Analyses of the N and 31 P NMR spectra of Ga@SiO2 contacted with N-Py and TPPO, respectively, made it possible to resolve the immediate coordination environment of Ga surface sites in Ga@SiO2 (Figure ), revealing the presence of two sites, namely GaBA and GaLA, which respond differently upon addition of probe molecules and are expected to display distinct reactivity in catalysis. Analysis of the 71 Ga spectrum of 15 N-py/Ga@SiO2 further supports the presence of two families of sites: