WO2019130983A1

WO2019130983A1 - Carbon nitride, method for producing same, and semiconductor material

Info

Publication number: WO2019130983A1
Application number: PCT/JP2018/044203
Authority: WO
Inventors: 正人栗原; 学石崎; みゆ荒井
Original assignee: 国立大学法人山形大学
Priority date: 2017-12-25
Filing date: 2018-11-30
Publication date: 2019-07-04
Also published as: JPWO2019130983A1; TW201936489A

Abstract

Provided are: a carbon nitride in which a band gap in a graphite type carbon nitride (g-C3N4) can be systematically controlled in an extremely broad region from approximately 2.7 eV to 0 eV using a simple and inexpensive method; a method for producing same; and a semiconductor material. This carbon nitride comprises a polymer of: a first monomer, dicyandiamide; and at least one second monomer selected from the group consisting of cyclic carbonates and organic compounds having two or more identical or different functional groups selected from the group consisting of hydroxyl groups, amino groups, carboxyl groups and amide groups. The molar ratio of the first monomer and the second monomer is 100:0.1-100:100. Moreover, oxalic acid is excluded as the second monomer. This carbon nitride is obtained by weighing out, mixing, heating and polymerizing the monomers. A carbon nitride having a band gap of 0.01-2.5 eV can be used as a semiconductor material.

Description

Carbon nitride, method for producing the same, and semiconductor material

The present invention relates to carbon nitride, a method of manufacturing the same, and a semiconductor material, and more specifically, carbon nitride having a band gap controlled by doping of graphite-type carbon nitride (g-C ₃ N ₄ ), a method of manufacturing the same, and a semiconductor material It is about

Graphite-type carbon nitride (g-C ₃ N ₄ ) in which triazine or tristriazine molecules are infinitely linked is a substance exhibiting a yellow absorption due to an absorption band extending around 460 nm, which is a visible light region derived from a band gap of 2.7 eV It is. Graphite-type carbon nitride has been studied for its application as a semiconductor material composed of carbon and nitrogen atoms, which are ubiquitous elements without concern of resource exhaustion. In particular, since the valence band and the conduction band are in an energy range that can thermodynamically decompose water molecules into oxygen and hydrogen, they are attracting attention as metal-free photocatalysts excellent in chemicals and environmental durability.

Graphite-type carbon nitride can be synthesized by heating a raw material such as urea, melamine, or dicyandiamide at about 550 ° C. Heretofore, molecular doping methods have been developed to synthesize graphitic carbon nitride responsive to the broad visible light wavelengths of sunlight. The band gap is systematically reduced by copolymerizing dicyandiamide using barbituric acid as a molecular doping agent (Non-patent document 1) and copolymerizing with melamine using triamino pyrimidine (Non-patent document 2) Have succeeded. A carbon nitride having a reduced band gap has been synthesized by copolymerization with a molecule containing an aromatic or double bond-containing carbon skeleton with an amino group or a cyano group, or both (Non-patent Document 3). It is also reported that quinoline is molecularly doped (Non-patent Document 4). Molecular doping is achieved by forming a Schiff base with furan or thiophene having a formyl substituent and melamine and the like (Non-patent Document 5). In each of these prior art documents, aiming at doping of aromatic molecules having a high carbon composition ratio, reduction of the band gap and band gap control depending on the doping amount are performed.

On the other hand, in doping of non-aromatic molecules, a method of hydrogen bonding ethanol and melamine (Non-patent document 6) and hydrogen bonding of melamine and cyanuric acid with ethylene glycol (Non-patent document 7) has been reported .

In addition, it is theoretically known that the band gap can be extended to 1 eV by doping nitrogen atoms into graphene with a band gap of 0 eV and introducing a defect structure. The graphene-derived carbon nitride is also expected to be applied to a TFT element function as a narrow band gap semiconductor, a secondary battery electrode, and the like.

Since a black carbon nitride group having a band gap of 1 eV to 0 eV has high conductivity, development of an electrochemical catalyst in which a nitrogen site functions as an active site has been advanced. In addition to metal-free oxygen reduction catalysts, which replace high-priced platinum catalysts used in fuel cell electrodes, metal-free carbon nitride catalysts that electrochemically reduce carbon dioxide to useful substances with two or more carbon atoms such as ethanol. The function has been reported (Non-patent Document 8). An electrochemical catalytic function that converts carbon dioxide to ethanol with high efficiency and high selectivity is reported by a catalyst in which copper nanocrystals and carbon nitride are complexed (Non-Patent Document 9), metal-free carbon dioxide to ethanol An electrochemical catalyst of carbon nitride that converts with high efficiency and efficiency is reported (Non-patent Document 10).

As described above, the carbon nitride group composed of only ubiquitous elements can be controlled from a band gap of 2.7 to 0 eV, and the photosemiconductor catalyst function responding to the visible light, the metal free electrochemical catalyst, etc. As a target metal, it is a material that is expected to develop high functions and its practical use.

However, according to Non-Patent Documents 1 and 2, it is understood that the band gap control by molecular doping is limited to 2.7 to 1 eV. In addition, the problem remains that such doping molecules are more expensive than urea, melamine and dicyandiamide which are raw materials of graphite type carbon nitride. Also in Non-Patent Documents 6 and 7, the introduction of ethanol or ethylene glycol hardly increases the carbon composition ratio as compared with graphite-type carbon nitride, and the reduction of the band gap is very slight. In addition, nitrogen atom doping has problems in manufacturing in industrial applications, such as requiring special synthesis equipment including gas reaction.

Therefore, in view of the above problems, in the present invention, it is easy to systematically control the band gap in a very wide range from around 2.7 to 0 eV in graphite-type carbon nitride (g-C ₃ N ₄ ). An object of the present invention is to provide carbon nitride which can be produced by an inexpensive method, a method for producing the same, and a semiconductor material.

In order to achieve the above object, the present invention, according to one aspect thereof, is carbon nitride, and the ground carbon is composed of dicyandiamide as a first monomer, a hydroxyl group, an amino group, a carboxyl group, and an amide group. And a polymer of at least one second monomer selected from the group consisting of cyclic carbonates, and an organic compound having two or more same or different functional groups selected from the group, and the first monomer and the second monomer The molar ratio to is 100: 0.1 to 100: 100. As the second monomer, oxalic acid is excluded. The said polymer can be obtained by the manufacturing method mentioned later. The polymer is preferably a fired product of the first monomer and the second monomer.

The organic compound having two or more same or different functional groups selected from the group consisting of a hydroxyl group, an amino group, a carboxyl group, and an amide group is represented by the following general formula (1)
AR B: Formula (1)
(Wherein, A and B are each independently a functional group selected from the group consisting of a hydroxyl group, an amino group, a carboxyl group, and an amide group, which may be the same or different, and R is And a linear or branched alkylene group having 0 to 20 carbon atoms, an aromatic ring, or a cycloalkane).

In the formula (1), when R is an aromatic ring, A and B are preferably bonded to the ortho position of the aromatic ring.

The first monomer may be composed of dicyandiamide and melamine, in which case the weight ratio of dicyandiamide to melamine is preferably 10:90 to 30:70.

The carbon nitride made of the polymer according to the present invention preferably has a band gap of 0.01 to 2.5 eV. The band gap value is more preferably 1.56 eV or less, and in this case, the C / N atomic ratio of carbon nitride is preferably in the range of 0.77 to 3.23. The band gap value is more preferably more than 0.40 ev and not more than 1.56 eV, and in this case, the C / N atomic ratio of carbon nitride is in the range of 0.77 to less than 0.83. preferable. Alternatively, the band gap value is more preferably 0.40 eV or less, and in this case, the C / N atomic ratio of carbon nitride is preferably in the range of 0.83 to less than 3.23.

Another aspect of the present invention is a semiconductor material, which comprises the carbon nitride according to the present invention described above.

According to another aspect of the present invention, there is provided a method for producing carbon nitride, which method is selected from the group consisting of dicyandiamide as a first monomer, a hydroxyl group, an amino group, a carboxyl group, and an amide group. A step of preparing a mixture by weighing and then mixing at least one second monomer selected from the group consisting of the above organic compounds having the same or different functional groups, and cyclic carbonate, and heating the mixture And a step of polymerizing the first monomer and the second monomer, wherein the molar ratio of the first monomer to the second monomer in the mixture is 100: 0.1 to 100: 100. As the second monomer, oxalic acid is excluded. The first monomer and the second monomer in the manufacturing method according to the present invention can use the first monomer and the second monomer in the carbon nitride according to the present invention described above.

According to the present invention, dicyandiamide, which is a raw material of graphite-type carbon nitride, is used as a first monomer, and in order to perform carbon (molecular) doping on this graphite-type carbon nitride, an organic having two or more predetermined or the same or different functional groups The band gap of the graphitized carbon nitride comprising a polymer obtained by polymerizing the compound and at least one member selected from the group consisting of cyclic carbonates using the second monomer as the second monomer comprises the first monomer and the second monomer It is possible to control systematically in a very wide range from around 2.7 to 0 eV simply and inexpensively by changing the molar ratio of, or selecting the compound of the second monomer. The same effect can be obtained by adding melamine to dicyandiamide as the first monomer. In addition, a polymer having a band gap of 0.01 to 2.5 eV has the performance as an n-type semiconductor due to the presence of nitrogen in a planar structure, and is very useful as a semiconductor material.

The graph of the infrared absorption spectrum of the polymer obtained by making dicyandiamide and propylene carbonate react in the molar ratio of 100: 0 to 100: 100 is shown. The powder X-ray analysis (XRD) graph of the polymer obtained by making dicyandiamide and a propylene carbonate react in the molar ratio of 100: 0 to 100: 100 is shown. The scanning electron microscope image of the polymer obtained by reacting dicyandiamide with propylene carbonate at a molar ratio of 100: 10 is shown.

Hereinafter, one embodiment of carbon nitride according to the present invention, a method for producing the same, and a semiconductor material will be described.

The carbon nitride of the present embodiment is made of a polymer obtained by polymerizing predetermined first and second monomers described in detail below at a predetermined molar ratio.

(1st monomer)
The first monomer is essentially a dicyandiamide used as a raw material of the graphite type carbon nitride _{_{(g-C 3 N 4)}} , rational _formula: represented by H 2 N-CNH-NH- CN. The melting point of dicyandiamide is 209 ° C. and the boiling point is 252 ° C. When it is heated above the melting point, ammonia is generated to produce melamine and the like.

In addition to the above dicyandiamide, melamine can also be used as the first monomer. When melamine is added, the weight ratio of dicyandiamide to melamine is preferably in the range of 10:90 to 30:70. By adding melamine as the first monomer in such a range, the band gap of carbon nitride formed of a polymer with the second monomer can be reduced, and by using melamine cheaper than dicyandiamide, the material cost is further increased. It has the merit of being able to lower the

(2nd monomer)
As the second monomer, an organic compound having two or more same or different functional groups selected from the group consisting of a hydroxyl group, an amino group, a carboxyl group, and an amide group can be used. This organic compound may be used alone or as a mixture of two or more. More specifically, for example, an organic compound represented by the following general formula (1) is preferably used.
AR B: Formula (1)

In the above formula (1), A and B are each independently a functional group selected from the group consisting of a hydroxyl group, an amino group, a carboxyl group, and an amide group, and may be the same or different.

In the above formula (1), R may be a linear or branched alkylene group having 0 to 20 carbon atoms, an aromatic ring, or a cycloalkane. The upper limit of the carbon number of the alkylene group is more preferably 20 or less, and still more preferably 10 or less. The lower limit of the carbon number of the alkylene group may be one or more.

More specifically, diamine compounds, amino alcohol compounds, hydroxycarboxylic acid compounds, aminocarboxylic acid compounds, diol compounds, polyhydric alcohol compounds, diamide compounds, or aromatic compounds are preferably used as the organic compound.

Examples of diamine compounds include ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminopentane, 1,8-diaminooctane A diamine compound having a linear alkylene of 1 to 20 carbon atoms, such as 1,9-diaminononane, 1,10-diaminodecane, 1,12-diaminododecane, or 1,20-diaminoeicosane, or 1,2 And diamine compounds having a branched alkylene having 1 to 20 carbon atoms such as diaminopropane, 1,2-diaminobutane, 1,3-diaminobutane, 2-methyl-1,3-diaminopropane and the like.

As an amino alcohol compound, ethanolamine, 3-aminopropanol, 4-aminobutanol, 5-aminopentanol, 6-aminohexanol, 7-aminopentanol, 8-aminooctanol, 9-aminononanol, 10-amino Amino alcohol compounds having linear alkylene having 1 to 20 carbon atoms such as decanol, 12-aminododecanol, or 20-aminoeicosanol, or isobutanolamine, 1,2-diaminopropanol, 1,2- Examples thereof include amino alcohol compounds having a branched alkylene having 1 to 20 carbon atoms such as diaminobutanol, 1,3-diaminobutanol, 1,2-diaminopropanol, or 2-methyl-1,3-diaminopropanol.

As a hydroxycarboxylic acid compound, glycolic acid, 3-hydroxypropionic acid, 4-hydroxybutyric acid, 6-hydroxycaproic acid, 8-hydroxycaprylic acid, 10-hydroxycaprylic acid, 12-hydroxylylic acid, 18-hydroxystearic acid Or a hydroxycarboxylic acid compound having a linear alkylene of 1 to 20 carbon atoms such as 20-hydroxyarachidic acid or a hydroxycarboxylic acid compound having a branched alkylene having 1 to 20 carbon atoms such as 3-hydroxybutyric acid Can be mentioned.

Examples of aminocarboxylic acid compounds include glycine, 3-aminopropionic acid, 4-aminobutyric acid, 6-aminocaproic acid, 8-aminocaprylic acid, 10-aminocaprylic acid, 12-aminolylic acid, 18-aminostearic acid, or 20 And aminocarboxylic acid compounds having a linear alkylene of 1 to 20 carbon atoms such as aminoarachidic acid, or aminocarboxylic acid compounds having a branched alkylene of 1 to 20 carbon atoms such as 3-aminobutyric acid.

As a diol compound, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-pentanediol, 1,8-octanediol, A diol compound having a linear alkylene having 1 to 20 carbon atoms, such as 1,9-nonanediol, 1,10-decanediol, 1,12-dodecanediol, or 1,20-eicosanediol, or 1,2 -Diol having branched alkylene having 1 to 20 carbon atoms such as propanediol, 1,2-butanediol, 1,3-butanediol, 1,2-propanediol, or 2-methyl-1,3-propanediol Compounds are mentioned.

As polyhydric alcohol compounds, 1,2,3-propanetriol (that is, glycerol), 1,2,3-butanetriol, oligovinyl alcohol (polymerization degree is 10 to 20), polyvinyl alcohol (polymerization degree is 21 or more) Or 1,2,3,4,5,6-cyclohexanehexaol (ie, inositol) and the like.

Examples of diamide compounds include oxamide, malonamide, 2-methoxypropanediamide, 1,6-hexanediamide, and 1,8-octanediamide.

Examples of the aromatic compound include aromatic compounds having two or more identical or different functional groups selected from the group consisting of a hydroxyl group, an amino group, a carboxyl group, and an amide group at the ortho position of the aromatic ring. And catechol, phthalic anhydride, ortho phenylene diamine, ortho aminophenol, salicylic acid, or ortho amino benzoic acid and the like.

Further, as the second monomer, a cyclic carbonate can be used instead of or in addition to the above-described organic compound. The cyclic carbonate is an ester of an alkylene diol having 2 to 4 carbon atoms and carbonic acid, and examples thereof include ethylene carbonate, propylene carbonate, butylene carbonate, and carbonic acid isobutylene.

As the second monomer, oxalic acid is excluded.

(Method of producing carbon nitride)
In the method for producing carbon nitride of the present embodiment, a step of mixing the first monomer and the second monomer described above after mixing and preparing the mixture, and heating the mixture to produce the first monomer and the second monomer And the step of polymerizing.

The heating conditions in the polymerization step are not particularly limited as long as the temperature and the time at which the first monomer and the second monomer sufficiently polymerize, and for example, although depending on the kind of the compound selected as the monomer, It is preferable to raise the temperature to 300 to 900 ° C. at a temperature rising rate of 1 min and maintain this temperature for 1 to 3 hours, and to a temperature of 550 ° C. at a heating rate of 15 ° C./min for 2 hours It is more preferable to maintain this temperature. By heating at a high temperature (eg, 900 ° C.), the carbon number can be controlled, or the surface area can be increased.

(Band gap control)
The molar ratio of the first monomer to the second monomer in the mixing step is 100: 0.1 to 100: 100. By setting the molar ratio in this range, the band gap of the resulting polymer can be controlled in a very wide region from around 2.7 to 0 eV.

A polymer having a desired band gap can be obtained depending on the type of compound selected as the monomer and the molar ratio of the first monomer to the second monomer. For example, when a diamine compound is selected as the second monomer, the band gap can be greatly reduced by adding a small amount of diamine. On the other hand, when a cyclic carbonate is selected as the second monomer, the decrease in band gap with respect to the addition amount is small as compared with the diamine compound, and therefore, the band gap can be accurately controlled to a desired value.

As a 2nd monomer which can reduce a band gap largely by addition of a small amount, an amino alcohol compound and a diol compound other than a diamine compound can be mentioned. Further, by using a compound having a long alkylene chain in the diamine compound, the diol compound and the like, the band gap can be greatly reduced by the addition of a small amount.

In addition to propylene carbonate compounds, polyhydric alcohol compounds, aminocarboxylic acid compounds, diamide compounds, hydroxycarboxylic acid compounds and the like can be mentioned as the second monomer that controls the band gap to the desired value with high precision. By selection of the above, it is possible to obtain carbon nitride having a target band gap with high accuracy. The molar ratio of the first monomer to the second monomer is preferably in the range of 100: 0.1 to 100: 100, and the height and accuracy of the band gap depend on the purpose, and the range and the second range It can be achieved by the choice of the type of monomer.

In this way, compounds to be used can be selected or mixed depending on the purpose. The band gap value of carbon nitride is preferably controlled in the range of 0.01 to 2.5 eV. The band gap value of carbon nitride can be controlled to a desired value or range depending on the application of carbon nitride.

Carbon nitride having a band gap in the range of 0.01 to 2.5 eV has the performance as an n-type semiconductor due to the presence of nitrogen in a planar structure. Therefore, the semiconductor material of the present embodiment is made of the carbon nitride of the present embodiment which is controlled to have the band gap in the range of 0.01 to 2.5 eV described above.

EXAMPLES The present invention will be specifically described by way of the following Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Example 1 Polymer of Dicyandiamide with 1,6-Diaminohexane (Polymerization)
Assuming 1.0 g of dicyandiamide (Tokyo Chemical Industry, purity> 98.0%) and a molar ratio of 100, 1,6-diaminohexane (Tokyo Chemical Industry, purity> 99.0) at a molar ratio of 0 to 20. Mixed), put the mixture in an alumina crucible, covered, heated up to 550 ° C. at a heating rate of 15 ° C./min in a muffle furnace (denken, model: KDF S-70), and under the atmosphere for 2 hours The polymer was calcined to obtain a polymer. Thereafter, the fired product was ground in an alumina mortar and various measurements were made.

(Band gap analysis)
Diffuse reflection spectrum measurement of the obtained polymer was carried out with a diffuse reflection unit (Shimadzu Corporation, model: ISR-3100) using an ultraviolet visible near infrared spectrophotometer (Shimadzu Corporation, model: UV-3600) . Then, the energy of the band gap was determined spectrochemically from the Tauc plot from the Kubelka-Munk function. The results are shown in Table 1. When 1,6-diaminohexane was not added at all (the molar ratio was 0), the band gap of the obtained polymer was 2.7 eV, which was confirmed to be g-C ₃ N ₄ . Then, the band gap decreased rapidly when 1,6-diaminohexane was added. This is similar behavior to graphite absorbing electromagnetic waves in a wide range of wavelengths. When the addition amount is 10 molar ratio or more, the band gap reaches nearly 0 eV, and the band gap can not be determined spectrochemically. In the table, “̃0” is described as infinitely close to 0 eV.

[Examples 2 to 8] Polymers of dicyandiamide and various second monomers (polymerization)
The second monomers listed in Table 2 instead of 1,6-diaminohexane, ie, ethylenediamine (Kanto Chemical, Deer Class 1), 1,4-diaminobutane (Tokyo Chemical Industry, purity> 98.0%), ethylene glycol (Tokyo Chemical Industry, purity> 99.5%), aminoethanol (Kanto Chemical, purity> 99.5%), glycine (Nacalai Tesque, special grade reagent), oxamide (Tokyo Chemical Industry, purity> 98.0%), A polymer was obtained in the same manner as Example 1, except that glycolic acid (Tokyo Chemical Industry, purity> 98.0%) was mixed at the molar ratio described in Table 2. All of the second monomers used showed a good reaction with dicyandiamide.

(Band gap analysis)
The band gap of the polymer was measured in the same manner as in Example 1. The results are shown in Table 2. The band gap of each of the second monomers decreased with the increase of the addition amount of the second monomer.

Comparative Examples 1 to 4 Polymer of Dicyandiamide and Monomer Having One Functional Group (Polymerization)
N-hexyl alcohol (Tokyo Chemical Industry Co., Ltd., purity> 98.0%) which is a monomer having only one functional group described in Table 3 instead of 1,6-diaminohexane, n-hexylamine (Tokyo Kasei Industry, purity> 99.0%), acetic acid (Kanto Chemical, special grade), acetamide (Kanto Chemical, special grade) were mixed in the molar ratio described in Table 3 in the same manner as in Example 1 except that the polymer was mixed Obtained. In the reaction with each monomer in Table 3, no decrease in band gap was observed and no good reaction was shown.

Comparative Example 5 Polymer of Dicyandiamide and Oxalic Acid (Polymerization)
A polymer was obtained in the same manner as in Example 1 except that oxalic acid (Matsuho Pharmaceutical, 99.6% purity) was mixed instead of 1,6-diaminohexane. However, no decrease in band gap was observed in the reaction with oxalic acid, and dicyandiamide and oxalic acid did not show a good reaction.

[Examples 9 to 15] Polymer of dicyandiamide and alkylene diol (polymerization)
A polymer was obtained in the same manner as in Example 1 except that, instead of 1,6-diaminohexane, an alkylene diol selected from 2 to 12 carbon atoms shown in Table 4 was mixed at a molar ratio of 10.

(Band gap analysis)
The band gap of the polymer was measured in the same manner as in Example 1. The results are shown in Table 4. The longer the alkylene chain of the alkylene diol, the lower the band gap tends to be.

[Example 16] Polymer of dicyandiamide and cyclic carbonate (polymerization)
A polymer was prepared in the same manner as in Example 1, except that propylene carbonate (Kanto Chemical for electrochemistry, purity 99.5%) was mixed at a molar ratio of 0 to 100 instead of 1,6-diaminohexane. I got The formation amount of the polymer is shown in Table 5. The polymer was obtained in a yield of 0.4 g or more when the amount of propylene carbonate added was 50 at a molar ratio.

(Band gap analysis)
The band gap of the polymer was measured in the same manner as in Example 1. The results are shown in Table 5. The band gap decreased as the amount of propylene carbonate added increased. When the addition amount was 50 or more in molar ratio, the band gap reached nearly 0 eV, and the band gap could not be determined spectrochemically.

(Elemental analysis)
In order to determine the atomic ratio (C / N ratio) of carbon and nitrogen atoms, EDX analysis is performed by a scanning electron microscope, and the analysis result is the C / N ratio of the polymer when the amount of propylene carbonate added is 0. The intensity was corrected and the results are shown in Table 5. The C / N atomic ratio increases with the decrease in the band gap due to the increase in the amount of propylene carbonate added.

(Infrared analysis)
The infrared absorption spectrum (Thermo Scientific Nicolet 6700) of the polymer obtained in Example 16 was measured. The results are shown in FIG. Regardless of the amount of propylene carbonate added, it showed infrared absorption similar to g-C ₃ N ₄ when the amount of propylene carbonate added was 0 in molar ratio. On the other hand, the spectrum broadened as the addition amount increased. The characteristic absorption around 800 cm ^-1 is derived from the triazine structure. The absorption can be clearly observed up to a molar ratio of 20, but it can not be observed at a molar ratio of 50 or more, which indicates that the triazine structure changes significantly with the increase of the additive amount. . The results are also consistent with the results of powder X-ray analysis described below.

(Structural analysis by powder X-ray diffraction (XRD))
The structure of the polymer obtained in Example 16 was analyzed by powder X-ray diffraction (Rigaku, MiniFlex II). The results are shown in FIG. The XRD pattern of g-C ₃ N ₄ when the amount of propylene carbonate added is 0 in molar ratio is derived from the signal by the 13 ° tris triazine periodic structure (in plane) and the interlayer distance of the 27 ° tris triazine layer Pattern. As the amount of propylene carbonate added increases, the signal derived from the interlayer distance is shifted to the lower angle side (the distance between the surfaces tends to be longer) and approaches the inter-surface distance (26 °) of the graphite. I understand. Also, the signal due to the 13 ° tris triazine periodic structure (in plane) is observed until the molar ratio of propylene carbonate is 20, but when it is more, it becomes unobservable along with the 27 ° signal broadening . These suggest that the abundance ratio of carbon atoms is increased due to the increase in the amount of propylene carbonate added.

(Observation by scanning electron microscope)
The polymer obtained in Example 16 and having propylene carbonate at a molar ratio of 10 was observed with a scanning electron microscope (JEOL, JEM 7600). The results are shown in FIG. It can be seen that the portion indicated in FIG. 4 has a layered structure.

[Example 17] Polymer of dicyandiamide and cyclic carbonate (polymerization)
A polymer was prepared in the same manner as in Example 1, except that ethylene carbonate (Kanto Chemical for electrochemistry, purity 99.5%) was mixed at a molar ratio of 0 to 20 instead of 1,6-diaminohexane. I got

(Band gap analysis)
The band gap of the polymer was measured in the same manner as in Example 1. The results are shown in Table 6. Compared to the other examples, the amount of decrease in the band gap with the increase in the amount of ethylene carbonate added was small.

Comparative Example 6 Polymer of Dicyandiamide and Carbonate Instead of 1,6-diaminohexane, dimethyl carbonate powder (Kanto Chemical, for electrochemistry, purity 99.5%) was mixed at a ratio of 15 in molar ratio. A polymer was obtained in the same manner as in Example 1. However, no decrease in band gap was observed.

[Examples 18 to 19] Polymer of dicyandiamide and a monomer having two or more hydroxyl groups (polymerization)
Instead of 1,6-diaminohexane, catechol (Nacalai Tesque, purity 和 95.0%) or glycerol (Wako Pure Chemical Industries, purity 97.0%), which are monomers having two or more hydroxyl groups shown in Table 7 The polymer was obtained in the same manner as in Example 1 except that the mixture was mixed at a molar ratio of 10.

(Band gap analysis)
The band gap of the polymer was measured in the same manner as in Example 1. The results are shown in Table 7. The band gap of the catechol having two hydroxyl groups in the aromatic ring and the polyhydric alcohol glycerol similarly decreased.

Comparative Example 7 Polymer of Melamine and Propylene Carbonate A polymer was obtained in the same manner as Example 16, except that melamine (Tokyo Chemical Industry, purity> 98%) was used instead of dicyandiamide of Example 16. . Although melamine is used as a raw material of g-C ₃ N ₄ similarly to dicyandiamide, in the polymer with propylene carbonate, no change in band gap was observed.

Comparative Example 8 Urea, Propylene Carbonate, and n Polymer A polymer was obtained in the same manner as in Example 16 except that urea (Tokyo Chemical Industry, purity> 99%) was used instead of dicyandiamide in Example 16. . Urea is used as a raw material of gC ₃ N _{4 in} the same manner as dicyandiamide, but no change in band gap was observed in the polymer with propylene carbonate.

Example 20 Polymer of Dicyandiamide, Melamine, and Ethylene Glycol (Polymerization)
The weight ratio of dicyandiamide to melamine was varied and mixed so that the total weight of dicyandiamide and melamine was 1 g. The mixture of dicyandiamide and melamine was adjusted to a molar ratio of 100, to which 50 ethylene glycol was added at a molar ratio, and mixed in an agate mortar. This was put in an alumina crucible, covered, heated to 550 ° C. at a heating rate of 15 ° C./min in a muffle furnace, and fired for 2 hours in the air to obtain a polymer. Thereafter, it was crushed in an alumina mortar and used for measurement.

(Band gap analysis)
The band gap of the polymer was measured in the same manner as in Example 1. The results are shown in Table 8. The band gap decreased when the weight ratio of dicyandiamide was 10 to 30%, and the band gap decreased as the weight ratio of dicyandiamide increased.

Claims

At least one selected from the group consisting of cyclic carbonates and dicyandiamide as the first monomer, an organic compound having two or more same or different functional groups selected from the group consisting of hydroxyl group, amino group, carboxyl group, and amide group Weighing and then mixing the two second monomers to prepare a mixture;
Heating the mixture to polymerize the first monomer and the second monomer, wherein a molar ratio of the first monomer to the second monomer in the mixture is 100: 0.1 to 100: 100. A method of producing carbon nitride, wherein the second monomer is oxalic acid.
At least one selected from the group consisting of cyclic carbonates and dicyandiamide as the first monomer, an organic compound having two or more same or different functional groups selected from the group consisting of hydroxyl group, amino group, carboxyl group, and amide group A carbon nitride comprising a polymer obtained by a method comprising: mixing two second monomers to prepare a mixture; and heating the mixture to polymerize the first monomer and the second monomer. There,
A molar ratio of the first monomer to the second monomer is 100: 0.1 to 100: 100, and the second monomer is carbon nitride except oxalic acid.
The organic compound having two or more same or different functional groups selected from the group consisting of a hydroxyl group, an amino group, a carboxyl group, and an amide group is represented by the following general formula (1)
AR B: Formula (1)
(Wherein, A and B are each independently a functional group selected from the group consisting of a hydroxyl group, an amino group, a carboxyl group, and an amide group, which may be the same or different, and R is , A linear or branched alkylene group having 0 to 20 carbon atoms, an aromatic ring, or a cycloalkane.)
The carbon nitride according to claim 2, having a structure represented by
The carbon nitride according to claim 2, wherein in the formula (1), R is an aromatic ring, and A and B are bonded to the ortho position of the aromatic ring.
The carbon nitride according to claim 2, wherein the first monomer comprises dicyandiamide and melamine, and the weight ratio of dicyandiamide to melamine is 10:90 to 30:70.
The carbon nitride according to claim 2, wherein the band gap is 0.01 to 2.5 eV.
The carbon nitride according to claim 6, wherein the C / N atomic ratio is in the range of 0.77 to 3.23, and the band gap value is 1.56 eV or less.
The C / N atomic ratio is in the range of 0.77 to less than 0.83, and the band gap value is more than 0.40 ev and 1.56 eV or less, or the C / N atomic ratio is 0.1. The carbon nitride according to claim 7, having a range of 83 or more and less than 3.23, and having a band gap value of 0.40 eV or less.
A semiconductor material comprising the carbon nitride according to claim 6.