Method for producing oral drinking water solution having reduced purine alkaloid

Abstract

The purpose of the present invention is to provide a method for producing an oral drinking water solution in which purine alkaloids are effectively reduced. According to the present invention, a metal organic framework containing Zr < 4 + >, Cr < 3 + > or Al < 3 + > as a metal ion and terephthalic acid ions as an organic ligand is brought into contact with an oral drinking water solution.

Description

Technical Field

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

[0002] Drinks like coffee and tea are widely consumed, often containing caffeine. While caffeine, a purine alkaloid, is consumed for its pharmacological effects to suppress drowsiness, some consumers avoid caffeinated beverages like coffee due to potential interference with sleep and sleep retention. Therefore, efforts are underway to remove caffeine from beverages containing caffeine, a purine alkaloid, while minimizing the effects on other ingredients.

[0003] Conventional methods for removing purine alkaloids, such as caffeine, from oral drinking water 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 dichloromethane and chloroform, and extraction with supercritical carbon dioxide. Furthermore, the use of activated clay or acid clay as an adsorbent for caffeine removal is also known (Patent Documents 1 and 2).

[0004] Meanwhile, metal-organic frameworks (MOFs) have recently attracted considerable attention as novel porous materials. MOFs are structures composed of metal complex molecules aggregated to form a finely porous structure. They are also referred to as porous metal complexes or aggregated metal complexes. Compared to porous materials such as activated carbon or zeolites, MOFs offer the advantage of easier design and control of pore size uniformity. Furthermore, MOFs are typically synthesized in a micropowder form, making them easier to manipulate for practical applications, a key advantage.

[0005] Previous research has confirmed that metal-organic frameworks (MOFs) have high gas adsorption properties and have been primarily used in gas storage and separation devices (Patent Documents 3–5). Furthermore, due to their structurally rich ionic properties, MOFs are also known to be used as catalysts (Patent Document 6).

[0006] Patent Literature Patent Document 1: Japanese Patent Application Laid-Open No. 6-142405 Patent Document 2: Japanese Patent Application Laid-Open No. 2004-222719 Patent Document 3: Japanese Patent Application Publication No. 2018-150255 Patent Document 4: Japanese Patent Application Laid-Open No. 2020-18995 Patent Document 5: Japanese Patent Application Laid-Open No. 2020-105118 Patent Document 6: Japanese Patent Application Laid-Open No. 2017-149683 Summary of the Invention

[0007] As described above, in the technical field of oral drinking water solutions such as coffee beverages and tea beverages, one of the goals of developing and designing oral drinking water solutions, such as beverages, is to remove purine alkaloids, such as caffeine, from the solutions to reduce their caffeine content. Therefore, the present invention aims to provide a method for producing an oral drinking water solution with a reduced content of purine alkaloids, such as caffeine.

[0008] The present inventors conducted research on reducing caffeine in aqueous solutions containing caffeine, a purine alkaloid, and noted that metal-organic frameworks (MOFs) had previously been largely unused in liquids. As mentioned above, MOFs have been primarily used for gas storage and separation, for example. To address this issue, the present inventors conducted extensive research and discovered that MOFs with a specific structure can adsorb caffeine, making them useful for reducing the caffeine content in aqueous solutions containing caffeine. Based on this discovery, the present inventors completed the present invention.

[0009] That is, the present invention is not limited to these but relates to the following contents. (1) A method for producing an oral drinking water solution with reduced purine alkaloids, characterized in that it comprises: 4+ Cr 3+ or Al 3+ The invention relates to a process for contacting a metal organic framework containing terephthalate ions as metal ions and organic ligands with an oral drinking water solution. (2) The method according to (1), characterized in that the oral drinking water solution contains purine alkaloids. (3) The method according to (2), characterized in that the content of purine alkaloids in the oral drinking water 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 brought into contact with 100 parts by weight of the oral drinking water solution. (5) The method according to any one of (1) to (4), wherein the pore diameter 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 water solution is a beverage. (8) The method according to (7), wherein the beverage is a coffee beverage or a tea beverage. (9) A purine alkaloid-reduced oral drinking water solution, characterized in that it contains Zr 4+ Cr 3+ or Al 3+ The invention discloses a method for producing a metal organic framework comprising a metal ion and a terephthalate ion as an organic ligand, and a step of contacting the metal organic framework with an oral drinking water solution. (10) A method for adsorbing purine alkaloids, characterized in that it comprises: 4+ Cr 3+ or Al 3+ The invention relates to a process for contacting a metal organic framework containing terephthalate ions as metal ions and organic ligands with an oral drinking water solution. (11) A purine alkaloid adsorbent, characterized in that it contains a metal organic framework containing Zr 4+ Cr 3+ or Al 3+ As metal ions, and contains terephthalate ions as organic ligands.

[0010] The present invention provides a method for producing an oral drinking water solution that effectively reduces purine alkaloid levels. Furthermore, utilizing the technology of the present invention provides a method for effectively removing purine alkaloids from an oral drinking water solution by adsorption. By using the present invention, for example, beverages (such as coffee or tea beverages) with significantly reduced caffeine content can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a graph showing the concentrations of various organic acids in coffee beverages after separation and recovery of metal-organic frameworks. Figure 2 This is a graph showing the amount of caffeine adsorbed per 1 g of the metal-organic framework at various liquid volumes of a caffeine-containing aqueous solution. Figure 3 is a graph showing the adsorption isotherm of the metal-organic framework. Figure 4 This is a graph showing the concentrations of various organic acids in green tea beverages, black tea beverages, and oolong tea beverages after separation and recovery of metal-organic frameworks. DETAILED DESCRIPTION

[0012] The present invention will be described below. In addition, unless otherwise specified, "ppm", "ppb" and "wt%" used in this specification refer to ppm, ppb and wt% on a weight / volume (w / v) basis, respectively.

[0013] One embodiment of the present invention is a method for producing a purine alkaloid-reduced oral drinking water solution, characterized in that it comprises: 4+ Cr 3+ or Al 3+ The invention relates to a process for contacting a metal organic framework containing terephthalate ions as metal ions and organic ligands with an oral drinking water solution.

[0014] As used herein, a purine alkaloid-reduced oral drinking water solution refers to an oral drinking water solution having a reduced purine alkaloid content. Furthermore, "reduced purine alkaloid content" means that the purine alkaloid content is reduced compared to the amount of purine alkaloids contained in the oral drinking water solution prior to contact with the metal-organic framework.

[0015] A metal-organic framework is used in the method of the present invention. A metal-organic framework (sometimes referred to as a "MOF") is a material based on coordination chemistry that utilizes coordination bonds between metal ions and organic compounds to form a porous structure. In a metal-organic framework, a crystalline polymer structure with internal space (pores) can be constructed by combining a variety of metal ions with cross-linked organic ligands that link them. Such materials can also be called porous metal complexes or aggregated metal complexes. As mentioned above, they have been mainly used in the gas field to adsorb specific gas components (such as hydrogen, methane, carbon dioxide, etc.).

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

[0017] The metal-organic framework of the present invention contains terephthalate ions as organic ligands. Organic ligands are cross-linked organic materials that bind to metal ions, characterized by forming coordination bonds with the metal ions. Terephthalate ions are ionized products of terephthalic acid (chemical formula: C8H6O4, CAS Registry Number: 100-21-0), and are represented, for example, by the following chemical formula.

[0018] [Chemistry 1]

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

[0020] Examples of the metal organic framework used in the present invention include aluminum terephthalate MOF (MIL-53(Al)) (chemical formula: C8H4AlO5, CAS registration number: 654061-20-8), MIL-101(Cr) (chemical formula: C 24 H 16 Cr3FO 16 , CAS registration number: 869288-09-5) and zirconium 1,4-dicarboxybenzene MOF (UiO-66) (chemical formula: C 48 H 28 O 32 Zr6, CAS Registry No.: 1072413-89-8) etc., but 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] Metal-organic frameworks are 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 measurement device.

[0022] The specific surface area (BET surface area) of the metal organic framework is not particularly limited, and is, for example, 60,000 m 2 / g or less, preferably 300 to 4000 m 2 / g, more preferably 500 to 2000 m 2 The 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, commercial products or self-made products can be used for the metal organic framework. The metal organic framework can be manufactured using a conventionally known method. As a method for manufacturing a metal organic framework, for example, a solution method or a hydrothermal method can be cited. The solution method is a method for manufacturing a metal organic framework by mixing a solution of metal ions and an organic ligand. Usually, the mixing is carried out at room temperature and normal pressure, and the conditions are not particularly limited. In the solution method, there is a diffusion method in which the solution is diffused for mixing and a stirring method in which the solution is stirred for mixing, and either method can be used. The hydrothermal method is a method in which a solvent and a raw material reagent are placed in a sealed container, heated to above the boiling point of the solvent, and a hydrothermal reaction (also called a solvent thermal reaction) is carried out to manufacture a metal organic framework.

[0024] In addition to the above methods, the following methods may also be used: a microwave method in which a raw material reagent 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 a raw material reagent 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 a raw material reagent is 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 frequency of the microwave and ultrasonic waves can be appropriately set according to the purpose and circumstances.

[0025] The method of the present invention includes a step of contacting the above-mentioned metal-organic framework with an oral drinking water solution. The so-called oral drinking water solution is an aqueous solution intended to be taken into the body orally. In the present invention, the oral drinking water solution is not limited to the refreshing drinking water defined in the Japanese Food Sanitation Law, but may also include drinking water solutions containing alcohol, other medicinal ingredients, pharmaceutical ingredients, etc., and alcoholic beverages defined in the Japanese Liquor Tax Law, and pharmaceuticals and quasi-drugs defined in the Japanese Pharmaceutical Machinery Law. The oral drinking water solution can be drunk directly (without blending) without dilution, or it can be drunk after dilution. The blending materials used to dilute the oral drinking water solution are not particularly limited, and include, for example, water, carbonated water, milk, fruit juice, etc. In addition, the temperature when drinking is not particularly limited, and it can be drunk at room temperature, or it can be drunk after cooling or heating. In the method of the present invention, the oral drinking water solution that contacts the metal-organic framework can be an oral drinking water solution before the purine alkaloids are reduced, or it can be a product in the intermediate stage of the oral drinking water solution before the purine alkaloids are reduced, or it can be a raw material in the state of an orally drinkable aqueous solution.

[0026] In the present invention, an oral drinking water solution with reduced purine alkaloids can be produced by contacting the above-mentioned metal organic framework with an oral drinking water solution. Purine alkaloids are a general term for alkaloids having a purine skeleton. In addition, alkaloids are known to be low molecular weight compounds containing basic nitrogen and are mainly found in plants. Examples of purine alkaloids include caffeine, theobromine, and theophylline. In the present invention, caffeine (chemical formula: C8H 10 N4O2, CAS registration number: 58-08-2).

[0027] In the method of the present invention, the oral drinking water solution that contacts the metal-organic framework contains purine alkaloids. The content of purine alkaloids in the oral drinking water solution that contacts the metal-organic framework is not particularly limited, and is, for example, 2000 ppm or less, preferably 1600 ppm or less, and more preferably 1500 ppm or less. The lower limit of the content of purine alkaloids in the oral drinking water solution is not particularly limited, and is, for example, 10 ppm or more, preferably 30 ppm or more, and more preferably 50 ppm or more. The content of purine alkaloids in the oral drinking water solution is typically, for example, 10 to 2000 ppm, preferably 30 to 1600 ppm, and more preferably 50 to 1500 ppm. When there are two or more purine alkaloids, the content refers to the total content of the various purine alkaloids. The content of purine alkaloids can be determined by known methods, for example, by HPLC, LC / MS, GC / MS, LC, GC, near-infrared spectroscopy, and the like.

[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 is contacted with 100 parts by weight of the oral drinking water solution. In the present invention, preferably 0.02 to 10 parts by weight, and more preferably 0.05 to 5 parts by weight of the metal-organic framework is contacted with 100 parts by weight of the oral drinking water solution.

[0029] As an oral drinking water solution in contact with the metal organic framework, extracts of plants such as coffee, cocoa, tea (green tea, black tea, oolong tea, etc.) and cola can be used, but are not limited to these. Extracts of other plants or aqueous solutions obtained by adding synthetic purine alkaloids or refined purine alkaloids (including crude and refined products) can also be used. In the present invention, the oral drinking water solution in contact with the metal organic framework can be a beverage. Beverage refers to the refreshing drinking water defined in the Japanese Food Sanitation Law or the alcoholic beverage defined in the Japanese Liquor Tax Law, preferably refreshing drinking water. As such beverages, coffee drinks, tea drinks (green tea drinks, black tea drinks, oolong tea drinks, etc.), cola drinks, cocoa drinks, etc. can be listed, but are not limited to these. In the present invention, coffee drinks and tea drinks (green tea drinks, black tea drinks, oolong tea drinks, etc.) are preferably used as oral drinking water solutions in contact with the metal organic framework.

[0030] Furthermore, in the present invention, the purine alkaloid-reduced oral drinking water solution is preferably a beverage, 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 also include a step of removing the metal-organic framework from the oral drinking water solution after contacting the metal-organic framework with the oral drinking water solution. The metal-organic framework after contact with the oral drinking water solution can be removed from the oral drinking water solution by solid-liquid separation using methods well known to those skilled in the art, such as filtration, without particular limitation.

[0032] Another embodiment of the present invention is a purine alkaloid-reduced oral drinking water solution, characterized in that the solution comprises Zr 4+ Cr 3+ or Al 3+ The invention also relates to a method for producing a metal-organic framework containing a terephthalate ion as a metal ion and an organic ligand, and a step of contacting the metal-organic framework with an oral drinking water solution. Matters related to the purine alkaloid-reduced oral drinking water solution of the present invention are as described above with respect to the method for producing the purine alkaloid-reduced oral drinking water solution, or are self-evident therefrom.

[0033] In addition, another embodiment of the present invention is a method for adsorbing purine alkaloids, characterized in that it comprises: 4+ Cr 3+ or Al 3+ The process of contacting a metal-organic framework containing terephthalate ions as metal ions and organic ligands with an oral drinking water solution. The metal-organic framework, its materials, and other matters related to the purine alkaloid adsorption method are as described above with respect to the method for producing an oral drinking water solution with reduced purine alkaloid content, or are self-evident therefrom. Furthermore, the oral drinking water solution in the purine alkaloid adsorption method corresponds to the oral drinking water solution that contacts the metal-organic framework in the oral drinking water solution described in the method for producing an oral drinking water solution with reduced purine alkaloid content.

[0034] In the adsorption method of purine alkaloids of the present invention, the purine alkaloids in the oral drinking water solution are adsorbed by the metal organic framework, and the purine alkaloids can be partially or completely removed from the oral drinking water solution. In addition, the purine alkaloids adsorbed and removed by this method can be detached from the metal organic framework by utilizing the characteristics of the metal organic framework. Therefore, another embodiment of the present invention is a method for detaching the adsorbed purine alkaloids from the metal organic framework using the above-mentioned method of the present invention (the adsorption method of purine alkaloids). The detached purine alkaloids can be used for other purposes. In addition, the metal organic framework from which the purine alkaloids are detached can be reused in the adsorption method of purine alkaloids.

[0035] In addition, another embodiment of the present invention is a purine alkaloid adsorbent, characterized in that it contains a metal organic framework, the metal organic framework contains Zr 4+ Cr 3+ or Al 3+ The adsorbent of the present invention contains a terephthalate ion as a metal ion and a terephthalate ion as an organic ligand. Purine alkaloids can be effectively removed from oral drinking water solutions by using the adsorbent of the present invention. Furthermore, the adsorbent of the present invention can also release temporarily adsorbed purine alkaloids. The metal-organic framework and its materials that constitute the adsorbent of the present invention are as described above in the method for producing an oral drinking water solution with reduced purine alkaloid content, or can be understood from the description thereof. Example

[0036] The following experimental examples are provided to specifically illustrate the details of the present invention, but the present invention is not limited thereto. In addition, in this specification, unless otherwise specified, numerical ranges are described in a manner that includes the endpoints thereof.

[0037] Experimental Example 1. Screening of MOFs with Caffeine Adsorption Capacity 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 investigated. MOFs produced by Atomis Co., Ltd. were used, and the caffeine adsorption capacity of the various MOFs shown in the table below was investigated.

[0038] [Table 1] No. MOF Metal ions Ligand precursor Pore diameter [nm] AP0005 MOF-801 Z14+ Fumaric acid 0.74 AP0010 UiO-66 Zr4+ Terephthalic acid 0.87 AP5018 MIL-88B Fe3+ Terephthalic acid 0.91 AP0013 MIL-101(Cr) Cr3+ Terephthalic acid 3.62 AP5013 MIL-53(Al) Al3+ Terephthalic acid 0.75 AP5015 Al(fumarate) Al3+ Fumaric acid 0.58 AP5020 CAU-10-H Al3+ Isophthalic acid 0.6 AP0008 ZIF-8 Zn2+ 2-Methylimidazole 1.13 AP0082 CALF-20 Zn2+ 1,2,3-triazole, oxalic acid 0.44

[0039] 1g of each of the above MOFs was added to 50g of a caffeine aqueous solution with a caffeine concentration of 600mg / L. The MOF-added caffeine aqueous solution 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 recovered MOF-containing caffeine aqueous solution were measured. The caffeine concentration was determined by HPLC using anhydrous caffeine in the solution at the Japan Food Analysis Center. The caffeine concentration measurement conditions are shown below. Pretreatment: dilute with methanol solution Instrument used: HPLC LC-20AD (Shimadzu Corporation) Column: CAPCELL PAK C18 MG 5μm (diameter 3mm×15cm) (Shiseido) Mobile phase: 0.01 mol ammonium acetate and methanol mixture Testing instrument: UV-visible spectrophotometer SPD-20A (Shimadzu Corporation) Detection wavelength: 270nm

[0040] The specific gravity of the caffeine aqueous solution after MOF recovery was set to 1.0, and the caffeine weight was calculated from the above caffeine concentration. The difference between the caffeine weight after MOF recovery and the blank control (no MOF addition) was used as the caffeine adsorption amount, and the caffeine adsorption amount per 1g of MOF was measured. In addition, the ratio of caffeine adsorption to the caffeine weight of the blank control (no MOF addition) was measured as the caffeine removal ability. The results are shown below.

[0041] [Table 2]

[0042] As shown above, among the 10 MOFs investigated, AP0010, AP0013, AP5013, and AP0008 have high caffeine adsorption capacity.

[0043] Experimental Example 2. Selective Separation Ability of Caffeine For the four MOFs obtained in the above experiment, the selective separation ability of caffeine was investigated using coffee extract. The coffee extract used was a commercially available canned coffee beverage (Suntory, trade name: Boss Unsweetened Black Coffee). 1 g of MOF was added to 50 g of the coffee extract and allowed to stand at room temperature for 24 hours. The MOF was 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. In addition, 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 content of organic acids was determined using the HPLC method, and the measurement conditions are as follows. Measuring device: HPLC LC-20AD (Shimadzu Corporation) Detector: Conductivity detector CDD-10A VP (Shimadzu Corporation) Column: Shim-pack SCR-102H (8 mm × 300 mm, 7 μm) (Shimadzu Corporation), two in series. Guard column: Shim-pack SCR-102H (6 mm × 50 mm, 7 μm) (Shimadzu Corporation) Column oven temperature: 50°C Mobile phase: p-toluenesulfonic acid aqueous solution (5 mmol / L) Detection 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): 0.8ml / min Pump flow rate (test liquid): 0.8ml / min Injection volume: 10 μl Polarity: + Unit temperature: Automatic setting

[0044] The results are shown in the table below. Figure 1 .

[0045] [Table 3]

[0046] [Table 4]

[0047] The above results indicate that AP0008's caffeine adsorption capacity decreases when coffee extract is used. Regarding MOFs other than AP0008, analysis of various organic acids in coffee extracts after MOF addition and comparison with blank controls (no MOF addition) revealed that AP5013 exhibited the highest caffeine adsorption selectivity, followed by AP0013.

[0048] Furthermore, the results of various organic acid concentration measurements show that AP0010 detected low levels of almost all organic acids compared to the blank control (no MOF added), indicating that not only caffeine in the coffee extract was adsorbed, but also the organic acids. These results indicate that AP0013 and AP5013 measured relatively similar organic acid concentrations compared to the blank control, indicating that they can selectively separate and adsorb caffeine. When comparing AP0013 and AP5013, comparison with the blank control suggests that AP5013 exhibits higher caffeine selective separation capabilities. Furthermore, AP0008 measured organic acid concentrations that were essentially the same as the blank control, yet showed no caffeine adsorption, suggesting that AP0008 is unsuitable for use in coffee extracts.

[0049] Experimental Example 3-1. Caffeine Adsorption Capacity (1) Regarding the above-mentioned four types of MOF, a test for confirming the adsorption capacity of caffeine was carried out. 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, respectively. The MOF-added caffeine aqueous solution was allowed to stand at room temperature for 24 hours, and then the MOF was separated and recovered. In the same manner 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 MOF addition and the weight of caffeine after MOF recovery was taken as the caffeine adsorption amount, and the caffeine adsorption amount per 1 g of MOF was investigated. The results are shown in the following table and Figure 2 .

[0050] [Table 5]

[0051] The above results show that AP5013 has the highest caffeine adsorption capacity, followed by AP0013. This suggests that AP5013 is likely to be the adsorbent capable of adsorbing the most caffeine.

[0052] Experimental Example 3-2. Caffeine Adsorption Capacity (2) Following the above-mentioned Experimental Example 3-1, the caffeine adsorption capacity of the MOFs AP0010, AP0013, and AP5013 was further investigated. Aqueous caffeine 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 MOF-added caffeine aqueous solution was allowed to stand at room temperature for 24 hours, and then the MOF was separated and recovered. The weight and caffeine concentration of the caffeine aqueous solution after MOF recovery were measured. In addition, the caffeine weight was calculated from the caffeine concentration after MOF recovery to investigate the caffeine adsorption amount per 1 g of MOF. In addition, the concentration measurement or numerical calculation was carried out in the same manner as in Experimental Example 3-1, and the number of experiments in this experimental example was N=3. The results are shown in the table below.

[0053] [Table 6]

[0054] As shown above, even when the caffeine concentration of the caffeine aqueous solution was changed, 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 sample was prepared. Figure 3 The adsorption isotherm of caffeine is shown.

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

[0056] In addition, the recovered MOF was washed three times with 50 mL of distilled water to remove various components from the beverage attached to the MOF surface. The washed MOF and 50 mL of distilled water were placed in a 100 mL reagent bottle and allowed to stand at 90°C for 6 hours. It was then quickly filtered, and the resulting filtrate was used as a beverage sample after detachment. The caffeine concentration in the sample was measured in the same way as in Experimental Example 1. The weight of caffeine in the beverage sample after detachment was calculated from the measured value of the caffeine concentration, and the amount of caffeine detached per 1 g of MOF and the caffeine detachment ratio were investigated. The number of experiments was set to N = 3, and the average value was calculated.

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

[0058] [Table 7]

[0059] [Table 8]

[0060] As shown above, AP0010, AP0013, and AP5013 all exhibited high caffeine adsorption capabilities in various beverages. Furthermore, all tested MOFs demonstrated the ability to desorb adsorbed caffeine. Measurements of various organic acid concentrations revealed that AP5013 produced relatively similar organic acid concentrations compared to the blank control, demonstrating the highest caffeine selectivity of the three MOFs.

Claims

1. A method for producing an oral drinking water solution with reduced purine alkaloids, characterized in that: Containing Zr 4+ Cr 3+ or Al 3+ The invention relates to a process for contacting a metal organic framework containing terephthalate ions as metal ions and organic ligands with an oral drinking water solution.

2. The method according to claim 1, characterized in that The oral drinking water solution contains purine alkaloids.

3. The method according to claim 2, characterized in that The content of purine alkaloids in the oral drinking water solution is below 2000 ppm.

4. The method according to claim 1, wherein 0.01 to 20 parts by weight of the metal organic framework is brought into contact with 100 parts by weight of the oral drinking water solution.

5. The method according to any one of claims 1 to 4, characterized in that The pore size of the metal-organic framework is 0.2 to 6 nm.

6. The method according to any one of claims 1 to 4, characterized in that The purine alkaloid is caffeine.

7. The method according to any one of claims 1 to 4, characterized in that Oral drinking water solution as a beverage.

8. The method according to claim 7, characterized in that The beverage is coffee or tea.

9. A purine alkaloid-reduced oral drinking water solution, characterized in that By including Zr 4+ Cr 3+ or Al 3+ The invention discloses a method for producing a metal organic framework comprising a metal ion and a terephthalate ion as an organic ligand, and a step of contacting the metal organic framework with an oral drinking water solution.

10. A method for adsorbing purine alkaloids, characterized in that: Containing Zr 4+ Cr 3+ or Al 3+ The invention relates to a process for contacting a metal organic framework containing terephthalate ions as metal ions and organic ligands with an oral drinking water solution.

11. A purine alkaloid adsorbent, characterized in that: Contains a metal organic framework containing Zr 4+ Cr 3+ or Al 3+ As metal ions, and contains terephthalate ions as organic ligands.

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