Photosensitization associated with light absorption and energy/electron‐transfer represents the central processes for photosynthesis. However, it's still a challenge to develop a heavy‐atom‐free (HAF) strategy to improve the sensitizing ability of polymeric photosensitizers. Herein, we propose a new protocol to significantly improve the photosensitization by decorating mother conjugated microporous polymer (CMP‐1) with polycyclic aromatic hydrocarbons (PAHs), resulting in a series of CMPs (CMP‐2–4). Systematic study reveals that covalent modification with PAHs can transfer charge to Bodipy in CMP to further facilitate both intersystem crossing and electron‐hole separation, which can dramatically boost energy‐/electron‐transfer reactions. Remarkably, CMP‐2 as a representative CMP can efficiently drive the photosynthesis of methyl phenyl sulfoxide with 92 % yield, substantially higher than that of CMP‐1 (32 %). Experiments and theory calculations demonstrate the structure‐property‐activity relationship of these CMPs, opening a new horizon for developing HAF heterogeneous photosensitizers with highly efficient sensitizing activity by rational structure regulation at a molecular level. A proof‐of‐concept strategy to trigger charge transfer for improving photosensitization is the covalent modification of conjugated microporous polymers (CMPs) with polycyclic aromatic hydrocarbons (PAHs). Charge transfer from the PAH donor to the Bodipy acceptor in CMPs can facilitate both intersystem crossing and electron–hole separation, leading to excellent performance for both energy‐ and electron‐transfer reactions.