Selective photocatalytic reduction of CO2 to CO mediated by atomically dispersed Cu-anchored upon hollow covalent organic frameworks

Selective photoreduction of CO 2 to a single product remains a major challenge in solar fuels catalysis. Herein, we report a hollow covalent organic framework hosting isolated Cu sites (Cu-HCOF) which drives the CO 2 -to-CO reaction through the visible-light with high activity and selectivity. The ordered framework directs interfacial electron transfer from an external photosensitizer to the single Cu centers, accelerating CO formation while suppressing H 2 evolution. Robust chemical anchoring of single Cu sites within the framework secures atomic dispersion of the active centers and simultaneously enhances CO 2 uptake and diffusion. Under visible-light irradiation, Cu-HCOF achieves a CO yield of 2881 μmol/g within 3 h (≈960 μmol/g.h), exhibiting 91 % selectivity over H 2 . Notably, the CO production rate of Cu-HCOF is enhanced by factors of 52.5 and 1.5 relative to pure COF and shapeless COF-Cu; respectively. We attribute this performance to the coupled effects of the hollow architecture, enhancing light harvesting via multiple internal reflections and shortening mass-transport pathways as well as; the locally tailored electronic environment of the Cu sites, which facilitates charge separation and CO 2 activation. These results establish morphology-controlled COFs with atomically dispersed metals as an effective platform for tuning active-site electronics and advancing selective CO 2 reduction into CO. • A morphology-inherited strategy adopted to design a unique Cu-HCOF photocatalyst. • Optimized catalyst revealed to be highly selective toward CO 2 photoreduction to CO. • Hollow triazine-based framework enhanced light utilization of catalytically active sites. • Cu atomic dispersion facilitated sunlight abs., CO 2 ads./activation & separation of e-h + pairs. • Tailored photocatalyst showed remarkable structural stability through the process.