Solid amorphous metal-organic aggregate for the release of metal cations

Abstract

The invention relates to a solid amorphous metal-organic aggregate for releasing metal cations, comprising: - one or more metal salts, preferably selected from Zn, Ni, Cu, Co, Fe, Cr, Ag, Pb, Ti, V, Sc, Cd, Pd, Rh, Ru, Mo, Nb, Zr, Y, Re, Os, Ir, Pt, Au, Hg, Al, Ga, In, Ce, Eu, Ca, Mg, Sr, Be, Na, K, Li, as well as mixtures of the aforementioned metals in a stable oxidation state in water, - a water-soluble polymer, in particular a polymer that provides transparent aqueous solutions and has alcohol (-OH) groups in its structure, - a boron cross-linking agent, preferably borax.

Description

[0001] SOLID METALLOORGANIC AMORPHOUS AGGREGATE FOR METAL CATION RELEASE

[0002] DESCRIPTION

[0003] FIELD OF INVENTION

[0004] The present invention relates to a novel water-resistant material comprising a cationic metal stabilized on a polymer in the presence of a boron crosslinking agent. However, when decomposing organic matter or nutrients are present, this material is able to release the metal, thereby controlling the population of living organisms such as bacteria, algae, or fungi.

[0005] STATE OF THE ART

[0006] Preventing the presence of bacteria and fungi in plant roots is important for several reasons, from the plant's own health to its economic yield. Roots are responsible for absorbing nutrients and water from the soil into the plant. Infection by bacteria or fungi can reduce their ability to perform these functions, which can negatively affect plant growth and development. Furthermore, some bacteria and fungi are pathogens that can cause plant diseases such as root rot or wilt. These diseases weaken the plant and can lead to its death if not treated properly. It is important to note that once bacteria and fungi enter plant roots, they compete for nutrients and space in the soil. This can reduce the plant's ability to obtain the resources it needs to grow.Plants have a natural defense system against pathogens, but under constant attack they can become weaker and more susceptible to other diseases or environmental factors. Therefore, keeping roots free of bacteria and fungi (and other microorganisms) is essential to ensure optimal plant health and growth. This can be achieved through good soil management practices, such as crop rotation, the use of sterile substrates, moisture and ventilation control, and the use of preventative and corrective treatments when appropriate. The chemical industry, and specifically the agrochemical industry, has dedicated significant effort to implementing methodologies that optimize crops with a moderate environmental impact. In this regard, fertilizers, herbicides, fungicides, and other derivatives have been developed and used in both intensive and extensive farming.This use has, however, had side effects resulting from the accumulation of these substances in food chains, soils, and aquifers. One of the most widely used and effective compounds is copper, in the form of its sulfate salt.

[0007] Copper(II) sulfate (CuSCU nFW) is a blue solid chemical compound used in agriculture primarily as a fungicide and bactericide. It is employed to control various plant diseases caused by fungi and bacteria. For example, it is used to control powdery mildew, a fungal disease that affects a wide range of plants, including important crops such as grapes, tomatoes, and melons. Similarly, it is used to control bacterial diseases in plants, such as bacterial wilt or fire blight in fruit trees. This compound is also useful for disinfecting soil and preventing the spread of soilborne diseases, such as Verticillium wilt, or for treating seeds and preventing diseases during germination and the early stages of plant growth.It is important to note that the use of copper sulfate in agriculture should be done with caution, as copper is a heavy metal and can accumulate in the soil if used excessively, which can negatively affect soil microbiology and the health of non-target organisms. Furthermore, excessive use of copper sulfate can have toxic effects on plants and the environment in general. Copper(II) sulfate is highly soluble in water; at 20°C, its solubility is 245 g / L. This high solubility facilitates its application as a foliar treatment or in irrigation solutions, as it dissolves readily in water and can be distributed evenly over plants or soil.The effectiveness of copper(II) cations for bacterial control has been widely reported in the literature. However, the solubility of its salts poses problems for its direct application to soils, as rain and irrigation cause this compound to be lost, reducing its effect on plants and, moreover, contaminating other systems. It is important to emphasize that the growth of microorganisms requires, among other factors, water and nutrients, particularly organic matter or decomposing organic matter. The growth rate of bacteria in pure water is practically zero compared to the rate in culture media (Laura Broth, commercial culture used for the growth of E. coli). Therefore, the development of smart materials that can release copper when conditions are optimal for bacterial growth, but that are practically inert in the presence of water, is of vital importance.In this regard, we previously developed the following system: Bacterial Population Control with Macroscopic HKUST Crystals; ACS Appl. Mater. Interfaces 2019, 11, 22. In this article, we described how HKUST (a metal-organic framework, or MOF, composed of Cu(II) cations and 1,3,5-benzene tricarboxylic acid) was able to selectively release Cu(II) cations, inhibiting bacterial growth in nutrient-rich media, but this release did not occur in water. While interesting, the preparation of this material was expensive, and obtaining macroscopic structures (crystals > 2 mm) was not straightforward. This material (HKUST MOF) is a viable but complex solution when macroscopic crystals or particles, such as millimeters, are required.It is important to emphasize that, in this type of process, the ability to prepare materials of different sizes can allow control of release rates since decomposition is primarily a surface phenomenon.

[0008] Another article related to the present invention is based on the use of copper salts at a basic pH in the presence of polyvinyl alcohol to obtain a solid containing copper oxide. However, the use of a basic pH hinders any application for controlling bacterial populations, since bacteria cannot survive in highly basic media, nor can biological tissues. As can be seen in the publication, high amounts of base (NaOH, KOH) are used, which is unfeasible in an in vivo application. In this case, it is the basic pH that causes the copper sulfate to transform into copper hydroxides, which have a sufficiently unstable structure to generate a viscous mass that, when heated, gives rise to the compounds used in the literature.

[0009] There are certain articles related to the invention that are worth highlighting: Copper-containing polyvinyl alcohol material systems: Preparation, characterization and biological activity. Journal of Physics and Chemistry of Solids, Volume 83, 2015, Pages 96-103. In this article, the authors propose the formation of a copper oxide-based material prepared by combining 1 g of polyvinyl alcohol in water, 4 g of NaOH, and millimolar amounts of copper sulfate, resulting in a green gel that is dried in an oven at 80°C. This material exhibits the X-ray diffraction bands of copper oxide. The article also demonstrates how this material, which decomposes and releases copper oxide, can be used to control bacterial growth.However, its basic nature (pH > 10) is a disadvantage for practical field applications. Furthermore, the relatively low copper content compared to PVA is also a drawback. Technically, it's important to note that copper(II) solutions are not stable at basic pH and form gel-like systems. The presence of copper atoms gives this material (and any other) bactericidal properties. Additionally, the process requires centrifugation at 6000 revolutions per minute to recover the product.

[0010] Silver nanoparticle-loaded PVA / gum acacia hydrogel: Synthesis, characterization and antibacterial study. Carbohydrate Polymers, Volume 89, Issue 3, 2012, Pages 906-913. This article reports the use of hydrogels to control bacterial populations. Hydrogels made from industrial polymers (PVA) and natural polymers (Acacia guiri) are used; however, the use of silver nanoparticles (Ag°) is responsible for this biological activity. According to this work, Ag cations (in the form of silver nitrate) are simply introduced and reduced with light to form Ag°. The result is not a solid material but a hydrogel. Obviously, the biocidal activity of silver is superior to that of copper, but so is its price (several orders of magnitude higher), making practical application in the field unlikely.

[0011] Synthesis of physically crosslinked PVA / chitosan loaded silver nanoparticle hydrogels with tunable mechanical properties and antibacterial effects. International Journal of Biological Macromolecules, Volume 149, 15 April 2020, Pages 1262-1274. According to this article, similar to the previous one, the biopolymer chitosan is used, and in this case, silver nanoparticles are used directly, resulting in high activity, but with the same economic drawbacks as the previous example. In any case, these are hydrogels loaded with silver nanoparticles (0). They do not obtain a material, but rather a hydrogel.

[0012] A novel metal-enhanced fluorescence bio-probe for insulin sensing based on polyvinyl alcohol-borax hydrogel functionalized by Ag dots. Sensors and Actuators B: Chemical Volume 251, 2017, Pages 609-616. This article focuses on the development of a hydrogel combining PVA and borax, the generic composition of hydrogels of this type. In this case, Ag nanodots are introduced, and the viability of the system for insulin sensing is explored. Different ratios of these three compounds that allow for obtaining hydrogels are studied, but hydrogel collapse is not reported since this phenomenon is not described in the literature.

[0013] Regarding possible patent references, the following documents may be found:

[0014] CN116693885A, Preparation method of self-healing oxidized rhizoma bletillae and glucomannan hydrogel material. This document focuses on the use of silver hydrogels. The collapse of this system for providing materials is not reported. Biopolymers are used as starting materials. This invention provides a new gel for the treatment of potential skin infections. The system itself adds silver nitrate solutions to the aqueous solution of the natural polymers.

[0015] CN115651336A, “copper nanoparticle coated carbon dot real-time monitoring type antibacterial hydrogel as well as method of preparation and application thereof.” This patent describes copper nanoparticles (CuNPs) coated with carbon quantum dots (CQDs). The invention discloses a real-time monitoring antibacterial hydrogel coated with these copper nanoparticles, which is composed of CuNPs, CQDs, and PVA. The CQDs are coated onto the surface of the CuNPs to obtain CuNP@CQDs, and the CuNP@CQDs are filled into the three-dimensional pores of the PVA. Composite CuNP@CQDs-PVA hydrogels were obtained. This invention is based on the bactericidal properties of copper combined with the ability of hydrogels to saturate surfaces using carbon dots with fluorescent properties as sensors. These are not materials, much less materials formed by collapse.They use carbon dots with fluorescent properties as sensors. These are not materials, much less materials formed by the collapse of hydrogel-type precursors with cationic metals.

[0016] The present invention makes it possible to obtain materials as large as a billiard ball, which can then be atomized.

[0017] Several documents refer to a product that is either a gel or a hydrogel, whereas the product of the present invention is a solid; therefore, they cannot solve the problem that the present invention solves. Among these documents are US 2023400415 A1, and the following articles:

[0018] - DEMIREL, Serkan, et al. Fabrication and electrochemical properties of flexible ZnO doped PVABorax based solid-gel electrolytes. Inorganic Chemistry Communications., 09 / 25 / 2020, Vol. 122, ISSN 1387-7003,<DOI: 10.1016 / j.inoche.2020.108268> ,

[0019] - DEMIREL, Serkan et al. Co-doped PVA-borax anodic supercapacitors with high capacity and self-healability features. Solid State Ionics, 04 / 17 / 2023, Vol. 396, ISSN 0167-2738,<DOI: 10.1016 / j.ssi.2O23.116230> .

[0020] DESCRIPTION OF THE INVENTION

[0021] The present invention relates to a solid metal-organic amorphous aggregate for the release of metal cations, comprising:

[0022] - a) one or more metallic salts

[0023] - b) a water-soluble polymer

[0024] - c) a boron crosslinking agent.

[0025] The amorphous aggregate may comprise more than one metallic salt as component a). In the case that the aggregate comprises more than one metallic salt, the salts may be of the same metal or of different metals.

[0026] The mass proportions of the components once the amorphous metallo-organic aggregate has been prepared and dried are:

[0027] - one or more species of metal cations between 3 and 20% by mass, preferably between 4.9 and 16%

[0028] - a water-soluble polymer: between 27 and 50% by mass, preferably between 30 and 46%

[0029] - a boron crosslinking agent: between 1.5 and 4.1% by mass, preferably between 1.6 and 3.2%.

[0030] The remaining mass, up to 100%, may be oxygen and, optionally, the amorphous metallo-organic aggregate may contain up to 20% water by mass. The presence of water may be due to the aggregate not being completely dry and / or to residual water from a precursor of the amorphous aggregate components. The mass percentages refer to the total mass of the solid amorphous aggregate.

[0031] The atomic ratio of the material of the present invention is as follows:

[0032] For every 10 boron atoms (from the boron crosslinking agent) present in the material, there are at least 115 carbon atoms and 4 metal atoms.

[0033] The metal salt is a stable salt in water (that is, it is not an oxidizer and does not form permanganate or chromate-type oxoanions, i.e., oxoanions represented by the formula M m EITHER n ' A where M represents the metal, n is the number of oxygen atoms, m is the number of metal atoms, and A is the number of negative charges).

[0034] A metallic salt can be, for example, a transition metal salt.

[0035] In the amorphous solid aggregate of the invention, the metal may be selected, for example, from the list comprising: Zn, Ni, Cu, Co, Fe, Cr, Ag, Pb, Ti, V, Se, Cd, Pd, Rh, Ru, Mo, Nb, Zr, Y, Re, Os, Ir, Pt, Au, Hg, Al, Ga, In, Ce, Eu, Ca, Mg, Sr, Be, Na, K, Li, as well as mixtures of the aforementioned metals in an oxidation state stable in water. Preferred metals are calcium, magnesium, sodium, lithium, potassium, beryllium, copper, iron, cobalt, and nickel, and preferably in the oxidation states Ca(1), Mg(1), Be(1), K(1), Li(1), Na(1), Cu(1), Fe(1), Co(1), Ni(1), Zn(1).

[0036] According to particular realizations, the metallic salts are selected from salts of Cu(ll), Fe(lll), Co(ll), Ni(ll), Zn(ll), Fe(ll), Cr(lll), Mg(II), Ca(ll), Be(ll), Na(l), Li(l), K(l).

[0037] Metallic salts can be selected from all those that generate structures that are stable in water (neutral), and can be selected, for example, from sulfates, nitrates, perchlorates, chlorates, chlorides, bromides, iodines, acetates, citrates, phosphates and carbonates, preferably sulfates or nitrates.

[0038] Salts can exist in different degrees of hydration; for example, copper sulfate can be di-, tetra-, or trihydrated. Similarly, other metals form salts that can also exist in various degrees of hydration. According to preferred embodiments, the metal is selected from Zn, Ni, Cu, Co, Fe, Cr, Ag, Pb, and mixtures thereof, in an oxidation state stable in water, and the salts are selected from sulfates, nitrates, perchlorates, chlorates, chlorides, bromides, iodines, acetates, citrates, phosphates, and carbonates.

[0039] Examples of preferred salts are, for example, copper(II) sulfates, zinc(II) sulfates, nickel(II) sulfates, cobalt(II) sulfates, silver(II) sulfates, iron(II and III) sulfates, chromium(III) sulfates, and mixtures of these sulfates.

[0040] Any polymer that provides clear aqueous solutions and has alcohol groups (-OH) in its structure can be used as a water-soluble polymer.

[0041] The term transparent has the usual meaning in physics: the property that some materials possess of allowing light to pass through without being absorbed or scattered.

[0042] These polymers are capable of interacting with the boron crosslinking agent, and can be, for example, polyvinyl alcohol (PVA) or hydrolyzed polyvinyl acetate in aqueous solution.

[0043] The water-soluble polymer can be one or more of one, and can be, for example, poly(vinyl alcohol) (PVA), hydrolyzed polyvinyl acetate in aqueous solution, naturally sourced polymers, hybrid copolymers, which can be commercial or obtained by combining polymers that are able to react with the boron crosslinking agent, or mixtures of these polymers.

[0044] Examples of polymers of natural origin include celluloses and starches.

[0045] Among the possible water-soluble polymers that can be used are polyvinyl alcohol in different sizes and degrees of hydrolysis, polyvinyl acetate in different sizes and degrees of hydrolysis, as well as naturally occurring polymers such as cellulose and starch. Similarly, mixtures of the aforementioned polymers and hybrid copolymers combining alcohols capable of reacting with the boron crosslinking agent can also be considered. In specific embodiments, the water-soluble polymer is polyvinyl alcohol.

[0046] The water-soluble polymer can have different molecular weights and different degrees of hydrolysis.

[0047] The degree of hydrolysis of the water-soluble polymer can range from 85 to 100%. Depending on specific embodiments, the degree of hydrolysis of the water-soluble polymer can range from 89 to 99%.

[0048] The molecular weight of the water-soluble polymer can vary depending on the different commercial suppliers; for example, for PVA (at 99% or 89% hydrolysis) it is usually sold as 13000 and 124000. The most common are: 13000-35000, 31000-50000 or 85000-124000.

[0049] According to preferred particular embodiments, the water-soluble polymer is selected from the list comprising PVAs with the following molecular weights and degree of hydrolysis: molecular weight between 13,000 and 35,000 and degree of hydrolysis: 98%, 31,000 to 50,000; molecular weight between 99%, 85,000 to 124,000 and degree of hydrolysis: 99%; molecular weight between 31,000 and 50,000 and degree of hydrolysis: 89%; molecular weight between 85,000 and 124,000 and degree of hydrolysis: 89%. In particular, the preferred one is the one with a molecular weight between 13,000 and 35,000 and a degree of hydrolysis: 98%.

[0050] The boron crosslinking agent can be one or more boron compounds, such as borax (sodium tetraorthoborate) in various degrees of hydration, for example, Na₂E₂O₃-IOH₂O, Na₂BiOrSH₂O, Na₂B₄O₃(OH)₄·8H₂O, boric acid (B(OH)₃), boron tetrahydroxide, and sodium tetrafluoroborate. Similarly, molecules containing two boron atoms, such as pinacol borane, tetrahydroxydiborane (also called hypoboric acid: (HO)₂B-B(OH)₂), or 1,4-benzenediboronic acid, are also acceptable. The crosslinking agent can also be a combination of the aforementioned compounds in varying proportions.

[0051] In specific embodiments, the boron crosslinking agent is selected from either borax or boric acid. An even more preferred embodiment is borax in tetrahydrate salt form (Na₂B₂O₆·OHaO). Alternatively, combinations described in the literature, such as borates, tetraorthoborates, and tetrafluoroborates of copper, zinc, cobalt, nickel, and iron, may be used.

[0052] The material for the release of metallic cations is obtained when a salt of a metal is introduced into a hydrogel-type system (either in solid form, or in the very process of forming a hydrogel-type precursor that collapses and gives rise to a solid that expels the solvent from the medium and contains all the remaining components of said precursor).

[0053] A hydrogel is defined as a three-dimensional, water-insoluble network of flexible polymer chains capable of holding a large amount of water. The present invention combines the constituents of a hydrogel but eliminates most of the water, providing a solid, amorphous, metallo-organic aggregate.

[0054] The invention also relates to a process for obtaining the solid metal-organic amorphous aggregate defined above, comprising:

[0055] -1) combine under agitation

[0056] - a. one or more metal salts

[0057] - b. a water-soluble polymer

[0058] - c. a boron crosslinking agent where at least the water-soluble polymer and the boron crosslinking agent are previously in an aqueous solution, which is selected from the same aqueous solution and two different aqueous solutions, obtaining a precursor of the amorphous solid aggregate in water

[0059] -2) maintain the precursor of the amorphous solid aggregate in water in the absence of agitation until the spontaneous collapse of said precursor of the amorphous solid aggregate occurs, obtaining the amorphous solid aggregate.

[0060] The precursor of the solid metal-organic aggregate obtained in step 1) is a hydrogel-type precursor, which means that it does not retain water inside as is the case with hydrogels, but rather expels it over time.

[0061] In step 1), agitation can be manual, mechanical, or ultrasonic. In step 1), the water-soluble polymer and the boron crosslinking agent are already in an aqueous solution, which is selected from either the same aqueous solution or two different aqueous solutions. These possible combinations, in the presence of a metal salt, induce the formation of a rubbery solid that expels water when pressed and can be easily manipulated. At the same time, an aqueous phase (in which the resulting material does not dissolve) remains in the same container and can be separated, for example, by filtration or decantation. The resulting metallo-organic amorphous material can then be manually removed.

[0062] The expression “spontaneous collapse” means that once the combination of aqueous solutions has been carried out, no further action is required or performed, but rather it is waited, in the absence of agitation, for the system to collapse on its own, this process being the one that requires prolonged times, which can last for days.

[0063] Step 1) can be carried out in a temperature range in which the water is in a liquid state, for example, at atmospheric pressure between 5 and 98 °C, preferably between 10 and 50 °C, and more preferably at 25 °C.

[0064] In step 1), any of the solutions can be optionally heated to help dissolve the solute. Heating can be done, for example, between 30°C and 99°C.

[0065] According to additional specific embodiments, step 1) of the process comprises preparing, under heating at a temperature between 50°C and 100°C, an aqueous solution of the water-soluble polymer together with the metallic salt(s), and adding the aqueous solution of the crosslinking agent at the same temperature under stirring. This variation is preferred when using long-chain polymers (>50,000) to provide homogeneous mixtures, i.e., when more viscous solutions are obtained and the mixing process needs improvement.

[0066] According to additional particular embodiments, step 1) comprises combining under stirring three aqueous solutions which are: a. an aqueous solution of one or more metal salts b. an aqueous solution of a water-soluble polymer and c. an aqueous solution of a boron crosslinking agent.

[0067] According to additional particular embodiments, step 1) of the procedure comprises combining under stirring two aqueous solutions which are: a. an aqueous solution of one or more metallic salts and a water-soluble polymer, with b. an aqueous solution of a boron crosslinking agent.

[0068] According to additional particular embodiments, step 1) comprises combining under stirring two aqueous solutions which are: a. an aqueous solution of one or more metallic salts with a boron crosslinking agent, with b. an aqueous solution of a water-soluble polymer.

[0069] According to additional particular embodiments, step 1) comprises combining under agitation two aqueous solutions which are:

[0070] - an aqueous solution of the water-soluble polymer and the boron crosslinking agent with

[0071] - an aqueous solution of one or more metallic salts.

[0072] According to additional particular embodiments, step 1) comprises combining under agitation:

[0073] - an aqueous solution of the water-soluble polymer and the boron crosslinking agent with

[0074] - one or more metallic salts.

[0075] According to preferred embodiments, step 1) comprises combining under agitation:

[0076] - a. an aqueous solution of a copper salt

[0077] - b. an aqueous solution of polyvinyl alcohol and

[0078] - c. an aqueous solution of borax obtaining the precursor of the solid metal-organic aggregate.

[0079] After step 2), once the spontaneous collapse of the precursor has occurred, the resulting solid metal-organic aggregate is separated. Optionally, the resulting solid metal-organic aggregate can be subjected to a drying process.

[0080] The solid metal-organic aggregate can be crushed and converted into smaller particles by mechanical methods such as mortar or ball milling.

[0081] The optimal conditions for preparing the metal-organic aggregate efficiently and generating the least amount of waste are determined by the solubility of the different constituents of the material in water at neutral pH.

[0082] According to a specific embodiment, when using borax, a 0.1 M aqueous solution allows for easy and stable preparation of this reagent. Similarly, PVA can be dissolved at 10% or up to 20% in water; however, the 10% solution has a lower viscosity and is therefore easier to handle. The material formation process is inefficient at lower concentrations: 20 mL of borax (0.1 M) + 20 mL of PVA (10%) plus CuSCU (between 0.3 and 2.8 grams) yields the material. If this is diluted by an order of magnitude (from 40 mL total volume to 400 mL), undefined viscous systems are obtained. Considering that water is a byproduct in aggregate formation, the less water generated, the less waste is produced; therefore, the indicated concentrations are optimal. In all cases, the final material obtained is insoluble in water.This amorphous aggregate has a plastic shape and a color derived from the metal used. In this case, green for copper, white for zinc, light green for nickel, and pink for cobalt.

[0083] When water contains compounds that can be used for bacterial food, the material begins to release the metal (in cationic form) that has been stabilized within it (Figure 5).

[0084] The present invention also relates to the material obtained through the described process. The mechanism by which the material of the invention is obtained is not described in the literature and is defined herein as “collapse of the hydrogel-type material” or “collapse of the hydrogel-type precursor.” The expression “collapse of the hydrogel-type precursor” means that when the three starting materials (step 1) are in the same liquid phase, a precipitate forms that expels solvent molecules, which in this case is water, from its structure.

[0085] Figure 2 shows the change in the system when a quantity exceeding 0.5 grams of copper sulfate salt is added to 20 mL of a 10% PVA solution in water, combined with 20 mL of a 0.1 M borax solution. At this point, two phases are clearly visible: an almost transparent aqueous phase and a greenish, gummy solid that expels water. This phenomenon is described as the collapse of the hydrogel precursor, since the polymer and boron crosslinking agent now form a solid that has expelled the water due to the presence of the metal. Below 0.5 grams, the resulting material lacks a consistency that allows for manipulation and remains viscous. Similar materials can be obtained in the range of 0.5 to 2.5 grams (of copper sulfate salt). Above these amounts, a viscous system is again obtained that is impossible to manipulate.

[0086] The amorphous metallo-organic aggregates of the present invention are obtained by combining the components mentioned above:

[0087] - one or more metallic salts

[0088] - a water-soluble polymer

[0089] - a boron crosslinking agent, in the proportions indicated:

[0090] The ratio of water-soluble polymer to metallic salt by weight may be between 5.5:1 and 0.2:1, preferably between 5:1 and 0.4:1

[0091] - The ratio of water-soluble polymer and crosslinking agent by weight may be between 11:1 to 2.5:1, preferably between 10:1 to 3.3:1.

[0092] The ratio of water to the weight of the metal salt is between 70 mL and 1.1 L of water per gram of salt, preferably between 80 mL and 1 L of water per gram of salt. As for the concentrations of the starting materials for the preparation of the amorphous metal-organic aggregate, these can be:

[0093] - The aqueous solution of boron crosslinker can have a concentration between 0.05 and 2 M, preferably between 0.07 and 1.5 M

[0094] - The aqueous solution of water-soluble polymer can be prepared with an amount of polymer between 1% and up to 25% by weight, relative to the total weight of this solution, preferably between 10% and 20% by weight,

[0095] - The aqueous solution of metallic salt can have a concentration between 70 mL and 1.1 L of water per gram of salt, preferably between 80 mL and 1 L of water per gram of salt.

[0096] For every 2 grams of polymer, between 0.4 grams and 5 grams of salt (or combination of metallic salts) and at least between 0.2 and 0.6 grams of boron crosslinking agent in a total volume of water between 1 L of water per gram of salt to 80 mL of water per gram of salt, preferably using 100 mL to 8 mL of water per gram of salt.

[0097] In the specific case of using borax, the use of 0.1 M solutions is recommended since the solubility of this compound at 25°C is less than 40 grams / liter. For other crosslinking agents, the proportion must be adjusted to their content, considering borax as a source of 4 boron atoms, that is, at least 0.15 millimoles of (for example) boric acid, sodium tetrafluoroborate, or 1,4-benzenediboronic acid.

[0098] Similarly, the material of the present invention can be prepared by combining aqueous solutions of polymers and metallic salts in the proportions mentioned above (2 grams of polymer, between 0.4 and 5 grams of metallic salt in 20 milliliters of water) in the presence of an excess of 0.1 M crosslinking agent solution (40 milliliters, 20 of excess). This allows obtaining the amorphous aggregate but generates more waste.

[0099] The present invention also relates to the use of the described materials for the control of living organism systems, such as bacteria and fungi. According to particular embodiments, the process further comprises calcining the resulting amorphous solid metal-organic aggregate in the absence of oxygen, obtaining a material M@C, where C is carbon and M is the metal or metals in their neutral elemental state.

[0100] The present invention also relates to an M@C material, where C is carbon and M is the metal or metals in a neutral elemental state, obtained according to the procedure of the present invention.

[0101] BRIEF DESCRIPTION OF THE FIGURES

[0102] Figure 1: Examples of combinations that do not provide amorphous metallo-organic aggregates obtained by combining PVA / Borax with increasing amounts of copper sulfate (5, 10, 50, 100 and 250 mg from left to right).

[0103] Figure 2: Transition to the material of the invention (collapsed hydrogel-type precursor) of PVA / Borax. Copper sulfate used: 100, 175, 250, 300, 400 and 500 mg from left to right.

[0104] Figure 3: Comparison between the copper obtained within the collapsed systems and the copper used in the preparation.

[0105] Figure 4: Solid amorphous metal-organic aggregates releasing metal cations derived from cobalt (II) nickel (II) and zinc (II).

[0106] Figure 5: Release studies of different materials (DA1, DB1 and DC1) in water or in bacterial culture solutions (LB) as well as control mixture.

[0107] Figure 6: Graphs of the results of the bacterial proliferation study in the presence of the materials of the invention. After 4 hours, black bars; after 24 hours, striped bars.

[0108] Figure 7: Powder X-ray diffraction pattern for an example of pyrolyzed nickel aggregate in a nitrogen atmosphere at 700°C.

[0109] EXAMPLES

[0110] Materials and equipment

[0111] Polyvinyl alcohol, borax, and metal salts were purchased from Sigma-Aldrich. Millq water was used to prepare all solutions. Microscopic images were taken using a LEICA M165 FC stereomicroscope. XRD powder spectra were obtained using a BRUKER AXS D5005 powder diffractometer (Cu radiation, 40 kV, 30 mA, 0.05 steps, 6 s). Elemental analyses were performed using a CE Instruments CHNS1100 elemental analyzer. Inductively coupled plasma mass spectrometry (ICP) analyses were performed using an inductively coupled plasma mass spectrometer with an Agilent 7900 mass detector. IR spectra were recorded using an FT-IR ATR. 0.1 M borax solutions were used for all reactions.

[0112] Example 1

[0113] Preparation of materials

[0114] The preparation of amorphous aggregate vapors from PVA, borax, and copper sulfate pentahydrate is described using the strategy of pre-dissolving the copper sulfate in the PVA solution.

[0115] Several PVA solutions with different molecular weights were prepared (Table 1), at 10%: 50 grams of PVA were dissolved in 500 mL of distilled water. The mixture was heated to 90°C with stirring until the PVA dissolved. The mixture was then cooled to 25°C and stored in a sealed flask. The PVA selected for these solutions is indicated in Table 1.

[0116] TABLE 1: Polymer Types.

[0117] At 25°C, copper sulfate pentahydrate (see Table 1 for copper quantities) was dissolved in 20 mL of 10% PVA solution, yielding a deep blue solution. This solution was rapidly added to 20 mL of borax solution in a flask and stirred with a spatula for 10 seconds, at which point a solid appeared. The remaining liquid (water) was colorless or slightly blue, depending on the initial amount of copper. The resulting material was removed from the water and air-dried using filter paper. It was then mechanically pressed, observing the release of water. This material could then be cut into small pieces and dried for 2 hours (the material obtained does not need to be dried before use). The material was then mechanically ground in a porcelain mortar. The resulting powder was dried at 85°C under vacuum for 12 hours. After this, the material was stored at room temperature.To prepare extra-small, homogeneous particles, a final grinding process was carried out using balls. The different masses were then dried without cutting, yielding large, stone-like materials between 2 and 5 cm in diameter. The dried samples were analyzed by ICP and elemental analysis, obtaining the results shown below (Table 2).

[0118] TABLE 2: Results of the different materials: a) Under these reaction conditions, neither a hydrogel nor a patented material is obtained, but rather a pasty mixture that cannot be handled. Entries 1 to 6 of Table 2 correspond to materials prepared with PVA1 (Code: A, 13000-35000, 99%). Entries 7 and 8 of Table 2 correspond to materials obtained with the PVAs coded as B and C (31000-50000 and 85000-124000 at 99%). Entries 9 and 10 of Table 2 correspond to materials prepared with the polymers coded B* and C* (31000-50000 and 85000-124000), whose degree of hydrolysis is 89%. In all cases, the amorphous metallo-organic aggregate was obtained.

[0119] Table 2

[0120] Figure 1 shows stable PVA / Borax hydrogels with increasing amounts of copper sulfate, prepared as described (5, 10, 50, 100 and 250 mg from left to right).

[0121] Figure 2 shows the transition from hydrogel to collapsed PVA / Borax material. The amounts of copper sulfate used were: 100, 175, 250, 300, 400, and 500 mg from left to right.

[0122] As a general rule, 20 mL of PVA solution (10% in water) are vigorously mixed with 20 mL of a 0.1M borax solution in water, as shown in Figure 1. Adding 5, 10, 50, 100, or 250 milligrams of copper sulfate (prior to mixing with either the PVA or borax solution) results in the formation of green hydrogels. When the concentration of copper sulfate exceeds half a gram per 20 mL of 10% polyvinyl alcohol, a solid is obtained, as shown in Figure 3. Samples obtained with less than half a gram of copper sulfate, despite the presence of this solid, appear to be a much more complex and difficult combination to handle due to their high viscosity (Figure 2).

[0123] Under the described conditions, when copper sulfate quantities between 500 mg and 2000 mg are used, a rubbery material is obtained from the collapse of the hydrogel precursor. This precursor generally contains all the reagents, and water is expelled as a byproduct. At these concentrations, the system expels water, resulting in a spongy / rubbery-like material that releases water under pressure. Above 2.5 grams of copper sulfate, structures are obtained that are not entirely stable and begin to exhibit a complex viscosity, making them extremely difficult to handle. Furthermore, unlike any of the other compounds obtained, they generate highly colored wastewater.Studying the composition of the materials obtained after drying (Figure 3) and activation, it can be verified that the maximum achievable copper content is approximately 140 milligrams of copper per gram of amorphous solid metal-organic aggregate, as measured by ICP. This value is stable from 1.5 grams up to 2 grams. None of the materials obtained exhibit bands in powder X-ray diffraction, indicating that they are not CuO or copper nanoparticles, but rather a mixture of PVA with Cu(II) cations and boron atoms. The boron, copper, and carbon in the PVA are all detected by ICP and elemental analysis.

[0124] Whether dried or not, all copper materials are extremely stable when immersed in water. No copper release is observed even when measurements are taken for weeks. In the case of dried materials, they absorb a certain amount of water from the medium but do not release copper.

[0125] This observed phenomenon is not exclusive to copper. Similar materials have been prepared using other metallic sources such as nickel, zinc, and cobalt (Table 3). Of course, all these metals must exhibit neutral cations in aqueous solutions. Figure 6 shows the materials derived from cobalt, nickel, and zinc after drying.

[0126] At 25°C, the appropriate salt (see Table 2 for type and quantities) was dissolved in 20 mL of 10% PVA solution. This solution was quickly added to 20 mL of borax solution in a flask and stirred with a spatula for 10 seconds, at which point a solid appeared. The resulting material was removed from the water and air-dried using filter paper and mechanically pressed, observing the release of water. This material was then cut into small pieces and dried for 2 hours, after which it was mechanically ground in a porcelain mortar. The resulting powder was dried at 85°C under vacuum for 12 hours. Afterward, the material was stored at room temperature. To obtain extra-small and homogeneous particles, a final grinding with ball mills was performed. The dried samples were analyzed by ICP and elemental analysis, yielding the results shown below (Table 3).

[0127] Table 3: Materials with other metals.

[0128] EXAMPLE 2

[0129] USE OF MATERIALS

[0130] Selective release in biological media:

[0131] Whether dried or not, all copper materials are extremely stable when immersed in water. No copper release is observed even when measurements are taken for weeks. In the case of dried materials, they absorb a certain amount of water from the medium but do not release copper. When these materials are immersed in media optimal for the growth of bacteria or other living organisms, copper release is almost immediate, as can be seen in the following examples. Biological culture medium (LB) was selected as a proof of concept where different samples were compared in water. It can be clearly observed that in water after 24 hours...For this experiment, ten milligrams of each of the prepared materials (identified in Table 2 as DA1, DB1, and DC1) were introduced into a constant volume of liquid, and the changes produced after 24 hours were measured using ultraviolet-visible light (650 nanometers, band associated with copper(II) in solution). As can be seen in Figure 5, none of the materials produced a signal after 24 hours when immersed in water. However, when a solution of LB in water was used instead of pure water, the release was very intense. Control systems were used in which copper sulfate and polyvinyl alcohol had been allowed to dry without borax. It can be observed that in water, this material decomposes after 24 hours, generating a small signal. Release was also observed in the culture medium (LB) (Figure 5).

[0132] Bacterial culture:

[0133] In this work, we considered E. coli as a model bacterium, using the Dh5a strain. The characteristics of this strain are: relaxed phenotype, non-utilization of lactose, recombination deficiency, and endonuclease A deficiency. Three different colonies were taken from the plates and cultured overnight at 37 °C with shaking (200 rpm) in 2 mL LB (in 13 mL capacity tubes).

[0134] Contact of bacterial cultures with materials

[0135] A preculture of E. coli was prepared, diluted 1:100, and cultured for 4 h at 37°C with shaking (200 rpm), ensuring that the resulting culture reached the exponential phase. The culture was then diluted 1:50 (unless otherwise specified), and several samples were prepared in 2 mL of LB. In each sample (in triplicate), 1, 7, or 15 mg of selected materials were introduced. These cultures were grown for 4 h under the same conditions, and then 200 pL were collected for absorbance measurements. At each sampling time, 200 pL were collected (without touching the material) for an absorbance measurement (500 nm) using a fluorometer (Varioskan LUX, Thermo). A 96-well plate (black, transparent background; Corning) was used. (Tables 4 and 5)

[0136] The following table presents the absorption values ​​of the tests. The higher the value, the greater the concentration of bacteria and therefore the lower the bactericidal effect of the material. As can be seen, the control inoculated with bacteria (LB Control, entry 2) reaches values ​​close to 0.4 after 4 hours, while in the presence of the metallo-organic aggregates of the invention, the value is lower. Particularly significant are the results at 24 hours (Table 5), where the control value of 1.2 and the materials (using more than 7 mg of amorphous aggregate of the invention) provide complete control. Table 4: Bacterial control tests at 4 hours Table 5: 24h Bacterial Control Trials

[0137] Figure 6 shows the results of the bacterial proliferation study in the presence of the materials of the invention. After 4 hours, the bars are black (I), and after 24 hours, they are striped. Bacterial density was measured using optical density (OD), with a value between 1 and 1.2 being observable for a naturally grown colony. As can be seen for the control culture, after four hours the optical density is close to 0.4, and after 24 hours, the density exceeds 1. The different materials introduced (DA1, DB1, and DC1, Table 2) are based on different degrees of polymerization of the PVA used (13,000–35,000 for DA1, 31,000–50,000 for DB1, and 85,000–124,000 for DC1). In general, regarding the materials used, it can be noted that with one milligram of material, no population control can be observed.With seven milligrams, after 24 hours there is practically a 50% attenuation, and when 15 milligrams are used, all materials show virtually total control of the indicated system, preventing bacterial proliferation with just 15 mg of these materials. Control tests were performed for this medium using pure polyvinyl alcohol, which does not show any bacterial control; pure copper sulfate, which is completely soluble and shows total control; borax, which shows almost no bacterial control; and a combination of a generated material (this material is a control, prepared by evaporating PVA with copper sulfate; it is not a collapsed precursor, it is water-soluble, as seen in Figure 5, and is used as a control) after drying copper sulfate solution with polyvinyl alcohol solution.This boron-free control material provides complete bacterial control but dissolves completely even in pure water, as previously mentioned (Figure 5). The combination of its high insolubility in water (or its relatively surprising stability in water) with its ability to break down when the water contains nitrogen sources (nitrogenous organic compounds, ammonia)—nutrients in general for bacterial populations—makes these materials potent agents, important in agrochemicals. A simple combination of the polymer with copper results in a plastic material that can be used but dissolves in water. In contrast, the amorphous aggregates obtained from the collapse of a borax and polymer hydrogel will only begin to release copper when the medium contains nutrients.Consequently, these materials only release copper when it is really necessary, since there is no need to control bacterial populations because these are also controlled by the absence of nutrients to grow.

[0138] EXAMPLE 3: Pyrolysis and use as catalysts

[0139] To obtain supported metal catalysts, different amorphous aggregates were prepared using copper, cobalt, and nickel metal salts. Specifically, sulfates of these metals were used. Nine amorphous aggregates were prepared, representing all possible combinations of these three metals: copper, cobalt, and nickel; copper with cobalt; copper with nickel; nickel with cobalt; and finally, nickel, copper, and cobalt. In all samples, an equimolecular amount of metal atoms was used to obtain the materials, calculated at 0.5 grams of copper sulfate pentahydrate (0.002 moles).

[0140] Once the materials were obtained by combining the metal and PVA solutions with the boron crosslinking agent solution (in this case, borax) using the procedure described above, the materials were dried (24 h at 80 °C under vacuum) and ground in a ball mill. The resulting fine powder was pyrolyzed in a nitrogen atmosphere at a ramp rate of 30 degrees per minute until reaching 700 degrees, and then pyrolyzed for 3 hours at 700 degrees. A black powder with the following composition was obtained:

[0141] The pyrolysis process allows the obtaining of metallic particles in an oxidized state as can be observed in figure 7

[0142] General procedure for the synthesis of anilines

[0143] In an 8 mL vial, 0.5 mmol of the starting reagent (nitrobenzene from the formula) and is dissolved in 1.4 mL of solvent (heptane in the scheme above). To the above solution, 1,3,5-trimethoxybenzene (84.0 mg, 0.5 mmol, 1 eq) is added, which will be the compound used as an internal standard, and the catalyst (Ni@C, 8 mol% or 30.74 mg, 4 mol%). Next, the vials are placed on the autoclave carousel and sealed so that the hydrogen from the bullet can be injected.

[0144] Once the autoclave is sealed, it is purged with 3 x 20 bar of H2 and the pressure is set to 50 bar. Finally, the autoclave is placed on a heating plate for 20 hours at 140 °C with stirring.

[0145] After this time, the autoclave is depressurized and the vials are removed from the carousel. Each reaction is transferred to an Eppendorf tube, and the vial is thoroughly washed with dichloromethane before centrifugation. Once this process is complete, the supernatant is extracted and transferred to a round-bottom flask for vacuum concentration. Finally, in cases where some catalyst particles have passed into the solution, PTFE filters are used to remove any remaining residue. Phenylamine (aniline)

[0146] Yellowish liquid, 87%. X H NMR (300 MHz, CDCI3) 8: 7.31 - 7.24 (m, 2H), 6.88 (tt, J = 7.3, 1.2 Hz, 1H), 6.79 - 6.74 (m, 2H), 3.67 (bs, 2H, NH2).

[0147] 13 C NMR (75 MHz, CDCI3) 8: 146.4 (C), 129.2 (CH), 118.4 (CH), 115.1 (CH).

[0148] 2 a-amino-1 -methylbenzene (b-toluidine) Clear liquid, 90%. 1 H NMR (300 MHz, COC / 3) 8: 7.07 (t, J = 7.3 Hz, 2H), 6.78 - 6.67 (m, 2H), 3.56 (s, 2H), 2.19 (s, 3H).13 C NMR (75 MHz, I). JH 2 CDCI3) 8: 144.58, 130.49, 127.00, 122.37, 118.68, 114.98, 114.54, 77.53.

[0149] 77.11 , 76.68 ,

[0150] 1 ,2-diaminobenzene (o-phenylenediamine)

[0151] Solid orange, 73%. 1 H NMR (300 MHz, CDC / 3) 8:6.72(s,1H), 3.16(s,1H). 13 C NMR (75 MHz, CDCI3) 6: 134.84, 120.43, 116.90, 77.58. 77.36, 77.16,

[0152] 1 ,3-diaminobenzene (m-phenylenediamine)

[0153] Solid orange, 80%. 1 H NMR (300 MHz, CDC / 3) 8: 6.94 (t, 3 = 7.9 Hz, 1 H), 6.12 (dd, 3 = 7.9, 2.2 Hz, 2H), 6.03 (t, 3 = 2.2 Hz, 1 H), 3.44 (s, 4H). 1 3 C NMR (75 MHz, CDCh) 8:147.61; 76.74.

Claims

CLAIMS 1. A solid metal-organic amorphous aggregate for releasing metal cations, comprising: - one or more metallic salts - a water-soluble polymer - a boron crosslinking agent.

2. A solid metallo-organic amorphous aggregate according to claim 1, comprising: - one or more salts of a metal: between 3 and 20% by mass, preferably between 4.9 and 16% - a water-soluble polymer: between 27 and 50% by mass, preferably between 30 and 46% - a boron crosslinking agent: between 1.5 and 4.1% by mass, preferably between 1.6 and 3.2%.

3. A solid metal-organic amorphous aggregate according to claim 1 or 2, wherein the metal is a non-oxidizing metal and does not form oxoanions represented by the formula M m EITHER n ' Awhere M represents the metal, n is the number of oxygen atoms, m is the number of metal atoms, and A is the number of negative charges.

4. A solid metallo-organic amorphous aggregate according to claim 1 or 2, wherein the metal is selected from: Zn, Ni, Cu, Co, Fe, Cr, Ag, Pb, Ti, V, Se, Cd, Pd, Rh, Ru, Mo, Nb, Zr, Y, Re, Os, Ir, Pt, Au, Hg, Al, Ga, In, Ce, Eu, Ca, Mg, Sr, Be, Na, K, L, as well as mixtures of the above-mentioned metals in an oxidation state stable in water.

5. A solid metal-organic amorphous aggregate according to claim 1 or 2, wherein the metal salt is selected from salts of Cu(ll), Fe(lll), Co(ll), Ni(ll), Zn(ll), Fe(ll), Cr(lll), Mg(II), Ca(ll), Be(ll), Na(l), Li(l) and / or K(l).

6. A solid metal-organic amorphous aggregate according to claim 1 or 2, wherein the metal salt is selected from sulfates, nitrates, perchlorates, chlorates, chlorides, bromides, iodides, acetates, citrates, phosphates and carbonates, preferably sulfates or nitrates.

7. A solid metallo-organic amorphous aggregate according to claim 1 or 2, wherein the metal is selected from Zn, Ni, Cu, Co, Fe, Cr, Ag, Pb and mixtures thereof, in an oxidation state stable in water and the salts are selected from sulfates, nitrates, perchlorates, chlorates, chlorides, bromides, iodides, acetates, citrates, phosphates and carbonates.

8. A solid metal-organic amorphous aggregate according to claim 1 or 2, wherein the metal salt is selected from copper(II), zinc(II), nickel(II), cobalt(II), silver(II), iron(II and III), chromium(III) sulfates and mixtures of these sulfates.

9. A solid metallo-organic amorphous aggregate according to any one of claims 1 to 8, wherein the water-soluble polymer is a polymer that provides clear aqueous solutions and has alcohol (-OH) groups in its structure.

10. A solid metallo-organic amorphous aggregate according to claim 9, wherein the water-soluble polymer is selected from poly(vinyl alcohol) (PVA), hydrolyzed polyvinyl acetate in aqueous solution, naturally sourced polymers, hybrid copolymers combining alcohols that are capable of reacting with the boron crosslinking agent.

11. A solid metallo-organic amorphous aggregate according to claim 9, wherein the water-soluble polymer is at a degree of hydrolysis between 85 and 100%.

12. A solid metallo-organic amorphous aggregate according to claim 9, wherein the water-soluble polymer is 99% or 89% hydrolysis PVA, and having a molecular weight between 13000 and 124000.

13. A solid metal-organic amorphous aggregate according to any one of claims 1 to 12, wherein the boron crosslinking agent is selected from borax, boric acid, boron tetrahydroxide, and sodium tetrafluoroborate, molecules containing two boron atoms.

14. A solid metallo-organic amorphous aggregate according to claim 13, wherein the boron crosslinking agent is selected from pinacol borane, tetrahydroxydiborane and 1,4-benzenediboronic acid.

15. A process for obtaining the solid metal-organic amorphous aggregate defined in any one of claims 1 to 14, comprising: -1) combine: - a. one or more metallic salts that provide stable cations in water. - b. a water-soluble polymer and - c. a boron crosslinking agent where at least the water-soluble polymer and the boron crosslinking agent are previously in an aqueous solution, selected from the same aqueous solution or two different aqueous solutions, obtaining a precursor of the amorphous solid aggregate, -2) maintain, in the absence of agitation, the precursor of the amorphous solid aggregate in water until the spontaneous collapse of said precursor of the amorphous solid aggregate occurs, obtaining the amorphous solid aggregate.

16. A process according to claim 15, wherein step 1) comprises combining under stirring three aqueous solutions which are: a. an aqueous solution of one or more metallic salts, b. an aqueous solution of a water-soluble polymer, and c. an aqueous solution of a boron crosslinking agent.

17. Process according to claim 15, wherein step 1) comprises combining under stirring two aqueous solutions which are: a. an aqueous solution of one or more metal salts and a water-soluble polymer, with b. an aqueous solution of a boron crosslinking agent.

18. A process according to claim 15, wherein step 1) comprises combining under stirring two aqueous solutions which are: a. an aqueous solution of one or more metallic salts with a boron crosslinking agent, with b. an aqueous solution of a water-soluble polymer.

19. A process according to claim 15, wherein step 1) comprises combining under agitation two aqueous solutions which are: - an aqueous solution of the water-soluble polymer and the boron crosslinking agent with - an aqueous solution of one or more metallic salts.

20. Process according to claim 15, wherein step 1) comprises combining under agitation: - an aqueous solution of the water-soluble polymer and the boron crosslinking agent with - one or more metallic salts.

21. A process according to claim 15, wherein starting materials are used in the following proportions: - ratio of water-soluble polymer to metallic salt by weight between 5.5:1 and 0.2:1, - ratio of water-soluble polymer and crosslinking agent by weight between 11:1 and 2.5:

1. - proportion of water to the weight of the metallic salt between 70 mL and 1.1 L of water for each gram of salt.

22. A process according to claim 15, wherein starting materials are used in the following concentrations: - aqueous solution of boron crosslinker at a concentration between 0.05 and 2 M, - aqueous solution of water-soluble polymer with a polymer content between 1% and up to 25% by weight, relative to the total weight of this solution - aqueous solution of metallic salt at a concentration between 70 mL and 1.1 L of water per gram of salt.

23. Method according to claim 15, comprising applying mechanical pressure after step 2) to expel the water as waste. 24 Process according to any one of claims 15 to 22, further comprising calcining the obtained amorphous solid metal-organic aggregate in the absence of oxygen, obtaining a material M@C, where C is carbon and M is the metal or metals in a neutral elemental state.

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