CHAPTER 3: Carbon Nitrides (g-C₃N₄) and Covalent Triazine Frameworks (CTFs)

Triazine- and heptazine-based polymeric systems, such as carbon nitrides (g-C₃N₄) and covalent triazine frameworks (CTFs), are high surface area, thermally and chemically stable materials with tailorable surface functionality, compositions, size, thickness, pore geometry, pore size distributions and morphologies. These heteroatom-bearing polymers have a tunable band gap, an in-plane quantum confinement effect and semiconductor features, predominantly favoring their usage in a wide range of fields such as optoelectronics, photocatalysis, gas sorption and sensor applications, etc. Most importantly, they also serve as multifunctional heterogeneous metal-free catalysts and as catalyst-support materials for several organic transformations. This chapter puts forth remarks on challenges and opportunities for designing triazine- and heptazine-based conjugated polymeric materials by overcoming the hurdles in classical synthetic approaches. Developments in synthetic protocols such as a hard/soft-templating strategy; exfoliation; ionothermal, microwave-assisted, supramolecular and solvothermal approaches; and combined methods for fabricating desired/optimized electronic-, nano- and hetero-structured carbon nitrides (g-C₃N₄) and CTFs are reviewed in an exemplary manner. New strategies are discussed for developing different donor–acceptor-based polymers and nano-architectures that provide extensive opportunities for utilizing these materials in sustainable catalysis, solar energy conversion and related devices.