Organometallic material of the MOF type, production method and fertilisation method

Abstract

The present invention relates to a composition for the direct formation, in a single step and at room temperature, of an amorphous MOF based on humic acids, which MOF consists of a phosphate-metal-humic complex. The present invention also relates to the method for obtaining this composition, and to the use thereof for efficient crop fertilisation.

Description

Description Title of the invention: MOF-type organo-metallic material, manufacturing process and fertilization process Technical Field

[0001] The present invention relates to materials whose structure includes an organo-metallic network (“Metal Organic Framework” in English and whose acronym is MOF) derived from the complexation of phosphorus and nitrogen sources with a humic system via metallic bridges.

[0002] Furthermore, the present invention relates to a method of manufacturing this product which can be used as a fertilizer for plant nutrition. Previous technique

[0003] Solid organic metal-on-focal (MOF) networks are porous crystalline materials composed of a metal that acts as a node and a polydentate organic ligand that binds the metal. The self-assembly of the metal and organic ligand generates a one-, two-, or three-dimensional network. This structure includes internal coordination bonds and intermolecular and weak bonds (hydrogen bonds or Pi-Pi interactions). The metal and organic ligand in MOFs can vary, with iron(III) being the most commonly used metal. The most common organic ligands are carboxylic acids, pyridines, cyano compounds, polyamines, benzenes, sulfonates, and ethers. Among the carboxylic acids, benzene derivatives of carboxylic acid, ethylenediaminetetraacetic acid, oxalic acid, and citric acid have been studied.

[0004] MOF materials are characterized by high porosity, high chemical stability, and high thermal stability. Due to their large surface area, large pore size, and crystalline nature, MOF materials allow the incorporation of molecules or ions both within the atomic lattice comprising the metal and the organic ligand, and within the internal cavities of the crystals. These unique properties offer a wide range of functionalities and technical applications for MOFs, such as gas storage, Drug administration and toxin elimination. The use of MOFs as fertilizers has also been studied.

[0005] For example, Anstoetz M. et al. reported in Journal of Material Science, 2016;51(20):9239-52 and in PLOS One, 2015 Dec 1; 10(12) the synthesis and characterization of a MOF using oxalic acid as an organic ligand. Phosphate and amine were then added to the MOF, resulting in an oxalate-phosphate-amine MOF (OPA-MOF). The authors also investigated the properties of this particular MOF as a slow-release nitrogen and phosphorus fertilizer. They observed that the structure of this OPA-MOF is crystalline and comprises FeOe units with bidentate oxalate bridges linking adjacent iron centers. Furthermore, the PÛ4 units share their oxygens with the FeOe units. OPA-MOFs exhibit a very stable crystalline morphology. However, they have the disadvantage of being poorly soluble and having a low capacity to encapsulate bioactive substances.The authors demonstrated that urea hydrolysis is rapid with OPA-MOF, while ammonium-to-nitrate conversion is significantly lower compared to urea alone. However, phosphorus uptake and yield with OPA-MOF treatment are considerably lower than those obtained with conventional fertilizer treatment. In conclusion, OPA-MOF has shown potential as a nitrogen fertilizer but suffers from low phosphorus bioavailability.

[0006] Later, CN111574284 described the synthesis of MOFs using citric acid instead of oxalic acid as the organic ligand for the carboxylic acid. Phosphate and urea were also included in the MOF to obtain a citrate-phosphate-amine MOF.

[0007] Prior art carboxylic acid MOFs have several drawbacks. They are prepared using a complicated and expensive hydrothermal method. This method involves multiple steps, requires high temperatures and pressures, and expensive reagents.

[0008] In particular, carboxylic acid-based MOF fertilizers such as prior art oxalate-phosphate-amine MOF and citrate-phosphate-amine MOF are expensive to produce, making them difficult to apply on a large scale in the agrochemical field. In addition, these MOFs are poorly soluble in water and their phosphorus bioavailability is poor.

[0009] Another recent variant of MOF, called "amorphous MOF," retains the building blocks and connectivity of crystalline lenses without large-scale periodic order. They are typically obtained by amorphizing a crystalline MOF by applying pressure, heating, ball milling, grinding, radiation, or electrical discharge. For example, Lohe et al. reported a two-step synthesis of a benzene tricarboxylic acid-iron nitrate MOF aerogel for catalytic applications in Chem. Commun. 2009, 40: 6056. The two-step protocol combines sol-gel and supercritical CO2 drying. The amorphous structure of such a MOF has been considered a problem to be solved. Another amorphous MOF based on an alginate-benzene tricarboxylic acid-iron-ammonium MOF aerogel was prepared by Wu et al. (Int. J. Biol. Macromol., 2020 Feb, 15: 145:1073-1079) and proposed as a slow-release fertilizer.

[0010] Amorphous MOFs are prepared by a two-step synthesis involving a chemical reaction to create a crystalline MOF and subsequent processing of the crystalline MOF using an energy-intensive method. This method prevents the large-scale production required in most industrial sectors.

[0011] It is therefore necessary to propose new MOF products that can be produced under mild synthesis conditions, with a limited number of steps, using inexpensive reagents and non-toxic solvents. It would be advantageous to develop a cost-effective manufacturing method for an MOF product that allows for large-scale production.

[0012] In addition, it would be interesting to propose a phosphorus-amine-metal MOF with improved fertilizing properties, such as high phosphorus bioavailability. Description of the invention

[0013] The present invention provides a solution to these needs and relates to a simple method for preparing an organometallic compound, such as a material MOF phosphorus-amine, without having to resort to energy-intensive physical treatments and multiple chemical steps.

[0014] The method of the invention is environmentally friendly and cost-effective. Indeed, only one chemical step is required, and it utilizes a solvent precipitation process. Water can advantageously be used as the solvent. The method may also include a physical step for separating the solid precipitate from the liquid phase.

[0015] The manufacturing method for the material can advantageously be carried out at low temperatures. In contrast, the prior art oxalate-phosphoramine and citrate-phosphoramine MOFs require high temperatures and pressures, as well as several steps.

[0016] The invention also proposes an organometallic material containing phosphorus and amine that incorporates humic acid substances as polydentate organic ligands to form a material with a MOF structure. Humic acids, which occur in nature, are inexpensive and environmentally friendly. The phosphorus-amine MOF product based on humic substances may include amorphous domains, particularly due to the incorporation of humic substances, which offers several advantages. First, the MOF-type materials of the invention can provide more bioavailable nitrogen and phosphorus. Second, they can encapsulate bioactive substances. For example, various biomolecules that stimulate plant growth can be incorporated. Furthermore, the phosphorus and nitrogen nutrients are incorporated into the MOF structure, resulting in a monolithic fertilizer composition with a homogeneous nutrient distribution. Brief description of the drawings

[0017] Figure 1 is a diagram representing several steps of a method for manufacturing a MOF product according to the invention.

[0018] Figure 2 is an X-ray diffractogram of a physical mixture composed of chemical reagents used to prepare the MOF.

[0019] Figure 3 is an X-ray diffractogram of a MOF product according to the invention.

[0020] Figure 4 is a SEM image of a physical mixture composed of chemical reagents used to prepare the MOF.

[0021] Figure 5 is a SEM image of a MOF product according to the invention.

[0022] Figure 6 is an EDX map of a physical mixture composed of chemical reagents used to prepare the MOF.

[0023] Figure 7 is an EDX map of a MOF product according to the invention.

[0024] Figure 8 is an XPS spectrum of a physical mixture composed of chemical reagents used to prepare the MOF.

[0025] Figure 9 is an XPS spectrum of a MOF product according to the invention.

[0026] Figure 10 shows four curves representing the release kinetics of P from a MOF product according to the invention in different media which differ in pH value.

[0027] Figure 11 is a nitrogen volatilization curve in a soil in the presence of MOF or in the presence of urea.

[0028] Figure 12 compares the weights of the aerial parts of a plant receiving a MOF product according to the invention or a simple superphosphate.

[0029] Figure 13 compares the weight of the roots of a plant receiving a MOF product according to the invention or a simple superphosphate.

[0030] Figure 14 shows an SEM image of an organometallic product from the prior art.

[0031] Figure 15 shows an SEM image of an organometallic product of MOF type according to the invention.

[0032] Figure 16 is an X-ray diffractogram of a prior art organometallic product.

[0033] Figure 17 shows an SEM image of an organometallic product from the prior art.

[0034] Figure 18 is an X-ray diffractogram of a prior art organometallic product. Description of the implementation methods

[0035] A first object of the invention is an organo-metallic material of the MOF type comprising phosphorus, nitrogen, a humic substance and at least one metal selected from iron, copper, manganese and zinc, this organo- metallic having a porous structure, said porous structure preferably being at least partially amorphous.

[0036] An "organometallic material of the MOF type" is defined in the present invention as a solid porous product comprising inorganic nodes that are linked by polydentate organic ligands in a three-dimensional arrangement. The nodes comprise a metal ion or a metal salt, such as iron phosphate, for example.

[0037] The MOF according to the invention is preferably insoluble in water. It can be insoluble in an aqueous solution having a pH less than 7.

[0038] The organometallic material is preferably a porous material comprising internal pores in its structure. The porosity of the MOF can be measured and / or observed by any method known to those skilled in the art, such as microscopy, the BET (Brunauer, Emmett and Teller) method for measuring specific surface area, the BJH (Barrett, Joyner and Halenda) method for measuring pore size and volume, or the Horvath-Kawazoe (HK) method for measuring pore volume.

[0039] For example, the porosity of the MOF can be at least one physical parameter chosen from specific surface area, pore distribution, mean pore width, mean pore diameter, and pore volume. A MOF porosity value can be defined as at least one numerical value of at least one parameter. The MOF porosity value can be a set of numerical values ​​for several parameters. The numerical value of a parameter can be an average value or a range of values. The material of the invention advantageously exhibits high internal porosity.

[0040] The porosity value of a MOF can be chosen from an average pore width, an average pore diameter, an average pore volume, or a combination of these values. According to the IUPAC definition, a MOF can be classified as a mesoporous structure when the average pore size is between 3 nm and 10 nm.

[0041] The porosity of the MOF according to the invention, defined as one or more parameters defined above, is greater than that of the starting compounds used for its preparation. In particular, it is greater than that of the substance humic. The porosity of the MOF according to the invention is preferably greater than the porosity of prior art compounds in the form of a complex comprising phosphorus, a metal and a humic substance.

[0042] The average pore width of the porous structure can be between 3.0 nm and 10.0 nm, between 4.0 nm and 9.0 nm or between 5.0 nm and 8.0 nm, particularly when the average pore width is measured by the BJH method.

[0043] The average diameter of the pores of the porous structure can be between 4.0 nm and 6.0 nm, between 4.5 nm and 6 nm or between 4.7 nm and 5.2 nm, particularly when the average diameter is measured by the BJH method.

[0044] The pore volume of the porous structure can be between 0.35 cm 3 / g and 0.50 cm 3 / g, for example between 0.40 cm 3 / g and 0.48 cm 3 / g or between 0.44 cm 3 / g and 0.48 cm 3 / g, particularly when the pore volume is measured by the BJH method.

[0045] The pore volume of the porous structure can be between 0.40 cm 3 / g and 0.60 cm 3 / g, for example between 0.45 cm 3 / g and 0.55 cm 3 / g, especially when the pore volume is measured by the HK method.

[0046] In a particular embodiment, the average pore width of the porous structure is between 3 nm and 10 nm, the average pore diameter of the porous structure is between 4 nm and 6 nm, and the average pore volume of the porous structure is between 0.35 cm³ 3 / g and 0.50 cm 3 / g.

[0047] MOF has a high specific surface area compared to the metallic humic substance complexes of the prior art, which is generally on the order of 40 m². 2 / g at 90 m 2 / g. The specific surface area of ​​the MOF is, for example, greater than a value chosen from the group consisting of 100 m 2 / g, 150 m 2 / g, 200 m 2 / g, 250 m 2 / g, 300 m 2 / g or 350 m 2 / g. It is preferably less than 1000 m 2 / g. The specific surface area can be measured by any method known to a person skilled in the art.

[0048] The MOF of the invention may be amorphous or at least partially amorphous in cases where certain periodic units may be present on a limited or large scale. The presence of amorphous domains can be observed by any method known to those skilled in the art, such as X-ray imaging.

[0049] The MOF product composition may include 10% to 15% atomic metal, 10% to 15% atomic phosphorus and 10% to 15% atomic carbon.

[0050] The organic ligand present in the MOF product of the invention is a humic substance (HS) which may be a humic acid, a fulvic acid or mixtures thereof.

[0051] Although the structure and properties of a given SH depend on the source of soil and water and specific extraction conditions, the average properties of SHs from different origins are nevertheless remarkably similar.

[0052] Humic acid (HA) can be extracted from organic matter, such as peat, leonardite, soils, and composts of animal and plant waste, using an alkaline agent such as sodium hydroxide (NaOH) or potassium hydroxide (KOH). The alkaline organic extract can then be separated by acidification into humic acids (soluble in water at alkaline pH but insoluble at acidic pH), fulvic acid (soluble in water at any pH), and humin (a residue insoluble in water at any pH). The humic acids can be further separated into gray humic acids (insoluble at neutral pH and ionic strengths greater than 1 M) and brown humic acids (soluble at neutral pH and ionic strengths greater than 1 M).

[0053] The constituent metal of the MOF, in the case of a single metal, or the constituent metals of the MOF, in the case of multiple metals, may be selected from Fe(III), Fe(II), Cu(II), Mn(II), and Zn(II). Calcium and magnesium are not preferred metals for the MOF product of the invention, as they can slow down the formation of the organometallic ligand network. Inorganic salts of calcium and magnesium, such as calcium nitrate, calcium chloride, magnesium nitrate, and magnesium chlorides, tend to flocculate humic acids and form aggregates of high molecular size.

[0054] Fe(III) can be advantageously used to increase the physicochemical stability of MOF.

[0055] The chemical composition of the organo-metallic material of the invention can be characterized by a metal:phosphorus molar ratio between 1:4 and 2:1, between 1:4 and 3:2, between 1:4 and 1:1, between 3:4 and 5:4, between 1:3 and 1:2, and preferably about 1:1, and / or a metal-humic substance mass ratio between 1:5 and 1:2, preferably between 1:4 and 1:2, and preferably about 1:3.

[0056] A second object of the present invention is a process for manufacturing an organo-metallic material comprising a step of preparing an aqueous solution comprising a water-soluble phosphorus compound, a water-soluble nitrogen compound and a water-soluble humic substance, a step of incorporating at least one water-soluble metallic salt into said aqueous solution, and a step of forming a precipitate and an aqueous phase, the incorporation step being stopped when the aqueous phase has a final pH between 3.0 and 9.0.

[0057] Another process for manufacturing an organometallic material involves a step of mixing a water-soluble or water-insoluble phosphorus compound with a water-soluble nitrogen compound, a water-soluble or water-insoluble humic substance, and a water-soluble metal salt or water-insoluble metal oxide, in the presence of a strong acid in sufficient quantity to ensure that the pH is between 3.0 and 9.0 at the end of the reaction. This process is particularly advantageous when the phosphorus compound, the humic substance, and / or the metal source is water-insoluble.

[0058] This variant of the manufacturing process for the organometallic material of the invention can be carried out by simultaneously combining all the reactants, without premixing two or three of them. The reactants are preferably introduced into a reactor at ambient temperature and atmospheric pressure, and the mixture is kept under stirring until the reaction is complete.

[0059] A person skilled in the art can choose a strong acid from their general knowledge, such as sulfuric acid or phosphoric acid, for example.

[0060] An insoluble phosphorus compound is, for example, a natural phosphate or a metallic phosphate. The term "metal oxide" covers compounds containing a metal-oxygen bond, such as metal hydroxides, metal oxides in the strict sense, and Metallic carbonates. A metallic oxide is, for example, an iron hydroxide, an iron oxide, or an iron carbonate.

[0061] The preparation and incorporation steps of at least one water-soluble metallic salt are preferably carried out by slow and controlled addition. Those skilled in the art will know how to adjust the duration of the incorporation step.

[0062] The organometallic material is advantageously a MOF that is formed simultaneously with the mixture of reactants in the same reactor as a precipitate, which can then be separated from the liquid by centrifugation or filtration. Before separating the filtrate, the suspension can be allowed to settle for an appropriate time, preferably 2 hours. According to one embodiment of the invention, the precipitate is separated from the aqueous phase by centrifugation and then dried.

[0063] The reaction is preferably carried out at ambient temperature in any type of stirred reactor. However, the temperature can be raised to a maximum of 100 °C. Therefore, the preparation and incorporation steps can advantageously be carried out at atmospheric pressure and at a temperature below 100 °C, preferably below 60 °C, and even more preferably between 20 °C and 30 °C.

[0064] According to a preferred embodiment, the aqueous solution comprises a water-soluble phosphorus compound, a water-soluble nitrogen compound and a water-soluble humic substance at a pH greater than 7.0.

[0065] The pH of the aqueous solution can be adjusted using an alkaline or acidic solution, as appropriate, during the incorporation step.

[0066] The incorporation step is stopped when the aqueous phase has a final pH between 3.0 and 9.0, preferably between 3.0 and 7.0, between 3.0 and 6.0, between 3.5 and 7.0, and even more preferably between 4.0 and 4.5. The final pH may be between 3 and 7. The final pH may also be between 3 and 4, between 3.0 and 5.4, between 3.0 and 5.0, or between 3.0 and 4.4.

[0067] The pH is advantageously acidic to obtain an insoluble compound comprising both the metal (M) and phosphorus (P). Above this value, the precipitate may not form, and the product obtained will be a complex of the metal with the humic substance, which may include COM bonds. This complex is soluble in water, not a complex of the metal with the humic substance and the phosphorus can include COMOP bonds, which complex is insoluble in water.

[0068] The pH is preferably greater than 3 in order to promote the formation of chemical bonds between the humic substance and the metal, and between the metal and phosphorus.

[0069] The quantities of humic substance, metallic salt and phosphorus compound used to prepare the material can be chosen so that the metal:phosphorus molar ratio is between 1:4 and 2:1, between 1:4 and 3:2. The metal:phosphorus molar ratio can also be between 1:4 and 1:1, preferably between 1:3 and 1:2, and preferably about 1:1, and the metal:humic substance mass ratio is between 1:5 and 1:2, preferably between 1:4 and 1:2, and preferably about 1:3.

[0070] In a particular case, where the material can be used as a fertilizer or can be incorporated into a fertilizer composition, this description discloses a set of four reagents to be used in a method of manufacturing a fertilizer, the four reagents being a water-soluble source of phosphorus, a water-soluble source of nitrogen, a water-soluble humic substance comprising humic acids and / or fulvic acids, and an aqueous solution of a metal, wherein a metal:phosphorus molar ratio is 1:4 to 1:1, preferably 1:3 to 1:2, and preferably about 1:1, and wherein a metal / humic substance mass ratio is 1:5 to 1:2, preferably 1:4 to 1:2, and preferably about 1:3.

[0071] The water-soluble humic substance can be selected from the water-soluble forms of humic acids, fulvic acids, and mixtures thereof. The water-soluble humic substance used to prepare the aqueous solution can be a commercially available product, either as a dry solid or as an aqueous solution of humic substances. Commercially available humic substances include, for example, potassium humates or sodium humates. The manufacturing process of the present invention may also include an additional step of preparing the water-soluble humic substance.

[0072] Water-soluble humic substances can be extracted from natural raw materials and possibly purified using methods well known to those skilled in the art (Stevenson, 1994, Humus Chemistry, Second Edition, Wiley, New York). Alkaline solutions can be used to extract water-soluble humic substances from raw organic matter. These alkaline solutions can be chosen from sodium hydroxide, ammonium hydroxide, potassium hydroxide, and mixtures thereof. The alkaline solution can optionally be used in the presence of a chelating agent such as pyrophosphates, synthetic chelates (EDTA, DTPA), and others. [0073)11 It is possible to prepare a suspension of the crude organic material in water and then mix it with the alkaline solution. The temperature is generally between about 5°C and about 100°C, preferably between about 10°C and about 60°C, and more preferably between about 20°C and about 40°C. Furthermore, the reaction is carried out for at least 1 minute, preferably for at least about 5 minutes, and preferably for at least 15 minutes.

[0074] The water-soluble humic substance can be obtained from a raw material chosen from peat, leonardite, lignite, charcoal, biochar, hydrochar, urban and sewage sludge, digestate and compost.

[0075] The humic substance obtained from organic matter can be in liquid form, for example as a solution or suspension containing an insoluble organic phase and a liquid phase comprising water-soluble humic substances. The humic substance can be in solid form if the solution or suspension described above is dried.

[0076] In one embodiment, the humic substance used as a reagent in the process of the invention is a water-soluble humic substance, preferably a humate salt, such as sodium humate or potassium humate. In another embodiment, a water-insoluble humic substance and a strong acid are used as reagents to form the water-soluble humic substance in the reaction medium.

[0077] According to one embodiment of the invention, the aqueous solution comprising a water-soluble phosphorus compound, a water-soluble nitrogen compound and a water-soluble humic substance is obtained by a step a) of preparing an aqueous solution comprising the water-soluble phosphorus compound and the water-soluble nitrogen compound, and a step b) of mixing the aqueous solution obtained in step a) with an aqueous solution of the water-soluble humic substance.

[0078] The aqueous solution of the water-soluble humic substance may have a pH greater than 6.5, preferably from 10.0 to 12.0.

[0079] The aqueous solution comprising the water-soluble phosphorus compound and the water-soluble nitrogen compound may have a pH between 7.0 and 9.0, preferably around 8.0. A person skilled in the art can adjust the optimal pH value according to the chosen water-soluble phosphorus compound and the chosen water-soluble nitrogen compound.

[0080] In one embodiment, the phosphorus compound used as a reagent in the process of the invention is a water-soluble phosphorus compound. In another embodiment, a water-insoluble phosphorus compound and a strong acid are used as reagents to form a water-soluble phosphorus compound in the reaction medium. A person skilled in the art will choose a water-insoluble phosphorus compound based on their general knowledge.

[0081] The water-soluble phosphorus compound, chosen as a reactant or as a reaction product of a water-insoluble phosphorus compound and a strong acid, is preferably a mineral phosphorus compound, preferably a mineral phosphate chosen from the group consisting of phosphoric acid and its mineral salts, said mineral salts being hydrated salts or anhydrous salts.

[0082] The mineral salt of phosphoric acid includes potassium phosphate, potassium hydrogen phosphate, sodium phosphate, potassium hydrogen phosphate, monocalcium phosphate, their hydrates and mixtures thereof.

[0083] The water-soluble metallic salt is preferably a mineral metallic salt such as a chloride metal salt, for example ferric chloride or ferrous chloride. Ferric chloride allows the production of a MOF compound with very good physicochemical stability.

[0084] The water-soluble phosphorus compound is preferably chosen from the group consisting of phosphoric acid and its mineral salts, the latter being hydrated or anhydrous salts. The mineral salt of phosphoric acid may be, for example, potassium phosphate, potassium hydrogen phosphate, sodium phosphate, potassium hydrogen phosphate, their hydrates, and mixtures thereof.

[0085] The water-soluble phosphorus compound is preferably phosphoric acid.

[0086] The water-soluble nitrogen compound includes an organic source of nitrogen, such as urea, or a nitrogenous mineral salt, such as a mineral ammonium salt.

[0087] In a particular case of the invention, the water-soluble phosphorus compound comprises a water-soluble nitrogen compound, such as ammonium phosphate or diammonium phosphate (also called ammonium hydrogen phosphate of formula (NF HPO₄)). Alternatively, the water-soluble nitrogen compound may comprise a water-soluble phosphorus compound, such as ammonium phosphate or diammonium phosphate.

[0088] According to one embodiment of the manufacturing process of the invention, the water-soluble phosphorus compound comprises potassium phosphate, the nitrogen source comprises urea, the water-soluble humic substance comprises humic acid, and the metallic salt is ferric chloride.

[0089] The MOF product of the invention can be used in various technical fields such as energy (storage, sensors and catalysts), biomedicine (drug delivery), the environment (gas storage, toxin removal, carbon dioxide absorption and water treatment) and agriculture (fertilizers).

[0090] According to a particular embodiment, the MOF product can be used as a fertilizer or incorporated into a fertilizer composition. Therefore, the present invention also relates to a method of crop fertilization that includes a step of applying an organo-metallic structural product as described above to soil and / or a crop.

[0091] In the context of this description, the term "fertilizer" refers to any product intended to improve plant nutrition.

[0092] In the context of the present invention, the term "plant" refers to the plant considered as a whole, including its root system, vegetative system and fruits.

[0093] In the expression of a range of numerical values, the term "between ... and ..." may include or exclude the bounds.

[0094] The present invention is described by the following examples and experiments. Unless otherwise indicated, the temperature is between 20°C and 25°C and the pressure is 1 atm. Example 1: A MOF product was synthesized and characterized by elemental analysis, XDR, XPS, SEM, water solubility and NAC solubility. The physicochemical properties of MOF were compared to the physicochemical properties of a mixture composed of the chemical reagents (in solid form and in dry state) that were used to synthesize the MOF product. In vitro tests of phosphorus release and nitrogen protection were carried out. Furthermore, the agrochemical potential of MOF was demonstrated in an in vivo test. Preparation of the physical mixture according to the prior art

[0095] 47 g of humic acid in KOH IM (47 g in 350 mL), a solution (ii) of KH2PO4 (38 g in 600 mL) and urea (28 g / L urea), and a solution (iii) of FeCh (45 g in 50 mL) were prepared. Preparation of the MOF material according to the invention

[0096] Humic acid extracted from leonardite (Czech Republic origin) was used as the organic ligand. The nitrogen source was urea, and the phosphorus source was monopotassium phosphate. The metal cation was Fe(III), added as FeCh.

[0097] To carry out the synthesis, a solution (i) of humic acid in KOH IM (47g in 350 mL), a solution (ii) of KH2PO4 (38g in 600mL) and urea (28 g / L urea), and a solution (iii) of FeCh (45g in 50 mL) were prepared. After After mixing solutions (i) and (ii), solution (iii) is added gradually, controlling the final pH (4.20), and a precipitate forms. A diagram of the different steps is shown in Figure 1. After precipitation, the solid is centrifuged, isolated, and dried. The metal-to-phosphorus molar ratio is approximately 1:1, and the metal-to-humic substance mass ratio is approximately 1:3. Elementary Analysis

[0098] Elemental analysis of the precipitate obtained includes the presence of C (14.90±1.14%), which indicates the incorporation of humic acid into the MOF network. Similarly, 12.64±0.88% Fe, 15.18±1.00% K, 2.68±0.50% N and 15.91±0.71% P2O5 are detected, which shows the presence of potassium phosphate, N and Fe (metal bridge).

[0099] The EDX elemental maps show the distribution of nutrients in each sample. Thus, the distribution of nutrients in the MOF (see Figure 7) is higher than the distribution in the physical mixture (see Figure 6), suggesting their incorporation into the formed structure. Solubility Method : The concentrations of total phosphorus (P), zinc (Zn) and magnesium (Mg) (HCl 35%), soluble in water and soluble in neutral ammonium citrate (0.96 M; temperature 65 °C) were analyzed according to official analytical methods (Métodos Oficiales de Anàlisis. Tomo III; Ministerio de agricultura, pesca y alimentacién; Secretarïa General Técnica Ministerio de Agricultura, Pesca y Alimentacién: Madrid, Spain, 1994, pp 565-578). One gram of the fed sample was heated with 100 ml of water (water-P) or NAC (NAC-P) or 20 ml of 37% HCl in 100 ml of water (Total-P) for 20 minutes (25 minutes for water-P) in a hot plate, diluted to 250 ml with water, filtered and determined the P by ICP-OES. Results : Table 1. Solubility of P in water and NAC

[0100] Regarding phosphorus solubility, it is observed that only 29.5% of the total phosphorus is soluble in water, while all of it is soluble in neutral ammonium citrate (NAC). NAC represents organic acids exuded by plants in cases of phosphorus deficiency. Therefore, the phosphorus soluble in NAC is higher than the phosphorus soluble in water. Consequently, the phosphorus soluble in NAC is potentially available to the plant. Thus, the solubility of MOF (monophosphate) in water and NAC suggests high plant availability and low fixation in the soil, resulting in reduced losses and, therefore, high fertilizer efficiency and low soil and water contamination. Structure: XRD, SEM and XPS

[0101] The X-ray diffractogram of MOF (Figure 3) reveals a less crystalline appearance than that of the physical mixture (PM) (Figure 2). Furthermore, crystalline phases associated with 2,4,5-trichlorophenoxyacetic acid, an organic compound with a structure analogous to that of humic acids, are observed. These two results confirm the presence and incorporation of the humic fraction in the MOF precipitate. This is consistent with the EDX results.

[0102] The SEM image of the physical mixture (Figure 4) shows a crystalline morphology with a predominance of KG, while the MOF image (Figure 5) shows a more amorphous appearance with various pores embedded in the structure. This is consistent with the XRD results and supports the formation of a porous structure.

[0103] Comparing the XPS spectra of PM (Figure 8) and MOF (Figure 9) shows a different chemical environment for iron. In PM, the Fe-Cl bond can be observed, whereas in MOF, Fe is associated with oxygen. Porosity Higher volume, width, and pore diameter are observed in the MOF compared to the physical mixture (PM), confirming the formation of a highly porous material during the MOF reaction. Table 2. Porosity of the MOF according to the invention and porosity of the physical mixture of chemical reagents used to prepare the MOF. Release of P in vitro Dissolution protocol: 0.4 g were added to 40 mL of the desired medium: water, 0.96 M sodium citrate at pH 4, pH 7.5, and pH 8. The mixture was stirred in a Reax2 Heidolph mixer at medium speed. Aliquots of the sample were taken at 5, 10, 15, 30, 50, 80, 120, and 240 minutes. Each aliquot was filtered through a 0.45 µm nylon filter, and the P value was determined by ICP-OES. Results :

[0104] The four curves are shown in Figure 10.

[0105] The kinetics of phosphorus (P) release from MOF in different media show that approximately 30% of the total P is released into water within 80 minutes. In sodium citrate, a controlled and gradual release of the P contained in the MOF is observed regardless of the pH. Theoretically, the curves show an initial zone of rapid release and a second zone of slower release. In all cases, the released MOF-P ranges between 70% and 100% of the total P, although there are differences in the time required for P release. Specifically, at pH 4, the MOF exhibits a maximum P release of 94% at 120 minutes, while at pH 7.5, 79% is released at 1440 minutes, and at pH 8, 75% is released at 240 minutes. The greater and faster release of P at an acidic pH may be due to the acid hydrolysis of MOF. Nitrogen volatilization in soil

[0106] In order to study the behavior of nitrogen contained in MOF, a soil incubation study was conducted to control nitrogen volatilization. Protocol: The volatilization model is based on that proposed by Zhepping et al. (1991). Air was circulated through a bottle of IL with water to create a humid atmosphere in another translucent bottle containing 150 g of soil and 300 mg of N / ha. The soil was activated with 10 ml of water. NH4 + The volatilized NH4 was trapped in a 1% H3PO4 solution. + was analyzed by UV-VIS spectrophotometry with an indophenol probe-based assay. A sample was taken daily for 10 days. Results :

[0107] Figure 11 shows a slower nitrogen loss in the presence of MOF compared to urea. Thus, the nitrogen volatilization slope from MOF is lower until day 8, where both treatments reach an asymptote. In vivo trials to evaluate agronomic potential

[0108] To study the ability of MOF to supply P to the plant, a hydroponic trial was carried out with Arabidopsis by applying MOF and comparing it to a conventional and soluble source of P, simple superphosphate (SSP). Protocol: A phosphorus-free nutrient solution with the following composition was used: MgSO4, KNO3, Ca(NO3)2, Fe-HBED, KCl, MnSO4, CuSO4, ZnSO4, H3BO3, and (NH4)6Mo7O24. 300 pM of phosphorus was supplied as MOF or SSP (simple superphosphate). Excess potassium was compensated with a KG solution. The growth chamber conditions consisted of a temperature between 18°C ​​and 21°C and a humidity of 75%. Harvesting took place 10 days after phosphorus application. Results :

[0109] The weights of the aerial part show the effectiveness of the supply of P with the MOF, obtaining results very similar to those of the application of the SSP, in both cases superior to the control without addition of P (see Figure 12). Regarding root weight, no change was observed between the control plants without P and those with SSP, but root development was greater in the plants treated with MOF. This may be due to the greater effort of the plants with MOF to mobilize the P contained in the MOF (see Figure 13). Example 2: Preparation of the MOF material according to the invention

[0110] Leonardite (from the Czech Republic), urea, iron hydroxide, natural phosphate, and 66% sulfuric acid were mixed simultaneously in a reactor at room temperature and atmospheric pressure. The reaction mixture was stirred. The amount of reactants was chosen so that the pH of the reaction mixture would be between 3 and 6 at the end of the reaction. A precipitate was observed, which was isolated by centrifugation and then dried.

[0111] The metal:phosphorus molar ratio was approximately 1:1, and the metal:humic substance mass ratio was approximately 1:3. Thermogravimetric analysis: product stability

[0112] The thermogravimetric analysis of the product of the invention, noted HA-MOF, was compared to that of a product noted "CKP" obtained according to the same process as that described above, with the difference that it did not contain leonardite (humic substance), and to that of the mixture of reagents which are in the solid state noted "PM" (with the exception of sulfuric acid).

[0113] The results revealed that, although both HA-MOF and PM contain HA in their chemical composition, their degradation profiles differ. The higher thermal stability of HA-MOF suggests the formation of a P-Fe-HA complex within it. CKP exhibits a different thermal stability, showing a greater weight loss at 406 °C. This weight loss is also present in other iron phosphates from the prior art. This peak could correspond to phosphate condensation. This weight loss is not present in HA-MOF, indicating that the chemical structures of HA-MOF and CKP are different. Amorphous structure

[0114] The XRD diffraction patterns of HA-MOF, PM, and CKP show different profiles. PM has a crystalline diffractogram, confirming the presence of urea and potassium monophosphate, which are included in the raw materials. The CKP diffractogram is also crystalline, with iron phosphates and potassium chloride. The XRD pattern of HA-MOF consists of a broad, amorphous background and a very weak crystalline phase, similar to that of CKP, namely iron phosphates and potassium chloride. The amorphous phase and the low amount of crystalline iron phosphates in HA-MOF indicate that the incorporation of HA promotes a highly distorted and less crystalline configuration. As with CKP, a potassium chloride fraction is also present. The amorphous pattern of HA-MOF indicates the incorporation of HA into its structure. Porosity

[0115] The porous structure of HA-MOF is confirmed by SEM studies. The PM SEM image does not show this porous aspect, but the CKP SEM image shows some porosity.

[0116] The porosity of HA-MOF is also studied by physisorption and MIP.

[0117] Nitrogen adsorption and desorption (physisorption) are observed in micropores and mesopores. It has been reported in the literature that crystalline MOFs exhibit higher adsorption in the micropore range than in the mesopore range. In contrast, the HA-MOF synthesized in this study exhibits higher adsorption in the mesopore range. The amount of nitrogen adsorbed by the HA-MOF is greater than that of the CKP. This high amount of adsorbed nitrogen demonstrates a higher porosity of the HA-MOF compared to the CKP.

[0118] Furthermore, MIP studies were conducted to investigate the porosity in the macroporous portion of HA-MOF. Mercury intrusion was higher in HA-MOF than in CKP. Therefore, it can be concluded that HA-MOF has a higher porosity than CKP, exhibiting microporosity and, more significantly, mesoporosity and macroporosity.

[0119] Finally, HA-MOF has a higher pore size than MOFs reported in the literature. Raman Electroscopy

[0120] The Raman spectrum of the CPK sample showed bands characteristic of the iron phosphate crystal structure. In the HA-MOF sample, the FePO4 bands were absent. EPR Electroscopy

[0121] The EPR spectrum of the HA-MOF sample shows strong Fe signals at 77 K and Fe signals that are degraded at room temperature. This result indicates that Fe is in an amorphous configuration in HA-MOF. Overall, the current EPR and Raman data show that (i) in CKP, iron is in a highly crystalline configuration, which is consistent with XRD results. (ii) In HA-MOF, Raman confirms the presence of humic carbon units. The iron atoms are in a highly distorted configuration, most likely forming iron aggregates embedded within the HA matrix. EDX Analysis

[0122] EDX analysis was used to analyze the elemental composition and surface distribution of the products. The distribution maps show a homogeneous distribution of all elements on the HA-MOF surface. This homogeneous distribution is a typical pattern observed in other MOFs. It could reflect the participation of all elements in the formation of the HA-MOF structure. XSP Electroscopy

[0123] The chemical bond between the phosphate group and HA is characterized by XPS spectroscopy. Low-resolution spectra confirmed that all elements determined by EDX are present in the HA-MOF. This incorporation of elements from all reactants into the resulting HA-MOF confirms the formation of the The proposed HA-Fe-P complex exhibited deconvolution of the Fe and P peaks in CKP. Deconvolution of the C peak in HA-MOF revealed a C-C bond (284.69 eV), a C-O bond (285.94 eV), and a C=O bond (288.74 eV). These three bonds suggest HA incorporation into the product. Furthermore, P-O (134.14 eV and 133.16 eV) suggests phosphate group incorporation. Deconvolution of the O peak into P-O (532.64 eV), C=O (530.77 eV), and Fe-O (531.39 eV) confirms a possible interaction between phosphate and HA via a metal bridge. The Fe-O (531.39 eV) further supports this potential complex formation between HA and Fe. Conclusion

[0124] The results obtained from different analytical techniques suggest the presence of HA-MOF units made up of the following molecular order: HA-Fe-Fe-PO4-Fe-Fe-HA.

[0125] The viability of this structure was confirmed by the semi-empirical PM3 model coupled to DFT (B3LYP / 6-311+G(d,p)). The salicylic group present in various humic acid models was used as the model binding site in the study. The results showed that the electron density is distributed across all elements of the HA-MOF unit structure, reflecting the presence of a complete molecular entity. These results demonstrate that the proposed HA-MOF unit is chemically viable. Example 3:

[0126] The inventors compared the structure of the MOF compound prepared in Example 1 with a compound prepared according to the teaching of prior art document EP1612200B1 denoted "SD".

[0127] The prior art compound SD is in the form of a double salt which is formed during an acid-base neutralization reaction by acid attack of a phosphate rock, the product is soluble in water and has a neutral final pH.

[0128] The MOF compound of the invention, on the contrary, is based on a precipitation reaction of humic acid and is formed by an acid attack on the metal.

[0009] From a morphological point of view, MOF and SD can also be differentiated. SEM images of SD show a non-crystalline morphology porous (Figure 14), while the SEM images of the MOF show an amorphous and porous structure (Figure 15). The X-ray diffractogram of the SD product shows different peaks, demonstrating the difference in molecular structure (Figure 16). Example 4:

[0129] The inventors compared the structure of the MOF compound prepared in Example 1 with a compound prepared according to the teaching of prior art document 2013 / 0104612A1 noted "CSP".

[0130] In this case, as in Example 3, the formation of CSP relies on the formation of superphosphates by acid attack of a phosphate rock, either with H2SO4 or with H3PO4, leading to a neutral final pH. In the case of the MOF product of the invention, the process consists of a precipitation reaction in an acidic medium. In the CSP product, the humic acid molecule is linked to the phosphate group by a calcium bridge. Furthermore, the stoichiometric ratios of metal, humic substance, and phosphorus differ between CSP and MOF. Finally, another structural difference lies in the crystallinity of CSP, as shown in the SEM images of SCP (Figure 17) and the XRD diagram of CSP (Figure 18).

Claims

Demands

1. MOF-type organo-metallic material comprising phosphorus, nitrogen, a humic substance and at least one metal selected from iron, copper, manganese and zinc, this organo-metallic complex having a porous structure and in which a metal:phosphorus molar ratio is between 1:4 and 1:1, and a metal:humic substance mass ratio is between 1:5 and 1:

2.

2. MOF-type organo-metallic material according to claim 1, wherein the average pore width of the porous structure is between 3 nm and 10 nm.

3. A method for manufacturing an organo-metallic material comprising a step of preparing an aqueous solution comprising a water-soluble phosphorus compound, a water-soluble nitrogen compound and a water-soluble humic substance, a step of incorporating at least one water-soluble metal salt into said aqueous solution, and a step of forming a precipitate and an aqueous phase, the incorporation step being stopped when the aqueous phase has a final pH between 3.0 and 7.

0.

4. A method for manufacturing an organo-metallic material according to claim 3, wherein the preparation step and the incorporation step are carried out at atmospheric pressure and at a temperature below 100°C, preferably below 60°C, preferably still between 20°C and 30°C.

5. A method for manufacturing an organo-metallic material according to any one of claims 3 or 4, wherein the incorporation step is stopped when the aqueous phase has a final pH value between 3.5 and 5.

5.

6. A method for manufacturing an organo-metallic material according to any one of claims 3 to 5, wherein the water-soluble humic substance is a humate salt, wherein the metallic salt is ferric chloride or ferrous chloride, and wherein the water-soluble phosphorus compound is phosphoric acid.

7. A method for manufacturing an organo-metallic material according to any one of claims 3 to 6, wherein the water-soluble nitrogen compound comprises an organic nitrogen source, such as urea.

8. Method of fertilizing a plant growing on soil, said method comprising a step of applying an organo-metallic material of the MOF type according to claim 1 to the plant or to the soil.

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