Regulating Charge Distribution in Porphyrin-Based Polymer for Achieving Photocatalytic CO₂ Conversion to CH₄ or C₂H₆

The photocatalytic conversion of CO₂ into products such as CH₄ and C₂H₆ poses a significant challenge due to the lengthy reaction steps and the high energy barrier involved. In this study, both benzothiadiazole (BTD) and hydroxyl groups (-OH) are introduced into cobalt-based polymerized porphyrinic network (PPN) through a C-C coupling reaction. This modification of orbital energy levels that strengthens the ability of gain electrons and facilitates the charge transfer in PPN. Hydroxyl group largely enhances the ability for light response, while thiadiazole unit tunes the molecular orbital to proper energy level. By this way, BTD-DBP-PPN(Co) achieves the capability for CO₂ conversion to CH₄ and C₂H₆ under the irradiation of light. Co active site is introduced to reduce the energy barrier and facilitate the charge transfer. The reaction pathway for C₂H₆ production has been studied for further mechanism explanation. Overall, a series of cobalt-based porphyrin centers with a donor–acceptor (D-A) structure are designed and synthesized to enhance CO₂ reduction performance and achieve the formation of C₂ products under 300-W Xe lamp irradiation.