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Subnanocatalysts (SNCs) containing various noble metals (Cu, Ru, Rh, Pd, or Pt) with sizes of approximately 1nmw ere synthesized using dendritic poly(phenylazomethine)s as amacromolecular template.These materials exhibit high catalytic performance during toluene oxidation without the use of harmful solvents or explosive oxidants,r esulting in the formation of valuable organic products,including benzoic acid as the major product. In particular,P t 19 SNC with an arrowp article size distribution exhibits extraordinary catalytic activity,w ith at urnover frequency of 3238 atom À1 h À1 ,whichis1700 times greater than that obtained by commercial Pt/C catalysts.Catalytic oxidation of hydrocarbons is acritically important process that converts raw materials into versatile organic compounds. [1] However, the majority of the practices currently employed in industry suffer from several disadvantages,s uch as the use of oxidants hazardous to the environment, poor selectivity,a nd excessive waste generation. Applying molecular oxygen as the oxidant in conjunction with solvent-free reaction systems has attracted considerable attention as ab enign, inexpensive approach to catalytic oxidations. [2] Fort his reason, many researchers have studied nanometer-sized heterogeneous catalysts.H owever,d ecreasing the size of the catalyst to the subnanometer scale would further reduce the quantities of noble metals required for catalysis.The catalytic properties of subnanocatalysts (SNCs) with sizes of approximately 1nmh ave been investigated because the lattice structure normally found in nanoparticles is collapsed in such materials and they exhibit quantum size effects as ar esult of the amorphous surface areas and the irregular electron distributions. [3] Additionally,n oble metal SNCs are resistant to oxidation even under an oxygen atmosphere.A sane xample,n oble metal SNCs composed of Rh, [4] Pd, [5] Pt, [6] and Au [7] exhibit highly effective and selective catalysis during CO oxidation. Size-specific Pt SNCs were also found to be more active for the dehydrogenation of propane than larger nanocatalysts. [8] However,t he precise synthesis of such particles while controlling the quantity of metallic atoms per particle is remarkably difficult.Thedendrimer-templated method is an effective strategy for the synthesis of size-controlled subnano metal particles in conjunction with low polydispersity. [9] Dendrimers provide internal nanospaces that could be suitable for catalytic conversion in the presence of metal particles. [10] Our group has prepared subnano platinum particles with atomic-level precision using fourth-generation dendritic poly(phenylazomethine) species having atetraphenylmethane core (DPAG4-TPM) or amono(2-pyridyl)-triphenylmethane core (DPAG4-PyTPM). [11] Ap rior electrochemical study found that SNCs containing between 12 and 20 Pt atoms exhibit superior catalytic performance. [12] In other work, multi-metal alloy nanocatalysts containing Au,P t, and Cu atoms showed enhanced catalytic activity during solvent-free aerobic...

Metallpartikel mit Subnanometergröße sind entscheidend an der katalytischen aeroben Toluol‐Oxidation beteiligt. In ihrer Zuschrift auf S. 1014 erzeugen M. Tanabe, K. Yamamoto und Mitarbeiter mithilfe von Dendrimer‐Templaten verschiedene katalytische Edelmetall‐Subnanopartikel festgelegter Größe. Ihr Pt19‐Katalysator ist einem kommerziellen Pt/C‐Katalysator in der Toluol‐Oxidation um den Faktor 1700 überlegen.

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