MOF loaded ferrocene composite material as well as preparation method and application thereof

Abstract

The invention discloses an MOF (Metal Organic Framework) loaded ferrocene composite material and a preparation method and application thereof, the composite material takes a metal organic framework MOF-545 as a main framework, a ferriporphyrin carboxylic acid ligand is used for constructing a photoactive center, and the ferrocene carboxylic acid ligand is anchored on a zirconium-oxygen cluster node of the MOF-545 through a Zr-O coordinate bond. Compared with an unmodified material, the material provided by the invention has better light absorption capacity, higher photon-generated carrier separation and migration efficiency and lower interface charge transfer impedance, and shows higher carbon monoxide generation activity and good cycle stability in photocatalytic carbon dioxide reduction reaction.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic materials, specifically, it relates to a MOF-supported ferrocene composite material, its preparation method, and its application. Background Technology

[0002] The greenhouse effect and energy crisis caused by massive carbon dioxide emissions are pressing global environmental and energy problems that urgently need to be addressed. Utilizing solar energy to drive the conversion of carbon dioxide into high-value-added carbon-containing products is an effective technological route that balances carbon emission reduction and energy conversion. Photocatalytic carbon dioxide reduction has become a research hotspot in this field due to its advantages of mild reaction conditions and direct utilization of solar energy.

[0003] Traditional semiconductor photocatalysts (such as TiO2, CdS, and ZnO) have inherent defects: limited band gap range leading to insufficient light absorption capacity, rapid photogenerated electron-hole recombination rate, and scarce and unevenly dispersed catalytic active sites, making it difficult to meet the product yield and selectivity requirements of carbon dioxide photoreduction for practical applications. While existing technologies can optimize performance through carbon / nitrogen-based material doping and surface modification with noble metal co-catalysts (Pd, Pt, etc.), these methods lack precise structural control strategies at the atomic / molecular level, failing to achieve targeted construction and functional customization of catalytic active sites; furthermore, the use of noble metals significantly increases preparation costs, limiting large-scale applications.

[0004] Metal-organic frameworks (MOFs) possess advantages such as large specific surface area, tunable pore structure, and designable metal nodes and organic ligands, providing an excellent platform for constructing highly efficient photocatalysts. Among them, porphyrin-based MOF-545 combines light-absorbing units and catalytic active centers, showing potential application value in the field of photocatalytic CO2 reduction. However, MOF-545 suffers from limited charge transfer efficiency from organic ligands to metal nodes, and long and resistant electron conduction paths, resulting in defects similar to most MOF photocatalysts, such as insufficient charge separation efficiency and low interfacial electron transport rates.

[0005] Existing MOF modification technologies mainly include ligand engineering and node engineering: Although ligand engineering can introduce photosensitive motifs or molecular catalytic centers, it requires the design of special ligands, the synthesis process is complex, and the stability of some introduced coordination structures is insufficient, which is not conducive to long-term photocatalytic reactions; Node engineering can directly utilize the coordination sites of metal cluster nodes to introduce functional components, which can improve the photoelectric and catalytic performance of materials while maintaining the overall stability of the framework structure, and is a modification method with greater application potential.

[0006] Ferrocene compounds are readily available organometallic compounds with a stable sandwich structure. Their d orbitals extend the π-electron conjugation system of the cyclopentadienyl ligands, endowing them with excellent electron-donating capabilities. Simultaneously, the reversible redox properties of iron ions enable them to possess highly efficient charge transport performance. Introducing ferrocene into the zirconium-oxygen cluster nodes of MOF-545 via stable coordination is expected to construct new electron transport pathways within the framework, thereby improving the separation efficiency of photogenerated carriers and catalytic reactivity.

[0007] Therefore, developing ferrocene-modified MOF-545 composite materials and applying them to photocatalytic CO2 reduction is of great practical significance for carbon emission reduction and clean energy conversion. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a MOF-supported ferrocene composite material, its preparation method and application.

[0009] To achieve the above objectives, the technical solution of the present invention is as follows:

[0010] In a first aspect, the present invention provides a MOF-supported ferrocene composite material, wherein the composite material uses a metal-organic framework MOF-545 as the main skeleton and iron porphyrin carboxylic acid ligands to construct photoactive centers, and the ferrocene carboxylic acid ligands are anchored to the zirconium oxide cluster nodes of MOF-545 through Zr-O coordination bonds.

[0011] In a preferred embodiment, the ferrocene carboxylic acid ligand is ferroceneformic acid or ferroceneacetic acid.

[0012] In a preferred embodiment, the iron porphyrin carboxylic acid ligand is iron tetra(4-carboxyphenyl)porphyrin.

[0013] Secondly, the present invention provides a method for preparing the composite material as described above. The method adopts an in-situ modified solvothermal method for one-step preparation, specifically including: adding ferrotetra(4-carboxyphenyl)porphyrin and zirconium salt ZrOCl2·8H2O to an organic solvent for mixing and dissolving, adding a regulator and ferrocene carboxylic acid, placing it in a closed reaction vessel for solvothermal reaction, and after the reaction, performing solid-liquid separation, washing, and drying to obtain the composite material.

[0014] In a preferred embodiment, the organic solvent is any one of N,N-dimethylacetamide, N,N-dimethylformamide, and dimethyl sulfoxide.

[0015] In a preferred embodiment, the regulator is any one of benzoic acid, trifluoroacetic acid, glacial acetic acid, hydrochloric acid, and trifluoromethanesulfonic acid.

[0016] In a preferred embodiment, the mass ratio of ferrocene carboxylic acid to ferrotetra(4-carboxyphenyl)porphyrin is 1:6-1.5:1.

[0017] In a preferred embodiment, the mass ratio of ferrocene carboxylic acid to ferrotetra(4-carboxyphenyl)porphyrin is 1:2.

[0018] In a preferred embodiment, the temperature of the solvothermal reaction is 100-140°C, and the reaction time is 12-36 h.

[0019] Thirdly, the present invention also provides the application of the composite material described above in the photocatalytic reduction of CO2 to CO reaction.

[0020] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art.

[0021] 1. This invention anchors ferrocene carboxylic acid ligands to zirconium-oxygen cluster nodes of MOF-545 through node engineering, forming a stable structure with Zr-O coordination bonds. This creates an additional electron transport path within the framework, effectively improving the separation and migration efficiency of photogenerated carriers and reducing the interfacial charge transport impedance, while maintaining the crystal structure and pore structure characteristics of the original MOF-545 framework.

[0022] 2. The composite material prepared by this invention exhibits ultra-high activity in the visible light photocatalytic reduction of CO2 to CO. Among them, the highest CO generation rate of the ferrocene-modified MOF-545 composite material is 940.2 μmol / g / h, which is 1.88 times that of the unmodified MOF-545 and 16.1 times that of the iron-free MOF-545. Moreover, the product selectivity is high, and only CO is reduced.

[0023] 3. The composite material prepared by this invention has excellent catalytic stability. After four recycling and reuse, the photocatalytic performance has almost no degradation and can be reused.

[0024] 4. The preparation method provided by the present invention adopts an in-situ modified solvothermal method for one-step synthesis, which does not require complicated precursor preparation and post-processing steps. It is simple to operate, does not require a harsh reaction environment, and does not use precious metal raw materials, so it is low in cost, environmentally friendly, and conducive to large-scale industrial production and application.

[0025] 5. This invention provides a new approach to the modification of MOF-based photocatalysts and also provides high-performance catalyst materials for the practical application of photocatalytic CO2 reduction technology. Attached Figure Description

[0026] The accompanying drawings, as part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention, but do not constitute an undue limitation of the invention. Obviously, the drawings described below are merely some embodiments, and those skilled in the art can obtain other drawings based on these drawings without creative effort. In the drawings:

[0027] Figure 1 The X-ray powder diffraction patterns of MOF-545 and MOF-545-ferrocene composite materials in the embodiments of the present invention are shown below.

[0028] Figure 2 The infrared spectra of ferrocene carboxylic acid, MOF-545, and MOF-545-ferrocene composite materials in the embodiments of the present invention are shown.

[0029] Figure 3 The X-ray photoelectron spectra of MOF-545 and MOF-545-ferrocene composite materials in the embodiments of the present invention are shown below.

[0030] Figure 4 The images shown are electron microscope images of MOF-545 and MOF-545-ferrocene composite materials in the embodiments of the present invention.

[0031] Figure 5 These are scanning electron microscope images of MOF-545 and MOF-545-ferrocene composite materials in embodiments of the present invention;

[0032] Figure 6 The graph shows the photoelectrochemical performance test results of MOF-545 and MOF-545-ferrocene composite materials in the embodiments of the present invention.

[0033] Figure 7 The diagram shows the photocatalytic CO2 reduction performance of MOF-545 and MOF-545-ferrocene composite materials in the embodiments of the present invention.

[0034] Figure 8 The image shows the photocatalytic CO2 reduction stability test results of the relevant MOF-545-ferrocene composite material in the embodiments of the present invention.

[0035] It should be noted that these accompanying drawings and textual descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art by referring to specific embodiments. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0037] [Comparative Example]

[0038] This embodiment provides an example of a method for preparing MOF-545, as follows:

[0039] Weigh 33 mg of tetra(4-carboxyphenyl)porphyrin and 108 mg of ZrOCl2·8H2O, add them to 10 mL of N,N-dimethylformamide, then add 0.45 mL of trifluoroacetic acid. After ultrasonic dispersion for 30 min, seal the container and allow it to react solvothermically at 120 °C for 20 h. After the reaction is complete, filter and collect the solid. Wash thoroughly with N,N-dimethylformamide to remove unreacted precursors, then wash several times with acetone. Finally, dry under vacuum at 80 °C overnight to obtain a purple powder, MOF-545.

[0040] [Example 1]

[0041] This embodiment provides an example of a preparation method for MOF-545-ferrocene carboxylic acid composite material, which is prepared in one step using an in-situ modified solvothermal method, as detailed below:

[0042] Weigh 33 mg of tetra(4-carboxyphenyl)porphyrin and 108 mg of ZrOCl2·8H2O, add them to 10 mL of N,N-dimethylformamide, add 0.45 mL of trifluoroacetic acid, and sonicate to disperse until homogeneous. Then add 15 mg of ferrocene carboxylic acid to the system and continue sonication for 20 min. Seal the mixture and react it at 120 °C for 20 h. After the reaction is complete, filter and collect the solid, wash it successively with N,N-dimethylformamide and acetone, and finally vacuum dry it overnight at 80 °C to obtain a brownish-yellow powder of ferrocene acetic acid-modified MOF-545 composite material MOF-545-Fca.

[0043] Among them, ferrotetra(4-carboxyphenyl)porphyrin can be prepared by the following method:

[0044] 272 mg of tetratetra(4-carboxyphenyl)porphyrin and 497 mg of ferric chloride hexahydrate were added to 15 mL of N,N-dimethylformamide, mixed thoroughly, and placed in a sealed container. The mixture was reacted at 100 °C for 20 h. After the reaction was complete, 10 times the volume of water was added to the reaction solution, and the solid was collected by filtration. The obtained solid was dissolved in chloroform, washed twice with 1 mol / L hydrochloric acid, and then washed with water until neutral. After separating the organic phase, anhydrous magnesium sulfate was added for drying, and the solvent was removed by rotary evaporation to obtain a dark purple solid product, namely tetratetra(4-carboxyphenyl)porphyrin.

[0045] [Example 2]

[0046] This embodiment provides an example of a method for preparing MOF-545-ferroceneacetic acid composite material. In Example 1, ferrocene carboxylic acid is replaced with ferroceneacetic acid, while keeping the other conditions unchanged, to obtain a brownish-yellow powdery ferroceneacetic acid node-modified MOF-545 composite material MOF-545-Fcaa.

[0047] Figure 1 The X-ray powder diffraction patterns of MOF-545, MOF-545-Fca, and MOF-545-Fcaa in Comparative Examples and Examples 1 and 2 are shown in the figure. As shown, the X-ray diffraction peak positions of MOF-545-Fcaa, MOF-545-Fca, and MOF-545 are consistent with the diffraction peak positions of MOF-545 single crystal, indicating that after introducing ferrocene guest through node engineering, the crystal structure of the metal-organic framework remains stable and has good crystallinity.

[0048] Figure 2 The infrared spectra of ferrocene carboxylic acid, MOF-545, MOF-545-Fca, and MOF-545-Fcaa are shown in the comparative examples and in Examples 1 and 2. As shown in the figure, the Fourier transform infrared spectra of MOF-545-Fcaa and MOF-545-Fca are at 430 cm⁻¹. -1 and 1102cm -1 Typical absorption peaks appeared at [value missing], corresponding to the stretching vibration of Fe-cyclopentadiene (Fe-Cp) and the C / C skeletal vibration of the cyclopentadiene ring (Cp) in ferrocene carboxylic acid, respectively. This result directly confirms that the ferrocene carboxylic acid group has been successfully introduced into the framework structure of MOF-545. It is noteworthy that the C=O double bond of the carboxylic acid in the ferrocene guest [value missing] (1660 cm⁻¹). -1 ) and CO single bond (1288cm) -1 The stretching vibration peak of ) completely disappeared in the spectra of MOF-545-Fcaa and MOF-545-Fca, indicating that the carboxylic acid group of the ferrocene carboxylic acid ligand was completely deprotonated and coordinated with the zirconium ion node.

[0049] Figure 3 X-ray photoelectron spectra of MOF-545, MOF-545-Fca, and MOF-545-Fcaa in Comparative Examples and Examples 1 and 2 are shown in the figure. As shown, in the high-resolution zirconium 3d spectrum, the Zr 3d of MOF-545-Fcaa is... 5 / 2 and Zr3d 3 / 2The characteristic binding energies are 182.88 eV and 185.17 eV, respectively, both showing a negative shift compared to MOF-545-Fca (182.90 eV, 185.28 eV) and MOF-545 (182.96 eV, 185.35 eV). This phenomenon can be attributed to the covalent anchoring of electron-donating ferrocene carboxylic acid to the zirconium-oxygen cluster of MOF-545, which increases the electron cloud density around the zirconium site. Furthermore, compared to MOF-545, the binding energies of nitrogen (398.49 eV, 400.35 eV) and oxygen (531.99 eV, 536.62 eV) in MOF-545-Fcaa, and the binding energies of nitrogen (398.45 eV, 400.17 eV) and oxygen (531.90 eV, 534.18 eV) in MOF-545-Fca both showed a slight positive shift. This phenomenon indicates that the electron cloud density of the carboxylic acid group and pyrrole nitrogen atom decreased after the introduction of ferrocene carboxylic acid. This is because the electron-rich ferrocene group enhances the conductivity of MOF-545 and accelerates the migration of electrons from the ligand to the metal active site. Two sets of characteristic peaks were observed in the X-ray photoelectron spectrum of iron 2p, corresponding to Fe(II)2p. 3 / 2 2p 1 / 2 and Fe(III)2p 3 / 2 2p 1 / 2 Typically, the reversible redox properties of ferrocene allow for reversible single-electron transfer between the oxidation states of iron, specifically Fe(II) and Fe(III).

[0050] Figure 4 Scanning and transmission electron microscopy (SEM) images of MOF-545, MOF-545-Fca, and MOF-545-Fcaa from comparative examples and Examples 1 and 2 are shown. As shown, MOF-545-Fcaa and MOF-545-Fca retain the spindle-shaped morphology of MOF-545. Energy dispersive spectroscopy (EDS) elemental mapping results in transmission electron microscopy mode show that carbon, oxygen, nitrogen, zirconium, and iron are uniformly distributed in the three metal-organic framework samples.

[0051] Figure 5 The nitrogen adsorption-desorption curves of MOF-545, MOF-545-Fca, and MOF-545-Fcaa in Examples 1 and 2 are shown in the figure. As shown, the specific surface areas of MOF-545, MOF-545-Fca, and MOF-545-Fcaa are basically the same, and all three samples exhibit a type I nitrogen adsorption-desorption isotherm, which is characteristic of microporous materials. The pore size distribution curves show that the pore size of the three samples is concentrated at around 2.59 nm.

[0052] Figure 6The figure shows the photoelectric physical properties of MOF-545, MOF-545-Fca, and MOF-545-Fcaa in comparative examples and Examples 1 and 2. As shown in the figure, the photoluminescence intensity of MOF-545-Fcaa is lower than that of MOF-545-Fca and the original MOF-545, indicating that the relaxation process of excited electrons to ground state electrons and the recombination of photogenerated electron-hole pairs are effectively suppressed. The average fluorescence lifetimes of MOF-545, MOF-545-Fca, and MOF-545-Fcaa are 4.85 ns, 7.58 ns, and 13.16 ns, respectively. MOF-545-Fcaa has the longest average fluorescence lifetime, indicating that its excited state electron lifetime is extended and the photogenerated electron transfer rate is accelerated, thus allowing more photogenerated electrons to participate in the photocatalytic reaction. Both MOF-545-Fcaa and MOF-545-Fca exhibit higher photocurrent responses than the original MOF-545, confirming that the introduction of ferrocene carboxylic acid enhances the photogenerated electron separation capability of the material. MOF-545-Fcaa shows a smaller semicircle diameter in its electrochemical impedance spectroscopy (EIS) Nyquist plot, indicating lower electron transfer resistance.

[0053] [Application Example 1]

[0054] In this embodiment, MOF-545, MOF-545-Fca and MOF-545-Fcaa prepared in the comparative example and in Example 1 and Example 2 were used for visible light catalytic CO2 reduction, and their photocatalytic CO2 reduction performance was tested.

[0055] 10 mg of catalyst, 60 mL of acetonitrile, 6 mL of triethanolamine, and 10 mg of tris(2,2'-bipyridine)ruthenium dichloride were added to a 300 mL photocatalytic glass reactor. After sealing the reactor, CO2 was introduced for 30 min to saturate the system under atmospheric pressure. A xenon lamp equipped with a 400 nm cutoff filter was used as the light source for irradiation, and circulating cooling was maintained. The reaction was allowed to proceed for 5 h, and gas samples were taken every 1 h for gas chromatography analysis to detect the products. The results are as follows: Figure 7 .

[0056] Figure 7 The figure shows a comparison of the photocatalytic CO2 reduction to CO activities of MOF-545, MOF-545-Fca, and MOF-545-Fcaa. As shown in the figure, during the 5-hour photocatalytic reaction, the total CO yield of MOF-545-Fcaa reached 1733.1 μmol / g / h, and the highest CO generation rate was 940.2 μmol / g / h, which are 1.77 times that of MOF-545-Fca (531.6 μmol / g / h), 1.88 times that of MOF-545 (500.7 μmol / g / h), and 16.1 times that of the iron-free MOF-545 (58.4 μmol / g / h), respectively.

[0057] [Application Example 2]

[0058] In this embodiment, the visible light catalytic CO2 reduction activity experiment of Application Example 1 was performed in 5 cycles. That is, after one reaction, the catalyst was filtered, dried and recovered, and then the next round of reaction was carried out. The photocatalytic CO2 reduction stability was tested in 4 consecutive measurements. The results are as follows: Figure 8 .

[0059] Figure 8 The figure shows the photocatalytic CO2 reduction stability test result of MOF-545-Fcaa in Example 2. As shown in the figure, after four recycling cycles, it still maintains good photocatalytic performance, indicating that the material has good catalytic stability.

[0060] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present invention. The implementation schemes in the above embodiments can also be further combined or replaced. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A MOF-supported ferrocene composite material, characterized in that: The composite material uses metal-organic framework MOF-545 as the main skeleton, and iron porphyrin carboxylic acid ligands to construct photoactive centers. Ferrocene carboxylic acid ligands are anchored to zirconium oxide cluster nodes of MOF-545 through Zr-O coordination bonds.

2. The composite material as described in claim 1, characterized in that: The ferrocene carboxylic acid ligand is ferroceneformic acid or ferroceneacetic acid.

3. The composite material as described in claim 1, characterized in that: The iron porphyrin carboxylic acid ligand is iron tetra(4-carboxyphenyl)porphyrin.

4. A method for preparing the composite material according to any one of claims 1-3, characterized in that, The composite material is prepared in one step by an in-situ modified solvothermal method, specifically including: adding ferrotetra(4-carboxyphenyl)porphyrin and zirconium salt ZrOCl2·8H2O to an organic solvent for mixing and dissolution, adding a regulator and ferrocene carboxylic acid, placing it in a closed reaction vessel for solvothermal reaction, and after the reaction, solid-liquid separation, washing, and drying are performed to obtain the composite material.

5. The preparation method according to claim 4, characterized in that: The organic solvent is any one of N,N-dimethylacetamide, N,N-dimethylformamide, and dimethyl sulfoxide.

6. The preparation method according to claim 4, characterized in that: The regulator is any one of benzoic acid, trifluoroacetic acid, glacial acetic acid, hydrochloric acid, and trifluoromethanesulfonic acid.

7. The preparation method according to claim 4, characterized in that: The mass ratio of the ferrocene carboxylic acid and ferrotetra(4-carboxyphenyl)porphyrin is 1:6-1.5:

1.

8. The preparation method according to claim 7, characterized in that: The mass ratio of ferrocene carboxylic acid to ferrotetra(4-carboxyphenyl)porphyrin is 1:

2.

9. The preparation method according to claim 4, characterized in that: The temperature of the solvothermal reaction is 100-140℃, and the reaction time is 12-36h.

10. The application of the composite material as described in any one of claims 1-3 in the photocatalytic reduction of CO2 to CO reaction.

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