Synthesis and Catalytic Application of Ag44 Clusters Supported on Mesoporous Carbon

4-(Fluorophenyl)thiolate-protected Ag 44 clusters (Ph 4 P) 4 [Ag 44 (SC 6 H 4 F) 30 ] were calcined on mesoporous carbon (MPC) under vacuum at 300–500 °C for 2 h. X-ray absorption spectroscopy, transmission electron microscopy, and thermal-desorption mass spectrometry revealed that sulfur-free Ag 44 clusters were successfully produced by the calcination of [Ag 44 (SC 6 H 4 F) 30 ] 4– at 300 °C, in sharp contrast to the formation of silver sulfide nanoparticles by the calcination of dodecanethiolate-protected Ag nanoparticles (3.0 ± 0.6 nm). Ag 44 /MPC was applied in the catalytic dehydrogenation of ammonia–borane (NH 3 BH 3 ) as a test reaction. It turned out that the Ag 44 /MPC catalysts produced 1 equiv of H 2 from NH 3 BH 3 but only in the presence of O 2 (turnover frequency 1.9 × 10 3 h –1 Ag atom –1 ). Given that nanoparticles of other metals (Pt, Pd, Rh, Ni, or Ru) produced 3 equiv of H 2 under an inert atmosphere, this result indicates that the Ag 44 /MPC-catalyzed dehydrogenation of NH 3 BH 3 proceeds by a different mechanism from that on other nanoparticles.