Graphitic carbon nitride materials in dual metallo-photocatalysis: a promising concept in organic synthesis

Abstract

In recent years, dual metallo-photocatalysis has grown rapidly, to emerge as one of the most powerful tools in functionalizing organic molecules. In contrast to conventional catalysis, photocatalysis exploits the formation of reactive intermediates by photo-induced atom, electron, or energy transfer processes. An interesting synergy evolved when photocatalysts were pooled together with a non-photochemical second catalytic system comprising mostly metals. In this strategy, the photocatalyst and the metallic system in the presence of light work in synergy with one another, sensitize the organic substrates, and manipulate the reactivity of photogenerated species. Graphitic carbon nitrides encompass a class of transition metal-free photocatalysts, which possess several merits like high chemical stability, low cost, recyclability, and high absorption coefficient (>10⁵ cm⁻¹). Blending this heterogeneous photocatalyst with Earth-abundant metal-based catalytic systems has contributed in abundance towards sustainable and effective synthetic transformations. Most significantly, this rather new branch of catalysis has stimulated an interdisciplinary branch of research that resonates from inorganic and organic chemistry to materials sciences, thereby establishing itself as one of the trending fields in contemporary organic synthesis. The objective of this review is to highlight and illustrate (with mechanisms) the milestones in organic synthesis, where dual metallo-photocatalytic strategies using graphitic carbon nitride have been used. Finally, forward-looking opportunities in this emerging field of research have also been discussed.