EP2027307B1 - Process for preparing porous metal organic frameworks - Google Patents

Abstract

The present invention relates to a process for preparing a porous metal organic framework comprising at least two organic compounds coordinated to at least one metal ion, which comprises the steps (a) oxidation of at least one anode comprising the metal corresponding to at least one metal ion in a reaction medium in the presence of at least one first organic compound which is an optionally substituted monocyclic, bicyclic or polycyclic saturated or unsaturated hydrocarbon in which at least two ring carbons have been replaced by heteroatoms selected from the group consisting of N, O and S to form a reaction intermediate comprising the at least one metal ion and the first organic compound; and (b) reaction of the reaction intermediate at a prescribed temperature with at least one second organic compound which coordinates to the at least one metal ion, with the second organic compound being derived from a dicarboxylic, tricarboxylic or tetracarboxylic acid.

Description

The present invention relates to processes for preparing a porous organometallic framework comprising at least two organic compounds coordinately bonded to at least one metal ion.

Crystalline porous metal-organic frameworks, so-called "metal-organic frameworks" (MOF) with specific pores or pore distributions and large specific surfaces have recently become the target of extensive research activities.

For example, describes the US-A 5,648,508 microporous organometallic materials prepared under mild reaction conditions from a metal ion and a ligand in the presence of a template compound.

The WO-A 02/088148 discloses the preparation of a series of compounds having the same framework topology. These so-called IRMOF (Isoreticular Metal-Organic Framework) structures represent monocrystalline and mesoporous framework materials, which have a very high storage capacity for gases.

Eddaoudi et al., Science 295 (2002), 469-472 , for example, describe the preparation of a so-called MOF-5, which is based on a zinc salt, ie zinc nitrate, wherein for the synthesis of MOF material, this salt and 1,4-benzenedicarboxylic acid (BDC) in N, N'-diethylformamide (DEF) are solved.

Chen et al., Science 291 (2001), 1021-1023 , describe, for example, the preparation of a so-called MOF-14 which starts from a copper salt (copper nitrate) and where for the synthesis of the MOF this salt and 4,4 ', 4 "-benzol-1,3,5-triyltribenzoic acid (H ₃ BTC) in N, N'-dimethylformamide (DMF) and water are dissolved.

To improve the properties of metal-organic frameworks prepared in this way have Seki et al., J. Phys. Chem. B 2002, 106, 1380-1385 reacted in a conventional manner prepared metal-organic framework materials in a heterogeneous reaction with triethylenediamine. The results presented here are intended to lead to the development of porous materials that require the need for structure control for applications such as gas storage, separation, catalysis, and molecular recognition.

Similar structures are from Kitagawa et al., Angew. Chem. Int. Ed. 43 (2004), 2334-2375 described.

An improved process for the preparation of porous organometallic frameworks having at least two coordinatively bound organic compounds is disclosed in U.S. Pat DE-A 10 2005 023 856 described. Here, in a one-step reaction, a metal ion is provided by means of electrochemical oxidation in a reaction medium which further comprises the two organic compounds. Furthermore, an alternative process is described which comprises two reaction stages. In a first step, the oxidation is to produce a metal ion in the presence of a first compound having at least two carboxylate groups and then reacting the resulting complex intermediate with a second organic compound.

Despite this improved manufacturing process using the electrochemical provision of the metal ion, there is a need for further optimized manufacturing processes.

It is therefore an object of the present invention to provide a process which provides an improved preparation of a porous organometallic framework having at least two organic compounds. In this case, in particular a most cost-effective and highly scalable method should be provided.

1. (a) Oxidation mindestens einer dem mindestens einen Metallion entsprechenden Metall enthaltenden Anode in einem Reaktionsmedium in Gegenwart zumindest einer ersten organischen Verbindung, wobei die erste organische Verbindung ein gegebenenfalls substituierter mono-, bi- oder polycyclischer gesättigter oder ungesättigter Kohlenwasserstoff ist, bei dem mindestens zwei Ring-Kohlenstoffatome durch Heteroatome ausgewählt aus der Gruppe bestehend aus N, O und S ersetzt sind, unter Ausbildung eines das mindestens eine Metallion und die erste organische Verbindung enthaltendes Reaktionszwischenprodukt; und
2. (b) Umsetzung des Reaktionszwischenproduktes bei einer vorgegebenen Temperatur mit einer mindestens zweiten organischen Verbindung, die koordinativ an das mindestens eine Metallion bindet, wobei sich die zweite organische Verbindung von einer Di-, Tri- oder Tetracarbonsäure ableitet.

The object is achieved by a process for the preparation of a porous organometallic framework material comprising at least two organic compounds coordinately bonded to at least one metal ion, comprising the steps:

1. (a) Oxidation of at least one metal containing the at least one metal ion in a reaction medium in the presence of at least one first organic compound, wherein the first organic compound is an optionally substituted mono-, bi- or polycyclic saturated or unsaturated hydrocarbon in which at least two Ring carbon atoms are replaced by heteroatoms selected from the group consisting of N, O and S to form a reaction intermediate containing the at least one metal ion and the first organic compound; and
2. (b) reacting the reaction intermediate at a given temperature with an at least second organic compound coordinating to the binds at least one metal ion, wherein the second organic compound derived from a di-, tri- or tetracarboxylic acid.

It has been found that it is advantageous, in contrast to the two-stage procedure from the DE-A 10 2005 023 856 initially not the polybasic carboxylic acid, but to add the further organic compound during the anodic oxidation of the metal to the reaction medium and only in a second step to carry out the reaction with the polybasic carboxylic acid, since the carboxylic acid essentially determines the framework structure of the porous organometallic framework.

It can thereby be achieved that the formation of the actual framework material is decoupled from the anodic oxidation and can therefore be carried out for a longer time with a simpler synthesis apparatus. In this way, in step (a), the oxidation can be limited to a minimum of reaction time, which is advantageous because of the comparatively high expenditure on equipment for the electrochemical oxidation.

The process according to the invention also makes it possible to use polybasic carboxylic acids which do not withstand the conditions of electrochemical oxidation. In addition, with the aid of the reaction intermediate, a plurality of porous organometallic frameworks can be easily represented, in which the polybasic carboxylic acid is varied in the simpler second step.

Step (a) of the process according to the invention is the anodic oxidation of the at least one metal, which enters the reaction medium as a cation and reacts with a first organic compound to form a reaction intermediate. This reaction intermediate can be separated by filtration, for example, and then further reacted with the second organic compound. However, it is preferred if the reaction intermediate is used without further workup in step (b) of the process according to the invention. Typically, this is the reaction intermediate in a suspension. The reaction intermediate may contain a salt and / or a porous organometallic framework and / or a non-porous organometallic framework. The salt may be formed by reaction of the solvent or one of its components (for example, as an alcoholate using a solvent containing at least one alcohol). It has surprisingly been found that the presence of the first organic compound contributes to a better or more controlled resolution of the anode.

Step (a) of the process according to the invention can preferably be carried out as described in WO-A 2005/049892 is described.

The term "electrochemical preparation" as used in the context of the present invention refers to a production process in which the formation of at least one reaction product in at least one process step is associated with the migration of electrical charges or the occurrence of electrical potentials.

The term "at least one metal ion" as used in the present invention refers to embodiments according to which at least one ion of a metal or at least one ion of a first metal and at least one ion of at least one second metal different from the first metal by anodic oxidation to be provided.

The present invention also encompasses embodiments in which at least one ion of at least one metal is provided by anodic oxidation and at least one ion of at least one metal via a metal salt, wherein the at least one metal in the metal salt and the at least one metal, via anodic oxidation as Metal ion can be provided, the same or different from each other. Thus, for example, the present invention encompasses an embodiment in which the reaction medium contains one or more different salts of a metal and the metal ion contained in that salt or salts is additionally provided by anodic oxidation of at least one anode containing that metal. Likewise, the present invention comprises an embodiment in which the reaction medium contains one or more different salts of at least one metal and at least one metal different from these metals is provided via anodic oxidation as the metal ion in the reaction medium.

According to a preferred embodiment of the present invention, the at least one metal ion is provided by anodic oxidation of at least one of the at least one metal-containing anode, wherein no further metal is provided via a metal salt.

Accordingly, the present invention includes an embodiment in which the at least one anode contains a single or two or more metals, wherein if the anode contains a single metal, that metal is provided by anodic oxidation, and in case the anode is two or more metals, at least one of these metals is provided by anodic oxidation.

Furthermore, the present invention comprises an embodiment according to which at least two anodes are used, wherein the two may be the same or different from each other. Each of the at least two anodes may in this case contain a single or two or more metals. In this case, it is possible, for example, for two different anodes to contain the same metals but these in different proportions. Likewise, in the case of different anodes, for example, it is possible that a first anode contains a first metal and a second anode contains a second metal, wherein the first anode does not contain the second metal and / or the second anode does not contain the first metal.

The metal or metals are elements of Groups 2 to 15 of the Periodic Table of the Elements. In the context of the present invention, preferred metal ions are selected from the group of the metals consisting of copper, iron, aluminum, zinc, magnesium, zirconium, titanium, vanadium, molybdenum, tungsten, indium, calcium, strontium, cobalt, nickel, platinum, rhodium, Ruthenium, palladium, scandium, yttrium, a lanthanide, manganese and rhenium. Further more preferred are iron, copper, zinc, nickel and cobalt. Particularly preferred is copper.

As metal ions; which are provided via anodic oxidation in the reaction medium, in particular Cu ²⁺ , Cu ⁺ , Ni ²⁺ , Ni ⁺ , Fe ³⁺ Fe ²⁺ , Co ³⁺ , Co ²⁺ , Zn ²⁺ , Mn ³⁺ , Mn ²⁺ , Al ³⁺ , Mg ²⁺ , Sc ³⁺ , Y ³⁺ , Ln ³⁺ , Re ³⁺ , V ³⁺ , In ³⁺ , Ca ²⁺ , Sr ²⁺ , Pt ²⁺ , TiO ²⁺ To mention Ti ⁴⁺ , ZrO ²⁺ , Zr ⁴⁺ , Ru ³⁺ , Ru ²⁺ , Mo ³⁺ , W ³⁺ , Rh ²⁺ , Rh ⁺ , Pd ²⁺ and Pd ⁺ . Particularly preferred are Zn ²⁺ , Cu ²⁺ , Cu ⁺ , Fe ²⁺ , Fe ³⁺ , Ni ²⁺ , Ni ⁺ , Co ³⁺ and Co ²⁺ . Particularly preferred are Cu ²⁺ and Cu ⁺ .

Accordingly, the present invention for step a) also describes a method as described above, wherein a copper and / or a nickel and / or a cobalt and / or a zinc and / or an iron-containing anode is used as metal ion source.

According to a preferred embodiment, the present invention also relates to a method as described above, wherein a copper-containing anode is used as the metal ion source.

The structure of the anode used in step a) of the process according to the invention can in principle be chosen arbitrarily, as long as it is ensured that the at least one metal ion can be provided in the reaction medium to form the reaction intermediate by αnodic oxidation.

Among others, preferred are anodes in the form of a rod and / or a ring and / or a disc such as an annular disc and / or a plate and / or a pipe and / or a bed and / or a cylinder and / or a cone and / or a truncated cone.

According to a preferred embodiment, the method according to the invention is carried out using at least one sacrificial anode in step a). The term "sacrificial anode" as used in the context of the present invention refers to an anode which at least partially dissolves in the course of the process according to the invention. In this case, embodiments are also detected in which at least a part of the dissolved anode material is replaced in the course of the process. This can be done, for example, by introducing at least one new anode into the reaction system or, according to a preferred embodiment, introducing an anode into the reaction system and continuously or discontinuously feeding it into the reaction system in the course of the process according to the invention.

In the method according to the invention, preference is given to using anodes which consist of the at least one metal serving as metal ion source or which contain at least one metal applied to at least one suitable carrier material.

The geometry of the at least one carrier material is subject to essentially no restrictions. For example, it is possible to use support materials in the form of a fabric and / or a film and / or a felt and / or a screen and / or rod and / or a candle and / or a cone and / or a truncated cone and / or a ring and / or a disc and / or a plate and / or a pipe and / or a bed and / or a cylinder.

Suitable support materials according to the invention, for example, metals such as at least one of the above metals, alloys such as steels or bronzes or brass, graphite, felt or foams into consideration.

Very particular preference is given to anodes which consist of the at least one metal which serves as source of metal ions.

The structure of the cathode used in step a) of the method according to the invention can in principle be chosen arbitrarily, as long as it is ensured that the at least one metal ion can be provided in the reaction medium by αnodic oxidation.
According to a preferred embodiment of the method according to the invention, the electrically conductive electrode material of the at least one cathode is selected such that no disturbing secondary reaction takes place in the reaction medium. As, among others Preferred cathode materials include graphite, copper, zinc, tin, manganese, silver, gold, platinum or alloys such as steels, bronzes or brass.

Among others, preferred combinations of the anode material serving as the metal ion source and the electrically conductive cathode material are: anode cathode zinc zinc copper copper magnesium copper cobalt cobalt iron stole copper stole

The geometry of the at least one cathode is subject to essentially no restrictions. For example, the use of cathodes in the form of a rod and / or a ring and / or a disc and / or a plate and / or a tube is possible.

Essentially any of the common cell types used in electrochemistry can be used in the present invention. Very particular preference is given in the process according to the invention to an electrolysis cell which is suitable for the use of sacrificial electrodes.

In principle, it is possible inter alia to use divided cells with, for example, plane-parallel electrode arrangement or candle-shaped electrodes. For example, ion exchange membranes, microporous membranes, diaphragms, filter fabrics of non-electron conducting materials, glass frits and / or porous ceramics can be used as a separation medium between the cell compartments. Preferably, ion exchange membranes, in particular cation exchange membranes, are used, of which in turn such membranes are preferably used, which consist of a copolymer of tetrafluoroethylene and a perfluorinated monomer containing sulfonic acid groups.

Within the scope of a preferred embodiment of the method according to the invention, one or more undivided cells are preferably used in step a).

Accordingly, the present invention also relates to a method as described above, wherein the method is carried out in an undivided electrolysis cell.

Very particular preference is given to combinations of geometries of anode and cathode, in which the mutually facing sides of the anode and cathode together form a gap of homogeneous thickness.

In the at least one undivided cell, for example, the electrodes are preferably arranged plane-parallel, the electrode gap having a homogeneous thickness, for example in the range from 0.5 mm to 30 mm, preferably in the range from 0.75 mm to 20 mm and particularly preferably in the range from 1 up to 10 mm.

Within the scope of a preferred embodiment, it is possible, for example, to arrange a cathode and an anode in a plane-parallel manner so that an electrode gap with a homogeneous thickness in the range of 0.5 to 30 mm, preferably in the range of 1 to 20 mm, in the resulting cell is preferably formed in the range of 5 to 15 mm and more preferably in the range of 8 to 12 mm, for example in the range of about 10 mm. This type of cell is referred to in the context of the present invention by the term "gap cell".

According to a preferred embodiment of the method according to the invention, the cell described above is used as a bipolar switched cell.

In addition to the cell described above, according to a likewise preferred embodiment, in the context of the method according to the invention, the electrodes are applied individually or in a stacked manner. In the latter case, these are so-called stack electrodes, which are preferably connected in series bipolar in the so-called plate stack cell. In particular for the practice of step a) of the process according to the invention on an industrial scale, preferably at least one pot cell and in particular preferably series-connected plate stack cells are used, the basic structure of which is disclosed in US Pat DE 195 33 773 A1 is described.

In the context of the preferred embodiment of the plate stacking cell, it is preferred, for example, to arrange disks of suitable materials, such as copper disks, in a plane-parallel manner, such that a gap with a homogeneous thickness in the range of 0.5 to 30 mm, preferably in the range of 0, is provided between the individual disks , 6 to 20 mm, more preferably in the range of 0.7 to 10 mm, more preferably in the range of 0.8 to 5 mm and in particular in the range of 0.9 to 2 mm such as formed in the range of about 1 mm. In this case, the distances between the individual panes may be the same or different, wherein according to a particularly preferred embodiment, the distances between the panes are substantially equal. According to another embodiment, the material of one slice of the plate stack cell may be different from the material of another slice of the plate stack cell. For example, a disc made of graphite, another disc made of copper, wherein the copper disc is preferably connected as the anode and the graphite disc preferably as a cathode.

Furthermore, it is preferred in the context of the present invention, for example, to use so-called "pencil sharpener" cells, as for example in J. Chaussard et al., J. Appl. Electrochem. 19 (1989) 345-348 the contents of which are incorporated by reference into the context of the present application in their entirety. In the method according to the invention, pencil sharpener electrodes with rod-shaped, trackable electrodes are particularly preferably used.

In particular, accordingly, the present invention for step a) also relates to a method as described above, wherein the method is carried out in a gap cell or plate stack cell.

Cells in which the electrode spacing is in the range of less than or equal to 1 mm are referred to as capillary gap cells.

According to likewise preferred embodiments of the method according to the invention, in step a) electrolysis cells can be used with, for example, porous electrodes made of metal fillings or with, for example, porous electrodes made of metal meshes or with, for example, electrodes both of metal fillings and metal meshes.

According to a further preferred embodiment, electrolysis cells are used in the process according to the invention, which have at least one sacrificial anode with a round disk-shaped cross section and at least one cathode with an annular cross section, wherein particularly preferably the diameter of the preferably cylindrical anode is smaller than the inner diameter of the cathode and the Anode is mounted in the cathode such that between the outer surface of the cylinder jacket of the anode and the inner surface of the cathode at least partially surrounding the anode, a gap of homogeneous thickness is formed.

In the context of the present invention, it is also possible to make the original anode to the cathode and the original cathode to the anode by reversing the polarity.

Within the scope of this process variant, it is possible, for example, to provide a metal via anodic oxidation as the metal cation by appropriate choice of electrodes containing different metals, and to provide a further metal in a second step after polarity reversal. It is also possible to accomplish the polarity reversal via the application of alternating current.

In principle, it is possible to carry out the process in batch mode or continuously or in mixed mode. Preferably, the process is carried out continuously in at least one flow cell.

The voltages used in the method according to the invention can be adapted to the respective at least one metal of the at least one anode which serves as metal ion source for the reaction intermediate and / or to the properties of the first organic compound and / or optionally to the properties of the at least one solvent and / or optionally the properties of the at least one conducting salt described below and / or the properties of the at least one cathodic depolarization compound described below.

In general, the voltages per electrode pair are in the range of 0.5 to 100 V, preferably in the range of 2 to 40 V, and more preferably in the range of 4 to 20 V. Examples of preferred ranges are about 4 to 10 V or 10 to 20 V. or 20 to 25 V or 10 to 25 V or 4 to 20 V or 4 to 25 V. In the course of the process according to the invention, the stress may be constant or change continuously or discontinuously in the course of the process.

For example, in the case where copper is anodized, the voltages are generally in the range of 3 to 20 V, preferably in the range of 3.5 to 15 V, and more preferably in the range of 4 to 15 V.

The current densities which occur in the context of the preparation according to the invention of the porous organic framework materials are generally in the range from 0.01 to 1000 mA / cm ² , preferably in the range from 0.1 to 1000 mA / cm ² , more preferably in the range from 0.2 to 200 mA / cm ² , more preferably in the range of 0.3 to 100 mA / cm ² and particularly preferably in the range of 0.5 to 50 mA / cm ² .

The process according to the invention is generally carried out at a temperature in the range from 0 ° C. to the boiling point, preferably in the range from 20 ° C. to the boiling point of the particular reaction medium or of the at least one solvent used, preferably under atmospheric pressure. It is also possible that Process under pressure, wherein pressure and temperature are preferably chosen so that the reaction medium is preferably at least partially liquid.

In general, the process according to the invention is carried out at a pressure in the range from 0.5 to 50 bar, preferably in the range from 1 to 6 bar and particularly preferably at atmospheric pressure.

Depending on the nature and state of the components of the reaction medium, the electrochemical preparation of the reaction intermediate according to the invention in step a) can in principle also be carried out without additional solvent. This is the case, for example, when the first organic compound acts as a solvent in the reaction medium.

Likewise, without the use of a solvent, it is basically possible to carry out the process according to the invention, for example in the melt, wherein at least one constituent of the reaction medium is in the molten state.

According to a preferred embodiment of the present invention, the reaction medium contains at least one suitable solvent in addition to the first organic compound and optionally to the at least one conducting salt and optionally to the at least one cathodic depolarization compound. In this case, the chemical nature and the amount of this at least one solvent can be adapted to the first organic compound and / or to the at least one conductive salt and / or to the at least one cathodic depolarization compound and / or to the at least one metal ion.

• Wasser;
• Alkohole mit 1, 2, 3 oder 4 Kohlenstoffatomen wie Methanol, Ethanol, n-Propanol, iso-Propanol, n-Butanol, iso-Butanol, tert-Butanol;
• Carbonsäuren mit 1, 2, 3 oder 4 Kohlenstoffatomen wie Ameisensäure, Essigsäure, Propionsäure oder Butansäure;
• Nitrile wie beispielsweise Acetonitril oder Cyanobenzol;
• Ketone wie beispielsweise Aceton;
• Mindestens einfach halogensubstituierte niedere Alkane wie beispielsweise Methylenchlorid oder 1,2-Dichlorethan;
• Säureamide wie beispielsweise Amide von niederen Carbonsäuren wie beispielsweise Carbonsäuren mit 1, 2, 3 oder 4 Kohlenstoffatomen wie Amide der Ameisensäure, Essigsäure, Propionsäure oder Butansäure wie beispielsweise Formamid, Dimethylformamid (DMF), Diethylformamid (DEF), t-Butylformamid, Acetamid, Dimethylacetamid, Diethylacetamid oder t-Butyl-Acetamid;
• Cyclische Ether wie beispielsweise Tetrahydrofuran oder Dioxan;
• N-Formylamide oder N-Acetylamide oder symmetrische oder unsymmetrische Harnstoffderivate primärer, sekundärer oder cyclischer Amine wie beispielsweise Ethylamin, Diethylamin, Piperidin oder Morpholin;
• Amine wie beispielsweise Ethanolamin, Triethylamin oder Etyhlendiamin;
• Dimethylsulfoxid;
• Pyridin;
• Trialkylphosphite und Phosphate;

oder Gemische aus zwei oder mehr der vorgenannten Verbindungen.In principle, all solvents or all solvent mixtures in which the reactants used in step a) of the process according to the invention can be at least partially dissolved or suspended under the chosen reaction conditions such as pressure and temperature are conceivable as solvents. Examples of solvents used include

• Water;
• Alcohols having 1, 2, 3 or 4 carbon atoms, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol;
• Carboxylic acids having 1, 2, 3 or 4 carbon atoms, such as formic acid, acetic acid, propionic acid or butanoic acid;
• Nitriles such as acetonitrile or cyanobenzene;
• Ketones such as acetone;
• At least one halogen-substituted lower alkanes such as methylene chloride or 1,2-dichloroethane;
• Acid amides such as amides of lower carboxylic acids such as carboxylic acids having 1, 2, 3 or 4 carbon atoms such as amides of formic acid, acetic acid, propionic acid or butyric acid such as formamide, dimethylformamide (DMF), diethylformamide (DEF), t-butylformamide, acetamide, dimethylacetamide , Diethylacetamide or t-butyl-acetamide;
• Cyclic ethers such as tetrahydrofuran or dioxane;
• N-formylamides or N-acetylamides or symmetrical or unsymmetrical urea derivatives of primary, secondary or cyclic amines, for example ethylamine, diethylamine, piperidine or morpholine;
• Amines such as ethanolamine, triethylamine or ethylenediamine;
• dimethyl sulfoxide;
• pyridine;
• Trialkyl phosphites and phosphates;

or mixtures of two or more of the aforementioned compounds.

Preference is given to organic solvents, in particular alcohols.

The term "solvent" as used above includes both pure solvents and solvents which contain in small amounts at least one further compound such as preferably water. In this case, the water contents of the abovementioned solvents are in the range of up to 1% by weight, preferably in the range of up to 0.5% by weight, particularly preferably in the range from 0.01 to 0.5% by weight. %, and more preferably in the range of 0.1 to 0.5 wt .-%. For the purposes of the present invention, the term "methanol" or "ethanol" or "acetonitrile" or "DMF" or "DEF" is understood as meaning, for example, a solvent which in each case particularly preferably contains water in the range from 0.1 to 0.5% by weight .-% may contain.

The preferred solvents used in step a) of the process according to the invention are methanol, ethanol, acetonitrile, DMF and DEF or a mixture of two or more of these compounds. Very particularly preferred solvents are methanol, ethanol, DMF, DEF and a mixture of two or more of these compounds. In particular, methanol is preferred.

In the context of a preferred embodiment, at least one protic solvent is used as the solvent. This is preferably used, inter alia, if the cathodic formation of hydrogen is to be achieved in order to avoid the reprecipitation of the at least one metal ion provided by anodic oxidation described below.

For example, in the case where methanol is used as the solvent, the temperature in step a) of the process according to the invention under normal pressure is generally in the range from 0 to 90 ° C .; preferably in the range of 0 to 65 ° C and particularly preferably in the range of 25 to 65 ° C.

For example, in the case where ethanol is used as the solvent, the temperature in the process according to the invention under normal pressure is generally in the range from 0 to 100 ° C .; preferably in the range of 0 to 78 ° C and more preferably in the range of 25 to 78 ° C.

The pH of the reaction medium is adjusted in the process according to the invention so that it is favorable for the synthesis or the stability or preferably for the synthesis and the stability of the framework. For example, the pH can be adjusted via the at least one conductive salt.

When the reaction is carried out as a batch reaction, the reaction time is generally in the range of up to 30 hours, preferably in the range of up to 20 hours. more preferably in the range of 1 to 10 hours, and more preferably in the range of 1 to 5 hours.

It is particularly preferred that the ratio of the reaction time for step (b) to step (a) is at least 1: 1. More preferably, the ratio is at least 2: 1, more preferably at least 5: 1, and most preferably at least 10: 1.

The first organic compound is a mono-, bi- or polycyclic saturated or unsaturated hydrocarbon in which at least two ring carbon atoms are replaced by heteroatoms selected from the group consisting of N, O and S.

Preferably, the first organic compound contains at least nitrogen as the ring atom, more preferably nitrogen occurs as the heteroatom.

The hydrocarbon may be unsubstituted or substituted. If more than one substituent occurs, the substituents may be the same or different. Substituents independently of one another may be phenyl, amino, hydroxy, thio, halogen, pseudohalogen, formyl, amide, an acyl having an aliphatic saturated or unsaturated hydrocarbon radical having 1 to 4 carbon atoms and an aliphatic branched or unbranched saturated or unsaturated hydrocarbon having 1 to 4 carbon atoms be. If the substituents contain one or more hydrogen atoms, each of these independently can also be replaced by an aliphatic branched or unbranched saturated or unsaturated hydrocarbon having 1 to 4 carbon atoms.

Halogen may be fluorine, chlorine, bromine or iodine. Pseudohalogens are, for example, cyano, cyanato or isocyanato.

An aliphatic branched or unbranched saturated or unsaturated hydrocarbon having 1 to 4 carbon atoms is, for example, methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, vinyl, ethynyl or allyl.

An acyl with an aliphatic saturated or unsaturated hydrocarbon radical having 1 to 4 carbon atoms is, for example, acetyl or ethylcarbonyl.

Preferably, the first organic compound is unsubstituted or has a substituent which is methyl or ethyl.

Preferably, the mono-, bi- or polycyclic hydrocarbon has 5- or 6-rings, more preferably 6-rings.

Furthermore, it is preferred that the at least two heteroatoms are nitrogen.

Further preferably, the first organic compound has exactly two heteroatoms, preferably nitrogen.

In the event that the hydrocarbon has a 6-membered ring in which two heteroatoms, preferably nitrogen, are present, these are preferably in the para position relative to one another.

It is further preferred that the first organic compound can be derived from an unsaturated hydrocarbon that is aromatic or fully saturated. If the first organic compound has more than one ring, at least one ring is preferably aromatic.

The monocyclic hydrocarbon from which the first organic compound is derived is, for example, cyclobutane, cyclobutene, cyclobutadiene, cyclopentane, cyclopentene, cyclopentadiene, benzene, cyclohexane or cyclohexene. Preferably, the monocyclic hydrocarbon from which the second organic compound is derived is benzene or cyclohexane.

The bicyclic hydrocarbon from which the first organic compound derives, for example, may consist of two rings linked together via a single covalent bond or through a group R.

R can be -O-, -NH-, -S-, -OC (O) -, -NHC (O) -, -N = N-, or an aliphatic branched or unbranched saturated or unsaturated hydrocarbon having 1 to 4 carbon atoms selected from the group consisting of -O-, -NH-, -S-, -OC (O) -, -NHC (O) - and -N = N-- with one or more independently of one another with a plurality of atoms or functional groups. can be interrupted.

Examples of a bicyclic hydrocarbon from which the first organic compound is derived and consisting of two rings linked together via a single covalent bond or via a group R are biphenyl, stilbene, biphenyl ether, N-phenylbenzamide and azobenzene. Preference is given to biphenyl.

Furthermore, the bicyclic hydrocarbon from which the first compound is derived may be fused ring systems.

Examples of these are decalin, tetralin, naphthalene, indene, indane, pentalen. Preference is given to tetralin and naphthalene.

Furthermore, the bicyclic hydrocarbon from which the first organic compound is derived may have a bridging ring system.

Examples of these are bicyclo [2.2.1] heptane or bicyclo [2.2.2] octane, the latter being preferred.

Likewise, the polycyclic hydrocarbon from which the first organic compound derives may contain fused and / or bridged ring systems.

Examples of these are biphenylene, indacene, fluorene, phenalen, phenanthrene, anthracene, naphthacene, pyrene, crysene, triphenylene, 1,4-dihydro-1,4-ethanonaphthalene and 9,10-dihydro-9,10-ethanoanthracene. Preference is given to pyrene, 1,4-dihydro-1,4-ethanonaphthalene and 9,10-dihydro-9,10-ethanoanthracene.

If the first organic compound has more than one ring, the at least two heteroatoms may be on one or more rings.

und substituierte Derivate davon.Particularly preferably, the first organic compound is selected from the group consisting of

and substituted derivatives thereof.

Suitable substituents are the substituents generally listed above for the first organic compound. Particularly preferred substituents are methyl and ethyl. Most preferably, the substituted derivatives have only one substituent. Very particularly preferred substituted derivatives are 2-methylimidazole and 2-ethylimidazole.

The second organic compound is derived from a di-, tri- or tetracarboxylic acid.

There may be other at least bidentate organic compounds involved in the construction of the framework, which can be used in step (b) of the method according to the invention. However, it is also possible that, moreover, not at least bidentate organic compounds are contained in the framework material. These may, for example, be derived from a monocarboxylic acid and be present both in step (a) and in step (b) of the process according to the invention.

The term "derive" in the context of the present invention means that the di-, tri- or tetracarboxylic acid can be present in the framework material in partially deprotonated or completely deprotonated form. Furthermore, the di-, tri- or tetracarboxylic acid may contain a substituent or independently of one another several substituents. Examples of such substituents are -OH, -NH ₂ , -OCH ₃ , -CH ₃ , -NH (CH ₃ ), -N (CH ₃ ) ₂ , -CN and halides. In addition, the term "derive" in the context of the present invention means that the di-, tri- or tetracarboxylic acid can also be present in the form of the corresponding sulfur analogs. Sulfur analogues are the functional groups -C (= O) SH and its tautomer and C (= S) SH, which can be used instead of one or more carboxylic acid groups. In addition, the term "derive" in the context of the present invention means that one or more carboxylic acid functions can be replaced by a sulfone group (-SO ₃ H). In addition, a sulfonic acid group may also occur in addition to the 2, 3 or 4 carboxylic acid functions.

The di-, tri- or tetracarboxylic acid has, in addition to the abovementioned functional groups, an organic main body or an organic compound to which these are bonded. In this case, the abovementioned functional groups may in principle be bound to any suitable organic compound, as long as it is ensured that the organic compound having these functional groups is capable of forming the coordinative bond for the preparation of the framework.

Preferably, the second organic compound is derived from a saturated or unsaturated aliphatic compound or an aromatic compound or an aliphatic as well as an aromatic compound.

The aliphatic compound or the aliphatic portion of the both aliphatic and aromatic compound may be linear and / or branched and / or cyclic, wherein also several cycles per compound are possible. More preferably, the aliphatic compound or the aliphatic portion of the both aliphatic and aromatic compounds contains 1 to 18, more preferably 1 to 14, further preferably 1 to 13, further preferably 1 to 12, further preferably 1 to 11 and particularly preferably 1 to 10 C atoms such as 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 C atoms. Methane, adamantane, acetylene, ethylene or butadiene are particularly preferred in this case.

The aromatic compound or the aromatic part of both aromatic and aliphatic compound may have one or more cores, such as two, three, four or five cores, wherein the cores may be separated from each other and / or at least two nuclei in condensed form. Especially Preferably, the aromatic compound or the aromatic moiety of the both aliphatic and aromatic compound has one, two or three nuclei, with one or two nuclei being particularly preferred. Independently of each other, furthermore, each nucleus of the compound mentioned can contain at least one heteroatom, such as, for example, N, O, S, B, P, Si, preferably N, O and / or S. More preferably, the aromatic compound or the aromatic moiety of the both aromatic and aliphatic compounds contains one or two C ₆ cores, the two being either separately or in condensed form. In particular, benzene, naphthalene and / or biphenyl and / or bipyridyl and / or pyridyl may be mentioned as aromatic compounds.

More preferably, the second organic compound is an aliphatic or aromatic, acyclic or cyclic hydrocarbon having from 1 to 18, preferably 1 to 10 and especially 6 carbon atoms, which additionally has only 2, 3 or 4 carboxyl groups as functional groups.

For example, the second organic compound is derived from a dicarboxylic acid such as oxalic, succinic, tartaric, 1,4-butanedicarboxylic, 1,4-butenedicarboxylic, 4-oxo-pyran-2,6-dicarboxylic, 1,6-hexanedicarboxylic, Decanedicarboxylic acid, 1,8-heptadecanedicarboxylic acid, 1,9-heptadecane dicarboxylic acid, heptadecanedicarboxylic acid, acetylenedicarboxylic acid, 1,2-benzenedicarboxylic acid, 1,3-benzenedicarboxylic acid, 2,3-pyridinedicarboxylic acid, pyridine-2,3-dicarboxylic acid, 1,3-butadiene 1,4-dicarboxylic acid, 1,4-benzenedicarboxylic acid, p-benzenedicarboxylic acid, imidazole-2,4-dicarboxylic acid, 2-methylquinoline-3,4-dicarboxylic acid, quinoline-2,4-dicarboxylic acid, quinoxaline-2,3-dicarboxylic acid, 6-chloroquinoxaline-2,3-dicarboxylic acid, 4,4'-diaminophenylmethane-3,3'-dicarboxylic acid, quinoline-3,4-dicarboxylic acid, 7-chloro-4-hydroxyquinoline-2,8-dicarboxylic acid, diimide dicarboxylic acid, pyridine 2,6-dicarboxylic acid, 2-methylimidazole-4,5-dicarboxylic acid, thiophene-3,4-dicarboxylic acid, 2-isopropylimidazole-4,5-dicarboxylic acid acid, tetrahydropyran-4,4'-dicarboxylic acid, perylene-3,9-dicarboxylic acid, perylenedicarboxylic acid, pluriol E 200-dicarboxylic acid, 3; 6-dioxaoctanedicarboxylic acid, 3,5-cyclohexadiene-1,2-dicarboxylic acid, octadicarboxylic acid, pentane-3, 3-carboxylic acid, 4,4'-diamino-1,1'-diphenyl-3,3'-dicarboxylic acid, 4,4'-diaminodiphenyl-3,3'-dicarboxylic acid, benzidine-3,3'-dicarboxylic acid, 1, 4-bis (phenylamino) benzene-2,5-dicarboxylic acid, 1,1'-dinaphthyldicarboxylic acid, 7-chloro-8-methylquinoline-2,3-dicarboxylic acid, 1-anilinoanthraquinone-2,4'-dicarboxylic acid, polytetrahydrofuran 250-dicarboxylic acid, 1,4-bis (carboxymethyl) -piperazine-2,3-dicarboxylic acid, 7-chloroquinoline-3,8-dicarboxylic acid, 1- (4-carboxy) -phenyl-3- (4-chloro) - phenylpyrazoline-4,5-dicarboxylic acid, 1,4,5,6,7,7-hexachloro-5-norbornene-2,3-dicarboxylic acid, phenylindane dicarboxylic acid, 1,3-dibenzyl-2-oxo-imidazolidine-4,5 dicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, naphthalene-1,8-dicarboxylic acid, 2-benzoylbenzene-1,3-dicarboxylic acid, 1,3-dibenzyl-2-oxoimidazolidine-4,5-cis-dicar carboxylic acid, 2,2'-biquinoline-4,4'-dicarboxylic acid, pyridine-3,4-dicarboxylic acid, 3,6,9-trioxaundecanedicarboxylic acid, Hydroxybenzophenone dicarboxylic acid, Pluriol E 300 dicarboxylic acid, Pluriol E 400 dicarboxylic acid, Pluriol E 600 dicarboxylic acid, pyrazole-3,4-dicarboxylic acid, 2,3-pyrazine dicarboxylic acid, 5,6-dimethyl-2,3-pyrazine dicarboxylic acid, 4,4 ' Diaminodiphenyl ether diimide dicarboxylic acid, 4,4'-diaminodiphenylmethanediimide dicarboxylic acid, 4,4'-diaminodiphenylsulfonediimide dicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,3-adamantanedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 8-methoxy 2,3-naphthalenedicarboxylic acid, 8-nitro-2,3-naphthalenecarboxylic acid, 8-sulfo-2,3-naphthalenedicarboxylic acid, anthracene-2,3-dicarboxylic acid, 2 ', 3'-diphenyl-p-terphenyl-4 , 4 "-dicarboxylic acid, diphenyl ether-4,4'-dicarboxylic acid, imidazole-4,5-dicarboxylic acid, 4 (1H) -oxothiochromene-2,8-dicarboxylic acid, 5-tert-butyl-1,3-benzenedicarboxylic acid, 7 , 8-Quinolinedicarboxylic acid, 4,5-imidazoledicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, hexatriacontanedicarboxylic acid, tetradecanedicarboxylic acid, 1,7-H eptadicarboxylic acid, 5-hydroxy-1,3-benzenedicarboxylic acid, 2,5-dihydroxy-1,4-dicarboxylic acid, pyrazine-2,3-dicarboxylic acid, furan-2,5-dicarboxylic acid, 1-nonene-6,9-dicarboxylic acid, Eicosendicarboxylic acid, 4,4'-dihydroxydiphenylmethane-3,3'-dicarboxylic acid, 1-amino-4-methyl-9,10-dioxo-9,10-dihydroanthracene-2,3-dicarboxylic acid, 2,5-pyridinedicarboxylic acid, cyclohexene 2,3-dicarboxylic acid, 2,9-dichlorofluorubin-4,11-dicarboxylic acid, 7-chloro-3-methylquinoline-6,8-dicarboxylic acid, 2,4-dichlorobenzophenone-2 ', 5'-dicarboxylic acid, 1,3- Benzenedicarboxylic acid, 2,6-pyridinedicarboxylic acid, 1-methylpyrrole-3,4-dicarboxylic acid, 1-benzyl-1H-pyrrole-3,4-dicarboxylic acid, anthraquinone-1,5-dicarboxylic acid, 3,5-pyrazoldicarboxylic acid, 2-nitrobenzene 1,1,4-dicarboxylic acid, heptane-1,7-dicarboxylic acid, cyclobutane-1,1-dicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 5,6-dehydronorbornane-2,3-dicarboxylic acid, 5-ethyl-2,3-pyridinedicarboxylic acid or camphordicarboxylic

More preferably, the second organic compound is one of the above exemplified dicarboxylic acid as such.

For example, the second organic compound may be derived from a tricarboxylic acid, such as

2-hydroxy-1,2,3-propanetricarboxylic acid, 7-chloro-2,3,8-quinolinetricarboxylic acid, 1,2,3-, 1,2,4-benzenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 2-phosphono 1,2,4-butanetricarboxylic acid, 1,3,5-benzenetricarboxylic acid, 1-hydroxy-1,2,3-propanetricarboxylic acid, 4,5-dihydro-4,5-dioxo-1H-pyrrolo [2,3-F ] quinoline-2,7,9-tricarboxylic acid, 5-acetyl-3-amino-6-methylbenzene-1,2,4-tricarboxylic acid, 3-amino-5-benzoyl-6-methylbenzene-1,2,4-tricarbon acid, 1,2,3-propanetricarboxylic acid or aurintricarboxylic acid,

More preferably, the second organic compound is one of the above exemplified tricarboxylic acids as such.

Exemplary of a second organic compound derived from a tetracarboxylic acid, such as

1,1-Dioxyperylo [1,12-BCD] thiophene-3,4,9,10-tetracarboxylic acid, perylenetetracarboxylic acids such as perylene-3,4,9,10-tetracarboxylic acid or perylene-1,12-sulfone-3,4, 9,10-tetracarboxylic acid, butanetetracarboxylic acids such as 1,2,3,4-butanetetracarboxylic acid or meso-1,2,3,4-butanetetracarboxylic acid, decane-2,4,6,8-tetracarboxylic acid, 1,4,7,10, 13,16-Hexaoxacyclooctadecane-2,3,11,12-tetracarboxylic acid, 1,2,4,5-benzenetetracarboxylic acid, 1,2,11,12-dodecantetracarboxylic acid, 1,2,5,6-hexane-tetracarboxylic acid, 1, 2,7,8-Octanetetracarboxylic acid, 1,4,5,8-naphthalenetetracarboxylic acid, 1,2,9,10-decantetracarboxylic acid, benzophenonetetracarboxylic acid, 3,3 ', 4,4'-benzophenetetracarboxylic acid, tetrahydrofurantetracarboxylic acid or cyclopentanetetracarboxylic acids such as cyclopentane 1,2.3.4-tetracarboxylic acid.

More preferably, the second organic compound is one of the above exemplified tetracarboxylic acids as such.

Very particular preference is given to using at least mono-, di-, tri-, tetra- or higher-nuclear aromatic di-, tri- or tetracarboxylic acids, where each of the cores can contain at least one heteroatom, where two or more nuclei have identical or different heteroatoms may contain. For example, preference is given to monocarboxylic dicarboxylic acids, monocarboxylic tricarboxylic acids, monocarboxylic tetracarboxylic acids, dicercaric dicarboxylic acids, dicercaric tricarboxylic acids, dicercaric tetracarboxylic acids, tricyclic dicarboxylic acids, tricarboxylic tricarboxylic acids, tricarboxylic tetracarboxylic acids, tetracyclic dicarboxylic acids, tetracarboxylic tncarboxylic acids and / or tetracyclic tetracarboxylic acids. Suitable heteroatoms are, for example, N, O, S, B, P. Preferred heteroatoms here are N, S and / or O. A suitable substituent in this regard is, inter alia, -OH, a nitro group, an amino group or an alkyl or alkoxy group.

Especially preferred as at least bidentate organic compounds are acetylenedicarboxylic acid (ADC), campherdicarboxylic acid, fumaric acid, succinic acid. Benzenedicarboxylic acids, naphthalenedicarboxylic acids, biphenyldicarboxylic acids such as 4,4'-biphenyldicarboxylic acid (BPDC), pyrazinedicarboxylic acids such as 2,5-pyrazinedicarboxylic acid, bipyridinedicarboxylic acids such as 2,2'-bipyridinedicarboxylic acids such as 2,2'-bipyridine-5,5'-dicarboxylic acid Benzene tricarboxylic acids such as 1,2,3-, 1,2,4-benzenetricarboxylic acid or 1,3,5-benzenetricarboxylic acid (BTC), benzene tetracarboxylic acid, adamantane tetracarboxylic acid (ATC), adamantane dibenzoate (ADB) benzene tribenzoate (BTB), methanetetrabenzoate (MTB) , Adamantane tetrabenzoate or dihydroxyterephthalic acid such as 2,5-dihydroxyterephthalic acid (DHBDC).

Very particular preference is given inter alia to phthalic acid, isophthalic acid, terephthalic acid, 2-aminoterephthalic acid, 5-aminoisophthalic acid, 4,4'-biphenyldicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, (+) camphorsic acid, succinic acid, 1,4-naphthalenedicarboxylic acid, 1,5 Naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,2,3-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,3,5-benzenetricarboxylic acid, 1,2,3,4-benzenetetracarboxylic acid or 1,2,4,5 -Benzoltetracarbonsäure.

In addition to these at least bidentate organic compounds, the organometallic framework material may also comprise one or more monodentate ligands and / or one or more at least bidentate ligands which are not derived from a di-, tri- or tetracarboxylic acid.

The at least one at least bidentate organic compound preferably contains no hydroxyl or phosphonic acid groups.

As already stated, one or more carboxylic acid functions can be replaced by a sulfonic acid function. In addition, a sulfonic acid group may additionally be present. Finally, it is also possible that all carboxylic acid functions are replaced by a sulfonic acid function.

Such sulfonic acids or their salts which are commercially available are, for example, 4-amino-5-hydroxynaphthalene-2,7-disulfonic acid, 1-amino-8-naphthol-3,6-disulfonic acid, 2-hydroxynaphthalene-3,6- disulfonic acid, benzene-1,3-disulfonic acid, 1,8-dihydroxynaphthalene-3,6-disulfonic acid, 1,2-dihydroxybenzene-3,5-disulfonic acid, 4,5-dihydroxynaphthalene-2,7-disulfonic acid, 2.9- Dimethyl-4,7-diphenyl-1,10-phenanthrolinedisulfonic acid, 4,7-diphenyl-1,10-phenanthrolinedisulfonic acid, ethane-1,2-disulfonic acid, naphthalene-1,5-disulfonic acid, 2- (4-nitrophenylazo) - 1,8-dihydroxynaphthalene-3,6-disulfonic acid, 2,2'-dihydroxy-1,1'-azonaphthalene-3 ', 4,6'-trisulfonic acid.

The first organic compound is used in a concentration which is generally in the range of 0.1 to 30 wt .-%, preferably in the range of 0.5 to 20 wt .-% and particularly preferably in the range of 2 to 10 wt. -%, each based on the total weight of the reaction system minus the weight of the anode and the cathode. Accordingly, the term "concentration" in this case includes both the amount of the first organic compound dissolved in the reaction system and, for example, the amount of the first organic compound optionally suspended in the reaction system.

According to a preferred embodiment of the method according to the invention, the first organic compound becomes, depending on the progress of the electrolysis and in particular as a function of the decomposition of the anode or release the at least one metal ion and / or continuously and / or discontinuously added depending on the formation of the reaction intermediate.

According to a particularly preferred embodiment for step a) of the process according to the invention, the reaction medium contains at least one suitable electrolyte salt. Depending on the first organic compound used and / or the solvent optionally used, it is also possible in the process according to the invention to carry out the preparation of the reaction intermediate without additional conductive salt.

There are essentially no restrictions with regard to the conductive salts which can be used in step a) of the process according to the invention. For example, salts of mineral acids, sulfonic acids, phosphonic acids, boronic acids, alkoxysulfonic acids or carboxylic acids or other acidic compounds such as sulfonic acid amides or imides are preferably used.

Possible anionic components of the at least one conductive salt are accordingly, inter alia, sulfate, nitrate, nitrite, sulfite, disulfite, phosphate, hydrogen phosphate, dihydrogen phosphate, diphosphate, triphosphate, phosphite, chloride, chlorate, bromide, bromate, iodide, iodate, carbonate or bicarbonate.

Alkali metal ions such as Li ⁺ , Na ⁺ , K ⁺ or Rb ⁺ , alkaline earth metal ions such as Mg ²⁺ , Ca ²⁺ , Sr ²⁺ or Ba ²⁺ , ammonium ions or phosphonium ions may be mentioned as cation component of the conductive salts which can be used according to the invention.

With regard to the ammonium ions, mention may be made of quaternary ammonium ions and protonated mono-, di- and triamines.

• symmetrische Ammoniumionen wie etwa Tetraalkylammonium mit bevorzugt C₁-C₄-Alkyl, beispielsweise Methyl, Ethyl, n-Propyl, iso-Propyl, n-Butyl, iso-Butyl. tert-Butyl, wie Tetramethylammonium, Tetraethylammonium, Tetrapropylammonium, Tetrabutylammonium oder
• unsymmetrische Ammoniumionen wie etwa unsymmetrische Tetraalkylammonium mit bevorzugt C₁-C₄-Alkyl, beispielsweise Methyl, Ethyl, n-Propyl, iso-Propyl, n-Butyl, iso-Butyl. tert-Butyl, wie beispielsweise Methyltributylammonium oder
• Ammoniumionen mit mindestens einem Aryl wie beispielsweise Phenyl oder Naphthyl oder mindestes einem Alkaryl wie beispielsweise Benzyl oder mindestens einem Aralkyl und mindestens einem Alkyl, bevorzugt C₁-C₄-Alkyl, beispielsweise Methyl, Ethyl, n-Propyl, iso-Propyl, n-Butyl, iso-Butyl, tert-Butyl, wie etwa Aryltrialkyl wie etwa Benzyltrimethylammonium oder Benzyltriethylammonium.

Examples of preferably used according to the invention quaternary ammonium ions in step a) of the method according to the invention include

• symmetrical ammonium ions such as tetraalkylammonium with preferably C ₁ -C ₄ -alkyl, for example methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl. tert-butyl, such as tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium or
• unsymmetrical ammonium ions such as unsymmetrical tetraalkylammonium preferably having C ₁ -C ₄ -alkyl, for example methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl. tert-butyl, such as methyltributylammonium or
• Ammonium ions having at least one aryl such as phenyl or naphthyl or at least one alkaryl such as benzyl or at least one aralkyl and at least one alkyl, preferably C ₁ -C ₄ alkyl, for example methyl, ethyl, n-propyl, iso-propyl, n- Butyl, iso-butyl, tert-butyl, such as aryl trialkyl such as benzyltrimethylammonium or benzyltriethylammonium.

According to a particularly preferred embodiment, in step a) of the process according to the invention, at least one conducting salt is used which contains a methyltributylammonium ion as at least one cationic component.

According to a particularly preferred embodiment, methyltributylammonium methylsulfate is used as conductive salt in the process according to the invention in step a).

Conductive salts which can also be used in the process according to the invention are ionic liquids such as, for example, methylethylimidazolium chloride or methylbutylimidazolium chloride.

According to a likewise preferred embodiment, methanesulfonate is used as conductive salt in the process according to the invention.

Protonated or quaternary heterocycles, such as, for example, the imidazolium ion, may also be mentioned as the cation component of the at least one conducting salt.

Within the scope of a preferred embodiment of the process according to the invention, it is possible, via the cationic and / or anionic component of the at least one conducting salt, to introduce into the reaction medium compounds which are used for the construction of the reaction intermediate. These compounds are those which influence the formation of the structure of the reaction intermediate, but are not contained in the resulting intermediate, and also those contained in the resulting intermediate. In particular, in the process according to the invention, at least one compound can be introduced via at least one conducting salt which is contained in the resulting reaction intermediate.

Within the scope of one embodiment of the method according to the invention, it is thus possible for step a), in addition to the at least one anode as metal ion source, to introduce the metal ion into the reaction medium via the cationic component of the at least one conducting salt. It is likewise possible, via the cationic component of the at least one conducting salt, to introduce at least one metal ion into the reaction medium which is different from the at least one metal ion introduced via anodic oxidation, which difference can relate to the valency of the cation and / or the type of metal.

Accordingly, the present invention also describes a method as described above, characterized in that the at least one conducting salt contains a salt of the first organic compound.

The concentration of the at least one conducting salt in the context of the process according to the invention is generally in the range from 0.01 to 10% by weight, preferably in the range from 0.05 to 5% by weight and particularly preferably in the range from 0.1 to 3 wt .-%, each based on the sum of the weights of all present in the reaction system Leitsalze and further based on the total weight of the reaction system without consideration of the anodes and cathodes.

If step a) of the process is carried out in batch mode, the reaction medium with the starting materials is generally first provided, then current is applied and then pumped around.

If the process is carried out continuously, a partial stream is generally discharged from the reaction medium, the reaction intermediate contained therein is isolated and the mother liquor is recycled.

According to a particularly preferred embodiment, step a) of the method according to the invention is carried out in such a way that the redeposition of the metal ion liberated by anodic oxidation at the cathode is prevented.

For example, this redeposition is preferably prevented according to the invention by using a cathode which has a suitable hydrogen overvoltage in a given reaction medium. Such cathodes are, for example, the above-mentioned graphite, copper, zinc, tin, manganese, silver, gold, platinum cathodes or cathodes containing alloys such as steels, bronzes or brass.

For example, the redeposition is preferably further prevented according to the invention by using an electrolyte in the reaction medium which favors the cathodic formation of hydrogen. In this regard, among other things, an electrolyte is preferred which contains at least one protic solvent. Preferred examples of such solvents are listed above. Particularly preferred are alcohols, more preferably methanol and ethanol.

For example, the redeposition is preferably further prevented by the reaction medium containing at least one compound which leads to a cathodic depolarization. In the context of the present invention, a compound which leads to a cathodic depolarization means any compound which is reduced under given reaction conditions at the cathode.

Preferred cathodic depolarizers include compounds which are hydrodimerized at the cathode. For example, particularly preferred in this context are acrylonitrile, acrylic esters and maleic acid esters, for example dimethyl maleate, which is more preferably preferred.

As cathodic depolarizers further compounds are preferred, among other things, containing at least one carbonyl group, which is reduced at the cathode. Examples of such carbonyl-containing compounds include ketones such as acetone.

Preferred cathodic depolarizers include compounds which have at least one nitrogen-oxygen bond, one nitrogen-nitrogen bond and / or one nitrogen-carbon bond which are reduced at the cathode. Examples of such compounds include compounds with a nitro group, with an azo group, with an azoxy group, oximes, pyridines, imines, nitriles and / or cyanates.

In the context of the method according to the invention, it is further possible to combine at least two of the measures mentioned to prevent cathodic redeposition. For example, it is possible to use both an electrolyte that favors the cathodic formation of hydrogen and to use an electrode with a suitable hydrogen overvoltage. It is also possible to use both an electrolyte which promotes the cathodic formation of hydrogen and at least one compound which leads to a cathodic depolarization. It is also possible to add at least one compound which leads to a cathodic depolarization, as well as to use a cathode with a suitable hydrogen overvoltage. Further, it is possible to use both an electrolyte which promotes the cathodic formation of hydrogen, as well as to use an electrode with a suitable hydrogen overvoltage and to add at least one compound which leads to a cathodic depolarization.

• (i) Verwendung eines Elektrolyten, der die kathodische Bildung von Wasserstoff begünstigt;
• (ii) Zusatz mindestens einer Verbindung, die zu einer kathodischen Depolarisation führt;
• (iii) Einsatz einer Kathode mit einer geeigneten Wasserstoffüberspannung.

Accordingly, the present invention also relates to a method as described above, wherein in step a) the cathodic redeposition of the at least one metal ion is at least partially prevented by at least one of the following measures:

• (i) use of an electrolyte which promotes the cathodic formation of hydrogen;
• (ii) adding at least one compound resulting in cathodic depolarization;
• (iii) use of a cathode with a suitable hydrogen overvoltage.

Likewise, the present invention therefore also relates to a process as described above, wherein the electrolyte according to (i) contains at least one protic solvent, in particular an alcohol, more preferably methanol and / or ethanol.

According to a particularly preferred embodiment, the process according to the invention for step a) is operated in a circular circulation manner. In the context of the present invention, this "electrolysis cycle" is understood as any process procedure in which at least part of the reaction system located in the electrolysis cell is discharged from the electrolysis cell, optionally at least one intermediate treatment step such as at least one temperature treatment or addition and / or separation of at least one component subjected to the discharged stream and returned to the electrolysis cell. Such an electrolysis circuit is particularly preferably carried out in the context of the present invention in combination with a plate-stack cell, a tube cell or a pencil-Sharpener cell.

After preparation, there is generally a reaction intermediate containing the at least one metal ion and the first organic compound. In addition, solvents may still be present.

Typically, the reaction intermediate is present as a suspension. The reaction intermediate can be separated from its mother liquor. This separation process can be carried out in principle according to all suitable methods. Preferably, the intermediate product by solid-liquid separation, centrifugation, extraction, filtration, membrane filtration, crossflow filtration, diafiltration, ultrafiltration, flocculation using flocculation aids such as nonionic, cationic and / or anionic auxiliaries, pH-pen by addition of additives such as salts, acids or bases, flotation, spray drying, spray granulation, or evaporation of the mother liquor at elevated temperatures and / or in vacuo and concentration of the solid separated.

After separation, at least one additional washing step, at least one additional drying step and / or at least one additional calcination step may follow.
If at least one washing step follows in the process according to the invention in step a), it is preferred to wash with at least one solvent used in the synthesis.

If in the process according to the invention in step a), if appropriate after at least one washing step, at least one drying step follows, then the solid material at temperatures generally in the range of 20 to 120 ° C, preferably in the range of 40 to 100 ° C and particularly preferably dried in the range of 56 to 60 ° C.

Also preferred is the drying in vacuo, wherein the temperatures can be generally chosen so that the at least one detergent is at least partially, preferably substantially completely removed from the crystalline porous organometallic framework and at the same time the framework structure is not destroyed.

The drying time is generally in the range of 0.1 to 15 hours, preferably in the range of 0.2 to 5 hours and more preferably in the range of 0.5 to 1 hour.

At least one washing step and optionally at least one drying step may be followed by at least one calcination step in step a), in which the temperatures are preferably chosen so that the structure of the framework material is not destroyed.

In particular, by washing and / or drying and / or calcination, it is possible, for example, at least partially, preferably substantially quantitatively, to remove at least one template compound which was optionally used for the electrochemical preparation of the framework according to the invention.

Preferably, however, the reaction intermediate is used without work-up in step (b).

In step b) of the process according to the invention, as stated above, either the uninsulated reaction intermediate is reacted with a second organic compound or the intermediate product is separated and preferably reacted in a solvent with the second organic compound. This reaction is typically carried out as in classical production processes for porous metal-organic frameworks (ie not electrochemically).

The reaction in step (b) of the process according to the invention for producing a porous organometallic framework can accordingly be carried out in an aqueous medium. In this case, hydrothermal conditions or generally solvothermal conditions can be used. In the context of the present invention, the term "thermal" is to be understood as meaning a preparation process in which the conversion to the porous organometallic framework according to the invention is carried out in a pressure vessel in such a way that it is closed during the reaction and elevated temperature is applied, so that Vapor pressure of existing solvent, a pressure builds up within the reaction medium in the pressure vessel.

Preferably, however, the reaction in step (b) does not occur in an aqueous medium and also not under solvothermal conditions.

The reaction in step (b) of the process according to the invention is preferably carried out in the presence of a nonaqueous solvent.

The reaction in step (b) is preferably carried out at a pressure of at most 2 bar (absolute). However, the pressure is preferably at most 1230 mbar (absolute). Most preferably, the reaction takes place at atmospheric pressure. However, this may result in slight overpressure or underpressure due to the apparatus. Therefore, in the context of the present invention, the term "atmospheric pressure" is to be understood as the pressure range which results from the actual atmospheric pressure of ± 150 mbar.

The reaction can be carried out at room temperature. Preferably, however, this takes place at temperatures above room temperature. Preferably, the temperature is more than 100 ° C. Further preferably, the temperature is at most 180 ° C, and more preferably at most 150 ° C. Suitable ranges for given temperatures are 0 ° C to 250 ° C, more preferably in the range of 50 ° C to 200 ° C, especially 100 ° C to 150 ° C.

Typically, in step (b) of the process according to the invention for producing a porous organometallic framework in water is carried out as a solvent with the addition of another base. This serves in particular to the fact that when using a polybasic carboxylic acid as at least bidentate organic compound, this is readily soluble in water. The preferred use of the nonaqueous organic solvent does not require the use of such a base. Nevertheless, the solvent for the process according to the invention can be such be chosen that this reacts as such basic, but this does not necessarily have to be for the implementation of the method according to the invention.

Likewise, a base can be used. However, it is preferred that no additional base is used.

It is also advantageous that the reaction can take place with stirring, which is also advantageous in a scale-up.

The non-aqueous organic solvent is preferably a C _1-6 alkanol, dimethyl sulfoxide (DMSO), N, N-dimethylformamide (DMF), N, N-diethylformamide (DEF), acetonitrile, toluene, dioxane, benzene, chlorobenzene, methyl ethyl ketone (MEK), pyridine, tetrahydrofuran (THF), ethyl acetate, optionally halogenated C _1-200 alkane, sulfolane, glycol, N-methylpyrrolidone (NMP), γ-butyrolactone, alicyclic alcohols such as cyclohexanol, ketones such as acetone or acetylacetone, cycloketones such as cyclohexanone, sulfolene or mixtures thereof.

A C _1-6 alkanol refers to an alcohol having 1 to 6 C atoms. Examples of these are methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, t-butanol, pentanol, hexanol and mixtures thereof.

An optionally halogenated C _1-200 alkane denotes an alkane having 1 to 200 carbon atoms, it being possible for one or more up to all hydrogen atoms to be replaced by halogen, preferably chlorine or fluorine, in particular chlorine. Examples of these are chloroform, dichloromethane, carbon tetrachloride, dichloroethane, hexane, heptane, octane and mixtures thereof.

Preferred solvents are DMF, DEF and NMP. Particularly preferred is DMF.

The term "non-aqueous" preferably refers to a solvent having a maximum water content of 10% by weight, more preferably 5% by weight, still more preferably 1% by weight, further preferably 0.1% by weight. , particularly preferably 0.01 wt .-% based on the total weight of the solvent does not exceed.

Preferably, the maximum water content during the reaction is 10% by weight, more preferably 5% by weight, and still more preferably 1% by weight.

The term "solvent" refers to pure solvents as well as mixtures of different solvents.

If solvents are used, it is preferred that the same solvent is used for step (a) and step (b) of the process according to the invention.

Further preferably, the process step of reacting the at least one metal compound with the at least one at least bidentate organic compound is followed by a calcination step. The temperature set here is typically more than 250 ° C, preferably 300 to 400 ° C.

Due to the calcination step, the at least bidentate organic compound present in the pores can be removed.

Additionally or alternatively, the removal of the at least bidentate organic compound (ligand) from the pores of the porous organometallic framework material by the treatment of the resulting framework material with a non-aqueous solvent can be carried out. In this case, the ligand is removed in a kind of "extraction process" and optionally replaced in the framework by a solvent molecule. This gentle method is particularly suitable when the ligand is a high-boiling compound.

The treatment is preferably at least 30 minutes and may typically be carried out for up to 2 days. This can be done at room temperature or elevated temperature. This is preferably carried out at elevated temperature, for example at at least 40 ° C., preferably 60 ° C. Further preferably, the extraction takes place at the boiling point of the solvent used instead (under reflux).

The treatment can be carried out in a simple boiler by slurrying and stirring the framework material. It is also possible to use extraction apparatuses such as Soxhlet apparatuses, in particular technical extraction apparatuses.

Suitable solvents may be those mentioned above, for example C _1-6 -alkanol, dimethyl sulfoxide (DMSO), N, N-dimethylformamide (DMF), N, N-diethylformamide (DEF), acetonitrile, toluene, dioxane, benzene, Chlorobenzene, methyl ethyl ketone (MEK), pyridine, tetrahydrofuran (THF), ethyl acetate, optionally halogenated C _1-200 alkane, sulfolane, glycol, N-methylpyrrolidone (NMP), gamma-butyrolactone, alicyclic alcohols such as cyclohexanol, ketones, such as acetone or Acetylacetone, cycloketones such as cyclohexanone or mixtures thereof.
Preferred are methanol, ethanol, propanol, acetone, MEK and mixtures thereof.

A most preferred extraction solvent is methanol.

The solvent used for the extraction may be the same as or different from that for the reaction of the at least one metal compound with the at least one at least bidentate organic compound. In particular, it is not absolutely necessary in the "extraction" but preferred that the solvent is anhydrous.

Examples Example 1 Preparation of a Cu-BDC-TEDA MOF

In an electrolysis cell with a copper rod as the anode (active electrode area 639 m ² ) and a centrically surrounding steel tube with a gap of 2 mm between the anode and cathode is an electrolyte consisting of 1802.6 g of methanol, 30.2 g of TEDA (= triethylenediamine) , 17.2 g Methyltributylammoniummethylsulfat (MTBS) at 45 ° C recirculated (700 l / h). For 1 hour, 14.5 A are applied at a voltage of 7 to 18 V, thereby dissolving 19 g of copper. The experiment is repeated and both discharges combined. There are obtained 3641.5 g of a TEDA-containing Cu-methylate suspension. 309.2 g of the TEDA-containing Cu-methylate suspension (1.04% Cu) are placed in a glass flask and 4.15 g of terephthalic acid are added with stirring. The mixture is stirred at reflux for 24 h. The turquoise product is filtered off and washed 4 x 50 ml of methanol. The product is then dried in a vacuum oven at 50 ° C for 16 h. There are obtained 8.9 g of powder.

The product has a N ₂ surface (Langmuir) of 1892 m ² / g. Using the diffractogram, the MOF can be identified as a Cu ₂ (terephthalate) ₂ (TEDA) structure.

Example 2 Preparation of a Cu-BPDC-TEDA MOF

The synthesis of Example 1 is repeated, but 6.1 g of 4,4'-biphenyl dicarboxylic acid are used instead of the terephthalic acid. There are obtained 10.9 g of a light blue powder.

The product has a N ₂ surface (Langmuir) of 2631 m ² / g. Using the diffractogram, the MOF can be identified as a Cu ₂ (biphenyldicarboxylate) ₂ (TEDA) structure.

Example 3 Preparation of a Cu-aminoterephthalic acid TEDA MOF

The synthesis of Example 1 is repeated, but 4.5 g of aminoterephthalic acid are used instead of terephthalic acid. There are obtained 9.5 g of a powder.

The product has a N ₂ surface (Langmuir) of 1545 m ² / g.

Example 4 Preparation of a Cu-butane tetracarboxylic acid TEDA MOF

The synthesis of Example 1 is repeated except that 2.9 g of 1,2,3,4-butanetetracarboxylic acid are used instead of terephthalic acid. There are obtained 7.5 g of a light blue powder.

Product has a N ₂ surface (Langmuir) of 699 m ² / g.

Example 5 Preparation of a Cu-5-aminoisophthalic acid TEDA MOF

In an electrolytic cell with a copper rod as the anode (active electrode area 639 m ² ) and a centrically surrounding steel tube with a gap of 2 mm between the anode and cathode, an electrolyte consisting of 1802.6 g of methanol, 30.2 g TE-DA, 17 , 2 g Methyltributylammoniummethylsulfat (MTBS) pumped at 46 ° C (700 l / h). For 1 hour, 14.5 A are applied at a voltage of 8.5 to 20.1 V, thereby dissolving 17.5 g of copper. The experiment is repeated and both discharges combined. There are obtained 3664.3 g of a TEDA-containing Cu-methylate suspension. 328.1 g of the TEDA-containing Cu-methylate suspension (0.96% Cu) are initially introduced into a glass flask and 4.53 g of 5-aminoisophthalic acid are added with stirring. The mixture is stirred overnight (about 16 h) under reflux. The olive-colored product is filtered off and washed 3 × 50 ml of methanol. The product is then dried in a vacuum oven at 50 ° C for 16 h. There are obtained 9.3 g of powder.

The product has a N ₂ surface (Langmuir) of 215 m ² / g.

Example 6 Preparation of a Cu succinic acid TEDA MOF

The synthesis of Example 5 is repeated, but 2.95 g of succinic acid are used instead of the aminoisophthalic acid. There are obtained 7.6 g of a greenish blue powder.

Product has a N ₂ surface (Langmuir) of 479 m ² / g.

Example 7 Preparation of a Cu-cyclohexanedicarboxylic acid TEDA MOF

The synthesis of Example 5 is repeated, but 4.4 g of cyclohexane-1,4-dicarboxylic acid are used instead of the aminoisophthalic acid. There are obtained 9.3 g of a greenish blue powder.

Product has a N ₂ surface (Langmuir) of 780 m ² / g.

Example 8 Preparation of a Cu camphors acid TEDA MOF

In an electrolytic cell with a copper rod as the anode (active electrode area 639 m ² ) and a centrically surrounding steel tube with a gap of 2 mm between the anode and cathode, an electrolyte consisting of 1802.6 g of methanol, 30.2 g TE-DA, 17 , 2 g Methyltributylammoniummethylsulfat (MTBS) at 46 ° C recirculated (700 l / h). For 1 hour, 14.5 A are applied at a voltage of 6.7 to 8.6 V, thereby dissolving 16.5 g of copper. The experiment is repeated and both discharges combined. There are obtained 3678.8 g of a TEDA-containing Cu-methylate suspension.

In a glass flask, 357.2 g of the TEDA-containing Cu-methylate suspension (0.90% Cu) are initially charged and 5.00 g (+) camphoric acid are added with stirring. The mixture is stirred overnight (about 16 h) under reflux. The blue-green product is filtered off and washed 3 x 50 ml of methanol. The product is then dried in a vacuum oven at 50 ° C for 16 h. There are obtained 10.6 g of powder.

The product has a N ₂ surface (Langmuir) of 746 m ² / g.

Example 9 Preparation of a Cu-BPDC imidazole MOF

In an electrolytic cell with a copper rod as the anode (active electrode area 639 m ² ) and a centrically surrounding steel tube with a gap of 2 mm between the anode and cathode, an electrolyte consisting of 1814.3 g of methanol, 18.5 g of imidazole, 17.2 g Methyltributylammoniummethylsulfät (MTBS) at 44 ° C recirculated (700 l / h). For 1 hour, 14.5 A are applied at a voltage of 6.8 to 6.5 V, thereby dissolving 26 g of copper. The experiment is repeated and both discharges combined. There are obtained 3662.8 g of a Cu-imidazolide-containing Cu-methylate suspension.

226.4 g of the Cu imidazolide suspension (1.42% Cu) are placed in a glass flask and 6.10 g of 4,4'-biphenyldicarboxylic acid are added with stirring. The mixture is stirred overnight (about 16 h) under reflux. The light blue product is filtered off and washed 3 x 50 ml of methanol. The product is then dried in a vacuum oven at 50 ° C for 16 h. There are obtained 11.2 g of powder.

The product has a N ₂ surface (Langmuir) of 514 m ² / g.

Claims (10)

1. A process for preparing a porous metal organic framework comprising at least two organic compounds coordinated to at least one metal ion, which comprises the steps

   (a) oxidation of at least one anode comprising metal corresponding to the at least one metal ion in a reaction medium in the presence of at least one first organic compound which is an optionally substituted monocyclic, bicyclic or polycyclic saturated or unsaturated hydrocarbon in which at least two ring carbons have been replaced by heteroatoms selected from the group consisting of N, O and S to form a reaction intermediate comprising the at least one metal ion and the first organic compound; and

   (b) reaction of the reaction intermediate at a set temperature with at least one second organic compound which coordinates to the at least one metal ion, with the second organic compound being derived from a dicarboxylic, tricarboxylic or tetracarboxylic acid.
2. The process according to claim 1, wherein the at least one metal ion is selected from the group of metals consisting of copper, iron, aluminum, zinc, magnesium, zirconium, titanium, vanadium, molybdenum, tungsten, indium, calcium, strontium, cobalt, nickel, platinum, rhodium, ruthenium, palladium, scandium, yttrium, a lanthanide, manganese and rhenium.
3. The process according to claim 1 or 2, wherein the first organic compound is selected from the group consisting of

   

   

   

   and substituted derivatives thereof.
4. The process according to any of claims 1 to 3, wherein the second organic compound is selected from the group consisting of phthalic acid, isophthalic acid, terephthalic acid, 2-aminoterephthalic acid, 5-aminoisophthalic acid, 4,4'-biphenyldicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, (+)-camphoric acid, succinic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,2,3-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,3,5-benzenetricarboxylic acid, 1,2,3,4-butanetetracarboxylic acid and 1,2,4,5-benzenetetracarboxylic acid.
5. The process according to any of claims 1 to 4, wherein the oxidation in step (a) is carried out in the presence of an organic solvent.
6. The process according to claim 5, wherein the organic solvent comprises an alcohol.
7. The process according to any of claims 1 to 6, wherein the reaction intermediate is present in a suspension.
8. The process according to any of claims 1 to 7, wherein the reaction intermediate is used without further work-up in step (b).
9. The process according to any of claims 1 to 8, wherein the set temperature in step (b) is in the range from 0°C to 250°C.
10. The process according to any of claims 1 to 9, wherein the ratio of the reaction time for step (b) to that for step (a) is at least 1:1.