Time-Resolved Mechanistic Depiction of Photoinduced CO Reduction Catalysis on a Urea-Modified Iron Porphyrin.

The development of functional artificial photosynthetic devices relies on the understanding of mechanistic aspects involved in specialized photocatalysts. Modified iron porphyrins have long been explored as efficient catalysts for the light-induced reduction of carbon dioxide (CO) towards solar fuels. In spite of the advancements in homogeneous catalysis, the development of the next generation of catalysts requires a complete understanding of the fundamental photoinduced processes taking place prior to and after activation of the substrate by the catalyst.

Photocatalytic generation of a non-heme Fe(iii)-hydroperoxo species with O in water for the oxygen atom transfer reaction.

Coupling a photoredox module and a bio-inspired non-heme model to activate O for the oxygen atom transfer (OAT) reaction requires a vigorous investigation to shed light on the multiple competing electron transfer steps, charge accumulation and annihilation processes, and the activation of O at the catalytic unit. We found that the efficient oxidative quenching mechanism between a [Ru(bpy)] chromophore and a reversible electron mediator, methyl viologen (MV), to form the reducing species methyl viologen radical (MV˙) can convey an electron to O to form the superoxide radical and reset an Fe(iii) species in a catalytic cycle to the Fe(ii) state in an aqueous solution. The formation of the Fe(iii)-hydroperoxo (Fe-OOH) intermediate can evolve to a highly oxidized iron-oxo species to perform the OAT reaction to an alkene substrate.

Dissection of Light-Induced Charge Accumulation at a Highly Active Iron Porphyrin: Insights in the Photocatalytic CO Reduction.

Iron porphyrins are among the best molecular catalysts for the electrocatalytic CO reduction reaction. Powering these catalysts with the help of photosensitizers comes along with a couple of unsolved challenges that need to be addressed with much vigor. We have designed an iron porphyrin catalyst decorated with urea functions (UrFe) acting as a multipoint hydrogen bonding scaffold towards the CO substrate.