Realizing C–C Coupling via Accumulation of C1 Intermediates within Dual‐Vacancy‐Induced Dipole‐Limited Domain Field to Propel Photoreduction of CO₂‐to‐C2 Fuel

Abstract Photocatalytic conversion of CO₂ and H₂O into high‐value‐added C2 fuels remains a tough challenge, mainly due to the insufficient concentration of photogenerated electrons for the instability of C1 intermediates, which often tend to desorb easily and disable to form C─C bonds. In this work, photoreduction of CO₂‐to‐C₂H₆ is successfully achieved by introducing adjacent C, N dual‐vacancy sites within the heptazine rings of ultrathin g‐C₃N₄, which results in the opening of two neighboring heptazine rings and forms a distinctive dipole‐limited domain field (DLDF) structure. In situ X‐ray photoelectron spectra and in situ fourier transform infrared spectra provide direct evidence of the rapid accumulation and transformation of C1 intermediates, especially CO^* and CHO^*, within the DLDF. Ab initio molecular dynamics further substantiates the role of DLDF in promoting C–C coupling between CO^* and CHO^*, through the analysis of interaction trajectories and energy changes of their central atoms, ultimately achieving a high yield of C₂H₆ up to 57.86 µmol g⁻¹ h⁻¹. It is for the first time to propose the concept of DLDF for significant advancement in photoreduction of CO₂‐to‐C2 fuel with the evident breakthrough to address the challenge of coupling carbon‐containing intermediates between active sites, offering new insights for the design of C–C coupling sites in single‐component photocatalysts.