**3. Current and future prospect**

oxide surfaces can be reduced by heating at elevated temperature. Various heteroatoms such as N, B, P, Se, S, F, and Cl [24] can be incorporated into the lattice of graphene sheets. Several

GO and their chemically converted forms have shown broad spectrum of catalytic activity ranging from oxidation reactions and thermal decomposition reactions. Bielawski et al., first demonstrated catalytic activity of graphene oxide for liquid phase organic transformations [26]. Since then, a variety of organic transformations have been explored taking advantage of the functional groups present on the graphitic surface. **Table 1** summarizes a variety of

Further, the two-dimensional surface of graphene based materials can be used to anchor other active catalysts as well as biocatalysts. For example, the catalytic activity of several enzymes including cytochromes, peroxidases, myoglobins, and hemoglobins supported on graphene

**Catalyst Reactions Active sites References**

O2

dissociative adsorption chemisorption on

rGO-NEt3 Hydrolysis of ethyl acetate Amino groups are active

rGO-PAMAM Knoevenagel condensation Basic sites of the catalyst [34]

**Table 1.** Catalytic reactions by GO and chemically converted GO. (B, N)-doped holy G [(BN)HolG], reduced

H Dehydration of xylose to furfural ─SO3

**Thermal decomposition reaction**

rehydrogenation of LiBH4

active sites

groups

) Electron rich oxygen groups

sites

), rGO functionalized with ─SO3

H groups onto

[28]

[29]

[30]

[33]

[35]

H (rGO-SO3

H) and

Beneficial B doping [31]

H are active sites [32]

organic reactions can also incorporate acidic functional groups such as ─SO3

reported reactions catalyzed by GO and chemically converted GO.

**Oxidation reactions (promoted by** 

(BN)HolG Aerobic oxidation of amines Doped N and B are

GO Aerobic oxidation of benzylic alcohols Oxygen functional

**Oxidation reactions (promoted by other** 

**)**

**molecular O2**

**oxidants)**

**Reduction reactions**

G ribbon edge

**Acid reactions**

**Base reactions**

rGO Oxidation of pollutants (H2

H2

rGO Thermal dehydrogenation and

poly(amidoamine)-modified rGO (rGO-PAMAM).

graphene oxide (rGO), triethylamine modified rGO (rGO-NEt<sup>3</sup>

B, N or O doped G ribbon edges

rGO-SO3

graphene sheets [25].

32 Graphene Oxide - Applications and Opportunities

The carbon based nanomaterials have already demonstrated their enormous potential either as catalysts or heterogeneous catalyst supports. Graphene oxide with oxygenated functional groups on their surface could act as active sites for various acid catalyzed and oxidative catalytic reactions. Recent advancement of these graphene based materials shows that the modification of graphene surface by different methods leads to generation of holes which acts as traps for reactive oxygen species for many challenging organic reactions [42]. Hence tremendous possibilities of these carbonaceous nanomaterials remain to explore in various fields including chemical synthesis, energy storage, fuel-cells, environmental remediation and organism degradation. Carbon nanodots are the recent inclusion to the nanocarbon family. The excellent photoluminescence properties of carbon nanodots have directed their application in different fields including sensing, optoelectronics, bio imaging, nanomedicine, etc. Although they are widely explored in sensing as well as bio-medical application, their inherent photocatalytic capability towards organic synthesis has not been explored much. So, the development of carbon nanodots towards organic synthesis may result in an important alternative to the traditional transition metal based catalysts. There are still huge scope towards (i) high performance carbon catalyst specific for desired products, (ii) development of chiral carbon nanomaterials for enantioselective synthesis, (iii) affordable methods for large scale synthesis, industrial scalability and economic viability, (iv) detailed elucidation of catalytic mechanism that can bring further improvements in catalytic activity and (v) stability of the catalyst to maintain excellent catalytic activity during recycling. Overall, development of carbon related catalysts with broader applications is imminent towards green and sustainable chemistry.

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