On account of their unique properties and robust structures, porphyrins are nature's favorite catalysts. Porphyrins have attracted the attention of researchers for many decades as a result of their intense colors; but in recent years, interest in these molecules has sharply increased, due to their potential use in solving difficult problems in the fields of medicine and environmental protection. Much attention is currently focused on the development of materials for the capture and conversion of CO₂ into value-added products, and porphyrins are proving to be of interest in this area of research. Porphyrins were previously thought to be poorly-absorbant materials, as they are generally planar compounds. However, the development of new, efficient porphyrin-based materials and reliable synthetic routes for porphyrin-based nanoreactors, such as covalent–organic frameworks and metal–organic frameworks, for use as porous materials has helped to overcome the underlying challenges in CO₂ reactivity. Porphyrin-based materials that behave as nanoreactors are promising candidates in the capture and conversion of CO₂ as a result of the presence of the basic pyrrole structure that contains a macrocyclic cavity and large aromatic rings, which facilitate strong interactions with CO₂. This review provides an overview of progress in the area of CO₂ capture and conversion using porphyrin-based molecular materials and nanoreactors. These materials have important structural features in terms of surface area, porosity, CO₂ uptake and the possibility of the catalytic conversion of CO₂ to chemically valuable products.

The pyrrole molecular framework is found in a large number of natural and synthetic compounds of great importance. Since functionalized pyrroles are essential for the progress of many branches of science, its synthesis by simple, efficient and eco-friendly routes are particularly attractive in modern organic and bio-organic chemistry. To this end, a number of synthetic methods have been developed, in which the Paal–Knorr pyrrole synthesis stands out to be the easiest route to synthesize pyrroles. In spite of the efficiency, Paal–Knorr synthesis of pyrroles is considered limited by harsh reaction conditions, such as prolonged heating in acid, which may degrade sensitive functionalities in many potential precursors. Through this route almost all dicarbonyls can be converted to their corresponding heterocycles and therefore it is a synthetically valued process. To address the adverse issues this reaction route has undergone numerous modifications recently and today it can be said that this reaction route is a prominent green route for the synthesis of pyrroles. This review is a tour from the evolution and application of this harsh synthetic route to the eco-friendly greener route developed for the synthesis of pyrroles.