Nickel Single Atoms Reconfigured 3D COFs Boost H₂O₂ Photosynthesis

Designing and implementing novel COFs with unique 3D topologies stand among the foremost methods for unlocking new structures and functions. Such designs address critical limitations inherent in traditional 2D covalent organic frameworks (2D COFs), including obscure active sites, constrained interlayer charge transport, and suboptimal exciton utilization. This work reports the synthesis of a 3D COF (PhFOONi-COF) featuring a helical-staggered interlayer-connected topology, achieved through sequential covalent assembly and precise nickel anchoring. The resulting hybrid bonding setup naturally creates continuous pathways for charge transfer and spatially open catalytic sites, thus efficiently balancing the activity-selectivity dilemma in photocatalytic H₂O₂ production. The integrated framework, featuring nitrogen-engineered fluorenone units coordinated with Ni centers, exhibits exceptional photocatalytic performance with a H₂O₂ production rate of 9.73 mmol g^-1 h^-1 under visible light, which is 15 times that of its purely covalent counterpart. Advanced in situ investigations and density functional theory calculations systematically reveal that the integrated covalent-coordination structure facilitates dual functionality: the Ni-N4 sites geometrically confine O₂ molecules in optimal adsorption configurations, and the conjugated fluorenone skeleton enables directional electron funneling to catalytic centers through orbital hybridization. This work pioneers a paradigm-shifting strategy for designing multifunctional photocatalytic platforms through atomic-level integration of covalent and coordination networks.