Method for realizing efficient photocatalytic oxidation-reduction reaction by using porous composite material
By preparing porous composite materials, the problems of insufficient specific surface area and pore structure of the catalyst during CO2 reduction and NO oxidation were solved, efficient CO2 reduction and NO oxidation effects were achieved, and the catalyst's ability to separate photogenerated electrons and holes was improved.
Patent Information
- Application Number
- CN202510213842.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-26
- Publication Date
- 2025-09-16
AI Technical Summary
Existing catalysts have low specific surface area and lack matching pore structure during CO2 reduction and NO oxidation, resulting in poor adsorption capacity, which limits further improvement of photocatalytic CO2 reduction activity, especially in the presence of oxygen.
The porous material was prepared using SiO2 balls as templates, tetraphenylporphyrin as raw material, CHCl3 as solvent, and AlCl3 as catalyst. TiO2 nanoparticles and coordinated metal Pd were loaded through self-assembly method to form a porous composite material.
Under pure CO2 conditions, the CH4 yield of TiO2/TPP-TPP-Pd reached 52 μmol g-1h-1, and the NO oxidation conversion rate was 65%. In the presence of air and trace NO, the CO2 conversion rate was still highly efficient, with a CH4 yield of 14.3 μmol g-1h-1, significantly improving the catalyst's ability to separate photogenerated electrons and holes.
Smart Images
Figure CN120644244A_ABST
Abstract
Description
Background Art
[0001] Vehicle exhaust and fumes from fossil fuel combustion are currently significant contributors to urban air pollution. Besides CO2, nitrogen oxides (NO) are also major air pollutants. To simultaneously reduce emissions of CO2 and other gases such as NO and achieve efficient carbon resource utilization, it is practical to conduct photocatalytic CO2 reduction and photocatalytic NO oxidation reactions simultaneously in a single system. For photocatalytic CO2 reduction, the practical application of this technology is to achieve both CO2 reduction and water oxidation without the consumption of expensive sacrificial agents. In this regard, utilizing photogenerated holes to trigger meaningful chemical reactions is an ideal approach to improving the economic benefits of photocatalytic CO2 reduction technology. For photocatalytic NO oxidation, the photocatalytic process is induced by photoexcited holes. Therefore, by combining CO2 reduction with NO oxidation to create a reaction system that fully utilizes photogenerated electrons and holes, the photocatalytic CO2 reduction capability is enhanced, while increasing the utilization of photogenerated holes. Furthermore, theoretically, the separation of photogenerated electrons and holes can be significantly improved without the addition of sacrificial agents, ultimately enhancing both reduction and oxidation capabilities.
[0002] For photocatalytic NO oxidation, the presence of O2 is essential for the reaction to proceed properly. To achieve simultaneous photocatalytic CO2 reduction and NO oxidation, catalysts must exhibit high CO2 / O2 selectivity and excellent NO adsorption in the presence of CO2, NO, and O2. Microporous materials, such as microporous organic polymers, possess high surface area, abundant micropores, tunable framework structures, and excellent chemical and thermal stability, making them highly advantageous for the capture and separation of gas molecules. Incorporating CO2 adsorbents into photocatalytic systems has been shown to improve CO2 adsorption, enabling the enrichment of low-concentration CO2 and the photocatalytic reduction of CO2 to CH4, CO, and other gases. It has been reported that the heterocyclic microenvironment within microporous polymers can promote CO2 adsorption and also modulate the electronic properties of the metal center to facilitate CO2 activation. Inspired by the application of microporous polymers in CO2 separation, their superior adsorption capacity and selectivity suggest new opportunities for the direct utilization of low-concentration CO2 and NO in flue gas or air. Summary of the Invention
[0003] The technical problem solved by the present invention is to propose a method for a porous composite material with low cost and simple synthesis for efficient photocatalytic CO2 reduction and NO oxidation, the purpose of which is to optimize the preparation process of the porous material, the preparation method of the composite material and the porous material in the composite material, thereby solving the problem that the current traditional catalyst has poor adsorption capacity for molecules such as CO2 due to low specific surface area and lack of matching pore structure, especially in the presence of oxygen, which further limits the further improvement of photocatalytic CO2 reduction activity. The preparation method includes the following steps: (1) using the Stöber method to prepare SiO2 microspheres of different sizes; (2) using SiO2 as a template, tetraphenylporphyrin as a monomer, AlCl3 as a catalyst, and CHCl3 as a solvent to promote the Scholl reaction between the raw materials to obtain a crude porous material product, and then removing the template to prepare a conjugated polymer with a multi-level pore structure; (3) using a self-assembly method to load TiO2 nanoparticles on the porous material, and then coordinating metal Pd to prepare a porous composite material. The preparation method of the porous composite material provided by the present invention has a simple process, cheap and easily available raw materials, and can be used as an effective photocatalyst for oxidation-reduction reactions. The CH4 yield of TiO2 / TPP-TPP-Pd prepared by the present invention can reach 52 μmol g under pure CO2 conditions. -1 h -1 The oxidation of NO can be achieved in a pure NO atmosphere, with a conversion rate of up to 65%. In the presence of air and trace NO, efficient conversion of CO2 can still be achieved, with a CH4 yield of 14.3 μmol g -1 h -1 .
[0004] In order to solve the technical problem of the present invention, the technical solution proposed is: a method for using a porous composite material to achieve efficient photocatalytic redox reaction, the porous composite material is used for efficient photocatalytic CO2 reduction and / or NO oxidation, wherein the preparation method of the porous composite material is as follows: using SiO2 balls as templates, tetraphenylporphyrin as raw material, and CHCl3 as solvent, the raw material and the template are uniformly dispersed in an organic medium CHCl3 to obtain a reaction mixture, anhydrous aluminum chloride catalyst is added to the reaction mixture to promote cross-linking between the raw materials to obtain a porous material; the crude porous material product is etched, centrifuged, washed, and dried to obtain a conjugated porous material; the mixture of TiO2 nanoparticles and the porous material is dispersed in ethanol and ultrasonically treated, and then stirred to gradually evaporate the ethanol solvent while inducing the assembly of ultrafine TiO2 nanoparticles on the porous material, coordinated with metal Pd, to obtain a porous composite material.
[0005] Preferably, the porous material crude product is etched using a 2.5 M NaOH aqueous solution with a stirring time of 48 hours.
[0006] Preferably, the preparation of the porous composite material comprises the following steps:
[0007] (1) Preparation of SiO2 balls: Add tetraethyl orthosilicate to a mixed solution of 95% ethanol and ammonia water, o C and continue the reaction for 12 h to prepare SiO2 balls;
[0008] (2) Preparation of a reaction mixture: using SiO2 balls as templates, tetraphenylporphyrin as raw material, and CHCl3 as solvent, the raw material and template are uniformly dispersed in an organic medium CHCl3 to obtain a reaction mixture;
[0009] (3) Preparation of porous materials: adding anhydrous aluminum chloride catalyst to the reaction mixture to promote cross-linking between the raw materials to obtain porous materials;
[0010] (4) Removing the template: The crude porous material is etched in sodium hydroxide, and then centrifuged, washed, and dried to obtain the conjugated porous material;
[0011] (5) Preparation of porous composite materials: A mixture of 50 mg of TiO2 nanoparticles and porous materials was dispersed in 25 mL of ethanol and ultrasonicated for 30 min. Then, the mixture was stirred at 70 °C to allow the ethanol solvent to evaporate gradually while inducing the assembly of ultrafine TiO2 nanoparticles on the porous material and coordinating with metal Pd to obtain a porous composite material.
[0012] Preferably, the solvent used in the self-assembly process in step (5) is anhydrous ethanol, o C. Stir slowly until the solvent evaporates to 2-3 mL of solution, then stop stirring. After removing ethanol at room temperature, further dry in a vacuum drying oven for 5-8 hours.
[0013] Preferably, the method comprises the following steps:
[0014] (1) Preparation of SiO2 balls: Tetraethyl orthosilicate was added to a mixed solution of 95% ethanol and ammonia water at 40 o C for 12 h to prepare SiO2 spheres with a size of 100 nm;
[0015] (2) Preparation of reaction mixture: SiO2 balls were used as templates, tetraphenylporphyrin was used as raw materials, and CHCl3 was used as reaction medium. The template, raw materials, and solvent were added to a three-necked flask equipped with a reflux condenser and magnetically stirred for 1 h to obtain a reaction mixture.
[0016] (3) Preparation of porous materials: anhydrous aluminum chloride catalyst was added to the reaction mixture to generate a Scholl reaction to obtain a crude porous material product. Stirring was maintained during the polymerization process. The specific process of adding the catalyst to control the temperature was as follows: stirring at room temperature for 4 hours, heating to 30 °C for 8 hours, 40 °C for 12 hours, and 58 °C for 48 hours. After the reaction stopped, the mixture was cooled to room temperature, washed once with ethanol, and then washed twice with HCl-H2O mixed solution. The mixture was heated and stirred in a saturated potassium hydroxide solution for 40 minutes, and then centrifuged and washed with water and ethanol. Finally, the mixture was extracted with an ethanol solution for 24 hours. The obtained material was vacuum dried at 75 °C for 24 hours to obtain a polymer material.
[0017] (4) Removing the template: The crude porous material is added to a hydrofluoric acid solution, etched, centrifuged, washed, and dried to obtain a conjugated porous material, which is labeled as TPP-TPP.
[0018] (5) Preparation of TiO2 nanoparticles: Tetrabutyl titanate was dispersed in anhydrous ethanol and refluxed at 80 °C; then, a mixed solution of water and ethanol was added dropwise and refluxed at this temperature; after the reaction, the mixture was washed three times with ethanol and deionized water to obtain a white solid; the obtained wet solid was redispersed in a mixed solvent of water and N, N-dimethylformamide and subjected to a solvothermal reaction at 120 °C. After the reaction, the solution was collected by centrifugation and washed twice with ethanol and deionized water, respectively, and then dried in a vacuum oven overnight to obtain TiO2 nanoparticles;
[0019] (6) Preparation of porous composite materials: TiO2 nanoparticles and TPP-TPP were dispersed in anhydrous ethanol and ultrasonicated for 30 min at 70 o C and slowly stirred to induce the assembly of ultrafine TiO2 nanoparticles on the porous material. When the solvent evaporated to a small amount of solution, stirring was stopped. After removing the ethanol at room temperature, the mixture was further dried in a vacuum drying oven for 5-8 hours. The TiO2 / TPP-TPP powder was dispersed in 4 mL of acetonitrile solution and ultrasonicated for 5 minutes to obtain a uniformly dispersed solution. A certain amount of metal precursor H2PdCl4 was added and reacted at 40°C for 12 hours. After the reaction stopped, the sample was centrifuged and washed twice with deionized water and ethanol respectively, and extracted with anhydrous ethanol for 2 days to remove excess uncoordinated metal ions. Finally, the sample was freeze-dried for 1 day, and the resulting solids were labeled as TiO2 / TPP-TPP-Pd.
[0020] (7) The porous composite material prepared by the above method can achieve efficient CO2 reduction under pure CO2 conditions, and the CH4 yield can reach up to 52 μmol g -1 h -1At the same time, the conversion rate of NO oxidation can reach more than 65% under the condition of NO alone. Under the condition of coexistence of air and trace NO, the material can still achieve efficient CO2 conversion, and the CH4 yield can reach up to 14.3 μmol g -1 h -1 .
[0021] Beneficial effects:
[0022] The high specific surface area and abundant ultramicropore characteristics of the porous material of the present invention indicate that it has a high gas adsorption capacity. The specific surface area of the porous material prepared by the present invention is 1374 m2 under the conditions of 273 K / 1 bar. 2 g -1 , the adsorption capacity for CO2 is 88.5 cm 3 g -1 When the porous material is assembled with TiO2 nanoparticles, the optimal specific surface area of the composite material can reach 465 m by optimizing the ratio. 2 g -1 , which is 2.2 times the specific surface area of TiO2, making the CO2 adsorption capacity of TiO2 / TPP-TPP-Pd reach 52 cm at 273 K / 1 bar. 3 g -1 In addition, the selectivity of TiO2 / TPP-TPP-Pd for CO2 / O2 can reach 30.2, which means that even in the presence of O2 in a CO2 atmosphere, the sample can preferentially adsorb CO2 and ensure that CO2 can be enriched around the catalytic sites, promoting the efficient photocatalytic conversion of CO2. The results showed that the CH4 yield of the catalyst under pure CO2 conditions can reach 52 μmol g -1 h -1 At the same time, it can achieve efficient NO oxidation in a single NO atmosphere (500-600ppb), with a NO conversion rate of 65%. In addition, it can still achieve efficient CO2 reduction in the presence of air and trace NO, with a CH4 yield of 14.3 μmol g -1 h -1 .
[0023] The Rct value of the TiO2 / TPP-TPP-Pd composite material is much smaller than that of pure TiO2, indicating that the self-assembly of TiO2 and porphyrin polymer and the coordination with Pd improve the interfacial charge transfer, thereby greatly reducing the recombination loss of photogenerated electrons and holes.
[0024] Metals with different coordination factors affect their photocatalytic conversion under pure CO2 atmosphere. Figure 12It can be seen that the CH4 yields under pure CO2 conditions showed different trends, among which the coordinated Pd showed the highest CH4 yield (52.0 μmol g -1 h -1 ), followed by Pt (38.1 μmol g -1 h -1 ), Co (27.0 μmol g -1 h -1 ), Cu (26.1 μmolg -1 h -1 ), Au (14.6 μmol g -1 h -1 ) and Fe (9.4 μmol g -1 h -1 ). BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1 SEM image of SiO2 balls
[0026] Figure 2 TPP-TPP polymerization process
[0027] Figure 3 TEM image of TiO2 / TPP-TPP-Pd sample
[0028] Figure 4 BET diagrams of TiO2 / TPP-TPP-Pd and TPP-TPP samples
[0029] Figure 5 Comparison of pore size distribution of TiO2 / TPP-TPP-Pd and TPP-TPP samples
[0030] Figure 6 CO2 / O2 Adsorption Selectivity of TiO2 / TPP-TPP-Pd Samples
[0031] Figure 7 EIS graph of TiO2 / TPP-TPP-Pd and TiO2
[0032] Figure 8 CH4 yields of TiO2 / TPP-TPP-Pd and TiO2 in pure CO2
[0033] Figure 9 Conversion rate of photocatalytic NO oxidation of TiO2 / TPP-TPP-Pd and TiO2
[0034] Figure 10 CH4 production rate of TiO2 / TPP-TPP-Pd in the coexistence of CO2, O2 and NO
[0035] Figure 11 Comparison of the activity of composite materials prepared by different etching methods in pure CO2 system
[0036] Figure 12 Effect of the type of coordination metal on the activity in pure CO2 system DETAILED DESCRIPTION
[0037] Example 1
[0038] (1) Preparation of SiO2 balls: Add 0.75 mL of tetraethyl orthosilicate (TEOS) to a mixture of 40 mL of 95% ethanol and 2 mL of ammonia water. o C for 12 hours to prepare SiO2 spheres with a size of about 100 nm. Figure 1 As shown in the SEM image.
[0039] (2) Preparation of reaction mixture: SiO2 spheres were used as templates, tetraphenylporphyrin was used as raw material (0.12 g), and CHCl3 (1 mL) was used as reaction medium. The template, raw material, and solvent were added to a three-necked flask equipped with a reflux condenser (ensuring that the mass ratio of polymer to SiO2 after the reaction was 1:1). The mixture was stirred magnetically for 1 hour to obtain a reaction mixture.
[0040] (3) Preparation of porous materials: Anhydrous aluminum chloride catalyst (0.5 g) was added to the reaction mixture to generate a Scholl reaction to obtain a crude porous material product. The polymerization process (e.g. Figure 2 The reaction mixture was stirred continuously in a saturated potassium hydroxide solution for 40 minutes, and then centrifuged and washed with water and ethanol. Finally, the mixture was extracted with an ethanol solution for 24 hours. The obtained material was vacuum-dried at 75°C for 24 hours to obtain a polymer material.
[0041] (4) Template removal: 100 mg of the crude porous material prepared in step (3) was added to 10 mL of 2.5 M sodium hydroxide solution. After etching for 48 hours, the conjugated porous material was obtained after centrifugation, washing, and drying, and was represented by TPP-TPP.
[0042] (5) Preparation of TiO2 nanoparticles: 0.5 mL of tetrabutyl titanate (TBT) was dispersed in 50 mL of anhydrous ethanol and refluxed at 80 °C. Then, a mixed solution of water and ethanol was added dropwise and refluxed at this temperature. After the reaction was completed, the mixture was washed three times with ethanol and deionized water to obtain a white solid. The obtained wet solid was redispersed in a mixed solvent of water and N, N-dimethylformamide and subjected to a solvothermal reaction at 120 °C. After the reaction was completed, the solution was collected by centrifugation and washed twice with ethanol and deionized water, respectively, and then dried in a vacuum oven overnight to obtain TiO2 nanoparticles.
[0043] (6) Preparation of porous composite materials: 30 mg of TiO2 nanoparticles and 20 mg of the porous material prepared in step (4) were dispersed in 25 mL of anhydrous ethanol and ultrasonicated for 30 minutes at 70 o C and slowly stirred to induce the assembly of ultrafine TiO2 nanoparticles on the porous material. When the solvent evaporated to 2-3 mL of solution, stirring was stopped. After removing the ethanol at room temperature, it was further dried in a vacuum drying oven for 5-8 hours to obtain TiO2 / TPP-TPP. 40 mg of TiO2 / TPP-TPP powder was dispersed in 4 mL of acetonitrile solution, ultrasonicated for 5 min to obtain a uniformly dispersed solution, and a certain amount of metal precursor (H2PdCl4, to ensure that the amount of Pd is 4 mg) was added to react at 40 ℃ for 12 hours. After the reaction stopped, the sample was centrifuged and washed twice with deionized water and ethanol each, and extracted with anhydrous ethanol for 2 days to remove excess uncoordinated metal ions. Finally, the sample was freeze-dried for 1 day, and the resulting solids were labeled TiO2 / TPP-TPP-Pd, and the crystal morphology was as shown in the figure. Figure 3 As shown in the figure, because SiO2 was used as a template during polymer preparation, macropores of approximately 100 nm were formed on the polymer. TiO2 nanoparticles were then loaded onto the polymer via self-assembly in ethanol solvent. Due to the polymer's large specific surface area, the TiO2 was uniformly dispersed on the polymer surface. The TiO2 nanoparticles exhibited a uniform morphology and a narrow size distribution, primarily around 9.0 nm, with no apparent agglomeration.
[0044] Due to the introduction of porous polymer, TiO2 / TPP-TPP-Pd shows a steep nitrogen adsorption curve at low relative pressure (P / P0 < 0.001), reflecting that the sample has rich microporous structure, and TiO2 / TPP-TPP-Pd has obvious hysteresis loop under medium and high pressure conditions, indicating that there are both mesopores and macropores in the sample. Due to the introduction of polymer with hierarchical pore structure rich in micropores, mesopores and macropores, TiO2 / TPP-TPP-Pd (465 m 2 g-1 ) has a larger surface area than pure TiO2 (213 m 2 g -1 ) is 2.2 times higher, such as Figure 4 , as shown in 5.
[0045] The high specific surface area and abundant ultramicropores of the porous material indicate that it has a high gas adsorption capacity. The CO2 adsorption capacity of TiO2 / TPP-TPP-Pd can reach 52 cm at 1 bar and 273 K. 3 g −1 , which is 2.7 times the adsorption capacity of TiO2. In addition, since there is a large amount of O2 in the mixed system (NO and air), the selective adsorption of CO2 / O2 by the sample plays a crucial role in the conversion of CO2 in the mixed system. Figure 6 As shown in the figure, at 1 bar and 273 K, the selectivity of TiO2 / TPP-TPP-Pd for CO2 / O2 can reach 30.2, which means that when O2 exists in a CO2 atmosphere, the sample can preferentially adsorb CO2. Based on the above results, it can be concluded that TiO2 / TPP-TPP-Pd also exhibits good CO2 adsorption performance in an oxygen-rich environment or air conditions. In addition, the Rct value of the TiO2 / TPP-TPP-Pd composite material is much smaller than that of pure TiO2, indicating that the self-assembly of TiO2 and porphyrin polymer and the coordination with Pd improve the interfacial charge transfer, thereby greatly reducing the recombination loss of photogenerated electrons and holes ( Figure 7 ).
[0046] (7) The porous composite material prepared according to the above method was first tested for its photocatalytic CO2 reduction performance in a gas-solid phase system with water as an electron donor under normal pressure. 30 mg of catalyst powder sample was dispersed in the middle of a culture vessel and placed in a customized sealed glass container, which was then evacuated after sealing. Then, pure CO2 was introduced into the reactor to maintain normal pressure. After 1 h of illumination using a 300 W xenon lamp, the photocatalytic reaction was analyzed using the FID detector of a gas chromatograph. The results showed that the catalyst could reduce CO2 to CH4 and CO under pure CO2 conditions, with the yield of CH4 as a high-electron product reaching 52 μmol g -1 h -1 ( Figure 8 ), is TiO2 (8.2 μmol g -1 h -1 ). Meanwhile, the performance of the sample in photocatalytic NO oxidation was tested in a mobile phase reactor. 100 mg of photocatalyst was placed in the reactor and sealed. A mixed gas containing 500-600 ppb NO was introduced at a rate of 4.0 L min −1The reactor is fed with a constant rate of 100 ppm and maintained at atmospheric pressure. After the gas reaches adsorption-desorption equilibrium on the photocatalyst, the photocatalytic reaction is carried out under illumination. The NO concentration is measured every hour using a NO analyzer to test the NO conversion rate. TiO2, a preferred NO oxidation photocatalyst, achieves a NO conversion rate of 45% under full illumination. When TiO2 is assembled on TPP-TPP and coordinated with Pd, the NO conversion rate increases to 65% ( Figure 9 ); It can be seen that for the NO oxidation reaction, the increase in specific surface area and the introduction of coordination metals do not significantly improve the NO conversion rate. Therefore, it can be considered that the activity contribution of the composite material TiO2 / TPP-TPP-Pd to catalytic NO oxidation mainly comes from TiO2, that is, the catalytic sites of the NO oxidation reaction are mainly concentrated on TiO2. In addition, inspired by the high CO2 / O2 adsorption selectivity of TiO2 / TPP-TPP-Pd under oxygen-rich conditions, the catalyst was simultaneously subjected to photocatalytic CO2 reduction-NO oxidation reaction in a mixed gas system (100 ppm NO + air) and the effect of the presence of O2 and NO on the photocatalytic CO2 reduction reaction was investigated. 30 mg of photocatalyst was placed in a reactor and the reactor was sealed. A mixture of air and NO was introduced into the reactor to ensure that the gas in the reactor was at normal pressure. A 300 W xenon lamp was used for illumination, and the CO2 reduction product was detected after 1 h of illumination. The results are shown in the figure. Figure 10 As shown in Figure 2, the CH4 yield of the TiO2 / TPP-TPP-Pd catalyst in the mixed system was 14.3 μmol g -1 h -1 , can still maintain a high level,
[0047] However, although TiO2 has good NO conversion performance under oxygen-rich conditions, the strong competitive adsorption of O2 on TiO2 inhibits the conversion of CO2 to CH4. In contrast, due to the high selective adsorption capacity of CO2 by TiO2 / TPP-TPP-Pd and the low NO concentration that is insufficient to significantly affect CO2 adsorption, it can achieve not only high NO conversion performance but also high CH4 yield under air conditions. Therefore, TiO2 / TPP-TPP-Pd can be used as a dual-functional photocatalyst for photocatalytic CO2 reduction and NO oxidation.
[0048] Example 2
[0049] In the material preparation process of Example 2, steps (1), (2), (3), and (5) are the same as those of Example 1, except that during the template removal process, 10 mL of 2.5 M NaOH or 5% HF is used to etch the material in step (3) to remove SiO2. The specific process is as follows:
[0050] (4) Template removal: 100 mg of the crude porous material prepared in step (3) was added to 10 mL of 2.5 M sodium hydroxide solution or 5% HF and etched for 48 hours. After the reaction, the conjugated porous material was obtained by centrifugation, washing, and drying, which were represented by TPP-TPP-NaOH and TPP-TPP-HF, respectively.
[0051] (6) Preparation of porous composite materials: 30 mg of TiO2 nanoparticles and 20 mg of the porous material prepared in step (4) were dispersed in 25 mL of anhydrous ethanol and ultrasonicated for 30 minutes at 70 o C and slowly stirred to induce the assembly of ultrafine TiO2 nanoparticles on the porous material. When the solvent evaporated to 2-3 mL of solution, stirring was stopped. After removing ethanol at room temperature, it was further dried in a vacuum drying oven for 5-8 hours to obtain TiO2 / TPP-TPP-NaOH or TiO2 / TPP-TPP-HF. 40 mg of TiO2 / TPP-TPP-NaOH or TiO2 / TPP-TPP-HF powder was dispersed in 4 mL of acetonitrile solution and ultrasonicated for 5 minutes to obtain a uniformly dispersed solution. A certain amount of metal precursor (H2PdCl4, ensuring that the amount of Pd is 4 mg) was added and reacted at 40 ℃ for 12 hours. After the reaction stopped, the sample was centrifuged and washed twice with deionized water and ethanol respectively, and extracted with anhydrous ethanol for 2 days to remove excess uncoordinated metal ions. Finally, the samples were freeze-dried for 1 day, and the obtained solids were labeled as TiO2 / TPP-TPP-Pd-1 and TiO2 / TPP-TPP-Pd-2, respectively.
[0052] (7) The porous composite material prepared by the above method, the polymer obtained after NaOH etching under pure CO2 conditions and the subsequent composite material showed a high CH4 yield ( Figure 11 ), indicating that the etching method affects its photocatalytic conversion under pure CO2 atmosphere. Figure 11 Comparison of the activities of composite materials prepared by different etching methods in a pure CO2 system (1 represents TiO2 / TPP-TPP-Pd-1, and 2 represents TiO2 / TPP-TPP-Pd-2).
[0053] Example 3
[0054] In the material preparation process of Example 3, steps (1), (2), (3), and (4) are the same as those of Example 1, except that in step (5), the type of TiO2 / TPP-TPP coordination metal is changed. The specific preparation process is as follows:
[0055] (5) Preparation of porous composite materials: 30 mg of TiO2 nanoparticles and 20 mg of the porous material prepared in step (4) were dispersed in 25 mL of anhydrous ethanol and ultrasonicated for 30 min at 70 o C and slowly stirred to induce the assembly of ultrafine TiO2 nanoparticles on the porous material. When the solvent evaporated to 2-3 mL of solution, stirring was stopped. After removing ethanol at room temperature, it was further dried in a vacuum drying oven for 5-8 hours to obtain TiO2 / TPP-TPP. 40 mg of TiO2 / TPP-TPP powder was dispersed in 4 mL of acetonitrile solution and ultrasonicated for 5 minutes to obtain a uniformly dispersed solution. A certain amount of metal precursor (H2PdCl4, H2PtCl6, FeCl3, (CH3COO)2Co, Cu(NO3)2, HAuCl4, where the metal content was 4 mg) was added and reacted at 40 ℃ for 12 hours. After the reaction stopped, the sample was centrifuged and washed twice with deionized water and ethanol respectively, and extracted with anhydrous ethanol for 2 days to remove excess uncoordinated metal ions. Finally, the samples were freeze-dried for 1 day, and the obtained solids were labeled as TiO2 / TPP-TPP-Pd, TiO2 / TPP-TPP-Pt, TiO2 / TPP-TPP-Fe, TiO2 / TPP-TPP-Co, TiO2 / TPP-TPP-Cu, and TiO2 / TPP-TPP-Au, respectively.
[0056] (6) The CH4 yield of the porous composite material prepared according to the above method under pure CO2 conditions showed different trends ( Figure 12 ), among which the coordinated Pd showed the highest CH4 yield (52.0 μmol g -1 h -1 ), followed by Pt (38.1 μmol g -1 h -1 ), Co (27.0 μmol g -1 h -1 ), Cu (26.1 μmol g -1 h -1 ), Au (14.6 μmol g -1 h -1 ) and Fe (9.4 μmolg -1 h -1 ), which clearly shows that metals with different coordination groups affect their photocatalytic conversion under pure CO2 atmosphere conditions. Figure 12Effect of the type of coordination metal on the activity in the pure CO2 system (1 represents TiO2 / TPP-TPP-Pd, 2 represents TiO2 / TPP-TPP-Pt, 3 represents TiO2 / TPP-TPP-Fe, 4 represents TiO2 / TPP-TPP-Co, 5 represents TiO2 / TPP-TPP-Cu, and 6 represents TiO2 / TPP-TPP-Au).
[0057] The present invention is not limited to the specific technical solutions described in the above embodiments, and all technical solutions formed by equivalent replacement are within the protection scope required by the present invention.
Claims
1. A method for achieving efficient photocatalytic redox reaction using a porous composite material, characterized by: The porous composite material is used for efficient photocatalytic CO2 reduction and / or NO oxidation, wherein the preparation method of the porous composite material is as follows: using SiO2 balls as templates, tetraphenylporphyrin as raw material, and CHCl3 as solvent, the raw material and the template are uniformly dispersed in an organic medium CHCl3 to obtain a reaction mixture, anhydrous aluminum chloride catalyst is added to the reaction mixture to promote cross-linking between the raw materials to obtain a porous material; a crude product of the porous material is etched, centrifuged, washed, and dried to obtain a conjugated porous material; a mixture of TiO2 nanoparticles and the porous material is dispersed in ethanol, ultrasonicated, and then stirred to gradually evaporate the ethanol solvent while inducing the assembly of ultrafine TiO2 nanoparticles on the porous material and coordinating metal Pd to obtain a porous composite material.
2. The method for realizing efficient photocatalytic redox reaction using the porous composite material according to claim 1, characterized in that: The porous material crude product was etched using a 2.5 M NaOH aqueous solution with a stirring time of 48 hours.
3. The method for realizing efficient photocatalytic redox reaction using the porous composite material according to claim 1, characterized in that: The preparation of the porous composite material comprises the following steps: (1) Preparation of SiO2 balls: Add tetraethyl orthosilicate to a mixed solution of 95% ethanol and ammonia water, o C and continue the reaction for 12 h to prepare SiO2 balls; (2) Preparation of a reaction mixture: using SiO2 balls as templates, tetraphenylporphyrin as raw material, and CHCl3 as solvent, the raw material and template are uniformly dispersed in an organic medium CHCl3 to obtain a reaction mixture; (3) Preparation of porous materials: adding anhydrous aluminum chloride catalyst to the reaction mixture to promote cross-linking between the raw materials to obtain porous materials; (4) Removing the template: The crude porous material is etched in sodium hydroxide, and then centrifuged, washed, and dried to obtain the conjugated porous material; (5) Preparation of porous composite materials: A mixture of 50 mg of TiO2 nanoparticles and porous materials was dispersed in 25 mL of ethanol and ultrasonicated for 30 min. Then, the mixture was stirred at 70 °C to allow the ethanol solvent to evaporate gradually while inducing the assembly of ultrafine TiO2 nanoparticles on the porous material and coordinating with metal Pd to obtain a porous composite material.
4. The method for realizing efficient photocatalytic redox reaction using a porous composite material according to claim 3, characterized in that: The solvent used in the self-assembly process in step (5) is anhydrous ethanol, which is heated at 70 o C. Stir slowly until the solvent evaporates to 2-3 mL of solution, then stop stirring. After removing ethanol at room temperature, further dry in a vacuum drying oven for 5-8 hours.
5. The method for realizing efficient photocatalytic redox reaction using a porous composite material according to claim 1, characterized in that: The following steps are involved: (1) Preparation of SiO2 balls: Tetraethyl orthosilicate was added to a mixed solution of 95% ethanol and ammonia water at 40 o C for 12 h to prepare SiO2 spheres with a size of 100 nm; (2) Preparation of reaction mixture: SiO2 balls were used as templates, tetraphenylporphyrin was used as raw materials, and CHCl3 was used as reaction medium. The template, raw materials, and solvent were added to a three-necked flask equipped with a reflux condenser and magnetically stirred for 1 h to obtain a reaction mixture. (3) Preparation of porous materials: anhydrous aluminum chloride catalyst was added to the reaction mixture to generate a Scholl reaction to obtain a crude porous material product. Stirring was maintained during the polymerization process. The specific process of adding the catalyst to control the temperature was as follows: stirring at room temperature for 4 hours, heating to 30 °C for 8 hours, 40 °C for 12 hours, and 58 °C for 48 hours. After the reaction stopped, the mixture was cooled to room temperature, washed once with ethanol, and then washed twice with HCl-H2O mixed solution. The mixture was heated and stirred in a saturated potassium hydroxide solution for 40 minutes, and then centrifuged and washed with water and ethanol. Finally, the mixture was extracted with an ethanol solution for 24 hours. The obtained material was vacuum dried at 75 °C for 24 hours to obtain a polymer material. (4) Removing the template: The crude porous material is added to a hydrofluoric acid solution, etched, centrifuged, washed, and dried to obtain a conjugated porous material, which is labeled as TPP-TPP. (5) Preparation of TiO2 nanoparticles: Tetrabutyl titanate was dispersed in anhydrous ethanol and refluxed at 80 °C; then, a mixed solution of water and ethanol was added dropwise and refluxed at this temperature; after the reaction, the mixture was washed three times with ethanol and deionized water to obtain a white solid; the obtained wet solid was redispersed in a mixed solvent of water and N, N-dimethylformamide and subjected to a solvothermal reaction at 120 °C. After the reaction, the solution was collected by centrifugation and washed twice with ethanol and deionized water, respectively, and then dried in a vacuum oven overnight to obtain TiO2 nanoparticles; (6) Preparation of porous composite materials: TiO2 nanoparticles and TPP-TPP were dispersed in anhydrous ethanol and ultrasonicated for 30 min at 70 o C and slowly stirred to induce the assembly of ultrafine TiO2 nanoparticles on the porous material. When the solvent evaporated to a small amount of solution, stirring was stopped. After removing the ethanol at room temperature, the mixture was further dried in a vacuum drying oven for 5-8 hours. The TiO2 / TPP-TPP powder was dispersed in 4 mL of acetonitrile solution and ultrasonicated for 5 minutes to obtain a uniformly dispersed solution. A certain amount of metal precursor H2PdCl4 was added and reacted at 40°C for 12 hours. After the reaction stopped, the sample was centrifuged and washed twice with deionized water and ethanol respectively, and extracted with anhydrous ethanol for 2 days to remove excess uncoordinated metal ions. Finally, the sample was freeze-dried for 1 day, and the resulting solids were labeled as TiO2 / TPP-TPP-Pd. (7) The porous composite material prepared by the above method can achieve efficient CO2 reduction under pure CO2 conditions, and the CH4 yield can reach up to 52 μmol g -1 h -1 At the same time, the conversion rate of NO oxidation can reach more than 65% under the condition of NO alone. Under the condition of coexistence of air and trace NO, the material can still achieve efficient CO2 conversion, and the CH4 yield can reach up to 14.3 μmol g -1 h -1 .