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

Abstract

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, Ag_0.15-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.