Covalent organic frameworks editing for efficient metallaphotoredox catalytic carbon-oxygen cross coupling of aryl halides with alcohols

Cross-coupling by dual metal/photoredox catalysis is attractive for producing valuable chemical building blocks, where the photoredox catalysts lay the foundations for an efficient and sustainable operation. Herein a series of imine based hexagonal covalent organic frameworks (COFs) were developed as photoredox platforms to cooperate with a molecular Ni catalyst for the cross-coupling of aryl halides with alcohols. By varying the C 2 and/or C 3 symmetric molecular subunits, the catalytic performance was effectivity modulated with up to one magnitude difference in the solar-to-coupling product conversion efficiency. Combined (photo)electrochemical measurements and electron paramagnetic resonance spectroscopy revealed the essence of Ni speciation balance to sustain the level of active Ni( i ) and the productive coupling cycle. Specifically, 4-[4-(4-formylphenyl)phenyl]benzaldehyde and planar 4,4′,4′′-(1,3,5-triazine-2,4,6-triyl)trianiline, upon assembling into TT-Ph 3 COF, translated to band structures that ensure Ni( ii ) reduction by conduction band electrons to Ni( i ) and minimal off-pathway deactivation, granting the best cross-coupling performance. Cross-coupling by dual metal/photoredox catalysis is attractive for producing valuable chemical building blocks, where the photoredox catalysts lay the foundations for an efficient and sustainable operation.