Microporous aerogel

1 . A silica-based microporous aerogel for carbon dioxide (CO 2 ) capture, the microporous aerogel comprises a reaction product of reagents comprising at least one amino substituted silane, at least one alkyl substituted silane, and at least one silicate, wherein:

the microporous aerogel comprises a plurality of pores wherein at least 50% of the pores have a diameter of less than about 2 nm;

the microporous aerogel has a surface area in a range between about 0.1 m2/g and about 500 m2/g;

the at least one silicate is in accordance with Formula 3:

Si(OR 7 ) 4    Formula 3,

wherein R 7 is C1-6alkyl; and

the at least one silicate has a % loading of at least about 20 mol %.

2 . The microporous aerogel according to claim 1 , wherein the aerogel adsorbs CO 2 from the air in environments with a CO 2 concentration of less than about 10 vol. %.

3 . The microporous aerogel according to claim 1 , wherein the aerogel adsorbs CO 2 from the air in enclosed environments with a CO 2 concentration of less than about 2 vol. %.

4 . The microporous aerogel according to claim 1 , wherein the aerogel adsorbs CO 2 from the air in environments with a CO 2 concentration of about 0.04 vol. %.

5 . The microporous aerogel according to claim 4 , wherein the CO 2 adsorption of the aerogel is at least 0.47 mmol/g.

6 . The microporous aerogel according to claim 1 , wherein the amino substituted silane is according to Formula 1:

R 1 Si(OR 2 ) n -L-NH 2    Formula 1

wherein:

R 1 is C1-6alkyl or is absent;

R 2 is C1-6alkyl;

L is a —C1-6alkyl-linker group between the silicon and nitrogen atoms; and

n is 2 or 3.

7 . The microporous aerogel according to claim 1 , wherein the alkyl substituted silane is according to Formula 2:

R 5 m Si(OR 6 ) n    Formula 2

wherein:

R 5 and R 6 are each independently selected from C1-6alkyl; and

m is 1 and n is 3 or m and n are each 2.

8 . The microporous aerogel according to claim 1 , wherein:

the at least one amino substituted silane is 3 aminopropyl(diethoxy)methylsilane with a % loading of about 40 mol %, the at least one alkyl substituted silane is triethoxymethylsilane with a % loading of about 40 mol %, and the at least one silicate is tetraethyl orthosilicate with a % loading of about 20 mol %; or

the at least one amino substituted silane is 3 aminopropyl(triethoxy)silane with a % loading of about 60 mol %, the at least one alkyl substituted silane is triethoxymethylsilane with a % loading of about 20 mol %, and the at least one silicate is tetraethyl orthosilicate with a % loading of about 20 mol %; or

the at least one amino substituted silane is 3 aminopropyl(diethoxy)methylsilane with a % loading of about 50 mol %, the at least one alkyl substituted silane is a mixture of triethoxymethylsilane with a % loading of about 15 mol % and triethoxy(ethyl)silane with a % loading of about 15 mol %, and the at least one silicate is tetraethyl orthosilicate with a % loading of about 20 mol %.

9 . The microporous aerogel according to claim 1 , wherein:

the at least one amino substituted silane is 3 aminopropyl(triethoxy)silane with a % loading of about 40 mol %, the at least one alkyl substituted silane is triethoxymethylsilane with a % loading of about 40 mol %, and the at least one silicate is tetraethyl orthosilicate with a % loading of about 20 mol %; or

the at least one amino substituted silane is 3 aminopropyl(diethoxy)methylsilane with a % loading of about 40 mol %, the at least one alkyl substituted silane is triethoxymethylsilane with a % loading of about 20 mol %, and the at least one silicate is tetraethyl orthosilicate with a % loading of about 40 mol %; or

the at least one amino substituted silane is 3 aminopropyl(triethoxy)silane with a % loading of about 40 mol %, the at least one alkyl substituted silane is triethoxymethylsilane with a % loading of about 20 mol %, and the at least one silicate is tetraethyl orthosilicate with a % loading of about 40 mol %; or

the at least one amino substituted silane is 3 aminopropyl(diethoxy)methylsilane with a % loading of about 40 mol %, the at least one alkyl substituted silane is triethoxy(ethyl)silane with a % loading of about 40 mol %, and the at least one silicate is tetraethyl orthosilicate with a % loading of about 20 mol %; or

the at least one amino substituted silane is 3 aminopropyl(triethoxy)silane with a % loading of about 40 mol %, the at least one alkyl substituted silane is triethoxy(ethyl)silane with a % loading of about 40 mol %, and the at least one silicate is tetraethyl orthosilicate with a % loading of about 20 mol %; or

the at least one amino substituted silane is 3 aminopropyl(diethoxy)methylsilane with a % loading of about 40 mol %, the at least one alkyl substituted silane is dimethyldiethoxysilane with a % loading of about 40 mol %, and the at least one silicate is tetraethyl orthosilicate with a % loading of about 20 mol %; or

the at least one amino substituted silane is 3 aminopropyl(diethoxy)methylsilane with a % loading of about 40 mol %, the at least one alkyl substituted silane is a mixture of triethoxymethylsilane with a % loading of about 20 mol % and dimethyldiethoxysilane with a % loading of about 20 mol %, and the at least one silicate is tetraethyl orthosilicate with a % loading of about 20 mol %; or

the at least one amino substituted silane is 3 aminopropyl(diethoxy)methylsilane with a % loading of about 60 mol %, the at least one alkyl substituted silane is dimethyldiethoxysilane with a % loading of about 10 mol %, and the at least one silicate is tetraethyl orthosilicate with a % loading of about 30 mol %; or

the at least one amino substituted silane is 3 aminopropyl(diethoxy)methylsilane with a % loading of about 40 mol %, the at least one alkyl substituted silane is dimethyldiethoxysilane with a % loading of about 30 mol %, and the at least one silicate is tetraethyl orthosilicate with a % loading of about 30 mol %; or

the at least one amino substituted silane is 3 aminopropyl(triethoxy)silane with a % loading of about 40 mol %, the at least one alkyl substituted silane is a mixture of triethoxymethylsilane with a % loading of about 20 mol % and dimethyldiethoxysilane with a % loading of about 20 mol %, and the at least one silicate is tetraethyl orthosilicate with a % loading of about 20 mol %; or

the at least one amino substituted silane is 3 aminopropyl(diethoxy)methylsilane with a % loading of about 40 mol %, the at least one alkyl substituted silane is a mixture of triethoxymethylsilane with a % loading of about 20 mol % and triethoxy(ethyl)silane with a % loading of about 20 mol %, and the at least one silicate is tetraethyl orthosilicate with a % loading of about 20 mol %; or

the at least one amino substituted silane is 3 aminopropyl(diethoxy)methylsilane with a % loading of about 60 mol %, the at least one alkyl substituted silane is triethoxymethylsilane with a % loading of about 20 mol %, and the at least one silicate is tetraethyl orthosilicate with a % loading of about 20 mol %; or

the at least one amino substituted silane is 3 aminopropyl(triethoxy)silane with a % loading of about 60 mol %, the at least one alkyl substituted silane is triethoxymethylsilane with a % loading of about 20 mol %, and the at least one silicate is tetraethyl orthosilicate with a % loading of about 20 mol %; or

the at least one amino substituted silane is 3 aminopropyl(diethoxy)methylsilane with a % loading of about 60 mol %, the at least one alkyl substituted silane is a mixture of triethoxymethylsilane with a % loading of about 10 mol % and triethoxy(ethyl)silane with a % loading of about 10 mol %, and the at least one silicate is tetraethyl orthosilicate with a % loading of about 20 mol %; or

the at least one amino substituted silane is 3 aminopropyl(diethoxy)methylsilane with a % loading of about 50 mol %, the at least one alkyl substituted silane is triethoxymethylsilane with a % loading of about 25 mol %, and the at least one silicate is tetraethyl orthosilicate with a % loading of about 25 mol %; or

the at least one amino substituted silane is 3 aminopropyl(diethoxy)methylsilane with a % loading of about 60 mol %, the at least one alkyl substituted silane is triethoxy(ethyl)silane with a % loading of about 20 mol %, and the at least one silicate is tetraethyl orthosilicate with a % loading of about 20 mol %.

10 . The microporous aerogel according to claim 1 , wherein the microporous aerogel has a free amine content that is less than, or equal to, about 60 mol %.

11 . The microporous aerogel according to claim 1 , wherein the density of the microporous aerogel is in a range between about 0.02 g/cm 3 to about 0.6 g/cm3.

12 . The microporous aerogel according to claim 1 , wherein the aerogel is in the form of particles, powders, beads, granules, sheets/layers, cast blocks, cylinders, discs, porous membranes or monoliths or is applied as applied as a coating composition or film on a substrate.

13 . The microporous aerogel according to claim 1 , wherein, the at least one amino substituted silane is 3 aminopropyl(diethoxy)methylsilane with a % loading of about 60 mol %, and the at least one silicate is tetraethyl orthosilicate with a % loading of about 40 mol %.

14 . An aerogel composite comprising:

a microporous aerogel according to claim 1 ; and

one or more additives selected from a buffer, a binder, a metal organic framework (MOF), and a nanoparticle.

15 . The aerogel composite according to claim 14 , wherein the additive has a % loading of about 5 to about 35 wt. %.

16 . The aerogel composite according to claim 14 , further comprising a lubricant, and/or a solvent.

17 . The aerogel composite according to claim 14 , wherein the composite is in the form of a pellet, bead, sheet, or granule, or is applied as a coating composition, paste or film on a substrate.

18 . The aerogel composite according to claim 14 , wherein the one or more additives includes a binder that is selected from cellulose-based polymers, silane-based polymers, cellulose-siloxane-based polymers, polyglycol-based polymers, polyvinyl pyrrolidone, polyvinyl alcohol, polyethylene imine, bentonite, graphite, or combinations thereof.

19 . A process for preparing a silica-based microporous aerogel for carbon dioxide (CO 2 ) capture, wherein the microporous aerogel comprises a reaction product of reagents comprising at least one amino substituted silane, at least one alkyl substituted silane, and at least one silicate that is in accordance with Formula 3:

Si(OR 7 ) 4    Formula 3

wherein R 7 is C1-6alkyl, and

wherein the at least one silicate has a % loading of at least about 20 mol %, the process comprising:

(i)(a) mixing an aqueous solution comprising the at least one amino substituted silane, the at least one alkyl substituted silane, and the at least one silicate, and a solvent system, to form a wet-gel matrix; and

(ii) drying the wet-gel matrix to provide the silica-based microporous aerogel,

wherein the dried silica-based microporous aerogel has a plurality of pores wherein at least 50% of the pores have a diameter of less than about 2 nm,

the microporous aerogel has a surface area in a range between about 0.1 m 2 /g and about 500 m 2 /g;

with the proviso that drying the wet-gel matrix does not involve supercritical CO 2 .

20 . The process according to claim 19 , wherein step (i) further comprises step (i)(b) rinsing the wet-gel matrix.

21 . The process according to claim 19 , wherein the process is a sol gel process and step (ii) comprises:

(a1) optionally heating the wet gel matrix to obtain a gel; and

(a2) drying the gel by solvent evaporation and/or heat treatment, to thereby provide the dried silica-based microporous aerogel.

22 . The process according to claim 19 , wherein step (ii) further comprises:

(b1) applying the wet gel matrix is applied to a substrate to form a wet-gel film coating the substrate; and

(b2) drying the wet-gel film by solvent evaporation and/or heat treatment, to thereby provide the dried silica-based microporous aerogel as a coating on the coated substrate.

23 . The process according to claim 19 , wherein the process further comprises an activation step.

24 . The process according to claim 19 , wherein the amount of amino substituted silane is in a range between about 10% and about 80% based on the total weight of the microporous aerogel;

the amount of alkyl substituted silane is in a range between about 10% and about 80% based on the total weight of the aerogel; and

the amount of silicate is in a range between about 10% and about 50% based on the total weight of the microporous aerogel.

25 . The process according to claim 19 , further comprising addition of one or more additives.

26 . A process for preparing an aerogel composite, the process comprising:

preparing a dried silica-based microporous aerogel by the process according to claim 19 ;

mixing the dried silica-based microporous aerogel with one or more additives, and optionally a lubricant, to form a mixture, the one or more additives having a % loading of about 5 to about 35 wt. %;

and either:

(c1) pressing the mixture into a pellet; or

(c2) liquid extrusion of the mixture to provide a viscous paste.

27 . A process for capturing carbon dioxide (CO 2 ) from a gaseous stream or atmosphere containing CO 2 comprising:

contacting the gaseous stream or atmosphere with a silica-based microporous aerogel for capturing at least some CO 2 from the gaseous stream or atmosphere,

wherein the silica-based microporous aerogel is in accordance with claim 1 or is a silica-based microporous aerogel prepared by the process according to claim 19 .

28 . The process according to claim 27 , wherein the gaseous stream or atmosphere has a CO 2 concentration of less than about 150,000 ppm; and one or more of:

wherein the gaseous stream or atmosphere has a CO 2 concentration in a range between about 3,000 ppm and about 150,000 ppm, wherein the process is direct air capture in external power plants (DACex);

wherein the gaseous stream or atmosphere has a CO 2 concentration in a range between about 4,000 ppm and about 5,000 ppm, wherein the process is direct air capture (DAC) of exhaled breath in masks or personal protective equipment (DACp);

wherein the gaseous stream or atmosphere has a CO 2 concentration of less than about 2,000 ppm, wherein the process is direct air capture (DAC) in indoor sealed environments (DACi); and/or wherein the gaseous stream or atmosphere is ambient air; and

wherein the gaseous stream or atmosphere is less than about 500 ppm, wherein the process is direct air capture (DAC); and/or wherein at least about 50% to about 99% of CO 2 is removed from the gaseous stream or atmosphere.

29 . The process according to claim 27 , wherein the process further comprises a regeneration recovery process to desorb the absorbed CO 2 from the silica-based microporous aerogel.

30 . The process according to claim 29 , wherein the regeneration recovery process comprises one or more of:

heating the silica-based microporous aerogel to a temperature range of between about 60° C. and about 140° C.,

reducing pressure,

flow of a gas with low CO 2 ,

heating the silica-based microporous aerogel by contact with steam.

31 . An adsorption apparatus for capturing carbon dioxide (CO 2 ) from a gaseous stream or atmosphere containing CO 2 comprising: a chamber enclosing at least one silica-based microporous aerogel that is in accordance with claim 1 , or that is prepared according to claim 19 , the chamber comprising an inlet through which gaseous stream can flow to the silica-based microporous aerogel, and an outlet through which the effluent gaseous stream can flow out from the silica-based microporous aerogel.

32 . The apparatus according to claim 31 , wherein the chamber comprises silica-based microporous aerogel in the form of a pellet, or is coated with the silica-based microporous aerogel located or packed within the chamber.