Preparation method of a high-efficiency photocatalytic pure formic acid decomposition hydrogen production catalyst

Abstract

The present invention belongs to the technical field of photocatalytic formic acid decomposition for hydrogen production, and provides a high-efficiency photocatalytic pure formic acid decomposition hydrogen production catalyst and its preparation method, mainly related to a preparation method of a non-precious metal composite photocatalytic material Cu@Bpt‑CTF based on a covalent triazine organic skeleton, including: first, a triazine-based organic skeleton material Bpt‑CTF containing a thiourea functional group is prepared by a molten salt catalysis method; secondly, Cu(NO3)2 is applied as a Cu source, and the Bpt‑CTF material is coordinated and anchored to obtain a covalent triazine organic skeleton material Bpt‑CTF‑Cu; finally, a non-precious metal copper-based triazine organic skeleton material catalyst Cu@Bpt‑CTF is prepared in situ under pure formic acid vapor and visible light irradiation. The reaction conditions of the present invention are mild, and the synthesis process is simple and easy to implement. It provides a high-efficiency, highly selective photocatalytic pure formic acid (additive-free, anhydrous) hydrogen production catalyst and its preparation process (CO is only 0.002%). The present application adopts a photocatalytic system, which can achieve the effect of utilizing solar energy and reasonable industrial operation costs, and has good application prospects.

Description

Technical Field

[0001] The invention belongs to the field of photocatalytic formic acid decomposition to produce hydrogen, and particularly relates to a method for preparing a catalyst for photocatalytic pure formic acid decomposition to produce hydrogen. Background Art

[0002] Currently, the global energy situation is extremely severe, with energy shortages and environmental pollution having a huge impact on human life. In the current energy sector, clean, efficient, and sustainable energy has become a hot topic of research, with the development of hydrogen energy undoubtedly being the focus. However, safe and efficient hydrogen storage technology is a major bottleneck in the field of hydrogen energy applications. Liquid organic small molecules (LOHCs) are a new type of hydrogen storage material with great development potential. Among them, formic acid is an ideal hydrogen storage material due to its abundant resources, low toxicity, non-flammability, and good stability. In addition, the decomposition of formic acid can produce only H2 and CO2, and CO2 can be hydrogenated to produce formic acid, thus realizing the hydrogen storage process.

[0003] As a subclass of covalent organic framework materials, covalent triazine framework materials (CTFs) are expected to become a new class of high-performance organic semiconductor porous materials due to their high catalytic activity, high selectivity, high stability, high quantum yield, easily adjustable band structure, and finely tuned isolated active sites. Two-dimensional covalent organic frameworks (CTFs) have excellent crystal structures and abundant pores, which provide excellent conditions for the adsorption, diffusion, and reaction of small molecules. At the same time, the π-π stacked aromatic functional groups can promote the separation, diffusion, and migration of photogenerated carriers. Therefore, it is crucial to construct a photocatalytic material based on CTFs by introducing catalytic active sites on their surface, combining high specific surface area, porous structure, photoresponsiveness, and high activity. Summary of the Invention

[0004] The object of the present invention is to provide a method for preparing a covalent triazine organic framework material Cu@Bpt-CTF, which has excellent photocatalytic formic acid decomposition and hydrogen production performance in a gas-solid phase reaction mode.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A method for preparing a covalent triazine organic framework material Cu@Bpt-CTF comprises the following steps:

[0007] Step 1: Using 1,3-bis(4-cyanophenyl)thiourea (Bpt) as a monomer, a molten salt catalysis method is used to prepare a triazine-based 2D-CTF material containing a thiourea functional group (Bpt-CTF), specifically:

[0008] Step 1.1: Weigh a certain amount of sodium chloride: potassium chloride: zinc chloride (mass ratio 1:2:5-1:2:7) and Bpt monomer;

[0009] Step 1.2: The solid weighed in step 1.1 was mixed and evenly ground in an anhydrous and oxygen-free glove box for 25 minutes to obtain a uniform white powder solid;

[0010] Step 1.3: Place the product obtained in step 1.2 into a Pyrex tube, evacuate the tube, and flame seal the tube;

[0011] Step 1.4: Heat the Pyrex tube prepared in step 1.3 at 200-300°C at 5°C / min. -1 The mixture was calcined for 24 h at a heating rate and then cooled to room temperature;

[0012] Step 1.5: The product obtained in step 1.4 was washed with trifluoromethanesulfonic acid and ultrasonically dispersed in deionized water;

[0013] Step 1.6: Freeze-dry the product from step 1.5 at 0°C for 24 hours to obtain a triazine-based Bpt-CTF material containing a thiourea functional group;

[0014] Step 2: Using Cu(NO3)2 as a Cu source, the Bpt-CTF material is coordinated and anchored to obtain a metal-anchored covalent triazine organic framework material Bpt-CTF-Cu, specifically:

[0015] Step 2.1: Weigh Cu(NO3)2 and dissolve it in deionized water in a round-bottom flask and sonicate until a clear solution is obtained.

[0016] Step 2.2: Add the triazine-based 2D-CTF material containing thiourea functional groups (Bpt-CTF) prepared in step 1 to the round-bottom flask in step 2.1 and perform ultrasonic treatment to ensure that the Bpt-CTF is completely dispersed;

[0017] Step 2.3: Stir the product from step 2.2 at 50°C for 24 hours;

[0018] Step 2.4: Filter the product after the reaction in step 2.3;

[0019] Step 2.5: The product obtained in step 2.4 is dried to obtain Bpt-CTF-Cu.

[0020] Step 3: In a sealed photocatalytic container, a trace amount of formic acid (20-60 μL) is added to the obtained metal-anchored covalent triazine organic framework material Bpt-CTF-Cu. The solid catalyst is then irradiated with visible light for 1 hour. The solid catalyst is then washed with deionized water, filtered, and vacuum-dried to obtain the photocatalytic material Cu@Bpt-CTF.

[0021] Furthermore, a method for preparing a covalent triazine organic framework photocatalytic material Cu@Bpt-CTF is provided, characterized in that the proportion of the molten salt used in the molten salt catalytic polymerization process in step 1.1 and the mixing ratio with the thiourea monomer Bpt and the grinding process in step 1.2 need to be carried out in an anhydrous and oxygen-free glove box.

[0022] Furthermore, a method for preparing a covalent triazine organic framework photocatalytic material Cu@Bpt-CTF is characterized in that, in step 1.4, the catalyst is heated in a Pyrex tube at a temperature of 5°C·min in the range of 200-300°C. -1 Calcination is carried out at a heating rate of 6-24h.

[0023] Furthermore, a method for preparing a covalent triazine organic framework photocatalytic material Cu@Bpt-CTF is provided, characterized in that the metal copper atom loading process in steps 2.2-2.5 needs to be stirred at 50°C for 24 hours under nitrogen protection and filtered, washed and dried.

[0024] Furthermore, the method for preparing a covalent triazine organic framework photocatalytic material Cu@Bpt-CTF is characterized in that the step 3 is a process for preparing the Cu catalytic site CTF photocatalytic material by in-situ photocatalysis under a formic acid atmosphere.

[0025] Compared with the prior art, the present invention can achieve the following technical effects:

[0026] 1) The preparation method provided by the present invention successfully synthesized a triazine covalent organic framework material Bpt-CTF containing a thiourea functional group using a simple molten salt catalysis method. The reaction conditions are mild and the synthesis process is simple and easy to implement;

[0027] 2) Compared with traditional covalent triazine photocatalytic materials, the thiourea-triazine-based two-dimensional covalent organic framework material of the present invention has a polar structure that allows the separation of photogenerated carriers to generate holes and electrons. The holes move to the thiourea group and the electrons move to the triazine group. This can more easily achieve the separation of electrons and holes in the plane, thereby improving the efficiency of the catalyst in photolysis of formic acid to produce hydrogen. It can be used as a new type of high-efficiency photocatalytic hydrogen production material;

[0028] 3) The covalent triazine organic framework photocatalytic material Cu@Bpt-CTF obtained by the preparation method provided by the present invention can simply construct a photocatalytic composite material with multivalent Cu sites.

[0029] 4) Compared with traditional noble metal doping, the use of copper metal in the present invention is less expensive;

[0030] 5) The preparation method provided by the present invention uses Cu(NO3)2 as the Cu source to functionally modify the organic framework material CTF, in which the copper catalytic center has a dual role: an electron acceptor divalent copper ion promotes photoelectron transfer and is used to reduce proton hydrogen ions to hydrogen, and a hole acceptor cuprous ion selectively oxidizes bicarbonate ions to carbon dioxide, thereby completing the entire photocatalytic formic acid decomposition and hydrogen production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a process flow chart of a method for preparing a high-efficiency photocatalytic pure formic acid decomposition hydrogen production catalyst of the present invention;

[0032] Figure 2 This is a schematic structural diagram of a triazine-based 2D-CTF material Bpt-CTF containing a thiourea functional group prepared in accordance with an embodiment of a method for preparing a high-efficiency photocatalytic pure formic acid decomposition catalyst for hydrogen production of the present invention;

[0033] Figure 3 XRD patterns of a triazine-based 2D-CTF material Bpt-CTF containing a thiourea functional group and a covalent triazine organic framework material Bpt-CTF-Cu containing a metal anchor prepared in accordance with an embodiment of a method for preparing a high-efficiency photocatalytic pure formic acid decomposition catalyst for hydrogen production of the present invention;

[0034] Figure 4 This is an infrared image of a triazine-based 2D-CTF material Bpt-CTF containing a thiourea functional group and a covalent triazine organic framework material Bpt-CTF-Cu containing a metal anchor, prepared in accordance with an embodiment of a method for preparing a high-efficiency photocatalytic pure formic acid decomposition catalyst for hydrogen production of the present invention;

[0035] Figure 5 This is an SEM image of a triazine-based 2D-CTF material Bpt-CTF containing a thiourea functional group and a covalent triazine organic framework material Bpt-CTF-Cu containing a metal anchor, prepared in accordance with an embodiment of a method for preparing a high-efficiency photocatalytic pure formic acid decomposition catalyst for hydrogen production of the present invention;

[0036] Figure 6 This is a method for preparing a highly efficient photocatalytic catalyst for hydrogen production by decomposing pure formic acid. The XPS graphs of the prepared triazine-based 2D-CTF material Bpt-CTF containing thiourea functional groups and the covalent triazine organic framework material Bpt-CTF-Cu containing metal anchors are shown in the example.

[0037] Figure 7 The present invention is a method for preparing a highly efficient photocatalytic catalyst for decomposing pure formic acid to produce hydrogen. The prepared photocatalytic material Cu@Bpt-CTF shows a graph showing the amount of hydrogen generated as a function of reaction time and a graph showing the hydrogen production rate at 160 min. DETAILED DESCRIPTION

[0038] Below in conjunction with the accompanying drawings in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is clearly and completely described. Obviously, the embodiment described is only a part of the present invention, rather than all embodiments. Based on the embodiment in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work premise all fall within the scope of protection of the present invention. Unless otherwise specified, all goods or reagents in the present invention are purchased through market channels.

[0039] Example

[0040] A method for preparing a covalent triazine organic framework material Cu@Bpt-CTF, comprising the following steps:

[0041] Step 1: Using 1,3-bis(4-cyanophenyl)thiourea (Bpt) as a monomer, a molten salt catalysis method is used to prepare a triazine-based 2D-CTF material containing a thiourea functional group (Bpt-CTF), specifically:

[0042] Step 1.1: Weigh 100 mg of sodium chloride, 200 mg of potassium chloride, 700 mg of zinc chloride, and 169 mg of Bpt monomer;

[0043] Step 1.2: The solid weighed in step 1.1 was mixed and evenly ground in an anhydrous and oxygen-free glove box for 25 minutes to obtain a uniform white powder solid;

[0044] Step 1.3: Place the product obtained in step 1.2 into a 10 ml Pyrex tube, evacuate the tube, and flame seal the tube.

[0045] Step 1.4: Heat the Pyrex tube prepared in step 1.3 at 200-300°C at 5°C / min. -1 The mixture was calcined for 24 h at a heating rate and then cooled to room temperature;

[0046] Step 1.5: The product obtained in step 1.4 was washed with trifluoromethanesulfonic acid and ultrasonically dispersed in deionized water;

[0047] Step 1.6: Freeze-dry the product from step 1.5 at 0°C for 24 hours to obtain a triazine-based Bpt-CTF material containing a thiourea functional group;

[0048] Step 2: Using Cu(NO3)2 as a Cu source, the Bpt-CTF material is coordinated and anchored to obtain a metal-anchored covalent triazine organic framework material Bpt-CTF-Cu, specifically:

[0049] Step 2.1: Weigh 100 mg of Cu(NO3)2 and dissolve it in 50 ml of deionized water in a round-bottom flask. Ultrasonicate until a clear solution is obtained.

[0050] Step 2.2: Add 100 mg of the triazine-based 2D-CTF material containing thiourea functional groups (Bpt-CTF) prepared in Step 1 to the round-bottom flask in Step 2.1 and sonicate to ensure complete dispersion of the Bpt-CTF.

[0051] Step 2.3: Stir the product from step 2.2 at 50°C for 24 hours;

[0052] Step 2.4: Filter the product after the reaction in step 2.3;

[0053] Step 2.5: The product obtained in step 2.4 is dried to obtain Bpt-CTF-Cu.

[0054] Step 3: In a sealed photocatalytic container, 10 μl of formic acid is added to the obtained metal-anchored covalent triazine organic framework material Bpt-CTF-Cu, and then the solid catalyst is irradiated with visible light for 1 hour, and then washed with deionized water, filtered and vacuum dried to obtain the photocatalytic material Cu@Bpt-CTF.

[0055] Test Example 1

[0056] 10 mg of photocatalyst material was loaded into the reactor, and 20 μl of formic acid was manually injected through a microsyringe. After the reaction was confirmed to be complete under dark conditions, a 300 W argon lamp with a 420 nm optical filter was turned on to continue the photocatalytic reaction, ensuring that the reaction system in the reactor was airtight. The photocatalytic decomposition products of formic acid were analyzed using a GC equipped with a TCD, FID detector, and a chromatographic column.

[0057] Test Example 2

[0058] 10 mg of photocatalyst material was loaded into the reactor, and 40 μl of formic acid was manually injected through a microsyringe. After the reaction was confirmed to be complete under dark conditions, a 300 W argon lamp with a 420 nm optical filter was turned on to continue the photocatalytic reaction, ensuring that the reaction system in the reactor was airtight. The photocatalytic decomposition products of formic acid were analyzed using a GC equipped with a TCD, FID detector, and a chromatographic column.

[0059] Test Example 3

[0060] 10 mg of photocatalyst material was loaded into the reactor, and 60 μl of formic acid was manually injected through a microsyringe. After the reaction was confirmed to be complete under dark conditions, a 300 W argon lamp with a 420 nm optical filter was turned on to continue the photocatalytic reaction, ensuring that the reaction system in the reactor was airtight. The photocatalytic decomposition products of formic acid were analyzed using a GC equipped with a TCD, FID detector, and a chromatographic column.

[0061] The test results are shown in Table 1:

[0062]

[0063] As can be seen from Table 1, the triazine-based two-dimensional covalent organic framework material (Cu@Bpt-CTF) loaded with copper catalytic sites prepared by the present invention can well achieve the technical effect of hydrogen production by decomposition of formic acid. Taking Test Example 1 of the embodiment as an example, as time increases, the hydrogen production first increases and then stabilizes. Taking the test example of the embodiment as an example, as the amount of formic acid increases, the catalytic performance is enhanced, and the hydrogen production rate can reach 23.92mmol·g after 160min. -1 ·h -1 .

[0064] The present invention illustrates the technical concept of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned embodiments, that is, it does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of individual raw materials (Cu and other triazine organic framework materials) of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the scope of protection and disclosure of the present invention.

[0065] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

Claims

1. A method for preparing a covalent triazine organic framework photocatalytic material Cu@Bpt-CTF, characterized in that: The following steps are involved: Step 1: Using 1,3-bis(4-cyanophenyl)thiourea Bpt as a monomer, a molten salt catalysis method is used to prepare a triazine-based 2D-CTF material Bpt-CTF containing a thiourea functional group, specifically: Step 1.1: Weigh sodium chloride, potassium chloride, and zinc chloride in a mass ratio of 1:2:5 to 1:2:7, and then weigh a certain amount of Bpt monomer; Step 1.2: The solid weighed in step 1.1 was mixed and evenly ground in an anhydrous and oxygen-free glove box for 25 minutes to obtain a uniform white powder solid; Step 1.3: Place the product obtained in step 1.2 into a Pyrex tube, evacuate the tube, and flame seal it; Step 1.4: Heat the Pyrex tube prepared in step 1.3 at 5°C / min. -1 The temperature was raised at a heating rate of 100-200 ° C, calcined at 200-300 ° C for 24 h, and then cooled to room temperature; Step 1.5: The product obtained in step 1.4 was washed with trifluoromethanesulfonic acid and ultrasonically dispersed in deionized water; Step 1.6: Freeze-dry the product from step 1.5 at 0°C for 24 hours to obtain a triazine-based Bpt-CTF material containing a thiourea functional group; Step 2: Using Cu(NO3)2 as a Cu source, the Bpt-CTF material is coordinated and anchored to obtain a metal-anchored covalent triazine organic framework material Bpt-CTF-Cu, specifically: Step 2.1: Weigh Cu(NO3)2 and dissolve it in deionized water in a round-bottom flask and sonicate until a clear solution is obtained. Step 2.2: Add the triazine-based 2D-CTF material containing thiourea functional groups prepared in step 1, Bpt-CTF, to the round-bottom flask prepared in step 2.1 and perform ultrasonic treatment to ensure that Bpt-CTF is completely dispersed; Step 2.3: Stir the product from step 2.2 at 50°C for 24 hours; Step 2.4: Filter the product after the reaction in step 2.3; Step 2.5: Dry the product obtained in step 2.4 to obtain Bpt-CTF-Cu; Step 3: In a sealed photocatalytic container, a trace amount of formic acid is added to the obtained metal-anchored covalent triazine organic framework material Bpt-CTF-Cu. After visible light irradiation for 1 hour, the material is washed with deionized water, filtered, and vacuum-dried to obtain the photocatalytic material Cu@Bpt-CTF.

2. The method for preparing a covalent triazine organic framework photocatalytic material Cu@Bpt-CTF according to claim 1, characterized in that: Steps 2.2 and 2.3 were performed under nitrogen protection.

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