Gas storage tank

Abstract

An object of the present invention is to provide a gas storage container that is easy to transport and install. The gas storage container according to the present invention has flat upper and lower surfaces and is stackable. The gas storage container according to the present invention may also include a casing that has flat upper and lower surfaces and is stackable, and a gas cylinder installed in the casing. [Selected Figure] Figure 2

Description

[Technology Field]

[0001] The present invention relates to a gas storage container having a specific shape. [Background technology]

[0002] Traditionally, heavy, bottle-shaped gas cylinders have been commonly used. However, these gas cylinders occupy a large volume, making them difficult to transport and install, and thus not easy to handle. Furthermore, these gas cylinders do not contribute to aesthetic appeal. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2015-178906 [Overview of the project] [Problems that the invention aims to solve]

[0004] The present invention aims to provide a gas storage container that is easy to transport and install. [Means for solving the problem]

[0005] Examples of the present invention are as follows: [1] A gas storage container with a flat top and bottom surface that can be stacked vertically. [2] The gas storage container described in [1], which is prismatic in shape. [3] The gas storage container described in [2], which is a rectangular prism, a pentagonal prism, or a hexagonal prism. [4] A gas storage container as described in [3], which is rectangular or cubic in shape. [5] A gas storage container according to any one of [1] to [4], wherein a gas outlet is provided on at least one side. [6] The gas storage container according to [5], having a recess on at least one side, wherein the outlet is provided in the recess. [7] A gas storage container according to any of [1] to [6], which is provided with a gripping portion. [8] A gas storage container according to any of [1] to [7], wherein the inner surface is spherical, cylindrical, or elliptical. [9] A gas storage container according to any one of [1] to [8], comprising a casing having a flat top and bottom and capable of being stacked vertically, and a gas cylinder installed in the casing.

[10] A gas storage container according to any one of [1] to [9], further comprising a gas remaining amount measurement module.

[11] The gas storage container according to [9], further comprising a gas remaining amount measurement module between the casing and the gas cylinder.

[12] The gas storage container according to

[10] or

[11] , wherein the gas remaining amount measurement module includes a temperature sensor.

[13] The gas storage container according to any one of

[10] to

[12] , wherein the gas remaining amount measurement module is configured to be capable of wireless communication.

[14] The gas storage container according to any one of

[10] to

[13] , wherein the gas remaining amount measurement module is configured to be capable of GPS communication.

[15] The gas storage container according to any one of

[10] to

[14] , further including a porous material inside.

[16] The gas storage container according to

[15] , wherein the porous material is a metal organic framework.

Advantages of the Invention

[0006] According to the present invention, it is possible to provide a gas storage container that is easy to transport and install.

Brief Description of the Drawings

[0007]

FIG. 1

FIG. 2

FIG. 3

FIG. 4

FIG. 5

FIG. 6

[0008] The gas storage container according to the present invention has a flat top and bottom surface and can be stacked vertically. By adopting such a configuration, the transportation and installation of the gas storage container become easy and efficient. An example of such a gas storage container will be described below.

[0009] Figure 1 is a perspective view showing a gas storage container according to one aspect of the present invention. Figure 2 is a cross-sectional view of the gas storage container shown in Figure 1. Figure 3 is a perspective view showing gas storage containers according to one aspect of the present invention stacked vertically.

[0010] The gas storage container 1 shown in Figures 1 and 2 is cubic in shape and has a top surface 10, a bottom surface 20, and four sides 30. Both the top surface 10 and the bottom surface 20 are flat and have the same shape. This allows the gas storage containers 1 to be stacked vertically. Figure 3 shows an example of this, where gas storage containers 1A to 1C are stacked.

[0011] The side surface 30 of the gas storage container 1 is typically equipped with a gas outlet 32. A recess 34 is provided in the side surface 30, and the outlet 32 ​​is located within it. Adopting this configuration reduces the volume occupied by the gas storage container 1, making it easier to transport and handle. The outlet 32 ​​usually also serves as the gas inlet.

[0012] The discharge port 32 is typically equipped with a gas level measurement module (not shown). Preferably, the gas level measurement module is configured to enable wireless communication. The gas level measurement module may also be configured to enable GPS communication. Adopting such a configuration makes it possible to remotely manage the gas level in the gas storage container 1.

[0013] Figure 4 is a conceptual diagram showing an example of the configuration of a gas remaining amount measurement module. The gas remaining amount measurement module shown in Figure 4 is an IoT module and comprises a pressure sensor, a temperature sensor, an analog-to-digital (A / D) converter connected to both sensors, and a central processing unit (CPU) connected to the A / D converter. The CPU is further connected to a wireless communication module configured for wireless communication and a GPS communication module configured for GPS communication. The wireless communication module is used, for example, to transmit measurement data to a monitoring PC or tablet. In the example shown in Figure 4, the monitoring PC or tablet displays information such as temperature (25°C), location information (135.405°E / 35.010°N), and pressure (9.85MPa). For example, a Bluetooth® communication module can be used as the wireless communication module. By using such a gas remaining amount measurement module, users can easily find out the remaining amount and location information of gas storage containers. This also makes inventory management and distribution management of gas storage containers easier.

[0014] The inner surface 70 of the gas storage container 1 has a cubic shape that is almost identical to its outer surface. By adopting this configuration, the gas storage capacity of the gas storage container 1 can be maximized.

[0015] There are no particular restrictions on the material of the gas storage container 1. For example, the gas storage container 1 may be made of metal or an alloy. Alternatively, the gas storage container 1 may be made of fiber-reinforced plastic, or a combination of fiber-reinforced plastic and metal or an alloy. Alternatively, the gas storage container 1 may be made of duralumin. The material of the gas storage container 1 can be appropriately selected considering factors such as moldability and weight.

[0016] Figure 5 is a perspective view showing a gas storage container according to another aspect of the present invention. The gas storage container 1 shown in Figure 5 has the same configuration as the gas storage container 1 shown in Figure 1, except that it has a larger chamfer. Adopting such a configuration improves the pressure resistance performance of the gas storage container 1 and gives the user a softer appearance. Note that the gas storage container 1 does not necessarily have to have the chamfer shown in Figures 1 and 5.

[0017] Figure 6 is a perspective view showing a gas storage container according to another aspect of the present invention. The gas storage container 1 shown in Figure 6 has the same configuration as the gas storage container 1 shown in Figure 5, except that it further has a gripping portion 100 on its upper surface. By adopting this configuration, the transport of the gas storage container 1 becomes even easier.

[0018] In the gas storage container 1 shown in Figure 6, a recess 102 is provided on the top surface 10. This ensures that the grip portion 100 does not protrude from the top surface 10. By adopting this configuration, stacking the gas storage containers 1 in the vertical direction becomes easier. The grip portion 100 may also be provided in a foldable manner on the top surface 10.

[0019] The gripping portion 100 may be provided on a surface other than the top surface of the gas storage container 1. In other words, the gripping portion 100 may be provided on the outside of the gas storage container 1. For example, the gripping portion 100 may be provided on the outer surface of the gas storage container 1, or on the outer corner of the gas storage container 1.

[0020] Figure 7 is a perspective view showing a gas storage container according to another aspect of the present invention. The gas storage container 1 shown in Figure 7 has the same configuration as the gas storage container 1 shown in Figure 1, except that the side surface 30 on which the outlet 32 ​​is provided does not have a recess. By adopting this configuration, it is generally possible to store a larger amount of gas compared to the configuration shown in Figure 1.

[0021] Figure 8 is a perspective view showing a gas storage container according to another aspect of the present invention. The gas storage container 1 shown in Figure 8 has the same configuration as the gas storage container 1 shown in Figure 1, except that the top surface 10 is also provided with an outlet 12 and a recess 14. By adopting such a configuration, it is possible to discharge or introduce gas from both the top surface 10 and the side surface 30. Furthermore, by connecting the outlets of multiple gas storage containers 1, it is possible to increase the effective capacity of the gas storage containers 1, for example. As explained with reference to Figure 7, the recess 14 may be omitted.

[0022] Figure 9 is a perspective view showing a gas storage container according to another aspect of the present invention. The gas storage container 1 shown in Figure 9 has the same configuration as the gas storage container 1 shown in Figure 8, except that an outlet 42 and a recess 44 are also provided on another side 40. Adopting such a configuration makes it possible to discharge or introduce gas from multiple sides. Furthermore, by connecting the outlets of multiple gas storage containers 1, it is possible to increase the effective capacity of the gas storage containers 1, for example. As explained with reference to Figure 7, the recess 44 may be omitted. In addition, outlets (and recesses) may be further provided on the bottom surface and other sides.

[0023] Figures 10 and 11 are perspective views showing gas storage containers according to other embodiments of the present invention. The gas storage container 1 shown in Figure 10 has the same configuration as the gas storage container 1 shown in Figure 1, except that it is a regular hexagonal prism shape. The gas storage container 1 shown in Figure 111 has the same configuration as the gas storage container 1 shown in Figure 1, except that it is a regular pentagonal prism shape. Even with these shapes, the gas storage container 1 is easy to transport and install.

[0024] The shape of the gas storage container 1 is not particularly limited, as long as the top and bottom surfaces are flat and it can be stacked vertically. The gas storage container 1 is, for example, cylindrical or prismatic, and preferably a quadrangular, pentagonal, or hexagonal prism. If the gas storage container 1 is prismatic, it is preferably a regular polygonal prism. The gas storage container 1 is more preferably a rectangular parallelepiped or cubic, and particularly preferably a cubic.

[0025] The shape of the inner surface of the gas storage container 1 is, for example, almost identical to the shape of the outer surface, as shown in Figure 2. The shape of the inner surface of the gas storage container 1 may differ from the shape of the outer surface. For example, the inner surface of the gas storage container 1 may be spherical, cylindrical, or elliptical. By adopting such a configuration, for example, the pressure resistance performance of the gas storage container 1 can be improved.

[0026] Figure 12 is a perspective view showing a gas storage container according to another embodiment of the present invention. Figure 13 is a cross-sectional view of the gas storage container shown in Figure 12. The gas storage container 1 shown in Figures 12 and 13 has the same configuration as the gas storage container 1 shown in Figures 1 and 2, except that the inner surface 70 is spherical. By adopting such a configuration, for example, the pressure resistance performance of the gas storage container 1 can be improved.

[0027] Figure 14 is a perspective view showing a gas storage container according to another embodiment of the present invention. Figure 15 is a cross-sectional view of the gas storage container shown in Figure 14. The gas storage container 1 shown in Figures 14 and 15 has the same configuration as the gas storage container 1 shown in Figures 1 and 2, except that the inner surface 70 is cylindrical. By adopting such a configuration, for example, the pressure resistance performance of the gas storage container 1 can be improved.

[0028] The gas storage container according to the present invention may comprise a casing with a flat top and bottom surface that can be stacked vertically, and a gas cylinder installed inside the casing. In this case, it is possible to provide a gas storage container that is easy to transport and install, regardless of the shape of the gas cylinder. In this case, the material of the casing and the material of the gas cylinder may be different from each other. Therefore, by optimizing the material of the casing and the material of the gas cylinder, it is possible to adjust the overall strength, weight, pressure resistance, and appearance of the gas storage container. In this case, for example, the material of the gas cylinder can be one of those previously exemplified as materials for gas storage containers. On the other hand, as the material of the casing, in addition to those previously exemplified as materials for gas storage containers, plastics, metals, alloys, etc., can be used as appropriate.

[0029] Figure 16 is a perspective view showing a gas storage container according to another aspect of the present invention. The gas storage container 1 shown in Figure 16 comprises a casing 200 and a gas cylinder 300 installed inside it. The casing 200 is substantially cubic in shape and made of plastic. Grips are provided at the outer corners of the casing 200. The gas cylinder 300 is made of fiber-reinforced plastic and is installed inside the casing 200. The outlet of the gas cylinder 300 is exposed to the outside through the casing 200. By adopting such a configuration, it is possible to provide a gas storage container that is easy to transport and install while enhancing pressure resistance.

[0030] Furthermore, if the gas storage container consists of a casing and a gas cylinder, the gas remaining amount measurement module described above may be installed between the casing and the gas cylinder. In this case, the gas remaining amount measurement module becomes less visible from the outside, and the aesthetic appearance is less likely to be compromised.

[0031] The gas storage container according to the present invention may contain a porous material inside. This porous material may be filled in such a way that the gas storage container satisfies the following conditions at 298K for at least one type of gas: that is, the gas content (G) at 1 MPa.1M ) and the gas content (G 0.1M ) and the difference (Δ 1M =G 1M -G 0.1M ) is the gas content (g 1M ) at 1 MPa and the gas content (g 0.1M ) at 0.1 MPa, and the difference (δ 1M =g 1M -g 0.1M ) is more than twice that. That is, the gas storage container according to the present invention may satisfy Δ 1M / δ 1M ≧2 for at least one type of gas at 298K.

[0032] Incidentally, the gas content (G 0.1M ) is substantially the gas content at atmospheric pressure. That is, this value serves as a guide for the limit value at which the gas storage container can release gas without depressurization.

[0033] Generally, gas cylinders are filled with gas up to a high pressure of 14.7 MPa. This is because, in the case of conventional gas cylinders, the pressure and the gas storage amount are directly proportional, so a sufficient amount of gas cannot be stored without a high pressure. On the other hand, when using a gas storage container that satisfies the above conditions, a high gas storage amount can be achieved at a relatively low pressure.

[0034] The gas storage amount G total of the gas storage container according to this embodiment can be calculated by the following formula. [Equation 1]

[0035] Here, G ext is the gas storage amount in the region where the porous material is not filled. G pore is the storage amount of gas with normal density that has entered the pores of the porous material. G excess is the excess adsorption amount of gas by the porous material.

[0036] G ext can be calculated by the following formula. [Math 2]

[0037] Here, F is the packing density (%) of the porous material. g is the gas density (mol / L) at the same pressure. ext The contribution by decreases as the packing density F of the porous material increases. For example, when F=100%, G ext = 0 mol / L

[0038] G pore This can be calculated using the following formula. [Math 3]

[0039] Here, F is the packing density (%) of the porous material. ε is the void ratio of the porous material, and ρ (g / cm³) is the density of the porous material. 3 ) and the pore volume V of the porous material p (cm 3 This value is obtained by multiplying it by ( / g).

[0040] G excess This can be calculated using the following formula. [Math 4]

[0041] Here, F is the packing density (%) of the porous material. A is the amount of gas adsorbed by the porous material (cm³) determined by adsorption measurement. 3 (STP) / g) where ρ is the density of the porous material (g / cm³). 3 ) Note that this calculation formula assumes the gas is an ideal gas in STP with a volume per mole (22.7 L / mol).

[0042] As can be seen from the above equation, gas storage amount G total In order to increase G excess It is important to increase the size of G excess To increase this, it is preferable to increase the packing density F of the porous material and to use a porous material with a large gas adsorption capacity A.

[0043] The packing density F(%) of the porous material is not limited as long as the above conditions are met, but it should be, for example, 60% or more, preferably 65% ​​or more, and more preferably 70% or more. In such cases, the effect of increasing the gas storage capacity by filling with porous material becomes more pronounced. Although the upper limit of the packing density is 100%, the packing density may be slightly lower from the viewpoint of gas filling efficiency and heat dissipation. For example, the packing density of the porous material may be 99% or less. Furthermore, the packing density may be further lowered to account for the increase in weight of the gas storage container due to the weight of the porous material itself.

[0044] As described above, the gas storage container according to this embodiment has a Δ for at least one type of gas at 298K. 1M / δ 1M It satisfies ≥2. 1M / δ 1M For example, it is 4 or more, preferably 6 or more, more preferably 8 or more, and particularly preferably 10 or more.

[0045] The gas storage container according to this embodiment has a Δ for at least one type of gas at 298K. 5M / δ 5M It is preferable that the condition ≥ 1.5 is satisfied. 5M / δ 5M For example, it is 1.8 or higher, preferably 2 or higher, more preferably 4 or higher, and particularly preferably 5 or higher.

[0046] The gas storage container according to this embodiment has a Δ for at least one type of gas at 298K. 10M / δ 10M It is preferable that the condition ≥ 1.2 is satisfied. 5M / δ 5M For example, it is 1.5 or more, preferably 1.8 or more, more preferably 2 or more, and particularly preferably 3 or more.

[0047] The gas storage container according to this embodiment has a Δ for at least one type of gas at 298K. 5M / δ 14.7M It is preferable that the condition ≥ 0.3 is satisfied.5M / δ 14.7M Δ is, for example, 0.5 or more, preferably 0.6 or more, more preferably 0.8 or more, and particularly preferably 1 or more. 5M / δ 14.7M If the value is 1 or greater, the gas storage container can store an amount of gas equivalent to or greater than that of an empty cylinder at 14.7 MPa at a low pressure of 5 MPa.

[0048] The gas storage container according to this embodiment has a Δ for at least one type of gas at 298K. 1M / δ 14.7M It is preferable that the condition ≥ 0.1 is satisfied. 1M / δ 14.7M For example, it is 0.2 or more, preferably 0.4 or more, more preferably 0.6 or more, even more preferably 0.8 or more, and particularly preferably 1 or more. 1M / δ 14.7M If the value is 1 or greater, the gas storage container can store an amount of gas at a low pressure of 1 MPa that is equivalent to or greater than that of an empty cylinder at 14.7 MPa.

[0049] Examples of porous materials that can be used include metal-organic frameworks (hereinafter also referred to as MOFs), activated carbon, zeolites, and mesoporous silica. Using metal-organic frameworks as the porous material is particularly preferable. Furthermore, multiple types of porous materials may be used in combination.

[0050] When using metal-organic structures as porous materials, there are no particular restrictions on their type. By appropriately combining the type and coordination number of metal ions with the type and topology of polydentate ligands, metal-organic structures with a desired structure can be manufactured.

[0051] Examples of metal elements constituting the metal-organic structure include alkali metals (Group 1), alkaline earth metals (Group 2), and any element belonging to transition metals (Groups 3 to 12). The polydentate ligands constituting the metal-organic structure are typically organic ligands, such as carboxylic acid anions and heterocyclic compounds. Examples of carboxylic acid anions include dicarboxylic acids or tricarboxylic acids. Specifically, examples include anions of citric acid, malic acid, terephthalic acid, isophthalic acid, trimesyl acid, and their derivatives. Examples of heterocyclic compounds include bipyridine, imidazole, adenine, and their derivatives. Alternatively, the ligand may be an amine compound, a sulfonate anion, or a phosphate anion. The metal-organic structure may further contain monodentate ligands.

[0052] The combination of metals and ligands constituting the metal-organic structure can be appropriately determined according to its function and the desired pore size. The metal-organic structure may contain two or more metal elements and two or more ligands. Furthermore, the metal-organic structure may be surface-modified with polymers or the like.

[0053] Specific examples of metal-organic structures include those listed in Table 1 of the reference (Yabing He et al. Methane Storage in Metal-Organic Frameworks, Chem Soc Rev, 2014). Alternatively, those listed in other references (Chem. Sci., 2014, 5, 32-51) may be used. Furthermore, the metal-organic structures shown in Tables 1 to 3 below may be used. Note that these are not restrictive listings, and other metal-organic structures may also be used.

[0054] [Table 1]

[0055] [Table 2]

[0056] [Table 3]

[0057] There are no particular restrictions on the shape of the porous material. For example, the porous material may be in powder form, pellet form, bead form, film form, or block form. Furthermore, multiple shapes of porous material may be used in combination.

[0058] There are no particular restrictions on the type of gas stored in the gas storage container. Examples of such gases include nitrogen, oxygen, air, carbon dioxide, noble gases such as helium, neon, argon, krypton, and xenon, hydrogen, saturated hydrocarbons such as methane, ethane, and propane, fluorocarbons such as acetylene and difluoromethane, LPG, natural gas, monosilane, theos, dichlorosilane, arsine, phosphine, diborane, boron trichloride, carbon tetrafluoride, nitrogen trifluoride, hydrogen bromide, chlorine, tungsten hexafluoride, hydrogen selenide, monogermane, ethylene oxide, nitrous oxide, and ammonia. Of these, it is particularly preferable to use a gas selected from the group consisting of nitrogen, oxygen, air, carbon dioxide, methane, and hydrogen. [Examples]

[0059] [Occupied volume] As described above, the present invention makes it possible to provide a gas storage container that is easy to transport and install. Hereinafter, referring to Figures 1 to 3, we will demonstrate that it is also possible to optimize the occupied volume using the gas storage container described above as an example.

[0060] A typical gas cylinder has a bottle shape. Its diameter is 23.2 cm, its height is 151 cm, and its volume is 47 L. In addition, a component is needed to secure the gas cylinder. Hereafter, we will assume that this securing component is a 25 cm square.

[0061] In contrast, let's consider the case where a cubic gas storage container with sides of 25 cm is used, as explained with reference to Figures 1 to 3. In this case, the volume of one gas storage container is 25 cm × 25 cm × 25 cm = approximately 15.6 L. As mentioned above, these gas storage containers can be stacked vertically. Assuming the same height as a conventional gas cylinder, six gas storage containers can be stacked. In this case, the total volume will be approximately 15.6 L × 6 = approximately 94 L. That is, the capacity can be approximately doubled for almost the same occupied volume. In other words, by stacking three gas storage containers, the same capacity as a conventional gas cylinder can be achieved. That is, in this case, the occupied volume can be approximately halved.

[0062] Furthermore, as mentioned above, the amount of gas that can be stored can be further improved by introducing porous materials into the gas storage container. Below, we will provide additional explanations of examples demonstrating this effect.

[0063] [Preparation of porous materials] The porous materials used are summarized in Table 4 below. In the table, HKUST-1 was synthesized using a twin-screw extruder according to the reference (Chem. Sci., 2015, 6, 1645-1649). ZIF-8, MIL-53(Al), AX-21, and 13X were commercially available. The density and pore volume in the table were taken from the reference (Chem. Sci., 2014, 5, 32-51).

[0064] [Table 4]

[0065] [Adsorption amount measurement] Adsorption amounts were measured at 298K using a BELSORP-HP (manufactured by Microtrac-Bel Co., Ltd.). The porous material used was in powder form.

[0066] [nitrogen] A comparison was made using nitrogen as the gas, with a packing ratio F = 60%. The results are summarized in Table 5 and Figure 17 below.

[0067] [Table 5]

[0068] A comparison was made using nitrogen as the gas, with a packing ratio F = 80%. The results are summarized in Table 6 and Figure 18 below.

[0069] [Table 6]

[0070] [oxygen] A comparison was made using oxygen as the gas, with a packing density F = 60%. The results are summarized in Table 7 and Figure 19 below.

[0071] [Table 7]

[0072] [methane] A comparison was made using methane as the gas, with a packing ratio F = 60%. The results are summarized in Table 8 and Figure 20 below.

[0073] [Table 8] [Explanation of Symbols]

[0074] 1, 1A, 1B, 1C...Gas storage container, 10...Top surface, 12...Discharge port (inlet), 14...Recess, 20...Bottom surface, 30...Side, 32...Discharge port (inlet), 34...Recess, 40...Side, 42...Discharge port (inlet), 44...Recess, 70...Inner surface, 100...Grip part, 102...Recess, 200...Casing, 300...Gas cylinder.

Claims

1. A gas storage container that has flat top and bottom surfaces and can be stacked one on top of the other.

2. 2. The gas storage container according to claim 1, which is prismatic.

3. 3. The gas storage container according to claim 2, which is in the shape of a square prism, a pentagonal prism, or a hexagonal prism.

4. 4. The gas storage container according to claim 3, which is in the shape of a rectangular parallelepiped or a cube.

5. 5. The gas storage container according to claim 1, wherein a gas outlet is provided on at least one side surface.

6. 6. The gas storage container according to claim 5, wherein the at least one side surface has a recess, and the outlet is provided within the recess.

7. 7. The gas storage container according to claim 1, further comprising a grip portion.

8. 8. The gas storage container according to claim 1, wherein the inner surface is spherical, cylindrical, or elliptical cylindrical.

9. a casing having flat upper and lower surfaces and capable of being stacked one on top of the other; a gas cylinder installed in the casing; 9. The gas storage container according to claim 1, comprising:

10. 10. The gas storage container according to claim 1, further comprising a gas level measurement module.

11. 10. The gas storage container according to claim 9, further comprising a gas level measuring module between the casing and the gas cylinder.

12. 12. The gas storage container according to claim 10, wherein the gas level measurement module includes a temperature sensor.

13. 13. The gas storage container according to claim 10, wherein the gas remaining amount measuring module is configured to be capable of wireless communication.

14. 14. The gas storage container according to claim 10, wherein the gas remaining amount measuring module is configured to be capable of GPS communication.

15. 15. The gas storage container according to any one of claims 1 to 14, further comprising a porous material therein.

16. 16. The gas storage vessel of claim 15, wherein the porous material is a metal-organic framework.

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