A palladium nanocatalyst, a preparation method thereof and application thereof in solar-driven spontaneous synthesis of solid aromatic amines from solid reactants
By preparing palladium nanocatalysts and utilizing solar energy to drive photothermal effects, the problem of difficult-to-control selectivity and activity in the synthesis of solid aromatic amines was solved, realizing efficient and spontaneous synthesis of solid aromatic amines with high yield and selectivity.
Patent Information
- Application Number
- CN202510102571.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-22
- Publication Date
- 2026-02-06
- Estimated Expiration
- 2045-01-22
AI Technical Summary
Existing technologies cannot achieve the selective synthesis of solid aromatic amines under solid conditions without external force, and conventional catalysts have the problem of difficulty in simultaneously controlling activity and selectivity when catalyzing solid reactions.
Palladium nanocatalysts were prepared by reacting 4-dodecylaniline diazonium salt and palladium acetate with sodium borohydride. The solid nitro compound was statically irradiated under solar energy, and spontaneous solid-state synthesis was achieved by utilizing the asymmetry and photothermal effect of palladium nanomaterials.
The efficient and spontaneous synthesis of solid aromatic amines at room temperature was achieved with a yield of up to 98% and a selectivity of over 99%. The catalyst also exhibited broad substrate applicability and stability, enabling gram-scale reactions up to 15g to be completed in a short time.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of organic synthesis, and particularly relates to a palladium nanocatalyst, a preparation method thereof and application of the palladium nanocatalyst in spontaneous synthesis of solid aromatic amines from solar-driven solid reactants. BACKGROUND
[0002] Fresh grapes can produce wine through fermentation, but raisins cannot. Milk is prone to spoilage, but powdered milk can remain unchanged. Similarly, dried meat can be stored for a long time, while meat broth will quickly rot when placed. By observing these phenomena, it can be seen that the transformation of one material into another occurs in a liquid state, not in a solid state. One of the most famous ancient Greek philosophers, Aristotle, summarized these observations and concluded that "No Coopora nisi Fluida", meaning "no reaction without solvent". These philosophies have had a major impact on the development of modern science in Europe, which provides a historical reason why most organic reactions are carried out in solution (Springer, Berlin Heidelberg, 2004, 115-245; Chem. Rev. 2000, 100, 1025-1074). The current pharmaceutical industry and fine chemical industry are strongly dependent on solvent-based organic synthesis, which leads to a serious problem of solvent waste, because organic solvents usually account for 80-90% of the total mass used in any organic reaction (Science 2002, 297, 799-803.). Although solvent recovery is a very effective method to reduce solvent waste, organic chemists should focus on (re)designing organic synthesis to reduce or not use solvents. In this context, solid-state organic transformation has attracted considerable attention as a cleaner, more sustainable alternative to synthesis (Nature 1997, 387, 583-586; J. Am. Chem. Soc. 2023, 145(12), 6823-6837; Chem. Sci. 2024, 15, 14798-14805).
[0003] In solid-state synthesis, the reactant molecules are in a confined state, and the molecular conformation is relatively stable, which greatly limits its ability to participate in reactions in the solid state. According to the theory of topological chemistry, solid-state synthesis reactions can usually be implemented in four stages: first, single or several nuclear crystal points produce crystal defects, deformation, and molecular loosening phenomena. Second, the old chemical bonds are broken in the given environment and new bonds are formed. Third, a small number of products quickly form solid / solution in the original crystal. Fourth, the product is crystallized and separated; the rate-limiting step in solid-state reactions is the diffusion of atoms or ions through the crystalline phases of reactants, intermediates, and products. This process is slow, requiring several days or even weeks of time and high-temperature treatment, and consumes a large amount of energy (Chem. Soc. Rev. 2011, 40, 2317-2329). Solid-state grinding, ultrasonic irradiation, mechanical shaking or stirring, spark plasma sintering, and high-temperature melting are effective means to accelerate this process (J. Am. Chem. Soc. 2023, 145(28), 15118-15127; Angew. Chem. Int. Ed. 2022, 61, e202212694). Among them, solid-state grinding accounts for half of the current solid-state synthesis field and has been widely used in drug co-crystal synthesis, material development, and electroplating. Mechanical grinding can increase the free energy of the solid surface, and the combined shear force, friction force, and elastic tension generated by extrusion produce instantaneous micro-heat, thereby activating the reaction system and accelerating the reaction. However, the use of external force is inevitable, which is commonly referred to as mechanical chemistry. However, under the background of energy crisis, green chemistry, and sustainable development, the field of solid-state organic synthesis faces new opportunities and challenges: 1. Under mild conditions, spontaneous solid-state organic synthesis is difficult to achieve; 2. Most solid-state synthesis strategies are only suitable for individual special cases, and their activity and selectivity often cannot be universally controlled; 3. Conventional catalysts often exhibit high activity on the contact surface when catalyzing solid-state reactions, and the uncontacted parts are usually difficult to occur or take a long time to react, making it difficult to simultaneously achieve spatial integration of conversion rate and selectivity control.
[0004] Solar-driven photothermal synergistic catalysis could be an interesting approach for spontaneous, efficient, and selective solid-state synthesis under mild conditions (Chinese J. Catal. 2024, 60, 128-157; Science 2011, 333, 712-717). The use of solar photothermal effect to drive organic synthesis is expected to replace traditional thermal catalytic technology, thus realizing low-energy consumption chemical production. In fact, photothermal effect has been widely studied in the fields of energy utilization, biomedicine, catalytic conversion, and intelligent devices, and has achieved applications in photothermal solar evaporation, photothermal therapy, photothermal catalysis, agricultural heaters, photothermal energy storage, photothermal induction self-healing materials, photothermal driven robots, and photothermal functional materials (Chem. Rev. 2022, 473, 214794). Given the current energy crisis, energy consumption is one of the important factors restricting the development of modern chemical industry. The use of solar energy to drive organic synthesis and convert solar energy into chemical energy provides a new way to alleviate the current energy dilemma. Metal nanostructures have unique plasmonic optical properties, providing opportunities for this technology approach (Chem. Rev. 2018, 118, 3054-3099). However, in order to fully utilize solar energy in solid-state synthesis and chemical production, two key scientific and technical problems need to be addressed: how to capture solar energy in a broad spectrum and how to effectively introduce captured solar photon energy into solid-state chemical reactions. Palladium is a highly efficient catalyst for many organic reactions, but the localized surface plasmon properties of palladium nanostructures are always inferior to those of gold and silver, with small light absorption cross-section and limited response spectrum range in the ultraviolet band, which brings great difficulties to solar energy capture and utilization. How to regulate and optimize these two processes for the needs of organic synthesis is the key to solving the problems in this field. Among them, loading photosensitive metals or semiconductor materials is an effective way to make them absorb visible light in a wide spectrum. The photothermal effect after light absorption can produce local high temperature to provide heat for organic reactions, realizing the combination of solar energy utilization and spatial distribution of catalytic activity. Reducing structural symmetry is another effective way to enhance visible light absorption (ACS Catal. 2018, 8(10), 9280-9286). It is worth noting that these two strategies are not a problem in liquid-state organic reactions, but due to the reduced penetration of light in solid-state reactions and the confinement of solid-state molecules, solar photothermal catalysis is difficult to occur under solid-state conditions, especially under spontaneous conditions without external force. In fact, current solar photothermal catalytic technology is limited to liquid-phase reactions, sometimes with stirring. In contrast, the great application potential of solid-state photothermal catalytic reactions in the fields of energy and environment should be considered as a powerful weapon for green chemistry, but it is more challenging. Therefore, developing visible light photothermal catalytic materials is the ultimate goal of studying solar-driven spontaneous solid-state synthesis. SUMMARY
[0005] The present application aims to solve the technical problem that the prior art cannot realize the selective synthesis of solid aromatic amines under the condition of solid state without external force, and provides a palladium nanocatalyst, a preparation method thereof and application thereof in the spontaneous synthesis of solid aromatic amines from solar-driven solid reactants.
[0006] To solve the above technical problems, the technical solution adopted by the present application is:
[0007] A preparation method of a palladium nanocatalyst comprises the following steps:
[0008] 4-dodecyl aniline diazonium salt is prepared from 4-dodecyl aniline, tetrafluoroboric acid and sodium nitrite;
[0009] The palladium nanocluster catalyst is prepared from palladium acetate, 4-dodecyl aniline diazonium salt and sodium borohydride.
[0010] As a further optimization of the preparation method of the palladium nanocatalyst, the preparation method specifically comprises the following steps:
[0011] S1: 4-dodecyl aniline and tetrafluoroboric acid are mixed and slowly added to an aqueous sodium nitrite solution at 0-5℃, and after stirring, 4-dodecyl aniline diazonium salt is obtained by filtration and washing, and is dried and stored at 0-5℃;
[0012] S2: The palladium acetate methanol solution and the tetrahydrofuran solution of 4-dodecyl aniline diazonium salt are mixed and slowly added to the sodium borohydride methanol solution at 0-5℃, and are stirred vigorously at 0-5℃, and after the reaction is completed, the methanol and tetrahydrofuran are removed and dissolved in dichloromethane, and after washing with H2SO4, an aqueous NaHCO3 solution and deionized H2O, the product is dried with anhydrous sodium sulfate, and finally, the product is filtered and the solvent is removed.
[0013] As a further optimization of the preparation method of the palladium nanocatalyst, the preparation method further comprises the step S3: the product after filtration and removal of the solvent is dispersed in anhydrous ethanol, the supernatant is discarded after centrifugal treatment, and the obtained solid is dried to obtain the palladium nanomaterial catalyst.
[0014] The molar ratio of the addition amount of 4-dodecyl aniline diazonium salt, sodium nitrite and tetrafluoroboric acid in step S1 is 1:4.5:21.
[0015] The molar ratio of the addition amount of palladium acetate, 4-dodecyl aniline diazonium salt and sodium borohydride in step S2 is 1:1:5.
[0016] The present application also provides a palladium nanocatalyst prepared by the above method.
[0017] The application further provides application of the above-mentioned palladium nanocatalyst in spontaneous synthesis of solid aromatic amine from solid-state reactants driven by solar energy.
[0018] As a further optimization of the application of the palladium nanocatalyst in spontaneous synthesis of solid aromatic amine from solid-state reactants driven by solar energy, the solid-state nitro compound is subjected to static solar irradiation at room temperature and in a H2 atmosphere, with the above-mentioned palladium nanomaterial as a catalyst, to synthesize a solid aromatic amine compound.
[0019] As a further optimization of the application of the palladium nanocatalyst in spontaneous synthesis of solid aromatic amine from solid-state reactants driven by solar energy, the molar ratio of the solid-state nitro compound to the palladium nanomaterial is 1:0.0001-0.1, preferably, the molar ratio of the solid-state nitro compound to the palladium nanomaterial is 1:0.01.
[0020] As a further optimization of the application of the palladium nanocatalyst in spontaneous synthesis of solid aromatic amine from solid-state reactants driven by solar energy, the reaction is detected by HPLC until it is complete, and then the solid aromatic amine compound is obtained by purification through either recrystallization or column chromatography.
[0021] The application has the following beneficial effects: the application utilizes spontaneous solid-state reaction driven by solar energy to produce aniline, and the reaction can be smoothly and spontaneously carried out without introducing mechanical chemistry, and only needs to be subjected to static irradiation with sunlight for a short time at ambient temperature (25℃). BRIEF DESCRIPTION OF DRAWINGS
[0022] Figure 1 It is a graph of solid-state catalytic performance under different light intensities;
[0023] Figure 2 It is a schematic diagram of monitoring the reaction process by an optical microscope;
[0024] Figure 3 It is a TOF value of 12R Pd-NCs, Pd(OAc)2 and Pd / C catalysts;
[0025] Figure 4 It is a graph of 12R-Pd-NCs solid-state catalytic cycle experiment;
[0026] Figure 5 It is a transmission electron microscope graph of 12R-Pd-NCs;
[0027] Figure 6 It is an infrared thermal imaging graph of a template substrate undergoing solid-state reaction;
[0028] Figure 7 It is a nuclear magnetic resonance spectrum of target product II-01; 1 H NMR spectrum;
[0029] Figure 8 NMR of target product II-01 13 C NMR spectrum;
[0030] Figure 9 Schematic diagram of mechanism of solar-driven spontaneous synthesis of solid aromatic amine from solid reactants. DETAILED DESCRIPTION
[0031] In order to better understand the present application, the content of the present application is further illustrated below in combination with examples, but the content of the present application is not limited to the following examples.
[0032] Palladium nanocatalyst 12R-Pd-NCs
[0033] The preparation method of the palladium nanocatalyst 12R-Pd-NCs is as follows:
[0034] 4-Dodecylaniline (261.45 mg, 1.0 mmol) and 50% tetrafluoroboric acid (5 mL) were added to a 25 mL flask at 0°C, and a previously configured aqueous sodium nitrite solution (0.3 g, 4.5 mmol, 1.0 mL H2O) was slowly added to the stirring 4-dodecylaniline and HBF4 solution, the solution was stirred for 30 minutes, then a yellow solid was obtained, which was filtered with a Buchner funnel and washed with H2O (2 x 2.5 mL). The 4-dodecylaniline diazonium salt was dried in a vacuum desiccator and stored at 0°C.
[0035] The palladium acetate methanol solution (112.3 mg, 0.5 mmol) and the tetrahydrofuran solution of dodecylaniline diazonium salt (173 mg, 0.5 mmol) were mixed and stirred at 0°C for 30 minutes. Then a sodium borohydride methanol solution (2.5 mmol of sodium borohydride dissolved in 2.0 mL of methanol) was slowly added, and stirred vigorously (300-500 r / min) at 0°C for 2 hours. After the reaction was completed, the methanol and tetrahydrofuran were removed with a rotary evaporator, dissolved in dichloromethane, washed with 0.5M H2SO4 (3 x 20 mL), 0.5M NaHCO3 (3 x 20 mL) and H2O (3 x 20 mL), dried with anhydrous sodium sulfate, and rotary evaporated. The 12R-Pd-NCs were dispersed in anhydrous ethanol, and obvious layering was observed after centrifugal treatment, the supernatant solvent was discarded, the solid was dried, and 12R-Pd-NCs were obtained. As shown in FIG. 1, it is a high-resolution transmission electron micrograph of the prepared palladium nanoclusters. Figure 5
[0036] Sometimes, interesting discoveries come from a powerful and unbound style. In fact, as McQueen said, “... most material discoveries in the field of solid-state chemistry have been made by accident, not by carefully designed reactions... ” (Acc. Chem. Res. 2018, 51, 2918-2925). Applicants “accidentally” designed a simple class of nanoscale palladium, with 3 nm palladium clusters as the main body, solar energy as the driving force, and solid-state reactants as the prey. The extremely asymmetricity exhibited by the defect structure of the cluster can greatly enhance the absorption of visible light and provide a constant source of power. At this time, the flexible alkyl chain will exhibit perfect capture and driving characteristics. This pre-designed catalyst can spontaneously, efficiently and selectively synthesize solid aromatic amines at room temperature, and only needs a constant source of solar energy. It is worth mentioning that the catalyst has wide substrate applicability, can realize gram-scale reactions to 15 g, and maintains 98% yield and >99% chemical selectivity, with only a small amount of catalyst. This is a new discovery in the field of solid-state photocatalysis. The development of this strategy will provide opportunities and unlimited possibilities for the scale-up application of solar energy-driven solid-state green synthesis.
[0037] <Spontaneous synthesis of solid aromatic amines from solar-driven solid-state reactants>
[0038] Under the condition of 12R-Pd-NCs and H2 (0.1 MPa), the solid-state nitro compound is subjected to static irradiation under sunlight for 4 hours, and HPLC detection shows that the reaction is complete. Solid aromatic amine compounds are obtained by recrystallization or column chromatography purification, and the reaction formula is as follows:
[0039]
[0040] Among them, R represents methoxy, methyl or phenyl substitution; X represents C atom or N atom.
[0041] The present application first introduces solar energy into spontaneous solid-state organic reactions. Under static sunlight irradiation, solid nitro reactants can be converted in a short time with nearly perfect conversion rate and chemical selectivity to generate solid aromatic amines. In addition, this method has wide substrate universality, and gram-scale reactions can reach 15 g. The TOF value is as high as 139169 h -1 ( Figure 3 ) which is one order of magnitude higher than the best value of nitrobenzene hydrogenation reported before. It is found that the “temperature gradient driven” effect is higher than the “local motion inhibition” threshold, which is a necessary condition for effective response ( Figure 1 ). In addition, the physical form of the reaction mixture changes sharply from a highly aggregated crystal structure to a foamy appearance during the reaction ( Figure 2 ). 1 H-NMR and 13C-NMR spectra were used to elucidate the structure of the product Figure 7 and Figure 8 Infrared thermal imaging data are shown in Figure 6 Figure 4 Cycling experiments for 12R-Pd-NCs.
[0042] Applicants found that the rate-limiting step in solid-state reactions involves the diffusion of atoms, molecules, or ions through the crystalline phases of reactants, intermediates, and products. This process is slow, often requiring days or even weeks of continuous or intermittent shaking, while consuming a large amount of energy. Microwaves, ball milling, grinding, ultrasonic treatment, spark plasma sintering, and high-temperature melting are effective methods to accelerate this process. However, achieving spontaneous solid-state synthesis without external force faces significant challenges. The present invention proposes a solar-driven spontaneous solid-state reaction to produce aromatic amines. The reaction can proceed smoothly and spontaneously without the introduction of mechanical chemistry, only by adding a trace amount of a newly designed nanocluster, and static irradiation under sunlight for a short time at ambient temperature. The "temperature gradient-driven" effect above the "local motion inhibition" threshold is a necessary condition for effective response. The yield and chemical structure of the reaction product can be obtained by combining high-performance liquid chromatography and nuclear magnetic resonance 1 HNMR, 13 CNMR. In addition, 12R-Pd-NCs can be recycled at least 5 times without significant loss of activity Figure 4 Catalytic cycling experiments demonstrate that the stability of this catalyst far exceeds that of homogeneous palladium complexes.
[0043] <Example 1>
[0044] Into a 10 mL reaction bottle, 0.5 mmol of compound I-01, 2 mg of 12R-Pd-NCs nanoparticles prepared above, and then 0.1 MPa H2 were added. Static irradiation of the raw materials was carried out at room temperature using sunlight (the light intensity of sunlight is equivalent to that of a 150 W xenon lamp). HPLC was used to detect the reaction progress, and the reaction yield was >99% after 4 hours. The target compound II-01 was obtained by recrystallization or column chromatography purification, and was a yellow solid.
[0045] Among them, the structural formula of compound I-01 and hydrogen is as follows:
[0046]
[0047] The structural formula of compound II-01 is as follows:
[0048]
[0049] The obtained product was analyzed, and the analysis data were as follows: A yellow solid, >99% yield. 1 H NMR (500 MHz, CDCl3) δ 6.76 (d, J = 10.0 Hz, 2H), 6.65 (d, J = 10.0 Hz, 2H), 3.75 (s, 3H), 3.44 (s, 2H). 13 C NMR (126 MHz, CDCl3) δ 153.04, 140.29, 116.70, 115.08, 56.02.
[0050] <Example 2>
[0051] Into a 10 mL reaction bottle, 0.5 mmol of compound I-02, 2 mg of 12R-Pd-NCs nanoparticles prepared above were added, then 0.1 MPa H2was introduced, and the raw material was statically irradiated with sunlight at room temperature (the light intensity of sunlight was equivalent to that of a 200 W xenon lamp). The reaction process was detected by HPLC, and the yield was 99% after 4 hours. The target compound II-02 was obtained by recrystallization or column chromatography purification, and was a yellow solid.
[0052] Among them, the structural formulas of compound I-02 and H2are as follows:
[0053]
[0054] The structural formula of compound II-02 is as follows:
[0055]
[0056] The obtained product was analyzed, and the analysis data were as follows: A yellow solid, >99% yield. 1 HNMR (500 MHz, DMSO) δ 7.28-7.14 (m, 2H), 6.98-6.88 (m, 2H), 5.21 (s, 2H), 2.48 (s, 3H). 13 C NMR (126 MHz, DMSO) δ 135.76, 120.67, 118.92, 107.19, 10.78.
[0057] <Example 3>
[0058] Into a 10 mL reaction vial, 0.5 mmol of compound I-03, 2 mg of 12R-Pd-NCs nanoparticles prepared above were added, followed by 0.1 MPa H2. The reaction was carried out under static irradiation of sunlight (the intensity of sunlight was equivalent to that of a 350 W xenon lamp) at room temperature. The progress of the reaction was monitored by HPLC. After 4 hours, the yield of the reaction was 99%. The target compound II-03 was obtained by recrystallization or column chromatography purification, yellow solid.
[0059] wherein the structures of compound I-03 and hydrogen are as follows:
[0060]
[0061] The structure of compound II-03 is as follows:
[0062]
[0063] The obtained product was analyzed, and the analysis data were as follows: White solid, 79% yield, 1 H NMR (500 MHz, CDCl3) δ 7.60 (d, J = 5.0 Hz, 2H), 7.51-7.42 (m, 4H), 7.32 (t, J = 5.0 Hz, 1H), 6.80-6.77 (m, 2H), 3.74 (s, 2H). 13 C NMR (126 MHz, CDCl3) δ 146.19, 141.47, 131.83, 129.01, 128.33, 126.73, 126.60, 115.72.
[0064] <Example 4>
[0065] Into a 10 mL reaction vial, 0.5 mmol of compound I-03, 2 mg of 12R-Pd-NCs nanoparticles prepared above were added, followed by 0.1 MPa H2. The reaction was carried out under static irradiation of sunlight (the intensity of sunlight was equivalent to that of a 350 W xenon lamp) at room temperature. The progress of the reaction was monitored by HPLC. After 4 hours, the yield of the reaction was 99%. The target compound II-03 was obtained by recrystallization or column chromatography purification, yellow solid.
[0066] wherein the structures of compound I-03 and hydrogen are as follows:
[0067]
[0068] The structure of compound II-03 is as follows:
[0069]
[0070] The product obtained was analyzed, and the analysis data were as follows: a yellow solid, 91% yield, 1 H NMR (500 MHz, CDCI3) δ 8.04 (d, J = 5.0 Hz, 1 H), 7.95 (d, J = 5.0 Hz, 1 H), 7.03-7.00 (m, 1 H), 6.95-6.88 (m, 1 H), 3.73 (s, 2 H). 13 C NMR (126 MHz, CDCI3) δ 143.01, 140.01, 137.64, 124.03, 121.72.
[0071] <Comparative Example 1-3>
[0072] The synthesis process of <Comparative Example 1-3> was basically the same as that of <Example 1>, except that the designed 12R Pd-NCs catalyst was replaced by Pd / C, Pd(OAc)2, and a dodecylpalladium precursor mixture, respectively. The reaction results were as follows:
[0073] After the reaction of <Comparative Example 1> was completed, the final yield was calculated to be 55%.
[0074] After the reaction of <Comparative Example 2> was completed, the final yield was calculated to be 28%.
[0075] After the reaction of <Comparative Example 3> was completed, the final yield was calculated to be 70%
[0076] <Comparative Example 4-7>
[0077] The synthesis process of <Comparative Example 4-7> was basically the same as that of <Example 1>, except that the reaction environment was changed to a dark environment for static light-avoiding reaction.
[0078] The temperature was adjusted to 0°C, 25°C, 50°C, and 100°C.
[0079] After the reaction of <Comparative Example 4> was completed, the final yield was calculated to be 19%
[0080] After the reaction of <Comparative Example 5> was completed, the final yield was calculated to be 50%
[0081] After the reaction of <Comparative Example 6> was completed, the final yield was calculated to be 56%.
[0082] After the reaction of <Comparative Example 7> was completed, the final yield was calculated to be 39%.
[0083] <Comparative Example 8-11>
[0084] The synthesis process of <Comparative Example 8-11> is basically the same as <Example 1>, except that the sun light is simulated by a hernia lamp, and the power of the xenon lamp is 15W, 60W, 100W and 300W respectively.
[0085] After the reaction of <Comparative Example 8> is completed, the final yield is calculated to be 44%.
[0086] After the reaction of <Comparative Example 9> is completed, the final yield is calculated to be 37%.
[0087] After the reaction of <Comparative Example 10> is completed, the final yield is calculated to be >99%.
[0088] After the reaction of <Comparative Example 11> is completed, the final yield is calculated to be >99%.
[0089] From the above data, it can be seen that sunlight is essential for driving the spontaneous synthesis of solid-state aromatic amines from solid-state nitro compounds. The new type of nanoclusters designed in the present application can significantly enhance this effect through photo-thermal conversion. Although light is essential for the reaction, its role as a heat source is another important consideration. The results of the reaction at different temperatures in the dark condition show that the temperature effect is unlikely to be the controlling factor in this process. The hypothesis of "gradient-driven" phenomenon seems to be a more reasonable assumption. Due to the difference between light and heat (in the dark), the resulting temperature "gradient" is significantly different. According to thermal measurements, these gradients are greater in the case of light explosion ( Figure 6 ). This is important because it is the gradient, not uniformity, that drives the movement of molecules or particles. The presence of a gradient facilitates the preferential migration of catalysts relative to reactants / products, thereby achieving complete conversion. This is something that heat itself cannot achieve without a gradient to drive movement. Experimental data at different light intensities also indicate the importance of the gradient, which shows that there is a critical light level above which the dynamics required for high yield can be achieved, i.e. the gradient needs to exceed a "local motion suppression" threshold ( Figure 1 ). Changes in the physical form of the reaction also coincide with the higher yield caused by the motion caused by the temperature gradient, i.e. the physical form of the reaction mixture changes dramatically from a highly aggregated crystalline structure to a foam-like appearance during the reaction ( Figure 2 ).
[0090] The above describes specific embodiments of the present application. It should be understood that the present application is not limited to the above specific embodiments, and those skilled in the art can make various modifications or modifications within the scope of the claims, which does not affect the essential content of the present application.
Claims
1. A method of preparing a palladium nanocatalyst, characterized by: The method comprises the following steps: S1: mixing 4-dodecyl aniline and tetrafluoroboric acid at 0-5 DEG C and slowly adding an aqueous sodium nitrite solution, stirring, filtering and washing to obtain 4-dodecyl aniline diazonium salt, and storing after drying at 0-5 DEG C; S2: mixing a palladium acetate methanol solution and a tetrahydrofuran solution of 4-dodecyl aniline diazonium salt at 0 DEG C and slowly adding a sodium borohydride methanol solution, stirring vigorously at 0-5 DEG C, removing methanol and tetrahydrofuran after the reaction is completed, dissolving in dichloromethane, washing and drying, and then performing suction filtration and removing the solvent; In step S2, the molar ratio of the added amounts of palladium acetate, 4-dodecyl aniline diazonium salt and sodium borohydride is 1:1:
5.
2. The method for preparing palladium nanocatalyst as described in claim 1, characterized in that: The method further comprises step S3: dispersing the product after suction filtration and removal of the solvent in anhydrous ethanol, discarding the supernatant after centrifugal treatment, and drying the obtained solid to obtain the palladium nanocatalyst.
3. The method for preparing palladium nanocatalyst as described in claim 1, characterized in that: In step S1, the molar ratio of the added amounts of 4-dodecyl aniline, sodium nitrite and tetrafluoroboric acid is 1:4.5:
21.
4. A palladium nanocatalyst characterized by: The palladium nanocatalyst is prepared by the method according to any one of claims 1-3.
5. The palladium nanocatalyst according to claim 4 is used in the spontaneous synthesis of solid aromatic amines from solid-state reactants driven by solar energy.
6. Use of the palladium nanocatalyst according to claim 5 for the solar-driven spontaneous synthesis of solid aromatic amines from solid reactants, characterized in that: The solid-state nitro compound is irradiated with solar light in a static state at room temperature and in a H2 atmosphere, and a solid aromatic amine compound is synthesized in a solid state by using the palladium nanomaterial as a catalyst.
7. Use of the palladium nanocatalyst according to claim 6 for the solar-driven spontaneous synthesis of solid aromatic amines from solid reactants, characterized in that: The molar ratio of the added amounts of the solid-state nitro compound and the palladium nanomaterial is 1:0.0001-0.
1.
8. Use of the palladium nanocatalyst according to claim 6 for the solar-driven spontaneous synthesis of solid aromatic amines from solid reactants, characterized in that: The reaction is detected by HPLC until it is complete, and then the solid aromatic amine compound is purified by recrystallization or column chromatography.