Highly Efficient and Robust Platinum Nanocluster Catalyst Mediated by Polyamine Amidine-Decorated Mesoporous Polymer Beads

Platinum nanoclusters (PtNCs) are promising in catalysis due to their large specific surface area and unique physicochemical properties. Here, ultrasmall and uniform PtNCs are facilely synthesized with the mediation of amidine-functionalized polyamines patched on mesoporous poly(divinylbenzene-4-vinylbenzyl chloride) beads. When each ligand patch has 14 amidines, ultrafine PtNCs (with the size as low as 1.1±0.1 nm) are formed as a result of several factors: deprotonated amidines (carbenes) strongly passivate on Pt atoms, amidines act as co-stabilizers along with weak polyamine ligands, and PtNCs are confined to discrete ligand patches. When one ligand patch contains 9.3 amidines, the resulting PtNCs (1.7±0.3 nm) reach the highest turnover frequency of 536 h⁻¹ for the catalytic reduction of 4-nitrophenol in a batch reaction. This catalyst remains rather stable in a continuous flow test as a 4-nitrophenol conversion of over 95 % is still achieved after running consecutively for 10 h.