A method of tuning the electrochemical properties of metal-organic framework thin films by plasma immersion

Abstract

The application belongs to the technical field of metal organic framework thin films, and particularly relates to a method for adjusting the electrochemical properties of a metal organic framework thin film through plasma immersion injection. The application is based on maintaining the porous network structure of the MOF thin film, and on-demand regulating the types and quantities of the metal ions stably connected in the MOF thin film, so as to realize the regulation of the electrochemical properties of the MOF thin film. The specific steps include: placing the MOF thin film synthesized on a substrate into a sample table of a plasma immersion injection device; loading metal target material into a target material chamber of the plasma immersion injection; setting an injection voltage and an injection time; and opening the device to inject the required ions into the MOF thin film, so as to realize the change of the types of the metal ions in the MOF thin film and the regulation of the electrochemical properties. The method is gas-phase regulation, and no organic solvent is involved in the whole process. The metal ions in the MOF thin film are regulated in one step, the rapid large-scale preparation is realized, and the method has universality and controllability.

Description

Technical Field

[0001] This invention belongs to the field of metal-organic framework thin film technology, and specifically relates to a method for regulating the electrochemical performance of metal-organic framework thin films. Background Technology

[0002] Metal-organic frameworks (MOFs) are a class of coordination polymers with periodic network structures formed by transition metal ions and organic ligands. They are characterized by large specific surface area, high porosity, high content of transition metal ions, and abundant unsaturated coordination sites. Chem. Rec. (2023, 23, e202300006) MOF films have been widely used in gas sensing, biosensing, electrochemical catalysis, gas separation, and drug delivery. In the fields of electrochemical sensing and catalysis, compared to MOF particles, MOF films have advantages such as uniform dispersion, sufficient exposure of active sites, and stable electronic conduction networks. Mater. Horiz. (2021, 8, 168) with better electrochemical performance.

[0003] However, the electrochemical sensing mechanism of MOFs depends on transition metal ions, and the sensing target and performance of MOFs correspond to the metal ions and structure of MOFs. Anal. Bioanal. Chem. 2023, 415, 2005-2023), which greatly limits the application of MOFs. Post-processing to control metal ions in MOFs has become an important way to expand their applications. The Pang Huan research group at Yangzhou University used ethanol to change the surface coordination mode of ZIF-67, achieving the insertion of Ni ions into Co-MOFs through complex control. Adv. Mater. 2023, 35, 2211523). However, this method is not universally applicable and is complex to operate. In addition, Lu et al. also studied the implantation of metal particles onto MOF films via physical vapor deposition methods such as sputtering (…). Electrochem. Commun. (2020, 114, 106715), but metals exist only in elemental form, which can improve sensitivity but cannot change electrochemical properties. Currently, there is no method to universally control metal ions in MOFs to regulate the electrochemical properties of MOF films. Summary of the Invention

[0004] The purpose of this invention is to provide a method for regulating metal ions in MOF thin films, thereby adjusting the electrochemical properties of MOF thin films. This method can control the types and quantities of metal ions connected by stable chemical bonds inside MOF thin films as needed, and achieve electrochemical sensing for a variety of target molecules.

[0005] The method for regulating the electrochemical properties of metal-organic framework (MOF) thin films via plasma immersion implantation provided by this invention involves using plasma immersion implantation to maintain the porous network structure of the MOF film while controlling the types and quantities of metal ions connected by stable chemical bonds within the MOF film as needed, thereby achieving the regulation of the MOF film's electrochemical properties. The specific steps are as follows:

[0006] (1) Place the MOF film synthesized on the substrate into the sample stage of the plasma immersion implantation device;

[0007] (2) The metal target is loaded into the target chamber of plasma immersion injection;

[0008] (3) Set the injection voltage and injection time;

[0009] (4) Turn on the equipment to inject the required ions into the MOF film, thereby changing the types of ions inside the MOF film and adjusting its electrochemical properties.

[0010] A schematic diagram of plasma immersion implantation on MOF thin films is shown below. Figure 1 As shown.

[0011] In step (1):

[0012] The substrate includes a two-dimensional planar substrate and a multi-level structure substrate;

[0013] The two-dimensional planar substrate includes a single-crystal silicon wafer, a silicon oxide wafer, and a flexible polymer planar substrate;

[0014] The multi-level structure substrates include high aspect ratio structure devices, fiber linear materials, and silicon array columnar substrates;

[0015] The synthesized MOF films include MOF films synthesized by gas-phase method and liquid-phase method;

[0016] The MOF thin film synthesized by the vapor phase method is a MOF thin film synthesized by first depositing a metal oxide thin film, then exposing it to the ligand vapor of the MOF, and then synthesizing the MOF thin film at a specific temperature.

[0017] The MOF thin films synthesized by the liquid phase method include MOF thin films synthesized by hydrothermal method, layer-by-layer deposition method, electro-driven synthesis method, and microwave-assisted method.

[0018] The MOFs mentioned include imidazole (ZIF), carboxylic acid, and phosphonic acid.

[0019] In step (2):

[0020] The plasma immersion implantation equipment is a device that can ionize the atoms of elements into charged ions, accelerate the charged ions in a strong electric field, and inject the ion beam into the surface of the material.

[0021] The metal target material is a high-purity metal target material, including Fe target, Co target, Ni target, Cu target, Zn target, Ge target, Ga target, In target, Sn target, and Ce target;

[0022] The injection voltage is 100 volts to 100 kilovolts; preferably, the injection voltage is 300 volts to 20 kilovolts, and more preferably, 500 volts to 10 kilovolts;

[0023] The injection time is from 1 second to 24 hours; preferably, the injection time is 5-200 minutes, and more preferably, 15-45 minutes.

[0024] This invention provides a method for controlling the internal metal ions of MOF thin films through plasma immersion implantation, thereby achieving the regulation of the electrochemical properties of MOF thin films. The ion implantation process does not disrupt the porous network structure of the MOF thin film, such as... Figure 2 SEM images of the thin film and Figure 3 The pore size distribution is shown in the diagram. The process of controlling MOF metal ions is solvent-free, achieving the ability to regulate the types of ions within the MOF while maintaining its porous network structure, thereby modulating its electrochemical properties. For example, implanting Co ions into a ZIF-4 film enables specific and sensitive sensing of H₂O₂ molecules, with a sensitivity reaching 2111 µm / m². -1 cm -2 ZIF-4 films themselves exhibit almost no electrochemical activity towards H2O2 molecules. However, by implanting Fe ions into the ZIF-4 film, specific and sensitive sensing of dopamine molecules can be achieved, with a sensitivity reaching 2475 µm / m². -1 cm -2 Furthermore, the ZIF-4 film itself has almost no electrochemical properties for dopamine molecules.

[0025] Compared with the prior art, the present invention has the following characteristics and positive effects.

[0026] (1) The method for adjusting the electrochemical properties of MOF thin films provided by the present invention is gas phase control, with no organic solvent involved in the whole process, thus avoiding the corrosion of the device by solvent and the residual solvent molecules in the MOF channels, which corrode the organic framework.

[0027] (2) The method provided by the present invention can achieve one-step control of metal ions in MOF thin films within the cavity of a plasma immersion injection device, enabling rapid large-scale preparation and compatibility with modern semiconductor manufacturing processes;

[0028] (3) The method provided by the present invention is applicable to the introduction of various metal ions into various types of MOF thin films synthesized on various substrates, and has strong universality;

[0029] (4) The method provided by this invention, by adjusting the implantation voltage and implantation time, can adapt to MOF films on various flexible or rigid substrates and can controllably adjust the number of implanted ions, thereby controllably adjusting the electrochemical properties of the MOF film, such as... Figure 4 As shown. Attached Figure Description

[0030] Figure 1 A schematic diagram of plasma immersion implantation on a MOF (ZIF-4) thin film.

[0031] Figure 2 SEM images of MOF (ZIF-4) films before and after plasma immersion implantation.

[0032] Figure 3 The image shows the pore size distribution of the MOF (ZIF-4) thin film before and after plasma immersion implantation.

[0033] Figure 4 This represents the relationship between implantation time and the number of implanted ions on the MOF film.

[0034] Figure 5 Electrochemical sensing of 1 mM H2O2 before and after Co ion implantation on MOF (ZIF-4) thin films.

[0035] Figure 6 Electrochemical sensing of different concentrations of dopamine molecules before and after Fe ion implantation on MOF (ZIF-4) films.

[0036] Figure 7 Electrochemical sensing of different concentrations of glucose molecules before and after Ni ion implantation on MOF (ZIF-4) films.

[0037] The numbers in the figure are: 1 for metal ions, 2 for plasma immersion implantation, and 3 for MOF thin films. Implementation

[0038] The present invention will be further described below with reference to the embodiments and accompanying drawings. Example

[0039] (1) Deposit a ZnO layer on a single crystal silicon wafer, place it in a CVD or tube furnace chamber, put the imidazole ligand in a crucible under the silicon wafer, and synthesize a MOF thin film in the gas phase at 120 degrees Celsius in a N2 atmosphere. This film is called ZIF-4 thin film.

[0040] (2) Place the silicon wafer with the ZIF-4 thin film grown on the sample stage of the plasma immersion implantation equipment, and select a high-purity Co target as the target material;

[0041] (3) Set the injection voltage to 500 volts and the injection time to 30 minutes;

[0042] (4) Turn on the ion implantation equipment and wait for the ion implantation to complete. Example

[0043] Ion implantation was performed on the MOF thin film according to the method of Example 1, except that the substrate of the MOF thin film was an Ecoflex flexible substrate.

[0044] ZIF-4 thin films were grown in the vapor phase on Ecoflex flexible substrates, and then Co ions were implanted as in Example 1. The electrochemical sensing performance for 1 mM H₂O₂ molecules was then tested. The results are as follows: Figure 5 As shown, the original ZIF-4 film exhibits almost no electrochemical activity towards H2O2 molecules, while the implantation of Co ions significantly enhances the electrochemical response current to H2O2 molecules, achieving a sensitivity of 2111 µm / m. -1 cm -2 . Example

[0045] Ion implantation was performed on MOF films according to the method in Example 1, except that the MOF films were synthesized using a liquid-phase solvothermal method. The specific synthesis steps of the MOF films (taking ZIF-67 films as an example) are as follows:

[0046] A ZnO layer was deposited on a single-crystal silicon wafer; Co(NO3)2·6H2O (1.45 g) was dissolved in a mixture of methanol (40 mL) and ethanol (40 mL) to form solution A; dimethylimidazole (1.65 g) was dissolved in a mixture of methanol (40 mL) and ethanol (40 mL) to form solution B; the silicon wafer with the deposited ZnO layer was then placed in a beaker containing solution A; the beaker was sealed at 90 °C for 24 hours; after cooling to room temperature, solution B was added, and the mixture was aged at room temperature for another 24 hours; after that, the silicon wafer was removed and washed with ethanol; the sample was then vacuum dried at 60 °C for 12 hours to form a uniform and dense ZIF-67 film on the silicon wafer. Example

[0047] Ion implantation was performed on the MOF film according to the method in Example 1, except that the MOF film type used was a carboxylic acid MOF-5 film.

[0048] The specific steps for the vapor-phase synthesis of MOF-5 are as follows: deposit a ZnO layer on a single-crystal silicon wafer, place it in a CVD or tube furnace chamber, place the terephthalic acid ligand in a crucible below the silicon wafer, and synthesize a ZIF-4 thin film in the vapor phase at 130 degrees Celsius in an N2 atmosphere. Example

[0049] Ion immersion implantation was performed on the MOF film according to the method of Example 1, except that a high-purity Fe target was used to implant Fe ions into the MOF film to change its electrochemical properties.

[0050] like Figure 6 As shown, after Fe ions are implanted into the gas-phase synthesized ZIF-4 thin film via plasma immersion implantation, specific and sensitive sensing of dopamine molecules can be achieved. The MOF thin film with Fe ion implantation for 30 minutes can achieve a sensitivity of 2475 µm / m² to dopamine. -1 cm -2 The original ZIF-4 film has almost no electrochemical properties for dopamine molecules. Example

[0051] Ion implantation was performed on the MOF film according to the method in Example 1, except that a high-purity Ni target was used as the target material, and Ni ions were implanted into the MOF film to change its electrochemical properties.

[0052] like Figure 7 As shown, after Ni ions are implanted into a vapor-synthesized ZIF-4 thin film via plasma immersion implantation, specific and sensitive sensing of glucose molecules can be achieved. The MOF film with Ni ion implantation for 30 minutes can achieve a glucose sensitivity of 1669 µm / m. -1 cm -2 Furthermore, the original ZIF-4 film has almost no electrochemical properties for glucose molecules. Example

[0053] Ion implantation was performed on the MOF film according to the method of Example 1, except that the implantation voltage was adjusted to 10 kV, thus changing the ion implantation energy.

[0054] A 10 kV injection voltage is suitable for substrates such as silicon wafers and titanium alloys that can withstand high energy, while flexible polymer substrates require a lower injection voltage to prevent damage to the thin film. Example

[0055] Ion implantation was performed on the MOF film according to the method of Example 1, except that the ion implantation time was adjusted to 15 minutes and the amount of implanted ions was changed.

[0056] The ZIF-4 film with a Co ion implantation depth of 15 minutes exhibited a sensitivity of 1449 µAmM to H2O2 molecules. -1 cm -2 Therefore, the electrochemical performance of MOF films can be adjusted by controlling the ion immersion implantation amount (implantation time).

[0057] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. For example, according to the preparation methods proposed in the above embodiments, different types of metal ions can be implanted onto different types of MOF films, and different implantation voltages and implantation times can be adjusted. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for adjusting the electrochemical properties of metal-organic framework thin films by plasma immersion implantation, characterized in that, The electrochemical properties of MOF films are controlled by plasma immersion implantation, which maintains the porous network structure of the MOF film while adjusting the types and quantities of metal ions connected by stable chemical bonds within the MOF film as needed. The specific steps are as follows: (1) Place the MOF film synthesized on the substrate into the sample stage of the plasma immersion implantation device; (2) The metal target is loaded into the target chamber of plasma immersion injection; (3) Set the injection voltage and injection time; (4) Turn on the equipment to inject the required ions into the MOF film to change the type of metal ions inside the MOF film and adjust its electrochemical properties; The metal target is a high-purity metal target, selected from Fe target, Co target, Ni target, Cu target, Zn target, Ge target, Ga target, In target, Sn target, and Ce target; The injection voltage is 500 volts to 10 kilovolts; The injection time is 15-45 minutes.

2. The method according to claim 1, characterized in that, In step (1): The substrate is a two-dimensional planar substrate or a multi-level structure substrate; wherein: The two-dimensional planar substrate is a single-crystal silicon wafer, a silicon oxide wafer, or a flexible polymer planar substrate; The multi-level structure substrate is a high aspect ratio structure device, a fiber linear material, or a silicon array columnar substrate.

3. The method according to claim 1, characterized in that, In step (1): The synthesized MOF film is a MOF film synthesized by a gas-phase method or a liquid-phase method; wherein: The MOF thin film synthesized by the vapor phase method is a MOF thin film synthesized by first depositing a metal oxide thin film, then exposing it to the ligand vapor of the MOF, and then synthesizing the MOF thin film at a specific temperature. The MOF thin film synthesized by the liquid phase method is a MOF thin film synthesized by hydrothermal method, layer-by-layer deposition method, electro-driven synthesis method or microwave-assisted method. The MOF is selected from imidazoles, carboxylic acids, and phosphonates.

4. The method according to claim 1, characterized in that, In step (2): The plasma immersion implantation device is a device that can ionize element atoms into charged ions, accelerate the charged ions in a strong electric field, and inject the ion beam into the surface of a material.

Images