TCSPC measurements were also performed in THF:TEOA solution at the volume ratio 5:1 corresponding to the typical condition of the CO2 photoreduction . TEOA can be irreversibly oxidized (ENHE = + 0.5-07 V) as sacrificial electron donor to regenerate the photosensitizer or, depending on the reaction conditions, it can act as a BrØnsted base when associated with another sacrificial electron donor . The emission lifetime measurement allows to determine directly if TEAO, at high concentration in the THF:TEOA mixture, can interact directly with the excited state of Pyr2Bpy or if TEOA behaves essentially as a sacrificial electron donor reacting after a potential oxidation of Pyr2Bpy during the CO2 reduction cycle. The addition of TEAO accelerates significantly the emission decay in comparison to the case of neat THF (Figure ). The emission spectrum of Pyr2Bpy is not modified (Figure SI-2.1) indicating that the nature of the emitting state of Pyr2Bpy is also not affected by the presence of TEOA. From the fit of the decay the lifetime of S1 in the mixture is obtained to be THF:TEOA = 0.7 ns. By comparing the lifetime in pure THF and THF:TEOA mixture, the decay time associated with the reaction of the excited Pyr2Bpy with TEOA is TEOA = 0.7 ns. With a concentration of TEAO of 1.25 mol•L -1 and assuming a pseudo-first order decay, the rate constant for the quenching of the S1 state of Pyr2Bpy by TEOA is k = 1.14×10 9 L•mol -1 •s -1 . From this value, it can be concluded that at molar concentration of TEOA, as it is usually the case for photocatalytic reactions condition using this amine as sacrificial electron donor, the excited states Pyr2Bpy, and probably of other pyrene-aryl derivatives, with a lifetime as short as 200-300 ps can directly react with the amine.