Claims:1. A composite material comprising Covalent Organic Framework(s) (COF(s)) and zeolite(s), wherein the zeolite(s) is coated by the COF(s).
2. The composite material as claimed in claim 1, wherein the zeolite(s) is selected from a group comprising zeolite A, zeolite X, zeolite Y, mordenite, zeolite L, zeolite beta, ZSM-5, zeolite 5A, zeolite 13X, or any combination thereof.
3. The composite material as claimed in claim 1, wherein the COF(s) is selected from a group comprising Tp-Azo, TpOMe-Azo, Tp-BD, Tp-BDMe2, Tp-Azo-BDMe2, or any combination thereof.
4. The composite material as claimed in claim 1, wherein the composite material comprises from about 2.5 % to about 10% zeolite(s).
5. The composite material as claimed in claim 1, wherein the composite material has about 1.5 times to about 2.9 times higher surface area than pristine zeolite.
6. The composite material as claimed in claim 1, wherein surface area of the composite material ranges from about 1200m2/g to about 2200m2/g.
7. The composite material as claimed in claim 1, wherein the composite material has about 6% to about 18% lower hygroscopicity than pristine zeolite.
8. A method of preparing a composite material comprising Covalent Organic Framework(s) (COF(s)) and zeolite(s), the method comprising:
mixing aromatic diamine, p-Toluenesulfonic acid monohydrate (PTSA.H2O), 1,3,5-Triformylphloroglucinol (Tp) and zeolite(s) by grinding to obtain a homogeneous mixture; and
heating the homogeneous mixture to obtain the composite material.
9. The method as claimed in claim 8, wherein the method comprises
a) grinding the aromatic diamine and the p-Toluenesulfonic acid monohydrate (PTSA.H2O) to obtain a mixture;
b) adding the 1,3,5-Triformylphloroglucinol (Tp) to the mixture and subjecting the resultant mixture to further grinding to obtain a paste;
c) adding the zeolite(s) to the paste and subjecting the paste and the zeolite to further grinding to obtain a homogeneous mixture; and
d) heating the homogeneous mixture to obtain the composite material.
10. The method as claimed in claims 8 or 9, wherein the aromatic diamine is selected from a group comprising 4,4’-Azodianiline (Azo), Benzidine (BD), 3,3’-dimethylbenzidine (BDMe2), 3,3’-dinitrobenzidine (BD(NO2)2), 3,3’-dihydroxylbenzidine (BD(OH)2), 3,3’-dimethoxybenzidine (BD(OMe)2), Azo-BD, or any combination thereof.
11. The method as claimed in claim 9, wherein the grinding in step (a) is performed for about 10 minutes to about 20 minutes; wherein the grinding in step (b) is performed for about 15 minutes to about 30 minutes; and wherein the grinding in step (c) is performed for about 15 minutes to about 30 minutes.
12. The method as claimed in claims 8 or 9, wherein the heating is at a temperature of about 80°C to about 100°C for time ranging from about 12 hours to 15 hours.
13. The method as claimed in claims 8 or 9, wherein the method further comprises
allowing the composite material to cool to room temperature;
washing the cooled composite material; and
drying the washed composite material.
14. The method as claimed in claim 13, wherein the washing is performed with solvent(s) selected from a group comprising water, N, N-dimethylacetamide and acetone or any combination thereof; and wherein the drying is performed at a temperature of about 70°C to about 80°C.
15. The method as claimed in claim 14, wherein the washing is performed sequentially with water, N, N-dimethylacetamide and acetone.
16. The composite material as claimed in claim 1 for use in selective gas separation.
17. A method of selective gas separation, wherein the gas separation is performed through the composite material as claimed in claim 1.
18. A device for selective gas separation comprising the composite material as claimed in claim 1 as a sorbent.
19. The composite material as claimed in claim 16, the method as claimed in claim 17 or the device as claimed in claim 18, wherein the gas is selected from, carbon dioxide, carbon monoxide, hydrogen, methane, oxygen, and nitrogen or any combination thereof.
, Description:FIELD OF THE INVENTION:
[0001] The present disclosure relates to the field of zeolites and composites thereof. Particularly, the present disclosure relates to a composite material comprising Covalent Organic Framework(s) (COF(s)) and zeolite(s), wherein the zeolite(s) is coated by the COF(s). Said composite material of the present disclosure provides advantages of high surface area and chemical stability. Further provided herein is a method of synthesis of said composite material and applications thereof.

BACKGROUND AND PRIOR ART OF THE INVENTION

[0002] Zeolites are crystalline microporous aluminosilicates with framework structure of three-dimensional tetrahedral units generating a network of pores and cavities having molecular dimensions. They are built by SiO4 and AlO4 tetrahedra (or by other tetrahedra such as PO4, GaO4 etc.), which are linked by oxygen atoms. A defining feature of zeolites is that their frameworks are made up of 4-coordinated atoms forming tetrahedra. These tetrahedra are linked together by their corners and make a rich variety of beautiful structures. The framework structure may contain linked cages, cavities, or channels, which are big enough to allow small molecules to enter. The system of large voids explains the consistent low specific density of these compounds. In zeolites used for various applications, the voids are interconnected and form long wide channels of various sizes depending on the compound. These channels allow the easy drift of the resident ions and molecules into and out of the structure. The aluminosilicate framework is negatively charged and attracts the positive cations that reside in cages to compensate negative charge of the framework. Due to specific pore sizes and large surface areas, the synthesis research of zeolite has been greatly developed and they offer a potential for a variety of industrial uses including molecular sieves, ion-exchangers, adsorbents, catalysts, detergent builders, the removal of cations from acid mine drainage and industrial wastewater. Zeolites are generally very good for carbon dioxide (CO2) capture except the drawback that when this material is used for the real application, the presence of moisture reduces the performance due to their hygroscopic nature.
However, given the natural abundance and low production cost of zeolites, the material finds a lot of interest and demand in industries. Accordingly, the need of the hour is zeolite or zeolite-based materials that have improved chemical stability, high water resistance and high surface area.

SUMMARY OF THE DISCLOSURE
[0003] Addressing the aforesaid lacunae in the art, the present disclosure provides a composite material comprising Covalent Organic Framework(s) (COF(s)) and zeolite(s), wherein the zeolite(s) is coated by the COF(s).
[0004] In some embodiments, the zeolite(s) is selected from a group comprising zeolite A, zeolite X, zeolite Y, mordenite, zeolite L, zeolite beta, ZSM-5, zeolite 5A, zeolite 13X, or any combination thereof.
[0005] In some embodiments, the COF(s) is selected from a group comprising Tp-Azo, TpOMe-Azo, Tp-BD, Tp-BDMe2, Tp-Azo-BDMe2, or any combination thereof.
[0006] In some embodiments, the composite material comprises from about 2.5 % to about 10% zeolite(s).
[0007] In some embodiments, the composite material has about 1.5 times to about 2.9 times higher surface area than pristine zeolite.
[0008] In some embodiments, the composite material has about 6% to about 18% lower hygroscopicity than pristine zeolite.
Further provided in the present disclosure is a method of preparing the composite material as described above, the method comprising:
mixing aromatic diamine, p-Toluenesulfonic acid monohydrate (PTSA.H2O), 1,3,5-Triformylphloroglucinol (Tp) and zeolite(s) by grinding to obtain a homogeneous mixture; and
heating the homogeneous mixture to obtain the composite material.
[0009] In some embodiments, the aromatic diamine is selected from a group comprising 4,4’-Azodianiline (Azo), Benzidine (BD), 3,3’-dimethylbenzidine (BDMe2), 3,3’-dinitrobenzidine (BD(NO2)2), 3,3’-dihydroxylbenzidine (BD(OH)2), 3,3’-dimethoxybenzidine (BD(OMe)2), Azo-BD, or any combination thereof.
[0010] In some embodiments, the aforesaid method further comprises
allowing the composite material to cool to room temperature;
washing the cooled composite material; and
drying the washed composite material.
[0011] Further envisaged herein is the composite material as described above for use in selective gas separation.

[0012] Also provided in the present disclosure is a method of selective gas separation, wherein the gas separation is performed through the composite material as described above.
[0013] Further provided herein is a device for selective gas separation comprising the composite material as described above as a sorbent.
[0014] In some embodiments, with regard to the gas separation as referred to above, the gas is selected from, carbon dioxide, carbon monoxide, hydrogen, methane, oxygen, and nitrogen or any combination thereof.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
[0015] In order that the disclosure may be readily understood and put into practical effect, reference will now be made to exemplary embodiments as illustrated with reference to the accompanying figures. The figures together with detailed description below, are incorporated in and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages, in accordance with the present disclosure where:
FIG 1. depicts the synthetic scheme of formation of TpAzo COF (COF@TpAzo).
FIG 2. depicts the sequential pictorial representation of the mechanochemical synthesis of TpAzo COF.
FIG 3. depicts the structure of Zeolite A (a) and Zeolite X (b).
FIG 4. depicts the schematic representation of the TpAzo COF/zeolite composite formation and selective gas separation.
FIG 5. depicts mechanochemical synthesis of TpAzo/Zeolite composite.
FIG 6. depicts comparative TGA spectra of TpAzo COF and the TpAzo/Zeolite composites.
FIG 7. depicts (a) FTIR and (b) XRD spectra of TPAzo COF and TPAzo/Zeolite composites.
FIG 8. depicts N2 uptake of zeolite 5A and TpAzo/5A at different concentrations of zeolite 5A at1 bar, 273K.
FIG 9. depicts N2 uptake of zeolite 13X and TpAzo/13X at different concentrations of zeolite 13X at 1 bar, 273K.
FIG 10. depicts gravimetric uptake capacity of TpAzo/5A and TpAzo/13X as compared to their pristine counterparts, reflected through water adsorption study at room temperature.
FIG 11. depicts photograph of the TpAzo/5A after 3(N) HCl treatment for 10 hours.
FIG 12. depicts CO2 uptake of TpAzo/5A, and TpAzo/5A treated with 3(N)HCl.
FIG 13. depicts CO2 uptake of TpAzo/5A, and TpAzo/5A treated with 0.1 (M) HCOOH, and 0.5(M) HCOOH.

DETAILED DESCRIPTION OF THE INVENTION
[0016] Addressing the requirements in the art, the present disclosure provides a zeolite based composite material. Particularly, the present disclosure provides a composite material comprising Covalent Organic Framework(s) (COF(s)) and zeolite(s).
[0017] However, before describing the composite material in further detail, provided below are definitions of terms used throughout the present disclosure.
[0018] As used herein, the term ‘composite material’ or ‘composite’ refers to the product of the present disclosure comprising the Covalent Organic Framework(s) (COF(s)) and zeolite(s), wherein the Covalent Organic Framework(s) (COF(s)) coats the zeolite(s).
[0019] As used herein, the term ‘covalent organic framework’ or ‘COF’ refers to a class of materials that form two- or three- dimensional crystalline organic polymeric structures through reactions between organic precursors resulting in strong, covalent bonds to afford porous, stable, and crystalline materials.
[0020] As used herein, the term ‘coated’ or ‘coating’ or ‘coat’ or other obvious variants thereof refer to the structural feature of the composite material of the present disclosure wherein the zeolite(s) is protected by the COF by virtue of the zeolite being coated by the COF.
[0021] In order to define the components of the composite, the present disclosure refers to the composite in the form ‘COF/zeolite’. Further, reference to the composite in the form of for example ‘COF/zeolite_2.5’, ‘COF/zeolite_5’ or ‘COF/zeolite_10’ in the examples and figures refers to the amount (%) of the zeolite in the composite.
[0022] As used throughout the present disclosure, the term ‘Tp’ has been used as an abbreviation for 1,3,5-triformylphloroglucinol.
[0023] With respect to the use of various well-known components in the present disclosure whose concentrations are not particularly defined herein, said components are deemed to be used in concentrations that are well known to a person skilled in the art in the context of material science and/or metallurgical applications such as those described in the present disclosure.
[0024] As used throughout the present disclosure, ranges are a shorthand for describing each and every value within the range. Any value within the range can be selected as the terminus of the range.
[0025] With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity. The use of the expression ‘at least’ or ‘at least one’ suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results. The use of the expression ‘about’ refers to values ±5%, ±4% ±3% ±2% or ±1% of the values defined immediately following said term.
[0026] Throughout this specification, the word “comprise”, or variations such as “comprises” or “comprising” wherever used, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
[0027] As mentioned above, the present invention provides a composite material comprising Covalent Organic Framework(s) (COF(s)) and zeolite(s). Said composite material is specifically characterized by its internal structure wherein the COF(s) coats the zeolite(s).
[0028] Accordingly, provided herein is a composite material comprising Covalent Organic Framework(s) (COF(s)) and zeolite(s), wherein the zeolite(s) is coated by the COF(s).
[0029] Among other effects, said coating of the zeolite by the COFs serves the function of protecting the zeolite(s) and further, increasing the porosity and thus surface area of the zeolite.
[0030] In some embodiments, the zeolite(s) is selected from a group comprising zeolite A, zeolite X, zeolite Y, mordenite, zeolite L, zeolite beta, ZSM-5, zeolite 5A, zeolite 13X, or any combination thereof.
[0031] In some preferred embodiments, the zeolite(s) is selected from zeolite 5A and zeolite 13X or a combination thereof. Zeolites 5A and 13X have been interchangeably referred to as ‘5A’ and ‘13X’, respectively.
[0032] In some embodiments, the COF(s) is selected from a group comprising Tp-Azo, TpOMe-Azo, Tp-BD, Tp-BDMe2, Tp-Azo-BDMe2, or any combination thereof.
[0033] In some preferred embodiments, the COF(s) is Tp-Azo. For purposes of clarity, reference to ‘Tp-Azo’ or ‘TpAzo’ or ‘ Tp Azo’ alone or ahead of ‘COF’ for e.g. ‘TpAzo COF’ in the present disclosure implies reference to the COF formed from 1,3,5-triformylphloroglucinol (Tp) and 4,4’-Azodianiline (Azo). Said reference is intended to provide clarity as to the specific COF employed.
[0034] In exemplary embodiments, the zeolite is selected from zeolite 5A, zeolite 13X or both and the COF(s) is Tp-Azo.
[0035] In some embodiments, the composite material comprises from about 2.5% to about 10% zeolite(s).
[0036] In a non-limiting embodiment, the composite material comprises zeolite(s) at a concentration of about 2.5%, about 3%, about 3.5%, about 4%, about 4.5%, about 5%, about 5.5%, about 6%, about 6.5%, about 7%, about 7.5%, about 8%, about 8.5%, about 9%, about 9.5% or about 10%. In a non-limiting embodiment, a higher amount of zeolite may destroy the crystallinity of the COF structure by intruding inside the packing of lattices.
[0037] In some embodiments, the composite material comprises from about 90% to about 97.5% COF(s).
[0038] In a non-limiting embodiment, the composite material comprises COF at a concentration of about 90%, about 90.5%, about 91%, about 91.5%, about 92%, about 92.5%, about 93%, about 93.5%, about 94%, about 94.5%, about 95%, about 95.5%, about 96%, about 96.5%, about 97% or about 97.5%.
[0039] Industrially, zeolites are used for removing carbon dioxide (CO2) from high-pressure fuel gas streams using Pressure swing adsorption (PSA) and temperature swing adsorption (TSA) techniques. In order to facilitate efficient separation of gases such as CO2 it is desirable for zeolites to have high surface area.
[0040] Although both the zeolite and COF are highly porous in nature, COF has comparatively higher porosity and hence surface area. While zeolite has more thermal stability, the COF has more chemical stability and hydrophobicity. Zeolite is easy to prepare and is a naturally occurring material, but COF is a synthetic material. Protecting zeolite with COF as per the present disclosure confers improved porosity (hence surface area), chemical stability, and water resistance to the zeolite to facilitate efficient CO2 capture and sequestration.
[0041] Figures 1 and 2 provide the synthetic scheme of the formation of TpAzo COF and the sequential pictorial representation of the mechanochemical synthesis of TpAzo COF. Figure 3 provides the structure of Zeolite A (a) and Zeolite X (b). Figure 4 shows the internal structuring of the composite material.
[0042] In some embodiments, the composite material has about 1.5 times to about 2.9 times higher surface area than pristine zeolite.
[0043] In non-limiting embodiments, the composite material has about 1.5 times, about 1.6 times, about 1.7 times, about 1.8 times, about 1.9 times, about 2 times, about 2.1 times, about 2.2 times, about 2.3 times, about 2.4 times, about 2.5 times, about 2.6 times, about 2.7 times or about 2.9 times higher surface area than pristine zeolite.
[0044] In some embodiments, surface area of the composite material ranges from about 1200m2/g to about 2200m2/g.
[0045] In non-limiting embodiments, surface area of the composite material is about 1200m2/g, about 1400m2/g, about 1600m2/g, about 1800m2/g, about 2000m2/g or about 2200m2/g. The surface area of the composite material is therefore significantly higher than that of pristine zeolites powder which usually show surface area far below 1000 m2/g.
[0046] In some embodiments, the surface area varies with the concentration of zeolite i.e. the amount of zeolite added to the COF during synthesis of the composite material.
[0047] In some embodiments, in addition to improvement of surface area the composite material comprising the COF coated zeolite also enhances activity of the zeolite in terms of protection from acid and base up to a certain concentration.
[0048] Further, as mentioned above, while zeolites are generally considered as being suitable material for CO2 capture, the presence of moisture reduces capture performance due to their hygroscopic nature. The composite material of the present disclosure addresses said problem and is characterized by the protection of zeolites within the COFs. Said protection minimizes the hygroscopicity of Zeolites since the COFs are hydrophobic in nature.
[0049] In some embodiments, the composite material has about 6% to about 18% lower hygroscopicity than pristine zeolite.
[0050] In a non-limiting embodiment, the composite material has about 6%, about 7%, about 8%, about 9%, about 10%, about 11%, about 12%, about 13%, about 14%, about 15%, about 16%, about 17% or about 18% lower hygroscopicity than pristine zeolite.
In some embodiments, the composite material shows thermal stability up to a temperature of about 350°C - 400 °C.
[0051] In a non-limiting embodiment, the composite material shows thermal stability up to a temperature of about 350°C, about 351°C, about 352°C, about 353°C, about 354°C, about 355°C, about 356°C, about 357°C, about 358°C, about 359°C or about 400 °C.In order to enable a reproduction of the aforesaid composite material of the present disclosure, further provided herein is a method of preparing the composite material, wherein said method comprises-
mixing aromatic diamine, p-Toluenesulfonic acid monohydrate (PTSA.H2O), 1,3,5-Triformylphloroglucinol (Tp) and zeolite(s) by grinding to obtain a homogeneous mixture; and
heating the homogeneous mixture to obtain the composite material.
[0052] In some embodiments, the aforesaid method comprises-
a) grinding the aromatic diamine and the p-Toluenesulfonic acid monohydrate (PTSA.H2O) to obtain a mixture;
b) adding the 1,3,5-Triformylphloroglucinol (Tp) to the mixture and subjecting the resultant mixture to further grinding to obtain a paste;
c) adding the zeolite(s) to the paste and subjecting the paste and the zeolite to further grinding to obtain a homogeneous mixture; and
d) heating the homogeneous mixture to obtain the composite material.
[0053] In some embodiments, the aromatic diamine is selected from a group comprising 4,4-Azodianiline (Azo), Benzidine (BD), 3,3/-dimethylbenzidine (BDMe2), 3,3/-dinitrobenzidine (BD(NO2)2), 3,3-dihydroxylbenzidine (BD(OH)2), 3,3-dimethoxybenzidine (BD(OMe)2) Azo-BD, or any combination thereof.
[0054] In some embodiments, the aromatic diamine is mixed with p-Toluenesulfonic acid monohydrate (PTSA.H2O) in a ratio of about 1:1 to about 1:4.
[0055] In a non-limiting embodiment, the aromatic diamine is mixed with p-Toluenesulfonic acid monohydrate (PTSA.H2O) in a ratio of about 1:1, about 1:2, about 1:3 or about 1:4.
[0056] In some embodiments, the 1,3,5-Triformylphloroglucinol (Tp) is added to the mixture of step (a) at a ratio of about 1:2 to about 1:4.
[0057] In a non-limiting embodiment, the 1,3,5-Triformylphloroglucinol (Tp) is added to the mixture of step (a) at a ratio of about 1:2, about 1:3 or about 1:4.
[0058] In some embodiments, the grinding in step (a) is performed for about 10 minutes to about 20 minutes. In some embodiments, the grinding is under moisture free conditions.
[0059] In some embodiments, the grinding in step (b) is performed for about 15 minutes to about 30 minutes.
[0060] In some embodiments, grinding in step (c) is performed for about 15 minutes to about 30 minutes.
[0061] In some embodiments, the heating in step (d) is at a temperature of about 80°C to about 100°C for time ranging from about 12 hours to 15 hours. In some embodiments, the homogenous mixture is transferred to a glass vial and thereafter subjected to heating to obtain the composite material.
[0062] In some embodiments, the method further comprises-
allowing the composite material to cool to room temperature;
washing the cooled composite material; and
drying the washed composite material.
[0063] In some embodiments, the washing is performed with solvent(s) selected from a group comprising water, N, N-dimethylacetamide and acetone or any combination thereof; and wherein the drying is performed at a temperature of about 70°C to about 80°C.
[0064] In some embodiments, the washing is performed sequentially with water, N, N-dimethylacetamide and acetone.
Accordingly, in some embodiments, the method further comprises two or more of-
i. allowing the composite material to cool to room temperature;
ii. washing the cooled composite material with water;
iii. washing the washed composite of (ii) with N, N-dimethylacetamide;
iv. washing the washed composite of (iii) with acetone; and
v. drying the acetone washed composite material.
[0065] Accordingly, in some embodiments, the method of preparing the composite material comprises-
a) grinding the aromatic diamine and the p-Toluenesulfonic acid monohydrate (PTSA.H2O) to obtain a mixture;
b) adding the 1,3,5-Triformylphloroglucinol (Tp) to the mixture and subjecting the resultant mixture to further grinding to obtain a paste;
c) adding the zeolite(s) to the paste and subjecting the paste and the zeolite to further grinding to obtain a homogeneous mixture;
d) heating the homogeneous mixture to obtain the composite material;
e) allowing the composite material to cool to room temperature;
f) washing the cooled composite material; and
g) drying the washed composite material.
[0066] In some embodiments, the method of preparing the composite material comprises-
a) grinding the aromatic diamine and the p-Toluenesulfonic acid monohydrate (PTSA.H2O) for about 10 minutes to about 20 minutes to obtain a mixture;
b) adding the 1,3,5-Triformylphloroglucinol (Tp) to the mixture and subjecting the resultant mixture to further grinding for about 15 minutes to about 30 minutes to obtain a paste;
c) adding the zeolite(s) to the paste and subjecting the paste and the zeolite to further grinding for about 15 minutes to about 30 minutes to obtain a homogeneous mixture;
d) heating the homogeneous mixture at a temperature of about 80°C to about 100°C for about 12 hours to 15 hours to obtain the composite material;
e) allowing the composite material to cool to room temperature;
f) washing the cooled composite material with solvent(s) selected from a group comprising water, N, N-dimethylacetamide and acetone or any combination thereof; and
g) drying the washed composite material at a temperature of about 70°C to about 80°C.
[0067] Figure 4 provides a schematic representation of the TpAzo COF/zeolite composite formation and selective gas separation. The mechanochemical synthetic pathway for preparing the composite is represented in Figure 5.
The present disclosure further provides the aforesaid composite material for use in selective gas separation.
[0068] The composite material allows adsorptive uptake of a chemical species from the group comprising carbon dioxide, carbon monoxide, hydrogen, methane, oxygen, and nitrogen or any combination thereof.
[0069] The present disclosure also provides a method of selective gas separation, wherein the gas separation is performed through the composite material as described above.
[0070] Further provided herein is a device for selective gas separation comprising the composite material of the present disclosure as a sorbent.
[0071] In some embodiments, the gas that is separated is selected from a group comprising carbon dioxide, carbon monoxide, hydrogen, methane, oxygen, and nitrogen or any combination thereof.
[0072] Overall, the process of the present disclosure provides a zeolite based composite material that while retaining the functionality and properties of zeolite has improved chemical stability, high water resistance and high surface area. Also provided herein is a simple method of preparing the said composite. The product and the method of the present disclosure may have obvious variants such as but not limited to composites comprising obvious alternatives or functionally identical alternatives of the COF(s) and zeolite(s) defined herein, reliance on ratios and proportions marginally different from those described herein, leading no significant difference in the performance of the final composite, employment of a different order of method steps, reliance on slightly differing physical parameters during the method leading to no significant difference in process efficiency and post processing steps for the obtained composite. Taken together, the method of the present disclosure provides multiple advantages such as but not limited to:

- High chemical stability of the zeolite-based composite;
- High water resistance of the zeolite-based composite;
- High surface area of the zeolite-based composite;
- Applicability of the of the zeolite-based composite in selective gas separation even in conditions generally unfavourable for zeolites per se;
- Simplicity of the mechanochemical synthesis route of preparing the zeolite-based composite and therefore low production cost.

[0073] In an embodiment, the foregoing descriptive matter is illustrative of the disclosure and not a limitation. Providing working examples for all possible combinations of optional elements in the composition and process parameters is considered redundant.
[0074] While considerable emphasis has been placed herein on the particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. Those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

EXAMPLES:
Materials and methods

Zeolite 5A
[0075] This zeolite has unique selectivity, acid properties and high thermal stability, uniform pore size, definite skeleton structure, and high porosity (about 700 m2/g at about 273K). The chemical formula is Ca5Na3[(AlO2)12(SiO2)12]. xH2O. Zeolite 5A could be selective for CO2 adsorption due to the strong interactions of the quadruple moment of CO2 and the cation positioned in the zeolite structure. The size cage of calcium zeolite 5A has an internal volume of about 776 Å, formed by a cubic lattice of sodalites. The free aperture of the pore is about 4.2 Å, allowing for the passage of molecules with a kinetic diameter of about <4.9 Å.

Zeolite 13X
[0076] Zeolite NaX or commonly known as zeolite 13X is a synthetic crystalline sodium aluminosilicate and in the dehydrated form, the framework unit cell has the chemical formula Nax(AlO2)x(SiO2)192-x where, 77 = x = 96. The primary building units (PBUs) are alternating SiO4 and AlO4 tetrahedra with silicon or aluminium atoms at their centres and oxygen atoms at the vertices. Each AlO2 group in the zeolite framework introduces a negative charge that is compensated by the presence of an extra-framework sodium (Na+) ion.

EXAMPLE 1: Synthesis of TpAzo COF
[0077] About 0.15mmol (1.5eqv, 31.8mg) of 4,4’-Azodianiline (Azo) was added to about 0.825mmol (8.25 eqv, 157mg) of PTSA.H2O (p-Toluenesulfonic acid) in a mortar and mixed well with a pestle under moisture free condition. Once the mixing was properly done, about 0.1 mmol (1 eqv, 21 mg) of 1,3,5-triformylphloroglucinol (Tp) was added to the mixture followed by vigorous grinding until it yields a paste. The paste was then transferred into a glass vial which was put inside an oven to heat at about 90 °C for about 12 hours. The vial was then removed from the oven and allowed to cool down to room temperature. The obtained COF was then washed sequentially with water, N, N-dimethylacetamide and finally acetone just before drying the sample in an oven at about 90° C to obtain the TpAzo COF. The synthetic scheme and pictorial representation of the mechanochemical process are shown in Figure 1 and Figure 2.
EXAMPLE 2: Synthesis of the composite
[0078] About 0.15mmol (1.5eqv, 31.8mg) of 4,4’-Azodianiline (Azo) was added to about 0.825mmol (8.25eqv, 157mg) of PTSA.H2O in a mortar and mixed well with a pestle under moist free condition. Once the mixing was properly done, about 0.1 mmol (1eqv, 21 mg) of 1,3,5-triformylphloroglucinol (Tp) was added to the mortar followed by vigorous grinding. Then, varying amounts of Zeolite 5A - 2.5 wt% 5 wt% and 10 wt%(for different batches) were added to the paste and again ground until a complete homogeneous mixture was obtained. The final paste was then transferred into a glass vial which was put inside an oven to heat at about 90 °C for about 12 hours. The vial was then removed from the oven and allowed to cool down to room temperature to obtain the COF/zeolite composite. The COF/zeolite composite was then washed sequentially with water, N, N-dimethylacetamide and finally acetone just before drying the sample in oven before subjecting it to characterization and surface area determination studies. The mechanochemical synthetic pathway for the composite is represented in Figure 5. The schematic representation of the TpAzo COF/zeolite composite formation and selective gas separation is shown in Figure 4.

EXAMPLE 3: Thermogravimetric Analysis (TGA)
[0079] The composite as prepared in Example 2 and TpAzo COF of Example 1 alone were subjected to thermogravimetric analysis.
[0080] The TGA curves of the COF and the composites showed thermal stability up to about 400 °C. However, there was about 2% to about 8% weight loss before about 200 °C in case of the composites which is absent in the COF itself (Figure 6). This, however, is completely due to the removal of trapped H2O from zeolite. Zeolites contain a large amount of water and hence, the pristine zeolites lose water when subjected to heating and there was no other loss in the whole range of heating even up to about 900 °C.
EXAMPLE 4: IR and PXRD analysis
[0081] The composite of Example 2 and pristine zeolite and TpAzo COF of Example 1 were subjected to FTIR and PXRD analysis. The results for the FTIR and PXRD analysis are provided in Figures 7a and 7b, respectively.
[0082] The COF formation in the composition was confirmed from the comparison of IR spectra of the composite of Example 1 with the TpAzo COF IR spectrum (Figure 7a). Further, the COF formation was also confirmed from the presence of 110, 200, and 210 planes both in TpAzo COF and the composite in XRD spectra (Figure 7b).

EXAMPLE 5: Surface area Measurement (N2 Adsorption)
[0083] The surface area of the composite varies with the amount of zeolite added to the COF during the synthesis (Figure 8 and 9). The screening of said effect of the concentration of zeolite was performed with pristine zeolite and composites comprising 2.5wt%g, 5 wt%, and 10wt% of both 5A and 13X zeolites, prepared as described in Example 2. The results are depicted in the below table.
Table 1. Surface area of TpAzo COF and COF/zeolite composites
Materials Surface Area (m2/g)
TpAzo 2400
Zeolite 5A Pristine 700
TpAzo/5A_2.5 2035
TpAzo/5A_5 1700
TpAzo/5A_10 1520
Zeolite 13X Pristine 800
TpAzo/13X_2.5 2160
TpAzo/13X_5 1890
TpAzo/13X_10 1267

[0084] As evident from the porosity measurement, the surface area of the composites prepared by the mechanochemical synthesis route as described in Example 1 is higher as compared to the pristine zeolite. Surface area was found to decrease with increase in the concentration of the zeolite.

EXAMPLE 6: Hygroscopicity assessment
[0085] About 60 mg each of 5A zeolite and 13X zeolite, TpAzo/5A composite, and TpAzo/13X composite prepared as per Example 2 were kept at room temperature (about 20°C) in atmospheric humid condition to check their ability to absorb water vapor from the air.
[0086] After about 403 minutes, it was found that the COF-coated zeolites i.e. the TpAzo/5A composite and the TpAzo/13X composite adsorbed less water than their pristine counterparts (observations in Table 2, below). However, the slow water adsorption rate limits the water uptake from saturation. As time progresses, the difference in water uptake between the composites and the pristine zeolites was found to increase before the saturation of water adsorption by the materials.

Table 2. Water uptake capacity of composite material compared to pristine zeolite
Materials Water uptake capacity (gm/gm)
5A zeolite 0.0570
TpAzo/5A 0.0497
13X zeolite 0.0552
TpAzo/13X 0.0489

[0087] The TpAzo/5A composite and the TpAzo/13X composite therefore showcased about 12.8% and about 11.4% w/w reduced water uptake, respectively, as compared to their pristine zeolite counterparts, indicating their improvement in hydrophobicity (Figure 10).

EXAMPLE 7: Assessment of chemical stability in Hydrochloric acid (HCl)
[0088] To check the chemical stability of the composite material as prepared in claim 1, the composite material was exposed to or treated with about10 ml of 3N HCl overnight. While performing comparative studies, it was found that pristine zeolite was entirely soluble in the HCl and lost its structural motif in the presence of acids. However, the composite material retained its structural and CO2 uptake ability even after treatment with 3N HCl overnight (Figure 11). Exposure to the strong acid, however, was found to lead to a certain decrement in the CO2 uptake capacity (Figure 12) and about 25% to about 40% weight loss compared to the composite in the form as-synthesized. Table 3 depicts the impact of the treatment with 3N HCl on the CO2 uptake capacity of the composite material.

Table 3. CO2 uptake capacity of composite material TpAzo/5A before and after treatment with 3N HCl compared to the pristine 5A zeolite.
Materials CO2 uptake data (0°C) (cc/g)
5A zeolite 138
5A zeolite_3(N) HCl NA (Completely solubilized)
TpAzo/5A 100
TpAzo/5A _3(N) HCl 59

[0089] Therefore, unlike pristine zeolite which was completely solubilized in the presence of an acid, even though decreased, the composite of the present disclosure retained its CO2 uptake ability even after treatment with a strong acid.

EXAMPLE 8: Assessment of chemical stability in formic acid (HCOOH)
[0090] In continuation to Example 7, in order to re-assess stability of the composite material in acidic environment, the composite was exposed to about 0.1 (M) HCOOH for about 10 hours.
[0091] It was found that TpAzo/5A showcased excellent acid stability in 0.1 (M) HCOOH, while the CO2 uptake capacity remaining unaltered. However, in the presence of higher concentration of acid i.e. about 0.5 (M) HCOOH, the CO2 uptake capacity decreased to about 81 cc/g from about 114 cc/g that was observed upon exposure to 0.1 (M) HCOOH (Table 4, Figure 13).

Table 4. CO2 uptake capacity of composite material TpAzo/5A before and after treatment with 0.1(M) HCOOH and 0.5(M) HCOOH for 10 hours, respectively.
Materials CO2 uptake data (0°C) (cc/g)
TpAzo/5A 114
TpAzo/5A_0.1(M) HCOOH 111
TpAzo/5A_0.5(M) HCOOH 81

[0092] Therefore, unlike pristine zeolite which was completely solubilized in the presence of an acid, even though slightly decreased, the composite of the present disclosure retained its CO2 uptake ability even in an acidic environment.