A METHOD OF GRAPHENE ENHANCED WITH MULTIPLE DOPANTS FOR CO2 CONVERSION: INSIGHTS INTO FORMIC ACID PRODUCTION AND ORGANIC TRANSFORMATIONS

Abstract

This invention introduces a functionalized, graphitic carbon-based photocatalyst designed for effective solar-driven regeneration of the coenzymes NADH and NADPH, essential in numerous biological redox reactions. By doping boron and fluorine into graphitic carbon nitride, this catalyst achieves efficient NAD(P)+ photoreduction under physiological conditions, enabling an integrated approach to photochemical and catalytic processes. This metal-free photocatalyst, labeled as BFGCN-x, achieves high regeneration yields for NADH (61.89%) and NADPH (59.84%) and facilitates acetalization reactions without the need for Lewis or Brønsted acids. This development represents a significant step toward sustainable photocatalysis, supporting both coenzyme regeneration and advanced chemical synthesis.

Specification

DESC:FIELD OF THE INVENTION
The present invention relates to a method of graphene enhanced with multiple dopants for CO2 conversion: insights into formic acid production and organic transformations. A heteroatom-doped graphene-based photocatalyst for CO2 conversion, where nitrogen (N), boron (B), and selenium (Se) are doped into a graphene lattice to enhance catalytic activity for formic acid production and organic transformations.
BACKGROUND OF THE INVENTION
References which are cited in the present disclosure are not necessarily prior art and therefore their citation does not constitute an admission that such references are prior art in any jurisdiction. All publications, patents and patent applications herein are incorporated by reference to the same extent as if each individual or patent application was specifically and individually indicated to be incorporated by reference.
Approximately, 80% of the energy supply in the world belongs from the fossil fuels which come from depletion of fossils fuel and results in increasing atmospheric carbon dioxide level, which leads to global warming and greenhouse effect.1 After industrial revolution, the global annual temperature of the earth increased to 1oC. In the 1980s era, the temperature rises on an average of 0.07 oC in every 10 years. But in last 40 years it is increasing around 0.18 oC per decades.2,3 This alarming increment of the global temperature is due to increasing global consumption day by day causes depletion or burning of fossil fuels (like coal, gasoline, oil, natural gas, etc.) which results in the heating of the earth, i.e., global warming.4-6 These gases like carbon dioxide and other pollutants collected in the atmosphere absorb the solar radiation and bounces off the radiation to the earth surface, which causes heating of earth surface (global warming).7 Nowadays, global warming directly attributed to activities of human being for example (i) generation of electricity via burning of fossil fuels, (ii) manufacturing goods in industries leads to emissions of several gases, (iii) cutting down of forest, which causes emissions of carbon, which they have been stored. Since, forest absorbs carbon dioxide from the atmosphere; cutting them down will lead to restrict the ability of nature to maintain the level of carbon dioxide in the atmosphere8, (iv) increasing the use of transportation which causes emission of major greenhouse gases, (v) excessive use of fertilizer and manure9, (vi) cattle also produces methane in their rumen which can be expelled out causes' greenhouse effect, etc.10 Therefore, human activities will lead to global warming. Due to global warming, change in temperature takes place which also causes rainfall which will leads to numerous recurrent storms, drought in various regions, melting of glaciers, etc.11,12 That's why global warming is serious threats which have to be minimized in order to protect the global atmosphere. However, this threat can only be reduced by fixing or by reducing the atmospheric carbon dioxide into some beneficial chemicals and fuels.13 Hence, with the help of solar radiation we can fix carbon dioxide artificially to produce desirable chemical fuels.14 For both practical and fundamental point of view, photocatalytic reactions have great importance. Photocatalytic reaction like splitting of water, oxidation of organic chemicals, synthesis of organic chemicals, reduction of carbon dioxide has been performed more frequently these days.15-17 These stereotypical photocatalytic reactions are performed with the help of heterogeneous photocatalyst which is metal free organic compound, semiconductor having suitable band gap to absorb desirable wavelength of light.18 To treat this stereotypical catalysis, artificial photosynthesis is an advance platform which traps the solar radiation and converts into valuable fuels like formic acid which is a bulk and energy carrier in industries these days.19 The platform mimics the natural phenomenon of photosynthesis (natural photosynthesis). Furthermore, the natural enzymes are chemo/regio-selective that's why they catalysed CO2 conversion more efficiently.20 Various enzymes like remodeled nitrogenize, formate dehydrogenase (FDH) and carbonic anhydrases, etc. have been used for this conversion process. FDH have small axis length of 3.8 nm, NADH dependent and have electronegativity among all enzymes.21 Therefore, it attracts huge interest in the conversion process. Besides this, FDH attains catalytic turn over, which requires nicotinamide co-factor (NAD+).22 Apart from CO2 fixation, molecular frameworks also play a crucial role in organic chemistry. From last few decades, reactions involved free radical played vital role in construction of molecular frameworks because of various methods for generating free radicals as an intermediate to tackle organic reactions (molecular frameworks).23,24 The moiety called 1,3-oxathiolane-2-thiones shows many activities like antifungal, neuroprotective, antibacterial, etc. that's why it is present in various biological active molecules and in natural products.25 Additionally, 1,3-oxathiolane-2-thiones are an important intermediate in material science. However, the ring-opening mechanism involved in the formation of cyclic thiocarbonates, catalysed by alkali metals, which limits their synthetic applications because of some drawbacks like high loading of catalyst, pressure requirements, low yield, low efficiency and regio-isomeric products formation.26 Therefore, development of alternative method for synthesis of 1,3-oxathiolane-2-thiones will be considerable contribution to this field. Styrenes are effortlessly accessible organic substrates. However, many studies have been investigated for di-functionalization of styrenes via organic transformation.27 Recently, by photo-redox catalysis many anionic species are converted into corresponding radicals.28,29 Additionally, photo-redox catalysis is also found attractive because of its capability of dioxygen (O2) activation in under visible light source for catalysing various organic reactions, i.e. functionalization.30,31 Moreover, three-dimensional porous network of graphene is desirable because of their high conductively, high surface area and porosity.32 Introduction of heteroatoms into native graphene is an effective strategy to enhance the specific power of capacitance and energy density.33,34 Also, heteroatom doped graphene provides turbo surface redox reactions because of insertion of heteroatoms in carbon lattice which fortify electronic conductively. Thus, the most pre-owned method for introduction of heteroatoms in graphene was based on direct solid-state reaction between RGO and heteroatoms.35 However, several modifications have been done in this method in order to obtain the desirable morphology. For example, Hui. et al. used aerogel of graphene which was prepared by hydrothermal method followed by freeze drying.36 Yeom et al. also used ultrasonicated solution of RGO and boron source (B2O3) followed by thermal annealing for homogenous doping of boron into graphene sheets in order to get high surface area.37 Recently, controlled sublimation technique has been used for introduction of dopants into sheets of graphene.38 However, an interesting method for introduction of heteroatoms into a graphene sheet is thermal decomposition at high temperature with heteroatoms, which causes surface precipitation by trapping heteroatoms.39 Herein, we reported thermal decomposition of heteroatoms like nitrogen (N), boron (B), and selenium (Se) in the carbon lattice of graphene at high temperature, which enhance its electronic conductively [fig. 1 (ii)] and energy density in order to promote excellent fixation of CO2 into formic acid and formation of molecular framework, i.e., biological active molecule like 1,3-oxathiolane-2-thiones under visible light source [as shown in figure 1 (i)].
Several patents issued for graphene or dopanings but none of these are related to the present invention. Patent KR101613558B1 relates to graphenes and, more particularly, to a doping method for graphene layers and doped graphenes. The present invention provides a method of manufacturing a semiconductor device, comprising: forming a graphene layer on a catalytic metal layer; Positioning a support layer comprising a dopant on the graphene layer; Removing the catalytic metal layer; Doping the graphene layer with a dopant; Positioning the substrate on the doped graphene layer; And removing the support layer.
Another patent KR101698228B1 relate to the use of graphene as a transparent conductive coating. In certain embodiments, the graphene thin film is a large area heterostructure-epitaxially grown on the catalyst thin film from a hydrocarbon gas such as C 2 H 2 , CH 4, and the like. The graphene thin film in some embodiments may be doped or undoped. In some embodiments, the formed graphene foil may be peeled from the carrier substrate and transferred to the receiving substrate of the intermediate or final product. The grown, peeled, and transferred graphene may have low sheet resistance (e.g., less than 150 OMEGA / & squ & at doping) and high transmittance (e.g., at least in the visible and infrared regions).
Another patent CN109569691B relates to a preparation method of boron-doped carbon nitride and a product and application thereof. A mode of carrying out hydrothermal reaction on melamine and boric acid promotes boron atoms and melamine to carry out chemical reaction so that boron and carbon nitrogen elements form atomic-level mixing on one hand, and carries out hydrothermal reaction on the melamine in an acid environment so that the melamine can form a supermolecular structure, which is beneficial to the separation of a carbon nitride lamellar structure in the subsequent roasting process; and then roasting the precursor synthesized by the reaction to prepare the boron-doped carbon nitride which is uniformly doped and has a thinner lamellar structure. The boron-doped carbon nitride prepared by the method has the advantages of uniform element doping, thinner lamella, better photocatalytic performance, simple preparation operation and lower difficulty, and is suitable for large-scale production.
Another patent CN104488117B report a kind of heteroatomic carbon framework of doping, and it functions simultaneously as the conductive network and polysulfide fixative for lithium sulphur negative electrode. The carbon of the doping is formed with elemental sulfur and/or sulphur compound and is chemically bonded. This can significantly suppress the diffusion of more lithium sulfides in the electrolyte, so as to cause high capability retention and high coulombic efficiency.
Another patent US8354323B2 method of making an electronic device, comprising: applying a first dopant species functional group to a graphene substrate in a first predetermined pattern to form a first doped region of the electronic device; and applying a second dopant species functional group in a second predetermined pattern to the graphene substrate patterned with the first dopant species functional group to form a second doped region of the electronic device, wherein the second predetermined pattern is at least partially determined by the application of the first dopant species functional group.
Another patent US9728605B2 relates to a roll-to-roll doping method of a graphene film and a graphene film doped by the method, in particular, to a roll-to-roll doping method, which includes doping the graphene film by immersing the graphene film in a solution containing a dopant and passing the graphene film through the solution by using a roll-to-roll process, a graphene film doped by the method, and a device using the same.
OBJECTS OF THE INVENTION
Main object of the present invention is graphene enhanced with multiple dopants for CO2 Conversion: Insights into Formic Acid Production and Organic Transformations.
Another object of the present invention is to develop a solar-driven photocatalyst for coenzyme regeneration.
Another object of the present invention is to utilize a metal-free doped graphene system.
Another object of the present invention is to enable coenzyme regeneration under physiological conditions.
Another object of the present invention is to advance sustainable photocatalysis in organic synthesis.
Another object of the present invention is to optimize catalytic performance for industrial applications.
SUMMARY OF THE INVENTION
This summary is provided to introduce a selection of concepts, in a simplified format, that are further described in the detailed description of the invention.
This summary is neither intended to identify key or essential inventive concepts of the invention and nor is it intended for determining the scope of the invention.
To further clarify advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawings.
The synthesized N@B@Se@Graphene was prepared via a solid-phase reaction at high temperature. First, 1g of chitosan (as a nitrogen source), 500 mg of selenium dioxide, and 500 mg of boric acid were thoroughly ground together and sealed in a crucible at 1000 ? for 2 hours. The calcinated product was then dissolved in water, filtered, and washed multiple times with acetone. This process successfully doped heteroatoms into the native carbon lattice of graphene. Similar procedures were used to prepare N@Graphene, B@N@Graphene, and Se@N@Graphene, as detailed in the ESI.
Herein enclosed a method of graphene enhanced with multiple dopants for CO2 conversion comprising the steps of:
fascinating the synthesized N@B@Se@Graphene through solid phase reaction method at high temperature;
grounding 1g chitosan (source of nitrogen), 500 mg selenium dioxide and 500 mg boric acid and kept in a sealed crucible at 1000 ? for 2 hours;
dissolving the calcinated product in water, filtered and washed repeatedly with acetone;
resulting in doping of heteroatoms in native carbon lattice of graphene; and
also fascinating the procedure of N@Graphene, B@N@Graphene, and Se@N@Graphene was also fascinated through solid phase reaction.
The method of a heteroatom-doped graphene-based photocatalyst for CO2 conversion, where nitrogen (N), boron (B), and selenium (Se) are doped into a graphene lattice to enhance catalytic activity for formic acid production and organic transformations.
The N@B@Se@Graphene used as a photocatalyst for CO2 reduction to formic acid and for facilitating various organic transformations, enabling efficient and sustainable chemical synthesis.
The improved catalytic activity and efficiency of N@B@Se@Graphene showed due to multi-dopant heteroatom integration, enabling enhanced selectivity and yield in CO2 reduction reactions and acetalization reactions without traditional catalysts.
These and other aspects of the embodiments herein will be better appreciated and understood when considered in concurrence with the following explanation and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.
BRIEF DESCRIPTION OF THE DRAWINGS
The illustrated embodiments of the subject matter will be understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and methods that are consistent with the subject matter as claimed herein, wherein:
Figure 1. (i) Schematic representation of artificial photosynthesis consisting a photocatalyst (N@B@Se@Graphene) as a light harvester, ascorbic acid (AsA) as scavenger, rhodium complex as an electron mediator, NAD+ co-factor and formate dehydrogenase as an enzyme (FDH), and (ii) Schematic representation of chitosan derived graphene.
Figure 2. (i) Diagrammatic representation of synthesis procedure of N@B@Se@Graphene photocatalyst, and (ii) 3D view of N@B@Se@Graphene photocatalyst.
Figure 3. Schematic representation of mechanistic pathway of 1,3-oxathiolane-2-thiones.
Figure 4. CO2 conversion to formic acid through energy gradient.
Figure 5. (i) % yield of NADH regeneration of N@Graphene (blue), N@Se@Graphene (dark green), N@B@Graphene (orange), N@B@Se@Graphene (red), (ii) Formic acid production of N@B@Se@Graphene (red), N@B@Graphene (dark blue), (iii) Reusability of N@B@Se@Graphene photocatalyst while performing NADH, (iv) Illustration of concentration ratio (C/Co) versus time (Co = initial concentration of NAD+ and C = concentration of NADH at "t" time) of N@B@Se@Graphene photocatalyst (red) , and (v) Reusability and stability of N@B@Se@Graphene photocatalyst through FT-IR.
Figure 6. UV-visible diffuse reflectance (DRS) of (i) N@B@Se@Graphene photocatalyst, (ii) N@B@Graphene, N@Se@Graphene, and N@Graphene, Fourier Transform Infrared Spectroscopy (FT-IR) of (iii) N@B@Se@Graphene photocatalyst, and (iv) N@B@Graphene, N@Se@Graphene, and N@Graphene.
Figure 7. X-ray Photoelectron Spectroscopy (XPS) (i) C1s spectra, (ii) N1s spectra, (iii) B1s spectra, (iv) Se 3d spectra, and (v) Survey of N@B@Se@graphene photocatalyst.
Figure 8. Scanning electron microscopy (SEM) images of (i) N@Graphene, (ii) B@N@Graphene, (iii) Se@N@Graphene, and (iv) B@Se@N@Graphene photocatalyst.
Figure 9. (i) Elemental mapping, and (ii) Energy Dispersive X-ray Spectroscopy (EDX) of N@B@Se@graphene photocatalyst along with elemental mapping of C, N, B, and Se.
DETAILED DESCRIPTION OF THE INVENTION
The detailed description of various exemplary embodiments of the disclosure is described herein with reference to the accompanying drawings. It should be noted that the embodiments are described herein in such details as to clearly communicate the disclosure. However, the amount of details provided herein 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 scope of the present disclosure as defined by the appended claims.
It is also to be understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and embodiments of the present disclosure, as well as specific examples, are intended to encompass equivalents thereof.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms "a"," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes" and/or "including," when used herein, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof.
It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may, in fact, be executed concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved.
In addition, the descriptions of "first", "second", "third", and the like in the present invention are used for the purpose of description only, and are not to be construed as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Thus, features defining "first" and "second" may include at least one of the features, either explicitly or implicitly.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, e.g., those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
In some embodiments of the present invention, the synthesized N@B@Se@Graphene was fascinated through solid phase reaction method at high temperature.
In some embodiments of the present invention, initially, 1g chitosan (source of nitrogen), 500 mg selenium dioxide and 500 mg boric acid were evenly grounded and kept in a sealed crucible at 1000 ? for 2 hours.
In some embodiments of the present invention, the calcinated product was then dissolved in water, filtered and washed repeatedly with acetone. Thus, resulting in doping of heteroatoms in native carbon lattice of graphene. However, the procedure of N@Graphene, B@N@Graphene, and Se@N@Graphene was also fascinated through solid phase reaction as shown in ESI.
Herein enclosed a method of graphene enhanced with multiple dopants for CO2 conversion comprising the steps of:
fascinating the synthesized N@B@Se@Graphene through solid phase reaction method at high temperature;
grounding 1g chitosan (source of nitrogen), 500 mg selenium dioxide and 500 mg boric acid and kept in a sealed crucible at 1000 ? for 2 hours;
dissolving the calcinated product in water, filtered and washed repeatedly with acetone;
resulting in doping of heteroatoms in native carbon lattice of graphene; and
also fascinating the procedure of N@Graphene, B@N@Graphene, and Se@N@Graphene was also fascinated through solid phase reaction.
The method of a heteroatom-doped graphene-based photocatalyst for CO2 conversion, where nitrogen (N), boron (B), and selenium (Se) are doped into a graphene lattice to enhance catalytic activity for formic acid production and organic transformations.
The N@B@Se@Graphene used as a photocatalyst for CO2 reduction to formic acid and for facilitating various organic transformations, enabling efficient and sustainable chemical synthesis.
The improved catalytic activity and efficiency of N@B@Se@Graphene showed due to multi-dopant heteroatom integration, enabling enhanced selectivity and yield in CO2 reduction reactions and acetalization reactions without traditional catalysts.
EXAMPLE 1
BEST METHOD
Experimental
Materials Required and Instrumentations
The chemicals like chitosan, selenium dioxide (SeO2), boric acid (H3BO3), NAD+ co-factor, L-ascorbic acid, Mono/di-basic of sodium phosphate, (Pentamethylcyclopentadienyl)- rhodium (III) dichloride dimer, formate dehydrogenase, carbon sulphide (CS2), methanol (MeOH), cesium carbonate (Cs2CO3), distilled water, ethyl acetate, acetone, magnesium sulphate, styrene, 4 methyl styrene, 4 nitro styrene were purchased from Sigma Aldrich and used without purification. UV-DRS was recorded by Shimadzu UV-1900i spectrophotometer, ATR-IR spectroscopy was analysed by Nicole 6700 (made by Thermo Scientific, USA) to record FT-IR, CHl608E-220V instrument was used to analyse electrochemical properties. SEM, EDX along with elemental mapping was recorded by JSM 6490 LV (constructed by JEOL, Japan). XPS was recorded by Escalab 250Xi, Thermo Fisher, America. PXRD and Raman was recorded via Rigaku Mini Flex benchtop and LabRam HR.
Synthesis of N@B@Se@Graphene
The synthesized N@B@Se@Graphene was fascinated through solid phase reaction method at high temperature. Initially, 1g chitosan (source of nitrogen), 500 mg selenium dioxide and 500 mg boric acid were evenly grounded and kept in a sealed crucible at 1000 ? for 2 hours. The calcinated product was then dissolved in water, filtered and washed repeatedly with acetone. Thus, resulting in doping of heteroatoms in native carbon lattice of graphene (fig. 2). However, the procedure of N@Graphene, B@N@Graphene, and Se@N@Graphene was also fascinated through solid phase reaction.
EXAMPLE 2
RESULTS AND DISCUSSION
Mechanistic pathway for the formation of 1,3-oxathiolane-2-thiones
A viable mechanistic pathway of 1,3-oxathiolane-2-thiolane is described in Fig 3 where after absorption, the PC gets excited and causes transfer of single electron between PC* and A. Due to photo-redox cycle, aerobic oxidation of PC takes place. Moreover, radical of compound B attacks on vinylic group to form an intermediate free radical called as C, which further combines with O2 to form peroxy radical. This peroxy radical again reacts with vinylic group to produce D radical. Subsequently, removal of methoxy radical takes place followed by cyclization to meet the worth product i.e., 1,3-oxathiolane-2-thiones as shown in ESI Figure S3.25,40 Optimization of reaction were performed to investigate the % yield of the desired product, where styrene was taken as a role model. The critical reaction was implemented with a reaction medium consisting styrene (1.0 mmol), Cs2CO3 (1.0 eq.), CS2 (1.0 mmol) in 3mL MeOH with N@B@Se@Graphene photocatalyst (2mol%). The reaction was irradiated under LED light source for 10 h under O2 environment. The craved product 5-methyl 1,3-oxathiolane-2-thione was extracted in 92% yield. The reaction was implemented for 8 h, yields about 94%. However, the controlled experiments were implemented, which results in importance of light source, base, photocatalyst, CS2, MeOH, and O2 in a critical reaction. Secondly, the reaction was optimized for amount of photocatalyst in MeOH, base, and CS2. These are the reagents required for xanthate formation. For the required yield the demand of CS2 is 1.0 mmol. Although, among the implemented bases, Cs2CO3 was highly effective. This is due to its high solubility in MeOH. To optimized the loading of photocatalyst different concentration of photocatalyst were investigated. The maximum yield obtained at 2mol%. While the yield decreases on decreasing mol% of photocatalyst to 1mol%. Nevertheless, the yield was not affected on increasing the loading of photocatalyst. Additionally, different photocatalyst were also optimized for desirable product yield. Besides these optimizations, the reaction medium was quenched with 1.0 mmol TEMPO (2,2,6,6-tetramethylpiperidyl-1-oxyl) showing radical intermediate while in presence of 1.0 mmol DABCO the reaction medium was not quenched showing triplet oxygen involvement (ESI, Table T2, entry 13). The yield % increases when electron donating groups are attached, while % yield decreases with electron withdrawing groups.
Furthermore, the NADH and Formic acid production takes place through a reaction medium where it was kept in 15mL quartz Pyrex equipped with stirrer in an inert atmosphere and composed of NAD+ co-factor, phosphate buffer, Rh-complex (synthesized by reported literature)41, L-ascorbic acid, x@Graphene photocatalyst. The pH of the reaction medium was maintained at 8 or 10. The reaction medium was then placed below a Xenon lamp having wavelength >420 nm. The distance between the Xenon lamp and the reaction medium was fixed at 5 cm. Prior to illumination, the reaction medium was kept in dark for 30 minutes to attain the absorption-desorption equilibrium. After 30 minutes, the reaction medium was kept under illumination for 2 hours.42,43 During illumination, the NADH concentration was monitored by UV-visible spectrophotometer (NADH concentration increases with time as shown in, figure 4). By measuring absorbance of reaction medium at 340 nm concentration of NADH was determined which have extinction coefficient of 6220 1,4 NADH is produced at 340 nm while other isomers like 1,2 NADH and 1,6 NADH are found to be enzymatically inactive at 340 nm. Therefore, we get selective yield of 1,4 NADH at 340 nm.46 (For yield %, figure 1). However, the production of formic acid from CO2 was also performed within quartz Pyrex in an inert atmosphere. The reaction medium was kept under the visible light source i.e. Xenon lamp having >420nm. The reaction medium was composed of x@Graphene photocatalyst, NAD+ co-factor, Rh-complex, phosphate buffer, L-ascorbic acid and formate dehydrogenase enzyme. The reaction medium was bubbled with CO2 for 1 hour in absence of light (flow rate: 0.5mL/min). After, 1 hour the reaction medium was subjected to light source. The amount of formic acid was determined by high performance liquid chromatography (HPLC)41,47 which is also supported by Scheme S3.
EXAMPLE 3
Illuminating Cellular Energy: A Breakthrough in NADH Photo-Regeneration and Formic acid production Using Advanced Photocatalysts
The cyclic experiments of NADH regeneration and production of formic acid were performed in order to investigate the stability of x@Graphene photocatalyst (figure 5). The cyclic experiments were subjected to 5 cyclic turns. In first turn the 49.75 % of NADH regenerated, whereas in fifth turn 44.69 % of NADH regenerated and 129.85 µM (efficiency~1.623%) of formic acid produced (figure 5). These experimental results show the robustness and usability of the x@Graphene photocatalyst in various applications. Additionally, the FT-IR spectra of the x@Graphene photocatalyst before and after also indicate the durability of chemical and sustainability of the x@Graphene photocatalyst (figure 5). In a controlled experiment, formic acid was not detected when NAD+ co-factor of Rh-complex were absent, which confirms their presence in formic acid production. Similarly, to confirm the photocatalytic response of x@Graphene photocatalyst. An experiment was performed in the absence of x@Graphene photocatalyst under light source, likewise doesn't produce formic acid. Therefore, these experiments confirm the importance of NADH regeneration associated with formic acid production.
Spectrum Unveiled: Revealing the Hidden with UV-Visible Spectroscopy Insights
UV-visible diffuse reflectance absorption spectrum is demonstrated in figure 6 (i). The absorption spectra of N@B@Se@Graphene show broader absorption range in UV-visible region, showing its capability of performing photocatalytic reactions. The spectrum shows the absorption band at ~270nm attributed to p- p* transitions of sp2 graphite lattice. However, absorption band at ~330nm refers to n- p* and p/d- p* transitions, which confirms the doping of nitrogen, boron, and selenium in the carbon lattice structure of Graphene framework. Moreover, the band structure of N@B@Se@Graphene was estimated by using Tauc plot (calculated by UV-DRS spectra) i.e. 2.21eV which is better than N@B@Graphene, N@Se@Graphene and N@Graphene i.e. 2.72 eV, 2.76eV and 2.78eV respectively.48
Harmonizing Molecular Secrets: A Symphony of Discovery with Fourier Transform Infrared (FT-IR) Spectroscopy
Figure 6 (iii) shows the Fourier Transform Infrared spectra of N@B@Se@Graphene photocatalyst. The strong band at 1400-1200 cm-1 is due to C-C stretching in the ring. The peak at 3503 cm-1 and 1677 cm-1 represents the bending and stretching vibrations of primary amines. 1024 cm-1, 1062 cm-1 represents the stretching vibrations of C-N in graphene sheets. However, the peaks of C-Se and B-C at 494 cm-1 and 1171 cm-1 confirm the doping of N, B, and Se in the carbon lattice structure of Graphene. Additionally, in the lattice structure of N@Graphene, stretching vibration of C=C and C-N attributed at 1486 cm-1 and 1017 cm-1 respectively. Moreover, N@B@Graphene and N@Se@Graphene also shows C=C and C-N stretching vibrations at 1480 cm-1, 1056 cm-1 and 1500 cm-1, 1037 cm-1 respectively along with C-B and C-Se at 1145 cm-1 and 476 cm-1 in N@B@Graphene and N@Se@Graphene respectively which confirms the boron and selenium doping in respective lattice.49-52
Unmasking the Surface: Exposing Details with X-ray Photoelectron Spectroscopy (XPS)
X-ray photoelectron spectroscopy (XPS) is a technique used to analyse composition of chemical constituents. Figure 7(i) shows the spectra of C1s comprising 5 peaks at 284.5eV, 284.8eV, 286.0eV, 286.7eV, and 288.9eV attributed to C-B, C-C/C=C, C-Se, C-N, and O-C=O respectively. The spectra of N1s comprises 3 peaks at 397.93eV, 399.68eV, and 400.80eV corresponds to N-B, N=C, and N-C respectively as shown in figure 7 (ii). Spectra of B1s comprise 2 peaks at 191.44eV and 192.36eV, contributed to B-C and B-N respectively. However, the spectrum of Se3d shows Se-C at 56.2eV. Additionally, figure 7(v) shows the XPS survey which confirms the presence of N, B, Se and C at 399.33eV, 191.74eV, 55.06eV, and 284.88eV respectively in N@B@Se@Graphene photocatalyst. 50,53-55
Beyond the Surface: Delving into Morphological Wonders and Elemental Elegance
The morphology of chitosan-based graphene networks was investigated through scanning electron microscopy (SEM). The surface morphology of N@Graphene shows soft, smooth and non-porous like structure as shown in figure 8. After insertion of boron the morphology changes to leaf light rigid structure having minute pores i.e. in N@B@Graphene while in case of selenium insertion in place of boron altered the morphology to sponge like macro porous structure as in N@Se@Graphene. Therefore, when both were inserted as in N@B@Se@Graphene photocatalyst, the morphology changes to spherical rod like rigid structure.56-57 The figure 9 shows the elemental mapping of N@B@Se@graphene photocatalyst confirms the presence of nitrogen (N), boron (B) and selenium (Se) in N@B@Se@graphene photocatalyst. However, this was also confirmed by the Energy Dispersive X-ray Spectroscopy (EDX) as shown in figure 9 (ii).
Conclusions
In conclusions, the hydrothermal decomposition of nitrogen (N), boron (B), and selenium (Se) in carbon lattice of graphene represents the significant innovation in field of photocatalysts. This approach boosts, not only structural and electronic specifications of graphene sheets but also performed remarkable efficiency towards NADH regeneration along with eco-friendly fixation of atmospheric carbon dioxide to value- added fuels and also have potential in synthesis of molecular frameworks.
Non-Patent References
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,CLAIMS:1) A method of graphene enhanced with multiple dopants for CO2 conversion comprising the steps of:
i. fascinating the synthesized N@B@Se@Graphene through solid phase reaction method at high temperature;
ii. grounding 1g chitosan (source of nitrogen), 500 mg selenium dioxide and 500 mg boric acid and kept in a sealed crucible at 1000 ? for 2 hours;
iii. dissolving the calcinated product in water, filtered and washed repeatedly with acetone;
iv. resulting in doping of heteroatoms in native carbon lattice of graphene; and
v. also fascinating the procedure of N@Graphene, B@N@Graphene, and Se@N@Graphene was also fascinated through solid phase reaction.
2) The method as claimed in claim 1, wherein prepared a heteroatom-doped graphene-based photocatalyst for CO2 conversion, where nitrogen (N), boron (B), and selenium (Se) are doped into a graphene lattice to enhance catalytic activity for formic acid production and organic transformations.
3) The method as claimed in claim 1, wherein said N@B@Se@Graphene used as a photocatalyst for CO2 reduction to formic acid and for facilitating various organic transformations, enabling efficient and sustainable chemical synthesis.
4) The method as claimed in claim 1, wherein improved catalytic activity and efficiency of N@B@Se@Graphene showed due to multi-dopant heteroatom integration, enabling enhanced selectivity and yield in CO2 reduction reactions and acetalization reactions without traditional catalysts.

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