Directing CO2 conversion using photosynthetic microorganisms offers a promising route to couple CO2 sequestration with petrochemical replacement. However, the low‐flux shikimate pathway remains largely unexploited for the synthesis of valuable aromatics. In addition, it is unclear how an enhanced low‐flux pathway would influence the photosynthetic chain. We created a powerful metabolic sink by introducing the 2‐phenylethanol pathway and an artificial feedback‐inhibition‐resistant cassette to Synechococcus elongatus. More than 30 % of the fixed carbon was redirected to the shikimate pathway for aromatic synthesis, and carbon fixation and O2 evolution increased significantly. A “self‐remodeling” mechanism of the photosynthetic chain was discovered, which accelerates electron transport and reduces energy waste. This study represents a significant step toward the industrial viability of CO2 conversion into aromatic compounds and provides design guidance for improving photosynthetic efficiency.