The steady state and time-resolved emission properties of PyrBpyCMP and Cp*Rh@PyrBpyCMP have been reported previously . While these preliminary results clearly demonstrated the efficient energy transfer from the organic matrix to the RhCp* complex, that was interpreted as the activation of the catalytic metal centre, they provided few information concerning the nature of the excited states responsible of the processes. In order to clarify the nature of the excited states formed upon the photoexcitation of PyrBpyCMP and Cp*Rh@PyrBpyCMP we performed the first fs transient absorption measurements for this family of porous polymers. For the measurements, the polymers were suspended in MeCN:TEOA (5:1) solutions. We point-out here the difficulties of these transient absorption measurements because the polymers are insoluble in any common organic solvent and so, the suspension are highly scattering our supercontinuum probe and the pump beam. So, to carry out these measurements, we had to work by using a standard 1 cm quartz cell, in which the stability and the optical density of the suspension were compatible with the experimental constrains, but at the cost of a degraded time-resolution. We also took all the common precautions by checking the linearity of our signal with the pump intensity and the photostability of the sample. The viscous TEOA helps in stabilizing the suspension, but in counterpart, it generates a strong transient signal. Due to this measurement conditions, we limit our analysis to the pump-probe delays longer than 5 ps, for which we obtained reliable transient spectra (Figure ). At 5 ps, the transient spectrum of PyrBpyCMP is dominated by a broad excited state absorption band from 485 nm to 750 nm, and a weak negative contribution at 475 nm suggesting a stimulated emission band between 450 and 500 nm. The transient absorption spectra exhibit a maximum of absorption at 700 nm and a second maxima at 550 nm. At 2 ns the signal is reduced to a residual absorption below 450 nm and a weak negative contribution from 500 to 700 nm. For Cp*Rh@PyrBpyCMP, the transient spectra in Figure .b are similar to PyrBpyCMP and are essentially dominated by the excited state absorption from the organic part of the polymer. We cannot detect a clear signature that could be assigned to the activated metal centre. Instead, we notice a pronounce negative contribution, that seems to appear at very short time and is still observed in the ns time scale. We tentatively assigned this negative signal to the bleach of the charge transfer absorption band from the organic framework to the metal centre. We are also noticing that the kinetics of decay measured for the absorption band at 700 nm (Fig ) is significantly slower in presence of the metal. So, these transient data reveal for both samples the formation of a large absorption that certainly corresponds to the signature of the excited organic framework. This signature is perturbed in presence of RhCp* but we cannot detect a clear absorption contribution specific of the activated catalytic centre. In order to elucidate the nature of the excited state of the CMP, we performed an exhaustive investigation of the Pyr2Bpy and Cp*Rh@Pyr2Bpy molecular compounds. These molecular compounds can be considered as building block of the CMP (Scheme 1). Our experimental approach is part of a general strategy aiming to develop molecular descriptors of the properties of the photoactive porous polymers that can orient the design of these photocatalysts. Similar approaches are also carried out at the theoretical level . and) the kinetic traces reconstructed at probe = 700 nm and their corresponding fit. In Figure ), the decays have been normalized and the dotted lines correspond to the y=0 level of each curve.