Porphyrins Acting as Photosensitizers in the Photocatalytic CO2 Reduction Reaction

Abstract

The success of the photocatalytic CO2 reduction using sunlight depends on how visible light is captured and utilized. Zn porphyrins, which are synthetic analogues of chlorophyll and bacteriochlorophyll, have very intense absorption bands in the visible region and are high potential candidates as photosensitizers for CO2 reduction. However, the use of zinc porphyrins had been limited due to their poor stability under the photocatalytic reduction conditions. We found that the durability of porphyrin during the photocatalytic CO2 reduction reaction is dramatically improved by combining a metal complex catalyst with the porphyrin so that two or more electrons are not accumulated on the porphyrin. In this perspective, we describe the molecular design of systems that combine Re complexes and porphyrins in detail and their unique reaction mechanisms in the photocatalytic CO2 reduction.