Porphyrin-based metal- and covalent-organic frameworks as heterogeneous nanosized photocatalysts in organic synthesis

Abstract

The porphyrin-containing metal- and covalent-organic frameworks, respectively MOFs and COFs, are quite versatile porous nanomaterials for hetero-photocatalysis. Indeed, they are capable of catalysing the photoinduced reduction of CO₂ and metal, contaminant degradation, H₂ and O₂ evolutions, photodynamic therapy, and thermotherapy, and biomimicry. Concurrently, they are also efficient photocatalysts for a large variety of organic reactions. This mini-review presents a comprehensive account of the current state of the art in this area and includes several examples of CO₂ transformation for the preparation of plus value chemicals such as methane and cyclic carbonates, formation of peroxides including Juglone, ascaridole and Artemisinin, ketones from benzyl alcohols and N-methylquinolinium salts, and imines from the photooxidative coupling of benzylamines and 2-aminobenzamides, selective oxidation of sulfides into sulfoxides, hydroxylation of aromatic boronic acids, various cases of C–C formations from diazo compounds and stable C–H bonds and oxidative Mannich reactions, C–P bond formations from aerobic cross dehydrogenative-coupling reactions with amines, and C–X bond activations (X = H, F, Br), reduction of nitroaromatics, dehydrogenation of tetrahydroquinolines, deprotection of aromatic ketones from their corresponding aryloxathiolanes, and asymmetric Strecker reactions. It also includes pertinent details regarding the generation of reactive oxygen species (ROS) of types I and II occurring during photoinduced electron and energy transfer processes within the porous heterogeneous nanocatalysts, which play a major role in the transformation of organic molecules.