Recent advances in the rational designing of metalloporphyrinoid-based CO2 reduction catalysts: From molecular structural tuning to the application in catalysis

Electro and photochemical CO₂ reduction (CO₂R) has emerged as a contemporary research field for tackling the fossil fuel problems and construction of a modern chemical industry. For efficient CO₂R, a catalyst is needed, and Earth-abundant Fe, Co, and Ni-based metalloporphyrinoids have appeared as promising molecular catalysts for CO₂R. Several metal complexes of porphyrins, phthalocyanines, corroles, and chlorins-type porphyrinoids have been designed and tested for this purpose. The unique advantages in the judicious tuning of the porphyrinoid structures and their susceptibility towards different functionalization reactions allow an impressive scope to explore and establish a direct structure-activity relationship of metalloporphyrinoids towards CO₂R. There have been rapid advances in this field in the last few years. For the homogeneous CO₂R, the electronic and steric aspects of the porphyrinoids are fine-controlled by installing favorable functional groups at the periphery of the porphyrinoids. On the other hand, in heterogenous CO₂R, the design principle is guided by integrating metalloporphyrinoids in composite material after mixing with carbon supports, semiconductors, or adopting reticular chemistry. All the advancements further result in the testing of excellent metalloporphyrinoids in industrially feasible CO₂ electrolyzers or photoelectrochemical devices. This review focuses on the recent advances in designing principles of metalloporphyrnoids catalysts in homogeneous, heterogeneous, and CO₂R reactors.