Methods for synthesizing environmentally friendly MOFs, especially flexible MOFs

Abstract

The present invention relates to a method for producing MOFs, which are structured metal-organic compounds comprising a two- or three-dimensional porous network of inorganic materials connected by multidentate chelating ligands bound to multiple metal centers, said multidentate chelating ligands being in particular C5-C carboxylic acid functional groups containing at least one carboxylic acid functional group, preferably benzyl or naphthyl di-, tri- or tetracarboxylate. 24 The aromatic or heteroaromatic ligands are selected from the group comprising heteroaromatic and aromatic ligands, and said aromatic or heteroaromatic ligands optionally bearing on at least one aromatic ring a group selected from -NH2, -OH, -CH3, -OCH3, -NO2, -CF3, -COOH, -SO3H, -SH.

Description

[Technical Field]

[0001] The present invention belongs to the field of coordination polymer synthesis, and more specifically relates to the preparation of environmentally friendly crystalline metal-organic frameworks, also known as structured metal-organic frameworks or MOFs, according to a previously undeveloped synthetic route. A compound is said to be environmentally friendly if its release into the natural environment is acceptable. Environmentally friendly MOF compounds do not cause predictable or identifiable impairments or significant disturbances of the ecological balance, and their preparation, use, and end-of-life waste disposal correspond to environmentally friendly MOFs according to their nature: "MOFs Industrialization: A Complete Assessment of Production Costs, Maria Ines Severino, Effrosyni Gkaniatsou, Farid Nouar, Moises L. Pinto, Christian Serre, Faraday Discuss., 2021, 231, 326." [Background technology]

[0002] Bibliographic references in the text below are indicated in [ ] in the text and are listed in the table of references.

[0003] The preparation and study of structured metal-organic frameworks is itself a branch of coordination chemistry with clearly identified applications such as toxic gas capture [1-5], gas storage [6-7], separation technologies [8-12], small molecule catalysis and electrocatalysis [13-15], heat redistribution [16,17], water recovery

[18] , sensing

[19] , and biological applications

[20] . For most of the targeted industrial applications, especially gas separation, gas storage, heat redistribution, and water recovery, the targeted MOFs must be produced in an environmentally friendly manner on very large scales and with minimal energy costs.

[0004] However, the number of MOFs that can be mass-produced on an industrial scale remains very limited compared to the number of MOFs known to date.

[21] However, most of the synthesis routes for MOFs identified to date rely on hydrothermal or solvothermal methods, which require large amounts of energy, which impacts the final production cost. This is incompatible with simpler methods such as heating at atmospheric pressure, while the storage and use of green solvents, such as water / alcohol mixtures, can be considered.

[22]

[0005] Among the various classes of known MOFs, those based on trivalent metal carboxylates, especially those containing Al, are considered to be the most promising for industrial applications due to their high hydrolytic stability compared to MOFs based on divalent metal carboxylates [23-26]. MIL-53(A1), an Al dicarboxylate, is a highly stable, benchmark MOF with a flexible framework

[27] .

[0006] Due to its high structural flexibility and excellent water stability, this MOF has been explored for a wide range of potential applications, such as gas separation[28-30], gas storage

[31] , catalysis[32,33], sensing

[34] , mechanical energy storage

[35] , and nonlinear optical devices

[36] . It has also been shown that the flexibility of this MOF can be utilized for the separation (adsorption and subsequent regeneration) of CO2 in the presence or absence of external stimuli such as mechanical pressure

[37] .

[0007] Other flexible MOFs of interest are solids of the MIL-53 structure but with functional groups on the organic spacer of the MOF: MIL-53(Al)-NH2 and MIL-53(Al)-OH [38-41]. Summary of the Invention [Problem to be solved by the invention]

[0008] These flexible MOFs generally have to be prepared under hydrothermal or solvothermal conditions that are not well suited to large-scale production. To overcome this drawback, one of the aims of the present invention is to produce MOFs using an innovative method that uses commercially available starting materials and green solvents, such as water, alcohols, or mixtures thereof, and implements techniques that are easy to implement, such as heating at ambient pressure.

[0009] The synthesis of MIL-53(Al) has been reported by several protocols, but the use of metal salts, whether by precipitation at ambient temperature using water as a solvent (one environmentally friendly method

[43] ), requires dilute solutions, which significantly reduces the space-time yield (STY) and makes this method impractical from an industrial point of view. Furthermore, to design flexible aluminum-based MOFs, such as MIL-53(Al), the use of Al 3+ The use of Al(NO3)3·6H2O as a source involves significant chemical risks (nitrate), so its production on an industrial scale is less clear, demonstrating a real need to develop alternative synthetic methods.

[0010] Biswas et al. described a method for synthesizing several functionalized MIL-53(Al) structures starting from AlCl3·6H2O

[44] , but this method requires a hydrothermal or solvothermal route and has the aforementioned drawbacks regarding industrial requirements.

[0011] The following synthesis can also be mentioned as prior art: - Synthesis of MIL-53(Fe) and MIL-53(Fe)-NH2 using green solvents, such as water, as the solvent and water-ethanol mixtures as the washing solution, but requiring high temperature and pressure conditions (hydrothermal / solvothermal route) [45, 46]; - synthesis of MOFs, more precisely In(OH)BDC 0.75BDCH 2 , under solvothermal conditions in the presence of hydrofluoric acid and N,N-dimethylformamide (so-called DMF), which is itself known as a toxic solvent

[47] ; and - Synthesis of MIL-53(X) by microwave heating at ambient pressure using a mixture of water and an organic solvent (which may be DMF or dimethyl sulfoxide, also known as DMSO), using exclusively DMF as a washing solution

[48] , where X is aluminum or chromium.

[0012] To overcome these drawbacks, one of the aims of the present invention is to make it possible to produce MOFs using an innovative method implementing techniques that are easy to implement, such as commercially available, inexpensive components, and green solvents, such as water, (ethyl) alcohol, DMSO, or mixtures containing a high proportion of water, and that involve heating at ambient pressure. [Means for solving the problem]

[0013] The present invention relates to a method for producing MOFs, which are structured metal-organic compounds comprising a two- or three-dimensional porous network of inorganic matter connected by multidentate chelating ligands bound to multiple metal centers, the multidentate chelating ligands being: - at least one carboxylic acid functional group selected from ligands containing linear alkyl chains without unsaturation and ligands containing carbon chains containing at least one unsaturation, such as C4-C containing fumaric acid or muconic acid 24 Aliphatic ligands; - at least one carboxylic acid functional group, preferably a C4-C containing benzyl or naphthyl di-, tri- or tetracarboxylate; 24 Heteroaromatic and aromatic ligands, said aromatic or heteroaromatic ligands optionally bearing a group selected from -NH2, -OH, -CH3, -OCH3, -NO2, -CF3, -COOH, -SO3H, -SH on at least one aromatic ring; and selected from the group comprising: The method comprises the steps of: a) dispersing in water molecules of a multidentate chelating ligand and at least one metal precursor (i.e. at least one metal salt), preferably at least one metal precursor selected from metal sulfates and metal chlorates, preferably aluminum sulfate; b) optionally heating the dispersion obtained in a) at ambient pressure and maintaining the dispersion at a temperature of 50-150°C for a time period of 10 minutes to 96 hours; c) returning to ambient temperature, filtering and washing the solid obtained with water; d) drying the solid obtained in c); e) A step of dispersing the solid obtained in d) in a solution containing or consisting of DMSO at a temperature of 150°C or less under stirring for a period of 30 minutes to 15 hours.

[0014] The inventors have demonstrated that the synthesis of MOFs can be carried out in water thanks to a subsequent washing step with DMSO, which allows for the removal of unconverted reagents. Conventional synthesis methods typically require the synthesis (or at least the washing step) to be carried out in a toxic solvent, such as DMF, and the solids in solution to be heated to 150°C for several days, so that impurities are removed with the washing solvent and do not remain trapped in the pores of the MOF.

[0015] Above and below, it is specified that the terms "cleaning" and "activation" are to be understood in the same way and can therefore be fully interchangeable.

[0016] The inventors have also demonstrated that the use of DMSO during the washing step can shorten the time of this step compared to such washing steps carried out with DMF. Moreover, due to the relatively high polarity of DMSO and the good solubility of certain ligands compared to DMF, unconverted reagents are removed more quickly.

[0017] Within the scope of the present invention, the term "aromatic group" refers to a stable, substituted or unsubstituted, unsaturated monocyclic or polycyclic hydrocarbon-based fragment, preferably having 3 to 14 carbon atoms and containing at least one ring that satisfies Hückel's rule for aromaticity.

[0018] The term "heteroaromatic group" as used within the scope of the present invention refers to a stable, substituted or unsubstituted monoheterocyclic or polyheterocyclic fragment, preferably having 3 to 14 carbon atoms and containing at least one ring that satisfies Hückel's rule for aromaticity. Examples of heteroaromatic entities include, but are not limited to, furanyl, pyridinyl (pyridine group), indolinyl (indole group), imidazolinyl (imidazole group), pyrrolinyl (pyrrole group), quinolinyl, dihydroquinolinyl, isoquinolinyl, quinazolinyl, dihydroquinazolyl, and tetrahydroquinazolyl groups. Among ligands containing such groups, 2,5-FDCA and 2,5-furandicarboxylic acid may be mentioned.

[0019] Preferably, the polydentate chelating ligand is chosen from at least one type chosen from bidentate, tridentate and tetradentate ligands, advantageously comprising a C6-C24 aromatic compound containing at least one functional group chosen from carboxylic acid, phosphonic acid, amine, alcohol, ketone and azole functional groups, preferably the polydentate chelating ligand is chosen from at least one of the following ligands: benzene-1,4-dicarboxylic acid or terephthalic acid (C8H6O4, CAS: 100-21-0, abbreviations 1,4-BDC, BDC, H2-BDC or BDC H2), nitro-terephthalic acid (C8H5NO6, CAS: 610-29-7, known by the abbreviation NO2-1,4-BDC), 2-amino-terephthalic acid (C8H5NO4, CAS: 10312-55-7, known by the abbreviation NH2-1,4-BDC), 2-chloroterephthalic acid (C8H5ClO4, CAS: 1967-31-3, known by the abbreviation Cl-1,4-BDC), 1,3,5-benzenetricarboxylic acid (C6H3(CO2H)3, CAS: 554-95-0), 3,3',5,5'-azobenzenetetracarboxylic acid (C 16 H 10 N2O8, CAS: 365549-33-3), 3,5-pyrazoledicarboxylic acid (C5H4N2O4, CAS: 303180-11-2), 2,5-bis(trifluoromethyl)-1,4-benzenedicarboxylic acid (C 10 H4F6O4, CAS: 366008-67-5), 2-(trifluoromethyl)-1,4-benzenedicarboxylic acid (C9H5F3O4, CAS: 1483-47-2), 1,2,4-triazole (C2H3N3, CAS: 288-88-0), 2-methylimidazole (C4H6N2, CAS: 693-98-1), N,N'-piperazine(methylenephosphonic acid) (C6H 16 N2O6P2, CAS: 89280-71-7), L-aspartic acid (C4H7NO4, CAS: 56-84-8), 2,5-dihydroxyterephthalic acid (C8O6H6, CAS: 610-92-4) and 3,4-dihydroxy-3-cyclobutene-1,2-dione (C4O4H2, CAS: 2892-51-5).

[0020] Advantageously, the DMSO is removed by rinsing after step e) in a step f) of treatment with ethanol.

[0021] Preferably, the metal centre of the method for producing a MOF according to the present invention comprises at least one metal selected from Cu, Zn, Ca, Mg, Ti, Zr, In, Ga, V, Cr, Mn, Fe and Al, preferably the metal is a metal ion selected from at least one metal ion of Fe, Al, Cr and Zr, even more preferably selected from at least one metal ion of Fe, Al, Cr and V.

[0022] Preferably, the MOF produced according to the method of the invention is selected from MIL-53, MIL-68, MIL-69, MIL-101, MIP-206, and DUT-7. In a particularly preferred manner, the MOF produced according to the method of the invention is an MOF selected from MIL-53(Al), MIL-53(Fe), MIL-53(Cr), MIL-68(Al), MIL-68(Fe), MIL-68(Cr) and MIP-206(Zr).

[0023] Preferably, the MOF is selected from the MIL-53 class containing metal ions in the oxidation state +3 of a metal selected from Cr, Al, Fe, V, Ga and In, and the aromatic ligand is benzene-1,4-dicarboxylic acid or a derivative.

[0024] Preferably, the benzene-1,4-dicarboxylic acid derivative is benzene-1,4-dicarboxylic acid substituted on the aromatic ring with at least one group selected from -NH2, -OH, -CH3, -NO2, -CF3, -COOH, -SO3H-SH, -OCH3, preferably from the groups -NH2, -OH and -NO2.

[0025] Such a ligand can be, for example, NO2-1,4-BDC, NH2-1,4-BDC, or Cl-1,4-BDC.

[0026] According to the invention, during step a) a base such as sodium hydroxide, piperazine or urea can be added.

[0027] Preferably, the metal sulfate used in step a) is Al2(SO4)3·16H2O, and in step a) preferably urea is added to the dispersion.

[0028] Preferably, the metal chlorate used in step a) is FeCl3·6H2O.

[0029] Preferably, step b) is maintained for 8 hours and 48 hours, and in step e) the dispersion is heated to a temperature of up to 130° C. for 1 to 4 hours under vigorous mechanical stirring.

[0030] Another object of the present invention relates to MOFs belonging to the MIL-53 family selected from MIL-53(Al), MIL-53(Al)-NH, MIL-53(Al)-NO, MIL-53(Al)-OH, MIL-53(Fe) and MIL-53(Cr), prepared according to the method as described above, without the use of DMF and without the need for a calcination step.

[0031] Particle size is assessed by imaging, preferably by SEM microscopy.

[0032] The invention also relates to the use of MOFs as described within the scope of the present invention for separations (gases, steam, etc.); in particular for CO2 capture (post-combustion, pre-combustion, or biogas); separation of aromatic substances (xylenes), aliphatic substances (branched alkanes); capture of organic volatile compounds; water-alcohol purification; desalination; materials for batteries; catalysis, such as the dehydrogenation of alcohols, or for the adsorption and conversion of small molecules (CO2, CH4, NH3, etc.), when the MOFs are combined with or doped with co-catalysts; waste heat management, for example by adsorption flexibility compensation; and detection; separation or controlled storage / release by stimuli, such as pressure, electric current, microwave irradiation, and magnetic fields.

[0033] Within the scope of the present invention, the BET specific surface area as well as the pore volume were determined by N adsorption method, in particular using a Micromeritics® TriStar instrument, based on the N adsorption-desorption isotherm at −196° C. (77 K).

[0034] Advantageously, a degassing step (i.e. heating under vacuum) can be carried out for sample preparation before the adsorption isotherm measurement, which may follow step f) described below.

[0035] The present invention is also described in detail below, in which the experimental part describes some embodiments in detail using examples that are provided merely as illustrations and should not be considered limiting, and in the following part, the drawings are briefly described. [Brief explanation of the drawings]

[0036] [Figure 1] Figure 1 shows the FTIR spectra of MIL-53(Al) (synthesized using the SO4 salt) and its activated form compared to the free ligand.

[0037] [Figure 2] Figure 2 shows the FTIR spectra of MIL-53(Al)-NO2 (synthesized using SO4 salt) and its activated form compared to the free ligand.

[0038] [Figure 3] FIG. 3 shows the FTIR spectra of MIL-53(Al)-NH2 (synthesized using SO4 salt) and its activated form in comparison with the free ligand.

[0039] [Figure 4] Figure 4 shows comparative powder X-ray diffraction diagrams (PXRD plots) of MIL-53-(Al) synthesized from the SO salt. The sample washed with DMSO and then dried at 100 °C is present primarily in the narrow pore (np) configuration, as opposed to the large pore (lp) configuration.

[0040] [Figure 5] Figure 5 shows a comparative FTIR plot of MIL-53-(Al) synthesized from the SO4 salt. Washing with DMSO followed by drying at 100 °C resulted in a MIL-53 sample with no ligands in the pores.

[0041] [Figure 6] FIG. 6 shows comparative PXRD plots of MIL-53-(Al) between the unactivated and activated forms synthesized from the chloride salt.

[0042] [Figure 7] FIG. 7 shows comparative PXRD plots of the unactivated and activated forms of MIL-53-(Al)-NO2 synthesized from the chloride salt.

[0043] [Figure 8] FIG. 8 shows comparative PXRD plots of the unactivated and activated forms of MIL-53-(Al)—NH 2 synthesized from the chloride salt.

[0044] [Figure 9] FIG. 9 shows the FTIR spectra of MIL-53(Al) and its activated form (synthesized from the chloride salt) compared to its ligand.

[0045] [Figure 10] FIG. 10 shows the FTIR spectra of MIL-53(Al)-NO2 and its activated form (synthesized from the chloride salt) compared to its ligand.

[0046] [Figure 11] FIG. 11 shows the FTIR spectra of MIL-53(Al)-NH2 and its activated form (synthesized from the chloride salt) in comparison with the ligand.

[0047] [Figure 12]FIG. 12 shows the thermogravimetric curves (ATG) of MIL-53(Al) (synthesized using SO4 salt) indicating the thermal stability of the structure before and after activation.

[0048] [Figure 13] FIG. 13 shows the thermogravimetric curves (ATG) of MIL-53(Al)-NO2 (synthesized using SO4 salt) before and after activation.

[0049] [Figure 14] FIG. 14 shows the thermogravimetric analysis curves (ATG) of MIL-53(Al)-NH2 (synthesized using SO4 salt) before and after activation.

[0050] [Figure 15] FIG. 15 shows the thermogravimetric curve (ATG) of MIL-53(Al) (synthesized using chloride salts).

[0051] [Figure 16] FIG. 16 shows the thermogravimetric curve (ATG) of MIL-53(Al)-NO2 (synthesized using chloride salts).

[0052] [Figure 17] FIG. 17 shows the thermogravimetric curve (ATG) of MIL-53(Al)—NH 2 (synthesized using chloride salt).

[0053] [Figure 18] Figure 18 shows the 77 K N isotherm of MIL-53(Al) synthesized using chloride salts. Activation by calcination produced samples with slightly smaller surfaces than activation by DMSO washing.

[0054] [Figure 19] FIG. 19 shows a comparative powder X-ray diffraction diagram (PXRD plot) of MIL-53(Fe)—Cl.

[0055] [Figure 20]FIG. 20 shows the FTIR spectra of MIL-53(Fe)—Cl and its activated form compared to the free ligand.

[0056] [Figure 21] FIG. 21 shows the thermogravimetric analysis curve (TGA) of MIL-53(Fe)—Cl. DETAILED DESCRIPTION OF THE INVENTION

[0057] Experimental Part Materials and Methods The reagents used were marketed by Alfa Aesar® and were used without further purification.

[0058] device PXRD: Powder X-ray diffraction (PXRD) data were collected using a Bruker® D8 Advance high-throughput diffractometer operated in transmission mode and equipped with a focusing Goebel mirror. The X-ray source was Cu-Kα radiation (λ=1.5418 Å).

[0059] Adsorption measurement All nitrogen porosimetry data were collected on a Micromeritics® TriStar instrument at 77 K. N2 and CO2 isotherms were recorded on a Micromeritics® Triflex instrument at 298 K. In all cases, measurements were recorded using ultra-high purity gases (grade ≥ 4.8). Prior to adsorption measurements, all samples were degassed at temperature (180-200 °C) for 8 h. Degassing was performed in a single step using a Micromeritics® SmartVacPrep degassing unit: vacuum was applied at 180-200 °C on the degassing port (P = 10 -6 mbar), and the degassing rate was <2 μbar / min.

[0060] TGA: TGA data were collected on a Mettler Toledo® TGA / DSC 2, STAR system at a heating rate of 5° C. / min under flowing oxygen.

[0061] FTIR: Infrared spectra were measured using a ThermoFisher™ Nicolet iS5 FTIR spectrometer.

[0062] Observation of the surface topography of the samples was carried out by scanning electron microscopy (SEM) using an FEI Magellan 400™.

[0063] Particle size distribution was performed by SEM and particle size measurements were performed using ImageJ™ software.

[0064] Within the scope of the present invention, mass percentages expressed in % w / w are used in the preparation and define the mass percentage of the component considered relative to the total mass of the considered object, such as a mixture, a material (such as a composite material), a membrane, etc. [Example]

[0065] Part 1: Compositing The synthesis of MIL-53(Al) and its derivatives was optimized using various metal salts, such as AlCl3·6H2O, Al2(SO4)3·16-18H2O, Al(OH)(CH3COO)2·xH2O, Al(OH)3, and NaAlO2, in the presence of various bases (NaOH, urea). Sulfate and chloride salts are the reagents of choice for obtaining MIL-53(Al) MOFs. The synthesis methods for MIL-53 MOFs using these sulfate salts (Examples 1-3) and chloride salts (Examples 4-6) are described below.

[0066] Example 1:

[0067] Preparation of MIL-53(Al)

[0068] MIL-53(Al) was synthesized using the reflux method. 100 mmol (66.6 g) of Al2(SO4)3·16H2O, 100 mmol (16.6 g) of 1,4-BDC (CAS: 100-21-0), and 100 mmol (6.0 g) of urea were dispersed in 200 ml of water in a 500 ml flask. The mixture was heated to reflux at 120 °C and maintained at reflux for 12 h. After the reaction mixture was cooled to ambient temperature, the colorless powder was filtered and washed with 80 ml of water. The sample was then dried overnight in air. The as-synthesized product contained free 1,4-BDC. Free 1,4-BDC was removed from the sample by washing with dimethyl sulfoxide (DMSO).

[0069] Activation of MIL-53(Al)

[0070] The synthesized MIL-53(Al) powder (22.5 g) was suspended in 250 ml of DMSO in a 500 ml flask. The mixture was then heated to 120 °C under continuous stirring and maintained under these conditions for approximately 2 hours. After cooling to 50 °C, the suspension was centrifuged and washed with ethanol (70 ml) and then with water (100 ml). The product was then dried in an oven at 100 °C. The mass of the isolated product is 18.5 g.

[0071] Alternatively, activation can be carried out by calcining MIL-53(Al) in air at 330° C. for 36 hours. These reaction conditions for activation by calcination at high temperatures are not very compatible with industrial scale implementation.

[0072] Example 2: (outside the scope of this invention)

[0073] Preparation of MIL-53(Al)-NO

[0074] The synthesis was carried out using the reflux method. 100 mmol (66.6 g) of Al2(SO4)3·16H2O, 100 mmol (21.1 g) of nitro-terephthalic acid (NO2-1,4-BDC, CAS: 610-29-7), and 100 mmol (6.0 g) of urea were dispersed in 200 ml of water in a 500 ml flask. The mixture was then refluxed at 120 °C and maintained at reflux for 12 h. After the reaction mixture was cooled to ambient temperature, the colorless powder was filtered and washed with 80 ml of water. The sample was then dried in air (overnight). The as-synthesized product contained free nitro-terephthalic acid, which was removed from the sample by washing with ethanol (EtOH).

[0075] Activation of MIL-53(Al)-NO2

[0076] The synthesized powder (26.5 g) was suspended in 250 ml of EtOH in a 500 ml flask. The mixture was then heated to 100 °C under continuous stirring and maintained under these conditions for approximately 4 hours. After cooling to 50 °C, the suspension was filtered and then rinsed with ethanol (60 ml). The product was then dried in an oven at 100 °C. The mass of the isolated product is 22.5 g.

[0077] Example 3:

[0078] Preparation of MIL-53(Al)-NH

[0079] The synthesis was carried out using the reflux method. 100 mmol (66.6 g) of Al2(SO4)3·16H2O, 100 mmol (18.1 g) of 2-amino-terephthalic acid (NH2-1,4-BDC, CAS: 10312-55-7), and 100 mmol (6.0 g) of urea were dispersed in 200 ml of water in a 500 ml flask. The mixture was then refluxed at 120 °C and maintained at reflux for 12 hours. After the reaction mixture was cooled to room temperature, the colorless powder was filtered and washed with 80 ml of water. The sample was then air-dried overnight. The as-synthesized product contained free 2-amino-terephthalic acid 1,4-BDC. Free 2-amino-terephthalic acid was removed from the sample by washing with dimethyl sulfoxide (DMSO).

[0080] Activation of MIL-53(Al)-NH2

[0081] The synthesized powder (25.5 g) was suspended in 250 ml of DMSO in a 500 ml flask. The mixture was then heated to 120°C under continuous stirring and maintained under these conditions for approximately 2 hours. After cooling to 50°C, the suspension was centrifuged and then washed with ethanol (70 ml) and then with water (100 ml). The product was then dried in an oven at 100°C. The mass of the isolated product was 19.0 g.

[0082] Example 4:

[0083] Preparation of MIL-53(Al)

[0084] MIL-53(Al) was synthesized using the reflux method. 150 mmol (36.15 g) of AlCl3·6H2O was dissolved in 260 ml of water in a 500 ml flask, and the solution was heated to 100 °C. Next, 125 mmol (20.75 g) of 1,4-BDC dissolved in 65 ml of 2 M NaOH was added to the flask under stirring. The mixture was then refluxed at 120 °C for 12 h. The colorless gel was then filtered and washed with 200 ml of water. The sample was then air-dried overnight. The mass of the isolated product was 23.0 g. The as-synthesized product contained free 1,4-BDC. Free 1,4-BDC was removed from the sample by washing with dimethyl sulfoxide (DMSO).

[0085] Activation of MIL-53(Al)

[0086] The synthesized powder (23.0 g) was suspended in 250 ml of DMSO in a 500 ml flask. The mixture was then heated to 120°C under continuous stirring and maintained under these conditions for approximately 2 hours. After cooling to 50°C, the suspension was centrifuged and then washed with ethanol (70 ml) and then with water (100 ml). The product was then dried in an oven at 100°C. The mass of the isolated product is 17.5 g.

[0087] Alternatively, activation may be achieved by calcination. The synthesized MIL-53(Al) powder was finely ground and well spread on a watch glass. The watch glass was then placed in a programmable oven. The sample was heated to 330°C (2 h) and maintained at 330°C for 36 h. After cooling to ambient temperature, the powder was collected and characterized by PXRD, TGA, and IR.

[0088] Example 5: (outside the scope of this invention)

[0089] Preparation of MIL-53(Al)-NO

[0090] The synthesis was carried out using the reflux method. 100 mmol (66.6 g) of AlCl3·6H2O was dissolved in 250 ml of water in a 500 ml flask, and the solution was heated to 100 °C. Then, 125 mmol (26.39 g) of nitro-terephthalic acid dissolved in 65 ml of 2 M NaOH (in a beaker) was added to the flask under stirring. An additional 20 ml of water was added to rinse the beaker. The mixture was then refluxed at 120 °C for 12 hours. The colorless solid was then filtered, washed with 150 ml of water, and rinsed with 50 ml of ethanol. The sample was then air-dried overnight. The mass of the isolated product was 26.0 g. The as-synthesized product contained free nitro-terephthalic acid, which was removed from the sample by washing with ethanol (EtOH).

[0091] Activation of MIL-53(Al)-NO2

[0092] The synthesized powder was pulverized and placed in a 500 ml flask. 250 ml of ethanol was added. The product was refluxed at 100°C for 10 hours, hot filtered (approximately 60°C), and washed with 40 ml of warm ethanol. The mass of the isolated product was 24.25 g.

[0093] Note: In some cases, the sample may contain traces of free ligand after the first wash. In this case, another wash with 150 ml of ethanol (100°C, 5 h) is required.

[0094] Example 6:

[0095] Preparation of MIL-53(Al)-NH

[0096] The synthesis was carried out using the reflux method. 150 mmol (36.15 g) of AlCl3·6H2O was dissolved in 200 ml of water in a 500 ml flask, and the solution was heated to 100 °C. Next, 125 mmol (22.64 g) of 2-amino-terephthalic acid (NH2-1,4-BDC, CAS: 10312-55-7) dissolved in 120 ml of 2 M NaOH (in a beaker) was added to the flask under stirring. 30 ml of water was added to rinse the beaker. The mixture was then refluxed at 120 °C for 12 hours. The yellowish solid was then filtered, washed with 200 ml of water, and rinsed with 30 ml of ethanol. The sample was then air-dried overnight. The mass of the isolated product was 19.0 g. The as-synthesized product contained 2-amino-terephthalic acid NH2-1,4-BDC. Free 2-amino-terephthalic acid was removed from the samples by washing with dimethyl sulfoxide (DMSO).

[0097] Activation of MIL-53(Al)-NH2

[0098] The powder thus synthesized was pulverized and placed in a 500 ml flask. 250 ml of DMSO was added. The mixture was refluxed at 120°C for 2 hours. After cooling to 50°C, the suspension was centrifuged and then washed with ethanol (70 ml) and then with water (100 ml). The product was then dried in an oven at 100°C. The mass of the isolated product was 16.2 g.

[0099] Example 7:

[0100] Preparation of MIL-53(Fe)-Cl

[0101] The synthesis was carried out using the reflux method. 15 mmol (4.10 g) of FeCl3·6H2O and 15 mmol (3.00 g) of 2-chloroterephthalic acid (Cl-1,4-BDC, CAS: 1967-31-3) were dissolved in 120 ml of water in a 250 ml flask. The mixture was then refluxed for 48 hours. The resulting colorless solid was then filtered and washed with 80 ml of water. The sample was then air-dried (overnight). The mass of the isolated product was 3.4 g. The as-synthesized product contained 2-amino-terephthalic acid 1,4-BDC. Free 2-amino-terephthalic acid was removed from the sample by washing with dimethyl sulfoxide (DMSO).

[0102] Activation of MIL-53(Fe)-Cl

[0103] The powder thus synthesized was pulverized and placed in a 100 ml flask. 50 ml of DMSO was added. The mixture was refluxed at 120 °C for 2 hours. After cooling to 50 °C, the suspension was centrifuged and then washed with ethanol (20 ml) and then with water (15 ml). The product was then dried in an oven at 100 °C. The mass of the isolated product was 3.0 g.

[0104] Part 2: Analysis and Results

[0105] Comparison of the FTIR and PXRD spectra in Figures 1 to 11 shows that activation makes it possible to remove all of the free ligands that did not react in the synthesis of the MOF.

[0106] Comparison of the thermogravimetric analysis (TGA) spectra in Figures 12-17 also shows that activation makes it possible to remove all of the free ligands that did not react in the synthesis of MOE.

[0107] The gas absorption spectra shown in Figure 18 indicate that activation by calcination produces MIE-53(Al) MOFs with slightly smaller BET surfaces than activation by washing with DMSO.

[0108] References The following table lists the references mentioned above in the text.

[0109] [Table 1]

[0110] [Table 2]

[0111] [Table 3]

[0112] [Table 4]

[0113] [Table 5]

[0114] [Table 6]

[0115] [Table 7]

Claims

1. A method for producing MOFs, the MOF being a structured metal-organic compound comprising a two- or three-dimensional porous network of inorganic matter connected by multidentate chelating ligands bound to multiple metal centers, the multidentate chelating ligands comprising: C containing at least one carboxylic acid function selected from ligands containing linear alkyl chains without unsaturation and ligands containing carbon chains containing at least one unsaturation ４ -C ２４ Aliphatic ligands; C containing at least one carboxylic acid function, preferably benzyl or naphthyl di-, tri- or tetracarboxylate ５ -C ２４ Heteroaromatic and aromatic ligands, and -NH ２ , —OH, —CH ３ , -OCH ３ , -NO ２ , -CF ３ , -COOH, -SO ３ said aromatic or heteroaromatic ligand optionally bearing a group selected from -H, -SH on at least one aromatic ring; and selected from the group comprising: The method comprises the following steps: a) dispersing molecules of a polydentate chelating ligand and at least one metal salt, preferably at least one metal salt selected from metal sulfates and metal chlorates, preferably aluminum sulfate, in water; b) optionally heating the dispersion obtained in a) at ambient pressure and maintaining the dispersion at a temperature of 50-150°C for a time period of 10 minutes to 96 hours; c) returning to ambient temperature, filtering and washing the solid obtained with water; d) drying the solid obtained in c); e) dispersing the solid obtained in d) in a solution containing DMSO under stirring at a temperature of 150°C or less for a period of 30 minutes to 15 hours; A method for producing an MOF, comprising:

2. 2. The method according to claim 1, wherein the metal center comprises at least one metal selected from Cu, Zn, Ca, Mg, Ti, Zr, In, Ga, V, Cr, Mn, Fe, and Al, and preferably the metal is a metal ion selected from at least one metal ion of Fe, Al, Cr, and V.

3. 3. The method according to claim 1 or 2, wherein the MOF produced according to the method of the present invention is selected from MIL-53, MIL-68, MIL-69, MIL-101, MIP-206 and DUT-7.

4. 4. The process according to claim 1, wherein the MOF is selected from the class of MIL-53 containing metal ions in the oxidation state +3 of a metal selected from Cr, Al, Fe, V, Ga and In, and the aromatic ligand is benzene-1,4-dicarboxylic acid or a derivative thereof.

5. The benzene-1,4-dicarboxylic acid derivative is —NH ２ , —OH and —NO ２ The method according to claim 4, wherein the aromatic ring is substituted with at least one group selected from the group consisting of:

6. The metal sulfate used in step a) is Al ２ (SO ４ ) ３ ・16H ２ 6. The process according to any one of claims 1 to 5, wherein in step a) preferably urea is added to the dispersion.

7. The metal chlorate used in step a) is FeCl ３ ・6H ２ The method according to any one of claims 1 to 5, wherein O is O.

8. 8. The method of any one of claims 1 to 7, wherein step b) is maintained for 8 hours and 48 hours, and in step e) the dispersion is heated to a temperature of up to 130°C under mechanical stirring for 1 to 4 hours.

9. MIL-53(Al), MIL-53(Al)-NH, prepared according to the method as claimed in any one of claims 1 to 8 without using DMF and without the need for a calcination step. ２ , MIL-53(Al)-NO ２ , MOFs belonging to the MIL-53 class selected from MIL-53(Al)-OH, MIL-53(Fe) and MIL-53(Cr).

10. 10. Use of the MOF according to claim 9, comprising the steps of: separation; ２ separation of aromatics, aliphatics; capture of organic volatile compounds; water-alcohol purification; desalination; battery materials; catalysis such as dehydrogenation of alcohols; for adsorption and conversion of small molecules; management of waste heat, e.g., by adsorption compensation; detection; and use of MOFs for separation or controlled storage / release by stimuli such as pressure, electric current, microwave irradiation and magnetic fields.

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