shows that, for low perovskite loadings, there is an increase of low-lying sub-band population, as the emission displays a reduced contribution from the high energy transition. Conversely, by increasing the perovskite content, the high energy transition (2.81 eV) became more and more pronounced, with a peak around 20% (and 35%, see main Figure ) of perovskite content while the trend inverts after this value and, at higher perovskite loadings, one can observe again a reduced contribution to the emission band from the high energy transition. Very interestingly, the trend of the high energy transition intensity as a function of perovskite loading recalls that of the ammonia production reported in Figure , with the maximum values of the photocatalytic activity found in the range 20-35% of perovskite corresponding to the percentages that lead to a higher contribution to the broad band by the δ* → LP state transition. This observation points out the effect of compositional engineering in funneling optical excitations to the sites where they can be exploited in photocatalytic processes. In a recent work on MHP/g-C3N4 we demonstrated that the reduction of the low-lying sub-band population allows to retain the excitation in the carbon nitride component where it can be exploited for the ammonia production. Herein we further corroborate this observation and, moreover, we also underline an active role of perovskite in offering catalytic centers as it will be confirmed by the computational modelling work. Noticeably, in these composite systems, a very simple and fast checking of the steady state photoluminescent properties allows to conveniently assess composition/performances relations.