Carbon Nitride as a Heterogeneous Photocatalyst for Organic Transformations
The development of sustainable and environmentally benign methods to perform chemical transformations has become a key challenge in chemistry. Visible light photoredox catalysis has recently attracted wide attention as a versatile approach to perform numerous reactions under mild conditions, but progress has been mostly confined to homogeneous photocatalysts, especially precious Ir or Ru metal complexes. In this thesis, carbon nitrides have been introduced as an inexpensive, stable, easy-to-synthesise, scalable and non-toxic heterogeneous photocatalyst. Prior to this work, carbon nitrides have been mostly studied as a photocatalyst for solar fuel productions and environmental applications. Here, the focus is on employing carbon nitrides photocatalyst for fine chemical synthesis and perform modification on carbon nitrides to achieve further efficiency and sustainability as a photocatalyst. In Chapter 2, the Minisci-type coupling reaction using carbon nitrides as a photocatalyst is described. The reaction demonstrates coupling of various heteroarenes with ethers, alcohols, and amides and easy recycling of the photocatalyst. The reaction advances existing photocatalyst methods by applying recyclable carbon nitrides, atmospheric O2 as an oxidant and generation of H2 in the presence of co-catalyst under anaerobic condition. In Chapter 3, Ni-deposited mesoporous graphitic carbon nitride has been developed as a fully heterogeneous dual catalytic system, the feasibility of the material is demonstrated for the additive and ligand free C-O cross-coupling reaction under visible light irradiation. This unprecedented dual catalytic system allows the significantly low nickel loading and easy recycling on the material. In Chapter 4, Ni-deposited mesoporous graphitic carbon nitride has been explored for the preparation of anilines using a dual photocatalytic system. Various anilines are prepared by the cross-coupling of aryl halides with sodium azide in mild conditions. Mechanistic studies are performed to deduce the formation of anilines instead of aryl azides.
Photocatalysis, green chemistry, Sustainable chemistry, Heterogeneous catalysis, organic synthesis
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