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Bottom-Up Synthesis of 2D Nanomaterials for Energy Applications
Published in Ram K. Gupta, 2D Nanomaterials, 2022
Another approach that has been first developed more than 100 years ago is the Ullmann reaction that consists of C-C coupling performed through the reaction between an aryl halide along with high surface area Cu at temperatures higher than 200°C to yield a biaryl and a Cu halide byproduct. Despite its complex mechanism, this approach is still employed today under UHV conditions to grow a thin layer of carbon-based materials over a Cu substrate, even though this approach does not yield large molecules. Yet, large polymerizations with highly aligned structures were obtained through Ullmann’s coupling by using 2,5-diiodo-3,4-ethylene dioxythiophene with the advantage that when it was performed over Cu (110) substrate there was a Cu-S interaction that promoted the alignment of the polymer leading to all-cis geometry, which was also attributed to the anisotropic nature of Cu (110) that created a driving force for one-directional growth [34]. This approach deems a convenient process as it can form accurately structured 2D films over a metallic substrate as it has been used to synthesize porous graphene. The synthesis was performed by 575 K annealing of hexaiodo-cyclohexa-m-phenylene (CHP) for 5 minutes. The precise nanostructured layered material had a pore spacing of 7.4 Å. On top of that, iodine atoms were released from the structure by thermal treatment at 875 K without damaging the 2D structure. The reaction that describes this process can be seen in Figure 4.6.
Synthesis and characterization of copper nanoparticles on walnut shell for catalytic reduction and C-C coupling reaction
Published in Inorganic and Nano-Metal Chemistry, 2018
Asghar Zamani, Ahmad Poursattar Marjani, Abbas Nikoo, Mojtaba Heidarpour, Ahmad Dehghan
In the present work, we wish to report here utilizing walnut shell (WS) which contains cellulose and lignin,[21] in the stabilizing of copper nanoparticles and application of this green nanocomposite (CuNP/WS) as a reusable and efficient catalyst in the reduction of nitroarenes benzonitriles to corresponding amines with NaBH4 at room temperature in aqueous phase. Also due to importance of Cu catalyzed formation of biaryl “Ullmann reaction” for preparing numerous natural compounds, pharmaceutical products and polymers in the material science industries,[22] we study catalytic properties of this nanocomposite by applying it as a catalyst in the classic Ullman reaction to synthesize biaryl in optimized reaction conditions which gave maximum yield with high purity.
Polyaniline-encapsulating CuFe2O4/Cu2O composite: a simple, effective and reusable heterogeneous catalyst for ligand-free N-arylation of amines and nitrogen heterocycles
Published in Inorganic and Nano-Metal Chemistry, 2023
Vahide Ahrari, Firouzeh Nemati
Conventional synthetic methods for the Ullmann reaction often were affected from main drawbacks, including the use of very polar solvents such as nitrobenzene, N-methylpyrrolidone or dimethylformamide (DMF) at harsh conditions (>200 °C) and needing for the stoichiometric amounts of copper complexes with various ligands that led to decreased atom efficiency and some waste problems.[30,31] Many of these ligands and copper complexes are expensive, toxic and sensitive to air and a major challenge lies in the separation of product from the expensive homogeneous catalyst. To overcome these problems the development of recyclable heterogeneous catalysts is crucial.