The method of producing an aqueous solution for oral use in which purine alkaloids are reduced for drinking.

Abstract

Invention details;

Description

Method for producing oral drinking solution with reduced purine alkaloids

[0001] The present invention relates to a method for producing an oral drinking solution having a reduced purine alkaloid content. More specifically, the present invention relates to a method for producing an oral drinking solution having a reduced purine alkaloid content by utilizing a metal organic framework.

[0002] Popular beverages such as coffee and tea contain caffeine. Caffeine is a purine alkaloid, and while there is a need to actively ingest it to suppress drowsiness due to its pharmacological effects, some consumers avoid caffeinated beverages such as coffee due to concerns that its ingestion may interfere with sleep or sleep onset. Therefore, attempts have been made to remove caffeine, a purine alkaloid, from beverages containing caffeine without affecting other components as much as possible.

[0003] Conventional methods for removing purine alkaloids, such as caffeine, from oral drinking solutions include the use of adsorbents such as activated carbon and zeolite, and the use of ion exchange resins. Other methods include the use of chlorine-based organic solvents such as methylene chloride and chloroform, and extraction and removal using supercritical carbon dioxide. It is also known to use activated clay or acid clay as an adsorbent for removing caffeine (Patent Documents 1 and 2).

[0004] Meanwhile, in recent years, metal-organic frameworks (sometimes referred to as "MOFs") have been attracting attention as novel porous materials. Metal-organic frameworks are structures in which a pore structure is formed by the accumulation of metal complex molecules, and are also called porous metal complexes or aggregate-type metal complexes. Compared to porous materials such as activated carbon and zeolite, metal-organic frameworks have the advantage that they can be designed and controlled to have more uniform pore sizes. Another feature of metal-organic frameworks is that they are usually synthesized as fine powders, making them easy to handle when considering practical use.

[0005] Previous research has revealed that metal-organic frameworks have high gas adsorption properties, and they have been used primarily in gas storage devices and separation devices (Patent Documents 3 to 5). Furthermore, because metal-organic frameworks are highly ionic in structure, they are also known to be used as catalysts (Patent Document 6).

[0006] Japanese Patent Laid-Open No. 6-142405 Japanese Patent Laid-Open No. 2004-222719 Japanese Patent Laid-Open No. 2018-150255 Japanese Patent Laid-Open No. 2020-18995 Japanese Patent Laid-Open No. 2020-105118 Japanese Patent Laid-Open No. 2017-149683

[0007] As described above, in the technical field of oral drinking solutions such as coffee drinks and tea drinks, one of the objectives in developing and designing oral drinking solutions such as beverage products is to remove purine alkaloids, e.g., caffeine, from the oral drinking solutions to reduce the caffeine content. Therefore, an object of the present invention is to provide a method for producing oral drinking solutions with reduced purine alkaloids such as caffeine.

[0008] While investigating the reduction of caffeine from an aqueous solution containing caffeine, a purine alkaloid, the present inventors focused on metal-organic frameworks, which have rarely been used for liquids in conventional technologies. As described above, metal-organic frameworks have traditionally been used primarily for gases, such as in gas storage devices and separation devices. After extensive research to solve the above-mentioned problems, the present inventors discovered that a metal-organic framework having a predetermined structure has the ability to adsorb caffeine and is useful for reducing the amount of caffeine in a caffeine-containing aqueous solution. Based on this finding, the present inventors have completed the present invention.

[0009] That is, the present invention relates to, but is not limited to, the following: (1) Zr as a metal ion ４＋ , Cr ３＋ , or Al ３＋(2) The method according to (1), wherein the oral drinking solution contains a purine alkaloid. (3) The method according to (2), wherein the content of purine alkaloids in the oral drinking solution is 2000 ppm or less. (4) The method according to any one of (1) to (3), wherein 0.01 to 20 parts by weight of the metal organic framework is contacted with 100 parts by weight of the oral drinking solution. (5) The method according to any one of (1) to (4), wherein the pore size of the metal organic framework is 0.2 to 6 nm. (6) The method according to any one of (1) to (5), wherein the purine alkaloid is caffeine. (7) The method according to any one of (1) to (6), wherein the oral drinking solution is a beverage. (8) The method according to (7), wherein the beverage is a coffee beverage or a tea beverage. (9) The method according to any one of (1) to (6), wherein the metal ion is Zr. ４＋ , Cr ３＋ , or Al ３＋ (10) A purine alkaloid-reduced oral drinking solution produced by a method comprising a step of contacting an oral drinking solution with a metal organic framework containing Zr as the metal ion and a terephthalate ion as the organic ligand. ４＋ , Cr ３＋ , or Al ３＋ (11) A method for adsorbing purine alkaloids, comprising a step of contacting a metal organic framework containing a terephthalate ion as an organic ligand with an oral drinking aqueous solution. ４＋ , Cr ３＋ , or Al ３＋ and a metal organic framework containing a terephthalate ion as an organic ligand.

[0010] According to the present invention, a method for producing an oral drinking aqueous solution in which purine alkaloids are effectively reduced can be provided. Furthermore, by utilizing the technology of the present invention, a method for effectively adsorbing and removing purine alkaloids from an oral drinking aqueous solution can be provided. By using the present invention, for example, a beverage (e.g., coffee beverage or tea beverage) with a significantly reduced caffeine content can be provided.

[0011] Fig. 1 is a diagram showing the concentrations of various organic acids in a coffee beverage after separation and recovery of a metal-organic framework. Fig. 2 is a diagram showing the amount of caffeine adsorbed per 1 g of metal-organic framework for various liquid volumes of a caffeine-containing aqueous solution. Fig. 3 is a diagram showing the adsorption isotherm of the metal-organic framework. Fig. 4 is a diagram showing the concentrations of various organic acids in a green tea beverage, a black tea beverage, and an oolong tea beverage after separation and recovery of a metal-organic framework.

[0012] The present invention will be described below. Unless otherwise specified, the terms "ppm," "ppb," and "wt %" used in this specification mean ppm, ppb, and wt % of weight / volume (w / v), respectively.

[0013] One aspect of the present invention is to use Zr as the metal ion. ４＋ , Cr ３＋ , or Al ３＋ and a terephthalate ion as an organic ligand, with the aqueous oral drinking solution.

[0014] In this specification, the term "purine alkaloid-reduced oral drinking aqueous solution" refers to an oral drinking aqueous solution in which the content of purine alkaloids has been reduced. Furthermore, "purine alkaloid content reduced" means that the content of purine alkaloids is less than the amount of purine alkaloids contained in the oral drinking aqueous solution before contact with the metal organic framework.

[0015] The method of the present invention uses a metal-organic framework. A metal-organic framework (sometimes referred to as "MOF") is a material based on coordination chemistry that forms a porous structure by utilizing coordinate bonds between metal ions and organic compounds. In a metal-organic framework, a crystalline polymer structure with internal spaces (pores) is created by combining various metal ions with bridging organic ligands that connect them. Such materials are also called porous metal complexes or integrated metal complexes, and as mentioned above, they have traditionally been used primarily in the field of gases to adsorb specific gas components (hydrogen gas, methane gas, carbon dioxide, etc.).

[0016] The metal organic framework used in the present invention contains Zr as the metal ion. ４＋ (zirconium ion (4+)), Cr ３＋ (chromium ion (3+)), or Al ３＋ (Contains aluminum ions (3+)). Zr ４＋ , Cr ３＋ , and Al ３＋ The metal ions may contain only one kind, or two or more kinds (or all three kinds). In the present invention, Zr ４＋ , Cr ３＋ , and Al ３＋ Among these three metal ions, Cr is preferred. ３＋ or Al ３＋ and more preferably Al ３＋ is included in the metal organic framework.

[0017] In the present invention, the metal organic framework contains a terephthalate ion as an organic ligand. The organic ligand is a crosslinkable organic material that connects metal ions and is characterized by forming a coordinate bond with the metal ion. The terephthalate ion is a terephthalic acid (chemical formula: C ８ H ６ O ４ , CAS registration number: 100-21-0) is ionized and is represented, for example, by the following chemical formula:

[0018]

[0019] The metal organic framework may contain only terephthalate ions as organic ligands, or may contain organic ligands other than terephthalate ions. When other organic ligands are contained, the proportion of terephthalate ions in all the ligands is not particularly limited, but is, for example, 90 mol % or more, preferably 95 mol % or more, and more preferably 98 mol % or more.

[0020] The metal organic framework used in the present invention is, for example, aluminum hydroxide terephthalate MOF (MIL-53(Al)) (chemical formula: C ８ H ４ AlO ５ , CAS registration number: 654061-20-8), MIL-101(Cr) (chemical formula: C ２４ H １６ Cr ３ FO １６ , CAS registration number: 869288-09-5), and zirconium 1,4-dicarboxybenzene MOF (UiO-66) (chemical formula: C ４８ H ２８ O ３２ Zr ６ , CAS Registry Number: 1072413-89-8), etc. are included, but are not limited to these. In the present invention, MIL-53(Al) and MIL-101(Cr) are preferably used, and MIL-53(Al) is particularly preferably used.

[0021] The metal-organic framework is characterized by having a porous structure. The pore diameter of the metal-organic framework in the present invention is not particularly limited, but is, for example, 0.2 to 6 nm, preferably 0.3 to 5 nm, and more preferably 0.4 to 4 nm. The pore diameter of the metal-organic framework can be measured using a commercially available pore distribution measuring device or the like.

[0022] The specific surface area (BET surface area) of the metal organic framework is not particularly limited, but is, for example, 60,000 m ２ / g or less, preferably 300 to 4000m ２ / g, more preferably 500 to 2000m ２The specific surface area of ​​the metal organic framework can be measured using a commercially available specific surface area measuring device or the like.

[0023] In the present invention, the metal organic framework used may be a commercially available one, or may be one prepared by oneself. The metal organic framework can be produced using a conventionally known method. Examples of methods for producing a metal organic framework include a solution method and a hydrothermal method. The solution method is a method for producing a metal organic framework by mixing solutions of metal ions and organic ligands. Usually, mixing is performed at room temperature and atmospheric pressure, but the conditions are not particularly limited. The solution method includes a diffusion method in which a solution is mixed by diffusing, and a stirring method in which a solution is mixed by stirring, and either method may be used. The hydrothermal method is a method for producing a metal organic framework by placing a solvent and raw material reagents in a sealed container, heating them to a temperature above the boiling point of the solvent, and causing a hydrothermal reaction (also called a solvothermal reaction) to proceed.

[0024] In addition to the above methods, other methods that can be used include a microwave method in which raw material reagents and a solvent are placed in a reaction vessel and irradiated with microwaves (electromagnetic waves) to produce a metal organic framework, an ultrasonic method in which raw material reagents and a solvent are placed in a reaction vessel and irradiated with ultrasonic waves to produce a metal organic framework, and a solid-phase synthesis method in which raw material reagents are mechanically mixed without using a solvent to produce a metal organic framework. In any of these methods, the concentration of the metal ion in the solvent, the concentration of the organic ligand in the solvent, the reaction temperature, pressure, time, and the microwave and ultrasonic frequencies can be appropriately set depending on the purpose and circumstances.

[0025] The method of the present invention includes a step of contacting the metal-organic framework with an oral drinking aqueous solution. The oral drinking aqueous solution is an aqueous solution intended to be orally ingested. In the present invention, the oral drinking aqueous solution is not limited to soft drinks as defined by the Food Sanitation Act, but may also include drinking aqueous solutions containing alcohol, other medicinal ingredients, medicinal active ingredients, etc., and also includes alcoholic beverages as defined by the Liquor Tax Act, and pharmaceuticals and quasi-drugs as defined by the Pharmaceutical and Medical Device Act. The oral drinking aqueous solution may be consumed as is (straight) without dilution, or may be diluted before consumption. The diluting agent used to dilute the oral drinking aqueous solution is not particularly limited, and examples include water, carbonated water, milk, and fruit juice. The temperature at which the solution is consumed is also not particularly limited, and the solution may be consumed at room temperature, or may be cooled or heated before consumption. In the method of the present invention, the oral drinking aqueous solution that the metal organic framework comes into contact with may be an oral drinking aqueous solution immediately before the purine alkaloid content is reduced, or may be an intermediate product of the oral drinking aqueous solution before the purine alkaloid content is reduced, or a raw material in the state of an orally drinkable aqueous solution.

[0026] In the present invention, a purine alkaloid-reduced oral drinking solution can be produced through a step of contacting the above metal organic framework with an oral drinking solution. Purine alkaloid is a general term for alkaloids having a purine skeleton. Alkaloids are low-molecular-weight compounds containing basic nitrogen, and are known to exist mainly in plants. Examples of purine alkaloids include caffeine, theobromine, and theophylline. In the present invention, caffeine (chemical formula: C ８ H １０ N ４ O ２ , CAS registration number: 58-08-2) is preferred.

[0027] In the method of the present invention, the oral drinking aqueous solution with which the metal-organic framework comes into contact contains a purine alkaloid. The content of the purine alkaloid in the oral drinking aqueous solution with which the metal-organic framework comes into contact is not particularly limited, but is, for example, 2000 ppm or less, preferably 1600 ppm or less, and more preferably 1500 ppm or less. The lower limit of the purine alkaloid content in the oral drinking aqueous solution is not particularly limited, but is, for example, 10 ppm or more, preferably 30 ppm or more, and more preferably 50 ppm or more. The purine alkaloid content in the oral drinking aqueous solution is typically, for example, 10 to 2000 ppm, preferably 30 to 1600 ppm, and more preferably 50 to 1500 ppm. When two or more types of purine alkaloids are present, the content refers to the total content of the various purine alkaloids. The purine alkaloid content can be measured by known methods, such as HPLC, LC / MS, GC / MS, LC, GC, and near-infrared spectroscopy.

[0028] In the method of the present invention, although not particularly limited, for example, 0.01 to 20 parts by weight of the metal organic framework can be brought into contact with 100 parts by weight of the oral drinking aqueous solution. In the present invention, preferably 0.02 to 10 parts by weight, more preferably 0.05 to 5 parts by weight of the metal organic framework can be brought into contact with 100 parts by weight of the oral drinking aqueous solution.

[0029] The oral drinking aqueous solution with which the metal-organic framework comes into contact can be, but is not limited to, a plant extract such as coffee, cacao, tea leaves (green tea, black tea, oolong tea, etc.), or cola. It is also possible to use an extract of another plant, or an aqueous solution to which synthetic purine alkaloids or purified purine alkaloids (including crudely purified products) have been added. In the present invention, the oral drinking aqueous solution with which the metal-organic framework comes into contact can be a beverage. The beverage is a soft drink as defined by the Food Sanitation Act or an alcoholic beverage as defined by the Liquor Tax Act, but is preferably a soft drink. Examples of such beverages include, but are not limited to, coffee beverages, tea beverages (green tea beverages, black tea beverages, oolong tea beverages, etc.), cola beverages, cocoa beverages, etc. In the present invention, coffee beverages and tea beverages (green tea beverages, black tea beverages, oolong tea beverages, etc.) are preferably used as the oral drinking aqueous solution with which the metal-organic framework comes into contact.

[0030] In the present invention, the purine alkaloid-reduced oral drinking aqueous solution is also preferably a beverage, and more preferably a coffee beverage or a tea beverage (green tea beverage, black tea beverage, oolong tea beverage, etc.).

[0031] The method of the present invention may include a step of contacting the metal-organic framework with an oral drinking aqueous solution and then removing the metal-organic framework from the oral drinking aqueous solution. The metal-organic framework after contacting with the oral drinking aqueous solution can be removed from the oral drinking aqueous solution by, for example, performing solid-liquid separation using a method well known to those skilled in the art, such as filtration, without any particular limitation.

[0032] Another aspect of the present invention is to use Zr as the metal ion. ４＋ , Cr ３＋ , or Al ３＋ and a method for producing the purine alkaloid-reduced oral drinking solution, the method comprising the step of contacting a metal organic framework containing a terephthalate ion as an organic ligand with an oral drinking solution. Matters related to the purine alkaloid-reduced oral drinking solution of the present invention are as described above with respect to the method for producing the purine alkaloid-reduced oral drinking solution, or are obvious from the same.

[0033] Another aspect of the present invention is a method for producing a compound containing Zr as a metal ion. ４＋ , Cr ３＋ , or Al ３＋ and contacting an oral drinking aqueous solution with a metal-organic framework containing terephthalate ions as an organic ligand. The metal-organic framework and materials therefor, as well as other matters relating to the method for adsorbing purine alkaloids, are as described above with respect to the method for producing a purine alkaloid-reduced oral drinking aqueous solution, or are obvious from the above. Note that the oral drinking aqueous solution in the method for adsorbing purine alkaloids corresponds to the oral drinking aqueous solution with which the metal-organic framework is brought into contact, among the oral drinking aqueous solutions described with respect to the method for producing a purine alkaloid-reduced oral drinking aqueous solution.

[0034] In the method for adsorbing purine alkaloids of the present invention, purine alkaloids in an oral drinking aqueous solution are adsorbed by a metal-organic framework, thereby making it possible to remove some or all of the purine alkaloids from the oral drinking aqueous solution. Furthermore, the purine alkaloids adsorbed and removed by this method can be released from the metal-organic framework by utilizing the properties of the metal-organic framework. Therefore, another aspect of the present invention is a method for releasing, from the metal-organic framework, a purine alkaloid adsorbed using the above-described method of the present invention (method for adsorbing purine alkaloids). The released purine alkaloids can also be used for other purposes. Furthermore, the metal-organic framework from which the purine alkaloids have been released can be reused in the method for adsorbing purine alkaloids.

[0035] Another aspect of the present invention is a method for producing a compound containing Zr as a metal ion. ４＋ , Cr ３＋ , or Al ３＋and a metal organic framework containing a terephthalate ion as an organic ligand. By utilizing the adsorbent of the present invention, purine alkaloids can be effectively removed from oral drinking aqueous solutions. Furthermore, the adsorbent of the present invention is also capable of desorbing purine alkaloids once adsorbed. The metal organic framework and materials thereof constituting the adsorbent of the present invention are as described above in the method for preparing a purine alkaloid-reduced oral drinking aqueous solution, or are self-evident therefrom.

[0036] The present invention will be described in more detail below with reference to experimental examples, but the present invention is not limited thereto. Furthermore, in this specification, unless otherwise specified, numerical ranges are stated to include their endpoints.

[0037] Experimental Example 1. Screening of MOFs with caffeine adsorption capacity In order to obtain a metal-organic framework (MOF) that exhibits caffeine adsorption, various MOFs were prepared and their caffeine adsorption capacity in a caffeine aqueous solution was examined. MOFs manufactured by Atomis Corporation were used, and the caffeine adsorption capacity of the various MOFs shown in the table below was examined.

[0038]

[0039] 1 g of each of the above MOFs was added to 50 g of a caffeine solution with a caffeine concentration of 600 mg / L. The caffeine solution to which the MOFs had been added was allowed to stand at room temperature for 24 hours, after which the MOFs were separated and recovered. The weight and caffeine concentration of the caffeine solution after MOF recovery were measured. The caffeine concentration was measured by HPLC, measuring the concentration of anhydrous caffeine in the solution, and the measurement was performed at the Japan Food Research Center Foundation. The caffeine concentration measurement conditions were as follows: Pretreatment: Dilution with methanol solution Equipment used: HPLC LC-20AD (Shimadzu Corporation) Column: CAPCELL PAK C18 MG 5 μm (diameter 3 mm x 15 cm) (Shiseido) Mobile phase: 0.01 mol ammonium acetate / methanol mixture Detector: UV-visible spectrometer SPD-20A (Shimadzu Corporation) Detection wavelength: 270 nm

[0040] The specific gravity of the caffeine aqueous solution after MOF recovery was set to 1.0, and the weight of caffeine was calculated from the above caffeine concentration. The difference between the weight of caffeine after MOF recovery and the data for a blank (no MOF added) was taken as the amount of caffeine adsorbed, and the amount of caffeine adsorbed per 1 g of MOF was determined. Furthermore, the ratio of the amount of caffeine adsorbed to the weight of caffeine in the blank (no MOF added) was determined as the caffeine removal capacity. The results are shown below.

[0041]

[0042] As shown above, it was found that among the 10 MOFs examined, AP0010, AP0013, AP5013 and AP0008 had high caffeine adsorption capacity.

[0043] Experimental Example 2. Selective Separation Ability of Caffeine The selective separation ability of the four types of MOFs obtained in the above test was examined using coffee extract. A commercially available canned coffee drink (Suntory, product name: Boss Unsweetened Black) was used as the coffee extract. 1 g of each MOF was added to 50 g of coffee extract and allowed to stand at room temperature for 24 hours. The MOFs were then separated and recovered, and the weight and caffeine concentration of the coffee extract after MOF recovery were measured in the same manner as in Experimental Example 1. Additionally, the coffee extract after MOF recovery was subjected to component analysis of various organic acids (phosphoric acid, citric acid, malic acid, quinic acid, acetic acid, and propionic acid). The organic acid content was measured using HPLC under the following measurement conditions: Measurement device: HPLC LC-20AD (Shimadzu Corporation); Detector: Electrical conductivity detector CDD-10A ＶＰ(Shimadzu Corporation) Column: Shim-pack SCR-102H (8 mm x 300 mm, 7 μm) (Shimadzu Corporation), two connected in series Guard column: Shim-pack SCR-102H (6 mm x 50 mm, 7 μm) (Shimadzu Corporation) Column oven temperature: 50°C Mobile phase: p-toluenesulfonic acid aqueous solution (5 mmol / L) Detecting solution: Bis-Tris aqueous solution (20 mmol / L) containing p-toluenesulfonic acid (5 mmol / L) and EDTA (100 μmol / L) Pump flow rate (mobile phase): 0.8 ml / min Pump flow rate (detecting solution): 0.8 ml / min Injection volume: 10 μl Polarity: + Cell temperature: automatically set

[0044] The results are shown in the table below. The results of component analysis of various organic acids are also shown in Figure 1.

[0045]

[0046]

[0047] The above results revealed that AP0008 had a reduced caffeine adsorption capacity when used with coffee extract. Regarding MOFs other than AP0008, the analysis of various organic acids in coffee extract after addition of MOF revealed that AP5013 had the highest selectivity for caffeine adsorption, followed by AP0013, in comparison with a blank (no MOF added).

[0048] Furthermore, the results of measuring the concentrations of various organic acids showed that AP0010 measured lower concentrations of most organic acids than the blank (no MOF added), indicating that it adsorbed not only caffeine but also organic acids in the coffee extract. From the above results, AP0013 and AP5013 measured relatively similar organic acid concentrations compared to the blank, indicating that they can selectively separate and adsorb caffeine. When comparing AP0013 and AP5013, AP5013 was considered to have a higher selective separation ability for caffeine compared to the blank. Furthermore, AP0008 measured organic acid concentrations almost equivalent to the blank, but caffeine was not adsorbed, indicating that AP0008 is not suitable for use with coffee extracts.

[0049] Experimental Example 3-1. Caffeine Adsorption Capacity (1) A test was conducted to confirm the caffeine adsorption capacity of the four types of MOFs described above. A caffeine aqueous solution with a caffeine concentration of 600 mg / L was prepared, and 1 g of MOF was added to 50 mL, 100 mL, 500 mL, and 1000 mL of the caffeine aqueous solution. The caffeine aqueous solution to which MOF was added was allowed to stand at room temperature for 24 hours, after which the MOF was separated and recovered. Then, as in Experimental Example 1, the weight and caffeine concentration of the caffeine aqueous solution after MOF recovery were measured, and the caffeine weight was calculated from the caffeine concentration after MOF recovery. In addition, the difference between the weight of caffeine in the caffeine aqueous solution before addition of MOF and the weight of caffeine after MOF recovery was defined as the caffeine adsorption amount, and the caffeine adsorption amount per 1 g of MOF was investigated. The results are shown in the table below and Figure 2.

[0050]

[0051] The above results show that AP5013 has the largest adsorption capacity for caffeine, followed by AP0013. This suggests that AP5013 has the potential to adsorb the largest amount of caffeine as an adsorbent.

[0052] Experimental Example 3-2. Caffeine Adsorption Capacity (2) Following Experimental Example 3-1 above, the caffeine adsorption capacity was further investigated for the MOFs AP0010, AP0013, and AP5013. Caffeine aqueous solutions with caffeine concentrations of 300 mg / L and 1200 mg / L were prepared, and 1 g of MOF was added to 100 mL of each caffeine aqueous solution. As in Experimental Example 3-1, the caffeine aqueous solution to which MOF had been added was allowed to stand at room temperature for 24 hours, after which the MOF was separated and recovered. The weight and caffeine concentration of the caffeine aqueous solution after MOF recovery were then measured. In addition, the caffeine weight was calculated from the caffeine concentration after MOF recovery, and the caffeine adsorption amount per 1 g of MOF was investigated. Note that concentration measurements and numerical calculations were performed in the same manner as in Experimental Example 3-1, and the number of tests in this experiment was N = 3. The results are shown in the table below.

[0053]

[0054] As described above, even when the caffeine concentration of the caffeine aqueous solution was changed, it was shown that AP5013 had the largest caffeine adsorption capacity, followed by AP0013. Using the above caffeine adsorption amount (average) and the caffeine concentration of 600 mg / L shown in the results of Experimental Example 3-1, a caffeine adsorption isotherm was created as shown in Figure 3.

[0055] Experimental Example 4. Caffeine Adsorption Capacity in Various Beverages The caffeine adsorption effects of the AP0010, AP0013, and AP5013 MOFs in beverages other than coffee, including green tea, black tea, and oolong tea, were investigated. The beverages used were a commercially available bottled green tea (Suntory, product name: Suntory Green Tea Iyemon), a commercially available bottled black tea (Suntory, product name: Craft Bosty Unsweetened Black Tea), and a commercially available bottled oolong tea (Suntory, product name: Suntory Oolong Tea). 1 g of MOF was added to 50 g of each beverage sample and allowed to stand at room temperature for 24 hours. The MOFs were then separated and recovered. The weight and caffeine concentration of the beverage samples after MOF recovery were measured in the same manner as in Experimental Example 1, and the weight of caffeine in the beverage samples after MOF recovery was calculated from these measurements. The caffeine concentration obtained from the blank (no MOF added) was used as the caffeine concentration in the beverage before MOF addition, and the weight of caffeine in the beverage before MOF addition was calculated. The difference between this weight and the weight of caffeine after MOF recovery was used as the caffeine adsorption amount. The amount of caffeine adsorption per 1 g of MOF was then determined. Furthermore, the caffeine removal rate was determined by measuring the ratio of the amount of caffeine adsorption to the weight of caffeine obtained from the blank (no MOF added). Furthermore, the beverage samples after MOF recovery were subjected to component analysis of various organic acids (phosphoric acid, citric acid, malic acid, quinic acid, acetic acid, and propionic acid) using the same method as in Experimental Example 2. The number of tests other than the blank was N = 3, and the average was calculated.

[0056] The recovered MOF was washed three times with 50 mL of distilled water to remove various beverage-derived components adhering to the MOF surface. The washed MOF and 50 mL of distilled water were then placed in a 100 mL medium bottle and allowed to stand at 90°C for 6 hours. The resulting filtrate was then promptly filtered, and the caffeine concentration in the desorption beverage sample was measured in the same manner as in Experimental Example 1. The weight of caffeine in the desorption beverage sample was calculated from the measured caffeine concentration, and the amount of caffeine desorbed per 1 g of MOF and the caffeine desorption ratio were also investigated. N = 3 tests were performed, and the average value was calculated.

[0057] The results are shown in the table below. Regarding caffeine adsorption and removal, the results obtained in Experimental Example 2 above are also included in the table below to allow for comparison with coffee beverages.

[0058]

[0059]

[0060] As described above, AP0010, AP0013, and AP5013 all demonstrated high caffeine adsorption capacity in various beverages. Furthermore, all of the tested MOFs were confirmed to have the ability to desorb adsorbed caffeine. Regarding the results of measuring the concentrations of various organic acids, AP5013 measured relatively similar organic acid concentrations to the blank, demonstrating that AP5013 has the highest selective separation capacity for caffeine among the three MOFs.

Claims

DEPCT6911 / 09 / 25681. Method for the production of an oral aqueous solution containing reduced purine alkaloids for drinking. The method involves the application of an oral aqueous solution for drinking containing a metal-organic framework composed of Zr4+, Cr3+, or Al3+ as metal ions and terephthalic acid ions as organic ligands.

2. Method according to claim 1, in which the oral aqueous solution for drinking contains purine alkaloids.

3. Method according to claim 2, in which the amount of purine alkaloids in the topical aqueous solution is determined.

4. A method under Reputation 1 in which 0.01 to 20 parts by weight of the metal-organic framework is exposed to 100 parts by weight of an aqueous solution for oral consumption.

5. Any one of the methods under Reputation 1 to 4 in which the metal-organic framework has a pore size of 0.2 to 6 nanometers.

6. Any one of the methods under Reputation 1 to 4 in which the purine alkaloid is caffeine.

7. Any one of the methods under Reputation 1 to 4 in which the aqueous solution for oral consumption is a beverage. 8.

9. An oral aqueous solution in which purine alkaloids are reduced for drinking, which is produced by means of an assembled metal-organic framework incorporating Zr4+, Cr3+, or Al3+ as metal ions and terephthalic acid ions as organic ligands, ..., and terephthalic acid ions as organic ligands, incorporating Zr4+, Cr3+, or Al3

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