KR101816369B1

KR101816369B1 - Method for preparing nanotube-MOF hybrid and the nanotube-MOF hybrid prepared therefrom

Info

Publication number: KR101816369B1
Application number: KR1020150187864A
Authority: KR
Inventors: 손대원; 고재형; 이정욱; 신주휘
Original assignee: 한양대학교 산학협력단
Priority date: 2015-12-28
Filing date: 2015-12-28
Publication date: 2018-01-09
Also published as: KR20170077692A

Abstract

The present invention relates to a method for preparing a composite comprising a metal-organic structure and a nanotube carrier, and a composite made therefrom. More particularly, the present invention relates to a method for uniformly dispersing a nanotube in a metal-organic structure (MOF) precursor solution; Supporting the solution of the MOF precursor on the lumen of the nanotube by applying a vacuum treatment to the solution; And recovering the nanotubes from the solution, heating the nanotubes, and washing the nanotubes. The present invention also relates to a nanotube-MOF composite produced from the nanotube-MOF composite.
According to the present invention, it is possible to produce a nanotube-MOF composite with high efficiency even when purification of the resultant product is easy after synthesis, MOF can be uniformly filled in the mold, and a separate chemical treatment is not required in the mold, Based nanotube-MOF composite and a nanotube-MOF composite produced from the same. In addition, the resulting composite exhibits excellent stability to water and exhibits unique gas adsorption characteristics due to the presence of micropores and mesopores.

Description

METHOD FOR PREPARING NANOTUBE-MOF COMPOSITION AND METHOD FOR PREPARING NANOTUBE-MOF COMPOSITION

The present invention relates to a method for producing a composite comprising a metal-organic structure and a nanotube carrier, and a composite made therefrom.

Metal-organic frameworks (MOFs) are a class of microporous materials formed from metal ions or metal ion clusters, and are extended three-dimensionally by linking structures by organic polyvalent ligands. Since the first synthesis of systematic MOFs has been reported (non-patent reference 1), hundreds of different MOFs have been reported for various applications, including drug delivery systems (DDS), carbon capture dioxide capture (CDC), and hydrogen gas storage for fuel.

Some researchers have reported attempts to synthesize MOFs within materials such as mesoporous materials, such as carbon nanofibers (CNFs), SBA-15 and silica monoliths. In these cases, the material properties are significantly improved, resulting in a surface area increase relative to the original material; Exhibit increased stability to water or other chemicals; Changes in the direction of growth (possibly due to limited crystal growth); Or for certain organic reactions.

For example, the study of supporting a substance in a tube using capillary phenomenon of carbon nanotubes was first reported in Nature, 1993 (Non-Patent Document 2). In addition, the surface tension required to utilize the capillary phenomenon is such that particles such as S, Se, and Cs including most of the solvent are possible, but pure metal liquids are difficult to use such force. The support of the material in the nanotube is effectively applied by decompressing the inside of the system, and the supported material can be stably held in the inner space by the capillary phenomenon. Also, due to the supported material, separation from a system such as a solution is possible. Therefore, the retention of the carrier material using the depressurization process and the capillary phenomenon provides a sufficient possibility for the nanotube to be utilized as a nanoreactor. In this application, the reaction in the tube can be carried out by polymerisation by crystallization, annealing, photoinitiated irradiation or chemical reaction through evaporation of solvent, and the reaction of the substance carried in the tube by this phenomenon is carried out as described above New features and properties can be imparted to the nanotube material.

However, problems are often encountered in purifying or separating the combined materials after synthesis from unused templates and separated bulk crystals. For example, P. Pachfule et al. Used a continuous centrifugation and washing method to separate MOF-5 @ CNF in the synthesis of MOF-5 in CNF pores (Non-Patent Document 3). Although the purification was possible because there was a relatively large difference in the density between MOF-5 crystals and MOF-5 @ CNF, the washing steps required a long time and the complete purification was not guaranteed. Furthermore, it was also difficult to uniformly load the MOFs between the pores.

Meanwhile, C. Wu et al. Attempted to avoid the purification problem by shortening the reaction time during MOF-5 synthesis in the presence of SBA-15 (Non-Patent Document 4). However, even in this case, the resulting crystals were not evenly distributed among the pores of SBA-15. Further, methods for employing specific functional groups on the mold inner surface to encapsulate MOF in mesoporous molds have also been proposed (Non-Patent Documents 3, 5, and 6). Establishing an effective synthesis method is a very important issue because these problems lead to a significant reduction in the net efficiency of the final product.

Therefore, the existing studies that introduced the MOF into the mold to improve the characteristics show the above-mentioned problems, as it can be inferred from the fact that these studies adopt the in-situ synthesis method, In the synthesis, it can be judged that the mesoporous materials are synthesized in the MOF precursor solution, and the following limitations can be regarded as follows: i) After the reaction, There is a problem that it takes a long time to purify the synthesized result or the purification itself is impossible. ii) it is impossible to evenly fill the template material because the precursors have different accessibility to different pores of the template; And iii) for the porous materials to be synthesized within the pores, the inner surface of the pores must provide a seed of crystallization, and thus the inner surface of the material pores to be the mold must have certain functional groups.

All of the above problems are inherent problems due to the in-situ solvothermal process, and there is a problem that the porous materials produced by these problems cause serious efficiency deterioration. Therefore, there is an urgent need for an X-situ synthesis method for effectively solving the above-mentioned problems.

Non-Patent Document 1: M. Eddaoudi, J. Kim, N. Rosi, D. Vodak, J. Wachter, M. O'Keeffe, O.M. Yaghi, Science 295 (2002) 469-472. Non-Patent Document 2: S.C. Tsang, Y.K. Chen, P.J.F. Harris, M.L.H. Green, Nature 372 (1994) 159-162. Non-Patent Document 3: P. Pachfule, B.K. Balan, S. Kurungot, R. Banerjee, Chem. Comm. 48 (2012), 2009-2011. Non-Patent Document 4: C.M. Wu, M. Rathi, S.P. Ahrenkiel, R.T. Koodali, Z. Wang, Chem. Comm. 49 (2013) 1223-1225. Non-Patent Document 5: Z. Xiang, Z. Hu, D. Cao, W. Yang, J. Lu, B. Han, W. Wang, Angew. Chem. Int. Ed. 50 (2011) 491-494. Non-Patent Document 6: C. Petit, T.J. Bandosz, Adv. Mater. 21 (2009) 4753-4757.

Accordingly, the present invention provides a novel X-situ synthesis method capable of exclusively and evenly distributing MOFs only inside the lumens of nanotubes while effectively solving the above-mentioned problems through the capillary phenomenon of the nanotubes.

Also, the present invention provides a nanotube-MOF composite which is manufactured by the X-situ synthesis method and includes a nanotube and a metal-organic structure supported on the lumen of the nanotube.

In order to solve the above problems,

Uniformly dispersing the nanotubes in a solution of a metal-organic structure (MOF) precursor;

Supporting the solution of the MOF precursor on the lumen of the nanotube by applying a vacuum treatment to the solution; And

And recovering the nanotubes from the solution, heating the nanotubes, and washing the nanotubes.

According to an embodiment of the present invention, the nanotube may be a nanotube selected from the group consisting of a carbon nanotube, a haloisot nanotube, a carbon nanofiber, a silica nanotube, and a mixture thereof.

According to another embodiment of the present invention, the MOF is formed by a metal selected from the group consisting of copper, zinc, nickel, and alloys thereof, such as benzene-1,3,5-tricarboxylic acid (BTC) A dicarboxylic acid, acetic acid, and mixtures thereof.

According to another embodiment of the present invention, the vacuum treatment may be performed for 10 minutes to 30 minutes, and may be repeated 1 to 5 times.

According to another embodiment of the present invention, recovery of the nanotubes from the solution can be performed by precipitating the nanotubes by centrifugation.

According to another embodiment of the present invention, the heating may be carried out at a temperature of 25 ° C to 200 ° C for 6 to 24 hours.

According to another embodiment of the present invention, the nanotubes may be mesoporous nanotubes having an average diameter of 2 nm to 50 nm and an average length of 50 nm to 2 μm.

The present invention also provides a nanotube-MOF composite comprising the nanotube and the MOF supported on the lumen of the nanotube.

According to the present invention, it is possible to produce a nanotube-MOF composite with high efficiency even when purification of the resultant product is easy after synthesis, MOF can be uniformly filled in the mold, and a separate chemical treatment is not required in the mold, Based nanotube-MOF composite and a nanotube-MOF composite produced from the same. In addition, the resulting composite exhibits excellent stability to water and exhibits unique gas adsorption characteristics due to the presence of micropores and mesopores.

1 is a schematic process diagram of a method of manufacturing a nanotube-MOF composite according to the present invention.
2A to 2D are diagrams respectively showing a TEM image 2a for the composite according to the present invention, an EDS element mapping image 2b for Al, an EDS element mapping image 2c for S and an EDS element mapping image 2c for Cu 2d.
3A and 3B are TEM images of pure HNT 3a and HKUST-1 @ HNT 3b, respectively.
4 is a graph showing XRD patterns for pure HNT, HKUST-1 @ HNT and bulk HKUST-1.
5a and 5b are graph 5a showing adsorption-desorption isotherms for pure HNT, HKUST-1 @ HNT, and bulk HKUST-1 and graph 5b showing BJH pore size distribution, respectively The filled-in figure indicates the adsorption cycle, while the hollow figure indicates the desorption cycle.

Hereinafter, the present invention will be described in more detail.

In the present invention, a new X-situ synthesis method capable of exclusively and evenly distributing MOFs only inside the lumens of mesoporous nanotubes while effectively solving the above-mentioned problems through capillary phenomenon of nanotubes is provided. The present invention provides a composite structure comprising a mesoporous nanotube and a metal-organic structure supported on the lumen of the mesoporous nanotube.

Specifically, in the present invention, a metal-organic structure is uniformly supported between nanotubes by performing a vacuum process in a solution state, and then a solvent thermal synthesis method is performed by an X-ray diffraction method after the supporting process. At this time, Serves not only as a micro vial, but also as a template. By the capillary action of the nanotubes in the course of the reaction, the precursor is present only in the lumen of the mesoporous nanotubes. That is, in the present invention, the synthesis reaction of the metal-organic structure in solution is not in-situ, but the precursor solution is introduced into the micro-cavity of the nanotube, and then the synthesis of the metal- (Ex-situ), it is possible to effectively overcome the limitations of the in-situ synthesis method described above.

In addition, the X-situ synthesis method according to the present invention is also different from the conventional synthesis method using the capillary phenomenon of carbon nanotubes reported in the prior art. In the conventional methods, And the reaction is focused on generating crystals by simple evaporation of the solvent. However, in the case of the present invention, the precursor solution remains in the nanoreactor for a long time, and the synthesis reaction of the metal- It is because it proceeds.

Therefore, in the present invention,

FIG. 1 is a schematic process diagram of a method of manufacturing a nanotube-MOF composite according to the present invention. Referring to FIG. 1, in the present invention, a step of uniformly dispersing a nanotube material in a MOF precursor solution is performed. This dispersion process can be performed, for example, by adding the solution to the solution of the nanotube and the MOF precursor, and then subjecting the resultant mixture to treatment such as sonication.

As the nanotubes usable in the present invention, nanotubes having various materials and shapes can be used. Examples of the carbon nanotubes and non-carbon nanotubes include single wall or multiwall carbon nanotubes, , Carbon nanofibers, silica nanotubes, and mixtures thereof. For example, in the case of the Halloysite nanotubes, a 1: 1 aluminosilicate multiwalled nanotube similar in composition to kaolinite (Al ₂ Si ₂ O ₅ (OH) ₄ ) has a large surface area And has a cylindrical structure. The morphology itself is similar to multi-walled carbon nanotubes, but the internal aluminol (Al-OH) and the external siloxane (Si-O-Si) have different functionalities, which often lead to drug delivery systems and biopharmaceuticals It is widely used for applications. Suitable nanotubes for use in the present invention may be mesoporous nanotubes having an average diameter of between 2 nm and 50 nm and an average length of between 50 nm and 2 μm.

Also, in the case of MOF, that is, a metal-organic structure, various metal ions or metal clusters may form coordination bonds with various organic ligands. For example, copper, zinc, nickel, And their alloys are coordinated with organic ligands selected from the group consisting of benzene-1,3,5-tricarboxylic acid (BTC), benzene-1,4-dicarboxylic acid, acetic acid, May be used. The synthesis of the MOF can be performed by subjecting the precursor solution for synthesizing the MOF to a solvent thermal synthesis process. The type of the appropriate precursor solution and the heat-synthesis conditions of the solvent can be selected according to the MOF to be synthesized .

Next, after the dispersion process, a process for supporting the MOF precursor solution in the lumen of the nanotube is performed. In the present invention, a vacuum is applied to the mixture solution of the MOF precursor and the nanotube to perform the supporting process. By this vacuum treatment process, the MOF precursor is uniformly supported in the inside of the lumen of the nanotube, and MOF The precursor is maintained in a state of being supported by the capillary force inside the lumen of the nanotube. For example, the vacuum treatment may be performed for 10 minutes to 30 minutes, and may be repeated one to five times to allow the MOF precursor to be supported within the lumens of more nanotubes.

After the MOF precursor is supported on the lumens of the nanotube by the above process, the MOF precursor-carrying nanotube is separated and recovered from the mixture solution. This can be carried out by precipitating the MOF precursor-carrying nanotube present in a solid state in a mixture solution by a method such as centrifugation.

The individual nanotubes in a separated state are shown in an enlarged state at the lower right end of FIG. 1, and it can be seen that the MOF precursor solution is held by the capillary force in the lumen of the nanotube. Therefore, in the next step, a process of synthesizing MOF from the supported MOF precursor solution is performed. In the present invention, since this synthesis process is performed in the state of being supported on the lumen of the nanotube, not in the MOF precursor solution, It is possible to synthesize MOF by the so-called X-situ method. The MOF may be synthesized from the MOF precursor solution by a known solvent solvothermal synthesis. In the synthesis process, the precursor solution may be heated at a temperature ranging from room temperature to the decomposition temperature of the ligand, At a temperature of 200 [deg.] C, i.e., at a temperature of 25 [deg.] C to 200 [deg.] C, for 6 to 24 hours or more.

When the MOF crystals are produced from the MOF precursor solution by this heating process, finally, the complex of the present invention can be manufactured after removing the residual MOF precursor solution through a simple cleaning process. Accordingly, it is possible to omit the process of purifying or separating the final product, which is a complex process that is required in the conventional in-situ synthesis method, in the present invention.

Meanwhile, the present invention also provides a nanotube-MOF composite produced by the above method, which comprises a nanotube and a MOF supported on the lumen of the nanotube.

Since the nanotube-MOF composite according to the present invention exhibits excellent stability to water and exhibits unique gas adsorption characteristics due to the existence of micropores and mesopores, as can be seen from the experimental data of the following examples, It is possible to provide an excellent catalyst capable of efficiently performing an oxygen reduction reaction for a fuel cell.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are intended to assist the understanding of the present invention and should not be construed as limiting the scope of the present invention.

Materials and methods

Purified hydrated halo-site nanotubes (HNT) were purchased from Applied Minerals Inc., USA. Copper nitrate trihydrate (Daejung, 99% or more), 1,3,5-benzenetricarboxylic acid (BTC, Lancaster, 98%), methanol (Daejung, 99.8% or more), dimethylsulfoxide (DMSO, Daejung, %) Were used without further purification. Powder X-ray diffraction (XRD) patterns were collected on D / MAX RINT 2000 through Cu Kα irradiation (λ = 1.5406 Å). The diffraction pattern was recorded at a scan rate of 2 ° per minute at 3 ° to 40 °. Transmission electron microscopy (TEM, JEOL JEM-2100F) images were obtained for pure HNT and HKUST-1 @ HNT at a driving voltage of 200 kV. Sample drops (0.1 mg / mL) were added dropwise onto a 200-mesh copper Formvar carbon coated TEM lattice.

Immediately after completion of the synthesis, energy-dispersive X-ray spectroscopy (EDS, Oxford Instruments) was performed on HKUST-1 @ HNT. In contrast to previous TEM sampling, the HKUST-1 @ HNT powder was transferred directly to the grating. In order to avoid confusion with the EDS analysis, a Nickel Formvar carbon film was used for EDS measurements. Nitrogen adsorption-desorption isotherm curves for each sample were measured by a volume gas adsorber (BEL JAPAN Inc., BELSORP-Mini II).

The total specific surface area and pore volume of each sample were measured using the Brunauer-Emmett-Teller (BET) method and the meso / macropore size distribution of the sample and the pore size of each pore were measured using the Barrett-Joyner-Halenda (BJH) Volume and surface area were measured. A relative pressure of 10 ^-4 to 0.99 was applied, and the operating temperature was 77 K. Prior to each measurement, samples were activated by heating at 433 K.

Synthesis process

1) Manufacture of Bulk HKUST-1

HKUST-1, a metal-organic structure, was the first copper-based MOF reported in 1999 by researchers from the Hong Kong University of Science (Chui, SS-Y. et al. Science 1999, 283, 1148). The synthesis of HKUST-1 was carried out according to previously reported literature (R. Ameloot, E. Gobechiya, H. Uji-I, A. Martens, J. Hofkens, L. Alaerts, BF Sels, D. De Vos, Adv. Mater. 22 (2010) 2685-2688).

Briefly, 0.58 g of benzene-1,3,5-tricarboxylic acid (BTC) was mixed with 5 g of DMSO and then 1.22 g of Cu (NO ₃ ) ₂ .3H ₂ O Was added slowly to prepare a precursor solution in a 20 mL vial. The solution was in a clear state and was reported to remain stable for at least 8 hours at room temperature. The solution was then heated at 423 K for 12 hours. After centrifugation of the resulting solution, the supernatant precursor was discarded and the remaining solid was washed with pure DMSO. The product was stored in methanol for at least 24 hours and then supplemented with methanol for further experiments.

2) Manufacture of HKUST-1 @ HNT

A precursor solution for HKUST-1 was prepared according to the protocol described above. HNT powder was added to the solution at a concentration of 1 mg / mL. The mixture was sonicated for 2 hours to evenly disperse the HNT in the precursor solution.

The precursor was then vacuum loaded into the HNT lumen by evacuation of the mixture for 20 minutes. This process exhausted the air occupying the HNT lumen, thus filling the voids with the precursor. To ensure maximum loading of the solution, the procedure was repeated three times and the resulting mixture was centrifuged. The supernatant was stored in vials for reuse. The precipitate was transferred to another vial and heated at 423 K for 12 hours. The post-treatment of the product was carried out in the same manner as in HKUST-1 described above.

Results and review

1) Energy-dispersive X-ray spectroscopy (EDS)

In order to confirm the capillary phenomenon of HNT, STEM-EDS was performed to confirm the element composition immediately after completion of the reaction. The reason for using this method is that the elemental mapping images obtained after completion of the reaction can provide clues as to where the reaction precursors were present during the reaction.

Figure 2 shows an EDS element mapping image for the product immediately after the reaction is complete. Since the aluminum atoms are constituent elements of the HNT, it is judged that the Al distribution has the same shape as the original TEM image (Fig. 2B). The distribution of sulfur atoms (from the solvent DMSO in the precursor solution) and the distribution of copper atoms (from the copper nitrate trihydrate solute in the precursor solution) were similar to those for Al, indicating that the precursor solution was contained in the nanotubes during the reaction . Crystal formation was not observed outside the nanotubes during the entire time of the EDS measurement. This is a strong evidence to disprove the capillary phenomenon of nanotubes. Capillary phenomena have been reported for some similar nanotubes, particularly carbon nanotubes (CNTs) (SC Tsang, YK Chen, PJF Harris, MLH Green, Nature 372 (1994) 159-162; E. Dujardin, TW Ebbesen , H. Hiura, K. Tanigaki, Science 265 (1994) 1850-1852; JY Chen, A. Kutana, CP Collier, KP Giapis, Science 310 (2005) 1480-1483).

However, there is no existing literature reporting that a selective solvent thermal reaction is performed while the capillary force of the nanotube remains in solution. In addition to the above methods, the even distribution of the tubes and the complete separation of the synthesized material is ensured by the fact that the precursor is evenly loaded by the vacuum process. Furthermore, since no chemical reaction is required between the mold surface and the precursor, it is applicable to a variety of materials and mold combinations that do not interact with each other.

2) Transmission electron microscope (TEM)

Figure 3 shows a TEM image of pure HNT and HKUST-1 @ HNT. After synthesis, the hollow HNT lumen is filled with HKUST-1, and the interface between the lumen and the HNT wall is shown in the figure as transparent. The area representing the HNT lumen is marked by a much darker color in contrast to the wall. It can be seen that the atoms that comprise the material filling the lumen of the nanotube have a higher atomic weight than those on the wall, since the region containing atoms with relatively high atomic masses appears shaded in the TEM image. Since copper has a higher atomic weight than silicon or aluminum, it can be seen that the elements present in the lumen are copper, which is derived from the internally synthesized HKUST-1. During the TEM scanning, no isolated HKUST-1 crystals could be observed and this also confirmed the capillary phenomenon of the HNT.

3) Powder X-ray diffraction (XRD)

Crystallinity for each sample was determined by powder XRD. Figure 4 shows characteristic reflections of each sample. The bulk HKUST-1 exhibits distinct reflections at (200), (220), and (222), which is consistent with the previously reported HKUST-1 (R. Ameloot, E. Gobechiya, H. Uji- I, A. Martens, J. Hofkens, L. Alaerts, BF Sels, D. De Vos, Adv. Mater. 22 (2010) 2685-2688). Pure HNT also showed a unique peak at 2θ = 8.75 °, due to the wall spacing of the hydrated HNT originally filled with water. Reflections at 2? = 8.75 ° for HNTs were shifted to reflections at 2θ = 7.64 ° for HKUST-1 @ HNT. These shifts are the result of a solvent exchange process after the reaction. This is due to the methanol used as cleaning and activating agent, which is due to the fact that such methanol is inserted into and widening the wall spacing, HNT often allows the insertion of various solvents, causing expansion or contraction of wall spacing (Y. Komori, Y. Suguhara, K. Kuroda, Chem.Mater. 11 (1999) 3-6).

HKUST-1 @ HNT represents a striking difference. Although the peak arrangement of HKUST-1 @ HNT is similar to that of bulk HKUST-1, the (200) and (220) reflections are significantly smaller, while the (222) reflections remain the same. This means that the product is not a simple mixture of HNT and HKUST-1. The change in peak intensity indicates preference in the growth direction of HKUST-1 @ HNT, that is, (222) direction. Studies by A. Sachse et al. Also reported similar trends to HKUST-1, which reported that HKUST-1 caused growth restriction when synthesized in silica monolith mesopores (A. Sachse , R. Ameloot, B. Coq, F. Fajula, B. Coasne, D. De Vos, A. Galarneau, Chem. Comm. 48 (2012) 4749-4751).

This change observed in the present invention can be attributed to the growth of the HKUST-1 crystal along the longitudinal axis of the HNT. In connection with this, researchers such as R. Ameloot et al. Have reported that when HKUST-1 crystallizes in a confined space between a PDMS stamp and a silicon wafer, the growth tends to proceed along the (222) direction A. Gobchiya, H. Uji-I, A. Martens, J. Hofkens, L. Alaerts, BF Sels, D. De Vos, Adv. Mater. 22 (2010) 2685-2688).

4) Volume N ² adsorption / desorption measurement

Characteristic adsorption characteristics of the samples were analyzed by measuring the volume N ² adsorption, and the isotherm curves are shown in FIG. 5A. MOFs such as HKUST-1 typically exhibit an IUPAC Type I isotherm, which is due to its microporous structure. Pure HNT represents a Type IV isotherm curve, which is due to its mesopore structure. The HKUST-1 @ HNT isotherm curves appeared as a combination of Type I and Type IV isotherm curves from which we can see that the sample has both micropores and mesopores.

Figure 5b shows the pore size distribution of each sample, as measured by the Barrett-Joyner-Halenda (BJH) method, which is a method applicable to mesopore and macropore areas. Bulk HKUST-1 has only micropores (<2 nm) and does not show any signal in the BJH pore size distribution. Two peaks near 15 nm and 28 nm represent the inner diameter of the pure HNT (P. Yuan, D. Tan, FA Bergaya, W. Yan, M. Fan, D. Liu, H. He, Clays Clay Min. 60 (2012) 561-573). In this area, a decrease in pore volume was observed for the logarithmic change in pore diameter (dV _p / dlogd _p ) as compared to pure HNT. This result implies that the hysteresis of HNT is lost by synthesized HKUST-1 which occupies the lumen. These results are consistent with the change in surface area as calculated by the non-pore volume and the BET method, as shown in Table 1.

In the above table, V _meso was calculated by the BJH method and V _micro was calculated from the values of BET total pore volume and BJH pore volume.

The pore diameter also decreases from 15 to 28 nm for pure HNT to 14 to 21 nm for HKUST-1 @ HNT. This is due to the reduction of the effective radius by the filling material and is additional evidence of the presence of HKUST-1 in the lumen. As expected, HKUST-1 @ HNT is thermally stable, and thermogravimetric analysis (TGA) results show that the mass loss of HKUST-1 @ HNT is greater than the values for bulk HKUST-1 and pure HNT Respectively.

The armoring effect was also observed, indicating that HKUST-1 @ HNT exhibited excellent stability to water, as opposed to the rapid breakdown of bulk HKUST-1 in water.

In summary, in the present invention, a method of synthesizing MOFs exclusively and exclusively within the nanotubes is proposed. The method according to the present invention evenly loads the precursor solution into the lumen of the nanotube and then keeps the precursor solution loaded by the capillary force of the nanotube during the reaction. As an example, when HKUST-1 was synthesized inside the HNT lumen, the growth of HKUST-1 was restricted to only one direction along the longitudinal axis of the nanotube. The resulting product, HKUST-1 @ HNT, exhibited improved stability to water and exhibited unique gas adsorption characteristics due to the micropores and mesopores present in the product. The method according to the present invention does not require any chemical interaction and thus can be applied to various MOF precursors and mesoporous sintered nanotube combinations. Therefore, the present invention suggests that synergistic effects can be obtained by synthesizing various hybrid nanotubes.

Claims

Uniformly dispersing the nanotubes in a solution of a metal-organic structure (MOF) precursor;
Supporting the solution of the MOF precursor on the lumen of the nanotube by applying a vacuum treatment to the solution; And
Recovering the nanotubes from the solution, heating the nanotubes, and then washing the nanotubes.

The method according to claim 1,
Wherein the nanotube is a nanotube selected from the group consisting of a carbon nanotube, a haloisot nanotube, a carbon nanofiber, a silica nanotube, and a mixture thereof.

The method according to claim 1,
Wherein the metal selected from the group consisting of copper, zinc, nickel and alloys thereof is at least one selected from the group consisting of benzene-1,3,5-tricarboxylic acid (BTC), benzene-1,4-dicarboxylic acid, And forming a coordination bond with an organic ligand selected from the group consisting of a metal complex and a metal complex.

The method according to claim 1,
Wherein the vacuum treatment is performed for 10 minutes to 30 minutes and is repeatedly performed 1 to 5 times.

The method according to claim 1,
Wherein the recovery of the nanotubes from the solution is performed by precipitating the nanotubes by centrifugation.

The method according to claim 1,
Wherein the heating is performed at a temperature of 25 ° C to 200 ° C for 6 hours to 24 hours.

The method according to claim 1,
Wherein the nanotubes are mesoporous nanotubes having an average diameter ranging from 2 nm to 50 nm and an average length ranging from 50 nm to 2 mu m.

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