Gas-Phase Photocatalytic CO₂ Reduction to Ethane via EDOT-Based Trimers

The photocatalytic conversion of CO₂ into fuels and high-value chemicals is a promising strategy to counteract the negative impact of greenhouse gas emissions. While most studies focus on UV-responsive semiconductors, few evaluate photocatalytic performance in the gas phase under visible light. In this work, we introduce 3,4-ethylenedioxythiophene (EDOT)-based conjugated trimers as visible-light-responsive photocatalysts for CO₂ conversion in the gas phase. We examine how changes in the acceptor units of these donor–acceptor–donor trimers affect their molecular arrangements and photocatalytic performance. By tuning the acceptor units, we achieve different aggregate states, which enable us to modulate product selectivity, shifting from C₁ to C₂ products with high stability for over 10 h of light exposure under continuous gas flow. We attribute these variations to differences in energy band alignment, excited-state delocalization, and optical absorption properties linked to molecular packing. Moreover, the crucial roles of Cu as a cocatalyst and TEOA as a sacrificial agent in enhancing selectivity toward C₂ products were also discussed. The integration of experimental findings with density functional theory (DFT) calculations provides comprehensive insights into the molecular-level mechanisms driving selectivity and efficiency. Our study demonstrates that visible-light-responsive organic trimers can effectively convert CO₂ to C₂ value-added products in the gas phase, contributing significantly to the development of solar-driven fuel production.