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. We found a spectacular photocatalytic activity reaching unreported TONs and TOFs as high as 7270 and 3720 h , respectively. While the Fe redox state has been widely accepted as the catalytically active species, we show here that the Fe species is already involved in the CO activation, which represents the rate-determining step in the photocatalytic cycle. The urea functions help to dock the CO upon photocatalysis. DFT calculations bring support to our experimental findings that constitute a new paradigm in the catalytic reduction of CO .