Porphyrins Acting as Photosensitizers in the Photocatalytic CO2 Reduction Reaction

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.

Automated summary

The success of photocatalytic CO2 reduction using sunlight relies on the effective capture and utilization of visible light. Zinc porphyrins, synthetic analogues of chlorophyll and bacteriochlorophyll, have strong absorption bands in the visible region and are potential photosensitizers for CO2 reduction. However, their poor stability under photocatalytic reduction conditions has limited their use. By combining a metal complex catalyst with the porphyrin, we dramatically improve the durability of the porphyrin during the photocatalytic CO2 reduction reaction by preventing the accumulation of multiple electrons on the porphyrin. We provide a detailed description of the molecular design of systems that combine Re complexes and porphyrins, as well as their unique reaction mechanisms in photocatalytic CO2 reduction.