Imine-Based Covalent Organic Frameworks as Photocatalysts for Metal Free Oxidation Processes under Visible Light Conditions

Photochemistry of extended polyimine COF structures with laminar, spherical and 3D architectures has been examined. We show that these materials, composed by undecorated phenyl rings and imine fragments, can act as photocatalyts in oxidative transformations, being the crystalline laminar material the most active photocatalyst. The sulfoxidation reaction proceeds with good yields for a large variety of different sulfides. This process was carried out under visible light conditions (20 W), ethanol/H2O as solvent, and the heterogeneous porous material can be recycled up to 9 times. The crystallinity favours the behavior as photocatalyst of laminar and spherical COFs whereas any particular effect on the 3D material activity was observed. Sulfoxidation reaction mainly proceeds through an energy transfer mechanism using crystalline laminar material. In addition, these materials as photocatalysts were used for the oxidation of phenyl boronic acid into phenol.