Precisely Constructed Asymmetric Coordination Tuned High‐Spin Co Sites for Sacrificial Agent‐Free H ₂ O ₂ Photocatalytic Production

Single‐atom catalysts have emerged as an important kind of photocatalysts for H ₂ O ₂ production. However, the inability to precisely mediate the coordination structure of metal single atoms has significantly hindered the efficiency of photocatalytic H ₂ O ₂ production. In this work, we introduce a Salen group into TPAB‐COF to precisely anchor Co atoms featuring atomically dispersed Co–N ₂ O ₂ asymmetric coordination units (CoSL‐COF). Experimental results and density functional theory calculations reveal that the Salen‐coordinated Co centers with high‐spin and electron‐rich state enable a Pauling‐type O ₂ adsorption configuration, effectively preventing the cleavage of the O–O bond of *OOH. Meanwhile, the adopted d ‐band center of Co delivers an appropriate regulation of O ₂ adsorption. Therefore, the balance between oxygen activation capacity and *OOH intermediates stability is well optimized, which enhances the selectivity of 2e ⁻ ORR processing. The distinctive π‐d conjugation architecture within the framework also significantly promotes the separation and transportation of photogenerated charge carriers. As a result, the elaborately designed CoSL‐COF with partially asymmetric coordinated CoN ₂ O ₂ achieves a high H ₂ O ₂ production rate of 1000.8 μmol g ⁻¹ h ⁻¹ in pure water under visible‐light irradiation without any sacrificial agents addition, which is higher than most of reported metal sites mediated COFs photocatalysts for H ₂ O ₂ production.