Regulating Electronic Structure of Transition Metal Single‐Atoms in COFs for Enhanced Photocatalytic CO ₂ Reduction

ABSTRACT The rational regulation of the electronic structure in single‐atom catalysts (SACs) is pivotal yet challenging for enhancing photocatalytic CO 2 reduction. Herein, we elaborately designed a series of M 1 N 2 sites (M = Au, Pt, Pd, Ru, Mo) anchored on a vinylene‐linked covalent organic framework (sp 2 c‐COF) to construct M/COF SACs for gas‐solid CO 2 photoreduction. The M/COF SACs revealed a d‐orbital electronic configuration‐dependent activity, where the d‐band center exhibiting strong correlation with CO 2 adsorption energy (R 2 = 0.98). Notably, the Mo/COF catalysts delivered a superior CO rate of 294.43 µmol·g −1 ·h −1 with near‐unity selectivity under pure CO 2 and sustained 146.6 µmol·g −1 ·h −1 under simulated flue gas (15% CO 2 ). The superior activity originates from the synergistic interplay of its highest d‐band center (−0.314 eV) and strongest spin polarization among the series. This unique electronic structure, featuring abundant single‐atom states near the Fermi level and half‐occupied d orbitals, facilitates optimal σ‐donation (via d z2 ) and π‐back‐donation (via d xz /d yz ) for CO 2 activation, thereby significantly lowering the energy barriers for *COOH formation and *CO desorption. This work establishes a design principle for high‐performance SACs through the co‐modulation of d‐band configuration and spin polarization.