Process for obtaining metal-organic materials with structure type MIL-101 (Cr) and MIL-101-Cr-MX+

Abstract

The present invention relates to a process for obtaining materials with Metal Organic atomic structure and called MOF (MOF: Metal Organic Framework) type MIL-101 (Cr) and MIL-101-Cr-M.sup.X+ (MIL: Material from Institute Lavoisier), where M.sup.X+ can be any metal cation, such as Mg.sup.2+, Al.sup.3+ or Ti.sup.4+, using for its synthesis metal epoxides and alkoxides, avoiding the use of hydrofluoric acid (HF) or bases as synthesis controlling agents. The process of the present invention for the preparation of materials MOF MIL-101 (Cr) and MOF MIL-101-Cr-M.sup.X+ where M.sup.X+ can be any metal cation, such as Mg.sup.2+, Al.sup.3+ or Ti.sup.4+, consisting of: a) Synthesizing MOF MIL-101 (Cr) with epoxides, or Synthesizing MOF MIL-101-Cr-M.sup.X+ with metal alkoxides; and b) Purifying the synthesized MOF. in order to obtain 100% pure materials, with a controlled mesoporosity associated with a hysteresis P/P.sub.0 from 0.7 to 0.99, BET surface area from 2,500 to 3,500 m.sup.2/g, pore volume from 1.1 to 2.2 cm.sup.3/g, and pore diameter from 15 to 55 nm.

Claims

1. A process for obtaining a metal-organic framework of chromium(III) terephthalate (MIL-101-Cr) or a metal-organic framework of chromium(III) terephthalate with an additional metal ion M.sup.X+ (MIL-101-Cr-M.sup.X+), consisting of: a) Synthesizing the MIL-101-Cr with epoxides, or Synthesizing the MIL-101-Cr M.sup.X+ with metal alkoxides, where M.sup.X+ is any metal cation; and b) Purifying the synthesized MIL-101-Cr or MIL-101-Cr-M.sup.X+; in order to obtain 100% pure materials with controlled mesoporosity associated with a hysteresis P/P.sub.0 from 0.7 to 0.99, BET surface area from 2,500 to 3,500 m.sup.2/g, pore volume from 1.1 to 2.2 cm.sup.3/g, and pore diameter from 15 to 55 nm.

2. The process of claim 1, wherein step a) for synthesizing MIL-101-Cr comprises: adding water to a mixing tank, and starting constant stirring at room temperature; adding terephthalic acid, and stirring 5-15 minutes; adding a chromium salt, maintaining stirring for 10 to 30 minutes, and applying pulses with an ultrasound probe with 75 to 85% amplitude for a time of 4 to 8 minutes, to form a solution; adding an epoxide, to the solution and stirring for 5 to 15 minutes to form a final solution; pouring the final solution in to a reactor and closing the reactor to start hydrothermal treatment for 20 to 28 hours, at 170-190° C., 150 to 250 rpm and at autogenous pressure of 160 to 200 psi; and allowing the reactor to cool to room temperature and recovering a final reaction mixture.

3. The process of claim 1, wherein step a) for synthesizing MIL-101-Cr-M.sup.X+ consists of: adding water to a mixing tank and initiating constant stirring at room temperature; adding a chromium salt and terephthalic acid, and stirring for 5 to 15 minutes and applying pulses with an ultrasound probe with 75 to 85% amplitude for a time of 4 to 8 minutes; adding a metal alkoxide and dissolving while maintaining stirring for 5 to 15 minutes, applying pulses with an ultrasound probe with 75 to 85% amplitude for a time of 4 to 8 minutes to form a final solution; pouring the final solution in a reactor and closing the reactor to start hydrothermal treatment for 20 to 28 hours, at 170-190° C. with no stirring and at autogenous pressure; and allowing the reactor to cool and recovering a sample.

4. The process of claim 1, wherein step a) provides a yield of 95 to 98% weight.

5. The process of claim 1, wherein step b) comprises: performing a first washing by adding 25 to 250 ml of acetone to the synthesized MIL-101-Cr or MIL-101-Cr-M.sup.X+ to provide a mixture comprising liquid and MIL-101-Cr or MIL-101-Cr-M.sup.X+ as suspension; stirring the mixture for 30 to 90 minutes, then filtering the mixture to recover a solid; subjecting the recovered solid to a second washing with the same characteristics as the first wash, and filtering again to recover a powder; and drying the recovered powder at 100-140° C. for 10 to 14 hours.

6. The process of claim 1, wherein M.sup.X+ is selected from Mg.sup.2+, Al.sup.3+ and Ti.sup.4+.

7. The process of claim 2, wherein the stirring step further comprises applying pulses with an ultrasound probe with 75 to 85% amplitude for a time of 4 to 8 minutes.

8. The process of claim 2, wherein the chromium salt is Cr(NO.sub.3).sub.3.9H.sub.2O.

9. The process of claim 2, wherein the epoxide is propylene oxide.

10. The process of claim 2, wherein the hydrothermal treatment in the reactor is conducted for 22 to 26 hours at 175-185° C., 175-225 rpm and autogenous pressure of 170-190 psi.

11. The process of claim 3, wherein the chromium salt is Cr(NO.sub.3).sub.3.9H.sub.2O.

12. The process of claim 3, wherein the metal alkoxide is Mg(OCH.sub.2CH.sub.3).sub.2.

13. The process of claim 3, wherein the hydrothermal treatment in the reactor is conducted for 22 to 26 hours at 175-185° C. without stirring and at autogenous pressure.

14. The process of claim 2, wherein step b) comprises: performing a first washing by adding 175 to 225 ml of acetone to the synthesized MIL-101-Cr.sup.+ to provide a mixture comprising liquid and MIL-101-Cr as suspension; stirring the mixture for 30 to 90 minutes, then filtering the mixture to recover a solid; subjecting the recovered solid to a second washing with the same characteristics as the first wash, and filtering again to recover a powder; and drying the recovered powder at 100-140° C. for 10 to 14 hours.

15. The process of claim 3, wherein step b) comprises: performing a first washing by adding 35 to 65 ml of acetone to the synthesized MIL-101-Cr-M.sup.X+ to provide a mixture comprising liquid and MIL-101-Cr-M.sup.X+ as suspension; stirring the mixture for 30 to 90 minutes, then filtering the mixture to recover a solid; subjecting the recovered solid to a second washing with the same characteristics as the first wash, and filtering again to recover a powder; and drying the recovered powder at 100-140° C. for 10 to 14 hours.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1. X-ray diffraction pattern of MOF material MIL-101-Cr synthesized with propylene oxide, Example 1.

(2) FIG. 2. N2 adsorption isotherm corresponding to MOF material MIL-101-Cr, synthesized with propylene oxide, Example 1.

(3) FIG. 3. X-ray diffraction pattern of MOF material MIL-101-Cr synthesized with propylene oxide, Example 2.

(4) FIG. 4. N2 adsorption isotherm corresponding to MOF material MIL-101-Cr synthesized with propylene oxide, Example 2.

(5) FIG. 5. X-ray diffraction pattern of MOF material MIL-101-Cr synthesized with propylene oxide, Example 3.

(6) FIG. 6. N2 adsorption isotherm corresponding to MOF material MIL-101-Cr synthesized with propylene oxide, Example 3.

(7) FIG. 7. X-ray diffraction pattern of MOF material MIL-101-Cr—Mg synthesized and functionalized with magnesium ethoxide, Example 4.

(8) FIG. 8. N2 adsorption isotherm corresponding to MOF material MIL-101-Cr—Mg synthesized and functionalized with magnesium ethoxide, Example 4.

(9) FIG. 9. MOF material MIL-101-Cr synthesized, powder material, as obtained in the synthesis, Example 1.

DETAILED DESCRIPTION

(10) The present invention relates to a process for obtaining materials with Metal Organic atomic structure and called MOF (Metal Organic Framework) type MIL-101-Cr and MIL-101-Cr-M.sup.X+ (MIL: Material from Institute Lavoisier), where M.sup.X+ can be any metal cation, such as Mg.sup.2+, Al.sup.3+ or Ti.sup.4+, using for its synthesis metal epoxides and alkoxides, avoiding the use of hydrofluoric acid (HF) or bases as synthesis controlling agents.

(11) By the synthesis process of the present invention are obtained materials such MOF MIL-101-Cr and MOF MIL-101-Cr-M.sup.X+, 100% pure, with controlled mesoporosity associated with a hysteresis P/P.sub.0 from 0.7 to 0.99, BET surface area from 2,500 to 3,500 m.sup.2/g, pore volume from 1.1 to 2.2 cm.sup.3/g, and pore diameter of 15 to 55 nm.

(12) Among epoxides employed by the present invention is propylene oxide, which is used as a proton scavenger agent and promotes the formation of materials type MOF MIL-101-Cr having high crystallinity and high specific area.

(13) Propylene oxide is used in the synthesis of metal oxides by sol-gel method. In the traditional sol-gel method is used as cation source a metal alkoxide, which is dissolved in alcohol and the hydrolysis is carried out in acidic or basic medium. Acid function is to control the hydrolysis rate, accelerating it by protonation of the oxygen and generate better leaving groups and thus takes place before it happens the condensation reaction of -M-OH-M species. It is well known that this synthesis method generates materials based on metal oxides with exceptional properties and can be considered a “custom design” method. However, the big problem is that the metal alkoxides are very sensitive to moisture, so its management must be very careful for obtaining the expected and reproducible results.

(14) However, in the case of the present invention, the reaction system is much more complex, since in addition to the formation of metal hydroxides clusters, in this case Cr(OH).sub.x, these should be subsequently reacted with an aromatic dicarboxylic acid as an organic binder, preferably terephthalic acid (H.sub.2BDC), through the carboxyl groups, under hydrothermal conditions, 180° C. and autogenous pressure of 180 psi.

(15) In the present invention for the synthesis of MOF MIL-101-Cr having high crystallinity and without the use of hydrofluoric acid (HF) or a base such as tetramethylammonium hydroxide (TMAOH), it state that the epoxide plays a crucial role in forming clusters Cr(OH).sub.x of size and shape suitable to react with the carboxyl groups, COON, of aromatic dicarboxylic acid, preferably terephthalic acid (H.sub.2BDC). Epoxide act as proton scavenger during the cluster formation and its reaction with aromatic dicarboxylic acid generates rigid and highly porous structures. The fact that the reaction between the clusters of Cr(OH).sub.x and the aromatic dicarboxylic acid, preferably terephthalic acid (H.sub.2BDC) is carried out under high temperature, 180° C. and hydrothermal conditions to self-generated pressure, is indicative that the reaction between the inorganic cluster Cr(OH).sub.x and the organic binder, preferably terephthalic acid (H.sub.2BDC) is difficult. Therefore, addition of the epoxide provides said reaction to give a material of high crystallinity and high surface area, such as that shown in FIGS. 1 to 8, BET area of at least 2,800 m.sup.2/g.

(16) However, the present invention employs metal alkoxides such as Mg(O—CH.sub.2—CH.sub.3)2, to incorporate from synthesis metal cations M.sup.X+, such as Mg.sup.2+, Al.sup.3+ or Ti.sup.4+, within the structure of materials type MOF MIL-101-Cr. This allows incorporate cations, such as Mg, Si, Al, Ti or others, so that remain incorporated in the atomic structure of MOF in orderly manner and highly dispersed, thereby obtaining functionalized materials according to the final application of the material.

(17) In the incorporation of metal cations from the synthesis, metal alkoxides M-OR are used, in which in a very similar way to epoxides, oxygen is protonated and M-OH-M and an alcohol ROH is formed. This causes the cations present in the alkoxide react and incorporate to CrOH.sub.x clusters. The synthesis of MOF-101 MIL-Cr—Mg, generates a material having high crystallinity and high surface area with highly dispersed Mg.sup.2+. The diffraction pattern of this material no reveals the presence of the phase Mg(OH).sub.2 such as that shown in FIG. 7. This material has a high surface area, such as that shown in FIG. 8, of 2800 m.sup.2/g.

(18) The original synthesis of MOF-101 MIL-Cr consist of the hydrothermal reaction of 1,4-benzene dicarboxylate (H.sub.2BDC) with chromium nitrate (Cr/(NO.sub.3).sub.3.9H.sub.2O), hydrofluoric acid (HF) and water (H.sub.2O) for 8 hours at 220° C. producing a highly crystalline pure chromium terephthalate powder with formula Cr.sub.3F(H.sub.2O).sub.2O[(O.sub.2C)—C.sub.6H.sub.4—(CO.sub.2)].sub.3.nH.sub.2O (n=25), based on chemical analysis. The cubic structure of this material (8.9 nm) has several unprecedented features: a mesoporous zeotype architecture, very large cell volume (702 nm3), very large pore sizes (diameters of 2.9-3.4 nm, pore volumes of 12.7-20.6 nm3) and a record adsorption capacity (S.sub.Langmuir=5,600 to 6,200 m.sup.2/g) (O. I. Lebedev, et al. First Direct Imagen of Giant Pores of the Metal-Organic Framework MIL-101. Chem. Mater. 2005, 17, 6525-6527).

(19) The materials obtained by the present invention, with atomic Metal Organic structure MIL-101-Cr and MIL-101-Cr-M.sup.X+, where M.sup.X+ can be any metal cation, such as Mg.sup.2+, Al.sup.3+ or Ti.sup.4+, are a green fine powder, such as MOF MIL-101-Cr shown in FIG. 9, which was synthesized with propylene oxide.

(20) The process of the present invention for the preparation of materials MOF MIL-101-Cr and MOF MIL-101-Cr-M.sup.X+ where M.sup.X+ can be any metal cation, such as Me.sup.+, Al.sup.3+ or Ti.sup.4+, consisting of:

(21) a) Synthesizing MOF MIL-101-Cr with epoxides, or

(22) Synthesizing MOF MIL-101-Cr-M.sup.X+ with metal alkoxides; and

(23) b) Purifying synthesized MOF,

(24) in order to obtain 100% pure materials with controlled mesoporosity associated with a hysteresis P/P.sub.0 from 0.7 to 0.99, BET surface area from 2,500 to 3,500 m.sup.2/g, pore volume from 1.1 to 2.2 cm.sup.3/g, and pore diameter from 15-55 nm.

(25) Where:

(26) The synthesis of MOF MIL-101-Cr with epoxides comprising: adding water to a reactor, preferably demineralized and start constant agitation at room temperature; adding an aromatic dicarboxylic acid as organic binder, preferably terephthalic acid (H.sub.2BDC), and stirring for 5-15 minutes, preferably 8-12 minutes; applying pulses, preferably with an ultrasound probe with 75 to 85% amplitude for a time of 4 to 8 minutes, preferably 5 to 7 minutes, to improve the solubility of aromatic dicarboxylic acid used; adding a chromium salt, preferably chromium nitrate (Cr(NO.sub.3).sub.3.9H.sub.2O), maintaining stirring for 10 to 30 minutes, preferably for 15 to 25 minutes; applying pulses, preferably with an ultrasound probe with 75 to 85% amplitude for a time of 4 to 8 minutes, preferably 5 to 7 minutes, to the final solution; adding an epoxide as proton scavenger agent, preferably propylene oxide, to the solution and stirring for 5 to 15 minutes, preferably 8 to 12 minutes; pouring the final solution in the reactor and closing the reactor to start the hydrothermal treatment for 20 to 28 hours, at 170-190° C., 150 to 250 rpm and autogenous pressure of 160 to 200 psi, preferably for 22 to 26 hours at 175-185° C., 175-225 rpm and autogenous pressure of 170-190 psi; and allowing to cool the reactor to room temperature and recovering the final reaction mixture.

(27) in order to obtain a highly dispersed material having high crystallinity and high surface area, with low residue concentrations of raw materials remained unreacted, so it is important to carry out a purification process of synthesized MOF.

(28) The synthesis of MOF MIL-101-Cr-M.sup.X+ with metal alkoxides, consisting of: adding water to the reactor, preferably demineralized and initiate constant agitation at room temperature; adding a chromium salt, preferably chromium nitrate (Cr(NO.sub.3).sub.3.9H.sub.2O), and an aromatic dicarboxylic acid, preferably terephthalic acid (H.sub.2BDC), and stirring for 5 to 15 minutes, preferably 8 to 12 minutes; applying pulses, preferably with an ultrasound probe with 75 to 85% amplitude for a time of 4 to 8 minutes, preferably 5 to 7 minutes, to improve the solubility of the aromatic dicarboxylic acid used; adding a metal alkoxide, preferably magnesium ethoxide and dissolve maintaining stirring for 5 to 15 minutes, preferably 8 to 12 minutes; applying pulses, preferably with an ultrasound probe with 75 to 85% amplitude for a time of 4 to 8 minutes, preferably 5 to 7 minutes, to the final solution; pouring the final solution in the reactor and closing the reactor to start the hydrothermal treatment for 20 to 28 hours, at 170-190° C. with no stirring and autogenous pressure preferably for 22 to 26 hours at 175-185° C. without stirring and autogenous pressure; and allowing to cool the reactor and recover the sample.

(29) in order to obtain a highly dispersed material having high crystallinity and high surface area, with metal cation (M.sup.X+, such as Mg.sup.2+, Al.sup.3+ or Ti.sup.4+), with low residue concentrations of raw materials remained unreacted, so it is important to carry out a purification process of synthesized MOF.

(30) The synthesis processes of the present invention provide a yield of 95 to 98% weight.

(31) Waste of raw materials remained unreacted in synthesized MOF can not be identified by X-ray diffraction, due to its low concentration, so it is important to perform a purification process to achieve 100% purity of material.

(32) Purification of synthesized MOF comprises: performing a first washing adding 25 to 250 ml of acetone, preferably 175 to 225 ml when the synthesis is performed with epoxides and 35 to 65 ml when synthesis is performed with metal alkoxides, to the resulting synthesis mixture comprising liquid and MOF as suspension; stirring the mixture for 30 to 90 minutes, preferably 50 to 70 minutes, then filtering the mixture; subjecting the recovered green solid to a second washing with the same characteristics as the first wash, and filtering again; drying the recovered powder at 100-140° C. for 10 to 14 hours, preferably at 110-130° C. for 11 to 13 hours.

(33) in order to obtain a pure 100% free waste material having high crystallinity and high surface area, with highly dispersed metal cation (M.sup.X+, such as Mg.sup.2+, Al.sup.3+ or Ti.sup.4+).

(34) By the synthesis process of the present invention, materials type MOF MIL-101-Cr and MOF MIL-101-Cr-M.sup.X+ 100% pure, with controlled mesoporosity associated with a hysteresis P/P.sub.0 from 0.7 to 0.99, BET surface area from 2,500 to 3,500 m.sup.2/g, pore volume from 1.1 to 2.2 cm.sup.3/g, and pore diameter form 15 to 55 nm.

(35) In this regard it should be noted that the mesoporosity is a very important property in catalytic and adsorbent materials, so it is very important to control.

(36) In the present invention, the mesoporosity is a function of the synthesis controlling agents: metal epoxides and alkoxides, critical property to custom design materials.

EXAMPLES

(37) The following some practical examples for a better understanding of the present invention are described, without limiting its scope.

Example 1

(38) MOF Synthesis of MIL-101-Cr with Propylene Oxide.

(39) In a 1-liter beaker, 660 ml of demineralized water were added, constant magnetic stirring at room temperature was initiated. 22.174 g of terephthalic acid (H.sub.2BDC) were added and stirred for 10 minutes. Pulses with the ultrasound probe SONICS Vibra Cell with 80% amplitude was applied for an effective time of 6 minutes to improve the solubility of terephthalic acid. 52.879 g of chromium nitrate (Cr(NO.sub.3).sub.3.9H.sub.2O) was weighed, and added to the above solution while stirring for 20 minutes. Pulses with SONICS Vibra Cell ultrasound probe with 80% amplitude were applied for an effective time of 6 minutes at a final solution. 1.938 g of propylene oxide were added and the solution was stirred for 10 min. The final solution was poured into the 1-liter beaker of Parr reactor, which contains in its interior a Teflon beaker. The Parr reactor was closed to start the hydrothermal treatment for 24 hours at 180° C., 200 rpm and autogenous pressure. After the reaction, the reactor was allowed to cool to room temperature and the final reaction mixture was recovered.

(40) Purification of Synthesized MOF: Wash with Acetone.

(41) To the resulting synthesis mixture comprising liquid and MOF as suspension were added 200 ml of acetone. The mixture was stirred for one hour and then filtered and the recovered green solid was placed in a flask and were added 200 ml of acetone to a second washing and filtered again. The recovered powder was dried at 120° C. for 12 hours.

(42) FIGS. 1 and 2 show the X-ray diffraction pattern and the N2 adsorption isotherm respectively of MOF material MIL-101-Cr synthesized with propylene oxide, which show the following properties, according to BET method: surface area of 3,000 m.sup.2/g, pore volume of 1.269 cm.sup.3/g, and pore diameter of ≈50 nm.

(43) FIG. 9 shows the powder material obtained: MIL MOF-101 (Cr) synthesized with propylene oxide.

Example 2

(44) Synthesis of MOF MIL-101-Cr with Propylene Oxide.

(45) Following the same procedure of Example 1, the content of propylene oxide was increased to 3.08 g, keeping the amounts of water in 600 ml, H.sub.2BDC in 22.174 g Cr(NO.sub.3).sub.3.9H.sub.2O at 52.879 g.

(46) The reactant solution was poured into the 1-liter beaker of Parr reactor, which contains in its interior a Teflon beaker. The Parr reactor was closed to start the hydrothermal treatment for 24 hours at 180° C., 200 rpm and autogenous pressure. After the reaction, the reactor was allowed to cool to room temperature and the final reaction mixture was recovered.

(47) Purification of Synthesized MOF: Wash with Acetone.

(48) To the resulting synthesis mixture comprising liquid and MOF as suspension were added 200 ml of acetone. The mixture was stirred for one hour and then filtered and the recovered green solid was placed in a flask and were added 200 ml of acetone to a second washing and filtered again. The recovered powder was dried at 120° C. for 12 hours.

(49) FIGS. 3 and 4 show the X-ray diffraction pattern and the N2 adsorption isotherm respectively of MOF material MIL-101-Cr synthesized with propylene oxide, which present the following characteristics, according to the BET method: surface area of 3,121 m.sup.2/g, pore volume of 1.833 cm.sup.3/g, 10% more than in the case of Example 1, and pore diameter of ≈50 nm which is in the range of mesopores. It is to be noted that the adsorption isotherm, FIG. 4, reveals the presence of mesoporosity associated with a hysteresis P/P.sub.0 from 0.9 to 0.98.

(50) The powder obtained is similar to that shown in FIG. 9.

Example 3

(51) Synthesis of MOF MIL-101-Cr with Propylene Oxide.

(52) Following the same procedure of Example 1, the content of propylene oxide was increased to 4.11 g, keeping the amounts of water in 600 ml, H.sub.2BDC in 22.174 g, Cr(NO.sub.3).sub.3.9H.sub.2O in 52.879 g.

(53) The reactant solution was poured into the 1-liter beaker of Parr reactor, which contains in its interior a Teflon baker. The Parr reactor was closed to start the hydrothermal treatment for 24 hours at 180° C., 200 rpm and autogenous pressure. After the reaction, the reactor was allowed to cool to room temperature and the final reaction mixture was recovered.

(54) Purification of Synthesized MOF: Wash with Acetone.

(55) To the resulting synthesis mixture comprising liquid and MOF as suspension were added 200 ml of acetone. The mixture was stirred for 1 hour and then filtered and the recovered green solid was placed in a flask and were added 200 ml of acetone to a second washing and filtered again. The recovered powder was dried at 120° C. for 12 hours.

(56) FIGS. 5 and 6 show the X-ray diffraction pattern and N2 adsorption isotherm respectively, of MOF material MIL-101-Cr synthesized with propylene oxide, which presented the following characteristics, according to the BET method: surface area of 3,165 m.sup.2/g, pore volume of 2.045 cm.sup.3/g, 20% more porous than in the case of Example 1, and pore diameter of ≈20 nm. It is important to note that the adsorption isotherm, FIG. 6, reveals the presence of mesoporosity, associated with a much stronger hysteresis than that obtained in Example 2, P/P.sub.0 from 0.8 to 0.98 indicating that the mesoporosity is much more important in this material.

(57) The foregoing confirms that the property of mesoporosity is based on the content of propylene oxide, so it can be modulated according to the needs of the material application; that is, this feature is very important to custom design materials.

(58) The powder obtained is similar to that shown in FIG. 9.

Example 4

(59) Synthesis of MOF MIL-101-Cr—Mg with Magnesium Ethoxide (Mg(OCH.sub.2CH.sub.3).sub.2).

(60) In a 100 ml beaker, 50 ml of demineralized water were added, constant magnetic stirring at room temperature was initiated. 3.97 g of chromium nitrate (Cr(NO.sub.3).sub.3.9H.sub.2O) was weighed and added. 1.65 g of terephthalic acid (H.sub.2BDC) were weighed and added to the above solution under constant stirring for 10 minutes. Pulses with the SONICS Vibra Cell ultrasound probe with 80% amplitude was applied for an effective time of 6 minutes to improve the solubility of terephthalic acid. Finally, 0.36 g of magnesium ethoxide (Mg(OCH.sub.2CH.sub.3).sub.2) was added, and dissolved with stirring for 10 minutes. Pulses with Sonics Vibra Cell ultrasound probe with 80% amplitude were applied for an effective time of 6 minutes to final solution. The final solution was poured into the 100 milliliter beaker of Parr reactor, which contains in its interior a Teflon beaker. The Parr reactor was closed to start the hydrothermal treatment for 24 hours at 180° C. without stirring and autogenous pressure. After the reaction, the reactor was cooled and the sample was recovered.

(61) Purification of Synthesized MOF: Wash with Acetone.

(62) To the resulting synthesis mixture comprising liquid and MOF as suspension were added 50 ml of acetone. The mixture was stirred for one hour and then filtered and the recovered green solid was placed in a flask and were added 50 ml of acetone to a second washing and filtered again. The recovered powder was dried at 120° C. for 12 hours.

(63) FIGS. 7 and 8 show the X-ray diffraction pattern and the N2 adsorption isotherm respectively of MOF material MIL-101-Cr—Mg synthesized and functionalized with magnesium ethoxide (Mg(OCH.sub.2CH.sub.3).sub.2) which present the following characteristics, according to the BET method: surface area of 2,800 m.sup.2/g, pore volume of 1.269 cm.sup.3/g, and pore diameter of ≈50 nm. It is important to note that the adsorption isotherm, FIG. 8 shows the presence of mesoporosity, associated with a hysteresis P/P.sub.0 from 0.9 to 0.98 indicating that the mesoporous material has features comparable to those of the material obtained in Example 2.

(64) The powder obtained is similar to that shown in FIG. 9.