Perylene diimide covalent organic frameworks super-reductant for visible light-driven reduction of aryl halides
In recent years,there has been a growing interest in the utilization of molecular photocatalysts in their radical ionic forms,especially as visible-light super-reductants.These catalysts exhibit re-markable capabilities in facilitating otherwise inert high-potential organic reactions,such as the reduction of aryl halides to aryl radicals.However,the development of heterogeneous su-per-reductants has lagged behind due to the deactivation effect caused by molecular aggregation.This study presents a novel approach to address this limitation by heterogenizing perylene diimides(PDls)super-reductants with a consecutive photo-induced electron transfer mechanism into two-dimensional donor-acceptor(D-A)covalent organic frameworks(COFs).Both COFs,possessing D-A electronic structures and photothermal effects,demonstrated superior visible-light photocata-lytic performance compared to their homogeneous counterparts.They achieved up to 99％conver-sion in the dehalogenation of aryl halides,primarily through a hydrogen atom trapping aryl radical mechanism.Additionally,we conducted a comparative investigation of the excited states of radical anionic D-A-type COFs and DPPDI using femtosecond transient absorption spectroscopy.Notably,the lifetimes of COFs were significantly prolonged,measuring 210 and 260 ps,respectively,com-pared to the 150 ps lifetime of(DPPDI·-).This study offers valuable insights into the design of effi-cient free radical ion-type photocatalysts,with potential applications in various chemical transfor-mations.
Perylene diimideCovalent organic frameworksPhotocatalystHomogeneousReduction of aryl halides
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