Abstract
Nitrogen-doped graphene quantum dots (N-GQDs), which are less than 10 nm in size, are an interesting member of the nanocarbon materials family. N-GQDs nanostructures have been broadly applied in various fields, such as drug-gene delivery systems, photocatalytic reactions, and catalysts, owing to their unique properties. However, N-GQDs have rarely been introduced as a catalyst in organic synthesis. Herein, CoFe2O4 nanocomposites with diverse morphologies are fabricated in various conditions (e.g. green routes, various pH adjusters, temperatures). Due to further active sites on the surface of the nanocomposites, morphology engineering can be effective in catalytic activities. Following the synthesis, the catalytic activity of the engineered CoFe2O4 nanocomposites was screened, and it presented the order of spherical > rod > prism > cubic. The uniform spherical morphology provides more accessible active sites. Then, the novel nano-sized N-GQDs/CoFe2O4 magnetic spherical composite was readily fabricated by a green, low-cost, and easy hydrothermal route. The engineered composite was applied as an efficient magnetic nanocatalyst for the MW-assisted one-pot synthesis of new and known quinoline-3-carbonitrile derivatives (83–96%) in the shortest reaction time (60–90 s). Furthermore, the green route, easy separation of the nanocatalyst, and reusability (7 runs) without noticeable loss of catalytic efficiency are other advantages.
Highlights
In recent decades, numerous categories of nano-sized carbon materials, such as fullerene, carbon nanohorns, carbon quantum dots (CQDs), and graphene quantum dots (GQDs), have been developed owing to their exceptional physicochemical attributes.[1,2] GQDs, which are a new type of carbon nanostructure, reveal many interesting attributes
The probable reaction mechanism for the microwave irradiation (MW)-assisted synthesis of 6-bromo-2-methoxy-4-(4-nitrophenyl)quinoline-3carbonitrile in the presence of Nitrogen-doped graphene quantum dots (N-GQDs)/CoFe2O4 sphere nanostructures from the three-component reaction of methyl 2-cyanoacetate, 4-nitrobenzaldehyde, and 4-bromoaniline is demonstrated in Scheme 3. It seems that the functional groups on the surface and the edges of the N-GQDs/CoFe2O4 nanocomposites play the main role in the catalytic activity
The CoFe2O4 sphere composites were decorated with N-GQDs
Summary
Numerous categories of nano-sized carbon materials, such as fullerene, carbon nanohorns, carbon quantum dots (CQDs), and graphene quantum dots (GQDs), have been developed owing to their exceptional physicochemical attributes.[1,2] GQDs, which are a new type of carbon nanostructure, reveal many interesting attributes These properties have their origins in their distinguished structure features.[3,4] they can be used for drug delivery, biosensors, catalyst activity, etc.[5] Generally, GQDs can be fabricated by applying two approaches: “top-down” link broken various carbon structures, and “bottom-up” preparation from polymers or organic compounds such as citric acid.[6,7] the presence of functional groups (e.g. hydroxyl and carboxyl) on the edges of GQD structures can be applied as bonding agents to the substrate or coating materials.
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