Customizing a Hyperbranched Ligand Confers Supported Platinum Nanoclusters with Unexpected Catalytic Activity toward the Reduction of 4-Nitrophenol.

We here show that a dendritic molecule combined with ligand merit confers supported platinum nanoclusters (PtNCs) with unprecedented catalytic performance. Branched polyethylenimine (PEI, M n = 2000 D) patched on a porous bead is modified with 2-(diphenylphosphino)benzaldehyde (dppb) before being used to mediate a platinum nanoparticle/nanocluster (Pt 0 ). The catalytic activity of Pt 0 toward the reduction of 4-nitrophenol (4-NP) is evaluated from the parameter of Pt-normalized rate constant ( k c ). Optimization of the dppb level along with transformation of the PEI hydrogens into diol or trimethylammonium groups imparts supported Pt 0 unprecedented activity ( k c = 19.2 L mmol -1 s -1 and turnover frequency (TOF) = 1041 h -1 ). The supported Pt 0 at an extremely low dosage of 0.1 ppm promotes 98% conversion of 4-NP within minutes and is well recyclable. The striking catalytic activity is attributed to the combination of orthogonal ligand properties such as weak ligand nature, catalyst-activating ability, excellent substrate affinity, and effect on PtNC-size mediation of the ligand.