Ultrafine Pt Nanoclusters Confined in a Calixarene-Based {Ni24} Coordination Cage for High-Efficient Hydrogen Evolution Reaction

To obtain stable and ultrafine Pt nanoclusters, a trigonal prismatic coordination cage with the sulfur atoms on the edges was solvothermally synthesized to confine them. In the structure of {Ni24(TC4A-SO2)6(TDC)12 (H2O)6} (H4TC4A-SO2 = p-tert-butylsulfonylcalix[4]arene; H2TDC = 2,5-thiophenedicarboxylic acid), three Ni4-(TC4A-SO2) SBUs are bridged by three TDC ligands into a triangle and two such triangles are pillared by three pairs of TDC ligands to form a trigonal prism. The cage cavity has 12 sulfur atoms on the surface. Because of the porous structure and strong covalent interaction between metal and sulfur, ultrafine Pt nanoclusters composed of less than ∼18 Pt atoms can be facilely confined in the present trigonal prismatic cage (Pt@CIAC-121). The as-synthesized Pt NCs exhibit higher electrocatalytic activity than commercial Pt/C toward hydrogen evolution reaction.