Ionic Carbon Nitrides in Solar Hydrogen Production and Organic Synthesis: Exciting Chemistry and Economic Advantages

Abstract

Molecular photoredox complexes from the platinum group paved the way of organic photocatalysis. However, high price and difficulties related to removal and recycling hamper application of such complexes on the larger scale. Carbon nitride semiconductor photocatalysts are deprived at large extent of such limitations. Herein, we summarize application of ionic carbon nitrides in photocatalysis. A salt-like structure of ionic carbon nitrides comprising negatively charged poly(heptazine imide) anion and positively charged alkali metal cations gives rise to a number of unique properties and high activity in photocatalysis. The performance of ionic carbon nitrides in H2 generation is up to 100 times higher compared with the covalent graphitic carbon nitrides. Eleven photocatalytic reactions mediated by ionic carbon nitrides and their long-lived radicals are reviewed. Economy of using carbon nitride photocatalysts in comparison with the photoredox complexes from the platinum group has been analyzed.