Planar ReN₁S₁ Sites with Dual σ-Channels Drive High-Performance CO₂ Photoreduction

Abstract

Although covalent organic frameworks (COFs) provide an adjustable platform for visible-light-driven CO2 reduction, their practical application is fundamentally limited by the lack of active sites for polarizing the C=O bond and the low efficiency of long-range charge transport. Here, we designed an olefin-linked donor-acceptor COF (Py-2CN-COF) and anchored atomically dispersed rhenium (Re) single atoms (SAs) to create a planar ReN1S1 coordination motif that functioned as a dual-channel electron sink. This structure shortened exciton diffusion, reduced the exciton binding energy from 112.28 to 100.26 meV, extended the carrier lifetime from 0.786 to 1.157 ns, and directed photogenerated electrons efficiently to the active sites. The optimized Re3-Py-2CN-COF achieved a CO production rate of 119.5 μmol·g-1·h-1 with 92.3% selectivity under visible light, without sacrificial agents, a 12.7-fold enhancement over the pristine COF. In situ Fourier transform infrared (FT-IR) spectroscopy unveiled a *CO2 → *COOH → *CO pathway, and theoretical calculations confirmed that the Re center lowered the adsorption energy of CO2 from -0.23 to -0.93 eV, extended the C=O bond length from 1.17 to 1.23 Å and injected 0.22 e- into CO2. This work establishes in-plane ReN1S1 coordination as an effective structural strategy to accelerate proton-coupled electron transfer, providing a general design principle for developing highly efficient and selective COF photocatalysts toward sustainable CO2 valorization.