoelectrochemical performance testing showed that the conduction band potential (CB) of the neodymium complex pair (-0.52 eV) is more negative than that of water splitting for hydrogen production, proving that thermodynamically, neodymium complex-catalyzed water splitting for hydrogen production is possible. To explore the application of neodymium complexes in photocatalysis and their effectiveness in catalyzing water splitting for hydrogen production, experiments were conducted to investigate the effects of the light source and hole sacrificial agent on the photocatalytic performance of the neodymium complex.

[0081] Accurately weigh 5.0 mg of the neodymium complex and add it to a 25 mL quartz tube. Using a pipette, accurately measure 4 mL of acetonitrile, 1 mL of water, and 1 mL of triethanolamine (TEOA) or 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzis[d]imidazole (BIH) and add them to the quartz tube. Seal the quartz tube, sonicate for 10 min to mix, and then purge the air from the system by bubbling with nitrogen for 20 minutes. Fix the quartz tube on a magnetic stirrer and stir the reaction solution at 800 rpm / min. Simultaneously, irradiate the reaction with a 500W xenon lamp (280-800 nm wavelength) or a 400-800 nm LED lamp. Catalyze the reaction at room temperature for 6 hours. After the reaction, analyze the gaseous products using an Agilent 8860 gas chromatograph. The results are shown in Table 3.

[0082] Results of photocatalytic hydrolysis for hydrogen production using the neodymium complex described in 6.2 As shown in Table 3: First, the hydrogen production rate of the photocatalytic reaction using triethanolamine (TEOA) as a sacrificial agent and LED lamps (400-800 nm) as the light source is 18.58 μmolg. -1 h -1Compared to the hydrogen production rate of 8.18 μmol / L under the same conditions using a 500W xenon lamp as the light source. . g -1. h -1 The hydrogen evolution rate was approximately twice that of the xenon lamp, likely because the strong xenon lamp light source affected the stability of the catalyst and the entire catalytic system, thus inhibiting the hydrogen production rate. Secondly, LED lamps (400-800 nm) were subsequently selected as the light source to investigate the effects of different hole sacrificial agents, BIH and TEOA, on the hydrogen evolution performance. When TEOA was used as the sacrificial agent, the rate of hydrogen production from water splitting catalyzed by the neodymium complex was 18.58 μmol / L. . g -1. h -1 The catalytic reaction with BIH as a sacrificial agent was higher than that of the previous reaction (7.21 μmol). . g -1. h -1 Experimental data show that hole sacrificial agents and light sources have a certain impact on the catalytic hydrogen production rate.

[0083] Table 6. Control experiment of photocatalytic water splitting for hydrogen production

[0084] Study on the photocatalytic CN coupling reaction of the neodymium complex described in Example 7 7.1 Photocatalytic self-coupling reaction of benzylamine Imines with C=N bonds are important intermediates in organic synthesis, widely used in the synthesis of dyes, pharmaceuticals, and agrochemicals. Compared with traditional synthetic methods, photocatalytic dehydrogenation coupling of amines offers advantages such as mildness, high efficiency, low cost, and no pollution, exhibiting high selectivity and conversion rates. Therefore, the synthesis of imine compounds using photocatalysis has attracted considerable attention in recent years. In this example, neodymium complexes were selected to test the amine oxide coupling reaction, and benzylamine was used as the reaction substrate.

[0085] Accurately weigh 5.0 mg of the neodymium complex and add it to a 25 mL quartz tube. Using a pipette, accurately measure 4 mL of acetonitrile and 10 μL of benzylamine (0.1 mmol) substrate and add them to the quartz tube. After sonicating for 10 min, fix the quartz tube on a magnetic stirrer and stir the reaction solution at 800 rpm / min. Simultaneously, irradiate the reaction with a 500 W xenon lamp (280-800 nm wavelength) or a 400-800 nm LED lamp. Catalyze the reaction at room temperature under air conditions for 9 hours. After the reaction, collect the supernatant by centrifugation. Confirm the product using NMR spectroscopy (results are shown in the figure). Figure 23 As shown in the figure, the product was detected and analyzed using an Agilent 7820A gas chromatograph to calculate the yield, and the target product was verified by nuclear magnetic resonance hydrogen spectroscopy.

[0086] 7.2 Analysis of Experimental Results of Photocatalytic Self-Coupling Reaction of Benzylamine with the Neodymium Complex Under identical conditions, using a 500 W xenon lamp (280-800 nm) as the light source, the neodymium complex catalyzed the oxidation of benzylamine to N-benzyl-1-phenylmethyleneimine with a conversion rate of 26.9% and a selectivity of 100%. Using an LED lamp (400-800 nm) as the light source, the neodymium complex catalyzed the oxidation of benzylamine to N-benzyl-1-phenylmethyleneimine with a conversion rate of 20.8% and a selectivity of 100%.

[0087] Neodymium complex catalysts activate O2 to form O2 • and 1 O2 is a key step in this reaction process; superoxide radical anions (O2) are involved. • With singlet oxygen 1 O2 is the main free radical generated in the photocatalytic autocoupling reaction of benzylamine. Neodymium complexes absorb energy under visible light to generate photogenerated electrons and holes; the photogenerated electrons reduce molecular oxygen to O2. • and 1 O2. O2 • and 1 O2 oxidizes benzylamine to give the product N-benzyl-1-phenylmethylimine, such as Figure 22 As shown.

[0088] Example 2 The method for synthesizing the neodymium complex [NdL(H2O)2]·3H2O includes the following steps: (1) The reaction system includes: a) A 65% (v / v) aqueous solution of acetonitrile; b) Neodymium acetate, in an amount of 0.052 mmol per 5 mL of the acetonitrile aqueous solution; c) 1,3,5-tris(carboxymethoxy)benzene, wherein the molar ratio of its amount to the neodymium acetate is 1:1.1.

[0089] (2) The reaction system is stirred evenly in a container, and then concentrated nitric acid is added dropwise to the container. The amount of concentrated nitric acid used is 0.06 mL of concentrated nitric acid for every 5 mL of the acetonitrile aqueous solution. The mixture is stirred evenly. (3) The reaction system was transferred to a reaction vessel and reacted in an oven at 145 °C. After the reaction was completed, the system was taken out, cooled, filtered, and washed to obtain the neodymium complex [NdL(H2O)2]·3H2O.

[0090] Example 3 The method for synthesizing the neodymium complex [NdL(H2O)2]·3H2O includes the following steps: (1) The reaction system includes: a) A 55% (v / v) aqueous solution of acetonitrile; b) Neodymium acetate, in an amount of 0.048 mmol per 5 mL of the acetonitrile aqueous solution; c) 1,3,5-tris(carboxymethoxy)benzene, wherein the molar ratio of its amount to the neodymium acetate is 1:0.9.

[0091] (2) The reaction system is stirred evenly in a container, and then concentrated nitric acid is added dropwise to the container. The amount of concentrated nitric acid used is 0.04 mL of concentrated nitric acid for every 5 mL of the acetonitrile aqueous solution. The mixture is stirred evenly. (3) The reaction system was transferred to a reaction vessel and reacted in an oven at 135 °C. After the reaction was completed, the system was taken out, cooled, filtered, and washed to obtain the neodymium complex [NdL(H2O)2]·3H2O.

[0092] Example 4 The method for synthesizing the neodymium complex [NdL(H2O)2]·3H2O includes the following steps: (1) The reaction system includes: a) 55%, 57%, 60%, 62.5%, or 65% (v / v) aqueous acetonitrile solution; b) Neodymium acetate, in amounts of 0.048, 0.049, 0.050, 0.051, or 0.052 mmol per 5 mL of the acetonitrile aqueous solution; c) 1,3,5-tris(carboxymethoxy)benzene, wherein the molar ratio of its amount to the neodymium acetate is 1:0.9, 1.0 or 1.1.

[0093] (2) The reaction system is stirred evenly in a container, and then concentrated nitric acid is added dropwise to the container. The amount of concentrated nitric acid used is 0.04, 0.05, or 0.06 mL of concentrated nitric acid per 5 mL of the acetonitrile aqueous solution. The mixture is stirred evenly. (3) Transfer the reaction system to a reaction vessel and react in an oven at 125, 128, 130, 132 or 135 °C. After the reaction is completed, remove the system, cool it, filter it and wash it to obtain the neodymium complex [NdL(H2O)2]·3H2O.

Claims

1. A neodymium complex, characterized in that, The neodymium complex has the chemical formula [NdL(H2O)2]·3H2O, HL = 1,3,5-tris(carboxymethoxy)benzene. The crystallographic parameters of the neodymium complex are shown in Table 1, and some bond lengths and bond angles are shown in Table 2. Table 1 shows the crystallographic parameters of the neodymium complexes. Table 2 shows some bond lengths and bond angles of the neodymium complexes. 。 2. The neodymium complex as described in claim 1, characterized in that, The asymmetric structural unit of the neodymium complex is composed of an Nd... 3+ The molecule consists of a fully protonated carboxylic acid ligand, two structurally linked water molecules, and three free water molecules. The central metal ion in the molecule is Nd. 3+ It forms a double-capped tetragonal antiprism configuration by decoordinating with eight carboxylic acid oxygen atoms on five ligands and oxygen atoms on two water molecules. The chains are orderly stacked into a three-dimensional structure through ligand oxygen bridging and π-π interactions and hydrogen bonding of the ligand benzene ring.

3. The method for synthesizing the neodymium complex [NdL(H2O)2]·3H2O as described in claim 1, characterized in that, Includes the following steps: (1) The reaction system includes: a) A 55-65% (v / v) aqueous solution of acetonitrile; b) Neodymium acetate, in an amount of 0.048–0.052 mmol per 5 mL of the acetonitrile aqueous solution; c) 1,3,5-tris(carboxymethoxy)benzene, wherein the molar ratio of its amount to the neodymium acetate is 1:0.9~1.

1.

4. (2) The reaction system is stirred evenly in a container, and then concentrated nitric acid is added dropwise to the container. The amount of concentrated nitric acid used is 0.04~0.06 mL of concentrated nitric acid per 5 mL of the acetonitrile aqueous solution. The mixture is stirred evenly. (3) Transfer the reaction system to a reaction vessel and react in an oven at 135~145 °C. After the reaction is completed, remove the system, cool it, filter it, and wash it to obtain the neodymium complex [NdL(H2O)2]·3H2O.

5. The method for synthesizing the neodymium complex [NdL(H2O)2]·3H2O as described in claim 3, characterized in that, Includes the following steps: (1) Weigh 0.05 mmol of 1,3,5-tris(carboxymethoxy)benzene and 0.05 mmol of neodymium acetate and place them in a 25 mL beaker; (2) Measure 3 mL of acetonitrile and 2 mL of distilled water with a graduated cylinder, pour them into a 25 mL beaker, stir with a glass rod, then add a stir bar and stir with a magnetic stirrer at room temperature for about half an hour. (3) Add one drop of concentrated nitric acid to a 25 mL beaker, then place it in an ultrasonic instrument and vibrate for ten minutes. (4) Remove the stir bar, pour the reaction system into the reactor liner, cover it and put in the iron sleeve, react in an oven at 140℃ for 72 h, remove it and cool it to room temperature, filter it and wash it to obtain the neodymium complex [NdL(H2O)2]·3H2O.

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