Description:FIELD OF THE INVENTION
[0001] The present disclosure relates to a method of converting carbon dioxide (CO2) captured in amine solution to formic acid production. The present disclosure also relates to a resin supported iridium-complex catalyst anchored with ethylene diamine loaded polystyrene/trityl resin for CO2 hydrogenation to formic acid production.

BACKGROUND OF THE INVENTION
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] Carbon, which is present in all known life forms, will continue to be needed to support human progress, but we must manage it within a closed loop system to make it sustainable. For the society to end its reliance on fossil fuels, CO2 must be treated as a precious resource, and to be recycled and reuse. As a result, capturing CO2 emissions and combining them with green hydrogen to chemicals/fuels production is gaining significant attention as an accelerated path toward a circular economy. Existing CO2 utilization strategies, based on the use of pure CO2, lead to relatively high cost for e-fuels and commodity chemicals. Once captured using various technologies, CO2 is desorbed and compressed for either storage by carbon capture and storage (CCS)) route or production of value-added products through the route known as carbon capture and utilization (CCU). Among various products that can be produced from CO2, methanol and formic acid are the two most important bulk chemicals having many industrial applications. For example, they can be used directly as fuels/fuel additives or to generate H2 on demand at low temperatures (<100 °C), making them attractive hydrogen carriers (12.6 and 4.4 wt % H2 in methanol and formic acid, respectively). Although value-added chemicals and fuels such as CH4, syngas, and methanol, can be produced through carbon capture and conversion (CCC), the high cost associated with CO2 compression and transportation remains a significant challenge for the CCC process. To make the CCC process more economically attractive and realize its potential on large scale production, a novel Integrated CO2 Capture and Conversion (ICCC) process is proposed and has been a hot research topic. Thus far, various kinds of the ICCC processes have been developed by combinations of different CO2 capture and CO2 conversion approaches, such as ionic liquids based hybrid process (Lia, solvent-based CO2 capture and electrolysis process high-temperature electrochemistry-based CO2 transport membranes, hybrid CO2 capture and photocatalytic conversion process by using a novel hybrid sorbent/photocatalyst, and hybrid CO2 capture (based on solid CO2 sorbent) and thermocatalytic conversion process in reducing atmosphere is used for sorbent regeneration in the ICCC, rather than a CO2-rich atmosphere commonly recommended in the conventional CO2 capture process using sorbents. As a result, the regeneration temperature of sorbents can be significantly decreased, thus saving good amount of energy and even making it highly possible to operate isothermally in the ICCC. Few homogeneous catalyst system of this pathway have been discovered for such reaction and reasonable productivities have been achieved. However, manufacturers are hesitant to use them for practical process, because of the concern of the separation of catalyst from the reaction mixture. Additionally, all the homogeneous catalysts used in the process need a base reagent (such as ammonia) to promote the catalytic performance. Finally, the homogeneous catalyst not only catalyzes the formate formation but also promote the reverses’ reaction and decompose the product back to the starting materials owing to its intrinsic thermoneutral reaction pathways. Because of these drawbacks, the heterogeneous catalytic route has been deliberated as the preferred solution of commercial CO2 hydrogenation to formic acid through integrated capture and utilization process.
[0004] Himeda group developed [Kanega et al., ACS Catal., 2017, 7, 10, 6426–6429] ligands derived from deprotonated picolinamide and its derivatives for preparing a series of iridium complexes as homogenous catalytic system. These catalysts effectively hydrogenated CO2 which is introduced as gas feed in the reaction system. Anionic amide in the ligand exhibits high catalytic activity owing to its high electron donating ability as well as resonance effect of phenolic -O towards to Ir-center. Later group led by Ertem re-confirms that deprotonated OH group in picolinamide derivative is the origin for high active iridium catalyst [Nijamudheen et al., ACS Catal., 2021, 11, 5776-5788]. Based on the success of picolinamide and its derivatives-based ligands and their respective iridium complex, Tensi et al [Inorg. Chem., 2022, 61, 10575-10586] heterogenized such complex using meso-porous silica support. It is noteworthy to mention that catalyst was tested in batch condition using CO2 and hydrogen as a gas feed in presence of aqueous solution of organic base. Maximum formate concentration was obtained using such immobilized catalyst system was 0.273 M owing to its degradation and this phenomenon was established by Rodriguez et al [Chemistry - A European Journal (2021), 27, 6, 2050-2064]. Consequently, it was proposed by Tensi et al. [Inorg. Chem. 2022, 61, 10575-10586] to develop ligand system with restricted amide bond rotation. Moreover, it is also imperative to develop integrated CO2 capture and conversion to formic acid to save additional energy input for de-capturing CO2 from absorbed solvent. Bhardwaj et al. [Chem. Commun., 2022, 58, 11531-11534] developed Ir(III)-N-heterocyclic carbene based homogenous catalyst system for integrated CO2 capture and conversion to formic acid. Being a homogenous system, it suffers usual disadvantage of catalyst and product separation for continuous operation. Considering all the shortcomings, it is prudent to develop heterogenized version of amide-ligated Ir-complex that restrict amide bond rotation for integrated CO2 capture and its conversion to formic acid. Both polystyrene and trityl based resins are hydrophobic in nature, it might provide cavity in water solution that can protect in degrading the structure through electrophilic reaction. Moreover, the structure of resin (polystyrene -cross linked and trityl) are bulky in nature it may provide further restriction in amine bond rotation to degrade intermolecularly. Keeping all these minds, in the present disclosure, resin supported iridium complex anchored with various amide -comprises bulky substitution ligand are employed for integrated CO2 capture and conversion to formic acid production.
OBJECTS OF THE INVENTION
[0005] An objective of the present disclosure is to provide a method of converting carbon dioxide captured in amine solution to formic acid.
[0006] Another objective of the present disclosure is to provide a resin supported iridium-complex catalyst anchored with ethylene diamine loaded polystyrene/trityl resin of formula (GS-1) for carbon dioxide-captured in amine solution to formic acid production.
[0007] Another objective of the present disclosure is to provide a resin supported iridium-complex catalyst anchored with ethylene diamine loaded polystyrene/trityl resin of formula (GS-2) for carbon dioxide-captured in amine solution to formic acid production.
[0008] Yet another objective of the present disclosure is to provide a resin supported iridium-complex catalyst anchored with ethylene diamine loaded polystyrene/trityl resin of formula (GS-3) for carbon dioxide-captured in amine solution to formic acid production

SUMMARY OF THE INVENTION
[0009] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in Detailed Description section. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
[0010] An aspect of the present disclosure is to provide a method of converting carbon dioxide captured in amine solution to formic acid comprising: a) charging 0.25 M to 2 M of an amine loaded with carbon dioxide (0.8 mole CO2/mole of amine) and 1 to 1000 micro-mol/gram of a resin supported iridium-complex catalyst to form a first reaction mixture and sealed the autoclave; b) pressurizing with H2 (1-60 bar) to the first reaction mixture of step a) in the sealed autoclave to obtain a second reaction mixture; c) heating the second reaction mixture under condition to form an intermediate liquid; and d) cooling the intermediate liquid followed by acidified with 1N of an acid to obtain formic acid.
[0011] Another aspect of the present disclosure is to provide a resin supported iridium-complex catalyst anchored with ethylene diamine loaded polystyrene/trityl resin of formula (GS-1) for carbon dioxide-captured in amine solution to formic acid production comprising:

(GS-1)
wherein,
R= H, Me, Et, OMe, OH, NMe2, NH2, NHMe; and
L= Cl, OH2.
[0012] Another aspect of the present disclosure is to provide a resin supported iridium-complex catalyst anchored with ethylene diamine loaded polystyrene/trityl resin of formula (GS-2) for carbon dioxide-captured in amine solution to formic acid production comprising:

(GS-2)
wherein,
R=H, Me, Et, OMe, OH, NMe2, NH2, NHMe;
L= Cl, OH2; and
R’= H, Me, Et, OMe, OH, NMe2, NH2, NHMe.
[0013] Another aspect of the present disclosure is to provide a resin supported iridium-complex catalyst anchored with ethylene diamine loaded polystyrene/trityl resin of formula (GS-3) for carbon dioxide-captured in amine solution to formic acid production comprising:

(GS-3)
wherein,
R’’= Me, Ph, PhOMe, Bu, iPr;
R= H, Me, Et, OMe, OH, NMe2, NH2, NHMe; and
L= Cl, OH2.
[0014] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The accompanying drawings are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.
[0016] Figure 1: illustrates HPCL of crude reaction mixture using Icat-1.

DETAILED DESCRIPTION OF THE INVENTION
[0017] The following is a detailed description of embodiments of the disclosure. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0018] Unless the context requires otherwise, throughout the specification which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense that is as “including, but not limited to.”
[0019] As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
[0020] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable.
[0021] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it is individually recited herein.
[0022] All processes described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0023] The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.
[0024] The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus, if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.
[0025] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
[0026] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description that follows, and the embodiments described herein, is provided by way of illustration of an example, or examples, of particular embodiments of the principles and aspects of the present disclosure. These examples are provided for the purposes of explanation, and not of limitation, of those principles and of the disclosure.
[0027] It should also be appreciated that the present invention can be implemented in numerous ways, including as a system, a method or a device. In this specification, these implementations, or any other form that the invention may take, may be referred to as processes. In general, the order of the steps of the disclosed processes may be altered within the scope of the invention.
[0028] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
[0029] An embodiment of the present disclosure provides a method of converting carbon dioxide captured in amine solution to formic acid comprising: a) charging 0.25M to 2 M of an amine loaded with carbon dioxide (0.8 mole CO2/mole of amine) and 1 to 1000 micro-mol/gram of a resin supported iridium-complex catalyst to form a first reaction mixture and sealed the autoclave; b) pressurizing with H2 (1-60 bar) to the first reaction mixture of step a) in the sealed autoclave to obtain a second reaction mixture; c) heating the second reaction mixture under condition to form an intermediate liquid; and d) cooling the intermediate liquid followed by acidified with 1N of an acid to obtain formic acid.
[0030] In an embodiment, the amine is selected from a group consisting of 1,4-diazabicyclo[2.2.2]octane (DABCO), 1,5,7-triazabicyclo(4.4.0)dec-5-ene (TBD), 7-methyl-1,5,7-triazabicyclo(4.4.0)dec-5-ene (MTBD), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), 1,1,3,3-tetramethylguanidine (TMG), quinuclidine, 2,2,6,6-tetramethylpiperidine (TMP), pempidine (PMP), tributlyamine, triethylamine, 1,4-diazabicyclo[2.2.2]octan (TED) and combination thereof. Preferably, the amine is DABCO. The amine has a concentration of 1 M.
[0031] In an embodiment, the condition in step c) includes temperature in the range of 100-180°C for a period of 1-24 hrs with stirring at a speed of 400-600 rpm. Preferably, the temperature is 150°C for a period of 6-12 hrs with a stirring at a speed of 500 rpm.
[0032] In an embodiment, the intermediate liquid of step d) is cooled at a temperature in the range of 15-35 °C. Preferably, the cooling temperature is 20-35 °C
[0033] In an embodiment, the acid is selected from a group consisting of hydrochloric acid, nitric acid, sulphuric acid and combination thereof. Preferably, the acid is hydrochloric acid.
[0034] In an embodiment, the acid is added to maintain the pH in the range of 2 to 4. Preferably, the pH is 3.
[0035] Another embodiment of the present disclosure provides a resin supported iridium-complex catalyst anchored with ethylene diamine loaded polystyrene/trityl resin of formula (GS-1) for carbon dioxide-captured in amine solution to formic acid production comprising:

(GS-1)
wherein,
R= H, Me, Et, OMe, OH, NMe2, NH2, NHMe; and
L= Cl, OH2.
Preferably, the catalyst (GS-1) is N,N chelating pyridine derivative based amido complex anchored with ethylene diamine loaded polystyrene/ trityl resin.
[0036] In an embodiment, the catalyst (GS-1) has a chemical structure represented by:

(Icat-1).
[0037] Another embodiment of the present disclosure provides a resin supported iridium-complex catalyst anchored with ethylene diamine loaded polystyrene/trityl resin of formula (GS-2) for carbon dioxide-captured in amine solution to formic acid production comprising:

(GS-2)
wherein,
R= H, Me, Et, OMe, OH, NMe2, NH2, NHMe;
L= Cl, OH2; and
R’= H, Me, Et, OMe, OH, NMe2, NH2, NHMe.
Preferably, the catalyst (GS-2) is N,N chelating quinoline derivative based amido complex anchored with ethylene diamine loaded polystyrene/ trityl resin.
[0038] In an embodiment, the catalyst (GS-2) is selected from the chemical structure represented by:

(Icat-2).
[0039] Another embodiment of the present disclosure provides a resin supported iridium-complex catalyst anchored with ethylene diamine loaded polystyrene/trityl resin of formula (GS-3) for carbon dioxide-captured in amine solution to formic acid production comprising:

(GS-3)
wherein,
R’’= Me, Ph, PhOMe, Bu, iPr;
R= H, Me, Et, OMe, OH, NMe2, NH2, NHMe; and
L= Cl, OH2.
Preferably, the catalyst (GS-3) is N, P chelating phosphino-derivative based amido complex anchored with ethylene diamine loaded polystyrene/ trityl resin.
[0040] In an embodiment, the catalyst (GS-3) has a chemical structure represented by:

(Icat-3).
CO2 Hydrogenation using Supported Ir-Catalysts:
[0041] Further to get integrated carbon capture and utilization through formic acid production, we developed supported resin-based iridium complex. Here various ligands are developed that are covalently bind using amide bond through ethylene diamine anchored in various commercial resins (Polystyrene and trityl resin) and followed by iridium complex was reacted to exchange with supported ligands. Iridium loading was performed by taking 1 mmol/g of iridium dimercomplex [Cp*IrCl2]2 into the resin that offer TON value of >8000 for formic acid production at 150 oC and 40 bar of hydrogen pressure for 0.8 mol/mol of CO2 loaded amine solution after 6 hrs of reaction. After the reaction amine has been regenerated (Scheme 1).

Scheme 1: Ir-complexes (heterogenized) based catalyst employed for CO2 hydrogenation to Formic acid.
[0042] CO2 hydrogenation to Formic acid: In a typical procedure, a 250 ml autoclave was charged with 1 M DABCO (60 ml) and an iridium complex (20 mg). The autoclave was closed and pressurized with carbon dioxide (1-40 bar) to capture CO2 and then depressurize the reactor. Collected CO2 captured amine (DABCO) was subjected to hydrogenation (using 1-60 bar H2 pressure) reaction in presence of Poylstyrene/trityl resin supported Ir-complex. The reaction was conducted at 100-180 0C for a duration of 1-24 hours. The autoclave was depressurized carefully, and the liquid was acidified with 1N HCl. The formation of product was analyzed by Agilent HPLC using C18 column.
[0043] Catalyst Preparation: To a solution of [Cp*IrCl2]2or Cp*Ir(OH2)3 SO4 in water was added various polystyrene supported heterocyclic ligand and the mixture was stirred at room temperature for 16 hours. The solution was filtered, and the filtrate was dried under reduced pressure to afford the Iridium catalyst-supported with polystyrene resin.
[0044] 13C CPMAS NMR (150 MHz) was performed for Icat-1, Icat-2 and Icat-3 characterization. 13C CPMAS Peak observed at around 130 ppm (C peak of benzene ring in PS-resin and trityl-resin), 40 ppm (C-peak of methylene group in ethylene diamine) and 200 ppm (C peak in >C=O) respectively confirms the presence of resin, ethylene diamine and its amide derivatives in the supported ligand structure. After loading with [Cp*IrCl2]2 complex with resin supported ligands, characteristics peak observed at 13 ppm (C peak of methyl group in CP*) and 88 ppm (C-peak of methylene group in CP* ring) further confirms Ir-loaded supported catalyst structure.

ADVANTAGES OF THE PRESENT INVENTION
[0045] A series of resin-supported iridium complex integrated CO2 capture were synthesized and discloses conversion to formic acid. The catalysts were prepared in a single step by reacting the ligand with the iridium precursor. The captured CO2 in amine solution was directly employed for CO2 reduction to formic acid at 40 bar hydrogen pressure and 150 °C. This process does not require additional de-capturing step to generate CO2 stream for formic acid production. Iridium catalysts reported here-in are found to be very active and completely selective towards CO2 hydrogenation to formic acid and no formation of side products were observed.
[0046] This is an integrated process and it does not require addition step to de-capture CO2 from amine solution for the catalytic hydrogenation of CO2 to formic acid. It converts CO2-captured in amine solution to formic acid and hydrogen atmosphere.
[0047] This is first report of resin-supported Ir-complexes that have been utilized for integrated capture and utilization for Formic acid production.
[0048] These supported catalysts could effectively produce upto 0.5 M formic acid concentration out of 0.8 M CO2 loaded amine and it helps to achieve >60% efficiency of CO2 utilization.
[0049] These supported catalysts perform in amine-water solution and proving their applicability in real system.
[0050] Prepared catalysts are easy for synthesis and purification and simple filtration and washing are sufficient for obtaining final supported catalyst. Hence these catalysts are scalable.
[0051] While the foregoing describes various embodiments of the disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.
EXAMPLES
[0052] The present invention is further explained in the form of following examples. However, it is to be understood that the following examples are merely illustrative and are not to be taken as limitations upon the scope of the invention.
Example 1
[0053] A 250 mL autoclave was charged with 1M DABCO (60 mL) loaded with CO2 (0.8 mol of CO2/mol of DABCO) and Icat-1 (GS-1). The autoclave was sealed and pressurized with H2 at 40 bar. It was heated to 150 °C and stirred (500 rpm) for 6-12 h. Cooled to room temperature and the liquid was carefully acidified with HCl to pH=3. The concentration of formic acid was analysed by HPLC using C-18 column (Figure. 1). Formic acid concentration: 0.44 M.
Example 2
[0054] A 250 mL autoclave was charged with 1M DABCO (60 mL) loaded with CO2 (0.8 mol of CO2/mol of DABCO) and Icat-2 (GS-2). The autoclave was sealed and pressurized with H2 at 40 bar. It was heated to 150 °C and stirred (500 rpm) for 6-12 h. Cooled to room temperature and the liquid was carefully acidified with HCl to pH=3. The concentration of formic acid was analysed by HPLC using C-18 column. Formic acid concentration: 0.35 M.
Example 3
[0055] A 250 mL autoclave was charged with 1M DABCO (60 mL) loaded with CO2 (0.8 mol of CO2/mol of DABCO) and Icat-3 (GS-3). The autoclave was sealed and pressurized with H2 at 40 bar. It was heated to 150 °C and stirred (500 rpm) for 6-12 h. Cooled to room temperature and the liquid was carefully acidified with HCl to pH=3. The concentration of formic acid was analysed by HPLC using C-18 column. Formic acid concentration: 0.48 M.
[0056] The Performance of the synthesized catalysts was evaluated in a batch reactor and CO2 conversion and formic acid selectivity were determined experimentally as shown in Table 1.
[0057] Table 1: Catalysts with formic acid concentration.
Example Catalyst HCOOH (M) Feed used
Icat-1
0.44 CO2-abosrbed in amine solution of present invention
Icat-2
0.35 CO2-abosrbed in amine solution of present invention
Icat-3
0.48 CO2-abosrbed in amine solution of present invention
Ref catalyst
Ir_PicaSi_SiO2
0.273 CO2 gas
[Tensi et al., Inorg. Chem. 2022, 61, 27, 10575–10586

[0058] The foregoing examples are merely illustrative and are not to be taken as limitations upon the scope of the invention. Various changes and modifications to the disclosed embodiments will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the scope of the invention.
, Claims:1. A method of converting carbon dioxide captured in amine solution to formic acid comprising:
a) charging 0.25M to 2 M of an amine loaded with carbon dioxide (0.8 mole CO2/mole of amine) and 1 to 1000 micro-mol/gram of a resin supported iridium-complex catalyst to form a first reaction mixture and sealed the autoclave;
b) pressurizing with H2 (1-60 bar) to the first reaction mixture of step a) in the sealed autoclave to obtain a second reaction mixture;
c) heating the second reaction mixture under condition to form an intermediate liquid; and
d) cooling the intermediate liquid followed by acidified with 1N of an acid to obtain formic acid.
2. The method as claimed in claim 1, wherein the amine is selected from a group consisting of 1,4-diazabicyclo[2.2.2]octane (DABCO), 1,5,7-triazabicyclo(4.4.0)dec-5-ene (TBD), 7-methyl-1,5,7-triazabicyclo(4.4.0)dec-5-ene (MTBD), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), 1,1,3,3-tetramethylguanidine (TMG), quinuclidine, 2,2,6,6-tetramethylpiperidine (TMP), pempidine (PMP), tributlyamine, triethylamine, 1,4-diazabicyclo[2.2.2]octan (TED) and combination thereof.
3. The method as claimed in claim 1, wherein the amine has a concentration of 1 M.
4. The method as claimed in claim 1, wherein the condition in step c) includes temperature in the range of 100-180°C for a period of 1-24 hrs with stirring at a speed of 400-600 rpm.
5. The method as claimed in claim 1, wherein the intermediate liquid of step d) is cooled at a temperature in the range of 15-35 °C.
6. The method as claimed in claim 1, wherein the acid is selected from a group consisting of hydrochloric acid, nitric acid, sulphuric acid and combination thereof.
7. The method as claimed in claim 1, wherein the acid is added to maintain the pH in the range of 2 to 4.
8. A resin supported iridium-complex catalyst anchored with ethylene diamine loaded polystyrene/trityl resin of formula (GS-1) for carbon dioxide-captured in amine solution to formic acid production comprising:

(GS-1)
wherein,
R= H, Me, Et, OMe, OH, NMe2, NH2, NHMe; and
L= Cl, OH2.
9. The catalyst as claimed in claim 8, wherein the catalyst (GS-1) has a chemical structure represented by:

(Icat-1).
10. A resin supported iridium-complex catalyst anchored with ethylene diamine loaded polystyrene/trityl resin of formula (GS-2) for carbon dioxide-captured in amine solution to formic acid production comprising:

(GS-2)
wherein,
R= H, Me, Et, OMe, OH, NMe2, NH2, NHMe;
L= Cl, OH2; and
R’= H, Me, Et, OMe, OH, NMe2, NH2, NHMe.
11. The catalyst as claimed in claim 10, wherein the catalyst (GS-2) is selected from the chemical structure represented by:

(Icat-2)
12. A resin supported iridium-complex catalyst anchored with ethylene diamine loaded polystyrene/trityl resin of formula (GS-3) for carbon dioxide-captured in amine solution to formic acid production comprising:

(GS-3)
wherein,
R’’= Me, Ph, PhOMe, Bu, iPr;
R= H, Me, Et, OMe, OH, NMe2, NH2, NHMe; and
L= Cl, OH2.
13. The catalyst as claimed in claim 12, wherein the catalyst (GS-3) has a chemical structure represented by:

(Icat-3).