Ammonia borane hydrolysis is considered as a potential means of safe and fast method of H production if it is efficiently catalyzed. Here a series of nearly monodispersed alloyed bimetallic nanoparticle catalysts are introduced, optimized among transition metals, and found to be extremely efficient and highly selective with sharp positive synergy between 2/3 Ni and 1/3 Pt embedded inside a zeolitic imidazolate framework (ZIF-8) support. These catalysts are much more efficient for H release than either Ni or Pt analogues alone on this support, and for instance the best catalyst NiPt@ZiF-8 achieves a TOF of 600 mol·mol·min and 2222 mol·mol·min under ambient conditions, which overtakes performances of previous Pt-base catalysts. The presence of NaOH boosts H evolution that becomes 87 times faster than in its absence with NiPt@ZiF-8, whereas NaOH decreases H evolution on the related Pt@ZiF-8 catalyst. The ZIF-8 support appears outstanding and much more efficient than other supports including graphene oxide, active carbon and SBA-15 with these nanoparticles. Mechanistic studies especially involving kinetic isotope effects using DO show that cleavage by oxidative addition of an O-H bond of water onto the catalyst surface is the rate-determining step of this reaction. The remarkable catalyst activity of NiPt@ZiF-8 has been exploited for successful tandem catalytic hydrogenation reactions using ammonia borane as H source. In conclusion the selective and remarkable synergy disclosed here together with the mechanistic results should allow significant progress in catalyst design toward convenient H generation from hydrogen-rich substrates in the close future.

The palladium-catalyzed Suzuki−Miyaura coupling reaction is one of the most versatile and powerful tools for constructing synthetically useful unsymmetrical aryl−aryl bonds. In designing a Pd cluster as a candidate for efficient catalysis and mechanistic investigations, it was envisaged to study a case intermediate between, although very different from, the "classic" Pd(0)L n and Pd nanoparticle families of catalysts. In this work, the cluster [Pd 3 Cl(PPh 2 ) 2 (PPh 3 ) 3 ] + [SbF 6 ] − (abbreviated Pd 3 Cl) was synthesized and fully characterized as a remarkably robust framework that is stable up to 170 °C and fully air-stable. Pd 3 Cl was found to catalyze the Suzuki−Miyaura C−C crosscoupling of a variety of aryl bromides and arylboronic acids under ambient aerobic conditions. The reaction proceeds while keeping the integrity of the cluster framework all along the catalytic cycle via the intermediate Pd 3 Ar, as evidenced by mass spectrometry and quick X-ray absorption fine structure. In the absence of the substrate under the reaction conditions, the Pd 3 OH species was detected by mass spectrometry, which strongly favors the "oxo-Pd" pathway for the transmetalation step involving substitution of the Cl ligand by OH followed by binding of the OH ligand with the arylboronic acid. The kinetics of the Suzuki− Miyaura reaction shows a lack of an induction period, consistent with the lack of cluster dissociation. This study may provide new perspectives for the catalytic mechanisms of C−C cross-coupling reactions catalyzed by metal clusters.

Herein, we report the synthesis and atomic structure of the cluster-assembled [Au60Se2(Ph3P)10(SeR)15](+) material. Five icosahedral Au13 building blocks from a closed gold ring with Au-Se-Au linkages. Interestingly, two Se atoms (without the phenyl tail) locate in the center of the cluster, stabilized by the Se-(Au)5 interactions. The ring-like nanocluster is unprecedented in previous experimental and theoretical studies of gold nanocluster structures. In addition, our optical and electrochemical studies show that the electronic properties of the icosahedral Au13 units still remain unchanged in the penta-twinned Au60 nanocluster, and this new material might be a promising in optical limiting material. This work offers a basis for deep understanding on controlling the cluster-assembled materials for tailoring their functionalities.