Visible Light-Driven Selective Reduction of CO₂ by Acetylene-Bridged Cobalt Porphyrin Conjugated Polymers

Photocatalytic conversion of CO₂ into renewable fuels with high efficiency and selectivity is desirable for solar energy utilization, but remains a great challenge. Herein, cobalt(II)-porphyrin functionalized conjugated polymers with acetylene bridging units, assembled through the Sonogashira cross coupling reaction, as heterogeneous catalysts for CO₂ photoreduction were presented. Experimental investigations and density functional theory calculations demonstrated the crucial roles of Co centers in porphyrin units for CO₂ activation and conversion, while excessive acetylene group prompted the competing hydrogen evolution reaction and reduced the selectivity. Thus, the CoPor-DBBP afforded superior activity for the CO generation with a rate of 286.7 μmol g^-1  h^-1 and high selectivity of up to 90.4 %. This work presents a new insight for rationally designing of porphyrin-based conjugated polymers as energetic photocatalyst in CO₂ reduction.