Long-Wavelength Visible Griffith-Type Oxygen Photoactivation on Isomeric Mesoporous Al-Salen Covalent Organic Polymer...

Covalent organic polymers (COPs) have emerged as promising photocatalysts for efficient solar-driven conversion of energy into chemicals. However, it remains rare for COPs capable of effectively harvesting long-wavelength visible to near-infrared (L-Vis-NIR) light (λ > 600 nm) to achieve these photochemical transformations. Here, two isomeric mesoporous Al-Salen COP fibers are demonstrated as L-Vis-NIR-responsive photocatalysts for efficient Griffith-type oxygen activation to produce hydrogen peroxide (H₂O₂). Both COPs achieve a high H₂O₂ production rate of about 1607 µmol g_cat ^-1 h^-1 under irradiation of common domestic LED lights (680-690 nm, 3.18 mW cm^-2) using 1,2,3,4-tetrahydroisoquinoline as a sacrificial reagent with a high solar to chemical efficiency of about 5.0%. Their efficient L-Vis-NIR-responsive photocatalytic performance is attributed to their narrow band gaps of about 1.5 eV, efficient charge separation facilitated by integrated electron-donor (benzene ring) and electron-acceptor (Al-Salen Lewis acid site) structures, and a direct Griffith-type photo-activation mechanism for oxygen. No significant isomerism effect is observed in their photocatalytic performance, attributed to the similar photoinduced charge carrier behaviors mainly affected by the local Al-Salen moieties rather than the topological structure. This study highlights isomeric Al-based COPs as effective platforms for L-Vis-NIR photocatalysis and opens avenues for the development of Al-based COP photocatalysts for diverse chemical transformations.