PREPARATION OF NEW ALDEHYDE AND/OR KETONE TRAPS AND FILTERS

Abstract

A method for preparing a nanoporous silica sol-gel matrix containing at least one amine reactant selected from hydroxylamine, methylhydroxylamine, tertbutylhydroxylamine, methoxyamine, tetraethylenepentamine, dicarboxylic acid dihydrazides, particularly adipic acid dihydrazide, and the salts thereof, said method including the following steps: a) synthesising a gel from tetramethoxysilane or from a mixture of tetramethoxysilane and another organosilicon precursor selected from among phenyltrimethoxysilane, phenyltriethoxysilane, a fluoroalkyltrimethoxysilane, a fluoroalkyltriethoxysilane, a chloroalkylmethoxysilane, a chloroalkylethoxysilane, an alkyltrimethoxysilane, an alkyltriethoxysilane, an aminopropyltriethoxysilane and the mixtures thereof, the synthesis being performed in an aqueous medium at a temperature ranging from 10 to 70° C. in the presence of at least one amine reactant selected from among hydroxylamine, methylhydroxylamine, tertbutylhydroxylamine, methoxyamine, dicarboxylic acid dihydrazides, particularly adipic acid dihydrazide, and the salts thereof; b) drying the gel obtained during step a) so as to obtain a sol-gel matrix containing at least one amine reactant.

Claims

1. A porous silicate sol-gel matrix comprising at least one aminic reagent selected from hydroxylamine, methylhydroxylamine, tert-butylhydroxylamine, methoxyamine, tetraethylenepentamine, and dicarboxylic acid dihydrazides, and salts thereof, wherein the sol-gel matrix is prepared by a process comprising the steps of: a) synthesizing a gel from tetramethoxysilane or a mixture of tetramethoxysilaneand another organosilicon precursor, selected from phenyltrimethoxysilane, phenyltriethoxysilane, fluoroalkyltrimethoxysilane, fluoroalkyltriethoxysilane, chloroalkylmethoxysilane, chloroalkylethoxysilane, alkyltrimethoxysilane, alkyltriethoxysilane, aminopropyltriethoxysilane and mixtures thereof, the synthesizing being carried out in an aqueous medium at a temperature of from 10 to 70° C. in the presence of at least one aminic reagent selected from hydroxylamine, methylhydroxylamine, tert-butylhydroxylamine, methoxyamine and dicarboxylic acid dihydrazides, and salts thereof, and b) drying the gel obtained in step a) to give a sol-gel matrix comprising at least one aminic reagent, and wherein the sol-gel matrix has a specific adsorption surface area of 15±2 m.sup.2.Math.g.sup.−1 to 900±100 m.sup.2.Math.g.sup.−1, preferably of 150±20 m.sup.2.Math.g.sup.−1 to 900±100 m.sup.2.Math.g.sup.−1.

2. The sol-gel matrix as claimed in claim 1, wherein the sol-gel matrix has a proportion of micropores of more than 50% and a balance to 100% corresponding to the proportion of mesopores.

3. The sol-gel matrix as claimed in claim 2, wherein the micropores have diameters of between 0.8 to 2 nm, with a maximum centered around 1.1±0.1 nm.

4. The sol-gel matrix as claimed in claim 2, wherein the sol-gel matrix has a specific adsorption surface area of 500±50 m.sup.2.Math.g.sup.−1 to 900±100 m.sup.2.Math.g.sup.−1.

5. The sol-gel matrix as claimed in claim 1, wherein the sol-gel matrix has a proportion of mesopores of more than 50% and a balance to 100% corresponding to the proportion of micropores.

6. The sol-gel matrix as claimed in claim 5, wherein the mesopores have diameters of between 3 and 6 nm, with a maximum centered around 4.9±0.1 nm.

7. The sol-gel matrix as claimed in claim 5, wherein the sol-gel matrix has a specific adsorption surface area of 15±2 m.sup.2.Math.g.sup.−1 to 400±40 m.sup.2.Math.g.sup.−1.

8. The sol-gel matrix as claimed in claim 1, wherein the at least one aminic reagent is selected from methylhydroxylamine, methoxyamine, adipic acid dihydrazide and salts thereof.

9. A method of trapping aldehydes and/or ketones which are present in air comprising contacting the porous silicate sol-gel matrix as claimed in claim 1 with the air so as to sequester the aldehydes and/or ketones in pores of said matrix.

10. The method as claimed in claim 9, wherein an air filter for abatement of aldhehydes and/or ketones comprises said matrix.

11. An aldehyde and/or ketone abatement filter, comprising a porous silicate sol-gel matrix as claimed in claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0050] FIG. 1: Curves of concentration as a function of time for a filter composed of the material of example 3 and exposed to formaldehyde: the “upstream” curve for the concentration of formaldehyde measured without filter, and the “downstream” curve for the concentration of formaldehyde measured after passage through.

[0051] FIG. 2: Difference between the “upstream” and “downstream” curves of FIG. 1, corresponding to the amount of formaldehyde trapped over time.

DETAILED DESCRIPTION

EXAMPLES

[0052] Abbreviations:

[0053] TMOS: tetramethoxysilane

[0054] Cl-TMOS: 3-chloropropyltrimethoxysilane

[0055] MeHA,HCl: methylhydroxyamine hydrochloride

[0056] CH3ONH2,HCl: methoxyamine hydrochloride

[0057] TEPA: tetraethylenepentamine

[0058] MeOH: methanol

[0059] I. Preparation and Analysis of Porous Sol-Gel Matrices

Example 1: TMOS Matrix Doped with Methylhydroxyamine

[0060] Reagents: MeHA,HCl (Sigma Aldrich, CAS number 4229-44-1, molar mass=83.52 g/mol, purity 98%), TMOS (CAS number: 681-84-5, molar mass=152.2 g/mol and density d=1.023 mg/cm.sup.−3). Plastic honeycomb mold with cylindrical wells 6 mm in diameter and 10 mm in depth.

[0061] 5M solution of MeHA,HCl with 6.264 g dissolved in 15 mL of H.sub.2O

[0062] V(TMOS)=7.993 mL

[0063] V(H.sub.2O)=23.083 mL

[0064] V(MeHA,HCl 5M)=5.92 mL (0.8M)

[0065] V(total)=37 mL

Procedure: In a 60 mL flask, 7.993 mL of TMOS are mixed with 23.083 mL of water with magnetic stirring. The mixture is stirred for 5 min and then the 5.92 mL of 5M aqueous solution of MeHA,HCl are added. The formation of two phases and a heating of the mixture are observed, the mixture becoming homogeneous over time. When the temperature of the mixture returns to ambient temperature, the mixture is poured into a honeycomb mold placed in a crystallizer. The mold is covered with an aluminum membrane and is placed in a desiccator equipped with a relative humidity indicator. Gelling takes place after 20 h. Three days after gelling, the aluminum membrane is replaced with a semipermeable membrane (AB-Gene Greiner one). The desiccator is flushed with a stream of inert gas (Ar or N2) at a rate of 300 mL/min, and drying is halted when the humidity indicator indicates between 0.5 to 2% relative humidity.

[0066] The dry granules obtained are transparent and pale yellow in color.

[0067] After drying, transparent sol gel granules of a pale yellow color are obtained, with dimensions close to cylinders 3 mm in diameter and 5 mm in length. The methylhydroxyamine content of the porous sol-gel matrix is 6.4 mol.Math.dm.sup.−3.

Example 2: TMOS/Cl-TMOS Matrix Doped with Methoxyamine

[0068] Reagents: CH3ONH2,HCl (Sigma Aldrich, CAS number 593-56-6, molar mass=83.52 g.Math.mol.sup.−1, purity 98%), TMOS (CAS number: 681-84-5, molar mass=152.2 g.Math.mol.sup.−1 and density d=1.023 mg.Math.cm.sup.−3), Cl-TMOS (CAS No.: 2530-87-2, purity 97%, molar mass=198.72 g.Math.mol.sup.−1 and density=1.09 g.Math.cm.sup.3), methanol (CH.sub.3OH, molar mass 32.04 g.Math.mol.sup.−1, density=0.792 g.Math.cm.sup.−3, purity 98%). Plastic honeycomb mold with cylindrical wells 6 mm in diameter and 10 mm in depth.

[0069] 5M solution of CH3ONH2,HCl with 2.506 g dissolved in 6 mL of H.sub.2O

[0070] V(TMOS)=9.182 mL

[0071] V (Cl-TMOS)=0.359 mL

[0072] V(MeOH)=20.589 mL

[0073] V(H2O)=0.950 mL

[0074] V(CH3ONH2,HCl 5M)=5.92 mL (0.8 M)

[0075] V(total)=37 mL

[0076] Procedure: In a 60 mL flask, 9.182 mL of TMOS, 0.359 mL of Cl-TMOS are mixed with 20.589 mL of MeOH with magnetic stirring. The mixture is stirred for 5 min, and then 0.95 mL of water and the 5.92 mL of 5M aqueous solution of CH3ONH2,HCl are added. The mixture is left with stirring for 7 days at ambient temperature and then is poured into a honeycomb mold placed in a crystallizer equipped with a relative humidity indicator. The mold is covered with an aluminum membrane and is placed in a desiccator equipped with a relative humidity indicator. Gelling takes place after 13 days. Three days after gelling, the aluminum membrane is replaced with a semipermeable membrane (AB-Gene Greiner one). The desiccator is flushed with a stream of inert gas (Ar or N.sub.2) at a rate of 300 mL/min, and drying is halted when the humidity indicator indicates between 0.5 to 2% relative humidity.

[0077] The dry granules obtained are translucent and pale yellow in color.

[0078] In the present example, the molar proportions of the reagents are TMOS/Cl-TMOS/MeOH/H.sub.2O/CH3ONH2,HCl=1/0.032/8.3/6.25/0.484. The CH3ONH2 content of the porous matrix is 6.4 mol.Math.dm.sup.−3.

Example 3: TMOS Matrix with Methoxyamine

[0079] Reagents: CH3ONH2,HCl (Sigma Aldrich, CAS number 593-56-6, molar mass=83.52 g.Math.mol.sup.−1, purity 98%), TMOS (CAS number: 681-84-5, molar mass=152.2 g.Math.mol.sup.−1 and density d=1.023 mg.Math.cm.sup.−3). Plastic honeycomb mold with cylindrical wells 6 mm in diameter and 10 mm in depth.

[0080] V(TMOS)=12.604 mL

[0081] V(H2O)=24.396 mL

[0082] CH3ONH2,HCl=2.52 g (0.815 M)

[0083] V(total)=37 mL

[0084] Procedure: 2.52 g of CH3ONH2,HCl is introduced into a 60 mL flask and 24.396 mL of water are added. The mixture is stirred until dissolution of the methoxyamine is complete. 12.064 mL of TMOS are added and the mixture is left with magnetic stirring for 6 h, after which the mixture is poured into a honeycomb mold placed in a crystallizer. The mold is covered with an aluminum membrane and the mold is placed in a desiccator equipped with a relative humidity indicator. Gelling sets in at between 72 and 96 h. The aluminum membrane is replaced with a semipermeable membrane and the desiccator is flushed with a stream of N2 at a rate of 300 mL/min, and drying is halted when the humidity indicator indicates between 0.5 to 2% relative humidity.

[0085] The dry granules obtained are white.

[0086] In the present example, the molar proportions of the reagents are TMOS/H2O/CH3ONH,HCl=1/16.16/0.353. The methoxyamine content of the porous matrix is 6.52 mol.Math.dm.sup.−3.

Example 4: TMOS Matrix Doped with Adipic Acid Dihydrazide

[0087] Reagents: Adipic acid dihydrazide (Sigma Aldrich, CAS number 1071-93-8, molar mass=174.2 g.Math.mol.sup.−1, purity 98%), TMOS (CAS number: 681-84-5, molar mass=152.2 g.Math.mol.sup.−1 and density d=1.023 mg.Math.cm.sup.−3). Plastic honeycomb mold with cylindrical wells 6 mm in diameter and 10 mm in depth.

[0088] V(TMOS)=12.37 mL

[0089] V(H.sub.2O)=24.65 mL

[0090] adipic acid dihydrazide=0.65 g (0.1M)

[0091] V(total)=37 mL

[0092] Procedure: 0.65 g of adipic acid dihydrazide is introduced into a 60 mL flask and 24.65 mL of water are added. The mixture is stirred until dissolution of the adipic acid dihydrazide is complete. 12.37 mL of TMOS are added and the mixture is left with magnetic stirring. Formation of two phases is observed. To accelerate the reaction, the flask is heated to 40° C. The mixture is left with stirring until the mixture becomes homogeneous (20 min). The mixture is poured into a honeycomb mold placed in a crystallizer. The mold is covered with an aluminum membrane and the mold is placed in a desiccator equipped with a relative humidity indicator. Gelling is rapid (35 min). After 3 days, the aluminum membrane is replaced with a semipermeable membrane and the desiccator is flushed with a stream of N2 at a rate of 300 mL/min, and drying is halted when the humidity indicator indicates between 0.5 to 2% relative humidity.

[0093] The dry granules obtained are white.

[0094] In the present example, the molar proportions of the reagents are TMOS/H.sub.2O/adipic acid dihydrazide=1/16.64/0.044. The adipic acid dihydrazide content of the porous matrix is 0.8 mol.Math.dm.sup.−3.

Example 5: TMOS Matrix Doped with Adipic Acid Dihydrazide

[0095] Reagents: Adipic acid dihydrazide (Sigma Aldrich, CAS number 1071-93-8, molar mass=174.2 g.Math.mol.sup.−1, purity 98%), TMOS (CAS number: 681-84-5, molar mass=152.2 g.Math.mol.sup.−1 and density d=1.023 mg.Math.cm.sup.−3). Plastic honeycomb mold with cylindrical wells 6 mm in diameter and 10 mm in depth.

[0096] V(TMOS)=12.37 mL

[0097] V(H20)=24.65 mL

[0098] Adipic acid dihydrazide=1.3 g (0.2M)

[0099] V(total)=37 mL

[0100] Procedure: 1.3 g of adipic acid dihydrazide are introduced into a 60 mL flask and 24.65 mL of water are added. The mixture is stirred until dissolution of the adipic acid dihydrazide is complete. 12.37 mL of TMOS are added and the mixture is left with magnetic stirring. Formation of two phases is observed. To accelerate the reaction, the flask is heated to 40° C. The mixture is left with stirring until the mixture becomes homogeneous (40 min). The mixture is poured into a honeycomb mold placed in a crystallizer. The mold is covered with an aluminum membrane and the mold is placed in a desiccator equipped with a relative humidity indicator. Gelling is rapid (43 min). After 3 days, the aluminum membrane is replaced with a semipermeable membrane and the desiccator is flushed with a stream of N2 at a rate of 300 mL/min, and drying is halted when the humidity indicator indicates between 0.5 to 2% relative humidity.

[0101] The dry granules obtained are transparent.

[0102] In the present example, the molar proportions of the reagents are TMOS/H2O/adipic acid dihydrazide=1/16.64/0.176. The adipic acid dihydrazide content of the porous matrix is 1.6 mol.Math.dm.sup.−3.

Example 6: TMOS Matrix Doped with Adipic Acid Dihydrazide and Methoxyamine

[0103] Reagents: Adipic acid dihydrazide (Sigma Aldrich, CAS number 1071-93-8, molar mass=174.2 g.Math.mol.sup.−1, purity 98%), CH3ONH2,HCl (Sigma Aldrich, CAS number 593-56-6, molar mass=83.52 g.Math.mol.sup.−1, purity 98%), TMOS (CAS number: 681-84-5, molar mass=152.2 g.Math.mol.sup.−1 and density d=1.023 mg.Math.cm.sup.−3), methanol (CH.sub.3OH, molar mass 32.04 g.Math.mol.sup.−1, density=0.792 g.Math.cm.sup.−3, purity 98%). Plastic honeycomb mold with cylindrical wells 6 mm in diameter and 10 mm in depth.

[0104] V(TMOS)=12.604 mL

[0105] V(H.sub.2O)=24.396 mL

[0106] Adipic acid dihydrazide=0.65 g (0.1 M)

[0107] CH3ONH2,HCl=1.855 g (0.6 M)

[0108] V(total)=37 mL

[0109] Procedure: 0.65 g of adipic acid dihydrazide and 1.855 g of CH3ONH2,HCl are introduced into a 60 mL flask and 24.65 mL of water are added. The mixture is stirred until dissolution of the two compounds is complete. 12.604 mL of TMOS are added and the mixture is left with magnetic stirring. Formation of two phases is observed and the mixture is left with stirring until the mixture becomes homogeneous. The mixture is poured into a honeycomb mold placed in a crystallizer. The mold is covered with an aluminum membrane and the mold is placed in a desiccator equipped with a relative humidity indicator. At the end of 3 days after gelling, the aluminum membrane is replaced with a semipermeable membrane and the desiccator is flushed with a stream of N2 at a rate of 300 mL/min. Drying is halted when the humidity indicator indicates between 0.5 to 2% relative humidity.

[0110] The dry granules obtained are transparent.

[0111] In the present example, the molar proportions of the reagents are TMOS/H2O/adipic acid dihydrazide/CH3ONH2,HCl=1/16.16/0.044/0.265. The dihydrazide content of the porous matrix is 0.8 mol.Math.dm.sup.−3 and the methoxyamine content is 4.8 mol.Math.dm.sup.−3.

Example 7: TMOS Matrix Doped with Adipic Acid Dihydrazide and Methoxyamine

[0112] Reagents: Adipic acid dihydrazide (Sigma Aldrich, CAS number 1071-93-8, molar mass=174.2 g.Math.mol.sup.−1, purity 98%), CH3ONH2,HCl (Sigma Aldrich, CAS number 593-56-6, molar mass=83.52 g.Math.mol.sup.−1, purity 98%), TMOS (CAS number: 681-84-5, molar mass=152.2 g.Math.mol.sup.−1 and density d=1.023 mg.Math.cm.sup.−3), methanol (CH.sub.3OH, molar mass 32.04 g.Math.mol.sup.−1, density=0.792 g.Math.cm.sup.−3, purity 98%). Plastic honeycomb mold with cylindrical wells 6 mm in diameter and 10 mm in depth.

[0113] V(TMOS)=17.033 mL

[0114] V(H.sub.2O)=32.967 mL

[0115] Adipic acid dihydrazide=1.745 g (0.2M)

[0116] CH3ONH2,HCl=0.42 g (0.1M)

[0117] V(total)=50 mL

[0118] Procedure: 1.745 g of adipic acid hydrazide and 0.42 g of CH.sub.3ONH.sub.2,HCl are introduced into a 100 mL flask and 32.967 mL of water are added. The mixture is stirred until dissolution of the two compounds is complete. 17.033 mL of TMOS are added and the mixture is left with magnetic stirring. Formation of two phases is observed and the mixture is left with stirring until the mixture becomes homogeneous. The mixture is poured into a honeycomb mold placed in a crystallizer. The mold is covered with an aluminum membrane and the mold is placed in a desiccator equipped with a relative humidity indicator. At the end of 3 days after gelling, the aluminum membrane is replaced with a semipermeable membrane and the desiccator is flushed with a stream of N2 at a rate of 300 mL/min. Drying is halted when the humidity indicator indicates between 0.5 to 2% relative humidity.

[0119] The dry granules obtained are transparent.

[0120] In the present example, the molar proportions of the reagents are TMOS/H.sub.2O/adipic acid dihydrazide/CH3ONH2,HCl=1/16.16/0.0866/0.043. The dihydrazide content of the matrix is 1.6 mol.Math.dm.sup.−3 and the methoxyamine content is 0.8 mol.Math.dm.sup.−3.

Example 8: TMOS/APTES Matrix Doped with Methoxyamine

[0121] Reagents: CH.sub.3ONH.sub.2,HCl (Sigma Aldrich, CAS number 593-56-6, molar mass=83.52 g.Math.mol.sup.−1, purity 98%), TMOS (CAS number: 681-84-5, molar mass=152.2 g.Math.mol.sup.−1 and density d=1.023 mg.Math.cm.sup.−3), APTES (CAS number: 919-30-2, purity 99%, molar mass=221.37 g.Math.mol.sup.−1 and density d=0.946 mg.Math.cm.sup.−3), methanol (CH.sub.3OH, molar mass 32.04 g.Math.mol.sup.−1, density=0.792 g.Math.cm.sup.−3, purity 98%). Plastic honeycomb mold with cylindrical wells 6 mm in diameter and 10 mm in depth.

[0122] 5M solution of CH3ONH2,HCl with 2.506 g dissolved in 6 mL of H.sub.2O

[0123] V(TMOS)=9.447 mL

[0124] V(APTES)=0.150 mL

[0125] V(MeOH)=20.547

[0126] V(H.sub.2O)=0.937 mL

[0127] CH3ONH2,HCl=5.92 mL of the 5 M aqueous solution (0.8M)

[0128] V(total)=37 mL

[0129] Procedure: 9.447 mL of TMOS and 0.15 mL of APTES are introduced into a 60 mL flask and 20.547 mL of MeOH are added. The mixture is stirred and then 5.92 mL of the aqueous methoxyamine solution and 0.937 mL of water are added and the mixture is left with magnetic stirring. The mixture is poured into a honeycomb mold placed in a crystallizer. The mold is covered with an aluminum membrane and the mold is placed in a desiccator equipped with a relative humidity indicator. At the end of 3 days after gelling, the aluminum membrane is replaced with a semipermeable membrane and the desiccator is flushed with a stream of N2 at a rate of 300 mL/min. Drying is halted when the humidity indicator indicates between 0.5 to 2% relative humidity.

[0130] The dry granules obtained are white.

[0131] In the present example, the molar proportions of the reagents are TMOS/APTES/MeOH/H.sub.2O/CH3ONH2,HCl=0.99/0.01/8/6/0.466. The methoxyamine content of the matrix is 6.4 mol.Math.dm.sup.−3.

Example 9: TMOS/Cl-TMOS Matrix Doped with Methylhydroxyamine in Buffered Medium

[0132] Reagents: MeHA,HCl (Sigma Aldrich, CAS number 4229-44-1, molar mass=83.52 g/mol, purity 98%), TMOS (CAS number: 681-84-5, molar mass=152.2 g/mol and density d=1.023 mg/mL), ClTMOS (CAS number: 2530-87-2, molar mass=198.7 g/mol, density=1.09 mg/mL), MeOH (molar mass=32.04 g/mole, d=0.791 mg/mL, 0.51 M citrate buffer (pH=4.6), Plastic honeycomb mold with cylindrical wells 6 mm in diameter and 10 mm in depth. [0133] 5M solution of MeHA,HCl with 6.264 g dissolved in 15 mL of H.sub.2O [0134] Citrate buffer, pH=4.6, obtained by mixing 25.5 mL of citric acid (2M) and 24.5 mL of sodium citrate (2M) in 50 mL of water.

[0135] V(TMOS)=22.823 mL

[0136] V(Cl-TMOS)=0.939 mL

[0137] MeOH=13.354 mL

[0138] V(H.sub.2O)=0.384 mL

[0139] V(MeHA,HCl 5M)=4 mL (0.4M)

[0140] 7.5 mL of citrate buffer

[0141] V(total)=50 mL

[0142] Procedure: In a 100 mL flask, 22.823 mL of TMOS are mixed with 0.939 mL of Cl-TMOS and 13.354 mL of MeOH. 23.083 mL of water with magnetic stirring. The mixture is cooled to −25° C. A second mixture is made with 7.5 mL of buffer solution, 4 mL of the aqueous solution of MeHA,HCl and 0.384 mL of water and is poured into the first mixture cooled to −25° C. Stirring is maintained for 6 min and then the mixture is returned to ambient temperature and is poured into a honeycomb mold placed in a crystallizer. The mold is covered with an aluminum membrane and is placed in a desiccator equipped with a relative humidity indicator. Gelling sets in after 30-35 min. Two days after gelling, the aluminum membrane is replaced with a semipermeable membrane (AB-Gene Greiner one). The desiccator is flushed with a stream of inert gas (Ar or N2) at a rate of 300 mL/min, and drying is halted when the humidity indicator indicates between 0.5 to 2% relative humidity.

[0143] After drying, transparent sol gel granules are obtained with dimensions close to cylinders of 3 mm in diameter and 5 mm in length. The methylhydroxyamine content of the porous sol-gel matrix is 4.0 mol.Math.dm.sup.−3.

[0144] In the present example, the molar proportions of the reagents are TMOS/ClTMOS/MeOH/H.sub.2O/MeHA,HCl/citric acid/sodium citrate=1/0.033/2.21/4.3/0.13/0.024/0.025

Example 10: TMOS-Cl-TMOS Matrix Doped with Tetraethylenepentamine (TEPA)

[0145] Reagents: TEPA (Sigma Aldrich, CAS number 112-57-2, molar mass=194.34 g.Math.mol.sup.−1, technical grade, d=0.998 g/mL), TMOS (CAS number: 681-84-5, molar mass=152.2 g.Math.mol.sup.−1 and density d=1.023 mg.Math.cm.sup.−3), ClTMOS (CAS number: 2530-87-2, molar mass=198.7 g/mol, density=1.09 mg/mL), methanol (molar mass=32.04 g.Math.mol.sup.−1, d=0.791 g.Math.mL.sup.−1) HCl 12.18 M. Plastic honeycomb mold with cylindrical wells 6 mm in diameter and 10 mm in depth.

[0146] V(TMOS)=11.903 mL

[0147] V(ClTMOS)=0.469 mL

[0148] V(MeOH)=18.78 mL

[0149] V(H.sub.2O)=5.938 mL

[0150] V(HCl)=4.51 mL

[0151] TEPA=3.41 mL

[0152] V(total)=50 mL

[0153] Procedure: In a 100 mL round-bottom flask, 11.903 mL of TMOS are mixed with 0.469 mL of ClTMOS and 8.0 mL of MeOH. The mixture is kept at −25° C. and is stirred for 10 min. A second mixture, consisting of 10.78 mL of MeOH, 3.41 mL of TEPA, 4.51 mL of concentrated HCl (fuming HCl 37%; Sigma Aldrich, CAS number 7647-01-0), is poured into the flask and the final mixture is stirred vigorously for 2 minutes. The mixture is poured into a honeycomb mold placed in a crystallizer. Gelling sets in 5 minutes after. The mold is covered with an aluminum membrane and the mold is placed in a desiccator equipped with a relative humidity indicator. The aluminum membrane is replaced with a semipermeable membrane and the desiccator is flushed with a stream of N2 at a rate of 300 mL/min, and drying is halted when the humidity indicator indicates between 0.5 to 2% relative humidity.

[0154] The dry granules obtained are transparent and pale yellow in color.

[0155] In the present example, the molar proportions of the reagents are TMOS/ClTMOS/MeOH/H.sub.2O/HCl/TEPA=1/0.03/5.75/6.5/0.7/0.2. The TEPA concentration of the matrix is 2.88 mol.Math.dm.sup.−3.

[0156] II. Characterization of Porosity and Filtration Properties

[0157] II.1 Porosity and Specific Surface Area

[0158] The specific surface areas, pore diameters, and proportions of micropores and mesopores were determined by analysis of the liquid nitrogen adsorption-desorption isotherm (77 K) with the DFT (Density Functional Theory) model, using the Autosorb 1 from Quantachrome.

[0159] The results are summarized in Table 1 below.

[0160] II.2 Trapping Efficacy in Formaldehyde Stream

[0161] The tests for measuring trapping efficacy in a stream are carried out with gas mixtures containing formaldehyde at high concentration, using the device described below.

Formaldehyde Filter Exposure Device

[0162] A permeation oven (model PUL010 from Calibrage-fivespillard) is used to generate a gaseous stream of nitrogen containing formaldehyde. Since formaldehyde is unstable in monomeric form, paraformaldehyde is used. This polymer is placed in a permeation tube, which is closed with a permeable membrane and placed into the oven. The oven is heated to 103° C. to give off the monomeric formaldehyde vapor. The oven is flushed with a gas stream of 150 mL/min.

[0163] At the exit of the permeation oven, the concentration of formaldehyde in the stream of nitrogen of 150 ml/min is 10.7 ppm or 13.375 mg/m.sup.3. This mixture is diluted with humid air and is conveyed into a 1L round-bottom flask which has four outlets. The 1.sup.st outlet is connected to a formaldehyde sensor, Profil'air® (Ethera, France), which measures the concentration of formaldehyde in the flask. The 2.sup.nd and 3.sup.rd outlets are each dedicated to exposure of a filter, and the 4.sup.th outlet is the vent. In the flask, the concentration of formaldehyde is 900±100 ppb with a humidity of 30±3%.

[0164] Each filter is composed of 0.5 g of the material under test, placed in a 3 mL syringe equipped with two end-pieces. The syringe is connected by one of the end pieces to the flask of gaseous mixture, and by the other end to a formaldehyde filter, which is connected in turn to a pump. The formaldehyde/air mixture is drawn through the syringe with a flow rate of 200 ml/min. The concentration of formaldehyde measured upstream (outlet 1) and downstream of the filter (outlets 2 and 3) twice a day makes it possible to work out the amount of formaldehyde trapped in each filter after a predetermined exposure time.

[0165] Leaching tests were also carried out to show the irreversibility of the reaction. Each filter already exposed is subjected to a humid stream of N.sub.2 (50% RH) at a rate of 400 ml/min. The stream emerging from the filter is taken into a 500 mL round-bottom flask, from which the gas is pumped at 200 mL/min for measurement of formaldehyde using a Profil'air® sensor (Ethera, France).

Measurement of Trapping Efficacy

[0166] The efficacy of trapping of the filters from examples 1 to 10 was evaluated. The results are summarized in Table 1.

[0167] FIG. 1 shows an “upstream” concentration curve, corresponding to the concentration of formaldehyde measured without filter, and a “downstream” concentration curve, measured after passage through a filter composed of the material of example 3. FIG. 2 represents the difference and corresponds to the amount of formaldehyde trapped over time. Calculation of the area under this curve gives the total amount of formaldehyde trapped. After 25000 minutes, amounting to 17.4 days, the filter still does not show saturation. The amount of formaldehyde trapped is 10.9 mg/g (g of filter). With the trapping of the formaldehyde, the filter becomes green and the intensity of the coloration increases with the amount of pollutant trapped.

TABLE-US-00001 Porosity Sads (BET/DFT) V(pore) % micro/meso- Trapping efficacy, pores mg CH2O/g filter Degree Formulation Pore diameter for x h of of Example No (molar ratio) distribution exposure leaching 2 TMOS/ClTMOS/MeOH/H2O/ 404/508 m2/g 9.56 mg/g - 124 h — CH3ONH2, HCl 0.16 cm3/g Color change: 1/0.032/8.3/6.25/0.484 93.5%/6.5% yellow .fwdarw. green 10-26 Å 3 TMOS/H2O/CH3ONH2, HCl 1060/1150 m2/ 10.9 mg/g - 427 h 0.09% 1/16.16/0.353 g Color change: 0.52 cm3/g white .fwdarw. green 65.2%/34.8% 11-40 Å 4 TMOS/H2O/adipic acid 423/316 m2/g 9.59 mg/g - 360 h 0.30% dihydrazide 1/16.64/0.044 0.33 cm3/g 0%/100% 21-80 Å 5 TMOS/H2O/adipic acid 267/205 m2/g 9.03 mg/g - 333 h 0.33% dihydrazide 1/16.64/0.088 0.24 cm3/g 0%/100% 29-80 Å 6 TMOS/H2O/adipic acid 560/420 m2/g 37 mg/g - 450 h 0.1%  dihydrazide/CH3ONH2, HCl 0.32 cm3/g >50 mg/g at 1/16.16/0.044/0.265 16.2%/83.8% saturation 11-55 Å 7 TMOS/H2O/adipic acid 14.3/6.5 m2/g 11 mg/g - 288 h — dihydrazide/CH3ONH2, HCl 0.015 cm3/g 1/16.16/0.087/0.043 0/100% 36-96 Å 8 TMOS/APTES/MeOH/H2O/ — 8.91 mg/g 334 h — CH3ONH2, HCl White to green 0.99/0.01/8/6/0.446 9 TMOS/ClTMOS/MeOH/H2O/ 242/249 m2/g 4.16 mg/g 110 h — MeHA, HCl + citrate buffer 11-27 Å pH = 4.7 61.9% 10 TMOS/ClTMOS/MeOH/H2O/ — 16.18 mg/g, 273 h HCl/ Bright yellow- TEPA dark 1/0.03/5.75/6.5/0.7/0.2 yellow/brown

[0168] II.3 Trapping in Stream of Acetone and in Stream of Benzaldehyde

[0169] The tests measuring trapping efficacy in a stream are carried out with saturated vapor either of acetone or of benzaldehyde at high concentration, by passing the saturated vapor in static mode. For this, the filter is exposed above the pure liquid.

[0170] On exposure of matrices exposed to saturated pollutant vapor, a green coloration is observed with acetone (tests with samples from Examples 3 and 6) and a reddish brown coloration with benzaldehyde (test with sample from Example 6).