d ‐Orbital Electron Spin Polarization Field Inhibits Photo‐Generated Carrier Recombination for Panel Photoelectrocatalysis

The rapid recombination of photo‐generated carriers remains a critical challenge limiting the photo‐electrocatalytic water splitting performance in covalent organic frameworks (COFs). Herein, this study proposes a d ‐orbital electron spin polarization strategy ( d ‐ESP) based on conjugated reticular oligomers (CROs). By coordinating with monatomic metals (M‐Cπ, Zn, Ni), the d‐ orbital splitting was induced, and the generated ESP field resulted in spatial rearrangement of electrons, changing the chemical adsorption strength and inhibiting the charge carrier recombination. The carrier dynamic demonstrates that the partially filled 3 d ⁸ orbitals of Ni ²⁺ cation significantly lower the conduction band minimum (CBM) energy level, thereby optimizing carrier migration pathways and effectively suppressing the carrier recombination at spin‐polarized Ni‐N ₄ active sites in the absence of same‐spin‐oriented hole pairs. In contrast, the fully filled 3 d ¹⁰ orbitals of Zn ²⁺ cannot generate spin polarization due to the paired electrons. The fabricated ITO/CuI/Ni‐CRO _TAPP‐PDA /P3HT/SnO ₂ /Pt photoelectrode demonstrates excellent performance, achieving a Δ J of 80.1 μA cm ⁻² at 0.4 V versus reversible hydrogen electrode (RHE) under illumination, representing a 2.0‐fold enhancement compared to the ITO/CuI/CRO _TAPP‐PDA /P3HT/SnO ₂ /Pt device, with operation stable operation for 10 h. This work establishes a novel design paradigm for modulating optoelectronic device performance through the electron spin‐state, providing critical guidance for developing artificial photosynthesis.