Particle Formation. The materials 1-M/SiO2-700, (M=Ni, Pd, Pt) were subjected to a temperature treatment under a flow of H2. From IR spectroscopy, the removal of organic fragments from the surface and the re-emergence of terminal OH groups were observed (Figures ). HAADF-STEM micrographs reveal that particles form for all materials (Figure , and Figures ). The observed particle sizes are given in Table (and Figure ). For Ni and Pt, the obtained particles were small and size homogeneous. In contrast, Pd/SiO2 shows a broader (and in some areas bimodal) particle size distribution (Figure ). Analogously, the materials 1-M/Al2O3-600 (M=Ni, Pd, Pt) were subjected to a temperature/hydrogen treatment. IR spectroscopy again confirms the removal of organic ligands, while the OH groups are partially regenerated (Figure ). The materials were analyzed using HAADF-STEM imaging. For Pd and Pt, small nanoparticles with a narrow size distribution were obtained (Figures S35-S37, Table &). For Ni/Al2O3, particles could not be resolved well enough by STEM techniques (Figure ) to allow for determination of size, likely due to low contrast in combination with small particles (≤1 nm). However, the formation of Ni(0) nanoparticles is supported by Ni K-edge X-ray absorption spec- ). For the SiO2-based sample, a mean particle size of 1.9 nm was found which is in agreement with STEM. For Ni/Al2O3, the observed coordination number is too low (5.4) to allow for accurate estimation of particle size, but is consistent with an average particle size in the sub-nanometer range. This is also supported by the shortening of the Ni-Ni bond lengths (2.44 Å vs.