Methylated covalent triazine polymers and methods of making and using the same
The preparation of methylated covalent triazine polymers by catalyzing the reaction of dimethylimide compounds with acid anhydrides solves the problems of narrow light absorption and slow charge transfer in existing photocatalytic materials, achieving highly efficient photocatalytic CO2 reduction and expanding the application potential of photocatalysts.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- LANZHOU INSTITUTE OF CHEMICAL PHYSICS CHINESE ACADEMY OF SCIENCES
- Filing Date
- 2023-09-26
- Publication Date
- 2026-06-23
AI Technical Summary
Existing photocatalytic materials suffer from narrow light absorption, slow charge transfer, and limited catalytic active sites during photocatalytic CO2 reduction, leading to photogenerated charge recombination problems and limiting their photocatalytic efficiency.
Methylated covalent triazine polymers were prepared by using anhydride catalysts to catalyze the reaction of dimethylimide compounds. By introducing methyl groups in situ onto the triazine backbone, the preparation process was simplified, the light absorption range was expanded, and the photogenerated electron transport efficiency was improved.
The prepared methylated covalent triazine polymer exhibits high CO2 adsorption performance and high yield under visible light excitation, as well as CO selectivity. Furthermore, it demonstrates good stability and minimal activity loss in the photoreduction of CO2 under gas-solid mode.
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Figure CN119708476B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of organic compounds, and particularly relates to a methylated covalent triazine polymer and a preparation method and application thereof. BACKGROUND
[0002] Carbon dioxide (CO2) is not only a greenhouse gas, but also a kind of carbon resource with abundant reserves and low cost. Reasonable utilization of CO2 is one of the effective ways to achieve the double carbon goal. The current serious energy crisis and environmental pollution problem has prompted more and more attention to focus on the thermal chemical, biological, electrochemical or photocatalytic conversion of CO2 to prepare high-value carbon-containing chemicals or fuels. Utilizing solar energy for artificial photosynthesis and photocatalytic conversion of CO2 is considered as a potential way.
[0003] The essence of photocatalytic CO2 reduction reaction (CO2RR) is a redox process under light induction, which mainly includes two processes: (1) adsorption of CO2 molecules by the reaction sites of photocatalytic materials; (2) redox process between the adsorbed CO2 and photo-generated electrons-holes. Therefore, improving the light absorption efficiency of photocatalytic materials, enhancing their adsorption and activation ability for CO2, and improving the separation efficiency of photo-generated electrons-holes are the key factors for constructing high-efficiency photocatalytic catalysts. However, the current developed catalysts are limited by narrow light absorption, slow charge transfer and limited catalytic active sites, etc., which leads to serious photo-generated charge recombination problem, and further causes their photocatalytic efficiency to be obviously limited. Therefore, developing high-efficiency, low-cost and high-stability photocatalysts is a great challenge to improve the efficiency of photocatalytic reduction of carbon dioxide.
[0004] In recent years, well-ordered crystalline covalent organic frameworks (COFs) have been regarded as a new type of organic semiconductor polymer material due to their π-conjugated skeleton and the ease of tunable and functionalized pore structure, showing great application potential in the artificial synthesis of photocatalysis. Among them, crystalline covalent triazine frameworks (CTFs) composed of triazine groups linked together with excellent light absorption capabilities have attracted widespread research attention. Their excellent organic semiconductor properties have led to their widespread application in various photocatalytic processes, such as water splitting to produce hydrogen and heterogeneous organic reactions. Some reported triazine organic polymer materials have shown photocatalytic activity comparable to or even better than inorganic semiconductors in hydrolysis reactions. However, due to band mismatch, they cannot meet high overpotentials, limiting the application of triazine polymers in photocatalytic CO2 conversion. CTFs utilize covalent chemical bonds to link triazine and other organic structural units at the molecular scale, thereby forming periodically ordered framework materials. For example, crystalline CTFs can be prepared by high-temperature (low-temperature) self-condensation polymerization of aromatic cyano groups under Lewis acid (Brown acid) catalysis. Additionally, the condensation polymerization between aromatic aldehydes / amines and dimethylamidine also provides an important route for creating crystalline CTFs. However, it should be noted that all of the above preparation methods have a significant drawback: it is difficult to easily functionalize the framework structure of the prepared CTFs. Typically, specific molecular structural design of the organic building blocks of the CTFs is required to achieve secondary modification or control of the pore structure. However, the multi-step and complex preparation process often hinders its further application in artificial photocatalysis. Therefore, providing a simple method for preparing functionalized triazine polymers and using them for carbon dioxide reduction is an urgent problem to be solved. Summary of the Invention
[0005] The main objective of this invention is to provide a methylated covalent triazine polymer, its preparation method, and its application, in order to overcome the shortcomings of the prior art.
[0006] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:
[0007] This invention provides a method for preparing a methylated covalent triazine polymer, comprising: reacting a dimethyl imipene compound in the presence of at least an acid anhydride catalyst to obtain a methylated covalent triazine polymer.
[0008] The present invention also provides methylated covalent triazine polymers prepared by the aforementioned preparation method.
[0009] This invention also provides a methylated covalent triazine polymer, the methylated covalent triazine polymer comprising a plurality of repeating structural units, the repeating structural units having a structure as shown in formula (II):
[0010]
[0011] Where n = 1 to 4, and the dashed lines represent the bond connection positions.
[0012] The embodiments of the present invention also provide the use of the aforementioned methylated covalent triazine polymer in the preparation of organic semiconductor materials or in the photocatalytic reduction of carbon dioxide.
[0013] This invention also provides an organic semiconductor material comprising at least the aforementioned methylated covalent triazine polymer.
[0014] This invention also provides a method for photocatalytic reduction of carbon dioxide, comprising:
[0015] Carbon dioxide is introduced into a reaction device equipped with a photocatalyst and subjected to a photocatalytic reaction under visible light irradiation, thereby reducing carbon dioxide to carbon monoxide; wherein the photocatalyst includes the aforementioned methylated covalent triazine polymer.
[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0017] (1) The methylated covalent triazine polymer prepared by this invention has the characteristics of wide light absorption range, high stability, high CO2 adsorption performance and good cycle performance; at the same time, the CO2 adsorption capacity of the methylated covalent triazine polymer in this invention reaches 2.0 mmol·g -1 The introduced methyl structure extends its light absorption range to 800 nm. Under visible light excitation, the methyl-modified covalent triazine framework catalytic system showed no significant activity loss in the photoreduction of CO2 in gas-solid mode for more than 4 rounds. Under test conditions without metals, photosensitizers or sacrificial reagents, it achieved high yield and 100% CO selectivity.
[0018] (2) This invention is the first to use an anhydride catalyst to catalyze the cyclization of methylammonium compounds to prepare methylated covalent triazine polymers. The preparation process is simple and the reaction conditions such as temperature and acid-base environment are relatively mild, which expands the synthesis route of covalent triazine polymers. It is very different from the traditional covalent triazine polymer synthesis method. It can synthesize triazine skeletons with functional methyl groups in situ in one step.
[0019] (3) This invention provides a method for synthesizing large quantities of methylated covalent triazine polymers, which has good scalability to reactants, and the methylated covalent triazine polymers prepared have good absorption in the visible light range and good photocatalytic reduction of carbon dioxide. Attached Figure Description
[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0021] Figure 1 This is a reaction mechanism diagram of a typical embodiment of the present invention for preparing a methyl-modified triazine group structure;
[0022] Figure 2 The infrared spectra of CTFs of dimethyl phthalimide monomer terephthalamide hydrochloride, methyl-modified covalent triazine polymer, and covalent triazine polymer materials synthesized by conventional methods in Example 1 of this invention are shown.
[0023] Figure 3 These are solid-state carbon NMR spectra of CTF, methyl-CTF-1, and methyl-CTF-2 prepared in Examples 1-3 of this invention.
[0024] Figures 4a-4b This is a catalytic performance diagram of a methyl-modified covalent triazine polymer in a typical embodiment of the present invention;
[0025] Figure 5 This is a schematic diagram illustrating the preparation of a methylated covalent triazine polymer in a typical embodiment of the present invention. Detailed Implementation
[0026] In view of the deficiencies of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention, which is mainly formed by the condensation of dimethylimide compounds into rings under the catalysis of acid anhydrides, and the in-situ introduction of methyl groups on the triazine skeleton, thereby effectively regulating the CTF skeleton, shortening the photogenerated electron transport distance between the methyl-modified CTF and CO2, and thus improving the photocatalytic efficiency.
[0027] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0028] Specifically, as one aspect of the technical solution of this invention, a method for preparing a methylated covalent triazine polymer includes:
[0029] Methylated covalent triazine polymers can be prepared by reacting dimethylimidides in the presence of an anhydride catalyst.
[0030] The synthesis method of the methylated covalent triazine polymer in this invention is simple, requiring only heating and stirring under nitrogen protection, without the need for high-temperature tube sealing. A schematic diagram of the reaction of the methylated covalent triazine polymer is shown below. Figure 5 As shown.
[0031] In some preferred embodiments, the preparation method specifically includes: mixing a dimethyl imidide compound, an acid anhydride catalyst, and an organic solvent under a protective atmosphere and reacting them at a first temperature to form an intermediate; then heating the intermediate to a second temperature and continuing the reaction to obtain a methylated covalent triazine polymer; wherein the second temperature is higher than the first temperature.
[0032] Furthermore, the dimethylimidide compound has a structure as shown in formula (I):
[0033]
[0034] Where n = 1 to 4.
[0035] Furthermore, the anhydride catalyst includes any one or more combinations of trifluoromethanesulfonic anhydride, benzoic anhydride, acetic anhydride, and trifluoroacetic anhydride, and is not limited thereto.
[0036] Furthermore, the organic solvent is an anhydrous organic solvent, which includes any one or more combinations of anhydrous dioxane, anhydrous trimethylbenzene, o-dichlorobenzene, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, anhydrous toluene, anhydrous methanol, and N-methylpyrrolidone, and is not limited thereto.
[0037] Furthermore, the first temperature is 30–130°C.
[0038] Furthermore, the reaction time at the first temperature is 1 to 5 days.
[0039] Furthermore, the second temperature is 130–200°C.
[0040] Furthermore, the reaction time at the first temperature is 1 to 7 days.
[0041] Furthermore, the molar ratio of the amine functional group to the acid anhydride catalyst in the dimethyl sulfide compound is 1:(1-100).
[0042] Furthermore, the preparation method further includes: after the reaction is completed, purifying and extracting the obtained product.
[0043] Specifically, the methyl-modified covalent triazine polymer was purified and extracted using organic solvents and water, respectively. After obtaining the covalent triazine polymer, organic solvents were added sequentially to remove small molecule organic compound impurities and acetic anhydride impurities. The organic solvents included N,N-dimethylformamide, dichloromethane, methanol, and ethanol.
[0044] In some more specific embodiments, the method for preparing the methylated covalent triazine polymer includes:
[0045] Under nitrogen protection, a series of dimethylimidides and anhydride catalysts are mixed and dissolved in an anhydrous organic solvent and mixed evenly to obtain a reactant mixture solution. Under nitrogen and a first temperature, the reactant mixture solution is stirred and heated for a first time to obtain an intermediate mixture solution. The temperature is increased to accelerate the reaction rate, and under nitrogen protection and a second temperature, the intermediate is heated for a second time to finally obtain a methyl-modified covalent triazine polymer (i.e., the aforementioned "methylated covalent triazine polymer"). The second temperature is higher than the first temperature.
[0046] Furthermore, the methylated covalent triazine polymer was purified and extracted using organic solvents and high-purity water, respectively. The organic solvents included N,N-dimethylformamide, dichloromethane, methanol, and ethanol, which were used as purification and extraction solvents for the material.
[0047] The present invention first conducted experimental tests and derived the mechanism of the preparation method disclosed herein, such as... Figure 1 As shown, Figure 1 This is a reaction mechanism diagram of the preparation method of the methyl-modified triazine group structure in this invention. The illustrated structure uses benzyl benzoate as a schematic structure to demonstrate the reaction mechanism.
[0048] This invention is the first to use an anhydride catalyst to catalyze the cyclization of dimethylimide compounds to prepare methylated covalent triazine polymers. The preparation process is simple, with mild reaction conditions including temperature and acid / base levels, thus expanding the synthetic pathways for methylated covalent triazine polymers. Furthermore, by controlling the amount of anhydride catalyst used and the polymerization temperature, the problem of difficulty in functionalization during the preparation of traditional CTFs is solved.
[0049] Another aspect of the present invention provides a methylated covalent triazine polymer prepared by the aforementioned preparation method.
[0050] Furthermore, the specific surface area of the methylated covalent triazine polymer is 60–560 m². 2 / g, with a pore size of 0.5–10 nm.
[0051] The backbone of the methylated covalent triazine polymer in this invention is composed of a methyl-modified triazine π-conjugated system. The specific methyltriazine structure not only broadens the light absorption range of the catalyst, but also provides an ideal model platform for elucidating the structure-activity relationship in photocatalytic CO2RR.
[0052] Another aspect of the present invention provides a methylated covalent triazine polymer, the methylated covalent triazine polymer comprising a plurality of repeating structural units having a structure as shown in formula (II):
[0053]
[0054] Where n = 1 to 4, and the dashed lines represent the bond connection positions.
[0055] Furthermore, the specific surface area of the methylated covalent triazine polymer is 60–560 m². 2 / g, with a pore size of 0.5–10 nm.
[0056] Furthermore, the number-average molecular weight of the methylated covalent triazine polymer is 15-25 kDa.
[0057] In this invention, the backbone of the methylated covalent triazine polymer is composed of a methyl-modified triazine π-conjugated system. The specific methyltriazine structure not only broadens the light absorption range of the catalyst, but also promotes the transfer of photogenerated electrons and accelerates the carbon dioxide reduction reaction.
[0058] Another aspect of the present invention provides the use of the aforementioned methylated covalent triazine polymer in the preparation of organic semiconductor materials or in the photocatalytic reduction of carbon dioxide.
[0059] Another aspect of the present invention provides an organic semiconductor material comprising at least the aforementioned methylated covalent triazine polymer.
[0060] Another aspect of the present invention provides a method for photocatalytic reduction of carbon dioxide, comprising:
[0061] Carbon dioxide is introduced into a reaction device equipped with a photocatalyst and subjected to a photocatalytic reaction under visible light irradiation, thereby reducing carbon dioxide to carbon monoxide; wherein the photocatalyst includes the aforementioned methylated covalent triazine polymer.
[0062] Furthermore, with a photocatalyst dosage of 5 mg and excitation under visible light (>420 nm) at room temperature, the CO yield was 524.5 μmol·h⁻¹. -1 The catalytic system showed no significant change in activity after four cycles of cyclic reaction.
[0063] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments and accompanying drawings. This embodiment is implemented on the premise of the technical solution of the invention, and provides detailed implementation methods and specific operation processes. However, the protection scope of the present invention is not limited to the following embodiments.
[0064] Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.
[0065] Example 1
[0066] In a protective atmosphere, 1 mmol of terephthalamide hydrochloride was reacted with an anhydride catalyst (trifluoromethanesulfonic anhydride) in DMAC solvent (3-10 mL) at 120 °C for 1-3 days, followed by heating to 150 °C and reacting for 1-5 days to finally obtain a methyl-modified covalent triazine polymer (methylated covalent triazine polymer). The resulting solid powder was soaked in DMF, CH2Cl2, and EtOH, and then Soxhlet extracted in MeOH solvent for 24 h to obtain a brown powder with a yield of 159.9 mg. The relative molecular mass of the structural unit corresponding to terephthalamide hydrochloride was 235.1 g / mol, so the yield was 68.1%, denoted as methyl-CTF-1.
[0067] Figure 2 These are the CTF (Continuous Transformer Infrared Spectra) of the dimethylimidone monomer terephthalamide hydrochloride, the methyl-modified covalent triazine polymer, and the methyl-free covalent triazine polymer material synthesized by conventional methods in Example 1. Figure 2 As shown, at 1700cm -1 Characteristic signal peaks of benzene ring skeletal vibrations were detected at 1520 cm⁻¹, confirming the presence of the benzene ring. CTF and methyl-modified CTF showed peaks at 1520 cm⁻¹. -1 The characteristic signal peak of CN stretching vibration was detected at 1361 cm⁻¹. -1 The characteristic signal peak of the triazine ring respiratory vibration was detected at 1423 cm⁻¹, and the CTF of methyl-modified CTF was at 1423 cm⁻¹. -1 The characteristic signal peak of the stretching vibration of methyl groups was detected, which verified the presence of the methyl structure in the methyl-modified CTF structure, indicating that the methyl-modified covalent triazine polymer was successfully synthesized in situ in this embodiment.
[0068] Example 2
[0069] Weigh 0.1 mmol of [1,1′-biphenyl]-4,4′-bis(carboxyimide) dihydrochloride, 0.05 mmol of 1,1,1-biphenyl-4,4-dimethylbis(N-phenylmethylamine) anhydrous carbonate, benzaldehyde (0.05 mL-0.5 mL), and DMF solvent (1-10 mL) into a 50 mL two-necked round-bottom flask equipped with a reflux condenser and a stir bar. Under nitrogen protection, the mixture was heated at 80 °C for 24 hours, 120 °C for 48 hours, and 150 °C for 72 hours, respectively. After cooling the reaction system to room temperature, it was filtered and treated sequentially with 5% dilute hydrochloric acid, DMF, ethanol, and dichloromethane to remove excess metal salts (carbonates) and unreacted oligomers or monomers. The product was then dried in a vacuum drying oven at 100 °C for 12 hours to obtain a methyl-free covalent triazine polymer material CTF, denoted as CTF. In this embodiment, the carbonate catalyst can be any one of cesium carbonate, sodium carbonate, lithium carbonate, or potassium carbonate.
[0070] Example 3
[0071] In a protective atmosphere, 1 mmol of [1,1′-biphenyl]-4,4′-bis(carboxyimide) dihydrochloride was reacted with an anhydride catalyst (benzoic anhydride) in DMAC and 5-10 mL of mesitylene solvent. The reaction was first heated to 120 °C for 1-5 days, then heated to 150 °C for 2-7 days to finally obtain a brown product, a methyl-modified covalent triazine polymer (methyl-CTF-2). After the reaction, the filtered solid powder was soaked in DMF, CH2Cl2, and EtOH, respectively, and then Soxhlet extracted in MeOH solvent for 24 h to obtain a brown powder. The relative molecular mass of the structural unit corresponding to [1,1′-biphenyl]-4,4′-bis(carboxyimide) dihydrochloride was 311.3 g / mol, and the yield of methyl-CTF-2 was 74.5%.
[0072] Figure 3 These are solid-state carbon NMR spectra of CTF, methyl-CTF-1, and methyl-CTF-2 prepared in Examples 1-3.
[0073] Example 4
[0074] In a protective atmosphere, 1 mmol of 1,1:4,1-terphenyl-4,4-dimethylamidine was reacted with an anhydride catalyst (0.5 mL-3 mL of acetic anhydride) in DMAC and o-dichlorobenzene solvent (5-10 mL) at 120 °C for 1-5 days, followed by heating to 150 °C and reacting for 1-7 days to finally prepare a methyl-modified covalent triazine polymer product (methyl-CTF-3). After the reaction, the filtered solid powder was soaked in DMF, CH2Cl2, and EtOH, respectively, and then Soxhlet extracted in MeOH solvent for 24 h to obtain a dark brown powder. The relative molecular mass of the structural unit corresponding to 1,1:4,1-terphenyl-4,4-dimethylamidine was 314.39 g / mol, and the yield of methyl-CTF-3 was 81.3%.
[0075] Application examples
[0076] The covalent triazine polymers (methyl-modified CTF prepared in Example 1) and the methyl-free CTF prepared in Example 2 were irradiated with visible light for 4 hours. Before irradiation, the covalent triazine polymer materials were uniformly dispersed on a reactor. The reaction system was evacuated, carbon dioxide was introduced, and after standing for 30 minutes, ultrapure water saturated with carbon dioxide was added.
[0077] A 300W xenon lamp is used as the light source, and a 420nm cutoff filter is configured to obtain visible light for photocatalysis.
[0078] Every 30 minutes, a portion of the gas in the system is taken from the photocatalytic device using a syringe. The concentration of carbon monoxide in the syringe is obtained using gas chromatography, and the amount of carbon monoxide produced is calculated in combination with the gas volume in the photocatalytic device.
[0079] Figures 4a-4b This is a graph showing the performance of the methyl-modified covalent triazine polymer in the photocatalytic reduction of carbon dioxide in pure water in this embodiment.
[0080] As shown in Figure 4, within 2 hours, CTF, methyl-CTF-1, and methyl-CTF-2 achieved carbon monoxide yields of 89.3 μmol / g / h, 236.8 μmol / g / h, and 524.5 μmol / g / h, respectively, and exhibited good catalytic stability.
[0081] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.
[0082] It should be understood that the technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made to the technical solutions of the present invention without departing from the spirit and scope of the claims are within the scope of protection of the present invention.
Claims
1. A method for preparing a methylated covalent triazine polymer, characterized in that, include: Methylated covalent triazine polymers were prepared by reacting dimethylimidides in the presence of an anhydride catalyst. The anhydride catalyst includes any one or more combinations of trifluoromethanesulfonic anhydride, benzoic anhydride, acetic anhydride, and trifluoroacetic anhydride. The dimethylimidide compound has the structure shown in formula (I): ； Formula (I); Where n = 1~4; The molar ratio of amine functional groups to acid anhydride catalysts in the dimethyl sulfide compounds is 1:(1-100).
2. The preparation method according to claim 1, characterized in that, Specifically, it includes: Under a protective atmosphere, a dimethyl imidide compound, an acid anhydride catalyst, and an organic solvent are mixed and reacted at a first temperature to form an intermediate; then the intermediate is heated to a second temperature and the reaction continues to obtain a methylated covalent triazine polymer; wherein the first temperature is 30~130℃, the second temperature is 130~200℃, and the second temperature is higher than the first temperature.
3. The preparation method according to claim 2, characterized in that: The organic solvent is an anhydrous organic solvent, which includes any one or more combinations of anhydrous dioxane, anhydrous mesitylene, o-dichlorobenzene, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, anhydrous toluene, anhydrous methanol, and N-methylpyrrolidone.
4. The preparation method according to claim 2, characterized in that: The reaction time at the first temperature is 1 to 5 days.
5. The preparation method according to claim 2, characterized in that: The reaction time at the first temperature is 1 to 7 days.
6. The preparation method according to claim 2, characterized in that, Also includes: After the reaction is complete, the obtained product is purified and extracted.