Continuous High-Spin Orbital Coupling for Enhanced CO₂ Photoreduction With H₂O in Covalent Organic Frameworks

Photocatalytic CO₂ reduction with H₂O offers an ideal pathway for sustainable solar fuel production, yet its efficiency remains hindered by sluggish charge transfer and reaction kinetics. Here, we introduce continuous orbital-coupling Ni-Nx covalent organic frameworks to overcome these constraints. Precise coordination tuning establishes strong π-d interactions for efficient charge separation and high-spin triplet formation, while concurrently aligning intermediate p-orbitals with Ni d-orbitals to create a "π→d→p" coupling pathway. This continuous orbital network enables rapid high-spin electron transfer from the framework to the catalytic center and onward to reaction intermediates, and lowers the rate-determining energy barrier by ∼40%. Consequently, the optimized Ni-N6 catalyst achieves efficient photocatalytic CO₂ reduction with H₂O with a CO and O₂ evolution rate of 57.17 and 27.07 µmol g^-1 h^-1, respectively-a 7.5-fold improvement over the weakly coupled analogue. This work establishes a generalizable principle for engineering coordination microenvironments toward high-efficiency molecular photocatalysts.