Interlayer Polarization Induced by Ag-N2 Motifs in Spherical Covalent Organic Framework Driving Efficient CO2 Photoreduction

Covalent organic frameworks (COFs) have emerged as promising candidates for photocatalytic CO2 reduction. While the introduction of single metal atoms can enhance activity, most reported COF-single atoms catalysts adopt near-planar coordination environments that confine carrier migration largely within individual layers, imposing high interlayer transfer barriers and sluggish kinetics and consequently hindered overall performance. This work constructed a single-atom Ag-modified covalent organic framework (Ag-COF) by confining isolated Ag atoms within a spherical TD-COF scaffold, thereby wiring adjacent layers into efficient interlayer charge-transfer channels for gas-solid CO2 photoreduction. Under visible light and without sacrificial agents, Ag0.15-COF delivered a CO formation rate of 184.05 μmol·L-1 with near-unity CO selectivity, representing a tenfold improvement over pristine TD-COF. Structural and photoelectronic analyses identified the N-Ag-N bridging motifs that lowered the interlayer electron-transfer barrier, accelerated carrier separation/migration, and tuned the local electronic structure of active sites. In situ spectroscopy combined with thermodynamic calculations further revealed that the strengthened interlayer charge flow enhanced CO2 adsorption/activation and markedly reduced the barrier for forming the key *COOH intermediate. This study elucidates, at the atomic scale, how interlayer charge transfer governs the activity and selectivity, and provides a design blueprint for highly efficient single-atom-modified COF photocatalysts.